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20.9.10 FIFRA REGISTRATION
Under The Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA), any chemical agent used
in a treatment process may require registration with the EPA Pesticide Registration Office. If a man-
ufacturer advertises that a chemical formulation can achieve a level of microbial inactivation (e.g.,
sterilant) for a specified use, that formulation would have to be registered with the EPA Office of
Pesticide Registration (Turnberg, 1996).

20.9.11 ADVANTAGES AND DISADVANTAGES OF CHEMICAL DISINFECTION
The combined shredding or chemical disinfection system is relatively simple. Furthermore, this
treatment train can substantially reduce waste volumes. After shredding, waste components are
essentially unrecognizable. Disadvantages of chemical disinfection include relatively high capital
and operating costs. There may be problems with contaminants in the slurry, concentrations of dis-
infectant in the work space (a potential irritant to nose, eyes, and lungs), noise levels, and bioaerosol
emissions (U.S. EPA, 1991). Discharge permits may be required for the slurry. Microbes may
become resistant to certain disinfectants. Finally, disinfection systems do not provide sterilization.

20.9.12 MICROWAVE IRRADIATION
During microwave treatment, waste is fed automatically to a grinding device where it is shredded and
sprayed with steam to increase the moisture content to about 10%. The moist ground waste is then
heated by exposure to microwave irradiation units over 2 h. Microwaves are electromagnetic waves
having a frequency between infrared and radio waves. A typical industry standard radio frequency
energy of 2450 MHz is absorbed by the waste to create friction in water molecules. Heat generated by
this friction denatures proteins within the microbial cell thereby killing and inactivating the cell
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(Turnberg, 1996). Temperatures in the unit exceed 90 C. Factors affecting the microwave treatment of
medical waste include the frequency and wavelength of irradiation, the duration of exposure, moisture
content of the waste material, process temperature, and the mixing of the waste during treatment.
Microwave irradiation can treat most medical wastes with the exception of cytotoxic, haz-
ardous, or radioactive wastes. Contaminated animal carcasses, body parts, and human organs are
excluded from treatment by microwave irradiation for aesthetic reasons.
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Thermally resistant species such as B. subtilis (globigii) ATCC 9372 (10 ) may be used for ver-
ification of microbial inactivation. Dried spores are placed in a steam-permeable container and added
to the waste stream after the waste is ground and sprayed with steam before exposure to microwave
irradiation. The microwave unit is operated under routine conditions. At the conclusion of the cycle
the test strips containing the organisms should be inoculated into soybean–casein digest broth
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medium and incubated for at least 48 h. B. subtilis should be cultured at 30 C. At the end of the incu-
bation period the media should be examined for turbidity as a sign of bacterial growth. Any growth
should be cultured onto appropriate media to confirm the identity of the organism (RTI, 1993).

REFERENCES

American Hospital Association, An Ounce of Prevention: Waste Reduction Strategies for Health Care
Facilities, American Society for Health Care Environmental Services of the American Hospital
Association, Chicago, IL, 1993.
Block, S. (Ed.), Disinfection, Sterilization, and Preservation, 4th ed., Lea and Fibiger, Philadelphia, 1977.
Centers for Disease Control, Guideline for Handwashing and Hospital Environmental Control, NTIS PB85-
923404, Washington, DC, 1985.
Code of Federal Regulations Vol 40 Part 259, Standards for the Tracking and Management of Medical Waste,
U.S. Government Printing Office, Washington, DC, 2002.
Cole, E.C. Application of Disinfection and Sterilization to Infectious Waste Management, Proceedings of
Strategies for Improved Chemical and Biological Waste Management for Hospitals and Clinical
Laboratories, North Carolina Board of Science and Technology, Raleigh, NC, 1987.