Contribution of breast milk and formula to arsenic exposure during the first year of life in a US prospective cohort

Abstract

Arsenic is a carcinogen that can also affect the cardiac, respiratory, neurological and immune systems. Children have higher dietary arsenic exposure than adults due to their more restricted diets and greater intake per unit body mass. We evaluated the potential contributions of breast milk and formula to arsenic exposure throughout the first year of life for 356 infants in the prospective New Hampshire Birth Cohort Study (NHBCS) using infant diets reported by telephone at 4, 8 and 12 months of age; measured household water arsenic concentrations; and literature data. Based on our central-tendency models, population-wide geometric mean (GM) estimated arsenic exposures in the NHBCS were relatively low, decreasing from 0.1 μg kg−1 d−1 at 4 months of age to 0.07 μg kg−1 d−1 at 12 months of age. At all three time points, exclusively formula-fed infants had GM arsenic exposures ~8 times higher than exclusively breastfed infants due to arsenic in both tap water and formula powder. Estimated maximum exposures reached 9 μg kg−1 d−1 among exclusively formula-fed infants in households with high tap water arsenic (80 μg/L). Overall, modeled arsenic exposures via breast milk and formula were low throughout the first year of life, unless formula was prepared with arsenic-contaminated tap water.

Sex-specific associations of infants’ gut microbiome with arsenic exposure in a US population

“…We stratified study subjects by sex to identify sex-specific effects given that sex-specific perturbations to gut microbiome community structure by arsenic exposure through drinking water have been observed in mice 50 . In addition, our previous research in the NHBCS indicated clear associations between the infant gut microbiome at 6 weeks of age and infant feeding and we also previously reported in this cohort that breast milk fed infants have lower urinary arsenic than formula-fed infants and is not a likely source of dietary arsenic 15 , 34 . Therefore, to address the potential for confounding or modification of the relationship between arsenic exposure and the infant microbiome by feeding method, we also stratified based on infant feeding, analyzing infants who did and did not receive formula separately.…”

“…We found an overall marginal association between infant urinary arsenic and microbiome composition among all infants in the study after adjustment for feeding method and urine specific gravity. Breast milk is known to be low in arsenic in our population and others 15 , 34 , 35 , 51 – 55 and exclusively breastfed babies had lower urinary arsenic concentrations than formula or mixed fed infants in our cohort 34 . Previous research by our group showed that this is to the contamination of both formula powder and drinking water used to mix formula 34 , with popular brands of formula containing from 2.2–12.6 ng/g of arsenic, most of it inorganic 56 .…”

Infants’ dietary arsenic exposure during transition to solid food

“…The number of reported breast milk feedings was used as an indirect measure of amount of breast milk consumed 26 . The exposure to arsenic during infants’ transition to solid food was evaluated with paired Wilcoxon signed-rank test statistical analyses to accommodate our relatively low sample size; statistical conclusions are robust to the use of parametric vs. non-parametric tests (data not shown).…”

“…Thus, formula fed-infants tend to have a higher level of urinary arsenic species associated with i-As exposure than exclusively breastfed infants. Still, the overall urinary arsenic concentrations and estimated i-As exposure have been reported to be relatively low compared to the general population 15 , 20 , 22 , 26 .…”

Relation between in utero arsenic exposure and growth during the first year of life in a New Hampshire pregnancy cohort

“…Our study was limited by arsenic exposure only being measured at one time during pregnancy; however one study conducted in Native American populations with relatively low levels of arsenic exposure suggests that measures of urinary arsenic are relatively stable over time (Navas-Acien et al, 2009). Our study was also limited by not assessing biomarkers of postnatal arsenic exposure in infants, however our findings were robust in sensitivity analyses restricted to infants who were exclusively breast fed, a subgroup without demonstrable postnatal arsenic exposure (Carignan et al, 2015(Carignan et al, , 2016Fängström et al, 2008). As women have been shown to underestimate their pre-pregnancy weight via selfreport, causing some overweight mothers to be misclassified as normal weight prior to pregnancy (Han et al, 2016), our reliance on self-reported maternal pre-pregnancy weight may have led to some subjects being misclassified with regards to pre-pregnancy weight status.…”