What Happened?

If you grow crops, raise animals, or work in food processing, pesticide makers can now use a chemical solvent called dimethyl sulfoxide (DMSO) in products applied to your operation without any cap on how much residue it can leave behind. ​

The Environmental Protection Agency (EPA) finalized the DMSO pesticide exemption rule effective Oct. 30, according to a Legis1 review of the Federal Register filing. Before the rule took effect, DMSO was not listed in any of the three federal tables that exempt certain pesticide ingredients from residue limits. The rule adds DMSO to all three:

  • Crops before and after harvest: Listed as a solvent with no numerical residue limit.
  • Animals: Same designation, no residue limit.
  • Food-contact surfaces: Covers antimicrobial formulations on dairy and food-processing equipment, also with no numerical limit.

Why Does it Matter to Me?

EPA concluded there is "a reasonable certainty that no harm will result from aggregate exposure" to DMSO residues, basing that finding on its determination that DMSO is of low toxicity, with systemic effects observed only at doses at or above 1,100 mg/kg/day.

Because EPA identified no toxicological endpoints of concern, it conducted a qualitative rather than a quantitative risk assessment and forwent the default 10-fold Food Quality Protection Act safety factor for infants and children. The agency identified skin and eye irritation, skin sensitization, and changes to eye lenses in laboratory animals at high doses. EPA also determined that no analytical enforcement method is required for DMSO residues under the new exemptions.

Both Sides, Now

The rule follows a petition filed by Spring Regulatory Sciences on behalf of Gaylord Chemical Company, L.L.C., and EPA received no relevant comments in response to the notice of filing.

Opponents argue that exempting DMSO from numerical residue limits may weaken safeguards, since the rule permits its use on crops, animals, and food-contact surfaces without a specified maximum residue level. EPA states that the rule imposes no enforceable duty on state, local, or tribal governments or the private sector.

What Happens Next?

Anyone who wants to formally challenge the rule must file a written objection or request a hearing with EPA's Hearing Clerk by Dec. 29, or they waive the right to raise issues the final rule resolved.

A separate public comment option is open through Dec. 30 at regulations.gov, but submitting an ordinary comment there does not substitute for the formal objection process. EPA encourages electronic filing of formal objections through its administrative law judges' e-filing system.

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