86. Prenatal exposure to endocrine disrupting chemical mixtures and infant birth weight: A Bayesian analysis using kernel machine regression (lay summary)

Hu J, Arbuckle TE, Janssen P, Lanphear BP, Zhuang LH, Braun JM, Chen A, McCandless LC. Environmental Research 2021 Apr;195:110749. doi: 10.1016/j.envres.2021.110749

Analyses of urine and blood samples from Canadians have shown that we are exposed to numerous chemicals in our lives.  Some of these chemicals are endocrine disruptors – chemicals that interfere with our hormone systems.  Pregnant women are often exposed to a mixture of potential endocrine disrupting chemicals that may affect infant birth weight.  Many studies have been done on individual chemicals and their association with birth weight.  However, research on how exposure to multiple chemicals at the same time is limited.  The objective of this study, therefore, was to examine the association between prenatal exposure to a mixture of endocrine disrupting chemicals and infant birth weight.

Data from 1857 pregnant women and their newborns from the Maternal-Infant Research on Environmental Chemicals (MIREC) Study were analysed.  Concentrations of twenty-one different chemicals from five unique groups were measured in the women’s 1st trimester blood and urine.  These groups were organochlorine compounds (OCs), metals, perfluoroalkyl substances (PFAS), phenols (BPA or bisphenol A, and triclosan) and phthalates.  Statistical techniques were used to measure the changes in birth weight in relation to increasing levels of chemicals.

The researchers found that mixtures of OCs and metals were associated with reduced birth weight, with trans-nonachlor from the OC group and lead from the metal group having the greatest impact.  Every 2-fold increase in each of maternal trans-nonachlor and blood lead concentrations was associated with an approximately 40 grams (1.4 oz) reduction in birth weight.  PFAS, phenols and phthalates were not associated with birth weight.

In conclusion, this study led by a graduate student at Simon Fraser University, found that higher levels of OC and metal mixtures in maternal blood during the 1st trimester were associated with lower birth weight among MIREC infants.