Hospitals generate large amounts of diverse wastes that require disposal. Much of the waste is hazardous and must therefore be packaged, transferred, and disposed of properly to protect both the persons handling it and the environment.

Hospital wastes can be categorized as infectious or noninfectious. Infectious wastes include human, animal, or biological wastes and any items that may be contaminated with pathogens. Noninfectious wastes include toxic chemicals, cytotoxic drugs, and radioactive, flammable, and explosive wastes.

6.1 INFECTIOUS WASTES

The material in this section is extracted from the EPA guide for Infectious Waste Management (EPA 1986). The following publications are also recommended:

• Guideline for Handwashing and Hospital Environmental Control Section 4 (Garner and Favero 1985). This document reprinted in Append 8.

• Guideline for Isolation Precautions in Hospitals (Garner and Simmons 1983). This document is reprinted in Appendix 8.

• Waste Disposal in Microbiology Laboratories, Chapter 9 (Mackel and Mallison 1981).

6.1.1 Infectious Waste Management Plan

Compliance with State and local regulations should be carefully considered when developing an infectious waste treatment plan. Each hospital should develop an infectious waste treatment plan. Each hospital should develop an infectious waste management plan that provides for (1) Designation of the waste that should be managed as infectious, (2) Segregation of infectious waste from the noninfectious waste, (3) Packaging, (4) Storage, (5) Treatment, (6) Disposal, (7) Contingency measures for emergency situations, and (8) Staff training.

6.1.2 Types of Infectious Waste

Infectious wastes may be classified as isolation wastes, cultures and stocks of infectious agents and associated biologicals, human blood and blood products, pathological wastes, contaminated sharps, contaminated carcasses, body parts, and bedding, or miscellaneous contaminated wastes. Each of these categories is discussed briefly as follows:

• Isolation wastes are those generated by patients who are isolated because of communicable diseases.

• Cultures and stocks of infectious agents and associated biologicals include specimen cultures from medical and pathological laboratories, cultures and stocks of infectious agents from research and industrial laboratories, wastes from the production of biologicals, discarded live and attenuated vaccines, and culture dishes and devices used to transfer, inoculate, and mix cultures.

• Human blood and blood products include blood as well as serum, plasma, and other blood products.

• Pathological wastes include tissues, organs, body parts, and body fluids that are removed during surgery and autopsy.

• Contaminated sharps are hypodermic needles syringes, Pasteur pipettes, broken glass, and scalpel blades. These items should be considered infectious wastes because of the possibility of contamination with blood-borne pathogens.

• Contaminated carcasses, body parts, and bedding emanate from animals intentionally exposed to pathogens during research, the production of biologicals, or the in vivo testing of pharmaceuticals.

• Miscellaneous wastes that are not designated as infectious should be assumed to be infectious and should be managed as such to maintain consistent levels of protection for both the environment and for persons handling these wastes. Miscellaneous wastes include those from surgery and autopsies, contaminated laboratory wastes, dialysis unit wastes, and contaminated equipment.

  • Wastes from surgery and autopsies include soiled dressings, sponges, drapes, lavage tubes, drainage sets, underpads, and surgical gloves.

  • Contaminated laboratory wastes include specimen containers, slides and cover slips, disposable gloves, laboratory coats, and aprons.

  • Dialysis unit wastes include contaminated disposable equipment and supplies such as tubing, filters, disposable sheets, towels, gloves, aprons, and laboratory coats.

  • Contaminated equipment refers to discarded equipment and parts that are used in patient care, medical and industrial laboratories, research, and the production and testing of certain pharmaceuticals.

6.1.3 Treatment and Disposal Methods

Several methods are used for infectious waste treatment, depending on the type of waste material. These treatment methods include steam sterilization, incineration, thermal inactivation, gas/vapor sterilization, chemical disinfection, and sterilization by irradiation. After treatment, the wastes or their ashes can be disposed of by discharge into sanitary sewer systems (for liquid or ground-up waste) or burial in sanitary landfills. Acceptable treatment methods for the various types of wastes are listed in Table 6-1.

6.1.3.1 Steam Sterilization, Autoclaving

Steam sterilization, autoclaving, involves the use of saturated steam within a pressure vessel at temperatures high enough to kill infectious agents in the waste. Sterilization is accomplished primarily by steam penetration. Steam sterilization is most effective with low-density material such as plastics. An alternative treatment method, e.g. incineration, should be used on high-density wastes such as large body parts or large quantities of animal bedding or fluids because they inhibit direct steam penetration and require longer sterilization times.

Containers that can be used effectively in steam sterilization are plastic bags, metal pans, bottles, and flasks. High-density polyethylene and polypropylene plastic should not be used in this process because they do not facilitate steam penetration to the waste load. Heat-labile plastic bags allow steam penetration of the waste, but they may crumble and melt. If heat-labile plastic bags are used, they should be placed in another heat-stable container that allows steam penetration, such as a strong paper bag, or they should be treated with gas/vapor sterilization.

The following precautions should be taken when using steam sterilization:

• Plastic bags should be placed in a rigid container before steam treatment to prevent spillage and drain clogging.

• To facilitate steam penetration, bags should be opened and caps and stoppers should be loosened immediately before they are placed in the steam sterilizer.

• Care should be taken to separate infectious wastes from other hazardous wastes.

The following precautions should be taken when using steam sterilization:

• Plastic bags should be placed in a rigid container before steam treatment to prevent spillage and drain clogging.

• To facilitate steam penetration, bags should be opened and caps and stoppers should be loosened immediately before they are place in the steam sterilizer.

• Care should be taken to separate infectious wastes from other hazardous wastes.

• Infectious waste that contains noninfectious hazards (see Section 5) should not be steam-sterilized because of the possibility that the equipment operator will be exposed to toxic, radioactive, or other hazardous chemicals.

• Waste that contains antineoplastic drugs, toxic chemicals, or chemicals that would be volatilized by steam should not be steam-sterilized.

• Persons involved in steam sterilizing should be trained in handling techniques to minimize personal exposure to hazards from these wastes. Some of these techniques include:

  • Use of protective equipment

  • Minimization of aerosol formation

  • Prevention of waste spillage during autoclave loading and unloading

  • Prevention of burns from handling hot containers

  • Management of spills

• The autoclave temperature should be checked with a recording thermometer to ensure that the proper temperature is being maintained for a long enough period during the cycle.

• Steam sterilizers should be routinely inspected and serviced, and the process should be routinely monitored to ensure that the equipment is functioning properly.

6.1.3.2 Incineration

Incineration converts combustible materials into noncombustible residue or ash. Gases are ventilated through the incinerator stacks, and the residue or ash is disposed of in a sanitary landfill. If incinerators are properly designed, maintained, and operated, they are effective in killing organisms present in infectious waste. Although all types of infectious waste can be disposed of by incineration, the process is especially useful for anesthetic disposal of pathological wastes such as tissues and body parts. Incineration also renders contaminated sharps unusable. The principal factors to consider when incinerating infectious wastes are variations in waste composition, the waste feed rate, and the combustion temperature. Infectious wastes containing antineoplastic drugs should be disposed of in an incinerator that provides high temperatures and enough time for the complete destruction of these compounds. The incinerator’s effectiveness in disposing of chemical wastes should be documented before such use.

6.1.3.3 Thermal Inactivation

Thermal inactivation involves the treatment of waste with high temperatures to eliminate the presence of infectious agents. This method is usually used for large volumes of infectious waste. Liquid waste is collected in a vessel and heated by heat exchangers or a steam jacket surround the vessel. The types of pathogens in the waste determine the temperature and duration of treatment. After treatment, the contents can be discharged into the sewer in a manner that complies with State, Federal, and local requirements. Solid infectious waste is treated with dry heat in an oven, which is usually electric. This method requires higher temperatures and longer treatment cycles than steam treatment.

6.1.3.4 Gas/Vapor Sterilization

Gas/vapor sterilization uses gaseous or vaporized chemicals as the sterilizing agents. Ethylene oxide is the most commonly used agent, but should be used with caution since it is a suspected human carcinogen, see sec 5 for a discussion of ethylene oxide toxicity and work practices. Because ethylene oxide may be adsorbed on the surface of treated materials, the potential exists for worker exposure when sterilized materials are handled.

6.1.3.5 Chemical Disinfection

Chemical disinfection is the preferred treatment for liquid infectious wastes, but it can also be used in treating solid infectious waste. The following factors should be considered when using chemical disinfection:

• Type of microorganism

• Degree of contamination

• Amount of proteinaceous material present

• Type of disinfectant

• Contact time

• Other relevant factors such as temperature, pH, mixing requirements, and the biology of the microorganism

Ultimate disposal of chemically treated waste should be in accordance with State and local requirements.

6.1.3.6 Sterilization by irradiation

Sterilization by irradiation is an emerging technology that uses ionizing radiation. Advantages over other treatment methods are as follows:

• Electricity requirements are nominal.

• Steam is not required.

• No heat or chemicals remain the treated waste.

The principal disadvantages are as follows:

• Capital costs are high.

• Highly trained operating and support personnel are required.

• Space requirements are great.

• The potential exists for worker exposure as a result of leaks in seals or poor work practices.

• Ultimate disposal of the radiation source may pose problems.