PFAS endocrine-disrupting chemicals linked to higher odds of thyroid cancer
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Key takeaways:
- Adults exposed to higher levels of linear PFOS are more likely to be diagnosed with thyroid cancer.
- Those exposed to high levels of PFAS should undergo thyroid function screening.
Exposure to a class of endocrine-disrupting chemicals may increase the risk for developing thyroid cancer, according to a study published in eBioMedicine.
In a nested case-control study, researchers analyzed exposure to PFAS among adults diagnosed with thyroid cancer and those without thyroid cancer. Adults had a higher likelihood for developing thyroid cancer with greater exposure to linear PFOS, and increased risks for thyroid cancer were observed with exposure to five types of PFAS for adults diagnosed more than 1 year after plasma samples were collected.
“We think that is important to raise the general awareness of the potential negative health impacts of PFAS chemicals,” Maaike van Gerwen, MD, PhD, assistant professor and director of research in the department of otolaryngology – head and neck surgery, and Lauren Petrick, PhD, assistant professor in the department of environmental medicine and public health at the Icahn School of Medicine at Mount Sinai, told Healio. “Our study results confirm that current actions by the U.S. Environmental Protection Agency to monitor and set limits for PFAS in drinking water are important, but may need to be expanded to removing PFAS from potential exposure sources, including drinking water and consumer products.”
Van Gerwen, Petrick and colleagues obtained data from 88 people with thyroid cancer who had a plasma sample collected prior to diagnosis (mean age, 46 years; 83% women). Data were collected from a medical record-linked biobank at the Icahn School of Medicine at Mount Sinai. Adults with thyroid cancer were matched by sex, age, race and ethnicity, BMI and smoking status with 88 adults who did not have thyroid cancer. Researchers included eight types of PFAS in the analysis.
Of the thyroid cancer group, 84% were diagnosed with papillary thyroid cancer, 5% had follicular thyroid cancer and 10% had thyroid cancer of unknown histology.
Adults had an increased likelihood for being diagnosed with thyroid cancer with each doubling of linear PFOS concentration (adjusted OR = 1.56; 95% CI, 1.17-2.15; P = .004). No associations were observed with other types of PFAS. The odds for developing papillary thyroid cancer were also higher with each doubling of linear PFOS intensity (aOR = 1.56; 95% CI, 1.13-2.21; P = .009).
In a sensitivity analysis, researchers analyzed associations for 31 adults diagnosed with thyroid cancer 1 year or later after plasma collection compared with their matched controls. Among the subgroup, each doubling of linear PFOS concentration (aOR = 2.67; 95% CI, 1.59-4.88; P = .002), branched PFOS level (aOR = 3.09; 95% CI, 1.73-6.13 P = .002), PFNA concentration (aOR = 2.22; 95% CI, 1.19-4.28; P = .02), PFOPA level (aOR = 2.03; 95% CI, 1.32-3.27; P = .004) and linear PFHxS concentration (aOR = 2.1; 95% CI, 1.36-3.37; P = .003) was associated with a higher likelihood for developing thyroid cancer. Among 57 adults who developed thyroid cancer less than 1 year after plasma sample collection, only linear PFOS was associated with increased odds for thyroid cancer (aOR = 1.45; 95% CI, 1.07-2.01; P = .02).
“The National Academies of Sciences, Engineering, and Medicine currently recommends testing for PFAS in patients with a history of high PFAS exposure followed by thyroid function testing if an adult patient would have high PFAS concentrations of 20 ng/mL or more,” Petrick and van Gerwen said. “Our study findings underwrite these recommendations and may indicate that high PFAS exposure warrants further surveillance. Clinicians treating patients with known high exposure levels of PFAS should take this into consideration when personalizing the management plan.”
Petrick and van Gerwen said more studies are needed to understand the mechanisms of how PFAS exposure may increase thyroid cancer risk. They also said a repeat study is needed with a larger sample size to confirm the findings.
For more information:
Lauren Petrick, PhD, can be reached at lauren.petrick@mssm.edu.
Maaike van Gerwen, MD, PhD, can be reached at maaike.vangerwen@mountsinai.org.
Perspective
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This nested case-control study found that higher PFAS exposures were associated with thyroid cancer diagnosis for six of the chemicals assessed. Only limited information is provided about the thyroid cancers included in this study; tumor size and staging are not described and would be of interest. Controls did not have diagnosed thyroid cancers, but given the high prevalence of occult papillary microcarcinoma in the general population, some misclassification is possible. Groups were matched for BMI, sex, age, race and smoking status, although some potentially important covariates, including thyroid function, were not assessed.
Overall, these data add to the growing body of evidence for adverse health effects of PFAS exposure. Earlier this year, the U.S. Environmental Protection Agency announced proposed regulation of six PFAS chemicals, including some of those associated with thyroid cancer in this study, in drinking water. However, these are “forever” chemicals which are highly persistent in the environment, and it is likely that widespread population exposure will continue. The National Academies of Sciences, Engineering, and Medicine have released guidance recommending monitoring of TSH annually in adult patients with the highest serum PFAS levels, although in most clinical settings PFAS testing is not covered by insurance. It is not clear whether thyroid cancer screening for individuals with high PFAS exposure would be beneficial, and larger studies with well-characterized thyroid cancers will ultimately be needed to better understand risks and inform clinical recommendations.
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