Arsenic levels among pregnant women and newborns in Canada: results from the Maternal-Infant Research on Environmental Chemicals (MIREC) Cohort (Lay summary)

Ettinger AS, Arbuckle TE, Fisher M, Liang CL, Davis K, Mihai Cirtiu C, Bélanger P, LeBlanc A, Fraser WD, the MIREC Study Group. Environmental Research. 2016 Nov 20;153:8-16. doi: 10.1016/j.envres.2016.11.008.

Arsenic in the environment occurs due to natural causes (e.g., stored in the earth’s crust and groundwater) as well as human activities (e.g., gold mining, fossil fuel combustion, pesticide application and waste incineration). Possible sources of exposure to arsenic include some foods (e.g., seafood and rice) and drinking water. Certain types of arsenic are toxic at elevated levels. Arsenic can be passed from a pregnant woman to her developing baby. Some studies (but not all) have reported that maternal exposure to elevated levels of arsenic has been associated with adverse birth outcomes and may affect child IQ and memory.

The Maternal-Infant Research on Environmental Chemicals (MIREC) Study recruited 2,000 women between 2008 and 2011 from 10 urban sites across Canada. Arsenic was measured in maternal blood and urine collected during pregnancy, umbilical cord blood at delivery and infant meconium. Meconium is the first stool that the infant passes within the first two days of birth and, because it is formed during the 2nd and 3rd trimesters of pregnancy, measuring chemicals in meconium is an indicator of fetal exposure.

Trace levels of arsenic were detected in the 1st and 3rd trimester blood samples of most of the women in the study. However, only about 50% of the umbilical cord blood samples had detectable levels of arsenic and no arsenic was detected in more than 90% of the meconium samples.

Arsenic levels in maternal blood were higher in Asian (Chinese, South and Southeast Asian, Filipino, Japanese, and Korean) women than in non-Asian women, possibly due to differences in preference for foods known to contain more arsenic than most (e.g., seafood and rice). Higher blood arsenic levels were detected in women who were 30 years old or more, had more than one child, or had more education. Arsenic levels in maternal blood from MIREC participants were lower than typical levels found in Canadian women of reproductive age (20-39 years of age).

Further research is needed to identify major sources of arsenic in pregnant women and factors which may influence their exposure.