Risk of Cancer in a Community Exposed to Per- and Poly-Fluoroalkyl Substances

Our plain-English summary of Risk of Cancer in a Community Exposed to Per- and Poly-Fluoroalkyl Substances, by M.F. Messmer, J. Salloway, N. Shara, et al (Environmental Health Insights, 2022).

The study

• Authors: M.F. Messmer, J. Salloway, N. Shara, B. Locwin, M.W. Harvey, N. Traviss
• Journal: Environmental Health Insights
• Published: 2022;16:11786302221076707
• Cited by: 48 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

Background: Per- and polyfluoroalkyl substances (PFAS) emissions from a plastic coating industrial source in southern New Hampshire (NH) have contaminated at least 65 square miles of drinking water. Prior research indicates that high levels of PFAS are associated with a variety of adverse health outcomes, including an increased risk of cancer. Reports indicate that mean blood serum levels of perfluorooctanoic acid (PFOA), one type of PFAS, in residents of the exposed community are more than 2 times greater than the mean blood serum level in the US. Merrimack public water supply customers also have higher average blood levels of perfluorooctane sulfonic acid (PFOS) and perfluorohexane sulfonic acid (PFHxS) than the time-matched US average. A 2018 report concludes that the incidence rate of cancer in Merrimack does not exceed the incidence rate of cancer in NH in general. However, prior reporting on the risk of cancer in Merrimack is compared only to a state-wide metric influenced by the Merrimack cancer incidence.

Methods: Our ecological study compared the risk in Merrimack, NH residents for 24 types of cancer between 2005 and 2014, targeted in a previous study, and all-cause cancers, to US national cancer rates and cancer rates in demographically similar towns in New England. Four New England "unexposed towns" were chosen based on demographic similarity to Merrimack, with no documented PFAS exposure in water supplies. We utilized unadjusted logistical regression to approximate risk ratios (RR) and 95% confidence intervals (CI) assessing the risk of cancer in Merrimack NH to each of the 4 comparator communities, the pooled comparator variable, and national average incidence.

Results: Residents of Merrimack, NH experienced a significantly higher risk of thyroid cancer (RR = 1.47, 95% CI 1.12-1.93), bladder cancer (RR = 1.45, 95% CI 1.17-1.81), esophageal cancer (RR = 1.71, 95% CI 1.1-2.65), and mesothelioma (RR = 2.41, 95% CI 1.09-5.34), compared to national averages. Our work also suggests that Merrimack residents experienced a significantly higher risk of all-cause cancer (RR = 1.34, 95% CI 1.25-1.43), thyroid cancer (RR = 1.69, 95% CI 1.19-2.39), colon cancer (RR = 1.27, 95% CI 1.02-1.57), and prostate cancer (RR = 1.36, 95% CI 1.15, 1.6) compared with similarly exposed New England communities. Our results indicate that residents of Merrimack may also have a significantly lower risk of some site-specific cancers compared to national averages, including lower risk of prostate cancer (RR = 0.57, 95% CI 0.5-0.66), female breast cancer (RR = 0.60, 95% CI 0.52-0.68), ovarian cancer (RR = 0.52, 95% CI 0.33-0.84) and cervical cancer (RR = 0.29, 95% CI 0.12-0.69).

Conclusion: Merrimack residents experienced a significantly higher risk of at least 4 types of cancer over 10 years between 2005 and 2014. Merrimack is a community with documented PFAS contamination of drinking water in public and private water sources. Results indicate that further research is warranted to elucidate if southern NH residents experience increased risk for various types of cancer due to exposure to PFAS contamination.

© The Author(s) 2022.

In plain English

This ecological study was about PFAS chemicals, not asbestos. It compared cancer incidence in Merrimack, New Hampshire, where PFAS from a plastics plant contaminated drinking water, with US rates and four New England towns without documented PFAS contamination. It covered 24 cancer types and all-cause cancer from 2005 to 2014, or 2005 to 2013 for lung and bronchus and prostate cancer. Compared with the US average, Merrimack residents had a higher risk of mesothelioma (RR 2.41, 95% CI 1.09-5.34) and of thyroid, esophageal and bladder cancer. They had a lower risk of all-cause, prostate, female breast, ovarian and cervical cancer. Compared with the four towns pooled, they had higher risks of all-cause cancer (RR 1.34, 95% CI 1.25-1.43) and of thyroid, colon and prostate cancer. The mesothelioma difference against the pooled towns was not statistically significant (RR 1.33, 95% CI 0.50-3.55). Merrimack had only 6 mesothelioma cases. The authors said the mesothelioma result may be subject to type 1 error and that a regional factor such as asbestos exposure could not be ruled out. Individual risk factors were unknown. The authors concluded that further research is warranted.

We wrote this plain-English summary from the full article with the help of AI, and a second AI model checked each sentence against the article. It is not the authors' wording; the abstract and the article are their own account.

What the study did and found

• Design: Ecological study using publicly available cancer incidence data, with unadjusted logistic regressions to approximate risk ratios
• Who was studied: Residents of Merrimack, NH (population 25 494 in 2010), cancer incidence 2005 to 2014 (2005 to 2013 for lung and bronchus and prostate cancer). They were compared with Sanford, Auburn and South Portland, Maine, and Colchester, Vermont (separately and pooled), and with US average incidence. Bennington, Vermont, a town with documented PFAS contamination, was used in sensitivity analyses. Vermont towns had data for only 7 cancer types plus all-cause cancer.
• Exposure: Per- and polyfluoroalkyl substances (PFAS), mainly PFOA, in drinking water and air emissions from the Saint Gobain Performance Plastics plant in Merrimack. PFOA in Merrimack well MW-4 was listed at 140 parts per trillion. Asbestos exposure was not measured.
• Main results:
  • Merrimack residents compared with US average incidence: mesothelioma RR 2.41, 95% CI 1.09-5.34 (described as 141% higher risk)
  • The authors noted that the precision estimate for the mesothelioma result against the US average was greater than 1.0, so the result may be a type 1 error (a false positive)
  • Merrimack mesothelioma risk compared with the pooled four towns was not statistically significant: RR 1.33, 95% CI 0.50-3.55
  • There were only 6 mesothelioma cases in Merrimack
  • Merrimack residents compared with US average: thyroid cancer RR 1.47 (95% CI 1.12-1.93), esophageal cancer RR 1.71 (95% CI 1.1-2.65), bladder cancer RR 1.45 (95% CI 1.17-1.81)
  • Merrimack residents compared with US average had lower risks of all-cause cancer (RR 0.86, 95% CI 0.82-0.91), prostate cancer (RR 0.57), female breast cancer (RR 0.60), ovarian cancer (RR 0.52, 95% CI 0.33-0.84) and cervical cancer (RR 0.29, 95% CI 0.12-0.69)
  • Merrimack residents compared with the pooled four towns: all-cause cancer RR 1.34 (95% CI 1.25-1.43), thyroid RR 1.69 (95% CI 1.19-2.39), colon RR 1.27 (95% CI 1.02-1.57), prostate RR 1.36 (95% CI 1.15-1.6). Lung and bronchus cancer was lower (RR 0.69, 95% CI 0.58-0.83).
  • Sensitivity analysis comparing Merrimack with Bennington, VT: Merrimack had lower lung and bronchus cancer (RR 0.42, 95% CI 0.33-0.52) and non-Hodgkin lymphoma (RR 0.56, 95% CI 0.38-0.83), and no significant difference for the other available cancer types
• The authors' conclusion: The authors concluded that Merrimack residents had significantly higher rates of mesothelioma and of esophageal, thyroid and bladder cancers than US incidence rates in 2005 to 2014. They concluded that further research, including case-control and cohort studies, is warranted.
• Limitations the authors state:
  • For mesothelioma, the authors stated that a regional factor such as asbestos exposure cannot be ruled out
  • Merrimack could not be compared with New Hampshire state rates or other time periods because the data are not publicly available
  • Delays in cancer reporting may lead to underestimation of prostate and lung and bronchus cancer
  • Unrecognized PFAS or other environmental exposures in the comparison towns may lead to underestimation of Merrimack's risk
  • The many comparisons mean type 1 error cannot be ruled out
  • Because the study used population-level data, comorbid, behavioral and other individual risk factors are unknown
  • Town-level data for all 24 cancers were not available for the Vermont towns, so only 7 cancer types were compared

Topics

Medical terms in this study, explained in our Lexicon: Incidence, confidence interval, Esophageal Cancer, Mesothelioma, Colorectal Cancer, Ovarian Cancer.

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