TLDR
Rice samples contained very different amounts of a harmful substance. Where the rice was grown, especially the quality of irrigation water, mattered more than the rice’s commercial label.
Summary
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1 Study Aim
The authors aimed to estimate typical levels of arsenic (As), a harmful element, in rice grain worldwide. They also examined whether rice-growing region, commercial type, soil, or irrigation water best explained differences in rice arsenic. The study tested whether contaminated irrigation water increased arsenic in rice more strongly than contaminated soil. Rice can contain different amounts of a harmful substance, and the study sought to identify the main reasons.
2 Study Design
The researchers measured total arsenic (all measured arsenic forms combined) in 204 commercial rice samples. Most samples came from retail stores in upstate New York, with additional samples from Canada, France, Venezuela, and other countries. They combined these results with published measurements to estimate a global typical range. Two large Bangladesh datasets helped compare the effects of irrigation-water and soil contamination. U.S. samples were also compared by growing region and commercial type. The researchers tested rice from many places and compared how growing conditions affected its contents.
3 Findings
The study reports arsenic concentrations from 0.005 to 0.710 milligrams per kilogram (mg kg−1). Combining the data produced a global typical range of 0.08–0.20 mg kg−1. Average concentrations in U.S. and European rice were both 0.198 mg kg−1, compared with 0.07 mg kg−1 in Asian rice. Bangladesh data linked higher grain arsenic to contaminated irrigation water, not soil. U.S. rice varied mainly by growing region, with averages of 0.258 mg kg−1 in Texas, 0.190 in Arkansas, and 0.133 in California. One Texas distributor had 75% of samples above the typical range, suggesting production in a contaminated environment. The findings support checking irrigation water and regional sources. Rice from some growing areas contained much more of the harmful substance, especially where irrigation water was polluted.