Groundwater Irrigation and Arsenic Speciation in Rice in Cambodia

Abstract

Background.Arsenic bioaccumulation in rice is a global concern affecting food security and public health.Objective.The present study examined arsenic species in rice in Cambodia to characterize health risks with rice consumption and to clarify uncertainties with Codex guidelines.Methods.The present study collected 61 well water samples, 105 rice samples, 70 soil samples, and conducted interviews with 44 families in Preak Russey near the Bassac River and Kandal Province along the Mekong River in Cambodia. Analyses of metals, total arsenic and arsenic species were conducted in laboratories in Canada, Cambodia and Singapore.Results.Unlike in Bangladesh, rice with the highest total arsenic concentrations in Cambodia contains mostly organic arsenic, dimethylarsinic acid (DMA), which is unregulated and much less toxic than inorganic arsenic. The present study found that storing surface runoff in ditches prior to irrigation can significantly reduce the arsenic concentration in rice. It is possible to remove > 95% of arsenic from groundwater prior to irrigation with natural reactions.Conclusions.The provision of high quality drinking water in 2015 to Preak Russey removed about 95% of the dietary inorganic arsenic exposure. The extremes in arsenic toxicity that are still obvious in these farmers should become less common. Rice from the site with the highest documented levels of arsenic in soils and water in Cambodia passes current Codex guidelines for arsenic.Informed Consent.ObtainedCompeting Interests.The authors declare no competing financial interests.

Environmental and Health Implications of the Correlation Between Arsenic and Zinc Levels in Rice from an Arsenic-Rich Zone in Cambodia

“…Both sites are mainly flood plains with farms with very similar agricultural techniques. Many of the rice samples in the present analysis were collected from farmers in 2016 as part of an earlier International Development Research Center (IDRC/CRDI)-funded project 4,38. Farmers in these areas hire combines to harvest their rice.…”

“…We also compare the zinc content of rice grain to the Codex standards for zinc in Infant and Follow-Up Formula and to zinc levels in countries with national programs for micronutrient fortification of rice. In part, it is an evaluation of a phenomenon of chlorotic rice observed in an earlier study in Preak Russey and is an extension of that study 436,37.…”

“…Drinking water had been the major source of arsenic. All rice passed the current Codex standards for arsenic 4. However the bioaccumulation of arsenic into rice via irrigation with groundwater could increase the probability of cancer 4,5.…”

“…All rice passed the current Codex standards for arsenic 4. However the bioaccumulation of arsenic into rice via irrigation with groundwater could increase the probability of cancer 4,5. In areas of Bangladesh with clean drinking water, consumption of rice with more than 200 μg/kg of arsenic is associated with significantly higher levels of cancer, and some rice in Cambodia has more than double this threshold 4–6…”

“…The current study took advantage of the speed and simplicity of handheld X-ray fluorescence (XRF) analysis to monitor zinc concentrations in rice grain 36,37. The rice had already been collected in the earlier study 4,38…”