California AB 1603 Requires Public Disclosure of PFAS in Pesticides and May Increase Regulatory and Litigation Risk

California has enacted Assembly Bill 1603 (AB 1603), a new transparency law that will require the California Department of Pesticide Regulation to publicly identify registered pesticides containing intentionally added PFAS and report how those products are used across the state. Although the law does not ban PFAS-containing pesticides or create a new private right of action, the resulting product and usage data could increase regulatory scrutiny and litigation risk for businesses throughout the agricultural and pesticide supply chains. As California joins a broader state trend toward greater PFAS oversight, companies may want to review their products, application and distribution records, supplier arrangements, and potential due diligence considerations before the state’s database goes live.

As stated in an earlier O’Melveny client alert, the presence of PFAS in pesticides constitutes a pathway by which these chemicals can enter the environment. Now, California has enacted a new PFAS transparency law with potentially significant consequences for the agricultural supply chain. Assembly Bill 1603 (AB 1603)—approved and chaptered on September 27, 2026 as Chapter 531—directs the California Department of Pesticide Regulation (DPR) to identify pesticides containing per- and polyfluoroalkyl substances (PFAS), publish usage trends, and maintain a public list of registered pesticides containing PFAS. The law does not ban those products, but the resulting data could sharpen regulatory scrutiny and provide a roadmap for litigation involving growers, applicators, distributors, pesticide manufacturers, and upstream chemical suppliers. (AB 1603, Legislative Counsel’s Digest; §§ 1–4.)

Key Takeaways

• PFAS pesticide data will become public. By January 1, 2028, DPR must identify pesticides containing PFAS ingredients and report annual usage trends.
• California will publish a statewide product list. DPR must list registered pesticides containing PFAS ingredients and update the list within 60 days after a new covered product is registered.
• Greater transparency may increase legal exposure. Public product and usage data could help regulators and plaintiffs investigate alleged PFAS pathways involving water, soil, produce, and the broader pesticide supply chain.

What AB 1603 Requires

AB 1603 adds a class-based definition of PFAS for California’s pesticide laws: fluorinated organic chemicals containing at least one fully fluorinated carbon atom. The law separately defines “PFAS pesticide ingredients” as PFAS intentionally added to a pesticide as active, adjuvant, or inert ingredients. (AB 1603 § 2, adding Cal. Food & Agric. Code §§ 12500.3–12500.4.)

The core requirement of the new law is disclosure. By the earlier of January 1, 2028 or DPR’s posting of the pesticide-use reporting database containing 2026 data—and annually thereafter—DPR must identify whether a pesticide contains PFAS pesticide ingredients, includes PFAS as a category of interest in the database, and includes PFAS-pesticide use trends in its annual report and other relevant reporting documents. (AB 1603 § 4, adding Cal. Food & Agric. Code § 13201(a).)

DPR must also publish a list of all registered pesticides containing PFAS pesticide ingredients and send that list to each county agricultural commissioner by January 1, 2028. DPR is also required to update the online list and transmit the update to county commissioners within 60 calendar days of registration of any new covered pesticide. (AB 1603 § 4, adding Cal. Food & Agric. Code § 13201(b).)

Why the New Data May Matter in Enforcement and Litigation

AB 1603 reflects California’s continued expansion of PFAS oversight into the agricultural sector. The California Legislature’s findings cite reported PFAS detections in drinking water and California-grown produce and identify PFAS pesticides as a potential source of contamination. (AB 1603 § 1(a)(1)–(7).) Those findings do not establish liability in any particular matter, but they provide context that is likely to feature in future regulatory inquiries and civil complaints.

Once DPR’s database and trend data become public, it may be easier to identify where particular PFAS-containing pesticides were used and to allege connections among applications, environmental media, and potential exposure. Impacts on drinking water may attract particular attention, though plaintiffs may also focus on alleged residues in produce or migration into soil, groundwater, surface water, or sediment, as well as into the food supply.

The nexus to drinking water resources is particularly important. Heightened concern about PFAS since 2016 has been driven in significant part by the Environmental Protection Agency’s (EPA) publication of the Third Unregulated Contaminant Monitoring Rule (UCMR 3) data documenting PFAS occurrence in public water systems nationwide. The EPA’s Fifth Unregulated Contaminant Monitoring Rule’s (UCMR 5) broader monitoring for 29 PFAS at substantially lower reporting levels does not diminish that concern; its findings reinforce the impression that PFAS’ impact to public water systems are more widespread than UCMR 3’s narrower analyte list and less-sensitive methods could reveal. (EPA, UCMR 3 Data Summary (2016); EPA, UCMR 5 Data Summary (2026).) AB 1603’s declarations and findings likewise state that an estimated “45 percent of the United States’ tap water is contaminated with PFAS.” (AB 1603 § 1(a).) 

Potential impacts to agricultural produce may draw comparable scrutiny. Among other findings, the California Legislature states that “approximated 2,500,000 pounds of active ingredient PFAS pesticides are applied to California crops” annually and that California has an interest in reducing “the presence of all PFAS pesticides on California-grown produce and in California’s soil, air, and water.” The findings therefore supply an express legislative link between PFAS pesticide use and potential produce contamination, which may inform future regulatory inquiries and product-related claims. (AB 1603 § 1(a)–(b).) PFAS’ impact on the food supply is a growing area of concern in the evolving body of PFAS law, and, given the nationwide distribution of California-grown produce, entities outside California may now face heightened liability exposure arising from alleged PFAS contamination in products that cross state lines.

Thus, the potential defendant pool may extend beyond owners and operators of agricultural land and the manufacturers of the PFAS themselves to include pesticide manufacturers, distributors, applicators, and upstream suppliers, as well as farmers, distributors, and retailers of affected produce. Specific causes of action or grounds for enforcement would depend on the facts and the asserted statutory or common-law theories, including product liability. 

Liability exposure under the federal Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA), commonly referred to as Superfund, and its California analogue, the Hazardous Substances Account, is unlikely as both laws contain a limited exclusion for certain registered pesticide products that are applied in accordance with labeling. AB 1603 does not alter those liability standards, so sites that follow such applications will not be subject to the strict, joint, and several liability regime of Superfund laws. However, the ability to take advantage of this exclusion will inevitably require careful analysis of the product, use, release pathway, governing statute, and available defenses. 

Due Diligence Considerations

The law also has transactional due diligence implications. Most immediately, entities interested in acquiring real property or businesses involved in or near California agricultural operations may wish to evaluate potential PFAS use once the state database is populated. Not only can such information help identify potential PFAS-related liabilities with respect to the relevant property or business, but in the case of properties and businesses located near agricultural operations, such diligence can serve a defensive purpose, as the attention of regulators or plaintiffs’ lawyers may be deflected from the target of a transaction to a nearby agricultural operation. 

What Other States Have Done

The new California law may be viewed as part of a broader—but still uneven—state trend toward regulating PFAS in pesticides. Maine has adopted the most direct prohibition: its pesticide-control law bars distribution of pesticides contaminated by PFAS and, beginning January 1, 2030, bars pesticides containing intentionally added PFAS that may not be sold under Maine’s general PFAS-products law. Maine also requires pesticide registrants to disclose whether a product formulation contains PFAS and whether the product is stored or distributed in a fluorinated high-density polyethylene container. (Me. Rev. Stat. tit. 7, §§ 604, 606; tit. 38, § 1614.)

Other states have considered more categorical restrictions. For example, Maryland legislation introduced in 2025 (Md. H.B. 386/S.B. 345) would have required the state agriculture department to identify registered pesticides listing PFAS as active ingredients and would have phased in restrictions on their use. Vermont legislation (Vt. H 911) introduced in 2026 would prohibit pesticides and pesticide packaging containing PFAS. Those proposals illustrate continued legislative interest, but they should be distinguished from the enacted requirements in California, Maine, and Minnesota. 

What Companies Might Want to Consider Now

Businesses that manufacture, formulate, distribute, sell, or apply pesticides in California—as well as agricultural operators that use them—should consider preparing before DPR’s database is posted. Useful steps may include:

• identifying products and formulations that may fall within AB 1603’s PFAS definitions, including active, adjuvant, and inert ingredients;
• mapping California sales, distribution, and application records against sensitive receptors such as public water systems and groundwater resources;
• reviewing supplier representations, product stewardship practices, indemnities, insurance, and record retention protocols; and
• assessing potential regulatory and litigation exposure under applicable statutes and common-law theories.

Companies may wish to conduct appropriately scoped assessments with counsel to evaluate whether privilege protections are available. O’Melveny’s environmental and mass tort lawyers advise clients on chemical regulation, pesticide issues, PFAS risk, and complex litigation across the product supply chain.

This memorandum is a summary for general information and discussion only and may be considered an advertisement for certain purposes. It is not a full analysis of the matters presented, may not be relied upon as legal advice, and does not purport to represent the views of our clients or the Firm. Reza Zarghamee, an O'Melveny partner licensed to practice law in the District of Columbia, California, New York, and Virginia; Hannah Y. Chanoine, an O’Melveny partner licensed to practice law in New York and Massachusetts; Eric Rothenberg, an O'Melveny of counsel licensed to practice law in New York and Missouri; John D. Renneisen, an O’Melveny senior counsel licensed to practice law in the District of Columbia; Andrew Weisberg, an O’Melveny counsel licensed to practice law in California; Emma Byrd, an O’Melveny associate licensed to practice law in New York; and Marcus S. Pipitone, an O’Melveny associate licensed to practice law in California, contributed to the content of this newsletter. The views expressed in this newsletter are the views of the authors except as otherwise noted.

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