Dimethyl Sulfoxide Pesticide Tolerance Exemptions Lawsuit

The Environmental Protection Agency (EPA) issued a final rule on October 30, 2026, establishing exemptions from the requirement of a tolerance for residues of dimethyl sulfoxide (CAS Reg. No. 67-68-5). The exemptions cover its use as an inert ingredient, meaning a solvent or cosolvent, in pesticide formulations applied to growing crops or to raw agricultural commodities after harvest, in formulations applied to animals, and in antimicrobial formulations applied to food-contact surfaces. The rule appears at 91 FR 68480 through 91 FR 68484. It is effective October 30, 2026.

At a glance

• The rule is a final rule published by the EPA at 91 FR 68480 on October 30, 2026, and it took effect that same day.
• It establishes tolerance exemptions for dimethyl sulfoxide (CAS Reg. No. 67-68-5) when used as a solvent or cosolvent inert ingredient in certain pesticide formulations.
• Spring Regulatory Sciences, on behalf of Gaylord Chemical Company, LLC, filed the underlying petition under the Federal Food, Drug, and Cosmetic Act (FFDCA).
• The docket is EPA-HQ-OPP-2026-0529, with Federal Register document number 2026-22176.
• Objections and requests for hearings must be received on or before December 29, 2026, filed under the instructions in 40 CFR part 178.

What does the exemption actually cover?

A tolerance is the maximum residue level of a pesticide chemical that federal law allows in or on food. A tolerance exemption means no such maximum level is set for the described use. The EPA stated that this regulation eliminates the need to establish maximum permissible levels for residues of dimethyl sulfoxide when it is used in accordance with the terms of those exemptions.

The exemptions apply in three settings described in the rule’s abstract. They cover pesticide formulations applied to growing crops or to raw agricultural commodities after harvest. They also cover pesticide formulations applied to animals. The third setting is antimicrobial formulations applied to food-contact surfaces in public eating places, dairy-processing equipment, and food-processing equipment and utensils.

Dimethyl sulfoxide is described in the rule as an inert ingredient acting as a solvent or cosolvent. The exemption attaches to that use, not to dimethyl sulfoxide as an active pesticidal ingredient. The rule references 40 CFR part 180, the part of the Code of Federal Regulations that houses pesticide tolerance regulations.

What is established vs. what is alleged

The regulatory action here is established. A final rule is the agency’s own decision, published in the Federal Register, and this one carries the action line “Final rule.” The effective date is fixed in the document at October 30, 2026.

Nothing in the record reviewed here is an allegation in the litigation sense. There is no complaint, no court, and no dispute between parties described in the document. Dimethyl sulfoxide’s earlier uses and any past regulatory history are similarly absent from this document; the page covers the decision itself, not the background of the substance.

The safety basis appears only by reference. The docket lists a supporting document titled “IN-12546; Dimethyl Sulfoxide. Human Health Risk Assessment and Ecological Effects Assessment to Support Inert Ingredient Approval for use in Pesticide Formulations,” with document ID EPA-HQ-OPP-2026-0529-0007. The Federal Register summary supplied here does not restate the risk assessment’s findings, so the underlying health and ecological conclusions are not described in this article.

Where the rule stands procedurally

This is an agency rulemaking, not a court case. There is no multidistrict litigation (MDL, a consolidation of related federal lawsuits before one judge), no bellwether trial (a test trial chosen from a group of similar cases), and no Judicial Panel on Multidistrict Litigation involvement.

The rule was published at 91 FR 68480 with document number 2026-22176 and FRL-13642-01-OCSPP. The docket is EPA-HQ-OPP-2026-0529. The action is labeled a final rule, and the regulation is effective October 30, 2026.

A window for administrative challenge remains open. Objections and requests for hearings must be received on or before December 29, 2026, and must be filed in accordance with the instructions provided in 40 CFR part 178, with the document also pointing to Unit I.C. for direction. The regulations.gov docket lists a comment end date of December 30, 2026.

Key dates

• October 30, 2026: The EPA final rule is published at 91 FR 68480 and takes effect the same day.
• October 30, 2026: The regulations.gov docket for EPA-HQ-OPP-2026-0529 opens for comment.
• December 29, 2026: Deadline for objections and requests for hearings under 40 CFR part 178.
• December 30, 2026: The comment end date recorded on the regulations.gov docket.

What this does not establish

The document reviewed here does not show that any court has reviewed, stayed, or vacated the rule. It does not record a lawsuit, a settlement, or a verdict connected to dimethyl sulfoxide.

It does not set a numeric residue limit for dimethyl sulfoxide, because an exemption removes the need for one rather than setting a value. It does not describe the substance’s toxicity profile, its environmental fate, or the risk assessment’s conclusions in any detail.

It also does not state whether any objection or hearing request was filed by the December 29, 2026 deadline. A filing window that has opened is not the same as a challenge that has been made.

Frequently asked questions

What did the EPA’s October 30, 2026 rule do?

The Environmental Protection Agency published a final rule at 91 FR 68480 establishing exemptions from the requirement of a tolerance for residues of dimethyl sulfoxide (CAS Reg. No. 67-68-5) when used as a solvent or cosolvent inert ingredient in certain pesticide formulations. The exemptions cover formulations applied to growing crops or raw agricultural commodities after harvest, formulations applied to animals, and antimicrobial formulations applied to food-contact surfaces. The rule took effect October 30, 2026.

Who petitioned the EPA for the dimethyl sulfoxide exemption?

Spring Regulatory Sciences submitted the petition on behalf of Gaylord Chemical Company, LLC under the Federal Food, Drug, and Cosmetic Act. The docket for the proceeding is EPA-HQ-OPP-2026-0529, and a notice of filing is listed among the docket’s supporting documents. The Federal Register document does not state the date the petition was filed.

What is a tolerance exemption?

A tolerance is a maximum permitted residue level for a pesticide chemical in or on food, and an exemption means no such maximum level is required for the specified use. The EPA stated that this regulation eliminates the need to establish maximum permissible levels for residues of dimethyl sulfoxide when used in accordance with the terms of the exemptions. Tolerances and exemptions are codified under 40 CFR part 180.

Can the dimethyl sulfoxide rule still be challenged?

The rule’s own text sets a deadline of December 29, 2026 for objections and requests for hearings, which must be filed under the instructions in 40 CFR part 178. That provision describes an administrative filing route before the agency rather than a court proceeding. The record reviewed here does not show whether any such objection or hearing request was filed.

Is there any litigation over this rule?

No court case appears in the record reviewed here. The document is an EPA final rule published in the Federal Register, with no MDL, trial date, appeal, or verdict attached to it. Related hazardous-substance litigation is covered elsewhere on this site, including the AFFF PFAS firefighting foam litigation and the asbestos mesothelioma litigation.

Sources

1. Federal Register (Office of the Federal Register): “Dimethyl Sulfoxide in Pesticide Formulations; Exemptions From the Requirement of a Tolerance” (link, accessed 2026-11-02)
2. Federal Register (Office of the Federal Register): “All Documents” (link, accessed 2026-11-02)
3. Federal Register (Office of the Federal Register): “Agencies” (link, accessed 2026-11-02)
4. Federal Register (Office of the Federal Register): “Documents of type Rule” (link, accessed 2026-11-02)
5. Federal Register (Office of the Federal Register): “Documents of type Notice” (link, accessed 2026-11-02)
6. Federal Register (Office of the Federal Register): “Documents of type Proposed Rule” (link, accessed 2026-11-02)