Gestational exposure to organochlorine compounds and metals and infant birth weight: effect modification by maternal hardships.

Janice MY Hu, Tye E Arbuckle, Patricia A Janssen, Bruce P Lanphear, Joshua D Alampi, Joseph M Braun, Amanda J MacFarlane, Aimin Chen, Lawrence C McCandless. Environmental Health 2024 Jul 1;23(1):60. doi: 10.1186/s12940-024-01095-x

Question: Do maternal hardships negatively impact associations observed between persistent organochlorine compounds or metals and infant birth weight?

What did the researchers do:
Six organochlorine chemicals (including PCB’s, banned organochlorine pesticides) and 5 metals (including lead and mercury) were measured in 1st trimester blood samples of women participating in MIREC. Based on the responses to questionnaires, the researchers identified 9 potential maternal hardships (i.e., belonging to a racial or ethnic minority, immigrant, financial strain, low intake of folic acid from supplements, low educational status, living status [e.g., separated], single parent, being a student and experiencing chronic diseases). They then examined associations between these hardships and infant birth weight. They also looked to see whether the combinations of specific chemicals and hardships were associated with lower infant birth weights.

What did they find:
The statistical models showed that trans-nonachlor (a banned organochlorine pesticide that persists in the environment), lead, low educational status, racial minority, and low intake of folic acid from supplements were each associated with lower birth weight. Experiencing both a maternal hardship and higher blood concentrations of some chemicals had varying impacts on infant birth weight, depending on the chemical. For example, every two-fold increase in lead concentrations was more strongly associated with lower infant birth weight among participants with lower education than those with higher education. However, every two-fold increase in mercury concentrations was associated with slightly higher birth weight among participants with low education compared to those with higher education.

What does this mean:
The findings from this study suggest that some maternal hardships that co-occur with exposure to various chemicals and metals during pregnancy may interact and produce a greater (or in some cases, lesser) impact on birth weight than either exposure alone. It is widely known that birth weight is determined by multiple factors (genetic, environmental, social and maternal). This study provides some data that may contribute to our understanding of how these factors work together.

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