Gradient News Alert: TSCA Risk Evaluation Update

News & Events

June 5, 2020

Ten TSCA draft risk evaluations have been released, with several still open for public comment.


TSCA/LCSA, high-priority chemicals,

US EPA’s risk evaluation process

TSCA Chemical Risk Evaluations: What We Have Learned and What to Expect


Ten TSCA draft risk evaluations have been released, with several still open for public comment.  Draft scopes of work for the next 20 high-priority chemicals have been released and are all open for comment.

In December 2019, US EPA designated 20 chemicals as high priority for risk evaluation under the Lautenberg Chemical Safety for the 21st Century Act (LCSA) amendments to the Toxic Substances Control Act (TSCA).  Draft scopes of work for these chemicals were published in April 2020.  The scopes describe the chemical uses that will be evaluated for workers and consumers, the exposure pathways associated with those uses, and how human and environmental risks will generally be evaluated for the full lifecycle of the chemicals.


Although the scopes do not provide detailed discussions of how the risk evaluations will be conducted, we have some understanding of what to expect based on the draft risk evaluations that have recently been published on the first 10 chemicals evaluated under the new TSCA.  Risk evaluations for these chemicals are due to be finalized before the end of 2020.  Some notable features are listed below.

  • A lifetime cancer risk of 10-4 (1 in 10,000) is considered acceptable for workers (including occupational non-users [ONUs]), with consideration of personal protective equipment (PPE) in a subset of the risk calculations.
  • Only acute risk evaluations were conducted (including no cancer risk evaluation) for a number of consumer scenarios (e.g., for trichloroethylene and perchloroethylene).
  • Data from manufacturers have been considered in the previous risk evaluations, with the 95th percentile applied to high-end risk estimates and the 50th percentile applied to central-tendency risk estimates. However, US EPA has used the 50th percentile exposure estimates as worst-case estimates for some ONU scenarios, which may be highly conservative for some ONUs.
  • Exposure models were applied to estimate dermal exposures for worker scenarios for several of the chemicals.  It is noteworthy that the dermal pathway, even considering dermal PPE, contributes to an unreasonable risk estimate for several chemicals.
  • Toxicity assessments have been conducted for some chemicals (e.g., asbestos), but for others (e.g., perchloroethylene, carbon tetrachloride), US EPA applied values derived in the most recent Integrated Risk Information System (IRIS) toxicity assessments.  See our recent comments submitted on the asbestos assessment.

Comments on the scopes for the upcoming 20 risk evaluations provide interested parties with the opportunity to submit chemical-specific information that may be relevant to US EPA’s risk evaluation process, such as updated chemical toxicity assessments, worker (or ONU) air monitoring data, PPE information, or other exposure or process information that may be useful for US EPA to consider. Comments are due on May 26th for the scopes of 13 chemicals, and on June 8th for the other 7 chemicals.  The final scopes are scheduled to be published by December 2020, and draft risk evaluations for these chemicals are scheduled to be published by December 2022.


Gradient scientists have expertise in conducting chemical hazard assessments, and environmental/ecological and human health risk evaluations, including expertise in exposure modeling for workers, consumers, and the general population.  Please let us know if you need support in understanding your company’s data needs or in preparing comments so that all of the information relevant to your chemical is available to US EPA.

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