3. Phthalate and bisphenol A exposure among pregnant women in Canada – Results from the MIREC study (lay summary)

Arbuckle TE, Davis K, Marro L, Fisher M, Legrand M, LeBlanc A, Gaudreau E, Foster WG, Choeurng V, Fraser WD; MIREC Study Group. Environment International. 2014 Jul;68:55-65. doi: 10.1016/j.envint.2014.02.010

Phthalates and Bisphenol A (BPA) are two chemicals that are commonly found in the environment, and have garnered a good deal of media attention which has helped to raise awareness of them among the general public in Canada. BPA is used to make a hard, clear plastic and may also be found in epoxy resin linings on the inside of metal-based food and beverage cans. Thermal papers such as receipts and tickets may also be a source of BPA. Phthalates are a family of chemicals commonly used to make plastics soft and flexible and harder to break. They are often called plasticizers and have a large number of industrial and commercial uses – for example, vinyl flooring, adhesives, detergents, automotive plastics, some children’s toys, and personal-care products (soaps, shampoos, hair spray, nail polishes). Some phthalates are also used as solvents for other materials.

Phthalates and BPA are both hormone (or “endocrine”) disruptors possibly linked to harmful reproductive and neurodevelopmental effects. These chemicals have commonly been measured in urine collected in population surveys, but less is known about their levels in populations of pregnant women, especially for the critical first trimester of pregnancy. For this reason, research was carried out to measure BPA and phthalate metabolites in first trimester urine samples collected from pregnant women participating in the MIREC Study, and to identify factors that predict exposure to these two environmental chemicals. (Metabolites are substances produced during metabolism, or bodily chemical processes, and may also refer to products that remain after a substance is broken down, or metabolized, by the body). A questionnaire was used to gather demographic and socio-economic information on the roughly 2,001 women who were recruited during the first trimester of pregnancy from ten cities across Canada, and a one-time urine sample was collected and analyzed for total BPA and 11 phthalate metabolites.

Almost 88% of the women had detectable levels of BPA in their urine. An analysis of urinary levels of BPA by maternal characteristics showed that average levels decreased with increasing maternal age; were higher in current smokers or women who quit during pregnancy, compared to never smokers; and tended to be higher in women who provided a fasting urine sample and who were born in Canada, and had lower incomes and lower levels of education.

Several of the phthalate metabolites analyzed weren’t all that common in the MIREC cohort, with only 15% of the urine samples having detectable levels. Two phthalate metabolites had the highest measured levels in urine. The levels of a third type of metabolite decreased with maternal age but didn’t differ by time of urine collection; whereas a fourth class of metabolites tended to be higher in older women and when the urine was collected later in the day.

This research provides the first biomonitoring results for the largest population of pregnant women sampled in the first trimester. The results show that exposure to BPA and phthalates among MIREC women is comparable to or even lower than that seen in women of reproductive age who participated in the Canadian Health Measures Survey (CHMS), a national population-based survey.