Modeled methylmercury exposure and risk from rice consumption for vulnerable populations in a traditional fish-eating area in China

The circulation of rice from contaminated areas could escalate exposure risk from a local problem to a national issue and affect a wider population beyond the region of origin, as confirmed by the "Poison Rice Incident" in May 2013 in Guangzhou, China. In the present study, the authors established a food chain model based on the aquivalence method to identify major sources of methylmercury (MeHg), estimate the levels of MeHg, and quantify exposure to MeHg via rice and aquatic food consumption. Different types of organism samples from the Haihe River also were collected to verify the calculated values. The MeHg intake in pregnant women was 1529.1ng/d from the aquatic food chain and as high as 2804.0ng/d from rice, although the intake varied among scenarios. The maximum possible MeHg concentration in the blood of pregnant women was 5.21μg/L, higher than the threshold value of MeHg recommended by the US Environmental Protection Agency (4.4μg/L), which indicated that pregnant women could face risk from MeHg exposure. The authors also assessed the risk of MeHg exposure in pregnant women and their breastfed infants using a new index, HQ_Equivalent. In 4 scenarios, the HQ_Equivalent indices ranged from 0.42 to 1.18 for pregnant women and from 0.29 to 0.83 for breastfed infants.