Board of Health: Second round of beach sampling finds PFAS concentrated in seafoam; residents advised to avoid contact

The Nantucket Board of Health heard an update Oct. 16 on the town's second round of bathing-beach sampling for per- and polyfluoroalkyl substances (PFAS), with consultants reporting that surface-water measurements were below state screening levels but foam samples contained higher PFAS concentrations.

Rebecca DeVries, a scientist with Eastern Research Group (ERG), told the board the team collected surface-water samples at 18 locations and foam where enough material was present. "All of the surface water results from August fall below that screening value [20 nanograms per liter], indicating that no additional action is needed," DeVries said. She added that laboratory flags and small sample volumes limited some foam analyses, but that foam concentrations remained elevated compared with surface water.

The board's environmental contamination administrator, Andrew Shapiro, said the town followed validated laboratory methods and used PACE Analytical Services in East Longmeadow, Massachusetts, for testing. Shapiro said field blanks and duplicate samples were collected to check sampling methods; the blanks showed no PFAS contamination from sampling materials.

Why it matters: PFAS are persistent chemicals associated with health risks at some exposure levels. The Massachusetts Department of Public Health (DPH) recommends an initial screening value of 20 nanograms per liter for an eight-compound PFAS suite used for bathing-beach guidance; town surface-water results were below that value, but foam—where PFAS can concentrate—showed elevated levels in both sampling rounds.

Key details from the ERG presentation:
- Surface water: PFAS were not detected at 11 of 18 sites; the most frequently found compound in detections was PFOA, and all detected surface-water results remained below the DPH 20 ng/L screening benchmark. Some PFAS without established screening values (PFOSA, PFHPA) were detected at low levels.
- Foam: Two foam samples (from Madaket/Manuket Harbor and Sasatchicka Pond) contained multiple PFAS and higher concentrations than paired surface-water samples. Some foam results were flagged by the lab because the post-collapse liquid volume was below the laboratory's preferred 500 mL and because of organic material in samples. DeVries said foam results this round were generally lower than July's but still high enough to warrant caution.

Actions and next steps: DeVries and Shapiro urged residents and visitors to avoid direct contact with foam on beaches. The board and consultants scheduled two public outreach events: Nov. 17, a presentation by Dr. Laurel Schader of the Silent Spring Institute on everyday PFAS exposures; and Dec. 11, a presentation by Dr. Tamara James Todd of the Harvard T.H. Chan School of Public Health on health effects of PFAS exposures. ERG will provide a more comprehensive evaluation in January once data from both sampling rounds are analyzed together.

Quotes in context: "No PFAS were detected in those [field] blanks either, which confirmed to us that the bags aren't contributing any PFAS to our sample results," DeVries said when explaining quality-control checks. Shapiro described the upcoming community briefings as "a chance to hear from some world renowned experts on PFAS."

What remains uncertain: Laboratory qualifiers on some foam samples and the limited liquid volume available for analysis mean the town will rely on the January report to synthesize both sampling rounds and finalize recommendations.