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6 Working with Chemicals 6.A INTRODUCTION 107 6.B PRUDENT PLANNING 107 6.C GENERAL PROCEDURES FOR WORKING WITH HAZARDOUS CHEMICALS 108 6.C.1 Personal Behavior 108 6.C.2 Minimizing Exposure to Hazardous Chemicals 108 6.C.2.1 Engineering Controls 108 6.C.2.2 Avoiding Eye Injury 108 6.C.2.3 Avoiding Ingestion of Hazardous Chemicals 109 6.C.2.4 Avoiding Inhalation of Hazardous Chemicals 110 6.C.2.5 Avoiding Injection of Hazardous Chemicals 111 6.C.2.6 Minimizing Skin Contact 111 6.C.3 Housekeeping 113 6.C.4 Transport of Chemicals 114 6.C.5 Storage of Chemicals 114 6.C.6 Use and Maintenance of Equipment and Glassware 114 6.C.7 Working with Scaled-Up Reactions 115 6.C.8 Responsibility for Unattended Experiments and Working Alone 116 6.C.9 Chemistry Demonstrations and Magic Shows 116 6.C.10 Responding to Accidents and Emergencies 117 6.C.10.1 General Preparation for Emergencies 117 6.C.10.2 Handling the Accidental Release of Hazardous Substances 117 6.C.10.3 Notification of Personnel in the Area 117 6.C.10.4 Treatment of Injured and Contaminated Personnel 117 6.C.10.5 Spill Containment 120 6.C.10.6 Spill Cleanup 120 6.C.10.7 Handling Leaking Gas Cylinders 120 6.C.10.8 Handling Spills of Elemental Mercury 121 6.C.10.9 Responding to Fires 121 6.D WORKING WITH SUBSTANCES OF HIGH TOXICITY 122 6.D.1 Planning 122 6.D.2 Experiment Protocols Involving Highly Toxic Chemicals 123 6.D.3 Designated Areas 123 6.D.4 Access Control 123 6.D.5 Special Precautions for Minimizing Exposure to Highly Toxic Chemicals 124 6.D.6 Preparing for Accidents with and Spills of Substances of High Toxicity 125 6.D.7 Storage and Waste Disposal 125 6.D.8 Multihazardous Materials 125 105
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106 PRUDENT PRACTICES IN THE LABORATORY 6.E WORKING WITH BIOHAZARDOUS AND RADIOACTIVE MATERIALS 126 6.E.1 Biohazardous Materials 126 6.E.2 Radioactive Materials 127 6.F WORKING WITH FLAMMABLE CHEMICALS 127 6.F.1 Flammable Materials 129 6.F.2 Flammable Liquids 129 6.F.3 Flammable Gases 129 6.F.4 Catalyst Ignition of Flammable Materials 130 6.G WORKING WITH HIGHLY REACTIVE OR EXPLOSIVE CHEMICALS 130 6.G.1 Overview 130 6.G.2 Reactive or Explosive Compounds 131 6.G.2.1 Protective Devices 131 6.G.2.2 Personal Protective Apparel 132 6.G.2.3 Evaluating Potentially Reactive Materials 132 6.G.2.4 Determining Reaction Quantities 132 6.G.2.5 Conducting Reaction Operations 133 6.G.3 Organic Peroxides 133 6.G.3.1 Peroxidizable Compounds 134 6.G.3.2 Peroxide Detection Tests 134 6.G.3.3 Disposal of Peroxides 134 6.G.4 Explosive Gases and Liquefied Gases 135 6.G.5 Hydrogenation Reactions 135 6.G.6 Materials Requiring Special Attention Because of Toxicity, Reactivity, Explosivity, or Chemical Incompatibility 135 6.G.7 Chemical Hazards of Incompatible Chemicals 140 6.H WORKING WITH COMPRESSED GASES 140 6.H.1 Chemical Hazards of Compressed Gases 140 6.H.2 Specific Chemical Hazards of Select Gases 140 6.I WORKING WITH MICROWAVE OVENS 141 6.J WORKING WITH NANOPARTICLES 141 6.J.1 Controls for Research and Development Laboratory Operations That Utilize or Synthesize Nanomaterials 141 6.J.1.1 Nanomaterial Work Planning and Hazard Assessment 142 6.J.1.2 A Graded Approach to Determining Appropriate Nanomaterial Controls 142 6.J.1.3 Engineering Controls for Nanomaterials Research 143
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107 WORKING WITH CHEMICALS 6.A INTRODUCTION • Minimize exposure to chemicals. Do not allow laboratory chemicals to come in contact with skin. Prudent execution of experiments requires not only Use laboratory chemical hoods and other ven- sound judgment and an accurate assessment of the tilation devices to prevent exposure to airborne risks involved in the laboratory, but also the selection of substances whenever possible. appropriate work practices to reduce risk and protect • Do not underestimate hazards or risks. Assume the health and safety of trained laboratory personnel that any mixture of chemicals will be more toxic as well as the public and the environment. Chapter 4 than its most toxic component. Treat all new provides specific guidelines for evaluating the hazards compounds and substances of unknown toxicity and assessing the risks associated with laboratory as toxic substances. Consider how the chemicals chemicals, equipment, and operations. Chapter 5 dem- will be processed and whether changing states or onstrates how to control those risks when managing forms (e.g., fine particles vs. bulk material) will the inventory of chemicals in the laboratory. The use of change the nature of the hazard. the protocols outlined in Chapter 4 in carefully planned • Be prepared for accidents. Before beginning an experiments is the subject of this chapter. experiment, know what specific action to take in This chapter presents general guidelines for labo- the event of accidental release of any hazardous ratory work with hazardous chemicals rather than substance. Post telephone numbers to call in an specific standard operating procedures for individual emergency or accident in a prominent location. substances. Hundreds of thousands of chemicals are Know the location of all safety equipment and encountered in the research conducted in laboratories, the nearest fire alarm and telephone, and know and the specific health hazards associated with most who to notify in the event of an emergency. Be of these compounds are generally not known. Also, prepared to provide basic emergency treatment. laboratory work frequently generates new substances Keep your co-workers informed of your activities that have unknown properties and unknown toxicity. so they can respond appropriately. Consequently, the only prudent course is for laboratory personnel to conduct their work under conditions that Virtually every laboratory experiment generates minimize the risks from both known and unknown some waste, which may include such items as used hazardous substances. The general work practices disposable labware, filter media and similar materi- outlined in this chapter are designed to achieve this als, aqueous solutions, and hazardous chemicals. (For purpose. more information about disposal of chemical waste, Specifically, section 6.C provides guidelines that are see Chapter 8.) the standard operating procedures where hazardous chemicals are stored or are in use. In section 6.D, ad- ditional special procedures for work with highly toxic 6.B PRUDENT PLANNING substances are presented. How to determine when Before beginning any laboratory work, determine these additional procedures are necessary is discussed the hazards and risks associated with the experiment in detail in Chapter 4, section 4.C. Section 6.E gives de- or activity and implement the necessary safety pre- tailed special procedures for work with substances that cautions. Ask yourself a hypothetical question before pose risks due to biohazards and radioactivity, section starting work: “What would happen if . . . ?” Consider 6.F addresses flammability, and section 6.G, reactivity the possible contingencies and make preparations to and explosivity. Special considerations for work with take appropriate emergency actions. For example, compressed gases are the subject of section 6.H. Section what would be the consequences of a loss of electri- 6.I covers microwave ovens, and section 6.J describes cal power or water pressure? Within each laboratory, working with nanoparticles. all personnel should know the location of emergency Chapter 7 provides precautionary methods for equipment and how to use it, be familiar with emer- handling laboratory equipment commonly used in gency procedures, and know how to obtain help in an conjunction with hazardous chemicals. Chapters 4, emergency. Laboratories should have a standing op- 6, and 7 should all be consulted before working with erational plan that describes how reactions, chemicals, hazardous chemicals. and other laboratory processes will be handled in the Four fundamental principles underlie all the work case of a natural disaster or in the event that the indi- practices discussed in this chapter. Consideration of vidual responsible for laboratory activities is unavail- each should be encouraged before beginning work as able indefinitely (i.e., in the case of illness or death). part of the culture of safety within the laboratory. Included in the plan should be emergency procedures and actions to be taken in the event that laboratory • Plan ahead. Determine the potential hazards as- personnel experience a sudden medical emergency sociated with an experiment before beginning. while performing an experiment.
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108 PRUDENT PRACTICES IN THE LABORATORY Pay attention to the potential safety implications 1. substitution of less hazardous materials or pro- of subtle changes to experimental procedures. Slight cesses (see Chapter 5, section 5.B, Green Chemistry changes to commonly performed operations often for Every Laboratory), present unrecognized hazards. Changing solvents, 2. engineering controls (Chapter 9), suppliers, reagent concentration, reaction scale, and 3. administrative controls (Chapter 2), and materials of construction may bring unintended 4. personal protective equipment (PPE) consequences. Determine the physical and health hazards associ- See also the Occupational Safety and Health Admin- ated with chemicals before working with them. This istration’s (OSHA) Safety and Health Management determination may involve consulting literature refer- eTool, Hazard Prevention and Control module avail- ences, laboratory chemical safety summaries (LCSSs), able at www.osha.gov. Before beginning work, review material safety data sheets (MSDSs), or other reference all proposed laboratory procedures thoroughly to materials (see also Chapter 4, section 4.B) and may determine potential health and safety hazards. Refer require discussions with the laboratory supervisor, to the MSDS for guidance on exposure limits, health safety personnel, and industrial hygienists. Check hazards and routes of entry into the body, and chemical every step of the waste minimization and removal pro- storage, handling, and disposal. Avoid underestimat- cesses against federal, state, and local regulations. Be- ing risk when handling hazardous materials. fore producing mixed chemical-radioactive-biological waste (see Chapter 8, section 8.C.1.3) consult your 6.C.2.1 Engineering Controls institution’s or firm’s environmental health and safety (EHS) personnel. Engineering controls are measures that eliminate, Many of the general practices applicable to working isolate, or reduce exposure to chemical or physical with hazardous chemicals are given elsewhere in this hazards through the use of various devices. Examples volume (see Chapter 2). (See Chapter 5, section 5.F for include laboratory chemical hoods and other ventila- detailed instructions on the transport of chemicals and tion systems, shields, barricades, and interlocks. En- section 5.E on storage; Chapter 7 for information on gineering controls must always be considered as the use and maintenance of equipment and glassware; and first and primary line of defense to protect personnel Chapter 8 for information on disposal of chemicals.) and property. When possible, PPE is not to be used as a first line of protection. For instance, a personal respira- tor should not be used to prevent inhalation of vapors 6.C GENERAL PROCEDURES when a laboratory chemical hood (formerly called FOR WORKING WITH fume hoods) is available. (See Box 6.1 and Chapter HAZARDOUS CHEMICALS 9 for more information about laboratory design and ventilation.) 6.C.1 Personal Behavior Demonstrating prudent behavior within the labora- 6.C.2.2 Avoiding Eye Injury tory is a critical part of a culture of safety. This includes following basic safety rules and policies (see Chapter Eye protection is required for all personnel and 2, section 2.C.1), being cognizant of the hazards within visitors in all locations where laboratory chemicals are the laboratory (see Chapter 4), and exhibiting profes- stored or used, whether or not one is actually perform- sionalism with co-workers. Maintaining an awareness ing a chemical operation. Visitor eye protection should of the work being performed in nearby hoods and on be made available at the entrances to all laboratories. neighboring benches and any risks posed by that work Researchers should assess the risks associated with is also important. an experiment and use the appropriate level of eye protection: 6.C.2 Minimizing Exposure to Hazardous • Safety glasses with side shields provide the mini- Chemicals mum protection acceptable for regular use. They Take precautions to avoid exposure by the principal must meet the American National Standards Insti- routes, that is, contact with skin and eyes, inhalation, tute (ANSI) Z87.1-2003 Standard for Occupational and ingestion (see Chapter 4, section 4.C, for a detailed and Educational Eye and Face Protection, which discussion). specifies minimum lens thickness and impact The preferred methods for reducing chemical expo- resistance requirements. sure are, in order of preference, • Chemical splash goggles are more appropriate
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109 WORKING WITH CHEMICALS goggles when conducting particularly hazard- ous laboratory operations (e.g., working with BOX 6.1 glassware under vacuum or handling potentially A Simple Qualitative Method explosive compounds). In addition, glassblowing to Verify Adequate Laboratory and the use of laser or ultraviolet light sources Chemical Hood Ventilation require special glasses or goggles. Materials • Operations at risk of explosion or that present the 200 g (approximately 250 mL) of dry ice pellets (5- possibility of projectiles must have engineering to 10-mm diam) controls as a first line of protection. For instance, Shallow bowl, approximately 3-L volume in addition to chemical splash goggles or full- 1 L water at 43 ºC (mix hot and cold water as face shields, these operations must be conducted needed to obtain the target temperature) behind blast shields, in rubber-coated or taped Thermometer glassware. Procedure Ordinary prescription glasses do not provide ad- 1. pen the chemical fume hood sash to simulate O equate protection against injury because they lack side actual operation. Position laboratory equipment shields and are not resistant to impact, but prescrip- as close as possible to where it will be used. tion safety glasses and chemical splash goggles are 2. lace the shallow bowl approximately 15 cm into P available. the chemical fume hood and in the center of the Similarly, contact lenses offer no protection against sash opening. eye injury and do not substitute for safety glasses and 3. dd 1 L of the warm water to the bowl. A chemical splash goggles. They should not be worn 4. dd the dry ice pellets to the water. A where chemical vapors are present or a chemical splash 5. fter approximately 5 s, observe the vapor flowing A or chemical dust is possible because contact lenses can from the bowl. be damaged under these conditions. If, however, an 6. epeat the observation while a colleague walks R individual chooses to wear contact lenses in the labo- past or moves around the chemical fume hood to ratory, chemical splash goggles must be worn. Note simulate actual operation. that there has been a change in recommended guid- 7. f vapors are observed escaping the chemical fume I ance regarding the wearing of contact lenses since the hood face, the result is a fail; none escaping is a previous edition. Many organizations, including the pass. National Institute for Occupational Safety and Health (NIOSH) (HHS/CDC/NIOSH, 2005) and the American In the event of a failure or if there is any concern about Chemical Society (Ramsey and Breazeale, 1998) have proper operation, contact appropriate personnel and removed most restrictions on wearing contact lenses take corrective action. Adjustment of the sash open- in the laboratory. ing and the baffles and relocation of equipment in the chemical fume hood should be considered. 6.C.2.3 Avoiding Ingestion of Hazardous Chemicals NOTE: In addition, airflow should be measured on an annual basis. Eating, drinking, smoking, gum chewing, applying cosmetics, and taking medicine in laboratories where hazardous chemicals are used or stored should be strictly prohibited. Food, beverages, cups, and other than regular safety glasses to protect against haz- drinking and eating utensils should not be stored in ar- ards such as projectiles, as well as when working eas where hazardous chemicals are handled or stored. with glassware under reduced or elevated pres- Glassware used for laboratory operations should never sures (e.g., sealed tube reactions), when handling be used to prepare or consume food or beverages. potentially explosive compounds (particularly Laboratory refrigerators, ice chests, cold rooms, and during distillations), and when using glassware ovens should not be used for food storage or prepara- in high-temperature operations. tion. Laboratory water sources and deionized labora- • Chemical splash goggles or face shields should be tory water should not be used as drinking water. Never worn when there is a risk of splashing hazardous wear gloves or laboratory coats outside the laboratory materials or flying particles. or into areas where food is stored and consumed, and • Because chemical splash goggles offer little pro- always wash laboratory apparel separately from per- tection to the face and neck, full-face shields sonal clothing. should be worn in addition to safety glasses or
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110 PRUDENT PRACTICES IN THE LABORATORY Laboratory chemicals should never be tasted. A face velocity and proper operation. They should pipet bulb, aspirator, or mechanical device must be be inspected regularly and the inspection certifica- used to pipet chemicals or to start a siphon. To avoid tion displayed in a visible location. accidental ingestion of hazardous chemicals, pipetting • Review the MSDS and the manufacturer’s label should never be done by mouth. Hands should be before using a chemical in the laboratory or hood. washed with soap and water immediately after work- Observe the permissible exposure limit, threshold ing with any laboratory chemicals, even if gloves have limit value, the primary routes of exposure, and been worn. any special handling procedures described within the document. Confirm that the experimental methods and available engineering controls are 6.C.2.4 Avoiding Inhalation of Hazardous capable of controlling personnel exposure to the Chemicals hazardous chemicals being used. Only in certain controlled situations should any • Keep reactions and hazardous chemicals at least laboratory chemical be sniffed.1 In general, the prac- 6 in. (15 cm) behind the plane of the sash, farther tice is not encouraged. Toxic chemicals or compounds if possible. of unknown toxicity should never be deliberately • Never put your head inside an operating hood to sniffed. Conduct all procedures involving volatile toxic check an experiment. The plane of the sash is the substances and operations involving solid or liquid barrier between contaminated and uncontami- toxic substances that may result in the generation of nated air. aerosols in a laboratory chemical hood. Air-purifying • On hoods where sashes open vertically, work respirators are required for use with some chemicals with the sash in the lowest possible position. Where if engineering controls cannot control exposure. Sig- sashes open horizontally, position one of the doors nificant training, along with a medical evaluation and to act as a shield in the event of an accident. When respirator fit, are necessary for the use of respirators. the hood is not in use, the sash should be kept at For further guidance on the use of respirators with the recommended position to maintain laboratory specific chemicals refer to Chapter 7, section 7.F.2.4 of airflow. this book, the OSHA Respiratory Protection Standard • Keep laboratory chemical hoods clean and clear; (29 CFR § 1910.134), and ANSI Standard Z88.2-1992. do not clutter with bottles or equipment. If there is Laboratory chemical hoods should not be used for a grill along the bottom slot or a baffle in the back, disposal of hazardous volatile materials by evapora- clean it regularly so it does not become clogged tion. Such materials should be treated as chemical with papers and dirt. Allow only materials ac- waste and disposed of in appropriate containers ac- tively in use to remain in the hood. Following this cording to institutional procedures and government rule provides optimal containment and reduces regulations. (See Chapter 8 for information on waste the risk of extraneous chemicals being involved handling.) in any fire or explosion. Support any equipment in hoods on racks or feet to provide airflow under 6.C.2.4.1 eneral Rules for Laboratory Chemical G the equipment. Hoods • Do not remove the airfoil, alter the position of Detailed information regarding laboratory ventila- inner baffles, block exterior grills, or make any tion can be found in Chapter 9. The information here other modifications without the approval of the is intended to provide a brief overview. These general appropriate staff. rules should be followed when using laboratory chemi- • Report suspected laboratory chemical hood mal- cal hoods: functions promptly to the appropriate office, and confirm that the problems are corrected. • Before using a laboratory chemical hood, learn • If working in a glovebox, check the seals and pres- how it operates. They vary in design and operation. sures on the box before use. • For work involving hazardous substances, use only hoods that have been evaluated for adequate Post the name of the individual responsible for the hood in a visible location. Clean hoods before mainte- nance personnel work on them. 1In a controlled instructional setting, students may be told to sniff (See Chapter 9, section 9.C, for more information on the contents of a container. In such cases, the chemical being sniffed should be screened ahead of time to ensure that it is safe to do so. If laboratory chemical hoods.) instructed to sniff a chemical, gently waft the vapors toward your nose using a folded sheet of paper. Do not directly inhale the vapors.
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111 WORKING WITH CHEMICALS may require the combined use of a chemical-resistant 6.C.2.5 Avoiding Injection of Hazardous (butyl, viton, or neoprene) glove and a cut-resistant Chemicals (e.g., leather, Kevlar®) glove. Reusable gloves should Solutions of chemicals are often transferred in sy- be washed and inspected before and after each use. ringes, which for many uses are fitted with sharp nee- Be sure to wash your hands after wearing gloves and dles. The risk of inadvertent injection is significant, and handling laboratory chemicals, to remove any skin vigilance is required to avoid an injury. Use special care contamination that might have occurred. when handling solutions of chemicals in syringes with Gloves that might be contaminated with toxic ma- needles. When accompanied by a cap, syringe needles terials should not be removed from the immediate should be placed onto syringes with the cap in place area (usually a laboratory chemical hood) in which and remain capped until use. Do not recap needles, the chemicals are located. To prevent contamination of especially when they have been in contact with chemi- common surfaces that others might touch bare-handed, cals. Remove the needle and discard it immediately never wear gloves when handling common items such after use in the appropriate sharps containers. Blunt-tip as doorknobs, handles, or switches on shared equip- needles, including low-cost disposable types, are avail- ment, or outside the laboratory. Along the same lines, able from a number of commercial sources and should consider, before touching a surface while wearing be used unless a sharp needle is specifically required gloves, whether it would be common for people to to puncture rubber septa or for subcutaneous injection. touch the surface with or without gloves and use ap- propriate precautions. For example, controls for hood nitrogen or water may be located outside the hood 6.C.2.6 Minimizing Skin Contact itself but may well be contaminated. 6.C.2.6.1 loves G When working with chemicals in the laboratory, wear The OSHA Personal Protective Equipment (PPE) gloves of a material known to be resistant to perme- Standard (29 CFR §§ 1910.132–1910.138) requires ation by the substances in use. Glove selection guides completion of a hazards assessment for each work area, for a wide array of chemicals are available from most including an evaluation of the hazards involved and glove manufacturers and vendors. In general, nitrile selection of appropriate hand protection. Wear gloves gloves are suitable for incidental contact with chemi- whenever handling hazardous chemicals, sharp-edged cals. Both nitrile and latex gloves provide minimum objects, very hot or very cold materials, toxic chemicals, protection from chlorinated solvents and should not and substances of unknown toxicity. No single glove be used with oxidizing or corrosive acids. Latex gloves material provides effective protection for all uses. protect against biological hazards but offer poor protec- Before starting, carefully evaluate the type of protec- tion against acids, bases, and most organic solvents. In tion required in order to select the appropriate glove. addition, latex is considered a sensitizer and triggers The discussion presented here is geared toward gloves allergic reactions in some individuals. (For more infor- that protect against chemical exposure. (For informa- mation, see section 6.C.126.96.36.199.) Neoprene and rubber tion about gloves that protect against other types of gloves with increased thickness are suggested for use hazards, see Chapter 7, section 7.F.1.4.) with most caustic and acidic materials. Barrier creams Select gloves carefully to ensure that they are im- and lotions can provide some skin protection but are pervious to the chemicals being used and are of cor- never a substitute for gloves, protective clothing, or rect thickness to allow reasonable dexterity while also other protective equipment. Use these creams only to ensuring adequate barrier protection. Choosing an im- supplement the protection offered by PPE. proper glove can itself be a serious hazard in handling According to the National Ag Safety Database (www. hazardous chemicals. If chemicals do penetrate glove nasdonline.org), a program supported by NIOSH and material, they could be held in prolonged contact with the Centers for Disease Control and Prevention, materi- the hand and cause more serious damage than in the als that are used in the manufacture of gloves designed absence of a proper glove. The degradation and per- to provide chemical resistance include the following: meation characteristics of the selected glove material must be appropriate for protection from the hazardous • Butyl is a synthetic rubber with good resistance chemicals that are handled. Double gloves provide a to weathering and a wide variety of chemicals. multiple line of defense and are appropriate for many • Natural rubber latex is a highly flexible and con- situations. Find a glove or combination of gloves that forming material made from a liquid tapped from addresses all the hazards present. For example, opera- rubber plants. It is a known allergen. (See section tions involving a chemical hazard and sharp objects 6.C.188.8.131.52 for more information.)
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112 PRUDENT PRACTICES IN THE LABORATORY • Neoprene is a synthetic rubber having chemical dispose of contaminated gloves according to insti- and wear-resistance properties superior to those tutional procedures. of natural rubber. • D econtaminate or wash gloves appropriately • Nitrile is a copolymer available in a wide range of before removing them. [Note: Some gloves, e.g., acrylonitrile content; chemical resistance and stiff- leather and poly(vinyl alcohol), are water per- ness increase with higher acrylonitrile content. meable. Unless coated with a protective layer, • Polyethylene is a fairly chemical-resistant mate- poly(vinyl alcohol) gloves will degrade in the rial used as a freestanding film or a fabric coating. presence of water.] • Poly(vinyl alcohol) is a water-soluble polymer • Do not wear gloves outside the laboratory, to that exhibits exceptional resistance to many avoid contamination of surfaces used by unpro- organic solvents that rapidly permeate most tected individuals. rubbers. • Gloves on a glovebox should be inspected with • Poly(vinyl chloride) is a stiff polymer that is made the same care as any other gloves used in the softer and more suitable for protective clothing laboratory. Disposable gloves appropriate for applications by the addition of plasticizers. the materials being handled within the glovebox • Polyurethane is an abrasion-resistant rubber that should be used in addition to the gloves attached is either coated into fabrics or formed into gloves to the box. Protect glovebox gloves by removing or boots. all jewelry prior to use. • 4H® or Silvershield® is a registered trademark 6.C.184.108.40.206 atex Gloves L of North Hand Protection; it is highly chemical- resistant to many different class of chemicals. Although natural rubber latex gloves can be used • Viton®, a registered trademark of DuPont, is a as protective equipment to prevent transmission of highly chemical-resistant but expensive synthetic infectious diseases and for skin protection against con- elastomer. tact with some chemicals, they can also cause allergic reactions. In addition to causing skin contact allergic When choosing an appropriate glove, consider the reactions to individuals wearing the gloves, they can required thickness and length of the gloves as well also cause allergic reactions through inhalation of latex as the material. Consult the glove manufacturer for proteins that may be released into the air when the chemical-specific glove recommendations and in- powders used to lubricate the interior of the glove are formation about degradation and permeation times. dispersed as gloves are removed. Thus the risk of ex- Certain disposable gloves should not be reused. (For posure via inhalation presents a risk both to the wearer more information, see OSHA PPE Standard, 29 CFR § of latex gloves and to sensitized individuals who may 1910.138, regarding hand protection.) be working nearby. The following general guidelines apply to the selec- Latex exposure symptoms include skin rash, respira- tion and use of protective gloves: tory irritation, asthma, and, in rare cases, anaphylactic shock. The amount of exposure needed to sensitize an • Do not use a glove beyond its expiration date. individual to natural rubber latex is not known, but Gloves degrade over time, even in an unopened when exposures are reduced, sensitization decreases. box. Individuals with known latex allergies should never • When not in use, store gloves in the laboratory but wear latex gloves and may not be able to work in areas not close to volatile materials. To prevent chemical where latex gloves are used. Persons with known latex contamination of nonlaboratory areas by people allergies should follow their organization’s procedures coming to retrieve them, gloves must not be stored to ensure that they are not exposed. in offices or in break rooms or lunchrooms. To help minimize the risk of exposure to latex al- • Inspect gloves for small holes, tears, and signs of lergens, NIOSH issued an alert, Preventing Allergic degradation before use. Reactions to Latex in the Workplace (HHS/CDC/NIOSH, • Replace gloves periodically because they degrade 1997). NIOSH recommends the following to reduce with use, depending on the frequency of use and exposure to latex: their permeation and degradation characteristics relative to the substances handled. • W henever possible, substitute another glove • Replace gloves immediately if they become con- material. taminated or torn. • If latex gloves are the best choice, use reduced- • Replace gloves periodically, depending on the protein, powder-free gloves. frequency of use. Regular inspection of their ser- • Wash hands with mild soap and water after re- viceability is important. If they cannot be cleaned, moving latex gloves.
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113 WORKING WITH CHEMICALS 6.C.3 Housekeeping 6.C.2.6.2 lothing and Protective Apparel C Protective clothing should be used when there A definite correlation exists between orderliness and is significant potential for skin-contact exposure to the level of safety in the laboratory. In addition, a dis- chemicals. Protective clothing does not offer complete orderly laboratory can hinder or endanger emergency protection to the wearer and should not be used as response personnel. The following housekeeping rules a substitute for engineering controls. The protective should be adhered to: characteristics of any protective clothing must be matched to the hazard. As with gloves, no single mate- • Never obstruct access to exits and emergency rial that provides protection to all hazards is available. equipment such as fire extinguishers and safety When multiple hazards are present, multiple layers showers. Comply with local fire codes for emer- of protective clothing may be required. Some types of gency exits, electrical panels, and minimum aisle PPE, such as aprons of reduced permeability and dis- width. posable laboratory coats, offer additional safeguards • Store coats, bags, and other personal items in the when working with toxic materials. (See also Chapter proper area, not on the benchtops or in the aisles. 7, section 7.F.1.1.) • Do not use floors, stairways, and hallways as stor- Commercial lab coats are fabricated from a variety age areas. Items stored in these areas can become of materials, such as cotton, polyester, cotton-polyester hazards in the event of an emergency. blends, polyolefin, and polyaramid. Selection of the • Keep drawers and cabinets closed when not in proper material to deal with the particular hazards use, to avoid accidents. present is critical. For example, although cotton is a • Properly label (see Chapter 4, section 4.B.5) in per- good material for laboratory coats, it reacts rapidly manent marker and store (see Chapter 5, section with acids. Plastic or rubber aprons can provide good 5.E) all chemicals appropriately by compatibility. protection from corrosive liquids but can be inap- • Label transfer vessels2 with the full chemical propriate in the event of a fire. Because plastic aprons name, manufacturer’s name, hazard class, and can also accumulate static electricity, they should not any other special warnings. be used around flammable solvents, explosives sensi- • Store chemical containers in order and neatly. tive to electrostatic discharge, or materials that can be Face labels outward for easy viewing. Contain- ignited by static discharge. Because many synthetic ers themselves should be clean and free of dust. fabrics are flammable and can adhere to the skin, they Containers and labels that have begun to degrade increase the severity of a burn and should not be worn should be replaced, repackaged, or disposed of if working with flammable materials or an open flame. in the proper location. Do not store materials or When working with flammable materials or pyrophor- chemicals on the floor because these may present ics, use laboratory coats made from flame-resistant, trip and spill hazards. nonpermeable materials (polyaramids). Disposable • Keep chemical containers closed when not in use. garments may be a good option if handling carcino- • Secure all compressed gas cylinders to walls or genic or other highly hazardous materials. However, benches in accordance with the guidance pro- these provide only limited protection from vapor or gas vided in Chapter 5, section 5.E.6. penetration. Take care to remove disposable garments • Secure all water, gas, air, and electrical connec- without exposing any individual to toxic materials and tions in a safe manner. dispose of as hazardous waste. • Return all equipment and laboratory chemicals to To prevent chemical exposure from spilled materi- their designated storage location at the end of als in the laboratory, wear shoes that cover the entire the day. foot. Perforated shoes, open-toe and open-heel shoes, • To reduce the chance of accidentally knocking sandals, or clogs should not be permitted. Shoes should containers to the floor, keep bottles, beakers, have stable soles that provide traction in slippery or flasks, and the like at least 2 in. from the edge of wet environments to reduce the chance of falling. benchtops. Socks should cover the ankles so as to protect against • Keep work areas clean (including floors) and un- chemical splashes. High heels should not be worn in cluttered. Wipe up all liquid and ice on the floor the laboratory. promptly. Accumulated dust, chromatography Once they have been used, laboratory coats and adsorbents, and other chemicals pose respira- other protective apparel may become contaminated. Therefore, they must be stored in the laboratory and 2Transfer vessels may also be known as “secondary containers.” not in offices or common areas. Institutions should pro- The term “transfer vessel” is used here to avoid confusion with sec- vide a commercial laundry service for laboratory coats ondary containment, which is a tray, bucket, or other container used and uniforms; they should not be laundered at home. to control spills from a primary container in the event of breakage.
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114 PRUDENT PRACTICES IN THE LABORATORY tory hazards. To avoid formation of aerosols, dry as peroxide formers), write the date the container was sweeping should not be used in the laboratory. opened on the label. For peroxide formers, write the Remove broken glass, spilled chemicals, and pa- test history and date of discard on the label as well. per litter from benchtops and laboratory chemical Keep only small quantities (<1 L) of flammable hoods. liquids at workbenches. Larger quantities should be • To avoid flooding, do not block the sink drains. stored in approved storage cabinets. Store large con- Place rubber matting in the bottom of the sinks tainers (>1 L) below eye level on low shelves. Unless to prevent breakage of glassware and to avoid additional protection and secondary containment are injuries. provided, never store hazardous chemicals and waste • Do not pile up dirty glassware in the laboratory. on the floor. Be aware that fire codes dictate the total Wash glassware carefully. Remember that dirty volume of flammable liquids, liquefied gases, and water can mask glassware fragments. Handle flammable compressed gases in a given work area. Ask and store laboratory glassware with care. Discard your institution’s EHS expert for the fire code’s maxi- cracked or chipped glassware promptly. mum flammable liquid and gas load for your labora- • Dispose of all waste chemicals properly and in tory, and ensure that your laboratory is in compliance accordance with organizational policies. with this code. • Dispose of broken glass and in a specially labeled Refrigerators used for storage of significant quanti- container for broken glass. Treat broken glassware ties of flammable chemicals must be explosion-proof contaminated with a hazardous substance as a laboratory-safe units. Explosion-proof refrigerators hazardous substance. are sold for this purpose and are labeled and hard- • Dispose of sharps (e.g., needles and razor blades) wire installed. Such a refrigerator is mandatory for a in a specially labeled container for sharps. Treat renovated or new laboratory where flammable mate- sharps contaminated with a hazardous substance rials need refrigeration. Because of the expense of an as hazardous substances. explosion-proof refrigerator, a modified sparkproof re- frigerator is sometimes found in older laboratories and Formal housekeeping and laboratory inspections laboratories using very small amounts of flammable should be conducted on a regular basis by the Chemical materials. However, a modified sparkproof refrigera- Hygiene Officer or a designee. tor cannot meet the standards of an explosion-proof refrigerator. Where they exist, a plan to phase out the sparkproof refrigerator is recommended. 6.C.4 Transport of Chemicals Materials placed in refrigerators should be clearly For more detailed information about transfer and labeled with water-resistant labels. Storage trays or transport of chemicals, see Chapter 5, section 5.F. secondary containment should be used to minimize the When transporting chemicals outside the labora- distribution of material in the event a container should tory or between stockrooms and laboratories, use only leak or break. Retaining the shipping can for secondary break-resistant secondary containment. Commercially containment is good practice. Regularly inspect storage available secondary containment is made of rubber, trays, shipping cans, and secondary containment for metal, or plastic, with carrying handle(s), and is large primary container leaks and degradation. Laboratory enough to hold the contents of the chemical containers refrigerators should have permanent labels warning in the event of breakage. Resealable plastic bags serve against the storage of food and beverages for human as adequate secondary containment for small samples. consumption. When transporting cylinders of compressed gases, All chemicals should be stored with attention to the cylinder must always be strapped in a cylinder cart incompatibilities so that if containers break in an acci- and the valve protected with a cover cap. When cylin- dent, reactive materials do not mix and react violently. ders must be transported between floors, passengers (See Chapter 5, section 5.E, and Chapter 8, section should not be in the elevator. 8.C.1.2, for more information.) 6.C.5 Storage of Chemicals 6.C.6 Use and Maintenance of Equipment and Glassware Avoid the accumulation of excess chemicals by acquiring the minimum quantities necessary for each Good equipment maintenance is essential for safe procedure or research project. Properly label all chemi- and efficient operations. Laboratory equipment should cal containers. Indicate any special hazards on the be regularly inspected, maintained, and serviced on label. For certain classes of compounds (e.g., ethers schedules that are based on the manufacturer’s recom-
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115 WORKING WITH CHEMICALS mendations, as well as the likelihood and hazards of VIGNETTE 6.2 equipment failure. Maintenance plans should ensure Runaway reaction that any lockout procedures cannot be violated. during scale-up Carefully handle and store glassware to avoid dam- age. Discard or repair chipped or cracked items. Handle A researcher scaled up the cycloaddition reac- vacuum-jacketed glassware with extreme care to pre- tion of maleic anhydride with quadricyclane, a vent implosions. Evacuated equipment such as Dewar strained high-energy hydrocarbon. This reaction flasks or vacuum desiccators should be taped, shielded, is reported in the literature and was also previ- or coated. Only glassware designed for vacuum work ously performed in the researcher’s laboratory should be used for that purpose. without incident, albeit at small scale (<10 g). No Use tongs, a tweezer, or puncture-proof hand protec- solvent is used in the procedure. The researcher tion when picking up broken glass. Small pieces should combined the reagents (approximately 250 g to- be swept up with a brush into a dustpan. Glassblowing tal, a 20-fold scale-up) and began heating to the operations should not be attempted unless an area has 60–70 °C target temperature. On reaching 50–60 been made safe for both fabrication and annealing. °C the internal temperature rose very rapidly to Protect your hands and body when performing forceful more than 220 °C. The subsequent rapid boiling operations involving glassware. For instance, leather of the reagents dislodged the reflux condenser or Kevlar® gloves should be used when placing rubber and expelled some liquid and solid into the tubing on glass hose connections. Cuts from forcing chemical fume hood. There was no fire. The ma- glass tubing into stoppers or plastic tubing are a com- terials were fully contained within the chemical mon laboratory accident and are often serious. (See fume hood, with no injuries, personnel exposure, Vignette 6.1.) Constructing adaptors from glass tubing or equipment damage. and rubber or cork stoppers is obsolete; instead, use The likelihood of runaway exothermic reac- fabricated, commercial adaptors made from plastic, tions must be considered whenever conducting metal, or other materials. a reaction on a larger scale than previous experi- (See Chapter 7 for more discussion.) ence. In the present example this possibility was increased by the use of ultrapure reagents and the 6.C.7 Working with Scaled-Up Reactions lack of solvent. When using high-energy reagents, it is preferable to run them as dilute as possible Special care and planning is necessary to ensure safe in a solvent. This practice significantly lowers the scaled-up work. Scale-up of reactions from those pro- energy density and significantly adds to the ther- ducing a few milligrams or grams to those producing mal mass, which help to decrease the chance of a more than 100 g of a product may magnify risks by runaway reaction. Slow addition of one reagent several orders. Although the procedures and controls also limits the effects of an exothermic reaction. for large-scale laboratory reactions may be the same as those for smaller-scale procedures, significant differ- ences may exist in heat transfer, stirring effects, times for dissolution, and the effects of concentration—all of which need to be considered. (See Vignette 6.2.) When planning large-scale work, practice requires consulting with experienced workers and considering all possible VIGNETTE 6.1 risks. Finger laceration from Although one cannot always predict whether a broken tubing connector scaled-up reaction has increased risk, hazards should be evaluated if the following conditions exist: A technician planned to replace the rubber vacuum tubing leading from a vacuum pump to • The starting material and intermediates contain a glass cold trap. While attempting to remove the functional groups that have a history of being old rubber tubing from the trap, the glass nipple explosive (e.g., N—N, N—O, N—halogen, O—O, broke and the broken glass cut the employee’s and O—halogen bonds) or that could explode to thumb. The technician did not don protective give a large increase in pressure. gloves or attempt to precut the rubber tubing • A reactant or product is unstable near the reac- to ease removal. The employee received three tion or workup temperature. A preliminary test sutures. to determine the temperature and mode of de-
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136 PRUDENT PRACTICES IN THE LABORATORY to fires and explosions. These compounds should be mother liquor. Peroxide concentrations from autoxida- stored and handled under an inert atmosphere in areas tion may form saturated solutions that then crystallize that are free from ignition sources. Detailed informa- the peroxide as it is being formed. There are numerous tion about handling of organolithium compounds is reports of old bottles of diisopropyl ether being found provided by Schwindeman et al. (2002). with large masses of crystals settled at the bottom of Aluminum chloride (AlCl3) should be considered a the bottle. These crystals are extremely shock sensitive, potentially dangerous material. If moisture is present, even while wetted with the diisopropyl ether super- sufficient decomposition may form hydrogen chloride natant. Mild shock (e.g., bottle breakage, removing (HCl) and build up considerable pressure. If a bottle the bottle cap) is sufficient to result in explosion. This is to be opened after long storage, it should first be ether should not be stored in the laboratory. Only the completely enclosed in a heavy towel. amount required for a particular experiment or process Ammonia and amines. Ammonia (NH3) reacts with should be purchased; any leftover material should be iodine to give nitrogen triiodide, which explodes on disposed of immediately. touch. Ammonia reacts with hypochlorites (bleach) Dimethyl sulfoxide (DMSO), (CH3)2SO, decom- to give chlorine. Mixtures of ammonia and organic poses violently on contact with a wide variety of active halides sometimes react violently when heated under halogen compounds, such as acyl chlorides. Explosions pressure. Ammonia is combustible. Inhalation of con- from contact with active metal hydrides have been centrated fumes can be fatal. Ammonia and amines reported. DMSO does penetrate and carry dissolved can react with heavy metal salts to produce explosive substances through the skin membrane. fulminates. Dry benzoyl peroxide (C6H5CO2)2 is easily ignited Azides, both organic and inorganic, and some azo and sensitive to shock. It decomposes spontaneously compounds can be heat and shock sensitive. Azides at temperatures greater than 50 °C. It is reported to be such as sodium azide can displace halide from chlori- desensitized by addition of 20% water. nated hydrocarbons such as dichloromethane to form Dry ice should not be kept in a container that is not highly explosive organic polyazides; this substitution designed to withstand pressure. Containers of other reaction is facilitated in solvents such as dimethyl substances stored over dry ice for extended periods sulfoxide. generally absorb carbon dioxide (CO2) unless they Boron halides are powerful Lewis acids and hydro- have been carefully sealed. When such containers are lyze to strong protonic acids. removed from storage and allowed to come rapidly Carbon disulfide (CS2) is both very toxic and very to room temperature, the CO2 may develop sufficient flammable; mixed with air, its vapors can be ignited by pressure to burst the container with explosive violence. a steam bath or pipe, a hot plate, or a lightbulb. On removal of such containers from storage, the stop- Chlorine (C12) is highly toxic and may react vio- per should be loosened or the container itself should lently with hydrogen (H2) or with hydrocarbons when be wrapped in towels and kept behind a shield. Dry ice exposed to sunlight. can produce serious burns, as is also true for all types Diazomethane (CH2N2) and related diazo com- of dry-ice cooling baths. Drying agents, such as Ascarite® (sodium hydrox- pounds should be treated with extreme caution. They are very toxic, and the pure gases and liquids explode ide–coated silica), should not be mixed with phospho- readily even from contact with sharp edges of glass. rus pentoxide (P2O5) because the mixture may explode Solutions in ether are safer from this standpoint. An if it is warmed with a trace of water. Because the cobalt ether solution of diazomethane is rendered harmless salts used as moisture indicators in some drying agents by dropwise addition of acetic acid. may be extracted by some organic solvents, the use Diethyl and other ethers, including tetrahydrofuran of these drying agents should be restricted to drying and 1,4-dioxane and particularly the branched-chain gases. type of ethers, may contain peroxides that have de- Dusts that are suspensions of oxidizable particles veloped from air autoxidation. Concentration of these (e.g., magnesium powder, zinc dust, carbon powder, peroxides during distillation may lead to explosion. and flowers of sulfur) in the air can constitute power- Ferrous salts or sodium bisulfite can be used to decom- ful explosive mixtures. These materials should be used pose these peroxides, and passage over basic active with adequate ventilation and should not be exposed alumina can remove most of the peroxidic material. In to ignition sources. When finely divided, some solids, general, however, dispose of old samples of ethers if including zirconium, titanium, Raney nickel, lead (such they test positive test for peroxide. as prepared by pyrolysis of lead tartrate), and catalysts Diisopropyl ether is a notoriously dangerous, Class (such as activated carbon containing active metals and A (see Chapter 4, Table 4.8 and section 4.D.3.2) peroxide hydrogen), can combust spontaneously if allowed to former. The peroxide is not completely soluble in the dry while exposed to air and should be handled wet.
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137 WORKING WITH CHEMICALS Ethylene oxide (C2H4O) has been known to explode organic materials such as leather, natural rubber, wood, when heated in a closed vessel. Experiments using and human tissue. Although HF is nonflammable, its ethylene oxide under pressure should be carried out corrosive action on metals can result in the formation of behind suitable barricades. hydrogen in containers and piping, creating a fire and Fluorine (F2) is an extremely toxic reactive oxidizing explosion hazard. HF should be stored in tightly closed gas with extremely low permissible exposure levels. polyethylene containers. HF attacks glass and therefore Only trained personnel should be authorized to work should never be stored in a glass container. Contain- with fluorine. (See Vignette 6.4.) Anyone planning to ers of HF may be hazardous when empty because work with fluorine must be knowledgeable of proper they retain product residues. HF and related materials first-aid treatment and have the necessary supplies on (e.g., NaF, SF4, acyl fluorides) capable of generating hand before beginning. HF upon exposure to acids, water, or moisture are of Halogenated compounds , such as chloroform major concern because of their potential for causing (CHCl3), carbon tetrachloride (CC14), and other halo- serious burns. genated solvents, should not be dried with sodium, po- HF causes severe injury via skin and eye contact, tassium, or other active metals; violent explosions usu- inhalation, and ingestion. It is very aggressive physi- ally result. Many halogenated compounds are toxic. ologically because the fluoride ion readily penetrates Oxidized halogen compounds—chlorates, chlorites, the skin and may cause decalcification of the bones bromates, and iodates—and the corresponding peroxy and systemic toxicity, including pulmonary edema, compounds may be explosive at high temperatures. cardiac arrhythmia and death. Burns from HF may not Hydrogen fluoride and hydrogen fluoride genera- be painful or visible for several hours and even moder- tors. Anhydrous HF or hydrogen fluoride is a colorless ate exposure to concentrated HF can result in fatality. liquid that boils at 19.5 ºC. It has a pungent irritating Unlike other acids which are rapidly neutralized, this odor, and a time-weighted average exposure of 3 ppm process may continue for days if left untreated. for routine work. Aqueous HF is a colorless very cor- Strong HF acid concentrations (over 50%), particu- rosive liquid that fumes at concentrations greater than larly anhydrous HF, cause immediate, severe, burning 48%. It attacks glass, concrete, and some metals, espe- pain and a whitish discoloration of the skin that usually cially cast iron and alloys containing silica as well as proceeds to blister formation. In contrast to the imme- diate effects of concentrated HF, the onset of effects of contact with more dilute solutions or their vapors may be delayed. Skin contact with acid concentrations in VIGNETTE 6.4 the 20% to 50% range may not produce clinical signs Fluorine inhalation or symptoms for 1 to 8 hours. With concentrations less than 20%, the latent period may be up to 24 hours. The A graduate student was filling the chamber usual initial signs of a dilute solution HF burn are red- of an excimer laser with fluorine gas. The gas ness, swelling, and blistering, accompanied by severe was connected to the laser with copper tubing. throbbing pain. Burns larger than 25 in.2 (160 cm2) may Over the course of 1 hour, the student noticed result in serious systemic toxicity. the chamber was not filling even though the gas When exposed to air, concentrated solutions and continued to flow. There was an odor in the room anhydrous HF produce pungent fumes which are es- but the student was concerned that the chamber pecially dangerous. Acute symptoms of inhalation of was not filling as expected and remained in the HF include coughing, choking, chest tightness, chills, room to try and determine what the problem fever, and cyanosis (blue lips and skin). All individuals was. That evening the student experienced chest suspected of having inhaled HF should seek medical pain and difficulty breathing and went to the attention and observation for pulmonary effects. This emergency room. She was diagnosed with pul- includes any individuals with HF exposure to the head, monary edema due to the prolonged exposure chest, or neck areas. HF exposures require immediate to fluorine gas. and specialized first aid and medical treatment. Fluorine is exceedingly toxic, with allowable For skin exposure: exposure levels of 1 ppm or less. The fluorine cylinder, laser, and piping should have been 1. Immediately start rinsing under safety shower contained in a ventilated enclosure. An alarmed or other water source and flush affected area fluorine gas detector should have been used in thoroughly with large amounts of water, remov- the work area. The student was not adequately ing contaminated clothing while rinsing. Speed trained to recognize the signs or hazards of fluo- and thoroughness in washing off the acid is of rine exposure. primary importance.
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138 PRUDENT PRACTICES IN THE LABORATORY 2. Call for emergency response. • Establish written standard operating procedures 3. While wearing neoprene or butyl rubber gloves for work with HF. to avoid a secondary HF burn, massage 2.5% • Ensure that all workers in a lab where HF is used (w/w) calcium gluconate gel onto the affected are informed about the hazards and first-aid pro- area after 5 minutes of flushing with water. If cedures involved. calcium gluconate gel is unavailable, continue • Only use HF in a chemical hood. flushing the exposed areas with water until • Depending on the concentration used, workers should wear butyl rubber, neoprene, 4H® or Sil- medical assistance arrives. vershield® gloves. Protective lab coats or aprons 4. Send a copy of the MSDS with the victim. are also recommended. For eye exposure: • At a minimum, workers should wear chemical splash goggles when working with HF. A face 1. I mmediately flush the eyes, holding eyelids shield is also recommended when there is a sig- open, for at least 15 minutes with large amounts nificant splash hazard. of gently flowing water, preferably using an eye- wash station. Hydrogen peroxide (H2O2) stronger than 3% can be 2. Do not apply calcium gluconate gel directly onto dangerous; in contact with skin, it causes severe burns. the eye. Thirty percent H2O2 may decompose violently if con- 3. Seek medical attention. taminated with iron, copper, chromium, or other met- 4. Send a copy of the MSDS with the victim. als or their salts. Stirring bars may inadvertently bring metal into a reaction and should be used with caution. For inhalation: Liquid nitrogen–cooled traps open to the atmo- sphere condense liquid air rapidly. When the coolant 1. Immediately move to fresh air. is removed, an explosive pressure buildup occurs, usu- 2. Call emergency responders. ally with enough force to shatter glass equipment if the 3. Send a copy of the MSDS with the victim. system has been closed. Hence, only sealed or evacu- ated equipment should be so cooled. Vacuum traps For ingestion: must not be left under static vacuum; liquid nitrogen in Dewar flasks must be removed from these traps when 1. Ingestion of HF is a life-threatening emergency. the vacuum pumps are turned off. Seek immediate medical attention. Lithium aluminum hydride (LiAlH4) should not be 2. Drink large amounts of water or milk as quickly used as a drying agent for solvents that are hygroscopic as possible to dilute the acid. and may contain high concentrations of water, such as 3. Do not induce vomiting. Do not ingest emetics or methyl ethers and tetrahydrofuran; fires from reaction baking soda. Never give anything by mouth to with damp ethers are often observed. Predrying these solvents with a less efficient drying agent, followed an unconscious person. 4. If medical attention must be delayed and the by LiAlH4 treatment is recommended. The reaction of materials are available, drink several ounces of LiAlH4 with carbon dioxide has reportedly generated milk of magnesia or other antacids. explosive products. Carbon dioxide or bicarbonate 5. Send a copy of the MSDS with the victim. extinguishers should not be used for LiAlH4 fires; instead, such fires should be smothered with sand or Laboratory personnel should be trained in first-aid some other inert substance. procedures for HF exposure before beginning work. Nitric acid is a strong acid, very corrosive, and de- Calcium gluconate gel (2.5% w/w) must be readily composes to produce nitrogen oxides. The fumes are accessible in work areas where any potential HF expo- very irritating, and inhalation may cause pulmonary sure exists. Check the expiration date of your supply edema. Nitric acid is also a powerful oxidant and reacts of commercially obtained calcium gluconate gel and violently, sometimes explosively reducing agents (e.g., reorder as needed to ensure a supply of fresh stock. organic compounds) with liberation of toxic nitrogen Note that homemade calcium gluconate gel has a shelf oxides. Contact with organic matter must be avoided. life of approximately 4 months. Extreme caution must be taken when cleaning glass- There are a number of ways to prevent HF exposure: ware contaminated with organic solvents or material with nitric acid. Toxic fumes of NOx are generated and • Only use HF when necessary. Consider substi- explosion may occur. tution of a less hazardous substance whenever Nitrate, nitro, and nitroso compounds may be ex- possible. plosive, especially if more than one of these groups
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139 WORKING WITH CHEMICALS is present in the molecule. Alcohols and polyols may facturers. Disassembly of such chemical hoods must be form highly explosive nitrate esters (e.g., nitroglycer- preceded by washing the ventilation system to remove ine) from reaction with nitric acid. deposited perchlorates. Organometallics may be hazardous because some Permanganates are explosive when treated with sul- organometallic compounds burn vigorously on contact furic acid. If both compounds are used in an absorption with air or moisture. For example, solutions of tert- train, an empty trap should be placed between them butyllithium ignite some organic solvents on exposure and monitored for entrapment. to air. The pertinent information should be obtained for Peroxides (inorganic) should be handled carefully. a specific compound. When mixed with combustible materials, barium, so- Oxygen tanks should be handled with care because dium, and potassium peroxides form explosives that serious explosions have resulted from contact between ignite easily. oil and high-pressure oxygen. Oil or grease should not Phenol is a corrosive and moderately toxic substance be used on connections to an O2 cylinder or gas line that affects the central nervous system and can cause carrying O2. damage to the liver and kidneys. Phenol-formaldehyde Ozone (O3) is a highly reactive toxic gas. It is formed reactions are used in creation of phenolic resins, and by the action of ultraviolet light on oxygen (air), and can be highly exothermic. These reactions have been therefore certain ultraviolet sources may require vent- implicated in a number of plant-scale accidents when ing to the exhaust hood. Ozonides can be explosive. runaway reactions caused a sudden rise in pressure Palladium (Pd) or platinum (Pt) on carbon, plati- and rupturing of pressure disks or vessels (Urben and num oxide, Raney nickel, and other catalysts presents Bretherick, 1999). Care should be taken if performing the danger of explosion if additional catalyst is added such reactions in the laboratory. to a flask in which an air-flammable vapor mixture or Phenol is readily absorbed through the skin and can hydrogen is present. The use of flammable filter paper cause severe burns to the skin and eyes. Phenol is ir- should be avoided. ritating to the skin, but has a local anesthetic effect, so Perchlorates should be avoided whenever possible. that no pain may be felt on initial contact. A whiten- Perchlorate salts of organic, organometallic, and inor- ing of the area of contact generally occurs and severe ganic cations are potentially explosive and may deto- burns may develop hours after exposure. Exposure to nate by heat or shock. Whenever possible, perchlorate phenol vapor can cause severe irritation of the eyes, should be replaced with safer anions such as fluorobo- nose, throat, and respiratory tract. In the event of skin rate, fluorophosphates, and trifluoromethanesulfonate exposure to phenol, do not immediately rinse the site (triflate). with water. Instead, treat the site with low-molecular- Perchlorates should not be used as drying agents weight poly(ethylene glycol) (PEG) such as PEG 300 if there is a possibility of contact with organic com- or PEG 400. This will safely deactivate phenol. Irrigate pounds or of proximity to a dehydrating acid strong the site with PEG for at least 15 minutes or until there enough to concentrate the perchloric acid (HClO4) (e.g., is no detectable odor of phenol. in a drying train that has a bubble counter containing Phosphorus (P) (red and white) forms explosive sulfuric acid). Safer drying agents should be used. mixtures with oxidizing agents. White phosphorus Seventy percent HClO4 boils safely at approximately should be stored underwater because it ignites sponta- 200 °C, but contact of the boiling undiluted acid or the neously in air. The reaction of phosphorus with aque- hot vapor with organic matter, or even easily oxidized ous hydroxides gives phosphine, which is toxic and inorganic matter, leads to serious explosions. Oxidiz- also may either ignite spontaneously or explode in air. able substances must never be allowed to contact Phosphorus trichloride (PCl3) reacts with water HClO4. This includes wooden benchtops or laboratory to form phosphorous acid with HCl evolution; the chemical hood enclosures, which may become highly phosphorous acid decomposes on heating to form flammable after absorbing HClO4 liquid or vapors. phosphine, which may either ignite spontaneously or Beaker tongs, rather than rubber gloves, should be explode. Care should be taken in opening containers of used when handling fuming HClO4. Perchloric acid PCl3, and samples that have been exposed to moisture evaporations should be carried out in a chemical hood should not be heated without adequate shielding to that has a good draft. protect the operator. The hood and ventilator ducts should be washed Piranha solution is a mixture of concentrated sul- with water frequently (weekly; but see also Chapter furic acid and 30% hydrogen peroxide. It is a power- 9, section 9.C.2.10.5) to avoid danger of spontaneous ful oxidant and strong acid used to remove organic combustion or explosion if this acid is in common use. residues from various surfaces. Many instances of Special HClO4 hoods are available from many manu- explosions have been reported with this solution upon
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140 PRUDENT PRACTICES IN THE LABORATORY 6.G.7 Chemical Hazards of Incompatible contact with reducing agents, especially organics. The Chemicals solution slowly evolves oxygen, and therefore contain- ers must be vented at all times. For each chemical, follow specific storage recom- Potassium (K) is much more reactive than sodium; it mendations in MSDSs and other references with ignites quickly on exposure to humid air, and therefore respect to containment and compatibility. Keep in- should be handled under the surface of a hydrocarbon compatibles separate during transport, storage, use, solvent such as mineral oil or toluene (see Sodium, and disposal (see Chapter 4, section 4.D; Chapter 5; below). Potassium can form a crust of the superoxide and section 6.C). Contact could result in a serious ex- (KO2) or the hydrated hydroxide (KOH·H2O) on con- plosion or the formation of substances that are highly tact with air. If this happens, the act of cutting a surface toxic or flammable. Store oxidizers, reducing agents, crust off the metal or of melting the encrusted metal and fuels separately to prevent contact in the event of can cause a severe explosion due to oxidation of the an accident. Some reagents pose a risk on contact with organic oil or solvent by superoxide, or from reaction of the atmosphere. the potassium with water liberated from the hydrated hydroxide (Yarnell, 2002). 6.H WORKING WITH COMPRESSED GASES Residues from vacuum distillations h ave been known to explode when the still was vented suddenly 6.H.1 Chemical Hazards of Compressed to the air before the residue was cool. To avoid such Gases explosions, vent the still pot with nitrogen, cool it be- fore venting, or restore pressure slowly. Sudden vent- Compressed gases expose laboratory personnel ing may produce a shock wave that explodes sensitive to both chemical and physical hazards. If the gas is materials. flammable, flash points lower than room temperature, Sodium (Na) should be stored in a closed container compounded by rapid diffusion throughout the labora- under kerosene, toluene, or mineral oil. Scraps of so- tory, present the danger of fire or explosion. Additional dium or potassium should be destroyed by reaction hazards arise from the reactivity and toxicity of the gas. with n-butyl alcohol. Contact with water should be Asphyxiation can be caused by high concentrations of avoided because sodium reacts violently with water even inert gases such as nitrogen. An additional risk to form hydrogen (H2) with evolution of sufficient heat of simple asphyxiants is head injury from falls due to to cause ignition. Carbon dioxide, bicarbonate, and rapid loss of oxygen to the brain. Death can also occur carbon tetrachloride fire extinguishers should not be if oxygen levels remain too low to sustain life. Finally, used on alkali metal fires. Metals such as sodium be- the large amount of potential energy resulting from come more reactive as the surface area of the particles the compression of the gas makes a highly compressed increases. Prudence dictates using the largest particle gas cylinder a potential rocket or fragmentation bomb. size consistent with the task at hand. For example, use Monitoring for leaks and proper labeling are es- of sodium balls or cubes is preferable to use of sodium sential for the prudent use of compressed gases. If sand for drying solvents. relatively small amounts are needed, consider on-site Sodium amide (NaNH2) can undergo oxidation on chemical gas generation as an alternative to com- exposure to air to give sodium nitrite in a mixture that pressed gas. Reduce risks by monitoring compressed is unstable and may explode. gas inventories and disposing of or returning gases Sulfuric acid (H2SO4) should be avoided, if possible, for which there is no immediate need. The equipment as a drying agent in desiccators. If it must be used, glass required for the safe use of compressed gases is dis- beads should be placed in it to help prevent splashing cussed in Chapter 7, section 7.D. when the desiccator is moved. To dilute H2SO4, the acid should be added slowly to cold water. Addition of 6.H.2 Specific Chemical Hazards of Select water to the denser H2SO4 can cause localized surface Gases boiling and spattering on the operator. tert-Butyllithium. See Alkyllithium compounds, above. Workers are advised to consult LCSSs and MSDSs for Trichloroethylene (Cl2CCHCl) reacts under a vari- specific gases. Certain hazardous substances that may be ety of conditions with potassium or sodium hydroxide supplied as compressed gases are listed below: to form dichloroacetylene, which ignites spontane- Boron trifluoride and boron trichloride (BF3 and ously in air and explodes readily even at dry-ice tem- BCl3, respectively) react with water to give HF and peratures. The compound itself is highly toxic, and HCl, respectively. Their fumes are corrosive, toxic, and suitable precautions should be taken when it is used. irritating to the eyes and mucous membranes. Chlorine trifluoride (ClF3) in liquid form is corrosive
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141 WORKING WITH CHEMICALS and very toxic. It is a potential source of explosion and odor. They are corrosive irritants to the skin, eyes, and causes deep penetrating burns on contact with the mucous membranes. When silyl halides are heated, body. The effect may be delayed and progressive, as in toxic fumes can be emitted. the case of burns caused by hydrogen fluoride. Chlorine trifluoride reacts vigorously with water 6.I WORKING WITH MICROWAVE OVENS and most oxidizable substances at room temperature, frequently with immediate ignition. It reacts with most Do not use domestic microwave ovens for laboratory metals and metal oxides at elevated temperatures. In work. Metal-based or volatile, flammable, and explo- addition, it reacts with silicon-containing compounds sive compounds pose a significant hazard when used and thus can support the continued combustion of in a domestic microwave oven. Domestic microwave glass, asbestos, and other such materials. Chlorine ovens do not provide mechanisms for monitoring trifluoride forms explosive mixtures with water vapor, temperature and pressure and contain no safeguards ammonia, hydrogen, and most organic vapors. The against explosion. Instead, use an industrial grade substance resembles elemental fluorine in many of its instrument (equipped with explosion-proof chambers, chemical properties and handling procedures, which exhaust lines, and temperature and pressure monitors) include precautionary steps to prevent accidents. suitable for such experiments. Hydrogen selenide (H2Se) is a colorless gas with an Although industrial ovens may reduce the risk of offensive odor. It is a dangerous fire and explosion risk such hazards, significant caution is required in their and reacts violently with oxidizing materials. Hydro- use. In general, the use of closed vessels should be gen selenide is an irritant to eyes, mucous membranes, avoided. Any reactions conducted in a microwave and the pulmonary system. Acute exposures can cause oven should be regarded with the same caution as symptoms such as pulmonary edema, severe bronchi- those conducted with highly reactive and explosive tis, and bronchial pneumonia. Symptoms also include chemicals. Reactions should use the smallest scale pos- gastrointestinal distress, dizziness, increased fatigue, sible to determine the potential for explosions and fires and a metallic taste in the mouth. (refer to sections 6.F and 6.G). Precautions should be Hydrogen sulfide (H2S) is a highly toxic and flam- taken for proper ventilation and potential explosion. mable gas. Although it has a characteristic odor of (See Chapter 7, section 7.C.5.7 for more information rotten eggs, it fatigues the sense of smell. This could about the use of microwave ovens in laboratories.) result in failure to notice the seriousness of the situa- tion before health becomes at risk and is problematic 6.J WORKING WITH NANOPARTICLES for rescuers who think danger has passed when the odor disappears. 6.J.1 Controls for Research and Methyl chloride (CH3Cl) has a slight, not unpleas- Development Laboratory ant, odor that is not irritating and may pass unnoticed Operations That Utilize or unless a warning agent has been added. Exposure to Synthesize Nanomaterials excessive concentrations is indicated by symptoms similar to those of alcohol intoxication, that is, drowsi- Nanoparticles are dispersible particles between 1 ness, mental confusion, nausea, and possibly vomiting. and 100 nm in size that may or may not exhibit a size- Methyl chloride may, under certain conditions, react related intensive property. The U.S. Department of with aluminum or magnesium to form materials that Energy (DOE, 2008, 2009) states that engineered nanoma- ignite or fume spontaneously with air, and contact with terials are intentionally created (in contrast with natural these metals should be avoided. or incidentally formed) and engineered to be between Phosphine (PH3) is a spontaneously flammable and 1 and 100 nm. This definition excludes biomolecules explosive poisonous colorless gas with the foul odor of (proteins, nucleic acids, and carbohydrates). decaying fish. The liquid can cause frostbite. Phosphine Nanoparticles and nanomaterials have different is a dangerous fire hazard and ignites in the presence of reactivities and interactions with biological systems air and oxidizers. It reacts with water, acids, and halo- than bulk materials, and understanding and exploiting gens. If heated, it forms hydrogen phosphides, which these differences is an active area of research. However, are explosive and toxic. There may be a delay between these differences also mean that the risks and hazards exposure and the appearance of symptoms. associated with exposure to engineered nanomaterials Silane ( SiH 4) is a pyrophoric colorless gas that are not well known. At the time this book was written, ignites spontaneously in air. It is incompatible with NIOSH had only defined occupational exposure limits water, bases, oxidizers, and halogens. The gas has a for one nanomaterial, titanium dioxide. Until material- choking repulsive odor. specific guidance can be issued, NIOSH, DOE, the Brit- Silyl halides are toxic colorless gases with a pungent ish Standards Institute, and others have issued general
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142 PRUDENT PRACTICES IN THE LABORATORY guidelines for management of engineered nanomateri- nanomaterials or other incompatible materials als. The procedures outlined here are based on those already captured in exhaust air filters. guidelines, which were developed from accepted chemical hygiene protocols for handling compounds When developing controls for the nanomaterials, of unknown toxicity. consider, but do not unquestioningly rely on, chemi- Because this is an area of ongoing research, consult cal hazard information for bulk or raw materials and trusted sources to ensure that the methods described any new information specific to the material at the here are not obsolete, and check for any applicable scale being used. When evaluating the hazards and material-specific guidance. Sources include uncertainties for the materials, consider the recognized and foreseeable hazards of the precursor materials and • Approaches to Safe Nanotechnology: Managing the intermediates as well as those of the resulting nano- materials. Note that the higher reactivity of many na- Health and Safety Concerns Associated with Engi- neered Nanomaterials (HHS/CDC/NIOSH, 2009a), noscale materials suggests that they should be treated and the NIOSH nanotechnology topic Web page, as potential sources of ignition, accelerants, and fuel www.cdc.gov/niosh; that could result in fire or explosion. • Nanoscale Science Research Centers: Approach to The risk of exposure may continue after laboratory Nanomaterial ES&H (DOE, 2008); work has been completed if, for example, a laboratory • ASTM E 2535-07: Standard Guide for Handling Un- chemical hood was used to house a reaction. Before removing, remodeling, servicing, maintaining, or re- bound Engineered Nanoscale Particles in Occupational Settings (ASTM International, 2007b); pairing laboratory equipment and exhaust systems, • the National Nanotechnology Initiative, www. evaluate the potential for trained laboratory person- nano.gov; and nel’s (including laboratory and maintenance workers) • the United Kingdom’s Health and Safety Execu- exposure to nanomaterials and escape of the materials tive Web site, at www.hse.gov.uk. into the environment. 6.J.1.1 Nanomaterial Work Planning and Hazard 6.J.1.2 A Graded Approach to Determining Assessment Appropriate Nanomaterial Controls Before beginning any work with or intended to pro- When performing the assessment described above, duce nanomaterials, perform a safety assessment for follow a graded approach in specifying controls. For the laboratory. Involve the organization’s EHS person- example, from the perspective of managing the health nel in the process, and consult subject-matter experts of laboratory personnel, easily dispersed dry nano- as needed. The assessment should materials pose the greatest health hazard because of the risk of inhalation, and operations involving these • include a well-defined description of the work; nanomaterials deserve more attention and more strin- • identify the state of the nanomaterials at each gent controls than those where the nanomaterials are stage of the work (i.e., dry and dispersible, in a embedded in solid or suspended in liquid matrixes. slurry or solution, affixed to a matrix, or embed- The list below and Figure 6.1 describe the graded risk ded in a solid); posed by the state of the material. Preference should • identify recognized and suspected hazards and be given to handling materials in the lower risk forms uncertainties, both biological and physical, at each (top of the list). stage; • specify hazard controls including 1. solid materials with embedded nanostructures, engineering controls, 2. solid nanomaterials with nanostructures fixed to identification of appropriate PPE, the material’s surface, training plans for laboratory personnel, 3. nanoparticles suspended in liquids, and emergency procedures, including spill or re- 4. d ry dispersible (engineered) nanoparticles, lease response, n anoparticle agglomerates, or nanoparticle experimental design elements to minimize risk aggregates. of exposure, and any other administrative controls; Be sure to consider all routes of possible exposure to • evaluate the potential for generating new nano- nanomaterials including inhalation, ingestion, injec- material-bearing waste streams and define waste tion, and dermal contact (including eye and mucous management protocols for these streams; and membranes). Avoid handling nanomaterials in the • consider the potential for reactions involving open air in a free-particle state. Whenever possible,
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143 WORKING WITH CHEMICALS U.S. Department of Energy graded risk for nanomaterials matrix FIGURE 6.1 U.S. Department of Energy graded exposure risk for nanomaterials. This figure assumes no disruptive force (e.g., sonication, grinding, burning) is applied to the matrix. SOURCE: Adapted from Karn (2008). handle and store dispersible nanomaterials, whether fugitive emissions of nanomaterials or hazardous pre- suspended in liquids or in a dry particle form, in closed cursors that might be released. For example, use a local (tightly sealed) containers. Unless cutting or grinding exhaust system such as a snorkel hood. Laboratory occurs, nanomaterials that are not in a free form (en- ventilation and exhaust systems should be chosen on capsulated in a solid or a nanocomposite) typically will the basis of what is known about nanoparticle motion not require engineering controls. If a synthesis is being in air. (For more information about ventilation options, performed to create nanomaterials, it is not enough to see Chapter 9, section 9.E.5.) only consider the final material in the risk assessment. Do not exhaust unfiltered effluent (air) that has Consider the hazardous properties of the precursor been demonstrated or strongly suspected to contain materials as well as those of the resulting nanomate- engineered nanoparticles to the laboratory. Whenever rial product. practical, filter it or otherwise clean (scrub) it before releasing it to the outdoors. Although HEPA filtration appears to effectively remove nanoparticles from air, 6.J.1.3 Engineering Controls for Nanomaterials the filters must be held in well-designed housings. A Research poorly seated filter can allow nanomaterials to escape through the gaps. If it is not practicable to contain 6.J.1.3.1 ork Area Design W the nanoparticles with such a system, conduct and When evaluating the work area, consider the need document the results of a hazard analysis before using for additional engineering or procedural controls to en- alternative hazard controls. sure trained laboratory personnel are protected in areas Exhaust the effluent from the ventilated enclo- where engineered nanoparticles will be handled. Addi- sure outside the building whenever feasible. Filters, tional controls to ensure that engineered nanoparticles scrubbers, or bubblers used to treat unreacted precur- are not brought out of the work area on clothing or sors appropriately may also be effective in reducing other surfaces may be advisable. Examples of possible nanomaterial emissions. If using portable benchtop additional controls include installing step-off pads to HEPA-filtered units, exhaust them through ventilation trap dust, creating a buffer area around the work zone, systems that carry the effluent outside the building and ensuring the availability of decontamination facili- whenever possible. ties (possibly for daily use) for laboratory personnel. If it is not feasible to duct HEPA-filtered treated exhaust air outside the building, follow the guid- 6.J.1.3.2 entilation Preferences V ance in ANSI Z9.7-2007, American National Standard To minimize laboratory personnel exposure, conduct for Recirculation of Air from Industrial Process Exhaust any work that could generate engineered nanoparticles Systems, and conduct a hazard assessment to identify in an enclosure that operates at a negative pressure appropriate engineering controls. Examples of such differential compared to the laboratory personnel controls include periodic air monitoring and an accu- breathing zone. Examples of such enclosures include rate warning or signal capable of initiating corrective gloveboxes, glovebags, and laboratory benchtop or action or process shutdown before nanoparticles are floor-mounted chemical hoods. Do not use horizontal exhausted or reenter the work area. If using a Type II laminar-flow hoods (clean benches) that direct a flow of biological safety cabinet for work with nanomateri- HEPA-filtered air into the user’s face for operations in- als, consider exhausting directly to the exterior (hard volving engineered nanomaterials. If the air reactivity ducted) or through a thimble connection over the of precursor materials may make it unsafe to perform cabinet’s exhaust. a synthesis in a negative-pressure glovebox, a positive- All exhaust systems should be maintained and tested pressure box may be used if it has passed a helium as specified by the manufacturer. Before beginning any leak test. If a process (or subset of a process) cannot maintenance, however, evaluate equipment for con- be enclosed, use other engineering systems to control tamination and chemical incompatibilities.
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144 PRUDENT PRACTICES IN THE LABORATORY (HHS/CDC/NIOSH, 2009a) and Respirator Selection 6.J.1.3.3 lothing and PPE C Logic (Bollinger, 2004) for guidance on choosing ap- Minimal data exist regarding the efficacy of PPE propriate air-purifying particulate respirators. These against exposure to nanoparticles. However, until documents are available online at www.cdc.gov/ further information is available, it is prudent to follow niosh. If employees are required to wear respirators, standard chemical hygiene practices. Conduct a hazard consideration must be given to the OSHA regulation evaluation to determine PPE appropriate for the level 29 CFR § 1910.134. of hazard according to the requirements set forth in 29 Keep potentially contaminated clothing and PPE CFR § 1910.132. Protective clothing that would typi- in the laboratory or change-out area to prevent en- cally be required for a wet-chemistry laboratory would gineered nanoparticles from being transported into be appropriate and could include but is not limited to common areas. Clean and dispose of all potentially contaminated • closed-toed shoes made of a low-permeability clothing and PPE in accordance with the laboratory material (disposable over-the-shoe booties may be procedures. necessary to prevent tracking nanomaterials from the laboratory); 6.J.1.3.4 onitoring and Characterization M • long pants without cuffs; The NIOSH publication Approaches to Safe Nano- • long-sleeved shirt; technology (HHS/CDC/NIOSH, 2009a) describes an • gauntlet-type gloves or nitrile gloves with ex- emission assessment technique that can be used for tended sleeves; and identification of sources and releases of engineered • laboratory coats. nanomaterials. The technique includes determin- ing the particle number concentration using direct- Wear polymer (e.g., nitrile rubber) gloves when reading, handheld particle counters at potential handling engineered nanomaterials and particulates emission sources and comparing those data to back- in liquids. Choose gloves only after considering the ground particle number concentrations. If elevated resistance of the glove to chemical attack by both the concentrations of suspected nanoparticles are de- nanomaterial and, if suspended in liquids, the liquid. tected at potential emission sources, relative to the background particle number concentrations, then a • Recognize that exposure to nanomaterials is not pair of filter-based, source-specific air samples are known to have good warning properties, and collected with one sample analyzed by transmission change gloves routinely to minimize potential electron microscopy or scanning electron microscopy- exposure hazards. Alternatively, double glove. for particle identification and characterization, and • Keep contaminated gloves in a plastic bag or other the other used for determining the elemental mass sealed container until disposed of. concentration. • Dispose of contaminated gloves in accordance If resources allow, a more comprehensive and quan- with organizational requirements. titative approach using additional aerosol sampling • Wash hands and forearms after wearing gloves. equipment (such as impactors or diffusion charges) • Follow any additional institutional rules regard- may be performed. ing nanoparticles, such as proper waste disposal. 6.J.1.3.5 ousekeeping H Wear eye protection, for example, spectacle-type Practice good housekeeping in laboratories where safety glasses with side shields (meeting basic impact nanomaterials are handled. Follow a graded approach resistance of ANSI Z87.1-2003), face shields, chemical paying attention where dispersible nanomaterials are splash goggles, or other safety eyewear appropriate handled. Insofar as practicable, maintain all working to the type and level of hazard. Do not consider face surfaces (i.e., benches, glassware, apparatus, laboratory shields or safety glasses to provide sufficient protec- chemical hoods, support equipment) free of engineered tion against unbound dry materials that could become nanoparticle contamination and otherwise limit labora- airborne. tory personnel exposure to engineered nanoparticles Contact the organization’s EHS professionals for an and associated hazards. In areas where engineered evaluation of airborne exposures to engineered nano- nanoparticles might settle, perform precautionary materials. If respirators are to be used for protection cleaning, for example, by wiping horizontal surfaces against engineered nanoparticles, NIOSH-certified with a moistened disposable wipe, no less frequently respirators should provide the expected levels of pro- than at the end of each shift or day. tection if properly selected and fit-tested as part of a Before selecting a cleaning method, consider the complete respiratory protection program. Refer to the potential for complications due to the physical and NIOSH publications Approaches to Safe Nanotechnology
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145 WORKING WITH CHEMICALS chemical properties of the engineered nanoparticles, bearing waste according to the laboratory’s hazardous particularly in the case of larger spills. Complications chemical waste guidelines. could include reactions with cleaning materials and 6.J.1.3.7 arking, Labeling, and Signage M other materials in the locations where the waste will be held. Such locations include vacuum cleaner filters Post signs indicating hazards, PPE requirements, and and canisters. administrative control requirements at entry points Clean up dry engineered nanomaterials using into designated areas where dispersible engineered nanoparticles are handled. A designated area may be • Wet wiping. an entire laboratory, an area of a laboratory, or a con- • A dedicated approved HEPA vacuum with veri- tainment device such as a laboratory chemical hood or fied filtration effectiveness. (Note: Consider pos- glovebox. Clearly label storage containers to indicate sible pyrophoric hazards associated with vacu- that the contents are in engineered nanoparticulate uming up nanoparticles.) If using the vacuum form (e.g., nanoscale zinc oxide particles, or other for multiple types of nanomaterials, keep a log identifier instead of simply zinc oxide). of the materials captured and check for chemical When engineered nanoparticles are being moved incompatibilities prior to use. outside a laboratory, use leakproof double contain- • O ther facility-approved methods that do not ment. For example, use compatible double zip-lock involve an energetic cleaning method. Avoid dry bags or “Tupperware-type” containers, or proper ship- sweeping or the use of compressed air, to prevent ping containers. Include label text that indicates that suspension of particles into the air. the particulates might be unusually reactive and vary in toxic potential, quantitatively and qualitatively, from Note that vacuum brushes may generate electro- normal size forms of the same material. (See Chapter 5, static charges that could make cleaning of charged section 5.F.2, for more information about transport and particles difficult. Consider using vacuum cleaners shipping of nanomaterials.) with electrostatic-charge-neutralization features (such 6.J.1.3.8 isposal of Nanomaterial-Bearing Waste D as those used for cleaning copier and printer toners.) Streams Again, be sure that the vacuum is exhausted through a properly fitted and maintained HEPA filter. Do not put material containing nanomaterials down Clean up spills of liquids containing nanomaterials the drain or in the regular trash. Contact the organiza- using absorbent materials. If the size of the spill is large, tion’s EHS personnel to assist in determining the ap- place absorbent pads at all points of egress from the propriate waste disposal method. Using the guidelines room to reduce tracking the spill into the other parts of provided by EPA (see Chapter 8), identify whether the building. Use plastic sheeting to reduce ventilation the material should be considered hazardous or non- in the area of a liquid spill to reduce the chance that it hazardous. Remember that nanomaterials often have will dry prior to cleanup. As noted above, dry nano- different reactivities than the bulk material, and while materials pose a greater hazard than those suspended bulk material properties can be used as a guide, do not in liquid. rely upon them to determine the properties of the nano- Dispose of used cleaning materials and wastes in materials. If the sample is in liquid, be sure to consider accordance with the laboratory’s hazardous waste the hazards of the liquid as well as the nanoparticles. procedures. As general guidance, DOE recommends collecting items that come in contact with nanomaterials, such 6.J.1.3.6 ork Practices W as PPE, wipes, and the like in a sealable plastic bag Evaluate hazards and implement work practices or other sealable container under appropriate ventila- to control potential contamination and exposure tion controls. When it is full, place the bag in a second hazards, if engineered nanoparticle powders must be sealable container before disposal. Label the waste handled without the use of exhaust ventilation (i.e., container as containing nanomaterials, and note any laboratory chemical hood, local exhaust) or enclosures particular hazards on the label. Notify the organiza- (i.e., glovebox). Take reasonable precautions to mini- tion’s hazardous waste handler that nanomaterials are mize the likelihood of skin contact with engineered in the waste stream. nanoparticles or nanoparticle-containing materi- 6.J.1.3.9 ersonnel Competency P als likely to release nanoparticles (nanostructures). Transfer engineered nanomaterial samples between Laboratory and support personnel who risk poten- workstations such as laboratory chemical hoods, tial exposure to engineered nanoparticles should be gloveboxes, furnaces in closed labeled containers given training on the risks of exposure and on safe (e.g., marked zip-lock bags). Handle nanomaterial- handling procedures. Do not assume that laboratory
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146 PRUDENT PRACTICES IN THE LABORATORY personnel or visiting researchers are aware of the • employing engineered controls, health and safety concerns posed by nanomaterials. At • using PPE, a minimum, provide personnel conducting hands-on • handling potentially contaminated laboratory work with an awareness-level orientation that will alert garments and protective clothing, them to concerns (potential hazards) and to the labora- • cleaning of potentially contaminated surfaces, tory’s policies concerning prudent material handling. • disposal of spilled nanoparticles, and Training should cover requirements and recommen- • use of respirators, if applicable. dations for