Burns & McDonnell conducted a grazing study for a manufacturing facility in eastern Kansas. Portions of the facility are leased for cattle grazing and hay production. The study was undertaken to determine whether contamination from previously active portions of the facility had impacted areas leased for agricultural use. The possible contamination of cattle through the ingestion of contaminated soil, vegetation and/or water could complete an important indirect human exposure pathway, dietary consumption of beef.
- Grazing study
- Risk assessment
Work included developing a statistically appropriate sampling strategy; collecting soil, surface water, sediment and vegetation samples from each of three study areas within the facility boundaries; and evaluating the potential for human health risks resulting from consumption of potentially contaminated beef. Laboratory analyses were performed for dioxins, furans, polychlorinated biphenyls (PCBs), pesticides, polycyclic aromatic hydrocarbons (PAHs) and metals.
To determine the chemicals of potential concern for each study area, analytical data from all three study areas were screened. As a first-tier screening effort, concentrations of chemicals detected at the site were compared to site-specific background levels. For chemicals exceeding background, the data were then compared to calculated risk-based screening levels. Using modeled vegetation and beef biotransfer factors, screening levels were back-calculated from acceptable cancer risk and noncancer hazard quotients to allowable concentrations in soil, surface water and vegetation. Dioxins, furans, PCBs, pesticides and metals remained as chemicals of potential concern in the risk assessment.
Risk assessments were then conducted in each sampling area to determine the human health risks associated with the area-specific chemicals of potential concern. The potential exposure scenario under consideration was consumers of beef from cattle grazed at the site. Analytical data from soil and vegetation were used to model estimated chemical concentrations in beef.
Because of the high toxicity associated with very low levels of dioxins, the risk characterization indicated human health risk from dioxins in excess of the Environmental Protection Agency (EPA) acceptable level. As a result of project negotiations, EPA and the state of Kansas acknowledged the ubiquitous presence of dioxins at background levels that can produce calculated health risk in excess of EPA acceptable levels. Regulatory acceptance of background levels of dioxins below which remediation would not be necessary reduced the level of remedial action potentially required at the site.