EPA Exempts Oxirane Polymers from Pesticide Tolerance Restrictions
Published Date: 11/17/2025
Rule
Summary
The EPA just made it official: two special polymers used in pesticides don’t need a safety limit for leftover amounts on crops or animals. This means farmers and pesticide makers can use these ingredients more easily without worrying about strict residue rules. The new rule kicks in on November 17, 2025, and anyone who wants to object has until January 16, 2026 to speak up.
Analyzed Economic Effects
4 provisions identified: 2 benefits, 2 costs, 0 mixed.
No tolerance required for Polymer A
The EPA exempted oxirane, methyl-, polymer with oxirane, monobutyl ether (CAS 9038-95-3; Mn 800 Da) from the requirement of a tolerance when used as an inert ingredient (adjuvant, carrier, diluent, or solvent) on growing crops, raw agricultural commodities pre- and post-harvest, and on animals. The exemption is effective November 17, 2025, so pesticide makers and agricultural producers no longer need a numerical residue limit for this ingredient when used as allowed.
Polymer B limited to 10% in formulations
The EPA exempted oxirane, 2-methyl-, polymer with oxirane, monomethyl ether (CAS 9063-06-3; Mn 800 Da) from a tolerance only when it makes up not more than 10% of the final pesticide formulation. EPA will enforce this limit through the pesticide registration process under FIFRA and will not register any pesticide formulation for food use that exceeds 10%. This rule is effective November 17, 2025.
EPA finds low toxicity, no dietary risk
EPA's safety review concluded these two polymers have low acute and chronic toxicity, did not identify acute or chronic dietary endpoints of concern, and are not expected to pose acute or chronic aggregate risks. Short- and intermediate-term residential inhalation margin-of-exposure (MOE) estimates ranged from 2,600 to 59,000, which EPA found not to be of concern.
Children's safety factor set to 1X
EPA reduced the FQPA (infant and child) safety factor to 1X for these substances instead of the default 10X, because the agency found the toxicity database adequate, no developmental or reproductive effects in the available study, no evidence of neurotoxicity, and conservative exposure assumptions. This decision is part of the basis for granting the tolerance exemptions.
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