Vegetable Houttuynia cordata Thunb. as an important human mercury exposure route in Kaiyang county, Guizhou province, SW China.

Consumption of mercury (Hg) contaminated vegetable is one important pathway of Hg expose to humans. In this study, Hg contents in a popular vegetable, Houttuynia cordata Thunb. (HCT), and its growing soils in Kaiyang county in Guizhou province of southwest China were investigated. Health risk related to Hg exposure through consumption of this vegetable was evaluated for the first time. Hg contents in HCT were found to be much higher in three towns in western Kaiyang county (42.3 +/- 48.2 mug/kg, FW), where former Hg mines located, than that in other towns (7.6 +/- 5.0 mug/kg, FW). Hg contents in HCT were also higher than in the other five vegetables (Chinese cabbage, Lettuce, Tomato, Carrot and White radish). Consumption of HCT may account for 37.4-61.1% of total vegetable Hg intake of local people in Kaiyang county. Hg concentration in HCT positively correlated with that in soil (r(2) = 0.311, p < 0.01), especially, the labile Hg species (FC1, r(2) = 0.796, p < 0.01) and the elemental Hg that is bound to the crystalline oxides (FC3, r(2) = 0.711, p < 0.01), and negatively correlated with Hg that is bound to humic and fulvic complexes (FC2, - 0.304). Estimated daily intake (EDI) and target hazard quotient (THQ) results shown that Hg expose risk is much higher for children than adults, likely due to their different eating habits and the amount of snack intake.