Indoor Environment as the Next Mass Tort: PFAS, Mold and Rental Housing Litigation

The U.S. Environmental Protection Agency (EPA) under Administrator Lee Zeldin has announced sweeping deregulation with a "compliance first" approach. Though this may appear to be a reprieve, the retreat of federal enforcement is accelerating private environmental litigation through citizen suit provisions and creative tort theories.

Plaintiffs' firms have accelerated nuisance, negligence and consumer protection class actions targeting indoor environments. A growing wave of "sick building" lawsuits relies on contested diagnoses such as Chronic Inflammatory Response Syndrome (CIRS) – conditions lacking mainstream medical recognition.

Why Deregulation Is Fueling, Not Reducing, Litigation

Reduced regulatory oversight does not reduce legal exposure:

• Uncertain Exposure Thresholds. Without clear standards, courts and juries decide what constitutes "reasonable" exposure – often favoring plaintiffs.
• Courts Filling Gaps. Judges increasingly see themselves as a last line of defense, as reflected in recent California and New Jersey rulings expanding premises liability for environmental conditions.
• Loss of Safe Harbors. When standards are rolled back, defendants lose the "we met government requirements" defense.
• Narrative Advantage. Post-verdict interviews and focus-group research confirm that juries are receptive to "the government isn't protecting us" themes.

Per- and polyfluoroalkyl substances (PFAS) and mold claims borrow from prior mass-tort playbooks, including lead paint (long latency, causation challenges) and Chinese drywall (rapid multistate scaling).

PFAS: The Benchmark Mass Tort

PFAS litigation has become one of the largest environmental mass torts, with more than 15,000 personal injury lawsuits pending in MDL 2873 (formally known as the Aqueous Film-Forming Foams (AFFF) Products Liability Litigation, this multidistrict litigation involves claims of environmental and health damages caused by PFAS-containing firefighting foams) and healthcare costs estimated at $37 billion to $59 billion annually.

The regulatory landscape is complicated by thousands of distinct PFAS compounds with different toxicity profiles. Long-chain compounds – such as perfluorooctanoic acid (PFOA) and perfluorooctanesulfonic acid (PFOS) – have received the most attention as a result of greater toxicity and environmental persistence.

Municipal settlements have generated more than $12 billion, including New Jersey's $875 million settlement in August 2025. Personal injury bellwethers expected in 2026 project settlements between $75,000 and $600,000 based on plaintiff-side valuation models and comparable toxic tort benchmarks.

The EPA finalized a maximum contaminant level for PFOS and PFOA in April 2024 but extended compliance to 2029 – acknowledging health risks while not yet requiring remediation. This exposes housing owners to claims that they knew of contamination yet failed to act.

Mold and Indoor Air Quality: The Immediate Portfolio Threat

Though PFAS dominates headlines, mold and indoor air quality (IAQ) claims may pose more immediate exposure for residential portfolio owners because of shorter latency periods and lower causation burdens. Major health organizations have not accepted "toxic mold syndrome" or CIRS as validated diagnoses, creating both risk (emotionally compelling theories) and opportunity (Daubert/Rule 702 defenses).

The Pseudo‑Science Ecosystem Behind Mold Claims

Many mold lawsuits follow a predictable pattern: Wellness media promotes "toxic mold" narratives, patients seek "mold literate" practitioners using proprietary diagnostics, and plaintiffs' lawyers rely on this ecosystem for causation theories. This model is vulnerable to challenge, relying on unvalidated criteria and methodologies rejected by mainstream medicine.

Structural Drivers: Aging Stock, Public Housing and Legacy Hazards

The legal theories – toxic tort, negligence and habitability – are familiar, but risk is concentrating. Pre‑1980s construction often involves lead, asbestos and mold‑prone materials. In addition, public housing tends to have outdated heating, ventilation and air conditioning (HVAC), and more than 9,000 federally subsidized developments are within 1 mile of a Superfund site.

Privatized Military Housing: A Preview of Civilian Multifamily Claims

Litigation against privatized military housing previews issues for civilian portfolios. In Texas, families have sued over mold, pest infestations and painting over mold. Similar patterns are emerging in civilian complexes, establishing templates deployable against real estate investment trusts (REITs) and institutional owners.

Jurisdictional Risk: Where Portfolios Are Most Exposed

Not all venues present equal risk. California leads in mold litigation with plaintiff‑friendly outcomes. New Jersey is a PFAS hotspot after its $875 million settlement. Texas has seen substantial military housing litigation. Florida combines humid conditions and aging stock, attractive for linking symptoms to indoor exposures.

Beyond Negligence: Expanding Liability Theories

Plaintiffs are pursuing public nuisance (borrowing from opioid playbooks), consumer protection claims with statutory damages, fraud-supporting punitive damages, expanded habitability warranties and statutory tenant protection claims seeking rent abatement and penalties.

Third‑Party Litigation Funding: More Staying Power for Plaintiffs

Third‑party litigation funding allows plaintiffs' firms to carry multiyear cases without self‑funding. Funded cases have undergone rigorous diligence, and funders' return structures incentivize resistance to early settlements. This means less attrition, more cases through trial and settlement dynamics influenced by funder expectations.

ESG, Capital and Reputation: Parallel Accountability Tracks

For large housing providers accessing institutional capital, these risks appear on environmental, social and governance (ESG) and credit risk dashboards. ESG frameworks scrutinize remediation practices, lenders embed environmental risk into underwriting, and negative coverage can damage entire ownership models.

The Near Term: What Sophisticated Defendants Should Anticipate

1. PFAS Personal Injury Acceleration: Bellwether outcomes in 2026 will frame settlement values for more than 15,000 pending cases.
2. Class vs. Single-Plaintiff Dynamics for Large Portfolios: Class risk is highest where plaintiffs allege systemic failures: standardized maintenance protocols ignoring mold or portfolio‑wide HVAC deficiencies. Single‑plaintiff risk dominates where exposure varies unit to unit, often featuring aggressive damages theories unconstrained by class commonality.
3. Expansion of Residential IAQ and Legacy Contamination Claims: Plaintiffs' firms are developing IAQ and legacy contamination class theories, aided by the absence of federal mold standards.
4. Increasing Sophistication in Causation Evidence: PFAS cases require reconstructing decades of exposure and linking compounds to conditions, including kidney and testicular cancers.

Causation proof in indoor PFAS cases is difficult for plaintiffs because humans are exposed to PFAS through numerous pathways – food, drinking water, consumer products and ambient air. Defendants should emphasize the ubiquity of exposure and absence of reliable methods to attribute health effects to any single source.

Regulatory Compliance, Condition Audits and Third-Party Certification

Robust compliance and documentation remain defensive assets. Proactive audits targeting mold, IAQ and legacy contaminants enable remediation before claims arise, generate good‑faith evidence and support limitations defenses. Third-party healthy building certifications – such as WELL, Fitwel and UL Verified Healthy Building – demonstrate due diligence and alignment with standards of care.

Maintenance Data Integrity

Portfolios should audit ticketing systems for accuracy and align contractor incentives with durable fixes rather than metrics‑driven closure.

Insurance Coverage: The Pollution‑Exclusion Battle

Indoor environment claims implicate general liability, environmental liability and professional liability policies. Courts are divided on whether mold constitutes a "pollutant," and PFAS coverage may face sub‑limits or exclusions. Portfolio‑wide insurance audits are recommended, including policy archaeology to locate historical policies with favorable terms.

How Holland & Knight Can Help

The retreat of federal enforcement is not eliminating environmental liability; it is reallocating it from regulators to juries. Organizations that treat the indoor environment as a core enterprise‑risk category and invest early in science-based defenses and documentation will be better positioned in this next mass‑tort wave.

Holland & Knight's Litigation and Dispute Resolution Practice and Environmental Team have defended property owners in toxic‑tort and environmental disputes across key exposure jurisdictions, including California, New Jersey, Texas and Florida. Our track record includes successfully excluding plaintiff expert testimony under Daubert/Rule 702, avoiding class certification in portfolio-wide habitability claims and coordinating multijurisdictional defense for national multifamily owners. We advise clients on proactive mitigation – from audit protocols to insurance positioning – before claims materialize.

If you have questions or need assistance for your business, contact the authors.

Information contained in this alert is for the general education and knowledge of our readers. It is not designed to be, and should not be used as, the sole source of information when analyzing and resolving a legal problem, and it should not be substituted for legal advice, which relies on a specific factual analysis. Moreover, the laws of each jurisdiction are different and are constantly changing. This information is not intended to create, and receipt of it does not constitute, an attorney-client relationship. If you have specific questions regarding a particular fact situation, we urge you to consult the authors of this publication, your Holland & Knight representative or other competent legal counsel.