On July 2, 2021, the U.S. Environmental Protection Agency (EPA) announced it is taking action to alleviate a supply-chain issue facing the pesticide industry. EPA stated that it is allowing registrants of non-antimicrobial pesticide products to substitute some combination of pre-approved alternate inert ingredients for inert ingredients derived from propylene oxide feedstocks that are in limited supply due to weather events that occurred in the U.S. Gulf Coast area in February 2021. EPA stated that it is allowing these substitutions even in cases where propylene glycol is added to the formulation or is part of a brand-name mixture in which the full composition is known to the registrant.

The pre-approved alternates are glycerin (Chemical Abstracts Service Registry Number (CAS RN) 56-81-5); diethylene glycol (CAS RN 111-46-6); ethylene glycol (CAS RN 107-21-1); and 1,3-propanediol (CAS RN 504-63-2).

EPA emphasizes that this action, known as “Propylene Glycol Phase 2 -- ‘Not In-Kind’ Substitution Mechanism,” relates only to non-antimicrobial pesticide products and that EPA will handle “not in-kind” substitutions for antimicrobial pesticide products on a case-by-case basis.

In April 2021, EPA implemented “Propylene Glycol Phase 1 -- ‘In-Kind’ Substitution Mechanism” to allow certain in-kind substitutions to address propylene glycol supply-chain shortages.

These actions require registrants to self-certify that the substitute inert ingredients serve the same function in the product as propylene glycol and that the change will not impact either the validity of any product-specific data submitted in support of the registration or the product’s acute toxicity category or physical/chemical characteristics in a way that would require label modifications. Registrants must also certify that the substitution will not affect the product’s fitness for its intended purposes in terms of efficacy, phytotoxicity, or any other factor.

This action is time limited, extending to December 31, 2021. Any registrants who wish to make the substitution permanent will have to go through the standard amendment process outlined in Pesticide Registration Notice (PRN) 98-10.