Health hazard evaluation report: HETA-95-0198-2765, City of Springfield, Department of Public Works Composting Facility, Springfield, Missouri.
On March 27, 1995, the National Institute for Occupational Safety and Health (NIOSH) received a management request for a health hazard evaluation from the City of Springfield, Missouri, to assess any possible employee health effects from operation of the city’s composting facility. There were no indications that employees have or had any health problems associated with the compost operation. This request was prompted by the publication of the NIOSH Alert pertaining to Organic Dust Toxic Syndrome (ODTS). The City of Springfield has two separate composting operations. The first operation was located on a large asphalt pad (adjacent to the sewage treatment plant) and consisted of windrows of mixed sewage sludge and saw dust/wood chips which produced a "Class A" compost. The second site, also adjacent to the sewage treatment plant, was a more conventional composting operation where city residents disposed of their yard waste, the yard waste piled and turned as necessary to produce compost. The finished compost is available to city residents for their home use. Loading of the finished composted product is done by the residents in their own vehicles. During the three surveys conducted at these composting sites, work area air samples were collected for total dusts, ammonia , bioaerosols and endotoxins. Also, real-time monitoring of respirable dust was accomplished inside and outside of equipment used to turn the compost piles. Finally, bulk samples were collected of various compost products and analyzed for microorganisms. Overall, total dust concentrations ranged from Non-detectable (ND) to 22.5 milligrams per cubic meter of air (mg/m3), with the highest samples being located downwind from the sites. Bacteria concentrations ranged from ND to 6.02 x104 colony forming units per cubic meter of air (CFU/m3), with the highest concentrations measured during compost turning operations. The most predominant bacteria found on the samples was Bacillus. Fungi air samples ranged from ND to 2.7 x 105 CFU/m3, with the highest concentrations measured downwind of the green waste compost site. The predominant fungi identified on the samples was Aspergillus. Endotoxin results ranged from ND to 381 endotoxin units per cubic meter of air (EU/m3), with the highest levels measured during compost turning. Ammonia concentrations were measured as high as 20 ppm during compost turning operations. Samples collected indicate that the enclosed equipment cabs, when used properly by keeping the windows closed, can reduce worker exposures. However, these controls are relatively ineffective if the cab window are opened during composting handling operations. City residents were observed shoveling compost into their own vehicles, digging through the compost piles in search of finer material, shoveling hot or cooking compost with their bodies positioned into the steam rising from the piles, and loading their vehicles while in close proximity to end-loaders turning piles. Residents may be at a greater risk of developing ODTS than the city’s workers since they are most likely uninformed of the health effects of breathing organic dust, use no respiratory protection, or because of a pre-existing medical condition that may make them more susceptible. Since ODTS is not a widely recognized illness, the syndrome might be misdiagnosed by community physicians. The results from this health hazard evaluation have shown that enclosed machinery cabs on the equipment can reduce exposure when used properly by keeping the windows closed. Also, these results show that individuals in the general area of the composting pads or those not operating enclosed equipment, should stay upwind during turning operations. However, controlling exposures to city residents at the green waste composting site may pose a more difficult problem. Residents may be at a greater risk in developing ODTS since they are most likely uninformed of the health effects of breathing organic dust, use no respiratory protection, or because of a pre-existing medical condition that may make them more susceptible. Since ODTS is not a widely recognized illness, the syndrome might be improperly diagnosed by community physicians. Recommendations are provided.