MADISON, Wis., Oct. 29 (UPI) -- U.S. environmentalists say they've found there is only a low risk from aerosolized microorganisms involved in applying treated sewage sludge as a fertilizer.
Class B biosolids are sewage sludges that have been treated to contain fewer fecal coliforms. The U.S. Environmental Protection Agency estimates 6.3 million tons of Class B biosolids are generated in the United States each year.
Biosolids produced during municipal sewage treatment are most commonly applied to land as a fertilizer at agricultural sites throughout the United States, researchers said, and Class B biosolids, the principal type of biosolids applied to land, contain a variety of enteric pathogens.
The study by the Soil Science Society of America focused on levels of microorganisms in air immediately downwind of such land application operations and estimated occupational risks from aerosolized microorganisms.
The researchers said they determined risks of aerosol-borne infection for biosolids workers are generally low, at less than 1 percent to 2 percent a year. Overall, they said, occupational exposure to bioaerosols from biosolids appears to be less risky than similar exposures among wastewater treatment workers.
The report appears in the November-December issue of the Journal of Environmental Quality.
