Monthly newsletter Material Concerns: Legal Updates on Substances of Emerging Concern keeps clients informed on the latest legal, regulatory and scientific developments related to substances of emerging concern. Each issue delivers concise, actionable insights to help companies navigate the evolving landscape of environmental law.

EPA Again Proposes Nationwide Drinking Water Standards for Perchlorate

By Joseph Zaleski 

The United States Environmental Protection Agency (EPA) has published proposed nationwide drinking water regulations for perchlorate, which proposes levels more stringent than previously anticipated. On January 6, 2026, EPA proposed a non-enforceable, health-based Maximum Contaminant Level Goal (MCLG) of 20 micrograms per liter (µg/L), often referred to as “parts per billion.” EPA has also requested public comment on setting the enforceable Maximum Contaminant Level (MCL) at one of three potential levels: 20 µg/L, 40 µg/L, or 80 µg/L. 

As discussed in the November 2025 edition of Material Concerns, EPA has considered nationwide standards for perchlorate for over 15 years and was under a federal consent decree with strict deadlines to publish the new proposed levels. In EPA’s January 2026 proposal, the agency acknowledged that the proposal is strictly in response to legal obligations: “[t]he Administrator has determined that the benefits of this regulation would not justify the costs; however, the EPA is required to issue [a National Primary Drinking Water Regulation] and MCLG for perchlorate in response to the D.C. Circuit's decision in NRDC v. Regan.” 

In February 2011, EPA issued a regulatory determination that establishing a nationwide primary drinking water standard for perchlorate was warranted under the federal Safe Drinking Water Act (SDWA). In June 2019, in the first Trump administration, EPA proposed to set the MCL and MCLG for perchlorate at 56 µg/L. The agency also took comment on alternative MCLs of 18 µg/L or 90 µg/L as well as public comment on entirely rescinding the 2011 regulatory determination for perchlorate. EPA’s suggestion to rescind the 2011 determination was based on what it said was new information that showed perchlorate did not occur in public drinking water systems at a frequency or at levels where national regulation would lead to meaningful public health risk reduction. After reviewing public comment on this 2019 proposal, EPA in July 2020 attempted to rescind the 2011 determination to regulate perchlorate under the SDWA and proposed not to move forward with any national primary drinking water standards for the chemical. That move led to the NRDC v. Regan litigation. 

Notably, the 20 µg/L MCLG and two of the three MCL options in the current proposal are considerably lower than the 56 µg/L previously proposed. Even so, the proposed levels are much less stringent than established drinking water standards in Massachusetts and California, which have adopted enforceable limits set at 2 µg/L and 6 µg/L, respectively. 

EPA will hold a virtual public hearing on its new perchlorate proposal on February 19, 2026, and EPA will accept public comments on the proposed rule through March 6, 2026.

Scrutiny Of Microplastic Detection Methods Raises Questions About Health-Risk Claims

By Jennifer E. Hackman

Growing concern about the potential detection of microplastics in the human body has intensified scientific debate over both the reliability of detection methods and the health significance of reported findings. A November 13, 2025, letter published in Nature Medicine, titled “Challenges in studying microplastics in human brain,” responded to an earlier study by Alexander J. Nihart reporting microplastics—particularly polyethylene—in human liver, kidney and brain tissue. The authors of the November letter—including Dr. Dušan Materić of the Helmholtz Centre for Environmental Research (UFZ) in Leipzig, Germany—noted research protocols in the Nihart study failed to include necessary safeguards to prevent cross-contamination essential in studies identifying exceptionally small plastic particles in biological material. 

To illustrate their concerns, the authors discussed the method used by Nihart and compared them with established peer-reviewed scientific guidelines. The authors concluded that the study relied on pyrolysis gas chromatography–mass spectrometry (Py GC–MS), a technique that seeks to identify materials by heating samples until they decompose into characteristic chemical fragments. According to the authors, this method can produce false positives because naturally occurring components of human tissue, such as fatty lipids in our bodies, can break down into compounds that resemble common plastics like polyethylene when heated. The authors also emphasized how easily microplastics from the surrounding environment—air, lab equipment or reagents—can contaminate samples unless strict procedures are followed. The authors state these limitations, “reflect[] a broader challenge across studies investigating [microplastics and nanoplastics], highlighting the need to standardize sampling, sample preparation, detection, QA/QC procedures and their documentation to ensure credible and reproducible findings in human biomonitoring.”

The conclusions presented in the letter may alter the trajectory of microplastic research and potential regulatory action. Calling attention to the risk of contamination, the need for adequate controls, and physiologically plausible alternatives (such as endogenous fats mimicking polymer signatures), the authors seek to promote more rigorous, standardized analytical approaches to produce reliable findings. 

EPA’s Proposed PFAS Reporting Rollback Faces Legal Pushback

By Christopher M. Sorenson

The United States Environmental Protection Agency (EPA) is facing opposition to its proposed rollback of per- and polyfluoroalkyl substances (PFAS) reporting requirements under the Toxic Substances Control Act (TSCA). Forty-one environmental groups and 15 state attorneys general argue the proposed reporting exemptions conflict with the plain language of the Fiscal Year 2020 National Defense Authorization Act (FY2020 NDAA) and represent an unwarranted reversal of EPA’s prior stance.  

EPA’s proposal exempts several categories from TSCA PFAS reporting, including low-concentration PFAS present at 0.1% or less in mixtures or products, PFAS in imported articles, byproducts, impurities, research and development substances, and non-isolated intermediates. Critics say these exemptions will eliminate more than 97% of the PFAS data that EPA initially expected to collect, which will drastically reduce the number of reporters from more than 13,300 to roughly 250.  

In a December 23 letter, environmental groups argue that the proposed rollback violates TSCA’s statutory mandate, which requires “each person” who has manufactured PFAS to submit a report, without exception. These groups contend that the proposal is arbitrary and capricious because it allows thousands of companies to avoid reporting, despite what they characterize as Congress’ explicit instructions.

State attorneys general further assert that EPA’s plan represents an unsupported reversal of EPA’s previous positions, undermining data collection critical to assessing PFAS related risks. They contend that Congress provided no discretion for EPA to create categorical exemptions that are not reflected in the statute. 

The environmental groups argue that EPA cannot invoke TSCA’s general provisions aimed at reducing reporting burdens to override the statute’s explicit and mandatory PFAS reporting requirement in TSCA Section 8(a)(7), 15 U.S.C. § 2607(a)(7). The groups dispute EPA’s claims that exempted entities hold little relevant information or that the excluded information is of little value, and the groups argue instead that the lack of data will significantly impair environmental and public health risk assessments. 

For industry, the proposed rollback could lighten near-term compliance burdens, but the mounting opposition signals the potential for litigation and continued regulatory volatility. Understanding the evolving rulemaking and potential legal challenges is critical for managing risk, planning disclosures and engaging strategically with regulators. Companies manufacturing, importing or incidentally generating PFAS should monitor developments closely and prepare for the possibility of shifting obligations as legal challenges unfold.

EPA Prepares 2026 TSCA Framework Rule

By Nisha L. Albert

The United States Environmental Protection Agency (EPA) is moving toward finalizing a new Toxic Substances Control Act (TSCA) framework rule in 2026, a decision that could shape how existing chemicals are evaluated and regulated for years to come—or at least until a future administration rewrites it. The proposed rule marks the third major rewrite of the TSCA evaluation framework in less than a decade, which demonstrates a pattern of significant regulatory shifts when a different political party occupies the White House. 

The upcoming framework is expected to revive the first Trump Administration’s “use by use” risk determination approach, which evaluates chemical risks based on specific uses rather than across the chemical as a whole. This approach differs sharply from the Biden Administration’s regulatory framework, which generally assessed risks by looking at all possible ways a chemical could cause harm, rather than an evaluation of the harm during its intended use. Industry groups have welcomed the return to narrower evaluations, arguing the need to restore predictability, but lament the uncertainty these frequent changes have brought. Environmental groups and Democratic state attorneys general strongly oppose the proposed rule, as noted in the November comments to the proposed rule. The AGs argue the proposed rule understates risk, unlawfully deviates from TSCA requirements, and will lead to the states reinitiating paused litigation challenging the Biden Administration’s rule. 

EPA’s regulatory timeline projects an April 2026 completion date, though prior delays suggest this may be optimistic. While this rulemaking is ongoing, EPA will continue to follow the Biden Administration’s approach until the framework rule revisions are finalized. Alongside the framework rulemaking, EPA plans to advance or revisit a number of individual chemical rules, including:

• Completing risk-management rules this spring or summer originally proposed in the Biden Administration for n-methylpyrrolidone, 1-bromopropane, and pigment violet 29.
• Revisiting rules the Biden Administration finalized for methylene chloride, trichloroethylene (TCE), and perchloroethylene (PCE).
• Reconsidering—without yet committing to revise—the Biden Administration’s finalized rule on carbon tetrachloride.
• Revisiting the Biden Administration’s December 2024 risk evaluation of 1,4-dioxane, which did not result in a proposed risk-management rule.

The ongoing revisions to EPA’s TSCA framework rule add to a period of regulatory transition for chemical manufacturers and other regulated entities. While EPA continues to apply the existing framework, companies may need to account for the possibility that evaluation methods, risk determinations and regulatory timelines could change again as rulemaking and related litigation proceed.

Ninth Circuit Hears Arguments On Constitutional Challenges To California Climate Disclosure Laws

Update To Our Prior Coverage Of California Chamber of Commerce v. California Air Resources Board (CARB), Addressing SB 261 and SB 253

By Jennifer E. Hackman

On January 9, the Ninth Circuit heard oral argument in the ongoing challenges to California’s two major climate disclosure statutes: SB 261, the Climate Related Financial Risk Act, and SB 253, the Climate Corporate Data Accountability Act. As we outlined in an earlier update, business groups have argued that both laws amount to unconstitutional, compelled speech. The January hearing marked the first time the three judge panel engaged directly with the parties on the First Amendment questions at the center of the appeal.

The plaintiffs reiterated their argument that both statutes require companies to make extensive public disclosures unrelated to any specific commercial transaction. In their view, SB 261 goes a step further by compelling companies to articulate judgment heavy narratives about climate related financial risk—statements plaintiffs contend fall outside the category of “purely factual and uncontroversial” commercial disclosures permitted under the First Amendment.

On the other hand, the State of California defended both statutes as standard commercial disclosure requirements designed to provide investors and the public with uniform information. The State emphasized that the laws regulate commercial—not political—speech; and therefore, the statutes should be evaluated under the more deferential standard applicable to commercial disclosure requirements.

The panel pressed both sides on several points:

• SB 261’s narrative reporting and whether its qualitative assessments go beyond permissible factual disclosure;
• SB 253’s Scope 3 emissions requirement, including whether Scope 3 reporting could be severed if deemed unconstitutional; and,
• overlap with Securities and Exchange Commission climate risk rules, and the practical implications of potentially inconsistent state and federal disclosure regimes.

The Ninth Circuit took the matter under submission and did not provide a timeline for a decision.

Looking Ahead

SB 261: Stay Remains Fully In Effect

A key practical takeaway is that the hearing did not alter the status of SB 261. The Ninth Circuit’s stay—initially issued on November 18, 2025—remains in full force. As a result:

• Companies remain excused from filing climate related financial risk reports under SB 261.
• The January 1, 2026, statutory reporting deadline continues to be suspended.
• CARB has acknowledged the stay and committed to setting a revised reporting date once the appeal is resolved.

For now, SB 261 imposes no active compliance obligations. 

SB 253: Still Moving Forward

SB 253, by contrast, remains fully operative. The Ninth Circuit has declined to stay the statute, and the hearing did not change that posture. Accordingly:

• Scope 1 and 2 reporting begins in 2026, and
• Scope 3 reporting begins in 2027.

Although the judges examined potential constitutional concerns related to Scope 3 reporting—and even suggested the possibility of limited remand—that discussion did not affect the operative effect of SB 253. Covered companies should continue to prepare for implementation of this statute. 

CARB is drafting implementing regulations for SB 253, and is expected to release proposed rules sometime in early 2026. The implementing regulations are expected to address methodologies for reporting, assurance requirements and fee structures. Once released, the draft regulations are expected to offer the first detailed roadmap for SB 253 compliance and careful legal examination and compliance will be warranted.

The Ninth Circuit’s forthcoming decision will determine whether SB 261 can proceed and whether any portion of SB 253—particularly Scope 3 emissions reporting— will face additional judicial scrutiny. In the meantime, the regulatory landscape remains split: SB 261 is paused; SB 253 is not.

We are monitoring the appeal and CARB’s regulatory developments, and will provide updates when new information becomes available.