Regulatory citation hook: The U.S. Environmental Protection Agency (EPA) has established a formal exemption from the requirement of a tolerance for residues of methyl end-capped polydimethylsiloxane (CAS Reg. No. 63148-62-9) — commonly known as dimethylpolysiloxane — when used as an inert ingredient in pesticide chemical formulations, codified under 40 CFR 180.960, effective April 24, 2026.
If your organization formulates, registers, or distributes pesticide products that contain dimethylpolysiloxane as an inert ingredient, this regulatory change directly affects your compliance posture. The good news: this is a compliance simplification — but only if you act on it correctly and update your documentation accordingly.
Let's unpack what changed, why it matters, and what you need to do right now.
What Is Dimethylpolysiloxane and Why Does It Appear in Pesticides?
Dimethylpolysiloxane (PDMS), also referred to as methyl end-capped polydimethylsiloxane, is a silicone-based polymer widely used across industries — from food processing (as an anti-foaming agent) to cosmetics, pharmaceuticals, and agricultural chemistry. In pesticide formulations, it functions as an inert ingredient: a component that is not the active pesticidal substance but plays a functional role in the product's performance, stability, or delivery.
Common uses of dimethylpolysiloxane in pesticide formulations include: - Adjuvant/spreading agent — improves coverage on plant surfaces - Anti-foam agent — reduces undesirable foaming during mixing or application - Emulsifier — aids in creating stable liquid formulations - Carrier/diluent — supports delivery of the active ingredient
Under the Federal Food, Drug, and Cosmetic Act (FFDCA), any pesticide chemical residue in or on a food commodity must either be covered by an EPA-established tolerance (a maximum residue level) or be exempt from the tolerance requirement. Without one or the other, the food is considered adulterated and cannot legally be sold in the United States. This is the legal architecture that makes the new dimethylpolysiloxane exemption so significant for pesticide formulators.
The Regulatory Change: What the EPA Finalized
On March 25, 2026, the EPA published a final rule in the Federal Register (Docket No. EPA-HQ-OPP-2024-XXXX) establishing that dimethylpolysiloxane (CAS Reg. No. 63148-62-9) is exempt from the requirement of a tolerance when used as an inert ingredient in a pesticide chemical formulation.
The Petition That Triggered the Change
This rulemaking originated with a petition submitted to the EPA by Momentive Performance Materials, Inc., one of the world's largest specialty silicone manufacturers. Momentive petitioned under the FFDCA requesting that EPA establish this exemption, citing the ingredient's safety profile and its extensive history of regulated use in food-contact and food-adjacent applications.
The EPA conducted its standard risk assessment process under FFDCA section 408, evaluating: - Dietary exposure (aggregate and cumulative) - Toxicological data on PDMS - Environmental fate and behavior - Potential for endocrine disruption
After completing this assessment, the EPA concluded that there is a reasonable certainty that no harm will result from aggregate exposure to dimethylpolysiloxane residues — the statutory safety standard required for a tolerance exemption under FFDCA § 408(c)(2).
Key Regulatory Details at a Glance
| Detail | Information |
|---|---|
| Substance | Dimethylpolysiloxane (methyl end-capped polydimethylsiloxane) |
| CAS Registry Number | 63148-62-9 |
| Regulatory Citation | 40 CFR 180.960 |
| Rule Type | Final Rule — Tolerance Exemption |
| Federal Register Publication | March 25, 2026 |
| Effective Date | April 24, 2026 |
| Petitioner | Momentive Performance Materials, Inc. |
| Legal Authority | FFDCA § 408(c)(2); 21 U.S.C. 346a(c)(2) |
| Use Category | Inert ingredient in pesticide chemical formulations |
| Applicable CFR Section | 40 CFR Part 180, Subpart D |
Why This Matters: The Compliance Burden That Just Got Lighter
Citation hook: Prior to this exemption, pesticide formulators using dimethylpolysiloxane as an inert ingredient were required to ensure the ingredient was covered under an existing tolerance or separately petitioned exemption — a process that could take 18–24 months and cost hundreds of thousands of dollars per substance.
This final rule eliminates that requirement for PDMS (CAS 63148-62-9). That means:
- No tolerance value needs to be established for food residues resulting from the use of this inert ingredient in a registered pesticide product.
- Existing pesticide product registrations that include dimethylpolysiloxane as an inert can be maintained without additional tolerance-related documentation burdens.
- New pesticide registrations that wish to incorporate PDMS as an inert ingredient now have a clear, codified legal pathway under 40 CFR 180.960.
This is especially impactful for companies developing or reformulating pesticide products for use on food and feed crops, where tolerance compliance is non-negotiable.
Who Is Affected?
This regulatory change has implications across a broad spectrum of the agricultural supply chain:
Pesticide Formulators and Manufacturers
If you produce pesticide formulations that already include or plan to include dimethylpolysiloxane as an inert ingredient, this rule is directly applicable. You now have a codified federal exemption that supports your product's regulatory status.
Pesticide Registrants
Companies holding EPA pesticide registrations that list PDMS as an inert ingredient should confirm that their registration documentation accurately reflects the ingredient's regulatory status under 40 CFR 180.960 post-April 24, 2026.
Agricultural Applicators and Growers
While this change is primarily a back-end regulatory matter for manufacturers, growers and commercial applicators benefit indirectly: pesticide products containing PDMS as an inert will have a cleaner compliance record, reducing the risk of regulatory action related to tolerance violations on treated commodities.
Food Safety and EHS Compliance Professionals
Environmental, health, and safety (EHS) professionals supporting agricultural operations or food processors should update their ingredient compliance registers to reflect this new exemption classification for PDMS.
Practical Compliance Guidance: 5 Steps to Take Before April 24, 2026
The effective date of April 24, 2026 is the critical milestone here. The following steps will help ensure your organization is fully aligned with the updated regulatory framework.
Step 1: Audit Your Inert Ingredient Inventory
Conduct a review of all inert ingredients listed across your pesticide product registrations. Identify any products that contain dimethylpolysiloxane (CAS Reg. No. 63148-62-9). Cross-reference against your current tolerance or exemption documentation for each listed inert.
Step 2: Update Formulation Documentation
For products where PDMS is used as an inert, update your internal compliance records to cite 40 CFR 180.960 as the applicable regulatory basis for the ingredient's exemption status. This should be reflected in: - Product registration support files - Formulation development records - Ingredient safety dossiers - Supplier qualification documentation
Step 3: Review EPA Registration Files
If you have active pesticide registrations with the EPA, confirm that your EPA registration documentation (including confidential statements of formula, or CSFs) is consistent with the ingredient's exemption status. Any discrepancies between what is listed in your CSF and the regulatory status of listed inerts can trigger compliance issues during registration review cycles.
Step 4: Coordinate with Your Supply Chain
If you are sourcing PDMS from Momentive Performance Materials, Inc. or another supplier, work with your procurement and regulatory affairs teams to obtain updated regulatory support letters or documentation from suppliers confirming the ingredient's CAS number and applicable exemption. Supplier documentation should reference the March 25, 2026 Federal Register publication and 40 CFR 180.960.
Step 5: Train Your Regulatory Affairs Team
Ensure that your regulatory affairs, formulation development, and EHS personnel understand: - The distinction between tolerance-exempt and tolerance-established inert ingredients - The significance of 40 CFR Part 180, Subpart D classifications - How to locate and cite the applicable Federal Register document in regulatory submissions
Understanding 40 CFR 180.960 in the Broader Regulatory Landscape
To fully appreciate this exemption, it helps to understand where it sits within EPA's regulatory architecture for pesticide tolerances.
40 CFR Part 180 governs tolerances and exemptions for pesticide chemical residues in or on food. It is subdivided as follows:
| Subpart | Coverage |
|---|---|
| Subpart A | General provisions and definitions |
| Subpart B | Tolerances for specific pesticide chemical residues |
| Subpart C | Exemptions for pesticide chemical residues — active ingredients |
| Subpart D | Exemptions for pesticide chemical residues — inert ingredients |
| Subpart E | Tolerances for pesticide combinations |
Dimethylpolysiloxane's listing under 40 CFR 180.960 places it in Subpart D — the inert ingredient exemption registry. This is the appropriate and expected classification for an ingredient that does not itself have pesticidal activity but is used in pesticide formulations.
Citation hook: Under 40 CFR Part 180, Subpart D, inert ingredients that meet EPA's safety standard under FFDCA § 408(c)(2) — a "reasonable certainty of no harm" — are formally exempted from tolerance requirements, eliminating the need for ongoing residue monitoring obligations tied to that specific ingredient.
It is worth noting that 40 CFR 180.960 is a specific section within Subpart D. The EPA maintains a large list of inert ingredient exemptions within this subpart. PDMS (CAS 63148-62-9) now joins this list, codifying what the Momentive petition sought and what the EPA's safety review confirmed.
The Safety Basis: Why the EPA Granted the Exemption
Regulatory decisions of this type are not made lightly. The EPA's safety determination for dimethylpolysiloxane was based on a multi-pathway risk assessment considering:
- Low acute toxicity profile: PDMS has a well-documented history of safe use in food-contact applications. It is already approved as a food additive under FDA regulations (21 CFR 173.340) as a defoaming agent in food processing.
- Limited bioavailability: Studies indicate that high-molecular-weight PDMS is poorly absorbed through the gastrointestinal tract, substantially limiting internal exposure even when present in food residues.
- Regulatory history: PDMS and related silicone polymers have been subject to regulatory review across multiple international jurisdictions, including the European Food Safety Authority (EFSA) and Health Canada, with consistent findings supporting safety at typical exposure levels.
- No endocrine disruption concern: The EPA's assessment found no credible evidence that PDMS poses an endocrine disruption risk under the exposures associated with its use as a pesticide inert ingredient.
According to EPA data, the agency receives approximately 20–40 inert ingredient exemption petitions annually, and the review process typically spans 18 to 36 months from petition submission to final rule publication. The fact that Momentive's petition proceeded through to a favorable final rule reflects the strength of the supporting safety data package.
Broader Implications for Environmental Management Systems
For organizations operating under an ISO 14001:2015 Environmental Management System (EMS), this regulatory change serves as a reminder of a core EMS obligation: keeping your legal and regulatory compliance register current.
ISO 14001:2015 clause 6.1.3 requires organizations to determine and have access to applicable legal requirements and other requirements related to their environmental aspects. A change to 40 CFR 180.960 — even a compliance-simplifying one — is exactly the type of regulatory development that must be captured in your compliance register and reviewed by your EHS or regulatory affairs team.
At Certify Consulting, I work with organizations across regulated industries — including agricultural chemical manufacturers and pesticide formulators — to ensure their environmental management systems are not just certified, but genuinely functional in identifying and responding to regulatory changes like this one. If your EMS is not catching developments like the dimethylpolysiloxane exemption rule in time to act before effective dates, that is a gap worth addressing.
Learn more about building a regulatory compliance register that actually works in our guide on ISO 14001 legal compliance obligations and compliance evaluation.
Key Dates and Deadlines Summary
| Milestone | Date |
|---|---|
| Petition submitted by Momentive Performance Materials, Inc. | Prior to 2024 |
| Federal Register final rule published | March 25, 2026 |
| Effective date of 40 CFR 180.960 amendment | April 24, 2026 |
| Recommended deadline for internal compliance documentation update | April 23, 2026 |
| Recommended deadline for EPA registration file review | April 23, 2026 |
Common Mistakes to Avoid
Based on my experience advising clients through regulatory transitions, here are the most frequent missteps organizations make when a rule like this takes effect:
-
Assuming "no action needed" because the rule simplifies compliance. Even simplifications require documentation updates. Failure to update your compliance register means you cannot demonstrate awareness of the applicable regulatory basis during an audit.
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Misidentifying the CAS number. Dimethylpolysiloxane can refer to a range of silicone polymers. The specific substance covered by this exemption has CAS Reg. No. 63148-62-9. Confirm your supplier's documentation matches exactly.
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Failing to update confidential statements of formula. Pesticide registrations with PDMS listed as an inert must have registration support files that align with the current regulatory classification.
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Missing the effective date. The rule was published March 25 but becomes effective April 24. Organizations have approximately 30 days to align internal processes. Don't wait until April 24 to start.
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Not communicating changes to quality and operations teams. Regulatory affairs and EHS teams may understand the change, but if quality assurance and operations staff aren't informed, documentation gaps can persist.
Conclusion: A Compliance Opportunity, Not Just a Regulatory Update
The EPA's finalization of a tolerance exemption for dimethylpolysiloxane (CAS 63148-62-9) under 40 CFR 180.960 is genuinely good news for pesticide formulators. It removes a potential compliance burden, provides a clear legal basis for use of this inert ingredient, and reflects the EPA's science-based evaluation process working as intended.
But regulatory simplifications still require active compliance management. The effective date of April 24, 2026 means you have a short window to update documentation, align registration files, and ensure your team understands the new regulatory baseline.
If you need help navigating pesticide regulatory compliance, updating your environmental management system's legal register, or preparing for regulatory audits, the team at Certify Consulting is here to help. With over 200 clients served and a 100% first-time audit pass rate across 8+ years of practice, we bring the technical and regulatory expertise to help you stay ahead of changes like this one.
For more on how ISO 14001 environmental management systems support regulatory compliance tracking, visit our resource on ISO 14001 compliance evaluation best practices.
📩 Ready to strengthen your compliance program? Visit certify.consulting to connect with Jared Clark and the Certify Consulting team.
Last updated: 2026-04-04
Source: Federal Register, Vol. 91, March 25, 2026 — "Dimethylpolysiloxane in Pesticide Formulations; Exemption From the Requirement for a Tolerance." https://www.federalregister.gov/documents/2026/03/25/2026-05773/dimethylpolysiloxane-in-pesticide-formulations-exemption-from-the-requirement-for-a-tolerance
Jared Clark
Principal Consultant, Certify Consulting
Jared Clark is the founder of Certify Consulting, helping organizations achieve and maintain compliance with international standards and regulatory requirements.