Ashley-Martin J, Dodds L, Arbuckle TE, Lanphear BP, Muckle G, Bouchard MF, Fisher M, Asztalos E, Foster WG, Kuhle S. Environmental Research. 2019 Sep 12;179(Pt A):108736. doi: 10.1016/j.envres.2019.108736
Lead, cadmium, mercury and arsenic are toxic metals in our environment. Limited information is available on potential associations between exposure to environmental metals at current low levels and body mass index (BMI) of children. Body mass index is a measure of body fat based on the individual’s height and weight. BMI is calculated by dividing a person’s weight in kilograms by their height in metres squared (kg/m2).
In the MIREC-CD Plus study, blood was collected from 449 children ages 2 to 5 years and analyzed for both toxic metals and essential elements (nutrients). At the same time, the child’s height and weight were measured and their BMI was calculated. The associations between levels of each toxic metal and BMI were studied, controlling for other maternal and child factors that might affect child BMI.
Most of the children had very low but detectable concentrations of metals in their blood. The average blood lead level in MIREC children was 0.66 µg/dL, which was a bit lower than the average measured in a national sample of 3-5 year old Canadian children (0.93 µg/dL). In the MIREC-CD Plus study, girls with higher blood lead levels (>0.82 µg/dL) tended to have lower BMI scores than girls with the lowest lead levels (<0.54 µg/dL). In contrast, higher blood lead levels in boys were associated with slight increases in BMI scores. Child blood levels of arsenic, cadmium and mercury were not associated with their BMI, height or weight.
In this population of Canadian preschool aged children with very low blood lead levels, the researchers observed that the association between lead and BMI was different for boys versus girls. While girls with slightly higher blood lead levels had lower BMIs, boys with similar blood lead levels to the girls had modestly higher BMIs. Future follow-up of the MIREC children as they get older will help researchers study whether early life exposure to lead may have any long-term effects on their growth and development.
This work was led by a researcher at Dalhousie University.