Mercury Exposure in Children of the Wanshan Mercury Mining Area, Guizhou, China

Economic benefit of ecological remediation of mercury pollution in southwest China 2007-2022

Methylmercury (MeHg) exposure via rice consumption poses health risk to residents in mercury contaminated areas, such as the Wanshan Hg mining area (WSMA) in southwest China. Making use of the published data for WSMA, this study developed a database of rice MeHg concentrations for different villages in this region for the years of 2007, 2012, 2017, and 2019. The temporal changes of human MeHg exposure, health effects, and economic benefits under different ecological remediation measures were then assessed. Results from this study revealed a decrease of 3.88 μg/kg in rice MeHg concentration and a corresponding reduction of 0.039 μg/kg/d in probable daily intake of MeHg in 2019 compared to 2007 on regional average in the WSMA. Ecological remediation measures in this region resulted in the accumulated economic benefits of $38.7 million during 2007-2022, of which 84 % was from pollution source treatment and 16 % from planting structure adjustment. However, a flooding event in 2016 led to an economic loss of $2.43 million (0.38 % of regional total Gross Domestic Product). Planting structure adjustment generates the greatest economic benefits in the short term, whereas pollution source treatment maximizes economic benefits in the long term and prevents the perturbations from flooding event. These findings demonstrate the importance of ecological remediation measures in Hg polluted areas and provide the foundation for risk assessment of human MeHg exposure via rice consumption.

Insights into the reduction of methylmercury accumulation in rice grains through biochar application: Hg transformation, isotope fractionation, and transcriptomic analysis

Methylmercury (MeHg), a potent neurotoxin, easily moves from the soil into rice plants and subsequently accumulates within the grains. Although biochar can reduce MeHg accumulation in rice grains, the precise mechanism underlying biochar-mediated responses to mercury (Hg) stress, specifically regarding MeHg accumulation in rice, remains poorly understood. In the current study, we employed a 4% biochar amendment to remediate Hg-contaminated paddy soil, elucidate the impacts of biochar on MeHg accumulation through a comprehensive analysis involving Hg isotopic fractionation and transcriptomic analyses. The results demonstrated that biochar effectively lowered the levels of MeHg in paddy soils by decreasing bioavailable Hg and microbial Hg methylation. Furthermore, biochar reduced the uptake and translocation of MeHg in rice plants, ultimately leading to a reduction MeHg accumulation in rice grains. During the process of total mercury (THg) uptake, biochar induced a more pronounced negative isotope fractionation magnitude, whereas the effect was less pronounced during the upward transport of THg. Conversely, biochar caused a more pronounced positive isotope fractionation magnitude during the upward transport of MeHg. Transcriptomics analyses revealed that biochar altered the expression levels of genes associated with the metabolism of cysteine, glutathione, and metallothionein, cell wall biogenesis, and transport, which possibly enhance the sequestration of MeHg in rice roots. These findings provide novel insights into the effects of biochar application on Hg transformation and transport, highlighting its role in mitigating MeHg accumulation in rice.

Home-produced eggs: An important pathway of methylmercury exposure for residents in mercury mining areas, southwest China

In light of the documented elevated concentrations of total mercury (Hg) and methylmercury (MeHg) in poultry originating from Hg-contaminated sites, a knowledge gap persists regarding the levels of Hg found in home-produced eggs (HPEs) and the associated dietary exposure risks in regions affected by Hg mining. To address this knowledge gap, a comprehensive investigation was undertaken with the primary objectives of ascertaining the concentrations of THg and MeHg in HPEs and evaluating the potential hazards associated with the consumption of eggs from the Wanshan Hg mining area in Southwest China. The results showed that THg concentrations in HPEs varied within a range of 10.5-809 ng/g (with a geometric mean (GM) of 64.1 ± 2.7 ng/g), whereas MeHg levels spanned from 1.3 to 291 ng/g (GM, 23.1 ± 3.4 ng/g). Remarkably, in half of all eggs, as well as those collected from regions significantly impacted by mining activities, THg concentrations exceeded the permissible maximum allowable value for fresh eggs (50 ng/g). Consumption of these eggs resulted in increased exposure risks associated with THg and MeHg, with GM values ranging from 0.024 to 0.17 µg/kg BW/day and 0.0089-0.066 µg/kg BW/day, respectively. Notably, the most substantial daily dosage was observed among children aged 2-3 years. The study found that consuming HPEs could result in a significant IQ reduction of 34.0 points for the whole mining area in a year. These findings highlight the potential exposure risk, particularly concerning MeHg, stemming from the consumption of local HPEs by residents in mining areas, thereby warranting serious consideration within the framework of Hg exposure risk assessment in mining locales.

Distribution, alkylation, and migration of mercury in soil discharged from the Itomuka mercury mine

The purpose of this study was to investigate the behavior of previously discharged mercury (Hg) released from the Itomuka Hg mine into the surrounding environment, especially into soil. Total-Hg (T-Hg), methylmercury (MeHg), and ethylmercury (EtHg) concentrations in the surface soil at eight sample sites around the mine were 3.8-64.2 mg/kg, 6.0-54.7 μg/kg, and undetected to 4.5 μg/kg, respectively. Core samples collected from seven of the eight sample sites showed that the vertical distribution of T-Hg was the highest in the surface soil layer and decreased rapidly in the lower layers. A strong positive correlation was observed between T-Hg and MeHg concentrations in the core samples; however, the slope of the regression line varied considerably for each core. This suggests that Hg and MeHg were not supplied from the atmosphere simultaneously, but rather that MeHg was produced on-site. Further, the formation of MeHg and EtHg in soil was considered in terms of the total organic carbon/total nitrogen ratio, which is a decomposition index of soil organic matter. The strong positive correlation between T-Hg and MeHg can be attributed to the migration of organic matter containing Hg species to the lower layers. There was no relationship between T-Hg and MeHg at the riverbed sample site because of the high T-Hg in the lower soil layers, suggesting that Hg was supplied by ore at this sample site. These assumptions of the formation change and migration of Hg in soil were supported by the results of the fractionation experiment and the elution test. To understand the current conditions in this area, measurements of Hg in the water, sediment, atmosphere, and plants were also conducted.

Holistic health risk assessment in an artisanal mercury mining region in Mexico

Mexico is one of the world's leading mercury producers and exporters. However, mercury mining is carried out using artisanal procedures, which highly impact ecosystems. In the municipality of Pinal de Amoles, Queretaro, Mexico, artisanal mercury mining (AMM) is practiced in a region that has been categorized as a Biosphere Reserve. Therefore, a holistic health risk assessment for mercury was performed in the region, including environmental monitoring (air, water, and soil) and mercury exposure in both humans (children, women, and miners) and biota (plants, rodents, and worms). The atmospheric mercury determination was carried out using the JEROME® J405 analyzer, whereas total mercury in environmental and biological samples was determined by atomic absorption spectrophotometry/cold vapor. Results showed that mercury concentrations in the environmental and biological matrices exceeded their respective reference values. These results demonstrate the direct influence of AMM in the increasing levels of mercury in all the components of the studied ecosystem. Therefore, comprehensive intervention strategies must be implemented to reduce and prevent human health and ecological risks due to the presence of mercury. In this regard, the Minamata Convention for mercury control should include biomonitoring programs not only for humans but also for critical ecological receptors in polluted ecosystems.

Neurodevelopment and exposure to neurotoxic metal(loid)s in environments polluted by mining, metal scrapping and smelters, and e-waste recycling in low and middle-income countries

This review covers a wide body of literature to gain an understanding of the impacts of informal activities related to metal extraction (primary mining and recycling) on early life exposure to neurotoxicants and on neurodevelopment. In primary mining, gold extraction with Hg amalgamation is the main environmental cause of Hg pollution in most artisanal small-scale gold mining (ASGM) activities around the world. Nevertheless, in Sub-Saharan Africa (SSA), Pb disrupted from gold-related ores, mining, and artisanal cookware production are an important neurotoxicant that seriously contaminates the affected population, with devastating effects on children. In e-waste recycling settings, the range of neurotoxic substances that contaminate mothers and children is wider than in primary mining environments. Thus, Hg and Pb are major pre- and postnatal neurotoxicants affecting children in the informal metal extraction activities and SSA countries show the highest record of human contamination and of neurotoxic effects on children. There are additional sources of neurotoxic contamination from mining and metal processing activities (cyanide tailing in South America and SSA) and/or co-exposure to Hg-containing products such as cosmetics (soaps and Hg-based skin lightning creams in Africa) and pediatric Thimerosal-containing vaccines (TCVs, that breaks down to ethyl-mercury) in current use in middle and low income countries. However, the action of these neurotoxicants (per se or in combination) on children needs more attention and research. Studies show a negative association between biomarkers of all environmental metal(loid)s (As, Cd, Hg, Mn, and Pb) studied and neurodevelopment in young children. Sadly, in many unregulated activities, child labor is widely employed, thus presenting an additional occupational exposure. Children living in polluted environments related to metal processing are disproportionately exposed to a wide range of co-occurring neurotoxic substances. The review showed compelling evidence from highly representative parts of the world (Africa, Asia, and Latin America) that the studied neurotoxic substances negatively affected areas of the brain associated with language, memory and executive function, as well as psychosocial behavior. Protecting the environment and children from unregulated and highly polluting metal extraction and processing are inextricably intertwined and deserve urgent attention.

Monthly variations in mercury exposure of school children and adults in an industrial area of southwestern China

Recent studies have shown that rice consumption can be the major pathway for human methylmercury (MeHg) exposure in inland China. However, few studies have considered the susceptible population of school children's exposure through rice ingestion. In this study, monthly variations in total Hg (THg)/MeHg concentrations in rice, fish, hair, and urine samples were studied to evaluate the Hg (both THg and MeHg) exposure in Guiyang, a typical industrial area with high anthropogenic emission of Hg. A total of 17 primary school (school A) students, 29 middle school (school B) students, and 46 guardians participated in this study for one year. Hair THg, hair MeHg, and urine THg concentrations ranged from 355-413 ng g^-1, 213-236 ng g^-1, and 469-518 ng g^-1 Creatinine (ng·g^-1 Cr), respectively, and no significant differences were observed between different genders and age groups. Hair and urine Hg concentrations showed slightly higher values in the cold season (October to February) than the hot season (March to September), but without significant difference. High monthly variability of individual hair and urine Hg concentrations suggested that long-term study could effectively decrease the uncertainty. The school students showed significantly higher urine THg concentrations than adults due to children's unique physiological structure and behaviors. Probable daily intake (PDI) of MeHg via rice and fish ingestion averaged at 0.0091, 0.0090, and 0.0079 μg kg^-1 d^-1 for school A students, school B students, and their guardians, respectively, which means that 86%, 84%, and 87% of the PDI were originated from rice ingestion, respectively. Therefore, more attention should be paid to children as a susceptible population. The results indicated low risk of Hg exposure via rice and fish consumption for urban residents in a Chinese industrial city.

Use of mercury isotopes to quantify sources of human inorganic mercury exposure and metabolic processes in the human body

The pathways of human mercury (Hg) exposure are complex and accurate understanding of relative contributions from different pathways are crucial for risk assessment and risk control. In this study, we determined total Hg concentration and Hg isotopic composition of human urine, dietary components, and inhaled air in the Wanshan Hg mining area (MA), Guiyang urban area (UA), and Changshun background area (BA) to understand Hg exposure sources and metabolic processes in human body. At the three studied sites, total gaseous mercury (TGM) showed negative δ²⁰²Hg (-3.11‰ to + 1.12‰) and near-zero Δ¹⁹⁹Hg (-0.16‰ to + 0.13‰), which were isotopically distinguishable from Hg isotope values of urine (δ²⁰²Hg: -4.02‰ to - 0.84‰; Δ¹⁹⁹Hg: -0.14‰ to 0.64‰). We observed an offset of -1.01‰ to -1.6‰ in δ²⁰²Hg between TGM and urine samples, and an offset of -1.01‰ to 0.80‰ in δ²⁰²Hg between rice and urine samples, suggesting that lighter isotopes are more easily accumulated in the kidneys and excreted by urine. We proposed that the high positive Δ¹⁹⁹Hg in urine samples of UA was derived from fish consumption. The results of a binary mixing model based on Δ¹⁹⁹Hg were compared with those from a classic dietary model. The results from the MIF binary model showed that fish consumption accounted for 22% of urine Hg in the families at UA, whereas fish consumption contributed limited Hg to MA and BA. This study highlighted that Hg isotopes can be a useful tracer in understanding the sources and fates of Hg in human bodies.

Multi-pathway mercury health risk assessment, categorization and prioritization in an abandoned mercury mining area: A pilot study for implementation of the Minamata Convention

This is a systematic study of human health risk assessment (HHRA) and risk categorization for inorganic mercury (IHg) and methylmercury (MeHg) in Hg mining areas. A multi-pathway exposure model coupled with Monte Carlo simulation was constructed for the Wanshan Hg mining area (WSMM), Southwestern China, with consideration of oral ingestion (foodstuffs, water and soil), dermal contact (water and soil), and inhalation (gaseous Hg and particulate Hg). The results show that dietary intake (food and water), gaseous Hg inhalation, oral ingestion of soil particles, dermal contact, and particulate Hg inhalation comprised 88.3-96.3%, 3.49-6.14%, 0.14-5.3%, 0.02%, and <0.01% of total IHg ingestion, respectively. As expected, rice consumption contributed the highest proportion (86.3-92.7%) of MeHg. The study shows that the elevated MeHg exposure risk is the most significant issue in Hg mining areas. In addition, Hg risk categorization and prioritization in the WSMM are established for the first time based on rice-based exposure doses of IHg and MeHg. Target areas for future treatment and/or remediation are characterized according to thresholds of reference dose and provisional tolerable weekly intake for exposure doses, as well as risk screening values and risk control values for contaminated soil. The proposed multi-pathway exposure model is strongly recommended for the HHRA of Hg-contaminated sites worldwide and helps facilitate the implementation of the Minamata Convention on Mercury.

Isotopic Fractionation and Source Appointment of Methylmercury and Inorganic Mercury in a Paddy Ecosystem

Bioaccumulation of methylmercury (MeHg) in rice grains has been an emerging issue of human health, but the mechanism of bioaccumulation is still poorly understood. Mercury (Hg) isotope measurements are powerful tools for tracing the sources and biogeochemical cycles of Hg in the environment. In this study, MeHg compound-specific stable isotope analysis (CSIA) was developed in paddy soil and rice plants to trace the biogeochemical cycle of Hg in a paddy ecosystem during the whole rice-growing season. Isotopic fractionation was analyzed separately for MeHg and inorganic Hg (IHg). Results showed distinct isotopic signals between MeHg and IHg in rice plants, indicating different sources. δ²⁰²Hg values of MeHg showed no significant differences between roots, stalks, leaves, and grains at each growth stage. The similar Δ¹⁹⁹Hg values of MeHg between rice tissues (0.14 ± 0.08‰, 2SD, n = 12), soil (0.13 ± 0.03‰, 2SD, n = 4), and irrigation water (0.17 ± 0.09‰, 2SD, n = 5) suggested that the soil-water system was the original source of MeHg in rice plants. Δ¹⁹⁹Hg values of IHg in the paddy ecosystem indicated that water, soil, and atmosphere contributed to IHg in grains, leaves, stalks, and roots with varying degree. This study demonstrates that successful application of MeHg CSIA can improve our understanding of the sources and bioaccumulation mechanisms of MeHg and IHg in the paddy ecosystems.

Impact of low-level mercury exposure on intelligence quotient in children via rice consumption

Wanshan is a city in southwest China that has several inactive mercury (Hg) mines. The local population are exposed to methylmercury (MeHg) due to the consumption of Hg contaminated rice. The relationship between Hg exposure and the cognitive functions of local children is unknown. This study investigated the relationship between hair Hg concentrations and the intelligence quotient (IQ) of 314 children aged 8-10 years, recruited from three local primary schools in Wanshan area in 2018 and 2019. IQ was evaluated using Wechsler Intelligence Scale for Children - Fourth Edition (WISC-IV). The average THg concentration in children's hair samples was 1.53 μg g^-1 (range: 0.21-12.6 μg g^-1), and 65.6% exceeded the United States Environment Protection Agency (USEPA) recommended value of 1 μg g^-1. Results of logistic regression analysis showed that children with hair Hg ≥ 1 μg g^-1 were 1.58 times more likely to have an IQ score <80, which is the clinical cut-off for borderline intellectual disability (R² = 0.20, p = 0.03). Increasing of 1 μg g^-1 hair Hg resulted in 1 point of IQ loss in Wanshan children, which was.much higher than that via fish consumption. The economical cost due to Hg exposure was estimated to be $69.8 million (9.43% of total GDP) in the Wanshan area in 2018.

Macrobrachium amazonicum (Crustacea, Decapoda) Used to Biomonitor Mercury Contamination in Rivers

Open-air landfill's may be are considered as a potential source of human environmental exposure to chemical substances such as, polycyclic aromatic hydrocarbons and toxic metals. Due to possible availability of mercury in the environment caused by open landfill emissions, this study evaluates the spatiality and seasonality of macroinvertebrates, in particular shrimps (Macrobrachium amazonicum), exposure to mercury (Hg). Information regarding Hg accumulation in this crustacean may be important for the development of public policies aiming conservation and preservation of ecosystems surrounding landfills in Amazon, and around the world. Sampling occurred quarterly in the following months: November/2015; February/2016; May/2016 and; August/2016. In each of these months, three points were selected: P1, P2 and P3. The samples were processed via acid digestion and the quantification of metal was performed by inductively coupled plasma mass spectrometry. The average concentration of total mercury (T-Hg) was 24.565 ± 6.610 µg kg^-1 wet weight, with minimum and maximum limits of 12.742 ± 11.367 (P3) and 35.509 ± 14.761 µg kg^-1 wet weight (P1) in November/2015 and August/2016, respectively. The concentration of total mercury (T-Hg) in shrimps was different between points (p = 0.004) and months (p = 0.000). The T-Hg concentrations were significantly higher in May and August 2016, which corresponds to the dry season. The presence of landfills promotes large accumulation of T-Hg in the aquatic biota and represents a risk to human health. However, seasonal changes in T-Hg levels were observed. In the wettest period, bioconcentration factor levels decrease in aquatic organisms.

Optimization of pretreatment procedure for MeHg determination in sediments and its applications

Methylmercury (MeHg) in sediment is difficult to be determined due to its low concentration and binding compounds like sulfide and organic matter. Moreover, wet sediment samples have been suggested to behave differently from certified reference materials in MeHg analysis. Optimal pretreatment procedure for MeHg determination in sediments has not been ascertained and whether the procedure could apply to sediment samples with complex matrix merits further research. This work firstly compared recovery results of five pretreatment procedures for MeHg determination using ERM-CC580. Using the optimal pretreatment procedure, recovery results were analyzed in different sediment samples after manipulation of moisture content, organic matter, and acid volatile sulfide. The procedure using CuSO₄/HNO₃ as leaching solutions and mechanical shaking as extraction method was proved to produce the most satisfactory recovery results (100.67 ± 6.75%, mean ± standard deviation). And when moisture content varied from 20 to 80%, average recovery results in sediment samples ranged from 100 to 125%. Furthermore, before and after the manipulation of organic matter or acid volatile sulfide, spiking recovery results varied little and were all within acceptable limit (85~105%). Therefore, the procedure of CuSO₄/HNO₃-mechanical is proposed as a universal pretreatment method for MeHg determination in sediment samples with various characteristics.

Health risks to local residents from the exposure of heavy metals around the largest copper smelter in China

Non-ferrous smelting releases lots of heavy metals to the environment. Although numerous studies have focused on pollution in the environment, fewer have studied the adverse health effects. In the current study, samples of food, hair and urine were collected and analyzed for zinc (Zn), iron (Fe), chromium (Cr), nickel (Ni), lead (Pb) and copper (Cu) from residents of 3 villages near the largest copper smelter in China. The estimated daily intake (EDI), target hazard quotient (THQ), and Hazard Index (HI) were used to estimate and analyze the health risks to local residents (children, adults, and seniors). The Zn, Cr, Ni, Fe, Pb and Cu concentrations in food ranged from 16.02 to 61.48 mg kg^-1, 0.23-13.64 mg kg^-1, 0.10-5.90 mg kg^-1, 19.16-170.05 mg kg^-1, 0.15-3.62 mg kg^-1, and 0.53-2.74 mg kg^-1, respectively. Zn, Cr, Ni and Pb concentrations in all vegetables were above the national tolerance limits. Children had higher EDIs of heavy metals than that of adults and seniors. The THQ of single elements and the HI of combined elements indicated that the EDI of Pb and Cu showed the highest potential health risks, followed by the EDI of Zn and Fe, and Ni, Cr. High EDI of heavy metals resulted in much higher concentrations of heavy metals in hair and urine samples than those of normal Chinese residents, showing that residents around the smelter have potential health risks through daily food intake. The main sources of these heavy metals were from the consumption of rice and vegetables and it is imperative that measures should be taken to control this urgent problem.

Mercury pollution in modern times and its socio-medical consequences

Mercury plays a critical role in serious health problems due to environmental or occupational exposures. Aquatic ecosystems are an essential component of the global biogeochemical cycle of mercury, as inorganic mercury can be converted to toxic methyl mercury in these environments and reemissions of elemental mercury rival anthropogenic mercury releases on a global scale. The history of the Minamata disease, a typical example of industrial pollution, has shown how corporate secrecy and ignorance on part of the health authorities may influence the devastating spread of environmental contamination and the progress of disease. While the Minamata Convention, in place since 2017, is aiming to lower mercury exposure and to prevent adverse effects, there are still knowledge gaps in the areas of global environmental mercury exposure. Areas of uncertainty in the global biogeochemical cycle of mercury include oxidation processes in the atmosphere, land-atmosphere and ocean-atmosphere cycling, and methylation processes in the ocean. Pollution related to climate change (especially in boreal and arctic regions), bioaccumulation and biomagnification of methyl mercury in the food chain, especially in fish and marine mammals, needs to be addressed in more detail. Information is lacking on numerous hidden contaminant exposures i.e. from globally applied traditional medicine, mercury containing skin creams and soaps, dental amalgam, ethyl mercury containing vaccines and latex paint additives, as well as on mercury releases from power plants, e-waste/fluorescent lamps, wildfire emissions, and global artisanal small-scale gold mining activities. Mercury occurs in various forms with different levels of toxicity. While much is already known and documented on the health effects of mercury, present knowledge and translation into preventive actions is still incomplete. Risks for long term health effects trough prolonged low dose exposure and trough cumulative exposures of various mercury forms should be further addressed. Preventive actions should include adequate human biomonitoring programs. Research data should be translated swiftly into management tools for local policy makers and health professionals, also paying attention at the major differences in mercury contamination across the globe.

Exposure risk of local residents to copper near the largest flash copper smelter in China

Copper (Cu) smelting released large amounts of Cu and contaminated the environment. However, few studies have investigated the Cu exposure risks for people located near Cu smelters. In this study, atmospheric bulk deposition, food from local families, drinking water and biological samples (hair and urine) were collected in three villages near the largest flash Cu smelter in China. The objective of the current study was to investigate how non-ferrous metals smelting affect the human health. Total atmospheric Cu depositions (56-767μgm^-2yr^-1) were one or two orders of magnitude greater than that of unpolluted rural areas. The Cu concentrations in locally grown vegetables and dietary chronic daily intake (CDI) of local residents showed a consistently decreasing trend with atmospheric Cu depositions. Dietary intake of vegetables and rice were the two major pathways of total CDI, which accounted for >93% totally. The Cu exposure showed higher potential non-carcinogenic risk to human health of local residents, especially children living around the Cu smelter through food consumptions. Health impact monitoring data revealed that mean Cu concentrations in hair and urine samples were ranged from 5.13 to 28.85mgkg^-1 and 19.90 to 54.61μgL^-1 in the three villages, respectively. Significant correlation between hair Cu concentrations and the CDI of Cu indicated food ingestion had adverse effects on the health of the local residents. The result suggested that nonferrous metal smelter should be away from residential area and locally produced crops became unsuitable for consumption. Therefore, effective measures on Cu pollution management and control in the surrounding area should be formulated and implemented.

Selenium status of children in Kashin-Beck disease endemic areas in Shaanxi, China: assessment with mercury

The causes of Kashin-Beck disease (KBD) in children are multifactorial, and particular consideration has been given to childhood selenium (Se) deficiency. In this study, dietary intake of Se and mercury (Hg) was determined at KBD areas to investigate the Se status and risks. Therefore, total Hg and Se levels were investigated in scalp hair samples and in daily intake food samples of 150 schoolchildren in Yongshou County of Shaanxi, China. The results showed that the average concentration of Se in children's hair has risen to 302 ng g^-1 and significantly increased compared to the data reported decades ago. Children at KBD endemic areas likely have improved Se status due to the Se supplementation in food at recent decades. However, all the children in the study areas still showed lower Se status compared to those in other non-KBD areas of China. The probable daily intake of Se in the study areas was still lower after stopping Se supplementation in food at KBD areas, which is 17.96 μg day^-1. Food produced locally cannot satisfy the lowest demand for Se nutrition for local residents. If the interactions of Se-Hg detoxification are considered, Hg intake from food exacerbates Se deficiency at the KBD areas.

Combined Amendments of Nano-hydroxyapatite Immobilized Cadmium in Contaminated Soil-Potato (Solanum tuberosum L.) System

The toxicity of cadmium (Cd) has posed major public health concern in crops grown in the Cd-contaminated soils. The effects of five amendments, nano-hydroxyapatite (n-HA) and it combined with lime, zeolite, bone mill and fly ash on Cd immobilization in soils and uptake in potatoes, were investigated in a contaminated soil by pot experiments. The result showed that the applications of combined amendments significantly decreased the bioavailable Cd concentrations extracted by TCLP, DTPA-TEA and MgCl₂ in the contaminated soils, and changed the soluble and exchangeable and specifically sorbed fractions to oxide-bound and organic-bound fractions. Compared to the control group, the concentrations of Cd in the potato tubers grown in n-HA, n-HA + Fly ash, n-HA + Lime, n-HA + Bone mill and n-HA + Zeolite soil were reduced 17.4%, 20.7%, 15.2%, 32.6% and 39.1%, respectively. Nano-hydroxyapatite combined amendments was more effective in reducing bioavailable Cd concentrations and Cd accumulations in potatoes, especially for n-HA + Z.

Mercury pollution by gold mining in a global biodiversity hotspot, the Choco biogeographic region, Colombia

Mercury (Hg) is a harmful pollutant released into the environment from gold mining activities, representing a risk to human health and the ecosystems. The aim of this study was to assess the levels of total Hg (T-Hg) in human hair, fish, sediments and air; and to determine fish consumption-based risks for T-Hg ingestion in the Choco biogeographic region, a global biodiversity hotspot located at the Colombian Pacific. Mercury concentrations in hair were measured in two locations, Quibdo, the state capital, and Paimado, a riverine community. The median T-Hg value in human hair in Quibdo was 1.26 μg/g (range: 0.02-116.40 μg/g), whereas in Paimado it was 0.67 μg/g (range: 0.07-6.47 μg/g). Mercury levels in examined locations were weakly associated with height (ρ = 0.145, P = 0.024). Air T-Hg levels in Quibdo were high inside gold shops being up to 200.9-fold greater than the background. Mercury concentrations in fish from Atrato River were above WHO limit (0.5 μg/g), with highest levels in Pseudopimelodus schultzi, Ageneiosus pardalis, Sternopygus aequilabiatus, Rhamdia quelen and Hoplias malabaricus, whereas the lowest appeared in Cyphocharax magdalenae and Hemiancistrus wilsoni. Based on fish consumption, these last two species offer low risk to human health. Sediment samples from fifty different sites of Atrato River showed low T-Hg concentrations, with little variability between stations. However, contamination factors revealed a moderate pollution in 44% of sampling sites along the river. In conclusion, Hg pollution is widespread in the Biogeographic Choco and governmental actions must be taken to protect the population and preserve its biodiversity.

Mercury Hair Concentration among Primary School Children in Malaysia

The main concern regarding mercury exposure is the adverse health effect on the developing nervous system. The objective of this cross-sectional study was to determine hair mercury levels and their association with socio-demographic characteristics, complaints about mercury poisoning symptoms and the fish consumption pattern among children in Malaysia. A cross-sectional study was conducted among 215 school children aged 11 years old. Hair was collected from the children and the total mercury was analyzed using oxygen combustion–gold amalgamation atomic absorption spectrophotometry. Anthropometric data, a fish consumption questionnaire and mercury poisoning symptoms were collected during a personal interview. The mean hair mercury level among primary school children was 0.63 ± 0.59 µg/g with the geometric mean of 0.47 µg/g. A total of 14% of respondents had hair mercury levels above 1 µg/g. A multiple binary logistic regression analysis outlined that fish consumption of at least one meal per week increased the likelihood of having a high mercury level (odds ratio (OR) 3.7, 95% confidence interval (CI) 1.3–10.4). This study confirms the existence of a mercury burden among Malaysian children and the level is high compared to other regional studies. This study provides important baseline data regarding the mercury level among children in Malaysia.