Advanced Risk Assessment Approaches for TSCA

The Environmental Protection Agency (EPA) is initiating new risk assessments on prioritized industrial chemicals using previously unpublished data. This may cause substantial impact on manufacturers, importers, and users, with the possibility of eliminating new uses or disallowing/limiting existing uses.

Under the EPA’s Toxic Substances Control Act (TSCA), the EPA finalized scoping documents for 20 priority substances, and will soon have a data call for these as well as 30 more flame-retardant chemicals to address the unpublished data.

The TSCA risk assessments will address toxicity according to occupational exposure or via environmental release. Much data are already available for these chemicals, and many chemicals have existing EPA risk assessments completed. The new risk assessments will likely include new approaches developed since the previous assessments were completed.

New advances in assessment include concepts like the National Academies of Science Toxicity Pathway approach, development of an Adverse Outcome Pathway and in silico prediction of toxicity via computational structure-activity relationships. The EPA is advancing methods to complete in vitro to in vivo extrapolation, bringing decisions based on in vitro findings pertinent to regulation closer than ever before.

The impending risk assessments may include unpublished data, and it is imperative that these data be interpreted in the context of the most recent guidance. Due to the advances in risk assessments, and because new data may be released during the development of the risk assessments, and because external peer reviewers may not be fully educated in the advancements in risk assessment methodology, the a priori development and peer review of the interpretations of previously unpublished data may provide valuable standing.

This is especially important in light of EPA’s June 30 release of their “Whole Chemical Approach,” which EPA will use to make risk determinations at the level of the chemical, not at the level of individual specified uses.  This may cause the withdrawal of some of the EPA’s recent re-evaluation of risks under TSCA. Under the Whole Chemical Approach, risks associated with some conditions of use may drive the risk assessment, resulting in restriction or disallowance of the chemical in general, even if other conditions of use are not associated with increased risk. This means exposure and chemical hazard assessments are important for each and every usage of the priority chemicals, underscoring the value of previously unpublished data, and data for which a peer review has not.

There have also been advances made in risk assessment methods since the previous assessments. These include mode of action analysis, animal to human extrapolation methods, physiologically based pharmacokinetic modeling, the use of tissue dose as critical measure of exposure, development of data-derived extrapolation factors, and analysis of the human relevance of the chemical mode of action.  These approaches can demonstrate that some conditions of use will not result in tissue or organ exposure in humans high enough to cause the toxicities seen in experimental animals.

If you have concerns about these new risk assessments, CTEH can help. Our toxicologists and risk assessors are ready to answer your client’s questions, discuss advanced risk assessment approaches, and plan for peer reviews of data-informed conclusions based on the most recently available EPA risk assessment policies.