The US Environmental Protection Agency has published new default assumptions for TSCA chemical assessments, providing laboratories with clearer insight into how the agency models environmental releases and worker exposure when reviewing new chemicals. These EPA default values are numeric inputs applied when chemical-specific data are unavailable or unverified. Their publication offers laboratories, chemical manufacturers, and EHS teams greater transparency into chemical exposure modeling under TSCA section 5. It may help reduce submission delays caused by incomplete or misaligned data packages.
Because many research laboratories contribute to regulatory submissions, support chemical characterization, or manage new substance workflows, EPA’s new reference guide delivers practical value for compliance planning and internal risk evaluation.
How EPA default values support new chemical reviews
EPA uses default assumptions to estimate workplace exposures and environmental releases when applicants do not provide substantiated data. These EPA default values cover areas such as process equipment residue, container types, cleaning practices, and potential release points throughout a chemical’s lifecycle. Under TSCA chemical assessments, these assumptions help standardize chemical exposure modeling and ensure that chemicals are reviewed consistently across sectors.
The new guide draws on three established sources:
- The Chemical Screening Tool for Exposures and Environmental Releases (ChemSTEER)
- EPA’s Generic Scenarios Documents
- The Organisation for Economic Co-operation and Development’s Emission Scenario Documents
EPA is hosting the resource in the New Chemicals Division Reference Library, where it will be updated as the agency incorporates new industry data. EPA notes that submitting higher-quality information aligned with these assumptions may reduce rework and improve review efficiency for laboratories and manufacturers involved in TSCA submissions.
What the default values mean for laboratory operations
Labs that support early-stage chemical research or regulatory submissions may find the new assumptions helpful for modeling their own workflows. For example, understanding the equipment-residue assumptions used in TSCA chemical assessments allows EHS teams to compare internal practices with the agency’s modeled expectations. Similarly, clarifying chemical exposure modeling inputs—such as transfer losses, container handling, and cleaning processes—may help labs evaluate engineering controls or identify where additional data could strengthen a regulatory filing.
Because these EPA default values represent generalized scenarios, laboratories with specialized or nonstandard processes may choose to submit representative data to help EPA refine future iterations of the guide.
How lab managers can use this information
For lab managers, the newly released assumptions provide a practical reference for aligning operations with regulatory expectations. Teams responsible for documentation or data generation can tailor submissions to match EPA’s modeling inputs, reducing the likelihood of delays. EHS managers can use the assumptions to proactively evaluate exposure risks, ventilation requirements, or waste-handling procedures.
When partnering with chemical manufacturers, shared visibility into TSCA chemical assessments and the underlying EPA default values supports more coordinated data development and reduces uncertainty during joint submissions. As EPA continues to update the guide, labs have an opportunity to provide operational insights that shape the future of chemical exposure modeling.
This article was created with the assistance of Generative AI and has undergone editorial review before publishing.
