Arsenic species in wheat, raw and cooked rice: Exposure and associated health implications.
Arsenic concentrations above 10μgL-1 were previously found in 89% of ground water sources in six villages of Pakistan. The present study has ascertained the health risks associated with exposure to total arsenic (tAs) and its species in most frequently consumed foods. Inorganic arsenic (iAs) concentrations were found to be 92.5±41.88μgkg-1, 79.21±76.42μgkg-1, and 116.38±51.38μgkg-1 for raw rice, cooked rice and wheat respectively. The mean tAs concentrations were 47.47±30.72μgkg-1, 71.65±74.7μgkg-1, 105±61.47μgkg-1. Wheat is therefore demonstrated to be a significant source of arsenic exposure. Dimethylarsinic acid was the main organic species detected in rice, whilst monomethylarsonic acid was only found at trace levels. Total daily intake of iAs exceeded the provisional tolerable daily intake of 2.1μgkg-1day-1 body weight in 74% of study participants due to concurrent intake from water (94%), wheat (5%) and raw rice (1%). A significant association between tAs in cooked rice and cooking water resulted in tAs intake 43% higher in cooked rice compared to raw rice. The study suggests that arsenic intake from food, particularly from wheat consumption, holds particular significance where iAs is relatively low in water. Chronic health risks were found to be significantly higher from wheat intake than rice, whilst the risk in terms of acute effects was below the USEPA's limit of 1.0. Children were at significantly higher health risk than adults due to iAs exposure from rice and/or wheat. The dietary exposure of participants to tAs was attributable to staple food intake with ground water iAs <10μgL-1, however the preliminary advisory level (200μgkg-1) was achievable with rice consumption of ≤200gday-1 and compliance with ≤10μgL-1 iAs in drinking water. Although the daily iAs intake from food was lower than total water intake, the potential health risk from exposure to arsenic and its species still exists and requires exposure control measures.