chapter (section 7.B) apply here also, multihazardous waste requires special management considerations because the treatment method for one of the hazards may be inappropriate for the treatment of another. For example, if a waste that contains a volatile organic solvent and infectious agents is autoclaved, it may release hazardous levels of solvent into the atmosphere. (For more on multihazardous waste, refer to Chapter 9, section 9.D.2.)

Management of multihazardous waste is complicated further by local or state requirements that may be inconsistent with the relative risk of each hazard and with sound waste management practices. Chemically hazardous waste that contains short-half-life radionuclides may, for example, be best managed by holding the waste in storage for decay, which may require up to 2 years. However, the EPA and state rules usually limit storage of chemically hazardous waste to 90 days.

Commercial treatment or disposal facilities for multihazardous waste from laboratories are scarce. Many of these waste types are unique to laboratories and are generated in such small volumes that there is little incentive for the development of a commercial market for their management.

While multihazardous waste is currently difficult and expensive to manage, it is generated in medical, biochemical, and other types of critically important research, as well as in clinical and environmental laboratories. As interdisciplinary techniques, technologies, and studies become more widely used, multihazardous waste will be more widely generated. Legally acceptable protocols for dealing with multihazardous waste need to be developed. (See also Chapter 4, section 4.B.3.)

Radioactive hazardous waste generated by laboratories is usually limited to low-level radioactive waste from the use of by-product material and naturally occurring or accelerator-produced radioactive material (NARM). By-product material, as defined by the U.S. Nuclear Regulatory Commission (U.S. NRC), is reactor-produced radioactive material and includes most purchased radiolabeled chemicals; NARM includes uranium and thorium salts. The use and disposal of by-product material are regulated by the U.S. NRC and usually require a license. NARM waste is not regulated by the U.S. NRC but may be regulated to some extent by some states. Common waste management methods for low-level radioactive waste from laboratories include storage for decay and indefinite on-site storage, burial at a low-level radioactive waste site, incineration, and sanitary sewer disposal.

Waste is considered biohazardous or infectious if it contains agents of sufficient virulence and quantity that exposure of a susceptible host could cause transmission of an infectious disease. Unlike chemical and radioactive waste, infectious or medical waste is currently not subject to federal regulations that govern its treatment, storage, or disposal. OSHA regulates the collection and containment of certain laboratory waste that contains human blood or body fluids in order to prevent exposure of personnel to blood borne pathogens. Although OSHA does not regulate waste treatment or disposal, its standard is often the impetus for managing infectious waste in laboratories. Putrescible waste, such as tissue and carcasses of laboratory animals, is also classified as biological waste, although putrescible laboratory waste is usually not biohazardous or infectious. Hypodermic needles, lancets, scalpel blades, and other medical laboratory sharps are considered biohazardous because of their potential for being contaminated with pathogens and the likelihood of accidental skin puncture. Biological waste may also include whole animals or plants made transgenic via recombinant DNA technology or into which recombinant DNA has been introduced. (See Chapter 5, section 5.E, on biohazards and radioactivity.)

Common management methods for biological waste include disinfection, autoclaving, and, for liquids, disposal in the sanitary sewer. Putrescible waste is usually disposed of by incineration, which destroys the unpleasant nature of these materials. Needles and sharps require destruction, typically by incineration or grinding. In general, if all hazards cannot be removed in one step, the goal is to reduce a multihazardous waste to a waste that presents a single hazard. This single-hazard waste can then be managed by standard methods for that category.

Most management principles apply to all types of waste. These universal management methods include waste minimization, training of laboratory personnel and waste handlers, reviewing proposed procedures, keeping dissimilar waste materials separate, identification of waste materials, and labeling of waste containers. However, multihazardous waste, because of its combination of hazards and regulatory controls, requires more complex attention, as detailed in the following guidelines:

  • Assess the risk posed by the waste's inherent hazards. Laboratories often have flexibility to define those waste characteristics whose hazards are so low (de minimis) as to not present a significant risk. For example, the U.S. NRC or state authority may allow a licensee to propose limits below which laboratory waste can be designated as noncontaminated and disposed of as nonradioactive waste. (Some licensees have agreed with their regulators to consider some wastes nonradioactive if effluent concentrations are less than

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