(EPA) defines chemically hazardous waste under the Resource Conservation and Recovery Act (RCRA), and the U.S. Nuclear Regulatory Commission (U.S. NRC) defines radioactivity hazards. Biological hazards are generally not defined within federal regulations.
Although we must consider and pay close attention to the regulatory definitions and procedures that govern the handling and disposal of waste, primary importance must be given to the safe and prudent handling of this material. It is important to remember that the danger associated with a specific hazardous waste depends not only on the composition of the waste, but also on its quantity. In fact, regulations recognize quantity in many of their definitions for hazard compliance as well as in the definitions of waste generators. The concept of de minimis quantities, that is, very small amounts of material, though not defined clearly, is also a consideration in determining hazardous waste risk. Enlightened risk management dictates that the amount of material be one factor in the decisions on handling and disposal of waste.
Waste that is regulated as hazardous because of its chemical properties is defined by EPA in two ways: (1) waste that has certain hazardous characteristics and (2) waste that is on certain lists of chemicals. The first category is based on properties of materials that should be familiar to every laboratory worker. The second category is based on lists, established by EPA and certain states, of certain chemicals common to industry. These lists generally include materials that are widely used and recognized as hazardous. Chemicals are placed on these RCRA lists primarily on the basis of their toxicity. (To determine if waste is hazardous or not, see Chapter 9, section 9.D.2.)
Regardless of the regulatory definitions of hazard, understanding chemical characteristics that pose potential hazards should be a fundamental part of the education and training of any laboratory worker. These characteristics may be derived from knowledge of the properties and/or precursors of the waste. The characteristics may also be established by specific tests cited in the regulations.
The properties that pose potential hazards are as follows:
Ignitability. Ignitable materials are defined as having one or more of the following characteristics:
Liquids that have a flash point of less than 60 °C or some other characteristic that has the potential to cause fire.
Materials other than liquids that are capable, under standard temperature and pressure, of causing fire by friction, adsorption of moisture, or spontaneous chemical changes and, when ignited, burn so vigorously and persistently as to create a hazard.
Flammable compressed gases, including those that form flammable mixtures.
Oxidizers that stimulate combustion of organic materials.
Ignitable materials include most common organic solvents, gases such as hydrogen and hydrocarbons, and certain nitrate salts.
Corrosivity. Corrosive liquids have a pH of 2 or less or 12.5 or greater or lead to corrosion of certain grades of steel. Most common laboratory acids and bases are corrosive. Solid corrosives, such as sodium hydroxide pellets and powders, are not legally considered by RCRA to be corrosive. However, laboratory workers must recognize that such materials can be extremely dangerous to skin and eyes and must be handled accordingly.
Reactivity. The reactivity classification includes substances that are unstable, react violently with water, are capable of detonation if exposed to some initiating source, or produce toxic gases. Alkali metals, peroxides and compounds that have peroxidized, and cyanide or sulfide compounds are classed as reactive.
Toxicity. Toxicity is established through the Toxicity Characteristic Leaching Procedure (TCLP), which measures the tendency of certain toxic materials to be leached (extracted) from the waste material under circumstances assumed to reproduce conditions of a landfill. The TCLP list includes a relatively small number of industrially important toxic chemicals and is based on the concentration above which a waste is considered hazardous. Failure to pass the TCLP results in classification of a material as a toxic waste.
Although EPA has developed several lists of hazardous waste, three regulatory lists are of most interest to laboratory workers:
the F list: waste from nonspecific sources (e.g., spent solvents and process or reaction waste),
the U list: hazardous waste (e.g., toxic laboratory chemicals), and
the P list: acutely hazardous waste (e.g., highly