Seasonal variation and source identification of heavy metal(loid) contamination in peri-urban farms of Hue city, Vietnam

m6A-methylated Lonp1 drives mitochondrial proteostasis stress to induce testicular pyroptosis upon environmental cadmium exposure

Cadmium (Cd) is a widely distributed typical environmental pollutant and one of the most toxic heavy metals. It is well-known that environmental Cd causes testicular damage by inducing classic types of cell death such as cell apoptosis and necrosis. However, as a new type of cell death, the role and mechanism of pyroptosis in Cd-induced testicular injury remain unclear. In the current study, we used environmental Cd to generate a murine model with testicular injury and AIM2-dependent pyroptosis. Based on the model, we found that increased cytoplasmic mitochondrial DNA (mtDNA), activated mitochondrial proteostasis stress occurred in Cd-exposed testes. We used ethidium bromide to generate mtDNA-deficient testicular germ cells and further confirmed that increased cytoplasmic mtDNA promoted AIM2-dependent pyroptosis in Cd-exposed cells. Uracil-DNA glycosylase UNG1 overexpression indicated that environmental Cd blocked UNG-dependent repairment of damaged mtDNA to drive the process in which mtDNA releases to cytoplasm in the cells. Interestingly, we found that environmental Cd activated mitochondrial proteostasis stress by up-regulating protein expression of LONP1 in testes. Testicular specific LONP1-knockdown significantly reversed Cd-induced UNG1 protein degradation and AIM2-dependent pyroptosis in mouse testes. In addition, environmental Cd significantly enhanced the m6A modification of Lonp1 mRNA and its stability in testicular germ cells. Knockdown of IGF2BP1, a reader of m6A modification, reversed Cd-induced upregulation of LONP1 protein expression and pyroptosis activation in testicular germ cells. Collectively, environmental Cd induces m6A modification of Lonp1 mRNA to activate mitochondrial proteostasis stress, increase cytoplasmic mtDNA content, and trigger AIM2-dependent pyroptosis in mouse testes. These findings suggest that mitochondrial proteostasis stress is a potential target for the prevention of testicular injury.

Health risk assessment of heavy metals in wild fish and seasonal variation and source identification of heavy metals in sediments: a case study of typical urban river in Xi'an, China

In order to determine the status of heavy metal pollution in river sediments and wild fish in Xi'an, concentrations of heavy metals (Cr, Ni, Cu, Zn, As, and Pb) were collected and analyzed in sediments and wild fish during dry season (October-November 2020) and wet season (June-July 2021). This study aimed to investigate the spatial and temporal variations of heavy metals in urban rivers of Xi'an, China. Their distribution characteristics and sources as well their pollution levels and health risks were assessed. The findings revealed that influenced by human activities, the heavy metal content in sediments (mg·kg-1 dry weight) in wet season was ranked as follows: Cr (73.09) > Zn (63.73) > Pb (40.31) > Ni (31.52) > Cu (24.86) > As (6.83); in the dry season: Zn (94.07) > Cr (69.59) > Cu (34.24) > Ni (33.60) > Pb (32.87) > As (7.60). Moreover, 32 fish samples from six species indicated an average metal content trend (mg·kg-1 wet weight) of Zn (8.70) > Cr (0.57) > Pb (0.28) > Ni (0.27) > Cu (0.24) > As (0.05). The potential ecological risk indices for sediment heavy metal concentrations in both seasons were well below the thresholds, which indicates that the aquatic environment is in safe level. The analysis of the potential ecological risk of sediment heavy metal concentrations indicates that the aquatic environment is safe for the time being. Based on the estimated daily intake (EDI), target risk quotient (THQ), total target risk quotient (TTHQ), cancer risk (CR), total cancer risk (TCR), and the permissible safety limits set by the agencies, the consumption of the fish examined is safe for human health. However, the presence of Cr and As in wild fish should still be a concern for human health, especially for children. The cumulative effect of heavy metals and the bioconcentration factor (BCF) suggest that sediment and heavy metals in fish are closely related, with higher concentrations in fish living in the bottom layer of the water column than in other water layers, and increasing with increasing predator levels. Correlation analysis and PMF modeling identified and determined four comparable categories of potential sources, namely, (1) atmospheric deposition and traffic sources, (2) agricultural sources, (3) industrial sources, and (4) natural sources.

Are high-risk heavy metal(loid)s contaminated vegetables detrimental to human health? A study of incorporating bioaccessibility and toxicity into accurate health risk assessment

Heavy metal(loid)s in the environment threaten food safety and human health. Health risk assessment of vegetables based on total or bioaccessible heavy metal(loid)s was widely used but can overestimate their risks, so exploring accurate methods is urgent for food safety evaluation and management. In this study, a total of 224 frequently consumed vegetables and their corresponding grown soils were collected from Yunnan, Southwest China. The total contents and bioaccessibilities of heavy metal(loid)s in vegetables were measured, their health risks were evaluated using the non-carcinogenic and carcinogenic risk models provided by USEPA. Besides, the gastrotoxicity of high-risk vegetables was also evaluated using a human cell model. Results showed that 6.25-43.8 % of Cr, Cd, and Pb contents in Zea mays L., Coriandrum sativum L., or Allium sativum L. exceeded the maximum permissible level of China, which were not consistent with those in corresponding soils. The bioaccessibility of Cr, Cd, As, Pb, Cu, Zn, Ni, and Mn in vegetables in the gastric phase was 0.41-93.8 %. Health risks based on bioaccessibility were remarkably decreased compared with total heavy metal(loid)s, but the unacceptable carcinogenic risk (CR > 10-4) was found even considering the bioaccessibility. Interestingly, gastric digesta of high-risk vegetables did not trigger adverse effects on human gastric mucosa epithelial cells, indicating existing health risk assessment model should be adjusted by toxic data to accurately reflect its hazards. Taken together, both bioaccessibility and toxicity of heavy metal(loid)s in vegetables should be considered in accurate health risk assessment and food safety-related policy-making and management.

Spatial distribution, sources, and risk assessment of potentially toxic elements in cultivated soils using isotopic tracing techniques and Monte Carlo simulation

Potentially toxic elements (PTEs) in cultivated lands pose serious threats to the environment and human health. Therefore, improving the understanding of their distinct sources and environmental risks by integrating various methods is necessary. This study investigated the distribution, sources, and environmental risks of eight PTEs in cultivated soils in Lishui City, eastern China, using digital soil mapping, positive matrix factorisation (PMF), isotopic tracing, and Monte Carlo simulation. The results showed that Pb and Cd are the main pollutants, which posed higher ecological risks in the study area than the other PTEs. Natural, mining, traffic, and agricultural sources were identified as the four determinants of PTE accumulation via a PMF model combined with Pearson correlation analysis, showing that their contribution rates were 22.6 %, 45.7 %, 15.2 %, and 16.5 %, respectively. Stable isotope analysis further confirmed that local mining activities affected the HM accumulation. Additionally, non-carcinogenic and carcinogenic risk values for children were 3.18 % and 3.75 %, respectively, exceeding their acceptable levels. We also identified that mining activities were the most important sources of human health risks (55.7 % for adults and 58.6 % for children) via Monte Carlo simulations coupled with the PMF model. Overall, this study provides insights into the PTE pollution management and health risk control in cultivated soils.

Levels of heavy metal in soil and vegetable and associated health risk in peri-urban areas across China

Peri-urban vegetable field plays an essential role in providing vegetables for local residents. Because of its particularity, it is affected by both industrial and agricultural activities which have led to the accumulations of heavy metal in soil. So far, information on heavy metal pollution status, spatial features, and human health risks in peri-urban vegetable areas across China is still scarce. To fill this gap, we systematically compiled soil and vegetable data collected from 123 articles published between 2010 and 2022 at a national level. The pollution status of heavy metals (i.e., cadmium (Cd), mercury (Hg), arsenic (As), lead (Pb), chromium (Cr), copper (Cu), nickel (Ni), and zinc (Zn)) in peri-urban vegetable soils and vegetables were investigated. To evaluate the levels of heavy metal pollution in soil and human health risks, the geoaccumulation index (Igeo) and target hazard quotient (HQ) were calculated. The results showed that mean concentrations of Cd, Hg, As, Pb, Cr, Cu, Ni, and Zn in peri-urban vegetable soils were 0.50, 0.53, 12.03, 41.97, 55.56, 37.69, 28.55, and 75.38 mg kg^-1, respectively. The main pollutants in peri-urban vegetable soil were Cd and Hg, and 85.25% and 92.86% of the soil samples had I_geo > 1, respectively. The mean I_geo values of this regions followed the order of northwest > central > south > north > east > southwest > northeast for Cd and northeast > northwest > north > southwest > east > central > south for Hg. The mean Cd, Hg, As, Pb, Cr, Cu, Ni, and Zn concentrations in vegetables were 0.30, 0.26, 0.37, 0.54, 1.17, 6.17, 1.96, and 18.56 mg kg^-1, respectively. Approximately 87.01% (Cd), 71.43% (Hg), 20% (As), 65.15% (Pb), 27.08% (Cr) of the vegetable samples exceeded the safety requirement values. The vegetables grown in central, northwest, and northern China accumulated much more heavy metals than those grown in other regions. As the HQ values for adults, 53.25% (Cd), 71.43% (Hg), 84.00% (As), and 58.33% (Cr) of the sampled vegetables were higher than 1. For children, the HQ values were higher than 1 for 66.23% (Cd), 73.81% (Hg), 86.00% (As), and 87.50% (Cr) of the sampled vegetables. The findings of this study demonstrate that the situation of heavy metal pollution in peri-urban vegetable areas across China are not optimistic and residents who consume the vegetables are at high risk of health issues. To ensure soil quality and human health, strategies should be taken to guide vegetable production and remedy soil pollution in peri-urban areas with the rapidly urbanizing China.

Heavy metal(loid)s in agriculture soils, rice, and wheat across China: Status assessment and spatiotemporal analysis

Heavy metal(loid)s (HMs) accumulation in agricultural soils, rice, and wheat is of particular concern in China, while the status and spatio-temporal distribution of HMs in the soil-crops system have been rarely reported at the national scale. This study aimed to summarize the overall pollution status, spatiotemporal patterns, and drivers of HMs in agricultural soil, rice, and wheat nationwide. The metal-polluted data from 1030 agricultural soils, rice, and wheat in China were collected from the literature published from 2000 to 2022. The results showed that Cd was the most prevailing contaminant in soils based on its spatiotemporal distribution and accumulation. The pollution cases and severe pollution percentage of Cd (103 %) and Hg (128 %) show an increasing trend pattern. Mining activities are the main anthropogenic sources of agricultural soil HMs in China. Cd and Pb had the highest exceedance rate in rice (33.5 and 32.2 %) and wheat (25.8 and 30.3 %). The rice from Hunan, Fujian, and Guangxi showed the highest average concentration of Cd and Pb, respectively, while wheat samples from Hubei had the greatest exceedance rate of Pb. Besides, HMs in crops was not usually corresponding to soil HMs but increased gradually from north to south areas. Several mitigation strategies and accurate health risk assessments model of HMs based on bioavailability were also proposed and recommended. Collectively, this review provides valuable information to improve the management of farmland nationwide, optimize the accurate risk assessment, and reduce HMs pollution.

Identification of Metal Contamination Sources and Evaluation of the Anthropogenic Effects in Soils near Traffic-Related Facilities

Traffic-related facilities typically have much lower metal emissions than other sources; however, they can be numerous and widespread as well. Subdividing pollution sources is necessary to assess soil contamination characteristics and identify sources according to the contamination cause. Anthropogenic contamination by metals was quantitatively determined using contamination factor (Cf) and evaluated using multivariate analysis. More than half of the concentrations for Zn, Pb, and Cu in soils were higher than that in the natural background (NB). Cf of metals was, in decreasing order, Zn > Pb = Cu > Ni = As. Zn, Pb, and Cu were identified as anthropogenic contaminants in correlation analysis. Principal component analysis showed that the two main contamination causes were coarse particles from the maintenance or crushing activities of vehicles and nonexhaust/exhaust emissions. Clusters were classified according to those two anthropogenic and lithogenic causes and included Group I (Zn, Pb, and Cu in garages, auto repair shops, and auto salvage yards), Group II (Zn, Pb, and Cu in parking lots, driving schools, and roadsides), and Group III (As and Ni with high lithogenic properties). Anthropogenic input and sources of soil contamination by metals in traffic-related facilities were appropriately estimated through the combination of Cf and multivariate analysis.