Forever chemicals identified as thyroid cancer risk

Researchers have discovered a link between certain per- and polyfluoroalkyl substances (PFAS) and an increased risk for thyroid cancer, according to a new study.

PFAS, also known as ‘forever chemicals’, are a large, complex group of synthetic chemicals that can migrate into the soil, water and air.

Due to their strong carbon-fluorine bond, they do not degrade easily in the environment.

They have been used in consumer products globally since the 1940s, including nonstick cookware, water-repellent clothing, stain-resistant fabrics, and other products that resist grease, water, and oil.

Multiple national and international institutions, including the European Parliament and the US Environmental Protection Agency, have declared PFAS exposure a health crisis.

The Mount Sinai Health System study published in eBioMedicine supports the actions needed to regulate and remove these chemicals from potential exposure routes.

A global concern

Although PFAS exposure has been identified as a potential contributor to recent increases in thyroid cancer, limited studies have investigated the association between PFAS exposure and thyroid cancer.

“With the substantial increase of thyroid cancer worldwide over recent decades, we wanted to dive into the potential environmental factors that could be the cause for this rise.” said co-corresponding author Dr Maaike van Gerwen.

Gerwen is assistant professor and director of research for the Department of Otolaryngology – Head and Neck Surgery, Icahn School of Medicine at Mount Sinai.

“This led us to the finding that PFAS, ‘forever chemicals’, may at least partially explain the rise of thyroid cancer and are an area we should continue to study further,” he added.

“Thyroid cancer risk from PFAS exposure is a global concern given the prevalence of PFAS exposure in our world.

“This study provides critical evidence to support large-scale studies further exploring the effect of PFAS exposure on the thyroid gland.”

Increased risk

The researchers investigated associations between plasma PFAS levels and thyroid cancer diagnosis using BioMe, a medical record-linked biobank at Icahn Mount Sinai.

They studied 88 thyroid cancer patients with plasma samples collected either at or before cancer diagnosis and 88 non-cancer controls.

They were people who did not develop any form of cancer – who matched on sex, race or ethnicity, age (within five years), body mass index, smoking status and the year of sample collection.

The researchers measured levels of eight PFAS in blood samples from the BioMe participants using untargeted metabolomics.

The levels of individual PFAS were compared between the group of participants who developed thyroid cancer and the group of healthy participants, using different statistical models to estimate accuracy.

The results showed that exposure to perfluorooctanesulfonic acid (n-PFOS, a group of chemicals under the PFAS umbrella) led to a 56 percent increased risk of thyroid cancer diagnosis.

Additionally, the researchers conducted the analysis again in a subgroup of 31 patients who had at least a year between their enrolment in BioMe and their diagnosis of thyroid cancer.

This was to take into consideration the time lag between exposure to PFAS chemicals and developing a disease.

From this second analysis, there was also a positive association between the exposure of n-PFOS and the risk of thyroid cancer.

There was also a positive association with a few additional PFAS chemicals, including branched perfluorooctanesulfonic acid, perfluorononanoic acid, perfluorooctylphosphonic acid, and linear perfluorohexanesulfonic acid.

“The results of this study provide further confirmation for the PFAS health crisis and underline the need to reduce, and hopefully one day eliminate, PFAS exposure,” said co-corresponding author Dr Lauren Petrick.

Petrick is associate professor of Environmental Medicine and Public Health at Icahn Mount Sinai.

“Today, it’s nearly impossible to avoid PFAS in our daily activities. We hope these findings bring awareness of the severity of these forever chemicals,” she added.

“Everyone should discuss their PFAS exposure with their treating physician to determine their risk and get screened if appropriate. In addition, we need continued industry changes to eliminate PFAS altogether.”