Rice life cycle-based global mercury biotransport and human methylmercury exposure

Maodian Liu,Huizhong Shen,Hanlin Cao,Xuejun Wang,Menghan Cheng,Shu Tao,Wei Zhang,Qianru Zhang,Yipeng He,Long Chen,Haoran Zhang

doi:10.1038/s41467-019-13221-2

Abstract

Protecting the environment and enhancing food security are among the world’s greatest challenges. Fish consumption is widely considered to be the single significant dietary source of methylmercury. Nevertheless, by synthesizing data from the past six decades and using a variety of models, we find that rice could be a significant global dietary source of human methylmercury exposure, especially in South and Southeast Asia. In 2013, globalization caused 9.9% of human methylmercury exposure via the international rice trade and significantly aggravated rice-derived exposure in Africa (62%), Central Asia (98%) and Europe (42%). In 2016, 180 metric tons of mercury were generated in rice plants, 14-fold greater than that exported from oceans via global fisheries. We suggest that future research should consider both the joint ingestion of rice with fish and the food trade in methylmercury exposure assessments, and anthropogenic biovectors such as crops should be considered in the global mercury cycle.

Highlights

Protecting the environment and enhancing food security are among the world’s greatest challenges
We found that rice plants contributed a significant amount to the global anthropogenic biovectors of Hg (Figs. 1 and 2, Supplementary Figs. 1–8 and Supplementary Data 1–3)
The amount of THg that was generated in rice plants was higher than the amount that was exported from the ocean via global marine fisheries by a factor of 1421

Summary

Introduction

Protecting the environment and enhancing food security are among the world’s greatest challenges. Fish consumption has been considered the single significant dietary source of MeHg in most studies[11,12,13] This conclusion was recently challenged by studies in some rural areas in China, where elevated rice (Oryza sativa)-derived MeHg levels and low fish ingestion rates were reported[14]. The main objective of this study is to identify and discuss the role of rice in the Hg exposure continuum (from the environment to people), including its production, residue disposition, regional trade, human MeHg intake, and potential health impacts. We first establish 27 total Hg (THg, including all forms of Hg) and MeHg inventories covering 56 years for different countries and regions, including global rice production, import, export, stock variation, domestic supplies (including food, feed, seed, processing, losses, and other uses) and human intake and potential health impacts, as well as Hg amounts in rice residue yields and those emitted from residue burning. We find that rice could be a significant global dietary source of human MeHg exposure, especially in South and Southeast Asia, and globalization significantly aggravates the

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Conclusion