TSCA PIP (3:1) Rule: What It Means for Phosphate Ester Fluids

Under EPA's TSCA rule at 40 CFR 751.407, PIP (3:1) hydraulic fluids may be processed and distributed only for aviation or military-specification uses (as of 2026-10-13). That limit dates from 2021; the January 21, 2025 revision kept it and narrowed the lubricant exclusion. EPA chose not to prohibit continued US commercial use of fluid already in service.

• The 2024 revision was published on November 19, 2024 and took effect on January 21, 2025 (EPA, 89 FR 91486, 2024).

• Lubricants and greases containing PIP (3:1) outside aerospace and turbine uses cannot be processed or distributed after November 21, 2039 (40 CFR 751.407, 2026).

• PIP (3:1) present unintentionally at less than 0.1 percent by weight is outside the prohibitions (40 CFR 751.407, 2026).

• Manufacturers, processors and distributors must keep compliance records for 5 years from the date each record is generated (40 CFR 751.407, 2026).

This answer covers US federal law only: the TSCA section 6(h) rule on phenol, isopropylated phosphate (3:1), CASRN 68937-41-7. It does not cover EU REACH, other national rules, US state chemical lists or other triaryl phosphates with a different CASRN. It is not a legal classification of any specific product.

What is changing in the PIP (3:1) rule, and when?

The PIP (3:1) rule is moving from a 2021 prohibition with broad exclusions to a 2024 revision that adds phase-out dates, worker protection and a 0.1 percent threshold, while the hydraulic fluid exclusion stays as written in 2021 (EPA, 89 FR 91486, 2024). As of 2026-10-13, the revised rule is final and in effect, and the eCFR text of 40 CFR 751.407, current to October 8, 2026, carries the 2024 amendments (40 CFR 751.407, 2026). PIP (3:1) is one of five persistent, bioaccumulative and toxic (PBT) chemicals that Toxic Substances Control Act (TSCA) section 6(h) required EPA to regulate on an expedited track without a risk evaluation (EPA, 89 FR 91486, 2024).

The timeline below shows which federal action set each date that matters to a hydraulic fluid user:

The row that matters most is March 8, 2021: since that date, supplying a PIP (3:1) hydraulic fluid outside aviation and military specifications has been prohibited under 40 CFR 751.407 (40 CFR 751.407, 2026). The 2025 revision did not move that date.

Which hydraulic fluid uses of PIP (3:1) are still allowed?

Only two hydraulic fluid uses of PIP (3:1) are still allowed under US TSCA: fluids for the aviation industry, and fluids that must meet military specifications where no alternative chemical meets US Department of Defense requirements (40 CFR 751.407, 2026). The exclusion covers PIP (3:1) itself for use in such fluids, PIP (3:1)-containing products for use in them, and the finished fluids, and the current text sets no end date for it (40 CFR 751.407, 2026).

The military branch reaches beyond aircraft. In 2021 EPA expanded the proposed aviation-only wording because synthetic hydraulic fluids with low levels of PIP (3:1) are certified to military specifications such as MIL-DTL-32353A and used in vessel valve hydraulics (EPA, 86 FR 894, 2021). EPA also stated that PIP (3:1) fluids certified for turbine hydraulic fluid military specifications fall under aviation hydraulic fluid (EPA, 86 FR 894, 2021).

A commenter on the 2019 proposal asked EPA to exclude hydraulic fluids for valve control in higher-pressure, more extreme industrial settings. In the 2021 final rule EPA added no industrial exclusion, writing that "for industrial hydraulic fluids (excluding aviation), various alternative products not containing PIP (3:1) are already available in commerce", and widened only the military-specification branch (EPA, 86 FR 894, 2021). For a plant running a fire-resistant phosphate ester (HFDR) fluid in industrial equipment, the practical reading is that a supplier may not lawfully process or distribute that fluid in the United States if PIP (3:1) was intentionally added or is present at 0.1 percent by weight or more, unless one of the two exclusions applies.

What changed in the November 2024 PIP (3:1) revisions?

The November 2024 PIP (3:1) revisions narrowed the lubricant and grease exclusion, added workplace protection, a 0.1 percent threshold and longer record retention, and left the hydraulic fluid exclusion unchanged (EPA, 89 FR 91486, 2024).

Six changes matter here. First, the lubricant and grease exclusion now covers only aerospace use and turbine engines; all other PIP (3:1) lubricants and greases face a prohibition after November 21, 2039, which EPA set at 15 years instead of the 5 years it proposed (EPA, 89 FR 91486, 2024). Second, after January 21, 2025, workplaces that manufacture or process PIP (3:1) and PIP (3:1)-containing products must, in regulated areas where airborne exposure can reasonably be expected, provide respirators at least as protective as an assigned protection factor (APF) 10 half mask, and require chemically resistant gloves where skin contact is reasonably expected; import and the processing of certain listed products and parts are excluded (40 CFR 751.407, 2026). Third, PIP (3:1) present unintentionally below 0.1 percent by weight is outside the prohibitions (40 CFR 751.407, 2026). Fourth, compliance records must be kept for 5 years instead of 3 (EPA, 89 FR 91486, 2024). Fifth, suppliers had to place new notice text in safety data sheet (SDS) Sections 1(c) and 15 by February 19, 2025, or on labels by May 19, 2026 (40 CFR 751.407, 2026). Sixth, articles already containing PIP (3:1) may be processed and distributed for repair or maintenance if no PIP (3:1) is newly added (40 CFR 751.407, 2026).

The repair exclusion does not cover a hydraulic fluid refill: EPA's definitions treat hydraulic fluids and motor oils as products, not articles (EPA, 87 FR 12875, 2022).

Which hydraulic fluid and lubricant products does the PIP (3:1) rule affect?

The PIP (3:1) rule affects every hydraulic fluid, lubricant and grease to which PIP (3:1) is intentionally added or in which it is present at 0.1 percent by weight or more, and its status depends on the end use rather than on the base stock (40 CFR 751.407, 2026). The table below sorts the fluid products a phosphate ester user is likely to hold by their status under 40 CFR 751.407:

The key row is the industrial HFDR fluid: processing and distribution of a PIP (3:1)-containing industrial hydraulic fluid has been prohibited since March 8, 2021 (40 CFR 751.407, 2026).

Industrial hydraulic fluid was a real use when EPA wrote the rule. EPA's 2019 proposal noted that "a high-volume use of PIP (3:1) is in aviation and industrial hydraulic fluid and lubricants and greases" (EPA, 84 FR 36728, 2019). Whether a specific HFDR product on a site today contains PIP (3:1) is not answered in EPA's rule documents; only the supplier can confirm it for each product. The base fluid alone does not decide the question either, since EPA cited a synthetic hydrocarbon military fluid with low levels of PIP (3:1) (EPA, 86 FR 894, 2021).

What does the PIP (3:1) rule change technically for phosphate ester fluids?

For phosphate ester fluids, the PIP (3:1) rule matters because one component can provide fire resistance, anti-wear and anti-compressibility at once, so removing it changes more than one property (EPA, 84 FR 36728, 2019). EPA described PIP (3:1) in aviation phosphate ester fluids as a flame retardant, anti-wear additive and anti-compressibility additive, and stated that for systems at 5,000 psi or greater no feasible alternative formula met performance and safety standards (EPA, 84 FR 36728, 2019).

PIP (3:1) is also a UVCB substance, one of unknown or variable composition (EPA, 86 FR 894, 2021), and an isomer mixture whose proportions can be adjusted in manufacture to reach specific properties (EPA, 84 FR 36728, 2019). Two commercial isopropylated phosphates can therefore differ, which suggests a reformulated fluid should be qualified as a new fluid.

For aviation fluids, EPA recorded that any change in formula composition results in a full requalification with the aircraft manufacturer and the Federal Aviation Administration (EPA, 86 FR 894, 2021).

For industrial fluids, the qualification reference depends on the system. ISO 12922:2020 specifies minimum requirements for unused HFDR and other fire-resistant fluids in general industrial applications and is not intended for aerospace or power generation (ISO 12922:2020, scope). ISO 11365:2025 gives guidance and requirements for triaryl phosphate ester turbine control fluids and other hydraulic systems in power generation (ISO 11365:2025, scope). A replacement HFDR fluid needs checking against the fitting standard and the equipment maker's approval list before service. Before a changeover, confirm seal, paint and filter compatibility and the allowed residual of the old fluid with the equipment maker and the new fluid supplier, and follow both fluids' SDS for draining and flushing.

How do you find out whether a hydraulic fluid contains PIP (3:1)?

You find out whether a hydraulic fluid contains PIP (3:1) by reading the supplier's SDS for CASRN 68937-41-7 and EPA's notice text, then asking the supplier in writing about anything the SDS leaves unclear (40 CFR 751.407, 2026). The rule defines PIP (3:1) as phenol, isopropylated phosphate (3:1), CASRN 68937-41-7 (40 CFR 751.403, 2026). EPA also refers to it as iPTPP (EPA, 86 FR 894, 2021); search the SDS for that abbreviation as well as the CASRN.

The SDS is the first place to look because the rule puts the notice there. Every processor or distributor of PIP (3:1) or PIP (3:1)-containing products must notify customers in writing before or with each shipment, and the current text required that notice in SDS Sections 1(c) and 15 by February 19, 2025, or on the label by May 19, 2026 (40 CFR 751.407, 2026). The required text begins: "The Environmental Protection Agency prohibits processing and distribution of this chemical/product for any use other than" and then lists the permitted uses (40 CFR 751.407, 2026). An SDS carrying that sentence is a strong sign the fluid contains PIP (3:1).

Absence of the notice is weaker evidence. A fluid may list a different triaryl phosphate CASRN, or an older SDS may predate the 2025 text. In those cases a written supplier statement naming the CASRN of every phosphate ester component, and stating whether PIP (3:1) was intentionally added, settles the question. Laboratory analysis is a poor first step: explaining why it did not regulate commercial use of products, EPA noted that such regulation would "require testing, which may not be widely available for a chemical" (EPA, 89 FR 91486, 2024).

What should users of phosphate ester fluids do now?

Users of phosphate ester fluids should confirm PIP (3:1) content, match each use to an exclusion, plan replacement where no exclusion applies, and keep the evidence, in that order (40 CFR 751.407, 2026). The action table below assigns each step to a role and a deadline:

The most urgent row is the supplier statement, because the industrial hydraulic fluid prohibition has applied since March 8, 2021 and no transition period remains (40 CFR 751.407, 2026).

Continued use of fluid already in a system is not prohibited: EPA found it impracticable to restrict the continued commercial use of PIP (3:1)-containing products (EPA, 86 FR 894, 2021). The constraint arrives at the next purchase. When the fluid is drained for a changeover, follow SDS Section 13 for disposal, and follow the used oil rules in 40 CFR part 279 where the drained fluid meets the used oil definition (EPA, 84 FR 36728, 2019). 40 CFR 751.407(c) also requires all persons to follow existing regulations and best practices to keep PIP (3:1) out of water during commercial use (40 CFR 751.407, 2026).

What is still open in the PIP (3:1) rule?

Three points remain open in the PIP (3:1) rule as of 2026-10-13: the line between hydraulic fluid and lubricant, the reach of the turbine exclusion, and court or congressional action.

First, the subpart defines lubricants and grease as "any product used to reduce friction, heat, or wear between moving or adjacent solid surfaces, or that enhance the lubricity of other substances" and does not define hydraulic fluid (40 CFR 751.403, 2026). Because 40 CFR 751.407 lists hydraulic fluids and lubricants as separate uses, EPA likely does not treat an anti-wear hydraulic fluid as a lubricant; get a written EPA view before relying on the lubricant phase-out.

Second, EPA declined to limit the turbine exclusion to gas turbines in 2024 (EPA, 89 FR 91486, 2024), but the text names lubricants and greases, so the status of steam turbine control fluids is unanswered.

Third, the Ninth Circuit granted review of the 2024 rule's decaBDE provisions and remanded it without vacatur, "leaving the 2024 Rule in place during the pendency of further agency proceedings" (US Court of Appeals for the Ninth Circuit, 2026). A resolution to disapprove the 2024 rule was introduced in the House on February 12, 2025 (H.J. Res. 46, 2025). As of 2026-10-13, the resolution has had no action since its referral to the House Committee on Energy and Commerce on February 12, 2025 (US Government Publishing Office, 2025).

Lubinpla works this kind of question from a site's own SDS, technical data sheets and certificates and returns one cited document.

Lubinpla applies this kind of reasoning to your own documents and site history and drafts the document for your review before it goes out.

Sources checked 2026-10-13.

Sources

1. US Environmental Protection Agency. Decabromodiphenyl Ether and Phenol, Isopropylated Phosphate (3:1); Revision to the Regulation of Persistent, Bioaccumulative, and Toxic Chemicals Under the Toxic Substances Control Act (TSCA). Final rule, 89 FR 91486. November 19, 2024. https://www.federalregister.gov/documents/2024/11/19/2024-25758/decabromodiphenyl-ether-and-phenol-isopropylated-phosphate-31-revision-to-the-regulation-of

2. US Environmental Protection Agency. Phenol, Isopropylated Phosphate (3:1) (PIP (3:1)); Regulation of Persistent, Bioaccumulative, and Toxic Chemicals Under TSCA Section 6(h). Final rule, 86 FR 894. January 6, 2021. https://www.federalregister.gov/documents/2021/01/06/2020-28692/phenol-isopropylated-phosphate-31-pip-31-regulation-of-persistent-bioaccumulative-and-toxic

3. Office of the Federal Register. eCFR, 40 CFR 751.407 PIP (3:1). Current to October 8, 2026. https://www.ecfr.gov/current/title-40/chapter-I/subchapter-R/part-751/subpart-E/section-751.407

4. Office of the Federal Register. eCFR, 40 CFR 751.403 Definitions. Current to October 8, 2026. https://www.ecfr.gov/current/title-40/chapter-I/subchapter-R/part-751/subpart-E/section-751.403

5. Office of the Federal Register. eCFR, 40 CFR 751.401 General. Current to October 8, 2026. https://www.ecfr.gov/current/title-40/chapter-I/subchapter-R/part-751/subpart-E/section-751.401

6. US Environmental Protection Agency. Regulation of Persistent, Bioaccumulative, and Toxic Chemicals Under TSCA Section 6(h). Proposed rule, 84 FR 36728. July 29, 2019. https://www.federalregister.gov/documents/2019/07/29/2019-14022/regulation-of-persistent-bioaccumulative-and-toxic-chemicals-under-tsca-section-6h

7. US Environmental Protection Agency. Regulation of Persistent, Bioaccumulative, and Toxic Chemicals Under TSCA Section 6(h); Phenol, Isopropylated Phosphate (3:1); Further Compliance Date Extension. Final rule, 87 FR 12875. March 8, 2022. https://www.federalregister.gov/documents/2022/03/08/2022-04945/regulation-of-persistent-bioaccumulative-and-toxic-chemicals-under-tsca-section-6h-phenol

8. US Environmental Protection Agency. Decabromodiphenyl Ether and Phenol, Isopropylated Phosphate (3:1); Revision to the Regulation of Persistent, Bioaccumulative, and Toxic Chemicals Under TSCA. Proposed rule, 88 FR 82287. November 24, 2023. https://www.federalregister.gov/documents/2023/11/24/2023-25714/decabromodiphenyl-ether-and-phenol-isopropylated-phosphate-31-revision-to-the-regulation-of

9. US Environmental Protection Agency. Agency Information Collection Activities; Proposed Renewal Collection and Request for Comment; Regulation of PBT Chemicals Under TSCA Section 6(h). Notice, 91 FR 57593. September 10, 2026. https://www.federalregister.gov/documents/2026/09/10/2026-18434/agency-information-collection-activities-proposed-renewal-collection-and-request-for-comment

10. US Court of Appeals for the Ninth Circuit. Alaska Community Action on Toxics v. US EPA, No. 24-7497. Amended opinion, July 7, 2026. https://cdn.ca9.uscourts.gov/datastore/opinions/2026/07/07/24-7497.pdf

11. US House of Representatives. H.J. Res. 46, 119th Congress, disapproval of 89 FR 91486. Introduced February 12, 2025. https://www.govinfo.gov/content/pkg/BILLS-119hjres46ih/html/BILLS-119hjres46ih.htm

12. ISO. ISO 12922:2020 Lubricants, industrial oils and related products (class L), family H (hydraulic systems): Specifications for hydraulic fluids in categories HFAE, HFAS, HFB, HFC, HFDR and HFDU. Scope as published by the Estonian Centre for Standardisation (EVS-EN ISO 12922:2020). 2020. https://evs.ee/en/evs-en-iso-12922-2020

13. ISO. ISO 11365:2025 Petroleum and related products: Maintenance and use of triaryl phosphate ester turbine control fluids, guidance and requirements. Scope as published by BSI. 2025. https://knowledge.bsigroup.com/products/petroleum-and-related-products-maintenance-and-use-of-triaryl-phosphate-ester-turbine-control-fluids-guidance-and-requirements-1

14. US Government Publishing Office. Bill status, H.J. Res. 46, 119th Congress. Updated April 7, 2025. https://www.govinfo.gov/bulkdata/BILLSTATUS/119/hjres/BILLSTATUS-119hjres46.xml

Written by the Lubinpla team from the sources listed and checked against them before publication.

Reviewed by Jonghwan Moon, Founder & CEO, Lubinpla, 2026-10-14.