A UK-wide sampling programme has found trifluoroacetic acid (TFA), an ultrashort-chain PFAS often described as a 'forever chemical', in 98% of 54 monitoring sites across 32 rivers, with an average concentration of 2,211 ng/L. One River Kelvin (Glasgow) sample reached 78,464 ng/L, reported as among the second-highest surface-water values recorded globally.

The study ran seasonal sampling over a year (summer 2022 through spring 2023) and was published in 2025, providing a detailed picture of how pervasive TFA has become in UK surface waters.

Persistence, mobility and the limits of treatment

TFA is especially challenging because it is highly persistent and highly mobile in water systems. It can form when PFAS break down, including from certain pesticide active substances, and it is also associated with fluorinated gases ('F-gases') and some pharmaceuticals. From a risk management perspective, the researchers note that there are currently limited practical or economically viable methods for removing TFA from water supplies, suggesting that preventing releases ('source control') may be more effective than relying on downstream treatment. 

Regulatory momentum and evolving science

TFA contamination reflects a pattern familiar to insurers, in which widespread contamination coincides with evolving scientific understanding and increasing regulatory attention, giving rise to potential long-tail liability considerations.

In the past 12 months, European institutions have visibly tightened the risk frame. On 22 July 2026, EFSA lowered its acceptable daily intake (ADI) for TFA to 0.014 mg/kg/day (down from 0.05) and set an acute reference dose (ARfD) of 0.07 mg/kg, citing new evidence including thyroid-hormone effects. Meanwhile, ECHA’s risk assessment committee process has been moving toward tougher hazard positioning: A June 2026 RAC update (as reported by ISPRA) states the committee recommended classifying TFA as Reproductive Toxicity Category 1B (H360Df) and recommended PMT/vPvM classifications.

UK regulatory developments

In the UK, government attention to TFA in drinking water is explicit: A Parliamentary answer in July 2025 said the Drinking Water Inspectorate is running a research programme to assess prevalence and treatment efficacy for TFA, coordinated with the Environment Agency and others, signalling that monitoring expectations, and potentially standards, could tighten over time. 

Separately, the Environment Agency published a January 2026 report developing PFAS thresholds for water risk management, reflecting a broader regulatory push that can expand disclosure, sampling, and remediation obligations across industries.

Insurer exposure: What this means for insurers.

• TFA's widespread presence in UK rivers may create environmental and public liability exposure for insurers. If water companies, local authorities, or landowners face claims for monitoring, alternative supply, or environmental harm, they may seek to identify responsible parties, potentially including upstream manufacturers and users of pesticides, refrigerants, and industrial fluorochemicals.
• TFA-related product liability and bodily injury claims represent a potential area of growing insurer exposure. PFAS-related claims globally illustrate how contaminants initially regarded as 'emerging' can develop into significant litigation. In the US, for example, 3M announced a $10.3bn accrual tied to its public water supplier settlement (final court approval announced in 2024), which may be indicative of the potential scale once litigation matures. European regulatory reclassification of TFA including proposed Reproductive Toxicity Category 1B could contribute to similar claims developments in the UK and EU.
• TFA also raises coverage and wording risk, sometimes called 'silent PFAS' exposure. The Lloyd's market has been updating PFAS exclusion language (e.g., LMA model clauses), and many insurers have moved to exclude PFAS-related liabilities more comprehensively-yet legacy occurrence policies can still be tested for historic releases. Insurers should review whether existing pollution, product, and general liability wordings adequately address TFA and related ultrashort-chain PFAS compounds. 
• Because TFA is highly persistent and there are currently limited economically viable removal technologies, remediation costs and timelines may be difficult to estimate with confidence, potentially increasing the severity of claims under environmental and public liability policies.

TFA’s detection in 98% of sampled UK rivers suggests that insurers may need to consider contamination not as a rare, isolated site event with a neat remediation endpoint, but as a potentially systemic and accumulative exposure across many insureds, and multiple lines of business. This may make aggregation across industries, geographies, and policy years a more prominent underwriting and portfolio-management consideration.

In practice, this points to several potential consequences: 

• First, there may be greater emphasis on portfolio-level scenario analysis and stress testing, tighter chemical-use and discharge questionnaires, and deeper scrutiny of wastewater pathways (on-site treatment performance, off-site disposal, sewer connections, trade effluent consents, biosolids handling, and runoff controls). 

• Second, insurers may consider more frequent PFAS/TFA-specific exclusions, sub-limits, higher retentions, and narrower definitions of 'pollution conditions'- especially for accounts connected to pesticides, refrigeration/F-gases, specialty chemicals, and waste handling. 

• Third, ubiquitous detection may increase the prospect of multi-party cost allocation disputes, third-party claims tied to monitoring and alternative supply costs, and 'who knew what, when' coverage arguments, and insurers may in turn look to tighten their approach to policy wording, occurrence/triggers, notice provisions, and long-tail reserving in response. 

• Finally, reinsurance considerations may follow: Cedants could face reinsurer requests for clearer PFAS/TFA exposure mapping, tougher attachments/aggregates, and evidence of active risk-engineering controls before capacity is offered.

To discuss how these developments may affect your book of business, contact Browne Jacobson's insurance and reinsurance sector team.