Abstract
Arsenic is a ubiquitous environmental toxicant with antimicrobial properties that can be found in food and drinking water. The influence of arsenic exposure on the composition of the human microbiome in US populations remains unknown, particularly during the vulnerable infant period. We investigated the relationship between arsenic exposure and gut microbiome composition in 204 infants prospectively followed as part of the New Hampshire Birth Cohort Study. Infant urine was analyzed for total arsenic concentration using inductively coupled plasma mass spectrometry. Stool microbiome composition was determined using sequencing of the bacterial 16S rRNA gene. Infant urinary arsenic related to gut microbiome composition at 6 weeks of life (p = 0.05, adjusted for infant feeding type and urine specific gravity). Eight genera, six within the phylum Firmicutes, were enriched with higher arsenic exposure. Fifteen genera were negatively associated with urinary arsenic concentration, including Bacteroides and Bifidobacterium. Upon stratification by both sex and feeding method, we found detectable associations among formula-fed males (p = 0.008), but not other groups (p > 0.05 for formula-fed females and for breastfed males and females). Our findings from a US population indicate that even moderate arsenic exposure may have meaningful, sex-specific effects on the gut microbiome during a critical window of infant development.
Highlights
Arsenic is a ubiquitous environmental toxicant found in food and water worldwide[1,2,3], and is present almost exclusively as inorganic arsenic in water supplies[4], and as inorganic or organic species including metabolites of inorganic arsenic in dietary staples such as rice[5]
Among the subjects included in the current study, infants who were exclusively breast fed had a mean urinary arsenic level of 0.5 μg/L compared with a mean of 0.9 μg/L for those fed both breast milk and formula and 1.2 μg/L for those who were fed only formula
We identified 14 operational taxonomic units (OTUs) that were negatively associated with natural log-transformed infant urinary arsenic concentration, among them, OTUs assigned to the family Clostridiaceae and to the genera Bacteroides and Bifidobacterium
Summary
Arsenic is a ubiquitous environmental toxicant found in food and water worldwide[1,2,3], and is present almost exclusively as inorganic arsenic in water supplies[4], and as inorganic or organic species including metabolites of inorganic arsenic in dietary staples such as rice[5]. Investigations by our group of levels of arsenic exposure common in the US, beginning in fetal life through well water and maternal diet, identified potential health impacts that included dose-related trends in risk of infection and wheezing, as well as fetal growth restriction[12,13,42,46] Immune profiling from this cohort has identified T cell decreases in cord blood[18], increased placental gene expression of proinflammatory marker IL1B and developmental gene Gli[348], and DNA methylation changes in cord blood and placenta[20,48]
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