- Higher exposure to several flame retardants in the home environment may be associated with the diagnosis and severity of papillary thyroid cancer.
- Several classes of flame retardants act as endocrine-disrupting chemicals and interfere with thyroid homeostasis.
- Decabromodiphenyl ether (BDE-209) and tris(2-chloroethyl) phosphate (TCEP) were the flame retardants causing papillary thyroid cancer.
Papillary thyroid cancer (PTC), a common type of thyroid cancer is associated with flame retardants used in many home products.
The term Flame retardants subsumes a diverse group of chemicals which are added to manufactured materials, such as plastics and textiles, and surface finishes and coatings.
‘Environmental chemicals in the form of dust exposed to flame retardants commonly used in home products increased the chances of thyroid cancer by nearly 14 times.’
Many animal studies have demonstrated that several classes of flame retardants act as endocrine-disrupting chemicals and interfere with thyroid homeostasis (function), partly because they share a similar chemical structure with thyroid hormones.
"Thyroid cancer is the fastest increasing cancer in the U.S., with most of the increase in new cases being papillary thyroid cancer," said the study's lead investigator, Julie Ann Sosa. "Recent studies suggest that environmental factors may, in part, be responsible for this increase."
"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. "This study is novel in that we collected and analyzed individuals' house dust as a measure of exposure to flame retardants."
Personal Exposure to House Dust
Levels of flame retardants in house dust significantly correlate with personal exposures, she explained. The researchers collected dust samples from the homes of 140 study subjects: 70 with PTC and 70 individuals without evidence of thyroid disease or cancer as control subjects.
Controls were matched on important characteristics, including age, sex, race/ethnicity, body mass index, household income and education level. Because all participants had lived in their homes for an average of approximately 11 years, Sosa said the researchers could assess long-term average exposure to these environmental chemicals. They also collected participants' blood samples to analyze biomarkers of exposure to several flame retardants in the class known as polybrominated diphenyl ethers (PBDEs).
Just as PTC affects more women than men, most study participants (79 percent) were women, and their average age was 48 years. The investigators reported that higher levels in house dust of two flame retardants were associated with an increased odds of the home resident having PTC
- Those were decabromodiphenyl ether (BDE-209), the most heavily used PBDE, and to a lesser degree, tris(2-chloroethyl) phosphate (TCEP), an organophosphate flame retardant.
- Participants whose BDE-209 levels in their dust were high were more than two times as likely to have thyroid cancer than those individuals with low BDE-209 concentrations.
- Participants with high levels of TCEP in their house dust were more than four times as likely to have larger, more aggressive tumors that extended beyond the thyroid.
In contrast, participants with the highest dust levels of BDE-209 were 14 times as likely to be a PTC patient that did not have a common gene mutation (BRAF V600E). This mutation has been linked to PTC that tends to behave more aggressively. "This difference," Sosa said, "begs more interrogation."
- Julie Ann Sosa et al., Exposure to common flame retardants may raise the risk of papillary thyroid cancer, ENDO 2017: The Endocrine Society's 99th Annual Meeting & Expo (2017).