Stool as a novel biomarker for arsenic exposure through diet: a case-control study in a West Bengal population Original paper

What was studied?

This study focused on evaluating arsenic exposure through diet by assessing stool samples in populations from West Bengal, India. Given that arsenic exposure via drinking water is well-documented, the researchers aimed to explore whether stool could serve as a reliable biomarker for arsenic exposure through the food chain, particularly in areas where groundwater arsenic contamination is prevalent. By comparing stool and urine arsenic concentrations between exposed and control populations, the study sought to validate stool as a viable marker for dietary arsenic exposure, particularly as many exposed individuals continue to consume arsenic-laden food despite access to safer drinking water.

Who was studied?

The study participants included two groups: the case group from arsenic-affected regions in Nadia, West Bengal, and a control group from the less-exposed district of Paschim Medinipore. The case group consisted of individuals exposed to higher levels of arsenic through dietary sources, primarily rice and groundwater used for cooking, while the control group comprised individuals with minimal arsenic exposure. The subjects were aged 28–60, and both males and females participated, with a total of 60 individuals (24 exposed and 36 control participants). The researchers aimed to assess the correlation of stool arsenic levels with urinary arsenic and environmental arsenic contamination levels.

Most important findings

The results showed significant differences in arsenic concentrations between the case and control populations, with the exposed group displaying higher arsenic levels in both stool and urine. The average stool arsenic concentration in the exposed population was 234 µg/kg, compared to 66 µg/kg in the control group. Similarly, urinary arsenic levels were markedly higher in the exposed group (142 µg/L) than in the control group (0.61 µg/L). These findings were further supported by statistical analysis, including Pearson’s correlation, which demonstrated a positive correlation between stool arsenic and groundwater arsenic in both groups, particularly in the exposed population. The correlation between urinary and stool arsenic was also strong in the case group (r = 0.52), further reinforcing the potential of stool as a biomarker for arsenic exposure through diet.

Moreover, multi-metal analysis showed a negative correlation between stool arsenic and most other heavy metals in the exposed group, while the control group showed opposite correlations. These differences were also reflected in the principal component analysis (PCA), which suggested a distinct pattern of arsenic and heavy metal interactions in the stool of the exposed individuals. This analysis supports the hypothesis that stool arsenic is not only reflective of dietary exposure but also correlated with other environmental contaminants.

Key implications

The findings of this study have significant implications for environmental health monitoring and arsenic exposure assessment. First, the study provides evidence that stool arsenic concentration can serve as a reliable biomarker for arsenic exposure through diet, particularly in areas where contaminated groundwater is used for cooking. This could help mitigate the challenges associated with using urine as a sole biomarker for arsenic exposure, as urine primarily reflects arsenic intake through drinking water. The ability to assess arsenic exposure through non-invasive stool samples offers a more accessible and potentially more accurate method for monitoring dietary arsenic exposure, especially in rural or resource-limited settings. Furthermore, this research highlights the need for increased awareness and regulatory measures to limit arsenic exposure from food sources like rice, pulses, and vegetables, which are commonly contaminated in regions with high groundwater arsenic levels.