Agricultural Land Application of Biosolids in Virginia: Risks and Concerns
Author: G.K. Evanylo, Extension Specialist, Department of Crop and Soil Environmental Sciences, Virginia Tech
Publication Number 452-304, posted August 1999
When state scientists are misled by federal regulators, can they be blamed for misleading legislators?
Why would a state scientist mislabel toxic pollutants as simple trace elements?
Human health and environmental risks
Risk assessment approach to regulation
Quality standards and limits for pollutants in biosolids were developed from extensive environmental risk assessments
conducted by scientists at the U.S. EPA and the U.S. Department of Agriculture. EPA used a rigorously reviewed
methodology that they developed specifically for conducting the assessment (National Academy of Sciences, 1983; U.S.
EPA, 1986). The goal of the risk assessment was to protect a person, animal or plant that is highly and continuously
exposed to pollutants in biosolids. The rationale for this goal is that the general population would be protected if the
regulations were developed to protect highly exposed individuals.
The risk assessment process was the most comprehensive analysis of its kind ever undertaken by the EPA. The
approach has since been applied to other materials, such as municipal solid waste compost. The resultant Part 503
Rule was designed to provide "reasonable worst-case," not absolute, protection to human health and the environment.
Part 503 risk assessment
The initial task of the 10-year risk assessment process was to establish a range of concentrations for trace elements
and organic compounds that had the greatest potential for harm based on known human, animal and plant toxicities.
Maximum safe accumulations for the chemical constituents in soil were established from the most limiting of 14 pathways
of exposure (Table 1), which included risks posed to human health, plant toxicity and uptake, effects on livestock or
wildlife, and water quality impacts. A total of 200 chemical constituents were screened by EPA, and 50 of these were
selected for further evaluation, using the criteria above and the availability of data for a preliminary risk assessment.
Twenty-three of the 50 constituents were identified as warranting consideration for regulation based on the risk
assessment. No regulatory limits were set for the 13 trace organic compounds in this group because the EPA risk
assessment showed that the safe levels were considerably higher than the observed concentrations in biosolids. The
503 rule was then limited to ten trace elements (arsenic, cadmium, chromium, copper, lead mercury, molybdenum,
nickel, selenium, and zinc). Chromium was subsequently dropped on a court challenge because the risk assessment
had shown a very low risk level for this metal.
In Leather Industries of America, Inc et al v. EPA suit, EPA told the court it only had a few pot studies and it had no
confidence in them. In "A Guide to the Biosolids Risk Assessments for the EPA Part 503 Rule" in
September 1995 which acknowledged that the risk assessment was a sham. The only cancer risk
assessment was based on the organics that were proposed for regulation, but were never
regulated. According to the writers, EPA's John Walker, Linda Stien, Robert Southworth and James Ryan, as well as
USDA's Rufus Chaney, "--the Part 503 metals were considered noncarcinogens (they do not cause or induce
cancer) for the exposure pathways evaluated." (pp. 110-11).
That might be true if you didn't inhale any of the carcinogens near a sludge site!