ASPO Abstracts
Exposure to Organophosphate Flame Retardants and Thyroid Cancer Risk in Women
Category: Molecular Epidemiology & Environment, Molecular Epidemiology & Environment
Conference Year: 2018
Abstract Body:
Purpose: Exposure to organophosphate flame retardants (PFRs) occurs worldwide, and growing evidence demonstrates that these chemicals can alter thyroid hormone regulation and function. We investigated the relationship between PFR exposure and thyroid cancer and examined whether individual characteristics or temporal factors predicted PFR exposures. Methods: Our analysis included 100 incident female, papillary thyroid cancer cases and 100 female controls of a Connecticut-based thyroid cancer case-control study. Interviewer-administered questionnaires and spot urine samples were collected at home visits from 2010-2013. We used mass spectrometry to measure concentrations of six PFR metabolites: 1-hydroxy-2-propyl bis(1-chloro-2-propyl) phosphate (BCIPHIPPP), bis(1-chloro-2-propyl) phosphate (BCIPP), diphenyl phosphate (DPHP), bis(1,3-dichloro-2-propyl) phosphate (BDCIPP), isopropyl-phenyl phenyl phosphate (ip-PPP), and tert-butyl phenyl phenyl phosphate (tb-PPP). We used unconditional logistic regression to estimate odds ratios (OR) and 95% confidence intervals (95% CI) for thyroid cancer risk for continuous and categories (low, medium, high) of concentrations of individual and summed metabolites, adjusting for potential confounders. We used multiple linear regression models to examine the relationship between concentrations of PFR metabolites and individual characteristics (age, smoking status, alcohol consumption, body mass index, income, education) and temporal factors (season, year). Results: None of the individual or summed PFRs were significantly positively associated with risk of papillary thyroid cancer. However, the odds ratios of BDCIPP was elevated; the OR (95%CI) for the high versus low category was 1.78 (95%CI: 0.83-3.8). BCIPP was inversely related to thyroid cancer risk; the OR (95%CI) for the high versus low category was 0.32 (0.20-1.00). Our exposure determinants analysis observed higher urinary PFR concentrations with increasing BMI and in the summer season. Conclusions: Our results do not support an increased risk of thyroid cancer with exposure to PFRs. However, given the modest sample size and use of spot urine samples to represent long-term exposure, the research question warrants additional study.
Keywords: thyroid cancer, endocrine disruptor, women’s health, environmental exposures, biomarkers