ganisms that are potentially pathogenic. The purpose of the special procedures is to prevent the release of infectious agents to the environment. The procedures involve decontaminating the mixed hazardous chemical and biohazardous waste to eliminate the biohazardous characteristics of the waste prior to disposal. Autoclaving and chemical decontamination are the methods of choice for decontaminating biohazardous waste. Autoclaving volatile chemicals is not appropriate because this practice could cause the release of the chemical to the environment.

Disposal is most difficult for the very small amount of chemical–biological waste that is EPA-regulated as chemically hazardous or contains a chemical, such as lead, that is inappropriate for an animal or medical waste incinerator. Disposal of tissue specimens preserved in ethanol or another flammable solvent is also difficult. In most cases, storage of this waste is limited to 90 days and must be managed at an EPA-permitted chemical waste facility. However, few chemical waste facilities are prepared to handle waste that is putrescible, infectious, or biohazardous.

8.C.2.1 Disposal of Chemically Contaminated Animal Tissue

Animal carcasses and tissues that contain a toxic chemical may be the most prominent chemical–biological laboratory waste. Such waste includes biological specimens preserved in formalin and rodents that have been fed lead, mercury, or PCBs in toxicity studies. If storage of such putrescible waste is necessary, refrigeration is usually advisable. Infectious waste should be stored separately in a secure area.

Incineration, which destroys potential infectious agents, is the most appropriate disposal method for putrescible waste. Large research institutions are likely to have an on-site animal incinerator. Medical waste incineration is also available through commercial waste haulers.

(If animal or commercial incineration is unavailable, methods in section 8.C.3.3, below, may be adaptable to chemical–biological waste.)

8.C.2.2 Sewer Disposal of Chemical–Biological Liquids

Laboratories that manipulate infectious agents, blood, or body fluids may generate waste that is contaminated with these materials and toxic chemicals. In most cases, blood and body fluids that contain toxic chemicals can be disposed of safely in a sanitary sewer, which is designed to accept biological waste. Approval for such disposal should be requested from the local wastewater treatment works. Chemical concentrations in such waste are typically low enough to be accepted by a local treatment works. OSHA recommends that a separate sink be used exclusively for disposal of human blood, body fluids, and infectious waste. It may be prudent to treat blood and body fluids with bleach (usually a 1:10 aqueous dilution of household bleach) prior to disposal in the sanitary sewer. Laboratory personnel should take care to prevent personal exposure while waste is being discharged into the sewer.

8.C.2.3 Disinfection and Autoclaving of Contaminated Labware

Contaminated labware may include cultures, stocks, petri plates, and other disposable laboratory items (e.g., gloves, pipettes, and tips). In many cases, the small quantities of infectious waste on labware can be disinfected safely with bleach or other chemical disinfectant (e.g., by soaking overnight). Once disinfected, the labware can be treated as a chemical waste. Laboratory personnel must check with the state or regional EPA office to determine if a treatment permit is required for chemical disinfection of chemical–biological waste.

Autoclaves can be used to steam-sterilize infectious waste but should be tested routinely for efficacy. Autoclaving does not require an EPA permit. Care must be taken because autoclaving of chemical–biological waste at 120 to 130 °C may result in the volatilization or release of the chemical constituent. Additional waste containment may be needed to minimize chemical releases, but it can interfere with steam penetration into the waste load and sterilization. Before autoclaving, evaluate the waste to verify that the heat and pressure of autoclaving do not create unsafe conditions.

Autoclaving waste containing flammable liquids may result in a fire or explosion. Note also that steam sterilization of waste that contains bleach may harm an autoclave. To autoclave voluminous chemical– biological waste streams, it may be appropriate to dedicate an autoclave room with ample ventilation and to restrict access.

8.C.2.4 Disposal of Chemically Contaminated Medical Waste and Sharps

Laboratories that work with human blood must adhere to OSHA’s Standard for Occupational Exposure to Bloodborne Pathogens (29 CFR § 1910.1030), which requires waste containment, marking, and labeling. The OSHA standard also regulates waste disposal from laboratories that manipulate HIV or HBV. In general, such waste that has chemical contamination can be incinerated with other medical waste.

Waste hypodermic needles and other “sharps” (e.g.,

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