Measuring Arsenic in Rice Crops

To avoid exposure to arsenic, increase access to detection and remediation of arsenic-contaminated water

Naturally-occurring arsenic in Bangladesh’s groundwater has been identified as one of the world’s great humanitarian disasters, with millions of people at risk of cancers and other diseases from drinking water and eating rice irrigated with contaminated water. Now University of Massachusetts Amherst analytical chemist Julian Tyson and his student Ishtiaq “Rafi” Rafiyu are partnering with Chemists Without Borders (CWB) to develop a low-cost, easy-to-use test kit to measure arsenic in Bangladesh’s rice supply, offering consumers information on exposure.

Tyson says, “One of the first steps in trying to make a difference and help people avoid this exposure has been to increase access to detection and remediation of arsenic-contaminated water, and many non-governmental organizations have been active for years in this area. 

Last year, CWB approached the UMass Amherst lab to develop a simple, low-cost test for arsenic in rice, based on the groundwater test. 

One of the key challenges in testing rice instead of water is that starch in the grain interferes with the reaction. One approach is to modify the chemistry by replacing zinc, the hydride-generation reagent, with borohydride. However, when Rafiyu adds this to the powdered rice paste, the reaction is extremely vigorous and must be slowed to detect any arsenic present.

Tyson and Rafiyu estimate that it will take scores of experiments to identify the optimum combination of reagent, concentrations and reaction conditions. Once that is solved, they plan to replace what is now a naked-eye evaluation of color on the arsenic test strip with a method that creates a digital image, for example with a cell phone camera, for analysis.

Using that water to irrigate rice can reduce arsenic contamination, as can rinsing rice before cooking, and cooking in excess water. Tyson notes that current scientific thinking is that no arsenic exposure or intake is safe, but an “acceptable risk threshold” of 1 in 10,000 for an arsenic-induced cancer is generally viewed as sensible and achievable. 

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Taxonomy

• Public Health
• Arsenic
• Arsenic Mitigation
• Crop Farming