High arsenic in rice is associated with elevated genotoxic effects in humans

Abstract

Arsenic in drinking water may cause major deleterious health impacts including death. Although arsenic in rice has recently been demonstrated to be a potential exposure route for humans, there has been to date no direct evidence for the impact of such exposure on human health. Here we show for the first time, through a cohort study in West Bengal, India, involving over 400 human subjects not otherwise significantly exposed to arsenic through drinking water, elevated genotoxic effects, as measured by micronuclei (MN) in urothelial cells, associated with the staple consumption of cooked rice with >200 μg/kg arsenic. Further work is required to determine the applicability to populations with different dietary and genetic characteristics, but with over 3 billion people in the world consuming rice as a staple food and several percent of this rice containing such elevated arsenic concentrations, this study raises considerable concerns over the threat to human health.

Figure 1. Cross-plot of mean urinary arsenic vs mean cooked rice arsenic.

The linear best-fit trendline is indicative only. Error bars represent ± 1 standard deviation for each parameter for each exposure group (A–F).

Figure 2. Urothelial cell genetic damage, as measured by frequency (per 1000 cells) of induction of micronuclei (MN), as a function of total arsenic concentration (CR-As) in consumed cooked rice, grouped as indicated.

For this rural West Bengal population consuming rice as a staple, high arsenic in cooked rice is associated with elevated genotoxic effects. All groups with a mean As in cooked rice >200 μg/kg (D, E, F) have mean micronuclei frequencies (MN/1000 cells) significantly higher (p < 0.05) than those of the lower exposure groups (A, B, C). Numbers in each group as in Table 1.

Figure 3. Cross-plot of urothelial micronuclei frequency (MN/1000 cells) and arsenic content in cooked rice for grouped data.

(a) males (squares) and females (circles); (b) tobacco-users (squares) and tobacco-non-users (circles); (c) groups from each of the 3 study areas, viz. Murshidabad (squares), Nadia (circles) and East Midnapur (triangles). The linear best-fit trendlines are indicative only. Error bars represent ± 1 standard deviation for each parameter for each exposure group (A–F).

Figure 4. Cross-plot of urothelial micronuclei frequency (MN/1000 cells) and urinary arsenic content for grouped data.

The linear best-fit trendline is indicative only. Error bars represent ± 1 standard deviation for each parameter for each exposure group (A–F). Data from this study (diamonds): for which arsenic exposure is predominantly from cooked rice and from Basu et al. (squares) and Ghosh et al. (circles), both for which arsenic exposure is predominantly from drinking water.