Flame Retardants Tied to Thyroid Cancer Risk

One chemical in particular was linked in study to larger, more aggressive tumors

By Alan Mozes

HealthDay Reporter

TUESDAY, April 11, 2017 (HealthDay News) -- Flame retardants used in many home furnishings may boost the risk for thyroid cancer, researchers report.

"Thyroid cancer is the fastest increasing cancer in the U.S., with most of the increase in new cases being papillary thyroid cancer," said study lead investigator Dr. Julie Ann Sosa. This is the most common type of thyroid cancer.

"Recent studies suggest that environmental factors may, in part, be responsible for this increase," added Sosa, a professor of surgery and medicine at Duke University School of Medicine in Durham, N.C.

The study researchers focused on a class of flame retardants known as PBDEs (polybrominated diphenyl ethers). They've been used to prevent or delay fires in building materials, electronics, furnishings, cars and airplanes, plastics, foams and textiles.

Animal studies have shown that several classes of flame retardants interfere with thyroid function, Sosa said. So she and her colleagues wanted to explore a possible relationship with thyroid cancer.

To assess the potential risk, the study team collected dust samples from the homes of 140 participants, half of whom had papillary thyroid cancer. About 80 percent of the participants were women, as they're more likely to develop thyroid cancer than men. On average, the participants had lived in their homes for more than a decade.

The researchers also took blood samples to evaluate exposure to certain flame retardants.

The team found that those living in homes exposed to higher levels of two types of PBDE flame retardants were at an increased risk for having papillary thyroid cancer. Those two types are known as BDE-209 and TCEP.

People living in homes with high levels of BDE-209 were more than twice as likely to have thyroid cancer as those living in homes with low exposure levels, the study found.

And participants with high levels of TCEP in their house dust were more than four times as likely to have larger, more aggressive tumors, the researchers said.

Sosa presented the findings at a recent meeting of the Endocrine Society in Orlando, Fla.

The research doesn't establish a direct cause-and-effect relationship between the cancer and the flame-retarding chemicals.

Still, "our study results suggest that higher exposure to several flame retardants in the home environment may be associated with the diagnosis and severity of papillary thyroid cancer, potentially explaining some of the observed increase in the incidence of thyroid cancer," Sosa said in a society news release.

Until published in a peer-reviewed medical journal, research presented at meetings is usually considered preliminary.