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In the United States (US), residing in a lower socio-economic environment neighborhood is associated with greater exposure to heavy metals due to closer proximity to major roads and industrial sites, increased exposure to particulate matter air pollution, residence in neighborhoods containing poorly maintained older homes with unmitigated lead (Pb) paint and higher rates of tobacco use. While some heavy metals are required for human health, Pb has no known biological function and is considered a systemic toxicant at deficient levels of exposure. Exposure causes deleterious effects, including upregulation of inflammatory cytokines and markers, developmental delays, neurological effects, microbial dysbiosis, and increased incidence of chronic and infectious illnesses. Exposure to Pb is cumulative in the body, and increased maternal body burden has been associated with increased exposure in infants via trans-placental transfer and human milk feeding. The dose of Pb in human milk may be significant, as the intestinal absorption rate for ingested toxins is significantly higher for infants than adults.

 

Using samples collected from breastfeeding dyads participating in two well-characterized urban birth cohorts in Cincinnati, OH, the proposed study will address these knowledge gaps by quantifying Pb burden in cord serum and human milk samples at two and six weeks of age, estimating exposure in an urban, US population, and correlating exposure levels to changes in the microbiome. The planned analysis includes:

• Calculating dose by human milk.
• Estimating total exposure in Cincinnati children.
• Family-level, ecological, and geospatial risk factors for increased Pb exposure.
• The relationship between these early exposures and Pb level at age two.

Further analysis will examine a subset of children to identify the relationship between the level of exposure and diversity and phylogenic changes in the gut microbiome at age two months.