Do Forever Chemicals Raise the Risk for Thyroid Cancer?

You have no doubt heard about “forever chemicals,” per- and polyfluoroalkyl compounds. Scientists shorten this chemical terminology to the acronym PFAS. Since the 1940s, manufacturers have used PFAS in nonstick pots and pans, food packaging, stain-resistant carpets and fabrics, as well as water-repellent shoes and outerwear. Such forever chemicals are found in air, soil and drinking water. We call them forever chemicals because they do not break down easily. As a consequence, they will persist in our environment—and in us—for decades. These compounds may cause deleterious changes in liver function, increased cholesterol levels, elevations in blood pressure and reduced fertility. Should we include thyroid cancer–or indeed any cancer–in this list?

PFAS Contamination Is Linked to Cancer Rates:

A recent study measured the levels of various types of PFAS in municipal water on a county-by-county basis (Journal of Exposure Science and Environmental Epidemiology, Jan. 9, 2025). The researchers then tracked the occurrence of specific cancers in those counties.

According to the investigators, approximately 4,000 to 7,000 excess cancers each year should be attributed to PFAS exposure. Males and females respond somewhat differently, however. Males in counties with contaminated drinking water are more susceptible to leukemia and cancers of the brain, soft tissues and urinary tract. Females are more likely to experience mouth, throat or thyroid cancer as well as malignancies of soft tissues. The scientists urge regulators to monitor and possibly regulate these persistent compounds more intensively.

Do PFAS Increase the Likelihood of Thyroid Cancer?

One study suggests that forever chemicals may also increase the risk for thyroid cancer (eBioMedicine, Oct. 24, 2023). Currently, approximately 45,000 American adults develop this cancer each year. While doctors can treat it successfully if it is diagnosed promptly, the incidence of this malignancy has been rising worldwide. Researchers suspect that exposure to PFAS chemicals may be partly to blame.

In the new investigation, scientists analyzed blood samples from 88 patients with and 88 individuals without thyroid cancer. They completed chemical analyses of eight different specific PFAS compounds.

Those with higher levels of PFAS in their bodies “showed a 56% increased risk of thyroid cancer diagnosis” as the levels of PFOS (perfluorooctanesulfonic acid) doubled. Since use of these compounds is worldwide and rapidly increasing, the risk of exposure is global. As a result, the authors call for large-scale prospective studies to better understand the health consequences of forever chemicals.

PFAS Concerns in China:

A study from China underscores the complexity of this question (Chemosphere, Oct. 2023). This research, like the study you just read about, is a case-control study in which investigators compare people with thyroid cancer to those without. The Chinese scientists analyzed blood samples for 12 different PFAS chemicals, and the findings were not straightforward. Higher levels of PFOS were, in fact, associated with thyroid malignancy. However, PFDA and a few other compounds were actually associated with lower risk. These scientists too call for large-scale prospective studies to clarify the relationship between PFAS and health.

Learn More:

Some of our podcasts have more information on this topic. Regarding PFAS, you may wish to listen to Show 1212: Should You Worry About Forever Chemicals? Show 1301: What Are Forever Chemicals Doing in Food Packaging? offers an update. In addition, Show 1404: How You Can Avoid the Harms from Forever Chemicals provides some practical advice.

Dr. Antonio Bianco and patient advocate Mary Shomon discuss a range of thyroid problems including cancer in Show 1096: What You Need to Know About Treating Thyroid Disease. You might also want to listen to our more recent interview with Dr. Bianco. It is Show 1330: Rethinking Hypothyroidism. We also offer a bonus interview: Dr. Antonio Bianco Describes His Remarkable Thyroid Research. People with a particular interest in this important gland may want to read our eGuide to Thyroid Hormones.