Exposure to Flame Retardants in the Home and Risk and Severity of Papillary Thyroid Cancer: Are They Associated?

Presentation Number: FRI 113
Date of Presentation: April 1st, 2016

Kate Hoffman*1, Amelia Lorenzo Lorenzo1, Craig M Butt1, Brittany Bohinc-Henderson2, Heather Stapleton1 and Julie Ann Sosa1
1Duke University, Durham, NC, 2Wake Forest Baptist Medical Center, Winston-Salem, NC

Abstract

Background: Thyroid cancer is the fastest increasing cancer in the US; over the last decade, incidence has increased by 7-8% per year. While increased exposure to radiation has been hypothesized to play a role, recent studies suggest that other environmental factors are likely responsible. Use of flame retardant chemicals (FRs) has increased dramatically over the last few decades, particularly as flammability standards have become more stringent. Human exposure to FRs also is increasing, raising concerns about potential health impacts. Indeed, animal studies indicate that some FRs disrupt endocrine function and are carcinogenic.

Methods: We are conducting a case controlled study investigating the impact of FR exposure on papillary thyroid cancer (PTC) occurrence and severity. We have recruited 50 participants with PTC and 50 controls.  Participants provided blood and urine samples, from which we measured exposure biomarkers. Because levels of FRs in household dust are strongly correlated with personal exposure, we also visited participants’ homes and collected dust samples. Several classes of FRs have been measured in dust. Demographic, lifestyle, and environment information were collected via questionnaire, and tumor histology data were abstracted from medical records. 

Results: Our data to date (n=50) indicate that study participants ranged from 21 to 67 years of age, and the majority were female (66%), reflecting a known gender difference in PTC risk. Approximately half of cases had nodal metastases (52%), and 70% were positive for the BRAFV600E mutation. FRs were detected in 100% of dust samples. Organophosphate flame retardant levels in dust collected in cases’ homes were 1.1-1.6 times those of controls, although differences were not statistically significant (p>0.05). Our data suggest that higher levels of some brominated FRs [e.g. bis(2-ethylhexyl)-2,3,4,5-tetrabromophthalate (TBPH), and 2-ethylhexl-2,3,4,5-tetrabromobenzoate] in dust are associated with increased PTC odds. Associations were strongest in participants that reported spending the most time at home. For example, when we restricted analysis to participants spending ≥12 hours per day in their home, those with dust concentrations of TBPH above the median were 5.5 times as likely to have PTC compared to those with levels below the median (p=0.06). Two polybrominated diphenyl ethers, BDE-47 and BDE-153, were commonly detected in serum samples (>60% of participants). Although not related to case status, data suggest that higher BDE-47 levels may be associated with more aggressive tumors (i.e. nodal metastases), while higher BDE-153 levels may be associated with increased odds of BRAFV600E mutation.

Conclusions: Taken together, our results suggest that exposure to FRs may be associated with the occurrence and severity of PTC; however, more data are required. We are currently recruiting additional participants.

 

Nothing to Disclose: KH, ALL, CMB, BB, HS, JAS