Trans-provincial health impacts of atmospheric mercury emissions in China

Mobilization and methylation of mercury with sulfur addition in paddy soil: Implications for integrated water-sulfur management in controlling Hg accumulation in rice

Sulfur-fertilizer is commonly applied in croplands and in immobilizing Hg in contaminated soil. However, there is still great uncertainty and controversy concerning Hg transportability and transformation when supplying sulfur in paddies with complex conditions. Herein, we explored the effect of adding sulfate in paddy soil at different rice growth stages on soil Hg release and MeHg accumulation in rice and uncovered the correlation between sulfur induced MeHg production and the dynamically changed soil E_h, dissolved Fe, and dissolved organic carbon (DOC). In specific, sulfate addition at early stages (flooding period) triggered the decrease of E_h and increase of DOC and dissolved Fe, which in turn promoted Hg release and favored MeHg generation (increased by 235.19-555.07% vs control). Interestingly, adding sulfate at late stages (drainage condition), as compared with that at early stages, alleviated Hg release and MeHg production accompanied by the increase of E_h and decrease of dissolved Fe and DOC. The microcosmic experiment further confirmed the reduction of sulfate to sulfide promoted the change of E_h, thereby stimulating HgS dissolution in soil extract. The results give clues on the rational application of sulfur-fertilizer and through the water-sulfur fertilizer management considering the correspondingly changed soil conditions to diminish Hg bioavailability and MeHg production in paddies and paddy-like environments.

Global Supply Chain Drivers of Agricultural Antibiotic Emissions in China

Antibiotic pollution causes serious environmental and social issues. China is the largest antibiotic producer and user in the world, with a large share of antibiotics used in agriculture. This study quantified agricultural antibiotic emissions of mainland China in 2014 as well as critical drivers in global supply chains. Results show that China's agriculture discharged 4131 tons of antibiotics. Critical domestic supply chain drivers are mainly located in Central China, North China, and East China. Foreign final demand contributes 9% of agricultural antibiotic emissions in mainland China and leads to 5-40% of emissions in each province. Foreign primary inputs (e.g., labor and capital) contribute 5% of agricultural antibiotic emissions in mainland China and lead to 2-63% of emissions in each province. Critical international drivers include the final demand of the United States and Japan for foods and textile products, as well as the primary inputs of the oil seeds sector in Brazil. The results indicate the uniqueness of supply chain drivers for antibiotic emissions compared with other emissions. Our findings reveal supply chain hotspots for multiple-perspective policy decisions to control China's agricultural antibiotic emissions as well as for international cooperation.

Possible health risk assessment for heavy metal concentrations in water, sediment, and fish species and Turkmen pregnant women's biomonitoring in Miankaleh Peninsula, Iran

This study investigated the human biomonitoring of heavy metals in the water, sediments, and tissues of mostly consumed fish species using Turkmen pregnant women's biomarkers in winter 2019, at the Miankaleh Peninsula, north of Iran. Metal concentrations were measured in various fish organs as well as pregnant women's blood, hair, and nail as biological indicators. For this purpose, a total of 20 water and sediment, 14 fish, and 16 human samples were collected. Inductively coupled plasma mass spectrometry (ICP-MS) was used to evaluate the concentration of Cr, Co, Cu, As, Hg, and Pb. Results showed metals with the highest concentrations as Cu and Cr in water (93.35 and 80.91 µg/l, respectively), Hg and Pb in sediment (7.40 µg/g for both), Cu and Pb in the liver (27.00 and 18.9 µg/g for C. carpio; 1414 and 31.7 µg/g for L. auratus), muscle (10.00 and 18.80 for C. carpio; 37.20 and 8.27 µg/g for L. auratus), and skin (26.40 and 9.90 for C. carpio; 10.80 and 11.74 µg/g for L. auratus). In addition, Cu, in pregnant women samples, had the highest values at 2.53 mg/l, 8.87, 36.46, and 29.04 µg/g for blood, hair, fingernail, and toenail, respectively. However, Co showed the lowest concentration in all studied samples. Fish liver and fingernail of pregnant women did reveal the highest heavy metal accumulation, whereas fish muscle and blood of pregnant women had the lowest accumulated heavy metals. The concentration of Hg in water, sediment, fish muscle, and women's blood and hair exceeded the limits suggested by various organizations. Therefore, this study highlighted that heavy metal concentration, in particular Hg, in water, sediments, and fish is a serious risk to the health of local inhabitants who rely on fisheries products and recommended that necessary information should be provided to warn Turkmen pregnant women in consumption of Hg-contaminated fish in this area.

Looping Mercury Cycle in Global Environmental-Economic System Modeling

The Minamata Convention on Mercury calls for Hg control actions to protect the environment and human beings from the adverse impacts of Hg pollution. It aims at the entire life cycle of Hg. Existing studies on the Hg cycle in the global environmental-economic system have characterized the emission-to-impact pathway of Hg pollution. That is, Hg emissions/releases from the economic system can have adverse impacts on human health and ecosystems. However, current modeling of the Hg cycle is not fully looped. It ignores the feedback of Hg-related environmental impacts (including human health impacts and ecosystem impacts) to the economic system. This would impede the development of more comprehensive Hg control actions. By synthesizing recent information on Hg cycle modeling, this critical review found that Hg-related environmental impacts would have feedbacks to the economic system via the labor force and biodiversity loss. However, the interactions between Hg-related activities in the environmental and economic systems are not completely clear. The cascading effects of Hg-related environmental impacts to the economic system throughout global supply chains have not been revealed. Here, we emphasize the knowledge gaps and propose possible approaches for looping the Hg cycle in global environmental-economic system modeling. This progress is crucial for formulating more dynamic and flexible Hg control measures. It provides new perspectives for the implementation of the Minamata Convention on Mercury.

Bioavailability and methylation of bulk mercury sulfide in paddy soils: New insights into mercury risks in rice paddies

Mercury sulfide (HgS) constitutes the largest Hg reservoir in the lithosphere but has long been considered to be not bioavailable and a minor participant in Hg biogeochemical cycling. Herein, we report that bulk α-HgS can be dissolved and methylated in paddy soils, especially with rice culture. Bulk α-HgS exposure did not affect rice growth compared to the control group but significantly increased methylmercury (MeHg) contents in the rhizospheric soils (e.g., 80.15% and 108.71% higher for bulk α-HgS treatment vs. control at the seedling and maturation stages, respectively). Moreover, bulk α-HgS exposure induced an apparent accumulation of MeHg (50% higher for bulk α-HgS treatment vs. control) and markedly elevated total Hg (THg) in rice grains. The presence of DOM and reduced sulfide in paddy soils was further evidenced to drive the mobilization and dissolution of bulk α-HgS, thereby resulting in THg and MeHg accumulation in rice grains. These findings highlight the bioavailability of HgS in rice paddies and suggest that bulk HgS should be considered when assessing Hg health risks and developing efficient remediation approaches in Hg-contaminated croplands.

Thiol-functionalized montmorillonite prepared by one-step mechanochemical grafting and its adsorption performance for mercury and methylmercury

The preparation of low-cost and highly efficient functional materials for the cleanup of mercury-contaminated water by adsorption in an environmentally friendly way is of great significance. In this study, thiol-functionalized montmorillonite (BSH-MMT) was prepared by a novel one-step mechanochemical grafting method and applied to aqueous Hg²⁺ and CH₃Hg⁺ adsorption. Characterization results showed that thiol groups were successfully grafted by chemical bonding with Si-OH or broken SiO bonds. The maximum adsorption capacities of BSH-MMT for Hg²⁺ and CH₃Hg⁺ were 104.79 mg g^-1 and 39.27 mg g^-1, which were approximately seven- and nine-fold that of pristine MMT, respectively. Adsorption kinetics and isotherm fitting indicated that Hg²⁺ adsorbs heterogeneously, while CH₃Hg⁺ proceeds through monolayer adsorption, both with chemical adsorption as the rate-limiting step. BSH-MMT maintained high adsorption performance over a wide pH range and in the presence of humic acid because of the high affinity of thiol groups toward mercury. The primary adsorption mechanism of thiol-ligand complexation was confirmed by the results of X-ray photoelectron spectroscopy and X-ray absorption spectra, in which a complex structure of bis-coordinated S-Hg-S (2.30 Å distance) was observed. These results demonstrated that mechanochemical grafting is a promising one-step method to prepare thiol-functionalized montmorillonite for effective cleanup of Hg²⁺/CH₃Hg⁺ contamination in water.

Cascading costs of snow cover reduction trend in northern hemisphere

Environmental changes in response to global warming would conversely deplete the efficacy of our actions combating climate change, cultivating extra cost. Among them, the declining snow cover due to global warming would diminish its contribution to climate regulation, and further exacerbate global warming. This leads to a part of global carbon mitigation efforts acting virtually to neutralize the impact of snow cover reduction. It would have been otherwise saved to contribute to the goals of the Paris Agreement. In this respect, here we evaluate the economic impacts of snow cover reduction in the Northern Hemisphere in terms of the mitigation that virtually counteracts the loss of climate regulation pertinent to the snow cover reduction trend, to demonstrate the magnitude of the cascading costs of climate change. As different carbon mitigation approaches would lead to different economic impacts, we follow the general principles of the Paris Agreement and establish two responsibility-sharing scenarios. The results reveal the non-negligible global costs considering not only the impact incurred by the nations implementing carbon mitigation but also, in the context of globalization, the cascading effect magnified in the global supply chain. We also identify critical nations, sectors, and international trade pairs that would confront the most costs. The results urge hotspot nations and trade partners to actively participate in the enhanced global efforts through the Paris Agreement to reduce carbon emissions. This can not only mitigate its direct global warming effect, but also abate the impacts of collateral environmental deterioration, such as snow cover reduction, eventually for their own benefits.

Unravelling the interactive effect of soil and atmospheric mercury influencing mercury distribution and accumulation in the soil-rice system

Mercury (Hg) accumulation in rice is an emerging health concern worldwide. However, sources and interactions responsible for Hg species accumulation in different rice tissues are still uncertain. Four experimental plots were carefully designed at an artisanal Hg mining site and a control site to evaluate the effect of atmospheric and soil Hg contents on Hg accumulation in rice. We showed that inorganic Hg (IHg) contents in rice tissues grown either in contaminated or control site soil (non-contaminated soil) were higher at Hg artisanal mining site than those at the control site. Elevated total gaseous mercury (TGM) levels in ambient air were the predominant source of IHg to rice at the Hg mining area. Methylmercury (MeHg) concentrations in rice plant tissues increased in proportionality with MeHg contents in paddy soil. Our results suggest that both atmosphere and soil Hg sources have been impacted the IHg accumulation in rice. Above ground rice tissues, grains, leaves, and stalk accumulated IHg from both atmosphere and soil to varying degrees. Nonetheless, the study also provides the first direct evidence that atmospheric Hg accumulated by above-ground rice tissues could be translocated to below-ground tissues (roots). However, the extent to which atmosphere or soil Hg contributes to IHg in rice tissues may vary with each source's concentration gradient at the given site. No evidence of in planta Hg methylation was found during the current study. Hence, paddy fields are potential MeHg production sites, whereas paddy soil is a unique MeHg accumulation source in rice plants. This study expands and clarifies the contribution of various sources involved in Hg accumulation in the soil rice system. The findings here provide the basis for future research strategies to deal with the global issue of Hg contaminated rice.

Globalization-Driven Industry Relocation Significantly Reduces Arctic PAH Contamination

Industry relocation under globalization has altered the origins and strength of emission sources of many air pollutants. We develop global emission inventories of polycyclic aromatic hydrocarbons (PAHs) embodied in the production and consumption of goods and services. We implement these inventories within a global atmospheric transport model and simulate spatial-temporal changes in atmospheric concentrations of benzo[α]pyrene (BaP), the most toxic congener in unsubstituted PAHs, and depositions across the Arctic subject to global trade and industry relocation. We show that interregional trade and industry relocation dramatically reduce the atmospheric levels and deposition of BaP in the Arctic. The most significant BaP decline occurs in the European and North American Arctic regions due to attenuated sources in the two well-developed continents proximate to the polar region induced by the relocation of high-PAH pollution industries to many developing countries far from the Arctic. Although BaP emissions embodied in industry relocations in China, India, and South and Southeast Asia resulted in increased BaP contamination in the Asian Arctic, such increases in pollution are minor compared to significant BaP reductions occurring in the European and North American Arctic regions. We find that "North-to-South" industry transfer could reduce trade-related BaP contamination by 60% in the Arctic.

Global Trends and Drivers in Consumption- and Income-Based Emissions of Polycyclic Aromatic Hydrocarbons

Polycyclic aromatic hydrocarbons (PAHs) are a class of the most hazardous substances. As unavoidable byproducts of petrogenic and pyrogenic processes, their emissions are dominantly linked to various economic sectors. In international trade, not only final consumption but also primary input can transfer the emissions among regions. Therefore, a long-term impact assessment of the international trade on PAH global emissions based on the final consumption and primary input could significantly benefit worldwide PAH mitigation strategies. This study investigated the changes in consumption- and income-based PAH emissions and interregional flows of worldwide regions, using the latest available data from 1999 to 2014. Results show that in 2014, 16.8 and 10.1% of global PAH emissions were transferred by consumption and primary input through international trade. Meanwhile, the production-, consumption-, and income-based emissions in most regions were decreasing. Furthermore, from the consumption-based perspective, sub-Saharan Africa surpassed China and became the largest net exporter of consumption-based emissions. From the income-based perspective, the net income-based outflows of India and the rest of Asia increased significantly, indicating the income-based emission leakage in emerging markets. From the socioeconomic perspective, emission intensity dominated the global decline in PAH emissions. As the two main factors driving the increase in emissions, the primary input structure (41%) had a larger effect than the final demand level (28%) from 1999 to 2014. Therefore, global cooperation, through the mitigation strategies of reducing emission factors and improving international trade patterns, is posited as an efficient strategy to reduce PAH pollution and related health risks.

Planetary Boundaries for Forests and Their National Exceedance

Achieving forest sustainability is a declared sustainable development goal (SDG 15). Measuring the safe operating space─planetary boundaries─of global forests is essential to determine global forest pressure and manage forests sustainably. Here, we quantify the forestry planetary boundary (FPB) and national forestry boundaries. Results show that, in 2015, the FPB was 7.1 billion m³ of forest stock increments. Global timber harvests account for 58.7% of the FPB. Timber harvests of 47 nations, mostly in Africa and Asia, have exceeded their national forestry boundaries. Their boundary-exceeding timber harvest is mainly driven by the final demand of developed nations (e.g., the United States and Japan) and emerging economies (e.g., India and China) through global supply chains. This study highlights the importance of the FPB in global forest management and trade-related policymaking. The findings can guide global and national forest harvesting activities and help promote international cooperation to mitigate global deforestation.

Ratiometric fluorescent probe for the on-site monitoring of coexisted Hg2+ and F- in sequence

The monitoring of mercury and fluoride ions (Hg²⁺ and F^-) has aroused wide concerns owing to the high toxicity of Hg²⁺ and the duplicitous nature of F^- to human health. As far as we known, more than 100 million people in poverty-stricken areas are still at high risk of being over-exposed to Hg²⁺ and F^- via drinking water. Simple and cost-effective luminescent methods are highly promising for on-site water monitoring in rural areas. However, the development of multipurpose luminescent probes that are accurate and sensitive remains challenging. Herein, a new strategy for rationally designing a multipurpose ratiometric probe is present. The obtained probe is consisted of two emission units with energy transfer between them, which exhibit high coordination affinities to the two coexisted toxic targets (Hg²⁺ and F^-), respectively. Thus, two distinct routes for efficiently modulating the energy transfer in the probe are present to trigger the responses to the two targets in sequence. By detecting the shift of the emission color with a smartphone, an on-site water monitoring method is successfully established with the detection limits as low as 2.7 nM for Hg²⁺ and 1.9 μM for F^-. The present study can expend the toolbox for water monitoring in rural regions.

Observation-Based Mercury Export from Rivers to Coastal Oceans in East Asia

Globally, the consumption of coastal fish is the predominant source of human exposure to methylmercury, a potent neurotoxicant that poses health risks to humans. However, the relative importance of riverine inputs and atmospheric deposition of mercury into coastal oceans remains uncertain owing to a lack of riverine mercury observations. Here, we present comprehensive seasonal observations of riverine mercury and methylmercury loads, including dissolved and particulate phases, to East Asia's coastal oceans, which supply nearly half of the world's seafood products. We found that East Asia's rivers annually exported 95 ± 29 megagrams of mercury to adjacent seas, 3-fold greater than the corresponding atmospheric deposition. Three rivers alone accounted for 71% of East Asia's riverine mercury exports, namely: Yangtze, Yellow, and Pearl rivers. We further conducted a metadata analysis to discuss the mercury burden on seawater and found that riverine export, combined with atmospheric deposition and terrestrial nutrients, quantitatively elevated the levels of total, methylated, and dissolved gaseous mercury in seawater by an order of magnitude. Our observations support that massive amounts of riverine mercury are exported to coastal oceans on a continental scale, intensifying their spread from coastal seawater to the atmosphere, marine sediments, and open oceans. We suggest that the impact of mercury transport along the land-ocean aquatic continuum should be considered in human exposure risk assessments.

The silver linings of mercury: Reconsideration of its impacts on living organisms from a multi-timescale perspective

Research on mercury (Hg), a naturally occurring element in Earth's lithosphere, has been extremely hot in the past few decades due to the outbreak of a series of disastrous poisoning incidents. However, such studies might provide us a biased view towards Hg if no thorough review about its long-term effects on living organisms from a multi-timescale perspective was performed. Hg might have played a mysterious role in critical intervals (e.g., mass extinction and oceanic anoxia events) in several geologic periods due to the elevated Hg levels induced by volcanism whereas it has long been used for various purposes in human history. Therefore, it is necessary to go through previous studies and historical records of different timescales (10⁰ to 10⁶ yr). In this work, we conducted a thorough review of Hg knowledge at three different timescales, i.e., geologic periods (10⁶ yr), human history (10³ yr), and contemporary history (10⁰ yr), summarizing recent advances and indicated potential research gaps. By doing so, we demonstrated that it is possible to achieve safe and sustainable Hg applications despite the current Hg crisis. However, such silver linings depend on a better understanding of ecosystem dynamics. Besides, considering the possible dire consequences of erupted Hg levels as suggested in geological periods, swift actions to mitigate the impacts of anthropogenic activities on the Hg cycle will be another key point. Overall, this review presented a unique perspective of Hg combining different timescales, shedding light on the importance of a better understanding of the global ecosystem as a whole and maintaining the sustainability of planet Earth in the future.

Road freight emission in China: From supply chain perspective

Freight emissions management has entered the deep-water zone. This study evaluated road freight emissions from supply chain perspective using China's 2007, 2010 and 2012 multiregional input-output table. For the first time, we quantified road freight emission based on sectors in China. Heavy industries, mining, agriculture and light industry contributed 71%,14%, 12% and 3% of total NO_x emissions in 2012 from production perspective. Construction was the largest consumption sector (43%) responsible for road freight emission from consumption perspective. Upstream transport and final product transport emitted 3.04 Tg (80%) and 0.77 Tg (20%) NO_x in 2012. Huge disparities of road freight emissions flows and allocation patterns were found across provinces in China in terms of resource endowments, geographical position and economic development. The road freight emission increased rapidly from 2007 to 2012, and economic growth effect outpaced emission control effect caused by emission standard upgrade and thus dominated the emission growth. The production structure and consumption pattern changes also promoted the emission growth. It is thus important to mitigate freight emissions with different strategies based on a certain sector's freight emissions features from the whole supply chain.

Mapping spatial supply chain paths for embodied water flows driven by food demand in China

Identifying critical spatial supply chain paths for embodied water flows driven by food demand can guide the development of more spatially explicit food-related policies for water savings. Previous studies have quantified water uses caused by food demand, but overlook intermediate transfer paths within and among regions. That is, spatial supply chain paths describing step-by-step transfer stages between water uses and final food demand have not been well characterized. Based on the multi-regional input-output model and structural path analysis, this study exhaustively identifies critical spatial supply chain paths for provincial water withdrawals driven by final food demand in China. Results show that the final demand of food products from critical sectors (e.g., agricultural products processing, rice, and swine) and regions (e.g., Xinjiang, Heilongjiang, and Guangdong) drives large amounts of water withdrawals. Critical supply chain paths indicate that agricultural products processing, food manufacturing, and catering should pay special attention to increasing the use efficiency of rice, poultry, cotton, water, and gas products, which can effectively reduce national water withdrawals. The interregional paths further provide evidence for interregional cooperation to save food-related water resources, such as the transfer of capital and technologies from agricultural products processing in Shandong to cotton production in Xinjiang and rice production in Heilongjiang. These critical supply chain paths provide spatially explicit and targeted hotspots for demand-side policies. They can also serve for the evaluation of measures in each stage of the supply chain paths.

Human Methylmercury Exposure and Potential Impacts in Central Tibet: Food and Traditional Tibetan Medicine

Methylmercury presents potent neurotoxicity to humans. Fish consumption is the leading source of human exposure to methylmercury worldwide. However, the exposure source in Tibet remains poorly understood because of the scarcity of observational data on most Tibetan foods, although high mercury levels were recently detected in some traditional Tibetan medicines. Here, the results of field investigations show that the joint consumption of traditional Tibetan medicines (TTMs), fish, and rice constitutes a primary exposure pathway to methylmercury in Tibetans and that the probable daily intake of methylmercury is close to that for many coastal regions. People who are young and high-income may have higher methylmercury exposure levels mainly because of economic development and cultural exchanges among regions. Our analysis indicates that a large proportion of the Tibetan population are likely to face a high methylmercury exposure risk and that mercury-susceptible populations in Tibet should be attentive to consuming TTMs with fish.

Status, fuzzy integrated risk assessment, and hierarchical risk management of soil heavy metals across China: A systematic review

Many reviewers have applied bibliometric analysis to conduct research on heavy metals (HMs) in Chinese soil and found that risk management decisions were biased to a certain extent due to case distribution difference and uncertainty. The previous methodologies were optimized integrating further uncertainty control and case identification in this study. A solid database was built, which included 779 cases published from 2009 to 2020. Based on the data features, the weight method was used to objectively shield extreme cases and normalize the concentrations. We conducted fuzzy eco- and health risk models via a triangular fuzzy number, and identified the risks from Pb, Cd, As, and Hg as the priority control metals. However, the national HMs risk had complex spatial heterogeneity and significant uncertainty. Thus, an "integrated risk grade criterion (IRGC)" was coupled with the risk threshold concentrations for the eco- and health risks to classify the each case. The cases above the moderate IRGC grade for Cd or Hg accounted for approximately 50%, and were mainly in the west and north of China, respectively. The high-grade areas were mostly in the south of China, including the Xijiang-Pearl River Basin and the Yangtze River Basin. It was demonstrated that warning health risks were likely a local question and that the ecological risks from Hg and Cd were considerable across China. By reviewing and summarizing the text information, high grades of soil Cd, Pb, and As were frequently reported in the villages associated with the mining industry, and certain soil Cd near suburban industrial complexes also caused warning health risks. Finally, this study proposed priority control objects for hierarchical risk management, including the identified heavy metals, areas, and pilot cities from multi-spatial scales.

Review on pollution damage costs accounting

Although the concept of damage cost accounting is already well-studied and applied, its application to pollution still lacks of an integrated accounting framework, while the spatial-temporal variability of accounting results has not been fully discussed. To fill this gap, this review frames the existing models and their limitations into static and dynamic categories, outlining the characteristics of different methods, which consider both human and non-human damages caused by pollution. Existing data sources, that could be used for accounting purposes, are detailed. Finally, this work discusses the relevance of spatial scales for the computation process, in order to obtain a more detailed information support for environmental policies for future compensatory actions. Conclusions highlights the need to develop a more comprehensive database of exposure-response relationships and to incorporate system alternatives into models to achieve a more accurate damage assessment.

Algal Organic Matter Drives Methanogen-Mediated Methylmercury Production in Water from Eutrophic Shallow Lakes

Algal blooms bring massive amounts of algal organic matter (AOM) into eutrophic lakes, which influences microbial methylmercury (MeHg) production. However, because of the complexity of AOM and its dynamic changes during algal decomposition, the relationship between AOM and microbial Hg methylators remains poorly understood, which hinders predicting MeHg production and its bioaccumulation in eutrophic shallow lakes. To address that, we explored the impacts of AOM on microbial Hg methylators and MeHg production by characterizing dissolved organic matter with Fourier transform ion cyclotron resonance mass spectrometry (FTICR-MS) and three-dimensional excitation-emission matrix (3D-EEM) fluorescence spectroscopy and quantifying the microbial Hg methylation gene hgcA. We first reveal that the predominance of methanogens, facilitated by eutrophication-induced carbon input, could drive MeHg production in lake water. Specifically, bioavailable components of AOM (i.e., CHONs such as aromatic proteins and soluble microbial byproduct-like materials) increased the abundances (Archaea-hgcA gene: 438-2240% higher) and activities (net CH₄ production: 16.0-44.4% higher) of Archaea (e.g., methanogens). These in turn led to enhanced dissolved MeHg levels (24.3-15,918% higher) for three major eutrophic shallow lakes in China. Nevertheless, our model results indicate that AOM-facilitated MeHg production could be offset by AOM-induced MeHg biodilution under eutrophication. Our study would help reduce uncertainties in predicting MeHg production, providing a basis for mitigating the MeHg risk in eutrophic lakes.

The reallocation effect of China's provincial power transmission and trade on regional heavy metal emissions

Coal-fired power plants (CFPPs) are key point sources to atmospheric heavy metal (HM) emissions in China. Unevenly distributed CFPPs lead to large-scale interregional power transmission, as well as corresponding environmental emissions transfer. However, the effect of power transmission on HM reallocation remains poorly understood. Here, we traced HM (including Hg, As, Se, Pb, Cd, and Cr) emission flows through electricity transmission and regional trade and calculated China's multi-perspective electricity-related HM emissions from 2010 to 2015. Results show that in 2015, power transmission and regional trade caused 226.5 t (14% of total emissions) and 453.6 t (28%) of HM emission flows, respectively, leading to great differences in provincial HM emissions under different perspectives (e.g., Beijing's consumption-based emission was 15.5 times higher than the city's production-based emission in 2015). Our study provides valuable insights for fairly allocating provincial HM emission reduction responsibility and formulating synergistic emission mitigation strategies among regions.

Rapidly changing coal-related city-level atmospheric mercury emissions and their driving forces

The up-to-date city-level mercury emission inventory is essential for effective mitigation policy designs due to rapid changes in energy consumption and industrial structures in Chinese cities. This study updated the atmospheric mercury emission inventory in 2015 based on the most recent information on plant-specific air pollution control devices (APCDs) and coal consumption for 45 sectors in 215 Chinese cities. Total emissions were estimated at 218 t with an uncertainty range of - 54.0% to 147%, to which coal-fired industrial boilers (CFIBs) contributed 58.1%, followed by coal-fired power plants (CFPPs, 32.7%). Mercury emissions varied significantly among cities, ranging from 0.0218 to 6.89 t. The Logistics Mean Division Index (LMDI) model was then applied to identify key factors driving mercury emission changes in 50 representative cities from 2010 to 2015. Although coal consumption increased by nearly one fifth across the 50 cities, their total emissions declined by 2.36%, largely due to energy structure adjustments and widespread installations of more efficient APCDs. However, key drivers of mercury mitigation differed widely between the cities, being driven by energy intensity improvements in Chongqing and Guangzhou (Guangdong province) and by energy structure adjustments in Wuhan (Hubei province) and Yinchuan (Ningxia province). Mitigation strategies should be tailored to reflect these differences.

Toxic effects of cadmium and lead exposure on intestinal histology, oxidative stress response, and microbial community of Pacific white shrimp Litopenaeus vannamei

Cadmium (Cd) and lead (Pb) are two hazardous pollutants that threaten shrimp farming. The intestine is an important organ for digestion and immunity. We separately exposed Pacific white shrimp Litopenaeus vannamei to 500 μg/L Cd or 500 μg/L Pb seawater for 7 days, and 45 shrimp from each group were used to evaluate the changes of intestinal histopathological, oxidative stress, and microbiota composition. After Cd and Pb exposure, shrimp intestine appeared significant mucosal damage and oxidative stress, and the microbiota variation were induced. Specifically, the abundance of the phyla Bacteroidetes and Actinobacteria were induced, that of Proteobacteria and Firmicutes were deduced. The abundances of putative beneficial bacteria (Lactobacillus, Weissella, Demequina, Formosa and Ruegeria) and potentially pathogenic bacteria (Vibrio and Photobacterium) were fluctuated. Furthermore, the nutrient metabolic function of intestinal microbes was significantly altered. We concluded that Cd and Pb exposure had negative effects on the intestinal health of shrimp.

Global health effects of future atmospheric mercury emissions

Mercury is a potent neurotoxin that poses health risks to the global population. Anthropogenic mercury emissions to the atmosphere are projected to decrease in the future due to enhanced policy efforts such as the Minamata Convention, a legally-binding international treaty entered into force in 2017. Here, we report the development of a comprehensive climate-atmosphere-land-ocean-ecosystem and exposure-risk model framework for mercury and its application to project the health effects of future atmospheric emissions. Our results show that the accumulated health effects associated with mercury exposure during 2010-2050 are $19 (95% confidence interval: 4.7-54) trillion (2020 USD) realized to 2050 (3% discount rate) for the current policy scenario. Our results suggest a substantial increase in global human health cost if emission reduction actions are delayed. This comprehensive modeling approach provides a much-needed tool to help parties to evaluate the effectiveness of Hg emission controls as required by the Minamata Convention.

DFT and Experimental Studies on the Mechanism of Mercury Adsorption on O2-/NO-Codoped Porous Carbon

The utilization of O₂ and NO in flue gas to activate the raw porous carbon with auxiliary plasma contributes to an effective mercury (Hg)-removal strategy. The lack of in-depth knowledge on the Hg adsorption mechanism over the O₂-/NO-codoped porous carbon severely limits the development of a more effective Hg removal method and the potential application. Therefore, the generation processes of functional groups on the surface during plasma treatment were investigated and the detailed roles of different groups in Hg adsorption were clarified. The theoretical results suggest that the formation of functional groups is highly exothermic and they preferentially form on a carbon surface, and then affect Hg adsorption. The active groups affect Hg adsorption in a different manner, which depends on their nature. All of these active groups can improve Hg adsorption by enhancing the interaction of Hg with a surface carbon atom. Particularly, the preadsorbed NO₂ and O₃ groups can react directly with Hg by forming HgO. The experimental results confirm that the active groups cocontribute to the high Hg removal efficiency of O₂-/NO-codoped porous carbon. In addition, the mercury temperature-programmed desorption results suggest that there are two forms of mercury present on O₂-/NO-codoped porous carbon, including a carbon-bonded Hg atom and HgO.

Atmospheric mercury pollution caused by fluorescent lamp manufacturing and the associated human health risk in a large industrial and commercial city

Although already eliminated in most industrial processes, mercury, as an essential ingredient in all energy-efficient lighting technologies, is still used in fluorescent lamp manufacturing. This study was conducted to investigate the atmospheric pollution caused by fluorescent lamp production and assess the associated public health risk in a large industrial and commercial city of south China, Zhongshan, which is a major production hub of lighting products. Concentrations of total gaseous mercury (TGM) in the atmosphere were measured over a total of 342 sites in the industrial, commercial, and residential areas. The average levels of TGM in the industrial, commercial, and residential areas prior to the landing of a typhoon were 12 ± 11, 3.6 ± 2.1, and 2.7 ± 1.3 ng⋅m^-3, respectively. TGM concentrations in the industrial areas exhibited significant diurnal variation, with levels in the working hours being much higher than those in the non-working hours, which indicates that the high atmospheric mercury concentrations were contributed by local emissions, instead of regional transport. Most fluorescent lamp manufacturing activities in the city were shut down during a typhoon event, which resulted in a significant reduction in the average TGM level (down to 1.6 ± 1.8 ng⋅m^-3) and rendered the difference in the average TGM levels in the industrial areas no longer significant between the working and non-working hours. Elevated TGM levels (up to 49 ng⋅m^-3) were found near clusters of small-scale fluorescent lamp workshops in both industrial and commercial areas, which is indicative of significant emissions of mercury vapor resulting from obsolete equipment and production technologies. No significant non-carcinogenic risk was found for the general residents in the sampling area over the study period, while the risk for the workers in the fluorescent lamp manufacturing facilities and workshops could be higher. These findings indicate that fluorescent lamp manufacturing in the developing countries is a major source of atmospheric mercury.

Impact of emission reductions and meteorology changes on atmospheric mercury concentrations during the COVID-19 lockdown

Controlling anthropogenic mercury emissions is an ongoing effort and the effect of atmospheric mercury mitigation is expected to be impacted by accelerating climate change. The lockdown measures to restrict the spread of Coronavirus Disease 2019 (COVID-19) and the following unfavorable meteorology in Beijing provided a natural experiment to examine how air mercury responds to strict control measures when the climate becomes humid and warm. Based on a high-time resolution emission inventory and generalized additive model, we found that air mercury concentration responded almost linearly to the changes in mercury emissions when excluding the impact of other factors. Existing pollution control and additional lockdown measures reduced mercury emissions by 16.7 and 12.5 kg/d during lockdown, respectively, which correspondingly reduced the concentrations of atmospheric mercury by 0.10 and 0.07 ng/m³. Emission reductions from cement clinker production contributed to the largest decrease in atmospheric mercury, implying potential mitigation effects in this sector since it is currently the number one emitter in China. However, changes in meteorology raised atmospheric mercury by 0.41 ng/m³. The increases in relative humidity (9.5%) and temperature (1.2 °C) significantly offset the effect of emission reduction by 0.17 and 0.09 ng/m³, respectively, which highlights the challenge of air mercury control in humid and warm weather and the significance of understanding mercury behavior in the atmosphere and at atmospheric interfaces, especially the impact from relative humidity.

An improved weighted index for the assessment of heavy metal pollution in soils in Zhejiang, China

Soil heavy metal pollution assessment is an important procedure in soil quality and ecological risk management, for which different mathematical models have been developed. However, these models have often failed to consider the characteristics of both heavy metals and the polluted sites. In this study, we analyzed the concentrations of seven heavy metals in soils in Zhejiang Province, China, and developed an improved weighted index (IWI) model to evaluate pollution levels. In contrast to traditional models, weights were assigned to different heavy metals using statistical tools, including hierarchical cluster analysis and principal component analysis. Of the 89 sites, 61.8% were considered unpolluted with IWI values < 1; 32.58% were slighted polluted with IWI values from 1 to 2, and only 2.25% of the sites were seriously polluted with IWI values > 3. The IWI results agree well with two traditional integrated index models, but can be also applied to much wider heavy metal concentration ranges. Possible pollution sources were then proposed based on the IWI model. The IWI overcame several shortcomings of the traditional indices and could be very beneficial for assessing heavy metal pollution in soil. Overall, this study developed a new model for soil pollution assessment and soil ecological risk management and comprehensively evaluated the current pollution status of soil surrounding potable surface water sources in Zhejiang Province, China.

Spatially Explicit Global Hotspots Driving China's Mercury Related Health Impacts

Over 100 nations signed the Minamata Convention on Mercury to control the adverse effects of mercury (Hg) emissions on human beings. A spatially explicit analysis is needed to identify the specific sources and distribution of Hg-related health impacts. This study maps China's Hg-related health impacts and global supply chain drivers (i.e., global final consumers and primary suppliers) at a high spatial resolution. Here we show significant spatial heterogeneity in hotspots of China's Hg-related health impacts. Approximately 1% of the land area holds only 40% of the Chinese population but nearly 70% of the fatal heart attack deaths in China. Moreover, approximately 3% of the land area holds nearly 60% of the population but 70% of the intelligence quotient (IQ) decrements. The distribution of hotspots of China's Hg-related health impacts and global supply chain drivers are influenced by various factors including population, economy, transportation, resources, and dietary intake habits. These spatially explicit hotspots can support more effective policies in various stages of the global supply chains and more effective international cooperation to reduce Hg-related health impacts. This can facilitate the successful implementation of the Minamata Convention on Mercury.

Rapid Increase in Cement-Related Mercury Emissions and Deposition in China during 2005-2015

The cement industry has become the largest mercury (Hg) emission source in China. Better understanding Hg emission and deposition characteristics and drivers of Hg emission changes can increase the awareness of related risks and support effective policy making. The results show that due to the substantial increase in the use of new suspension preheater and precalciner (NSP) technology in China, an approximate two-fold increase from 80.0 to 144.0 Mg year^-1 was observed for the cement-related Hg emissions during 2005-2015, which has resulted in a considerable increase in atmospheric deposition over terrestrial China from 37.9 to 75.9 Mg year^-1. Compared to the great majority of emission sectors, the same increase in Hg emissions from cement production can cause more deposition due to the large share of highly water-soluble divalent Hg in the sector. Each 1% increase in the share of divalent Hg can result in an increase of 0.37 Mg year^-1 in deposition over terrestrial China. Technical improvement and diversification of cement products are two major driving forces offsetting the economy-induced growth in cement-related Hg emissions during 2005-2015. Measures aimed at reducing the Hg emission intensity against the further increase in the use of NSP technology and avoiding overcapacity against the stimulation of real estate and increasing cement demands are urgently needed for the cement industry in China.

Mercury in traditionally foraged species of fungi (macromycetes) from the karst area across Yunnan province in China

The objective of this study is to better quantify the occurrence, intake, and potential risk from Hg in fungi traditionally foraged in SW China. The concentrations and intakes of Hg were measured from 42 species including a "hard" flesh type polypore fungi and a" soft" flesh type edible species that are used in traditional herbal medicine, collected during the period 2011-2017. Three profiles of forest topsoil from the Zhenyuan site in 2015 and Changning and Dulong sites in 2016 were also investigated. The concentrations of Hg in composite samples of polypore fungi were usually below 0.1 mg kg-1 dry weight (dw) but higher levels, 0.11 ± 0.01 and 0.24 ± 0.00 mg kg-1 dw, were noted in Ganoderma applanatum and Amauroderma niger respectively, both from the Nujiang site near the town of Lanping in NW Yunnan. Hg concentrations in Boletaceae species were usually well above 1.0 mg kg-1 dw and as high as 10 mg kg-1 dw. The quality of the mushrooms in this study in view of contamination with Hg showed a complex picture. The "worst case" estimations showed probable intake of Hg from 0.006 μg kg-1 body mass (bm) ("hard" type flesh) to 0.25 μg kg-1 bm ("soft" flesh) on a daily basis for capsulated products, from 17 to 83 μg kg-1 bm ("soft" flesh) in a meal ("hard" type flesh mushrooms are not cooked while used in traditional herbal medicine after processing), and from 0.042 to 1.7 and 120 to 580 μg kg-1 bm on a weekly basis, respectively. KEY POINTS: • Polypore species were slightly contaminated with Hg. • Hg maximal content in the polypore was < 0.25 mg kg-1 dry weight. • Many species from Boletaceae family in Yunnan showed elevated Hg. • Locals who often eat Boletus may take Hg at a dose above the daily reference dose.

Policy adjustment impacts Cd, Cu, Ni, Pb and Zn contamination in soils around e-waste area: Concentrations, sources and health risks

Pollution control policies (PCP) have been implemented in some e-waste dismantling areas in China to curb metal contamination since 2012. We investigated the effects of policy intervention on the concentrations, sources and health risks of heavy metals in soils. Post-implementation, among Cd, Cu, Ni, Pb and Zn, Pb levels declined while the Cd, Cu, Ni and Zn concentrations in soils were not impacted. Changes in their pollution indices and health risks were also similar. After the PCP, the contribution of traffic emission significantly decreased, while natural and industrial contribution increased due to the heighten background input and relocation of small e-waste dismantling workshops. Risk assessment showed that total cancer risk of five metals also slightly increased. Thus, policy intervention might be effective in controlling the release of some metals from e-waste dismantling. However, the performance of control measures varied depending on both source emission and geochemical properties of the metals. This study reveal the ongoing need of stricter supervision, targeted emission reduction and more-effective soil remediation actions to alleviate soil contamination from e-waste dismantling.

CO2 Emissions Embodied in International Migration from 1995 to 2015

While present international CO₂ mitigation agreements account for the impact of population composition and structure on emissions, the impact of international migration is overlooked. This study quantifies the CO₂ footprint of international immigrants and reveals their non-negligible impacts on global CO₂ emissions. Results show that the CO₂ footprint of international immigrants has increased from 1.8 gigatonnes (Gt) in 1995 to 2.9 Gt in 2015. In 2015, the U.S. had the largest total and per capita CO₂ emissions caused by international immigrants. Oceania and the Middle East are highlighted for their large portions of immigrant-caused CO₂ emissions in total CO₂ emissions (around 20%). Changes in the population and structure of global migration have kept increasing global CO₂ emissions during 1995-2015, while the reduction of CO₂ emission intensity helped offset global CO₂ emissions. The global CO₂ mitigation targets must consider the effects of global migration. Moreover, demand-side measures need to focus on major immigrant influx nations.

Quantifying Direct and Indirect Spatial Food-Energy-Water (FEW) Nexus in China

Food, energy, and water resources, which are interconnected with one another, are essential to human beings and sustainable development goals. Existing studies have quantified direct interconnections of food, energy, and water (FEW) systems in China but overlooked their indirect and spatial interconnections through production systems of other products. Quantifying both the direct and indirect spatial interconnections of food, energy, and water systems is the basis of holistic FEW resource management. The spatial interconnections of the FEW systems within China's economic supply chains at the provincial level were quantified from both demand-driven and supply-push perspectives in this study. Results show that food and energy subsystems have tighter coupling relations than the other relationships in the FEW nexus from the demand perspective, and food and water subsystems have tighter coupling relations from the supply perspective. Findings of this study highlight the necessity of demand-side and supply-side measures by identifying critical final consumers and primary suppliers. For example, primary inputs of energy extraction sectors in Inner Mongolia, Shanxi, and Heilongjiang are crucial for national water withdrawals. Sustainable management of FEW resources in China can be better achieved through strengthening the interdepartmental and interregional cooperation from both the demand and supply sides.

Great Divergence Exists in Chinese Provincial Trade-Related CO2 Emission Accounts

Accurate accounting of greenhouse gas (GHG) emissions considering interregional trade are important for developing regional-specific strategies for climate mitigation in countries like China where vast heterogeneity exists among regions. Trade-related provincial CO₂ emission accounts have been reported and analyzed for China using three independently developed multiregional input-output (MRIO) models which have been widely used. Here we show that significant divergence exists in both consumption-based and income-based CO₂ emission accounts for Chinese provinces in 2012 using different MRIO models. For example, the difference of CO₂ emissions for Shandong Province calculated from two MRIO models can reach 208Mt, more than the terrestrial emissions of Argentina, United Arab Emirates, or The Netherlands. Reducing such divergence, however, requires only the agreement among various MRIO models on a small number of critical data elements. Our results demonstrate the need of careful interpretation of previous studies on trade-related provincial GHG emission accounts in China, and prioritize future efforts to harmonize GHG emission accounting within China.

Describing the toxicity and sources and the remediation technologies for mercury-contaminated soil

Mercury (Hg) is a natural element and its compounds are found as inorganic and organic forms in the environment. The different Hg forms (e.g., methylmercury (MeHg)), are responsible for many adverse health effects, such as neurological and cardiovascular effects. The main source of Hg is from natural release. Nevertheless, with the development of industrialization and urbanization, Hg-contaminated soil mainly influenced by human activities (especially near mercury mining areas) has become a problem. Therefore, much more attention has been paid to the development and selection of various treatment methods to remediate Hg-contaminated soils. This paper presented a systematical review of the recent developments for the remediation of Hg-contaminated soils. Firstly, we briefly introduced the Hg chemistry, toxicity and the main human activity-related sources of mercury in soil. Then the advances in remediation technologies for removing Hg pollution from the soil were summarized. Usually, the remediation technology includes physical, chemical and biological remediation technology. Depending on this, we further classified these remediation technologies into six techniques, including thermal desorption, electrokinetic extraction, soil washing, chemical stabilization, phytoremediation and microbial technology. Finally, we also discussed the challenges and future perspectives of remediating Hg-contaminated soils.

Spatial-temporal characteristics and driving factors of the human health impacts of five industrial aquatic toxic metals in China

With the rapid advancement of industrialization without effective supervision, industrial aquatic toxic metal (TM) emissions pose threats to human health in China. Due to differences in socioeconomic development, the regional disparity of industrial aquatic TM emissions is obvious nationwide. In this study, the human health impacts (HHIs) of industrial aquatic TM emissions (i.e., mercury (Hg), cadmium (Cd), hexavalent chromium (Cr(VI)), lead (Pb), and arsenic (As)) in the 31 provinces of China were evaluated based on the ReCiPe method, and the driving factors affecting HHIs from 2000 to 2015 were decomposed using the logarithmic mean Divisia index (LMDI) method. The results showed that the HHIs gradually decreased, with more than an 80% decrease from 2000 to 2015. The order of the TMs contributing to the national HHIs in 2015 was as follows: As (79.5%) > Cr(VI) (19.6%) > Hg (0.4%) > Pb (0.2%) = Cd (0.2%), and 21 (68%) provinces were dominated by industrial aquatic As emissions. Economic development is the major driving factor of the increase in HHIs, while the HHI strength and wastewater discharge intensity are the key driving factors causing reductions in the HHIs. Hunan, Inner Mongolia, Hubei, and Jiangxi accounted for approximately 55% of the total HHIs in 2015. Some suggestions for reducing HHIs based on the local realities of different provinces were put proposed considering two aspects: economic strategy and technical capability.

Saving less in China facilitates global CO2 mitigation

Transforming China's economic growth pattern from investment-driven to consumption-driven can significantly change global CO₂ emissions. This study is the first to analyse the impacts of changes in China's saving rates on global CO₂ emissions both theoretically and empirically. Here, we show that the increase in the saving rates of Chinese regions has led to increments of global industrial CO₂ emissions by 189 million tonnes (Mt) during 2007-2012. A 15-percentage-point decrease in the saving rate of China can lower global CO₂ emissions by 186 Mt, or 0.7% of global industrial CO₂ emissions. Greener consumption in China can lead to a further 14% reduction in global industrial CO₂ emissions. In particular, decreasing the saving rate of Shandong has the most massive potential for global CO₂ reductions, while that of Inner Mongolia has adverse effects. Removing economic frictions to allow the production system to fit China's increased consumption can facilitate global CO₂ mitigation.

Chemical content and source apportionment of 36 heavy metal analysis and health risk assessment in aerosol of Beijing

The concentration levels of 36 airborne heavy metals and atmospheric radioactivity in total suspended particulate (TSP) samples were measured to investigate the chemical characteristics, potential sources of aerosols, and health risk in Beijing, China, from September 2016 to September 2017. The TSP concentrations varied from 6.93 to 469.18 μg/m³, with a median of 133.97 μg/m³. The order for the mean concentrations of heavy metals, known as hazardous air pollutants (HAPs), was as follows: Mn > Pb > As > Cr > Ni > Se > Cd > Co > Sb > Hg > Be; Non-Designated HAPs Metals: Ca > Fe > Mg > Al > K > Na > Zn > P > Ba > Ti > Cu > Sr > B > Sn > I > V > Rb > Ce > Mo > Cs > Th > Ag > U > Pt. The median concentration of As was higher than China air quality standard (6 ng/m³). The gross α and β concentration levels in aerosols were (1.84 ± 1.59) mBg/m³ and (1.15 ± 0.85) mBg/m³, respectively. The enrichment factor values of Cu, Ba, B, Ce, Tl, Cs, Pb, As, Cd, Sb, Hg, Fe, Zn, Sn, I, Mo, and Ag were higher than 10, which indicated enriched results from anthropogenic sources. Pb, As, and Cd are considered to originate from multiple sources; fireworks released Ba during China spring festival; Fe, Ce, and Cs may come from stable emissions such as industrial gases. The health risks from anthropogenic metals via inhalation, ingestion, and dermal pathway were estimated on the basis of health quotient as well as the results indicated that children faced the higher risk than adults during the research period. For adults, the health risk posed by heavy metals in atmospheric particles was below the acceptable level.

Impact of a Coal-Fired Power Plant Shutdown Campaign on Heavy Metal Emissions in China

Recently, China has committed to decommissioning the heavy metal (HM) intensive coal-fired power plants (CFPPs), small units especially, yet a quantitative assessment for the impact on HM emissions remains poorly understood. This study, for the first time, compiles a plant-specific inventory for six HMs (Hg, As, Se, Pb, Cd, and Cr) avoided by CFPPs decommissioned in China during the 12th Five Year Plan period. The reduced HM amounts to 271.58 t (9.19 t Hg, 45.84 t As, 60.76 t Se, 85.30 t Pb, 1.74 t Cd, and 68.75 t Cr), accounting for 12.71% of the total emissions from all China's CFPPs in 2010. Small units which have low boiler efficiency and lack air pollutant control devices are more than tenfold HM-intensive as the large units. The detailed HM emission factors for each CFPP decommissioned in each provincial region are also identified. HM content in the coal consumed is a key parameter to determine their corresponding emission factors, while the capacity of decommissioned coal plants plays a decisive role in the reduced emissions. The high-resolution inventory not only verifies China's progress in alleviating HM pollution, but also provides basis for further investigation into HM relevant environmental and human health impact.

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

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.

Fish consumption is considered to be the only significant dietary source of MeHg. Here the authors show that rice could also be a significant global dietary source, especially in South and Southeast Asia. International rice trade and joint ingestion of fish and rice could aggravate the MeHg exposure levels in many areas.