Univariate predictors of maternal concentrations of environmental chemicals: The MIREC study (Lay summary)

Lewin A, Arbuckle TE, Fisher M, Liang CL, Marro L, Davis K, Abdelouahab N, Fraser WD. International Journal of Hygiene and Environmental Health.  2017 2017 Mar;220(2 Pt A):77-85. DOI: 10.1016/j.ijheh.2017.01.001.

Technological advances have made it possible to measure extremely low levels of chemicals in body fluids (e.g., 1 microgram per liter or 1 part per billion of blood).  For reference, one part per billion can be roughly interpreted as a drop of the chemical in a medium sized swimming pool.  Therefore, it is not unusual to measure very low levels of a number of chemicals in the blood or urine of pregnant women.

This study was designed to identify various characteristics of MIREC participants that are associated with higher or lower levels of various chemicals in their blood or urine. Women completed questionnaires that collected information on maternal characteristics such as age, parity, household income, country of birth, height and weight.  A wide range of chemicals were measured in first trimester maternal blood and urine.

The results revealed that various social factors are significantly associated with the levels of environmental chemicals measured. Levels of some chemicals were higher in women born outside Canada, possibly due to previous exposure outside of Canada, cultural habits or food preferences related to the country of origin. Some chemicals were lower in women who had more than one child. Levels of some metals and persistent organic pollutants were higher in older women, possibly related to having lived during times when there was more pollution. Women who were current smokers had higher blood cadmium levels, a chemical found in tobacco smoke, as well as higher levels of bisphenol A (BPA) in their urine.

These results show that maternal factors can be associated with the levels of chemicals measured in their blood or urine and produce an unequal distribution of chemical exposures among populations within a country.   These factors need to be considered in risk assessments, as they can affect the degree of exposure and may modify the individual’s susceptibility to potential health effects due to differences in lifestyle, diet, and age.