Human Health & Ecological Risk Assessments

Forest managers frequently make decisions regarding the use of pesticides on forest lands. These decisions must be based not only on the effectiveness of these tools, but also on an understanding of the risks associated with their use. For the pesticides commonly used by the Forest Service in its management activities, Human Health and Ecological Risk Assessments (HERAs) are prepared. In these documents, the process of risk assessment is used to quantitatively evaluate the probability (i.e. risk) that a pesticide use might pose harm to humans or other species in the environment. It is the same assessment process used for regulation of allowable residues of pesticides in food, as well as safety evaluations of medicines, cosmetics, and other chemicals. The Forest Service incorporates relevant information from the HERA into environmental assessment documents prepared for pesticide projects, and are used to guide decision-making and to disclose to the public potential environmental effects.

Risk is defined as the likelihood that an effect (injury, disease, death or environmental damage) may result from a specific set of circumstances. It can be expressed in quantitative or qualitative terms. While all human activities carry some degree of risk, some risks are known with a relatively high degree of accuracy, because data have been collected on the historical occurrence of related problems (i.e. lung cancer caused by smoking, auto accidents caused by alcohol impairment, and fatalities resulting from airplane travel). For several reasons, risks associated with activities including exposure to chemicals such as pesticides cannot be so readily determined. The process of risk assessment helps evaluate the risks resulting from these situations. 

When evaluating risks from the use of pesticides proposed in a NEPA planning document, reliance on U.S. EPA’s pesticide registration process as the sole demonstration of safety is insufficient. The Forest Service and Bureau of Land Management were involved in court cases in the early 1980’s that specifically addressed this question (principally Save Our Ecosystems v. Clark, 747 F.2d 1240, 1248 (9th Circuit, 1984) and Southern Oregon Citizens v. Clark, 720 F. 2d 1475, 1480 (9th Cir. 1983)). These court decisions and others affirmed that although the Forest Service can use U.S. EPA toxicology data, it is still required to do an independent assessment of the safety of pesticides rather than relying on FIFRA registration alone. The Courts have also found that FIFRA does not require the same examination of impacts that the Forest Service is required to undertake under NEPA. Further, Forest Service assessments consider data collected from both published scientific literature and data submitted to U.S. EPA to support FIFRA product registration, whereas U.S. EPA utilizes the latter data only. The U.S. EPA also considers many forestry pesticide uses to be minor. Thus, the project-specific application rates, spectrum of target and non-target organisms, and specialized exposure scenarios evaluated by the Forest Service are frequently not evaluated by U.S. EPA in its generalized registration assessments.

Risk assessment documents and worksheets have been developed for a number of pesticides that are used by the Forest Service. These are available on-line at this website. Existing risk assessments may be used in lieu of a project-specific risk assessment. 

For further detail of the Forest Service risk assessment process for pesticides and how it is used, please consult “Preparation of Environmental Documentation and Risk Assessments”, available from the following on-line selections.