Significant bioaccumulation and biotransformation of methyl mercury by organisms in rice paddy ecosystems: A potential health risk to humans

Hongxia Du; Pan Guo; Tao Wang; Ming Ma; Dingyong Wang

doi:10.1016/j.envpol.2021.116431

Significant bioaccumulation and biotransformation of methyl mercury by organisms in rice paddy ecosystems: A potential health risk to humans

Environ Pollut. 2021 Jan 5:273:116431. doi: 10.1016/j.envpol.2021.116431. Online ahead of print.

Authors

Hongxia Du¹, Pan Guo², Tao Wang², Ming Ma³, Dingyong Wang⁴

Affiliations

¹ Chongqing Key Laboratory of Bio-resource for Bioenergy, Southwest University, College of Resources and Environment, Southwest University, Chongqing, 400715, China.
² Center of Molecular Ecophysiology (CMEP), College of Resources and Environment, Southwest University, Chongqing, 400715, China.
³ Chongqing Key Laboratory of Bio-resource for Bioenergy, Southwest University, College of Resources and Environment, Southwest University, Chongqing, 400715, China; Center of Molecular Ecophysiology (CMEP), College of Resources and Environment, Southwest University, Chongqing, 400715, China. Electronic address: maming@swu.edu.cn.
⁴ Chongqing Key Laboratory of Bio-resource for Bioenergy, Southwest University, College of Resources and Environment, Southwest University, Chongqing, 400715, China; Chongqing Key Laboratory of Agricultural Resources and Environment, College of Resources and Environment, Southwest University, Chongqing, 400715, China.

PMID: 33453697
DOI: 10.1016/j.envpol.2021.116431

Abstract

Rice has been confirmed as one of the principal intake pathways for methylmercury (MeHg) in human, however, the impact of edible organisms, such as snails, loaches and eels, living in the rice-based ecosystem to the overall MeHg intake has been overlooked. Here, we conducted a cross-sectional ecological study, and the results showed that bioaccumulation of MeHg in these edible organisms was significantly higher than in paddy soils and rice roots (p < 0.001), even though rice roots and grains have significantly higher total Hg (THg) (p < 0.001). The MeHg/THg ratios were consistently and significantly higher in those edible organisms than in rice grains, suggesting a potential elevated MeHg exposure risk through consumption. Based on results of bioaccumulation factors (BAFs) for MeHg, it was clear that MeHg was bioaccumulated and biotransformed from paddy soils to earthworms and then to eels, as well as from paddy soils to snails and then to eels and loaches, potentially indicating that the consumption of eels and loaches was absolutely pernicious to people regularly feeding on them. Overall, MeHg was biomagnified along the food chain of the paddy ecosystem from soil to the organisms, and it was of potential higher risks for local residents to eat them, especially eels and loaches. Therefore, it is intensely indispensable for people fond of such diets to attenuate their consumption of rice, eels and loaches, thus mitigating their MeHg exposure risks.

Keywords: Accumulation; BAFs; Mercury; Methylmercury; Organisms.