TSCA SACC Review of EPA's Fenceline Screening Level Approach

Report raises concerns over exposure pathways & potential use of screening methods for regulation

On May 19, the Toxic Substances Control Act (TSCA) Science Advisory Committee on Chemicals (SACC) released its final report on the U.S. Environmental Protection Agency's (EPA's) "Draft TSCA Screening Level Approach for Assessing Ambient Air and Water Exposures to Fenceline Communities Version 1.0." SACC concluded that, while the screening level approach may be protective for some exposure pathways, "it may not be protective overall because potential key exposure pathways are excluded."

SACC criticized the lack of consideration for cumulative exposures, multiple source exposures, and aggregate exposures. The 74-page report also asked for consideration of occupational exposures for individuals that both work at and live near a facility and outlined a number of recommended refinements.

EPA developed the draft screening level approach as part of the continuing implementation of TSCA as amended by the Frank R. Lautenberg Chemical Safety for the 21st Century Act of 2016. The guidance outlined a framework for addressing exposures to residents who live near the so-called "fenceline" of industrial facilities.

The motivation for the guidelines was that the prior administration, in the first 10 chemical risk evaluations conducted under the 2016 TSCA amendments, did not assess air, water, or disposal exposures to the general population.

At the outset of the SACC meeting, EPA's Assistant Administrator for the Office of Chemical Safety and Pollution Prevention, Michal Freedhoff, warned that lengthy revisions could delay urgent regulatory needs from the first 10 evaluations, but from a broader implementation perspective, most SACC members found the screening methodology insufficient to exclude exposure scenarios as presenting risk. Furthermore, EPA described scenarios where the screening level methodology could be used to regulate exposures without additional analysis.

Under the classic risk assessment paradigm, a screening methodology serves to exclude certain exposure scenarios as causing risk by using methodologies that tend to overestimate true risk. In other words, the method "screens" out risks clearly not of concern. If a risk is identified, a more refined analysis is conducted to estimate risks more accurately. Using a screening methodology to regulate without further refinement creates scenarios for potential over-regulation and unnecessary remediation.

How Exponent can help

Exponent scientists have a long history of solving complicated problems and communicating the results effectively. We can assist clients with the siting and installation of fenceline monitoring systems and the interpretation of the data collected. Our scientists are knowledgeable in meteorology, air transport, and the industrial processes that cause emissions. We can help develop a plan for mitigating impacts and effectively engaging with the community to communicate the results.