EPA Issues Proposed Interim Registration Review Decision to Require New Risk Mitigation Measures for Chlorpyrifos

On December 7, 2020, the U.S. Environmental Protection Agency (EPA) issued for comment the Proposed Interim Decision (PID) for chlorpyrifos.  85 Fed. Reg. 78849.  EPA announced it is proposing new risk mitigation measures to address potential human and environmental risks identified in EPA’s September 2020 draft risk assessments.  The PID proposes the following measures:

• Label amendments limiting application to address potential drinking water risks of concern.

• Additional personal protection equipment and application restrictions to address potential occupational handler risks of concern.

• Spray drift mitigation, in combination with the use limitations and application restrictions identified to address drinking water and occupational risks, to reduce exposure to non-target organisms.

EPA states that the PID presents proposed mitigation with the 10-fold (10x) Food Quality Protection Act (FQPA) safety factor, reflecting the uncertainties around doses that may cause pre- and post-natal neurodevelopmental effects.  Under FQPA, EPA evaluates new and existing pesticides to ensure they can be used with a reasonable certainty of no harm to infants, children, and adults.  EPA is required to consider the special susceptibility of children to pesticides by using an additional 10x safety factor unless adequate data are available to support a different factor.  EPA additionally included a FQPA factor of 1x to reflect the range of potential risk estimates of chlorpyrifos, as illustrated in the September 2020 draft risk assessments.

Comments on both the September 2020 draft risk assessments and the PID are due on or before February 5, 2021.  EPA states that by holding the comment period for both actions at the same time, the public has access to more information and can provide more informed, robust comments.  Comments can be submitted at EPA-HQ-OPP-2008-0850.

EPA announced that it will also consider the input and recommendations from the September 2020 Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA) Scientific Advisory Panel (SAP) meeting once it releases its report in December 2020.  Depending on the SAP’s conclusions, EPA may further revise the human health risk assessment. 

Commentary

The inclusion of both 1x and 10x calculations for the appropriate FQPA safety factor is unusual.  EPA states the final decision on the appropriate FQPA safety factor is partly dependent on any recommendations expected from the SAP meeting, which reviewed the “use of new approach methodologies (NAMs) to derive extrapolation factors and evaluate developmental neurotoxicity for human health risk assessment.”  This is part of a larger and longer evaluation of whether test methods that avoid using test animals can reliably substitute for current test guideline requirements, that is, whether it is appropriate to rely on in vitro test protocols to substitute for current in vivo testing protocols.

EPA’s articulation at this point in time of mitigation needed if the FQPA 10x safety factor is retained may indicate a prediction about the SAP’s likely recommendations.  It will be important to monitor developments on this issue closely.