As part of the US Environmental Protection Agency's (EPA) commitment to re-evaluate policies and practices under the Toxic Substances Control Act's (TSCA) New Chemicals Program to ensure compliance with statutory requirements and the Biden-Harris Administration's executive orders and directives. The agency has changed its policy to stop the use of exposure modeling thresholds for assessing the health and environmental risks of new substances under TSCA.

The policy of employing exposure-modeling thresholds was introduced in the mid-1990s to focus limited resources on exposures with the greatest potential for harm to human health and the environment. After evaluating over a thousand pre-manufacture notices each year, the Program discovered that when a chemical is emitted at relatively small levels into the air or from landfills. Because the risks posed by such releases are minor and unlikely to be unjustified, it was decided to impose exposure release criteria below which no programmatic efforts will be invested to assess associated risks. It has gotten less difficult to do these computations since then, thanks in part to modeling automation.

The EPA is working to have a better understanding of the potential dangers posed by chemical discharges in overburdened and vulnerable areas. By removing modeling thresholds from novel chemical reviews, the EPA and overloaded and vulnerable areas will acquire a better understanding of these potential risks. Completing the modeling for all potential exposures to groundwater caused by air releases and landfill releases will provide a more complete picture of the potential threats to these areas.

The New Chemicals Program will make minor adjustments to the coding in our New Chemical Review program eliminate the thresholds, as well as alter standard operating procedures and training materials for exposure and human health risk assessors, to incorporate this change. The EPA will implement this policy change as soon as possible. Despite the resource constraints that the EPA is currently experiencing in the TSCA program, the agency anticipates that this will have little impact on the amount of time it takes to complete new chemical reviews and that the benefits gained from a more comprehensive accounting of all potential air and water releases will help ensure that any necessary safeguards are in place before a new chemical can be introduced to the market.


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