Harvard researcher: PFAS linked to immune, reproductive and metabolic harms; NASEM offers testing guidance

Dr. Tamara James Todd, a professor of environmental reproductive epidemiology at the Harvard T.H. Chan School of Public Health, told a Nantucket public information session that per- and polyfluoroalkyl substances (PFAS) are "forever chemicals" with growing evidence linking them to health harms across life stages. She said the literature has expanded rapidly — from a few dozen studies two decades ago to more than a thousand by the end of 2024 — and now supports specific clinical and community responses.

Todd reviewed laboratory and epidemiologic findings showing PFAS can bioaccumulate and affect multiple organs. She described associations found in meta-analyses and cohort studies between higher PFAS levels and lower birth weight and preterm birth, immune effects including lower measles and rubella antibody titers, changes in lipid metabolism and higher cholesterol, lower bone mineral density in adolescence (with some sex differences), increased risks of gestational hypertension and, in some analyses, preeclampsia, and links to kidney, testicular and other cancers. She emphasized that many studies are observational and that timing of exposure (prenatal vs. postnatal) and mixtures of different PFAS influence results.

Todd highlighted the 2022 National Academies of Sciences, Engineering, and Medicine (NASEM) committee that issued principles for clinical evaluation and testing. She summarized the committee's practical thresholds discussed in the report: under 2 nanograms per milliliter (ng/ml) suggests routine care; 2–<20 ng/ml suggests encouraging exposure reduction when a source is known and considering targeted screening for pregnant people and others at elevated risk; and >20 ng/ml prompts stronger exposure-reduction recommendations and individualized clinical follow-up. She cautioned that those thresholds reflect the committee's deliberations and the level of uncertainty in the evidence.

On immune outcomes, Todd said several well-conducted studies report that higher PFOA or related PFAS are associated with reduced vaccine antibody titers and more childhood infections; she recommended clinicians consider antibody-titer testing when community exposure is high and to involve pediatricians and regional Pediatric Environmental Health Specialty Units in planning responses.

Todd also discussed exposure-reduction strategies individuals and communities can pursue: testing private wells; using certified point-of-use filters that are appropriate for PFAS removal (without endorsing specific brands); avoiding stain- and grease-resistant textiles; reducing use of nonstick cookware; minimizing products that shed dust; and advocating that retailers carry safer alternatives. She said engineering research is progressing on filter disposal and 'cradle-to-grave' solutions to avoid moving contaminants downstream.

Todd urged continued local engagement, offering Harvard's community-engagement resources and pointing to publicly available materials from PFAS research centers and outreach networks. The session ended with an announcement that the town will present surface-water sampling results in January, and with a commitment from Todd to continue the dialogue with local clinicians and community groups.