Impacts of farmed fish consumption and food trade on methylmercury exposure in China

Abstract

The global pollutant mercury (Hg), especially as methylmercury (MeHg), threatens human and ecosystem health. But major contributors of MeHg exposure to people in China remain highly debated. We developed the China Mercury Exposure Assessment (CMEA) model, which incorporates human exposure pathways for MeHg and total Hg (THg), the interregional, including international and interprovincial, food trading as well as human physiology to provide a comprehensive system that can evaluate the pathway of Hg forms to human consumers in China. Based on the CMEA model that employed the most comprehensive and recent data, we have found that the probable daily intake (PDI) of MeHg for the Chinese population was 0.057 (range: 0.036 – 0.091 as 60% confidence interval) μg·kg−1·day−1, while that of THg was 0.35 (range: 0.22 – 0.55) μg·kg−1·day−1. MeHg exposure was dominated by fish intake, especially by farm-raised freshwater fish due to higher consumption of these fish. In 2011, fish intake contributed to 56% to the total MeHg exposure, followed by rice (26%). Consumption of farm-raised fish reduced human exposure to MeHg by 33%. On the other hand, interregional food trading increased MeHg exposure of the Chinese population, as a whole, by 7.6%. The international and interprovincial food trades contributed to 5.1% and 22% of MeHg intake, respectively. For the whole China, fish intake related exposure to MeHg was highest for the Eastern and Northeastern populations, while Tibetans were chronically exposed to the highest MeHg from other sources. Our findings highlight the importance of farmed fish and food trade for MeHg exposure.

Trans-provincial health impacts of atmospheric mercury emissions in China

“…Previous studies have suggested that the changes in MeHg concentrations were driven by THg availability 47,48 , such as the significant linear correlation between THg and MeHg in fish 14 and the logarithmic linear correlation between THg and MeHg in rice 56 . Here, following our previous studies 46,55 , we establish the best linear correlation between THg and MeHg concentrations for certain food products whose published data are abundant ( n > 10), such as rice, vegetables, marine fish, and freshwater fish. For food products with limited data (i.e., beans, pork, poultry, and eggs), we average the ratios of MeHg to THg concentration using the limited paired data (see Supplementary Data 4).…”

“…According to previous studies 23,46 , the following 10 categories of Hg-containing food products are selected as the main intake pathways of total Hg (THg; THg = MeHg + IHg) and MeHg for the Chinese population in this study: rice, wheat, beans, vegetables, pork, poultry, milk, eggs, marine fish, and freshwater fish. Here, marine fish and freshwater fish include major fish species in China (e.g., grass carp, crucian carp, common carp, catfish, silver pomfret, and yellow croaker) and other aquatic products (e.g., shrimp, crab, and shellfish).…”

“…We compile an intake inventory of MeHg for the Chinese population at the provincial scale based on our previous study 46 . The method in our previous study was used to compile an intake inventory at the regional scale, such as the intake of MeHg for the population in Central China.…”

“…Concentrations of THg and MeHg in food products harvested in specific provinces are collected from previous studies conducted by authoritative scientific research institutions in China and published in peer-reviewed journals (see Supplementary Data 4). Some data are retrieved from our previous study 46 , but we classify the data from the regional scale to the provincial scale according to the location information from previous literature. The Chinese government has set limits for concentrations of THg or MeHg in food products (see Supplementary Data 4); thus, we assume that the food products whose THg or MeHg concentrations exceed the limits would not be allowed to circulate in markets and are hence not considered in our analysis.…”

Occurrence and Fate of Heavy Metals in Municipal Wastewater in Heilongjiang Province, China: A Monthly Reconnaissance from 2015 to 2017

“…This might potentially pose a health risk to humans. For example, previous studies suggested that Hg released into paddy soil could be methylated and accumulated in rice grains, which could subsequently become a significant dietary source for inhabitant Hg exposure [55,56]. Similarly, As, Cd, and Cr can also enter the food chain and become widely distributed throughout plants and animals, and thereby pose a risk to humans and wildlife [57][58][59].…”