Predicting the Permissible Limit of Arsenic in Irrigation Water for Rice Cultivation

This study establishes, for the first
time, a permissible
arsenic
limit for irrigation water to ensure the safe cultivation of rice,
a dietary staple in South Asia. Arsenic contamination of irrigation
water is a major health risk for approximately 110 million people
in this region. An incubation study was conducted using 420 monolithic
soil columns from 10 arsenic-contaminated sites under two irrigation
regimes (rainfed and irrigated). Using a logistic regression model,
a threshold concentration for arsenic in irrigation water was identified
as 190 μg L–1. A nonparametric bootstrap simulation
(n = 100,000) was performed, yielding a 95% confidence
interval of 163.78–190.20 μg L–1, which
confirmed the model’s stability. The threshold was validated
with field samples and effectively classified rice grain arsenic concentrations.
These findings provide a reference for managing irrigation practices
to safeguard food safety in arsenic-endemic rice-growing regions of
South Asia.