Elevated Kidney Cancer Rates in Merrimack and Manchester

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Correction and update, Sept. 19, 2026, 3:16 p.m. EDT: An earlier version of this article said the Dartmouth research was presented “this week,” that kidney cancer in Merrimack was “significantly” higher than expected, and that state testing “tied” the region’s PFAS contamination to Saint-Gobain emissions. It also cited the wrong New Hampshire Bulletin story on soil handling in Merrimack. In fact, the research was presented to the Commission on Environmental and Public Health Impacts of Perfluorinated Chemicals on October 10, 2025; the New Hampshire Bulletin reported a 38% excess without describing its statistical significance; and the state has blamed the company for contaminating air and water, a link the Dartmouth study did not test (New Hampshire Bulletin). We corrected those passages, added the date and evidence levels of the IARC classifications, and updated the drinking-water section with the EPA’s May 18, 2026 proposals to allow PFOA and PFOS compliance extensions to 2031 and to rescind limits for four other PFAS (EPA).

By Granite State Report

Research presented to the Commission on Environmental and Public Health Impacts of Perfluorinated Chemicals on October 10, 2025, confirms what many families in southern New Hampshire have suspected for years: kidney cancer diagnoses in Merrimack are higher than expected, and Manchester may have a second possible cluster. The findings revive urgent questions about long-standing PFAS (“forever chemicals”) contamination and what state and local leaders will do next.

What’s new

Megan Romano, an associate professor of epidemiology at Dartmouth’s Geisel School of Medicine, presented her team’s findings: Merrimack saw a 38% excess of kidney cancer cases from 2013–2021, with an additional 18% excess in Manchester over the same period. Hudson had an 83% excess in 1995–2003 that later returned to expected levels. The researchers emphasized the study confirms elevated rates but does not determine a cause; more funding and granular exposure data are needed. (New Hampshire Bulletin)

Why it matters

PFAS were found in 2016 in hundreds of wells around the Saint-Gobain Performance Plastics facility in Merrimack, and the state has long blamed the company for contaminating air and water in Merrimack, Londonderry, Bedford, Litchfield and Hudson. Under a 2022 consent decree, the company agreed to provide clean drinking water to about 1,000 homes. Saint-Gobain announced in 2023 that it would close the plant, which had operated since 1986, and completed demolition in July 2025. Long-term cleanup and exposure histories remain complex. (New Hampshire Bulletin)

In December 2023, the World Health Organization’s cancer agency, IARC, classified PFOA (a common PFAS) as carcinogenic to humans (Group 1) and PFOS as possibly carcinogenic (Group 2B). The PFOA rating rested on sufficient evidence in experimental animals and strong mechanistic evidence in exposed humans; IARC found “limited evidence for cancer in humans,” naming renal cell carcinoma, a kidney cancer, and testicular cancer. IARC says its classifications describe the strength of evidence that a substance can cause cancer, not the level of risk at a given exposure. (IARC)

In April 2024, the EPA finalized the first national drinking-water limits for six PFAS, giving public water systems until 2029 to comply. In May 2025, the agency said it would keep the limits for PFOA and PFOS but planned to rescind the limits for PFHxS, PFNA, HFPO-DA (known as GenX) and a combined limit for mixtures. On May 18, 2026, the EPA proposed a rule that would let water systems request two more years, to 2031, to meet the PFOA and PFOS limits, and a separate rule to rescind the other four; public comment on both closed July 20, 2026. New Hampshire’s own PFAS drinking-water standards took effect September 30, 2019. (Environmental Protection Agency; NHDES)

What the data show (and don’t)

The Dartmouth team used the New Hampshire State Cancer Registry to compare kidney cancer rates in Merrimack and eight surrounding towns against the rest of the state across three time windows. The signal in Merrimack (2013–2021) is consistent with earlier New Hampshire DHHS work that also found a statistically significant excess and recommended deeper study. The new analysis additionally flags Manchester’s excess—especially among women—while urging caution until more detail is available. (New Hampshire Bulletin)

Researchers say the next step is to link people’s residential histories and water testing records to exposure data—work that is doable but intensive and dependent on sustained funding. (New Hampshire Bulletin)

Community context

Residents have long pointed to PFAS as a possible cause. NHDES and local activists say the Saint-Gobain plant released PFAS into the air for decades, but the Dartmouth analysis did not test whether that exposure explains the kidney cancer excess. While the plant is gone, the remediation picture is unfinished; construction in parts of Merrimack is complicated because contaminated soil is being kept in place, and state Rep. Rosemarie Rung has said there are no clear regulations for managing soil that must be removed. (New Hampshire Bulletin, Sept. 29, 2025; New Hampshire Bulletin, Oct. 17, 2025)

What Granite Staters can do

If you’re on a private well: NHDES recommends testing a residential well for PFAS if it has not been tested before, and residents can ask NHDES to sample their well for PFAS at no cost. If levels exceed drinking-water standards, check the NHDES PFAS Removal Rebate Program for Private Wells for whether applications are being accepted. (NHDES private-well guidance)
If you want to understand the cancer data: The New Hampshire DHHS Cancer Incidence Report, Merrimack, NH (January 2023) counted 66 kidney cancer cases in Merrimack from 2009 to 2018 against 46.49 expected, a standardized incidence ratio (SIR) of 1.42. The report says it does not assess exposure to PFAS or other chemicals and cannot connect any exposure to the cancers. (dhhs.nh.gov)
If you’re on public water: Under the 2024 EPA rule, public water systems must meet the PFOA and PFOS limits by 2029; a May 2026 EPA proposal would let systems request more time, to April 2031. Watch for monitoring notices and treatment updates from your utility. (Environmental Protection Agency)

What to watch next

Whether state and federal partners fund the expanded exposure-history study researchers say is necessary to test environmental links. (New Hampshire Bulletin)
How NHDES implements PFAS treatment projects and soil management around Merrimack and Manchester, and whether additional community health surveillance is added. (New Hampshire Bulletin)
Whether the EPA finalizes its May 2026 proposals on PFAS compliance deadlines and rescissions, and how utilities schedule treatment upgrades. (Environmental Protection Agency)

Watch: explainers and local meetings (YouTube)

NHDES: Town of Merrimack PFAS informational meeting, May 25, 2021 (Merrimack TV): https://www.youtube.com/watch?v=YUdHZZAJOAw
Dana-Farber explainer: “What is the connection between PFAS and cancer?” https://www.youtube.com/watch?v=Nfxu1gWxzDE
Merrimack TV: NHDES PFAS virtual public meeting, February 2, 2022: https://www.youtube.com/watch?v=8EzVNSCgu0g
A broader science explainer on PFAS persistence and exposure pathways (Veritasium): https://www.youtube.com/watch?v=SC2eSujzrUY

Corrections: Granite State Report corrects verified errors promptly and appends a dated note identifying what changed and when. The corrections policy and the corrections register are public, and correction notes are never removed.