Carignan et al. 2015 — Arsenic Sources in Infancy: Well Water vs Breast Milk
This 2015 New Hampshire Birth Cohort study quantified the relative contributions of private well water and breast milk to infant arsenic exposure at 6 weeks of age, establishing that formula-fed infants in well-water homes have substantially higher arsenic exposure than breastfed infants.
Key numbers
Breast milk tAs (n=9 breastfeeding mothers, µg/L): Median 0.31, range <0.22–0.62. LOD 0.22 µg/L.
Infant urinary arsenic (minus arsenobetaine) by feeding mode (n=72 infants, µg/L): Formula-fed: median 0.17, range <LOD–2.9. LOD 0.05 µg/L. Breastfed infants had 7.5× lower urinary arsenic than formula-fed.
Home tap water from private wells (n=874 households, µg/L): Median 0.44; range <0.01–189; some wells far above EPA MCL of 10 µg/L.
Estimated daily intake (µg/kg bw/day): Formula-fed (median): 0.22. Breastfed (median): 0.04. 5.5× difference.
Methods
HPLC-ICP-MS speciation. 72 infants; 9 breastfeeding mothers; well water from 874 households. NHBCS northeastern US private well water area. LOD breast milk 0.22 µg/L; urinary 0.05 µg/L.
Key finding: In well-water households, formula preparation with arsenic-contaminated well water is the dominant route of infant As exposure in early infancy, not the formula powder itself. Breast milk median As (0.31 µg/L) from non-contaminated-water mothers is extremely low.
Implications
App: Formula preparation water quality is a critical determinant; municipal water vs well water vs bottled water creates large differences in infant formula As exposure.