Risk assessment for human health in a seleniferous area, Shuang'an, China

Shuang'an in Ziyang is a typical high-selenium (Se) area in China, where human selenium (Se) poisoning was reported 30 years ago. To assess the risk of Se poisoning in the area, the Se content in agricultural soil, plant, and water in Naore, Shuang Hekou, and Lin Benhe villages of Ziyang was systematically investigated. The probable daily intake (PDI) was calculated on the basis of Se contents in food, water, and dietary habits to evaluate the risk of selenosis. Se content in hair from local habitants (32 men and 34 women) was determined to further verify the risk. Results showed that Se content in the soil ranged from 0.21 to 36.07 mg/kg, with a geometric means of 3.02 +/- 5.16 mg/kg, respectively. Approximately 60% of soil reached the Se toxicity threshold (> 3 mg/kg). The Se content in plants ranged from 0.02 to 17 mg/kg, with an average of 0.76 +/- 2.51 mg/kg. Approximately 40% of the plant reached the toxicity standard (1 mg/kg). Se content in soil and plant of Naore village was significantly higher than that from two adjacent villages. The Se content in vegetables (on fresh weight basis) was higher than that in cereals. Se contents were 3.73 +/- 9.08 and 1.32 +/- 3.50 mg/kg in eggplant and pepper, respectively. The Se content in drinking water was 7.85 +/- 6.04 mu g/L, lower than the upper tolerable limit (40 mu g/L) set by WHO. The Se content in stream water (18.5 mu g/L) was significantly higher than that in drinking water because of soil erosion. The calculated PDI of habitants in Naore village (1801 mu g/day) was significantly higher than that in Lin Benhe (666 mu g/day) and Shuang Hekou (686 mu g/day), all of which was higher than the tolerable upper Se intake (400 mu g/day) set by WHO. The calculated blood Se content was relatively high, especially for habitants of Naore village (2783-2824 mu g/L). Moreover, the Se content in the hair of local habitants reached as high as 12.72 +/- 13.81 mg/kg, and 78.79% exceeded hair Se toxicity threshold (> 3 mg/kg), which further verified the potential selenosis risk. Our study provides significant implications of the potential Se intoxication of local residents. Therefore, governments and other institutions should implement various measures to reduce the daily Se intake and to mitigate the associated health risks.