Peptides Used for Heavy Metal Remediation: A Promising Approach.

In recent years, heavy metal pollution has become increasingly prominent, severely damaging ecosystems and biodiversity, and posing a serious threat to human health. However, the results of current methods for heavy metal restoration are not satisfactory, so it is urgent to find a new and effective method. Peptides are the units that make up proteins, with small molecular weights and strong biological activities. They can effectively repair proteins by forming complexes, reducing heavy metal ions, activating the plant's antioxidant defense system, and promoting the growth and metabolism of microorganisms. Peptides show great potential for the remediation of heavy metal contamination due to their special structure and properties. This paper reviews the research progress in recent years on the use of peptides to remediate heavy metal pollution, describes the mechanisms and applications of remediation, and provides references for the remediation of heavy metal pollution.

Soil Microplastic Pollution and Microbial Breeding Techniques for Green Degradation: A Review.

Microplastics (MPs), found in many places around the world, are thought to be more detrimental than other forms of plastics. At present, physical, chemical, and biological methods are being used to break down MPs. Compared with physical and chemical methods, biodegradation methods have been extensively studied by scholars because of their advantages of greenness and sustainability. There have been numerous reports in recent years summarizing the microorganisms capable of degrading MPs. However, there is a noticeable absence of a systematic summary on the technology for breeding strains that can degrade MPs. This paper summarizes the strain-breeding technology of MP-degrading strains for the first time in a systematic way, which provides a new idea for the breeding of efficient MP-degrading strains. Meanwhile, potential techniques for breeding bacteria that can degrade MPs are proposed, providing a new direction for selecting and breeding MP-degrading bacteria in the future. In addition, this paper reviews the sources and pollution status of soil MPs, discusses the current challenges related to the biodegradation of MPs, and emphasizes the safety of MP biodegradation.

Predictive modeling of methylmercury in rice (Oryza sativa L.) and species-sensitivity-distribution-based derivation of the threshold of soil mercury in karst mountain areas.

The bioavailable mercury (Hg) in the soil is highly active and can affect the formulation of methyl-Hg (MeHg) in soil and its accumulation in rice. Herein, we predicted the concentration of MeHg in rice using bioavailable Hg extracted from soils; additionally, we determined the threshold value of soil Hg in karst mountain areas based on species sensitivity distribution. The bioavailable Hg was extracted using calcium chloride, hydrochloric acid (HCl), diethylenetriaminepentaacetic acid mixture, ammonium acetate, and thioglycolic acid. Results showed that HCl is the best extractant, and the prediction model demonstrated good predictability of the MeHg concentration in rice based on the HCl-extractable Hg, pH, and soil organic matter (SOM) data. Compared with the actual MeHg concentration in rice, approximately 99% of the predicted values (n = 103) were within the 95% prediction range, indicating the good performance of the rice MeHg prediction model based on soil pH, SOM, and bioavailable Hg in karst mountain areas. Based on this MeHg prediction model, the safety threshold of soil Hg was calculated to be 0.0936 mg/kg, which is much lower than the soil pollution risk screening value of agricultural land (0.5 mg/kg), suggesting that a stricter standard should be applied regarding soil Hg in karst mountain areas. This study presents the threshold of soil Hg pollution for rice safety in karst mountain areas, and future studies should target this threshold range.

Human Dietary Exposure to Heavy Metals via Rice in Nepal.

The effects of exposure to heavy metals (HMs) in rice on human health have become a global public health concern, particularly in countries where rice is consumed as a staple food. The concentrations of HMs, including cadmium (Cd), arsenic (As), lead (Pb), and copper (Cu), in commercial rice samples (n = 170) were analyzed to estimate the HM exposure of consumers in Nepal. The geometric mean concentrations of Cd, As, Pb, and Cu in commercial rice were 15.5 ± 16.0, 43.4 ± 19.6, 16.0 ± 14.0, and 1066 ± 1210 µg/kg, respectively, all below the maximum allowable concentrations (MACs) recommended by FAO/WHO. Generally, the average estimated daily intakes (EDIs) of Cd, As, Pb, and Cu were all below the oral reference doses (RfDs). However, young age groups were exposed to high levels of HMs, and the average EDI of As and the P99.9 EDIs of Cu and Cd were above the corresponding RfDs. The mean hazard index and total carcinogenic risk were 1.13 and 1.04 × 10-3 respectively, suggesting a potential non-carcinogenic risk (NCR) and a carcinogenic risk (CR) via rice consumption. Arsenic contributed the most strongly to NCR and Cd to CR. Overall, although the HM levels in rice were generally safe, the Nepalese population may be exposed to an elevated health risk from rice consumption.

Integrated Insights into Source Apportionment and Source-Specific Health Risks of Potential Pollutants in Urban Park Soils on the Karst Plateau, SW China.

Polycyclic aromatic hydrocarbons (PAHs) and heavy metal(loid)s (HMs) pose risks to environmental and human health. Identification of priority control contaminants is important in guiding the management and control of these synchronous pollutants. A total of 247 soil samples were collected from 64 urban parks in the karst plateau city of Guiyang in SW China to determine the concentrations, spatial distributions, and health risks of PAHs and HMs. The results indicate that dibenz(ah)anthracene and benzo(a)pyrene are the main PAHs species of high ecological risk, and Cr, Mn, and Ni pose elevated ecological risk among the HMs. Four sources were identified for PAHs (biomass burning, coke oven, traffic sources, and coal burning) and HMs (traffic sources, coal burning, industrial sources, and natural sources). The non-carcinogenic risk (NCR) and total carcinogenic risk (TCR) of PAHs were all determined to be negligible and at acceptable levels, several orders of magnitude below those of HMs. The NCR and TCR values of HMs were relatively high, especially for children (11.9% of NCR > 1; 79.1% of TCR > 10-4). Coal burning and natural sources make the greatest contributions to the NCR and TCR values from karst park soils in Guiyang. Considering HMs bioavailability, NCR and TCR values were rather low, due to the high residual HM fractions. Integrated insights into source specific ecological and human health risk indicate future directions for management and control of synchronous PAH and HM pollution, particularly for karst plateau areas. Supplementary Information: The online version contains supplementary material available at 10.1007/s12403-023-00534-3.

The range and habitat suitability of François' langur (Trachypithecus francoisi) in Mayanghe Nature Reserve, China.

The François' langur (Trachypithecus francoisi) is an endangered primate living in limestone forests in Vietnam and China. From October 2017 to August 2018, the habitat preferences and the range of the Francois' langur were surveyed in the Mayanghe Nature Reserve, Guizhou, People's Republic of China. To estimate the range and predict suitable habitat of François' langur, a Gaussian normal kernel density estimation and species distribution models (BIOMOD2) were used along with data on environmental variables and records of the langur's occurrence. The total range of François' langur in the reserve is 68.76 km2, accounting for 22.1% of the total area of the reserve. The elevation of the main utilisation area is 500-800 m, accounting for 48.53% of the total area of the reserve. The maximum slope utilised is 20°-30°, 30.19 km2 and accounting for 30.56% of the total area. The habitat used is largely distributed along valleys, preferred broad leaf forest, lower elevation, and close to rivers. Broad leaf forest is the main habitat type utilised, totalling 25.57 km2 and accounting for 37.19% of the total area. Our models predicted that the suitable habitat in the reserve is 62.46 km2, accounting for 20.08% of the total reserve area, with 32.93-km2 suitable habitat occurring in the core zone, 22.44 km2 in the buffer zone, and 7.02 km2 in the experimental zone. Our results indicate that only limited suitable habitat (51%) adverse reserve zoning exists in the Mayanghe Nature Reserve of François' langur.

Prediction model of delayed graft function based on clinical characteristics combined with serum IL-2 levels.

BACKGROUND: Kidney transplantation is an effective treatment for end-stage renal disease (ESRD). Delayed graft function (DGF) is a common complication after kidney transplantation and exerts substantial effects on graft function and long-term graft survival. Therefore, the construction of an effective model to predict the occurrence of DGF is particularly important. METHODS: Seventy-one patients receiving their first kidney transplant at the First Affiliated Hospital of Nanchang University from October 2020 to October 2021 were enrolled in the discovery cohort. Based on clinical characteristics and serum markers, a logistic regression model was used to simulate the risk of DGF in the discovery cohort. The DGF prediction model was named the prediction system and was composed of risk factors related to DGF. Thirty-two patients receiving a kidney transplant at the First Affiliated Hospital of Nanchang University from October 2021 to February 2022 were enrolled in the validation cohort. The validation cohort was used to verify the accuracy and reliability of the prediction model. RESULTS: Cold ischemia time (CIT), donor history of diabetes mellitus, donor interleukin-2 (IL-2) level and donor terminal creatinine level constitute the prediction system. In the validation test, the area under the receiver operating characteristic curve (AUC) was 0.867 for the prediction system, and good calibration of the model was confirmed in the validation cohort. CONCLUSIONS: This study constructed a reliable and highly accurate prediction model that provides a practical tool for predicting DGF. Additionally, IL-2 participates in the kidney injury process and may be a potential marker of kidney injury.

Occurrence of total mercury and methylmercury in rice: Exposure and health implications in Nepal.

Emerging studies have indicated that the consumption of rice could be the major methylmercury (MeHg) contributor to human mercury (Hg) exposure. Nonetheless, few studies are available on Hg in rice around the world, especially in countries with heavy rice diet. In this study, total Hg (THg) and MeHg levels in rice samples (n = 172) across Nepal were first investigated. The geometric mean THg was 7.05 ± 7.71 µg/kg with a range of 0.622 µg/kg to 158 µg/kg, and the maximum THg level was up to 791% of the Chinese National Standard Limit for THg in rice (20 µg/kg). The geometric mean MeHg was 0.820 ± 0.660 µg/kg with a range of 0.189 µg/kg to 8.59 µg/kg. Overall, the mean MeHg exposure (0.00445 ± 0.00477 µg/kg bw/day) and inorganic Hg (IHg) exposure (0.0360 ± 0.0739 µg/kg bw/day) were lower than the reference dose (RfD) of 0.1 µg/kg bw/day for MeHg and the provisional tolerable weekly intake (PTWI) of 0.571 µg/kg bw/day for IHg, respectively. Concerning different groups of vulnerable populations, the highest MeHg exposure (0.126 µg/kg bw/day) and IHg exposure (1.57 µg/kg bw/day) of preschoolers (37-50 months old) were approximately 126% of the RfD for MeHg and 275% of the PTWI for IHg. When the pregnant mothers eat the rice without awareness of the Hg content in rice, the mean and highest intelligence quotients (IQs) losses were 9554 and 118659 points, respectively, and the corresponding economic costs due to IQ loss could be 15.1 million USD and 188 million USD in Nepal. The results of rice THg and MeHg levels and corresponding exposure in populations highlighted the occurrence of rice THg and MeHg pollution issues in Nepal. More efforts should be made to protect younger groups in Nepal from high rice Hg exposure. CAPSULE: Owing to the high rice consumption rates relative to body mass, preschoolers (37-50 months) may meet the 126% reference dose (0.1 µg/kg bw/day) for MeHg and 275% provisional tolerable weekly intake (0.571 µg/kg bw/day) for IHg exposure in Nepal.

Distributions of Total Mercury and Methylmercury in Dragonflies from a Large, Abandoned Mercury Mining Region in China.

Dragonflies (Order Odonata) often are considered to be biosentinels of environmental contamination, e.g., heavy metals and/or persistent organic pollutants (POPs). Dragonflies (n = 439) belonging to 15 species of 8 genera were collected from an abandoned mercury (Hg) mining region in China to investigate the bioaccumulation of total Hg (THg) and methylmercury (MeHg). THg and MeHg concentrations in dragonflies varied widely within ranges of 0.06-19 mg/kg (average: 1.5 ± 2.2 mg/kg) and 0.02-5.7 mg/kg (average: 0.75 ± 0.65 mg/kg), respectively. THg and MeHg were positively correlated with bodyweight (THg: r2 = 0.10, P = 0.000; MeHg: r2 = 0.09, P = 0.000). Significant variations were observed among species, with the highest MeHg value (in Orthetrum triangulare) was fivefold higher than the lowest (in Pantala flavescens). These variations were consistent with those of nitrogen isotope (δ15N) values, indicating that increased δ15N, i.e., trophic levels, may reflect increased exposure and uptake of biomagnifying MeHg in dragonflies. A toxicological risk assessment found hazard quotients for specialist dragonfly-consuming birds of up to 7.2, which is 2.4 times greater than the permissible limit of 3, suggesting a potential toxicological risk of exposure.

Dietary exposure assessment of cadmium, arsenic, and lead in market rice from Sri Lanka.

Rice is frequently reported to be contaminated with heavy metals (HMs); thus, the human health risks from its consumption have received increasing attention. A total of 165 commercial rice samples from Sri Lanka were collected to determine their cadmium (Cd), arsenic (As), and lead (Pb) concentrations. The exposure risk for Sri Lankans from the estimated daily intakes (EDIs) of these toxicants was assessed. Simultaneously, non-carcinogenic and carcinogenic risks were evaluated using hazard quotients (HQs) and the hazard index (HI). The results revealed that the average levels of Cd, As, and Pb in commercial rice were 0.080 ± 0.130, 0.077 ± 0.040, and 0.031 ± 0.050 mg/kg, respectively, with ranges of 0.003-0.727, 0.019-0.217, and 0.001-0.345 mg/kg (expressed on a dry weight basis), respectively. The average EDIs of Cd, inorganic As (iAs), and Pb were 0.772, 0.490, and 0.306 µg/kg body weight (bw)/day, respectively; these were below provisional tolerable weekly intake (PTWI) values recommended by the Joint FAO/WHO Expert Committee on Food Additives (JECFA), but iAs was above the recommended reference doses (RfDs) recommended by the United States Environmental Protection Agency (USEPA). However, approximately 25% and 75% of the Cd and iAs HQs for the Sri Lankan population, respectively, were greater than 1, suggesting a potential health risk, whereas the HQs for Pb was less than 1. Considering the additive effect, HI values of the P90, P95, P97.5, and P99 percentiles would reach 4.773, 6.458, 8.392, and 11.614, implying that intake of the combined metals might result in potential health risks.

Total mercury and methylmercury in rice: Exposure and health implications in Bangladesh.

Rice methylmercury (MeHg) contamination has attracted global attention, especially in countries where rice is considered a staple food. The daily rice intake rate in Bangladesh ranks first in the world; however, no attention has been paid to rice MeHg contamination in Bangladesh. Total Hg (THg) and MeHg concentrations of commercial rice (n = 172) from Bangladesh were first analyzed to accurately evaluate both rice MeHg and inorganic Hg (IHg) exposure in different age-gender groups of Bangladeshis. The corresponding adverse health impacts and associated economic loss were also assessed. The results showed that THg concentration in all samples ranged from 0.42 to 14.4 ng/g, with an average of 2.48 ± 1.41 ng/g, while the MeHg concentration ranged from 0.026 to 7.47 ng/g, with an average of 0.83 ± 0.60 ng/g. The highest average MeHg and IHg were both recorded in rice from Chittagong. The highest mean MeHg and IHg exposures were observed in 2-5 years-old group and were 16.2% of the reference dose (RfD) of 0.1 µg/kg/day for MeHg and 7.09% of the provisional tolerable weekly intake (PTWI) of 0.571 µg/kg/day for IHg. Surprisingly, MeHg exposure of the 2-5 year-old children could be up to 93.7% of the RfD at a high percentile (P99.9). The total intelligence quotient reduction caused by rice MeHg exposure could be 54700 points, and the associated economic loss is approximately 42.5 million USD. To avoid high rice MeHg exposure, it was suggested that diet structure be improved. More attention should be paid to residents with long-term rice MeHg exposure, especially children in the 2-5 year-old group.

Parenterally Delivered Methionyl-Methionine Dipeptide During Pregnancy Enhances Mammogenesis and Lactation Performance Over Free Methionine by Activating PI3K-AKT Signaling in Methionine-Deficient Mice.

BACKGROUND: Pregnancy-induced hypoaminoacidemia, l-methionine (Met) included, disturbs embryogenesis and may also affect breast function. Supplementation with the dipeptide l-methionyl-Met (Met-Met) may improve lactation performance. OBJECTIVE: We compared the effects of supplemental Met or Met-Met during pregnancy on mammogenesis and lactogenesis and investigated underlying mechanisms. METHODS: In experiment 1, 9-wk-old ICR mice (n = 72, ∼30 g) were divided into 3 groups. During the first 17 days of pregnancy (DP), the Control group was fed a diet with Met (8.2 g/kg) and saline was intraperitoneally injected, the Met group was fed a Met-devoid diet and 35% of the Met (92-mmo l Met) as contained in the Control diet was intraperitoneally injected, and the Met-Met group was fed the same diet and 70-mmo l Met plus 11-mmo l Met-Met was intraperitoneally injected. All animals were fed the Control diet after DP17 and during lactation. Mammogenesis, lactogenesis, transcriptome at DP17, and milk performance during lactation were examined. In experiment 2, 9-wk-old ICR mice (n = 55, ∼30 g) at DP0 were injected through the teat with adeno-associated virus for overexpression/inhibition of phosphoinositide-3-kinase regulatory subunit 1 (Pik3r1), divided into the Control, Met, and Met-Met groups and received the same treatment as experiment 1 to examine mammogenesis and lactogenesis at DP17. RESULTS: In experiment 1, compared with the Met group, the Met-Met group showed higher (P < 0.05) mammary epithelium percentage (42%) and αS1-casein expression (84%) at DP17, milk yield (34%) and energy concentrations (8.7%) during lactation; transcriptomic analysis illustrated activated phosphatidylinositol-3 kinase (PI3K)/protein kinase B (AKT) signaling in the mammary glands of the Met-Met group (P-adj < 0.001). In experiment 2, overexpression of Pik3r1 enhanced (P < 0.05) the protective effect of Met-Met over Met on mammogenesis and ß-casein expression. CONCLUSION: Met-Met is more effective than Met in promoting mammogenesis and lactogenesis mainly by activation of PI3K-AKT signaling in Met-deficient mice.

Dietary exposure assessment of total mercury and methylmercury in commercial rice in Sri Lanka.

Methylmercury (MeHg) in rice has attracted growing health concern over the past decade, due to the accumulation of high MeHg levels, which may pose potential health risk to humans. Rice is the staple food in Sri Lanka; nevertheless, the presence of micro pollutants, such as MeHg has been not investigated. Therefore, commercial rice samples from the Sri Lankan market (n = 163) were measured to reveal the total mercury (THg) and MeHg levels. THg (mean: 1.73 ±â€¯0.89 ng/g, range: 0.21-6.13 ng/g) and MeHg concentrations (mean: 0.51 ±â€¯0.37 ng/g; range: 0.03-3.81 ng/g) were low. Compared to the fish MeHg exposure, the rice MeHg exposure was generally lower in different consumption groups, suggesting that rice plays a less role than fish in MeHg exposure in Sri Lanka. Babies (infants and toddlers) at one year old may face fish MeHg exposure (0.17 µg/kg bw/day) higher than the reference dose for MeHg (RfD)-0.1 µg/kg bw/day, which was more than 5 times that of rice MeHg exposure (0.031 µg/kg bw/day). Future studies in Sri Lanka should focus on health impacts under long-term overexposure of MeHg, especially in vulnerable populations. Some diet changes should be made to mitigate MeHg exposure levels in Sri Lankans.

Methylmercury and inorganic mercury in Chinese commercial rice: Implications for overestimated human exposure and health risk.

China is the largest rice producer and consumer in the world, and mercury (Hg) levels, particularly methylmercury (MeHg), in rice and health exposure risks are public concerns. Total Hg (THg) and MeHg levels in 767 (domestic = 709 and abroad = 58) Chinese commercial rice were investigated to evaluate Hg pollution level, dietary exposures and risks of IHg and MeHg. The mean rice THg and MeHg levels were 3.97 ± 2.33 µg/kg and 1.37 ± 1.18 µg/kg, respectively. The highest daily intake of MeHg and IHg were obtained in younger groups, accounted for 6% of the reference dose-0.1 µg/kg bw/day for MeHg, 0.3% of the provisional tolerance week intake-0.571 µg/kg bw/day for IHg. Residents in Central China and Southern China meet the highest rice Hg exposure, which were more than 7 times of those in Northwest China. Lower concentrations than earlier studies were observed along the implementations of strict policies since 2007. This may indicate that a declining temporal trend of Hg in Chinese grown rice and associated exposures could be obtained with the implementations of strict policies. Though there exist Hg pollution in commercial rice, Hg levels in Chinese commercial rice is generally safe compared with Hg polluted sites. Populations dwelling in China have relatively a quite low and safe MeHg and IHg exposure via the intake of commercial rice. Strict policies contributed to the decrease in THg and MeHg levels in Chinese-grown rice. More attention should be paid to younger groups.

Characteristics, speciation, and bioavailability of mercury and methylmercury impacted by an abandoned coal gangue in southwestern China.

During coal mining activities, a lot of coal gangue is produced, which usually contains high mercury (Hg) concentrations as well as the acid mine drainage (AMD) generator of pyrite. In the present study, the total mercury (THg) and methylmercury (MeHg) in gangue, water, sediment, paddy soil, and rice samples, collected from abandoned coal mining areas, were analyzed. Results showed that the THg concentrations ranged from 0.37 to 35 mg/kg (11 ± 8.4 mg/kg) and 0.15 to 19 mg/kg (2.0 ± 3.9 mg/kg) in gangue and sediments, respectively. For paddy soils, the THg concentrations and MeHg varied from 0.16 to 0.91 mg/kg and 0.71 to 11 ng/g, respectively. Rice samples exhibited wide concentration ranges of THg (3.0-22 ng/g) and MeHg (0.71-8.9 ng/g). Sequential extraction of Hg revealed that the nitric acid-extractable state Hg (F4) was the dominant Hg species in gangue and sediment, while humic acids state Hg (F3) was the dominant form in paddy soil. Compared with gangue, higher percentages of F3 and the residual state Hg (F5) in both sediment and soil samples implied the transformation of F4 to F3 and F5 during transportation. Soil n-HAs (the difference between the total organic carbon and humic acids) were positively correlated with both THg and MeHg in soil and rice, indicating that n-HAs enhance Hg bioavailability under acidic conditions. Further studies should be conducted to reveal the factors influencing the transformation of different Hg fractions, providing ideas on decreasing the bioavailability of Hg in coal mining areas.

Transcriptional changes in the hypothalamus, pituitary, and mammary gland underlying decreased lactation performance in mice under heat stress.

Because of climate change, heat stress (HS) causes more and more impacts on dairy animals to decrease lactation performance. The neuroendocrine system is key in regulating systemic physiological processes and milk synthesis. However, the hypothalamic-pituitary axis response to HS is still unclear. In this study, a group of lactating mice underwent a daily 2-h heat treatment (36°C) for 14 d to explore possible cross-talk between the hypothalamic-pituitary axis and mammary gland under HS. Transcriptome analyses by multitissue RNA-Seq indicated the possible mechanisms of reduced lactation performance in animals under HS. In the hypothalamus, the cAMP signaling pathway was activated to resist neuronal death, and the expression of downstream genes was increased to promote cell survival under HS. Reduced food intake might be caused by down-regulated appetite-related peptide, whereas up-regulated neuropeptide Y acted to attenuate reduced food intake. In pituitary, energy stress from lower food intake might result in reduced secretion of prolactin and growth hormone. Under HS, the mammary gland may undergo hypoxic stress, causing mammary epithelial cell apoptosis. Together, these data showed systemic changes in tissues to accommodate the effects of HS on lactation.-Han, J., Shao, J., Chen, Q., Sun, H., Guan, L., Li, Y., Liu, J., Liu, H. Transcriptional changes in the hypothalamus, pituitary, and mammary gland underlying decreased lactation performance in mice under heat stress.

Impacts of selenium supplementation on soil mercury speciation, and inorganic mercury and methylmercury uptake in rice (Oryza sativa L.).

Rice grain is known to accumulate methylmercury (MeHg) and has been confirmed to be the major pathway of MeHg exposure to residents in mercury (Hg) mining areas in China. Selenium (Se) supplementation has been proven to be effective in mitigating the toxicity of Hg. To understand how Se supplementation influences soil Hg speciation, a wide range of Se (0-500 mg/kg) was applied to Hg polluted paddy soils in this study, which decreased MeHg concentration in soil from 2.95 ±â€¯0.36 to 0.69 ±â€¯0.16 µg/kg (or 77%). After Se addition, humic acid state Hg (F4) was transformed into strong-complexed state Hg (F5), indicating that Hg bound up to the non-sulfur functional groups of humic acid (non-RSH) was released and reabsorbed by strong binding Se functional group (F5). As a result, inorganic Hg (IHg) was reduced by >48%, 18%, and 80% in root, stem, and grain, respectively, however, the reduction was not apparent in leaf. Substantial reductions were also found for MeHg in grain and root, but not in stem and leaf. Soil is suggested to be the main source of both MeHg and IHg in rice grain. Such a finding may provide an idea for improving Hg-polluted paddies through controlling soil IHg and MeHg. Further research on the molecular structure of the strong-complexed Hg in F5 should be conducted to elucidate the mechanism of Hg-Se antagonism.

Health Risk Assessment of Inorganic Mercury and Methylmercury via Rice Consumption in the Urban City of Guiyang, Southwest China.

Rice consumption is the main methylmercury (MeHg) exposure route for residents in mercury (Hg) mining areas. However, there is limited studies on mercury in commercial rice, which has high liquidity and can be directly consumed by urban residents. This study measured the total Hg (THg) and MeHg concentrations in 146 rice samples purchased from the markets in Guiyang city, southwest China, and both the inorganic Hg (IHg) and MeHg estimated daily intakes (EDIs) and hazard quotients (HQs) were calculated according to rice consumption. The THg concentrations in all rice samples (range: 0.97 to 13.10 µg·kg-1; mean: 3.88 µg·kg-1) were lower than the Chinese national standard (20 µg·kg-1). The average MeHg concentration in rice was 1.16 µg·kg-1. The total HQs (THQs) ranged from 0.0106 to 0.1048, with a mean of 0.0462, which was far lower than 1. This result suggests that there were low Hg exposure levels through consumption of commercial rice in residents of Guiyang.