Beene et al. 2022 — Mass-balance approach to arsenic intake and excretion (Bangladesh, Navajo, Chile)
This study applies a geoscience-derived mass-balance framework to reconcile arsenic intake from multiple environmental sources with urinary arsenic excretion in three well-characterized populations: rural Bangladesh (HEALS cohort, n=11,224), Navajo Nation birth cohort (NBCS, n=619), and northern Chile case-control studies (n=630). The approach treats biomarker arsenic as a dependent variable reflecting total intake from multiple pathways, rather than as an independent exposure marker. In Bangladesh, accounting for arsenic from both well water and rice substantially improved the alignment between predicted intake and measured urinary excretion; rice contributed an average of approximately 96 µg/day of arsenic, about one-third of the 300 µg/day average from drinking water. Rice As concentrations ranged 50–1,200 µg/kg (average 244 ± 150 µg/kg uncooked; 235 ± 180 µg/kg cooked). In Navajo Nation, home dust emerged as an important additional arsenic source beyond drinking water. In northern Chile, persistent imbalance between intake estimates and excretion suggested imprecise measurement of drinking water arsenic as the main source of misclassification.
Key numbers
Bangladesh HEALS: rice As concentration 50–1,200 µg/kg (average 244 ± 150 µg/kg uncooked; 235 ± 180 µg/kg cooked); average rice consumption 300 g/day (women), 520 g/day (men); rice-derived As intake approximately 96 µg/day on average; well-water As geometric mean 45 µg/L (overall), range to 860 µg/L; average drinking-water As intake approximately 300 µg/day. Urinary total As: 1–2,300 µg/L, mean 140 µg/L; MMA + DMA account for >80% of urine As. Navajo NBCS: 13% used water with As >10 µg/L; home dust identified as important source. Chile: fish/shellfish identified as supplementary source via FFQ and urine speciation.
Methods (brief)
Mass-balance analysis combining multiple environmental source measurements with urinary total arsenic and speciation data. Bangladesh: HEALS cohort data from 2000–02 recruitment, with rice As data from household samples collected 2016 (n=410 participants). Navajo: NBCS recruitment 2013+. Chile: case-control 2007–2010. Urine As speciation (DMA, MMA, arsenobetaine, inorganic) measured in subsets. Simulations performed integrating source contributions with creatinine-adjusted urine dilution correction.
Implications
Certification: Rice contributes one-third of total arsenic intake in a population with both high rice consumption and moderately elevated groundwater As. The rice As concentration range (50–1,200 µg/kg) from Bangladeshi household samples represents a realistic distribution for As-contaminated regions. Courses: Demonstrates the mass-balance method for exposure assessment and illustrates how single-source monitoring (water only) systematically underestimates total As intake where rice is a staple. App: The multi-source approach is the correct conceptual frame for the app’s cumulative exposure model; rice and drinking water must both be incorporated for populations with high rice consumption.