Three workers fall sick at waste-disposal plant
Investigation uncovers lack of decontamination
Lewis County, Washington, a bucolic community of 66,000, sees so few cases of tuberculosis that public health officials don’t even bother to calculate TB incidence rates there. That’s why they were puzzled when first one, then two, then three workers at a county biomedical waste- disposal facility came down with active TB.
Tests showed that an isolate from one patient was resistant to a single frontline drug; a second patient was found to have multidrug-resistant TB. That second discovery "was a really big flag, since we simply don’t have MDR-TB in the Northwest to any appreciable extent," says Kammy Johnson, DVM, MS, PhD, an epidemiological investigative service officer assigned to the Washington state health department. "Even though biomedical waste had never been reported as an occupational hazard, that’s when we knew we were dealing with something other than person-to-person transmission."
Skin tests on other workers at the facility turned up 13 positive reactors as well — an ambiguous finding, Johnson notes, since it’s impossible to say whether the finding reflects the workers’ exposure to infectious wastes or to an infectious co-worker.
As the outbreak investigation proceeded, a study of how laboratories in the state licensed to handle TB cultures uncovered more news: Nearly half the labs in the state licensed to handle TB (a total of 20 out of 44) were shipping their TB stocks and cultures off site without first decontaminating them.
NIOSH inspectors called in
In an attempt to pinpoint how the exposures might have occurred, the state called in the National Institute of Occupational Safety and Health (NIOSH) to inspect the waste-disposal facility. The findings, though indeterminate, were enlightening.
Waste at the facility is packed into 40- to 60-gallon containers, inspectors found, which workers unload by hand. The containers are emptied into processing equipment, where the waste is shredded, blown into another part of the system, and then heat-treated by macrowaves.
The shredding and blowing portions of the process take place under negative pressure. Even so, NIOSH inspectors found instances in which, Johnson says, "they felt it was plausible" that workers may have been exposed to airborne pathogens, perhaps by coming into contact with air that had leaked from the system, handling contaminated equipment, or entering the facility before it had been decontaminated.
Legally, the only recourse available to the state health department was to tell the Lewis County facility to begin requiring that workers don full-face respirators before entering the processing facility.
Shredding and blowing wastes are not unusual in such facilities, experts say. "These places are all over the country, and they operate on the same principle: They shred the waste first," says Wayne Turnberg, public health adviser to the state health department. Many states demand that biomedical waste be ground before it’s heated, for the simple reason that landfill operators don’t like looking at it in its unaltered form, he adds.
Theoretically, disposal facilities could opt for other technologies less apt to produce airborne suspensions of particles. "There’s one technology that consists of using a strong base, such as sodium hydroxide, that’s used a lot in veterinary settings," Turnberg says. "It’s like something out of a horror show — the sodium hydroxide can reduce an entire horse carcass to basically nothing."
But one expert in infectious waste exposure says the real hazards to workers at such disposal facilities don’t result from the processing itself, but from workers’ handling of wastes as they are loaded and unloaded (see cover story). At such points in the process, "there’s generally a lot of blood and other fluids splattering around," says Turnberg. "If it gets sloppy, it can become very risky."
Despite outbreak, no bills passed
Following the Lewis County outbreak, a handful of legislative measures were proposed in Washington state aimed at protecting workers at waste-disposal facilities. Among them were bills that would have required:
• facilities generating biomedical wastes (such as laboratories) to decontaminate them before sending them off-site;
• the state to review and approve new "alternative-waste" technologies such as the patented shred-and-blow method used at the Lewis County facility;
• waste-treatment facilities to have a hazard-analysis control plan in place;
• counties to address waste-disposal problems on a local basis.
Not one of the proposed measures passed. The reason? "Generators of the waste — hospitals, clinics, doctors’ offices — all have an economic and operational stake in how they get rid of this stuff," says Brian Peyton, assistant director for legislative and constituent relations for the state health department. "Plus, risk to the public health simply wasn’t perceived as great as the risk posed by other public health problems. That’s just the way these things work."
Ironically, many waste generators have autoclaves and theoretically could treat their wastes on site, notes Turnberg. "But there would be a capital expense to the labs; the process [of shipping wastes off-site] couldn’t be easily reversed. In a sense, the cat’s already out of the bag."
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