Because you can usually smell biosolids being applied on a farm, some people have wondered whether disease-causing organisms left over from the wastewater treatment process could be spread through the air to humans or animals. There have even been unsubstantiated allegations of illness after land application.

However, there are no scientifically documented cases of illnesses caused by biosolids. There have been a number of scientific studies that demonstrate the difficulty of transmitting biosolids-related diseases through the air. Current federal and state regulations, combined with the implementation of land application best management practices, make it even more unlikely that diseases can be transmitted from biosolids.

Research conducted by Paul Chrostowki & Sarah Foster, Odor Perception and Health Effects, 76th Annual Water Environment Federation Technical Exhibition and Conference Workshop (2003). A 2004 literature review of the health effects of odors from municipal wastewater operations presented reasons to conclude that odors do not cause illness: (1) odors do not cause signs of illness in healthy individuals; (2) odor acceptability varies with circumstances of exposure and the meaning people associate with the exposure; (3) below toxic levels of exposure, symptoms associated with odors involve no pathology; (4) symptoms are reduced almost immediately when the source of an odor is removed; and (5) nonphysical variables, such as anxiety and stress, seem to mediate symptoms from odors.

Most odors in biosolids are caused by sulfur compounds that only cause toxic effects in concentrations vastly greater than that which triggers a smell. Further, gases with a possible toxic effect are not present in biosolids in concentrations that would endanger nearby residents. Although there has not been any observed health risks, site and process specific stabilization or vector attraction reduction criteria are essential. Accordingly, local agencies in Virginia have invested significant resources for improved odor control.