TitleRice methylmercury exposure and mitigation: a comprehensive review.
Publication TypeJournal Article
Year of Publication2014
AuthorsRothenberg, SE, Windham-Myers, L, Creswell, JE
JournalEnviron Res
Date Published08/2014
KeywordsAgriculture, Animals, Environmental Exposure, Mercury, Methylmercury Compounds, Oryza

Rice cultivation practices from field preparation to post-harvest transform rice paddies into hot spots for microbial mercury methylation, converting less-toxic inorganic mercury to more-toxic methylmercury, which is likely translocated to rice grain. This review includes 51 studies reporting rice total mercury and/or methylmercury concentrations, based on rice (Orzya sativa) cultivated or purchased in 15 countries. Not surprisingly, both rice total mercury and methylmercury levels were significantly higher in polluted sites compared to non-polluted sites (Wilcoxon rank sum, p<0.001). However, rice percent methylmercury (of total mercury) did not differ statistically between polluted and non-polluted sites (Wilcoxon rank sum, p=0.35), suggesting comparable mercury methylation rates in paddy soil across these sites and/or similar accumulation of mercury species for these rice cultivars. Studies characterizing the effects of rice cultivation under more aerobic conditions were reviewed to determine the mitigation potential of this practice. Rice management practices utilizing alternating wetting and drying (instead of continuous flooding) caused soil methylmercury levels to spike, resulting in a strong methylmercury pulse after fields were dried and reflooded; however, it is uncertain whether this led to increased translocation of methylmercury from paddy soil to rice grain. Due to the potential health risks, it is advisable to investigate this issue further, and to develop separate water management strategies for mercury polluted and non-polluted sites, in order to minimize methylmercury exposure through rice ingestion.

Alternate JournalEnviron. Res.
PubMed ID24972509
PubMed Central IDPMC4119557
Grant ListR15 ES022409 / ES / NIEHS NIH HHS / United States
R15ES022409 / ES / NIEHS NIH HHS / United States