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Engineering Controls Database

Control of Biological, Chemical, and Safety Hazards in Medical Waste Treatment Facilities

It has been estimated (219-05-E) that 3.5 million tons of medical wastes are generated each year in the United States. The medical waste treatment processes consist of untreated waste handling, waste treatment, and treated waste handling. It is estimated that more than 10,000 workers are involved in processing medical waste on site at healthcare establishments and off site at commercial treatment facilities.
Workers in medical waste treatment facilities may be exposed to biological hazards (e.g., HIV, TB, HBV, and HVC) through sprays or splashes that contact the skin or mucous membrane as well as cause exposure through inhalation. Workers may also be exposed to hazardous microorganisms through needlestick and other sharps injuries. In addition to biological hazards, medical waste treatment workers may be exposed to radioactive materials, noise, chemicals, heat stress, ergonomic problems and electrical and other safety hazards.
Under contract, NIOSH conducted a number of field studies to examine the medical waste treatment process including untreated waste handling, treatment, and treated waste handling. Currently available infection systems were identified and evaluated with regards to safety, aerosol, chemical, blood and microbial hazards and the use of engineering controls in controlling exposures. Originally, two fully-developed medical waste treatment technological systems were identified and evaluated (steam autoclave and microwave) and one developing technology (pyrolysis) [219-05-D]. A fourth system was later identified and covered in a separate report: Rotoclave® medical waste treatment facility (219-05-F).

Pyrolysis: Pyrolysis units treat medical waste by pyrolizing waste in a controlled temperature and environment. The units may operate up to 5100°C (9500°F) with a second oxidation chamber operating over 9820°C (18000°F). Pyrolysis reduces most medical waste to gases leaving a small amount of dust and debris. Metals and ceramics will not be reduced in size but will be sanitized by the high temperature in the treatment unit. All remaining solid waste is collected ion a dust bin and emptied as needed.

Steam Autoclave: The steam autoclave treatment combines moisture, heat and pressure to inactivate microorganisms. The process has been used for sterilizing medical equipment in hospitals and is well documented. Hospital autoclaves normally operate at a temperature of 1210°C (2500°F) and a pressure of 15 psi for gravity displacement units. A typical laboratory autoclave used in a hospital normally can teat about 20 lbs in one cycle. Prevacuum units, such as the ones used for on-site medical waste treatment operate at 132-1380°C (270-2800°F) and 30 psi, and can treat approximately 100 lbs per cycle. The off-site commercial autoclaves operate at 1600°C (3200°F) and 80-85 psi, and can treat about 3,000 lbs per cycle.

Microwave: Microwave treatment uses nonionizing radiation to heat medical waste to produce thermal inactivation of microorganisms. Typically, waste is fed by continuous batch mode into a grinding chamber where is sprayed with steam and mechanically shredded. The waste is then treated with additional steam as it slowly moves via a transport auger under a series of microwave units. The internal temperature of the waste maintained 950°C (2030°F). Following microwave exposure, the treated waste is conveyed via an auger tube to a dumpster or compactor. The treated waste may then be hauled to an approved landfill. The individual units are designed to treat medical waste at rates from 220 to 900 lbs/hr.

Rotoclave® : The Rotoclave® technology combines steam autoclaving of the waste while appropriately rotating it so that the contents of the waste containers are uniformly exposed to the steam. Following the treatment cycle, the waist is moved from the unit by conveyer to a solid waste shredder and then through a grinder for finial disposition to a landfill.
219-03; 219-05-A; 219-05-B; 219-05-C; 219-05-D; 219-05-E; 219-05-F; 219-07;
medical waste treatment
medical waste treatment facilities
medical-waste workers
It is assumed that all of the engineering controls used to process medical waste noted above adequately sterilize the waste. The studies were conducted in the early to mid-1990s and it is also assumed that advances have been made in reducing the hazards noted in the NIOSH evaluations.

The NIOSH study was concerned with an evaluation of the hazards associated with the use of the processes described above noted particularly safety and blood exposure hazards. Most of the safety issues were similar to those that might be found in other industrial, non-medical waste facilities. For example, the following safety hazards were noted at one of more facilities:

• Required warning signs missing;
• Flammable chemicals found in non-flammable cabinets;
• Electrical hazards and code violations;
• Floors were wet, and potentially slippery, from liquid spills;
• Extensive manual labor led to concerns over worker back and muscular strain;
• Workers were required to enter confined areas.

These safety issues indicated a need for medical waste treatment facilities to periodically review their procedures and processes to ensure they are in compliance with Occupational Safety and Health Administration (OSHA) regulations.

As far as hazards related directly to the medical waste, the most significant came from liquid spills and splashes and from exposure to sharps. All requirements of the OSHA Bloodborne Pathogens Standard should be followed. The following practices were also emphasized:

• Engineering controls should be used to minimize or eliminate the manual dumping of regulated waste whenever possible;
• Face shields and goggles should be worn if there is a potential for splash;
• Clean sets of protective clothing including footwear should be provided daily to workers who have direct contact with untreated medical waste – the clothing should remain at the worksite for disposal or cleaning to reduce the potential for transmission of infectious agents to workers’ homes.