Documented cancer risks from exposure previously centered on a short list. This list included kidney cancer, testicular cancer, and blood cancers. These connections appeared most clearly in worker populations and communities living near major chemical manufacturing sites. They shaped the regulatory conversation around PFAS. A new study in January 2025 in the Journal of Exposure Science & Environmental Epidemiology calls this into question. The National Institutes of Health funded this research. The medical team from USC systematically examined drinking water alongside national cancer incidence. The cancer associations they discovered went beyond the familiar short list.
The Study’s Design
Researchers utilized two large national datasets. The National Cancer Institute tracks cases across 22 registries. This program covers roughly half the United States population. The EPA Unregulated Contaminant Monitoring Rule provided the second dataset. This rule records chemical concentrations measured at public water systems. The team compared county cancer rates against measured water chemical levels. They controlled for age, sex, and socioeconomic status. They also controlled for smoking rates, obesity, and air pollution. They used Poisson regression models. Scientists use this standard tool for count based epidemiological analysis. The ecological design uses population data rather than individual records. The researchers acknowledge this limitation carefully. Ecological studies identify patterns and generate hypotheses. They cannot prove causation at the individual level.
What the Study Found
Counties with contaminated drinking water showed higher cancer rates. These cancers affected the digestive, endocrine, oral, and respiratory systems. A compound called PFBS showed the strongest single association. Affected counties experienced a 33 percent higher incidence rate of mouth and throat cancers. The findings varied by sex. Male exposure increased risks for urinary, brain, and soft tissue cancers. It also increased leukemia risks. Female exposure showed strong associations with thyroid cancer. Mouth, throat, and soft tissue cancers also showed strong associations. Researchers had never previously studied several of these cancer types regarding chemical exposure. Researchers estimate that drinking water contamination causes thousands of new cancer cases annually in the United States.
The Focus on PFBS
Perfluorobutanesulfonic acid (PFBS) is a PFAS that deserves particular attention. Its regulatory history illustrates how manufacturers try escaping regulation. Manufacturers phased PFOS out of production in the early 2000s following toxicity evidence. Chemical companies then introduced shorter carbon chain replacements. PFBS was one of them. Companies initially promoted shorter molecules as safer alternatives. Theorists believed their smaller size would prevent bodily accumulation. However, less bioaccumulative does not equal safe. The USC study found PFBS carried the strongest cancer association. The EPA proposed rescinding drinking water standards for PFBS in 2025.
What Water System Directors Should Take from this Study
The study reinforces a longstanding scientific point. Health consequences extend well beyond the cancers driving early litigation. Original regulatory assessments completely ignored mouth, throat, brain, and thyroid cancers. PFOA and PFOS are not the only chemicals harming communities. A wide range of these chemicals causes harm at various concentrations. Systems must test broadly and treat effectively. They must hold manufacturers accountable for full contamination costs. This approach protects ratepayers completely. For information on how public water systems can pursue PFAS claims against chemical manufacturers, see Stag Liuzza’s PFAS litigation overview.