Exposure assessment of employees land-applying biosolids.
American Industrial Hygiene Conference and Exposition, May 20-25, 2000, Orlando, Florida. Fairfax, VA: American Industrial Hygiene Association, 2000 May; :42
In response to a management request for assistance, NIOSH investigators conducted an evaluation of worker exposure during the land application of biosolids (treated sewage sludge). At the wastewater plant, biosolids were loaded into large dump trucks with a front-end loader, transported to a farm field, and dumped. The biosolids were then loaded into a side discharge sludge spreader and sprayed on the field. A tractor was used to disk the sludge into the soil. All five employees reported at least one episode of gastrointestinal illness occurring soon after performing this work. Environmental monitoring was conducted, which included the collection of area and/or personal breathing zone air samples for culturable bacteria, endotoxins, volatile organic compounds (VOCs), and metals. Bulk samples of sewage sludge were analyzed for coliform bacteria. The geometric mean bacterial area air concentrations ranged from 412 to 2356 colony forming units per cubic meter of air (CFU/m3). All bacterial genera identified in these samples are associated with outdoor environments or mammals; some are considered opportunistic human pathogens. Airborne endotoxin levels ranged from 20 to 39 endotoxin units per cubic meter (EU/m3), which are similar or below levels found in wastewater treatment plants. The geometric mean concentrations of coliform bacteria and Escherichia coli in the bulk sewage sludge samples were 2.7 x lQ4 CFU and 2.2 x IQ4 CFU per gram of sample, respectively. The concentrations of metals and VOCs, including toluene, were low and well below current occupational exposure limits. The nature and timing of the employees' reported symptoms suggest occupational exposure by direct contact with the biosolids as a probable cause of these symptoms. Recommendations were made for minimizing the growth of microorganisms during the storage process, increasing hand washing, adding filtration to the air-conditioning units on the tractor and front-end loaders, and improving the use of personal protective equipment.
Exposure-assessment; Employee-exposure; Employee-health; Environmental-exposure; Environmental-hazards; Environmental-health-monitoring; Sewage-treatment; Hazardous-materials; Waste-disposal; Soil-analysis; Soil-bacteria; Soil-sampling; Farmers; Work-operations; Gastrointestinal-system-disorders; Air-sampling; Breathing-zone; Sampling; Bacteria; Endotoxins; Volatiles; Organic-compounds; Metals; Outdoors; Pathogens; Microorganisms; Personal-protective-equipment; Exposure-limits; Materials-handling; Materials-storage; Materials-transport
American Industrial Hygiene Conference and Exposition, May 20-25, 2000, Orlando, Florida