Endocrine Disrupting Chemicals and Sensitive Reproductive Endpoint Measures: Evidence from the MIREC and MIREC-ID Cohort Study in Canada

Abstract

Objective: Prenatal exposure to potential endocrine disrupting chemicals may be linked to adverse reproductive health outcomes; however the evidence available in human populations is scarce and inconsistent. The aim of this study was to examine any potential associations between prenatal exposure to select phthalate metabolites, bisphenol A and triclosan and the anogenital distance at birth and the 2D:4D digit ratio at 6-months of age, in male and female infants. Methods: Approximately 2000 women in their 1st trimester of pregnancy were recruited from across Canada as part of the MIREC Research Platform. Single spot urine samples were collected and analyzed for various environmental chemicals. Of this sample, 525 women were recruited into the follow-up study, MIREC-ID, which measured the anogenital distance and 2D:4D digit ratio in infants. Analyses included descriptive statistics of the chemicals and the sample population, and the fitting of multiple linear regression models. Results: In female infants, the phthalate metabolite MBzP was negatively associated with the anus-clitoris distance (p=0.002) and positively associated with the 2D:4D digit ratio (p=0.024). The metabolite MEP was positively associated with the anus-clitoris distance (p=0.008). In male infants, the metabolite MEHHP and total BPA were negatively associated with the 2D:4D digit ratio (p=0.021 and p=0.002, respectively). There we no other significant associations observed among the 96 comparisons tested. Conclusion: In contrast to some other studies, although a few significant associations were observed, in this study, type 1 error cannot be ruled out due to the many comparisons made.