Biomarkers for the evaluation of population health status 16 years after the intervention of arsenic-contaminated groundwater in Xinjiang, China

Independent and combined associations of urinary arsenic exposure and serum sex steroid hormones among 6-19-year old children and adolescents in NHANES 2013-2016

Arsenic exposure may disrupt sex steroid hormones, causing endocrine disruption. However, human evidence is limited and inconsistent, especially for children and adolescents. To evaluate the independent and combined associations between arsenic exposure and serum sex steroid hormones in children and adolescents, we conducted a cross-sectional analysis of data from 1063 participants aged 6 to 19 years from the 2013-2016 National Health and Nutrition Examination Survey (NHANES). Three urine arsenic metabolites were examined, as well as three serum sex steroid hormones, estradiol (E₂), total testosterone (TT), and sex hormone-binding globulin (SHBG). The ratio of TT to E₂ (TT/E₂) and the free androgen index (FAI) generated by TT/SHBG were also assessed. Linear regression, weighted quantile sum (WQS) regression, and Bayesian kernel machine regression (BKMR) were used to evaluate the associations of individual or arsenic metabolite combinations with sex steroid hormones by gender and age stratification. Positive associations were found between total arsenic and arsenic metabolites with TT, E₂, and FAI. In contrast, negative associations were found between arsenic metabolites and SHBG. Furthermore, there was an interaction after gender-age stratification between DMA and SHBG in female adolescents. Notably, based on the WQS and BKMR model results, the combined association of arsenic and its metabolites was positively associated with TT, E₂, and FAI and negatively associated with SHBG. Moreover, DMA and MMA dominated the highest weights among the arsenic metabolites. Overall, our results indicate that exposure to arsenic, either alone or in mixtures, may alter sex steroid hormone levels in children and adolescents.

Arsenic intake-induced gastric toxicity is blocked by grape skin extract by modulating inflammation and oxidative stress in a mouse model

Arsenic (As) is known to induce toxic responses in many organs of human beings and animals. However, research concerning toxicity in the stomach is limited. In this study, arsenic-induced gastric toxicity was investigated in a mouse model, and grape skin extract (GSE) was confirmed to have protective effects against arsenic toxicity. Our experimental results showed that exposure to 10 mg/l arsenic via drinking water for 56 days caused oxidative damage and inflammatory responses. The H₂O₂ and malondialdehyde (MDA) contents were significantly increased, accompanied by significant decreases in total superoxide dismutase (T-SOD) activity and glutathione (GSH) content in the gastric tissue of arsenic-treated mice. Two inflammatory signalling pathways, i.e., TLR2/MyD88/NF-κB and IL-6/STAT-3, were activated, along with inflammatory cell infiltration and the elevated mRNA expression of pro-inflammatory cytokines (TNF-α, IL-1β and IFN-γ) and myeloperoxidase (MPO) in the gastric tissue of mice exposed to arsenic. Meanwhile, the mRNA levels of the ZO-1, ZO-2 and occludin genes, which encode the key components of tight junction (TJ) complexes, were downregulated. However, the application of GSE (300 mg/kg bw) significantly inhibited the arsenic-induced increases in H₂O₂ and MDA contents and the decreases in T-SOD activity and GSH content. The arsenic-mediated gene expression of pro-inflammatory cytokines (TNF-α, IL-1β and IFN-γ), MPO and IL-6/STAT3 and TLR2/MyD88/NF-κB pathways was found down-regulated. Moreover, the arsenic-induced inflammatory cell infiltration and inhibition of TJ genes transcription were markedly attenuated in the As+GSE (300 mg/kg bw) group. Based on the present findings, arsenic intake appears to cause gastric toxicity via oxidative stress and inflammation, and the application of GSE offers significant protection against arsenic toxicity in a mouse model by attenuating the oxidative stress and inflammatory response. Our results suggest that GSE by oral administration might function as a candidate therapeutic supplement to antagonize arsenic toxicity.

Aqueous Arsenic Speciation with Hydrogeochemical Modeling and Correlation with Fluorine in Groundwater in a Semiarid Region of Mexico

In arid and semiarid regions, groundwater becomes the main source to meet the drinking water needs of large cities, food production, and industrial activities. For this reason, necessary studies must be carried out to estimate its quantity and quality, always seeking sustainable management, thus avoiding social conflicts or a decrease in the productive activities of humanity. This research explains the behavior of groundwater quality concerning arsenic speciation and its relationship with fluoride. The average total arsenic concentration of 19.95 µg/L and 20.29 µg/L is reported for the study period from 2015 to 2020, respectively, according to the Mexican standard. If the population drinks water directly, it is exposed to possible damage to health. The predominant arsenic species is As (V), with 95% and As (III) with 5%, this finding will allow us to define in greater detail the type of remediation that is required to reduce the content of this element in the water. Regarding the relationship between arsenic and fluorine, very small Pearson correlation coefficients of the order of 0.3241 and 0.3186 were found. The estimation of the space–time variation made it possible to identify the areas with the highest concentration of arsenic and fluorine, allowing the definition of the operating policies of these wells, thereby protecting the health of the inhabitants who consume this water.

Essential hypertension in patients exposed to high-arsenic exposed areas in western China: Genetic susceptibility and urinary arsenic metabolism characteristics

OBJECTIVE

To clarify the urinary arsenic metabolism characteristics in individuals with essential hypertension and to analyze the relationship between lipid metabolism gene polymorphisms and susceptibility to essential hypertension in individuals in high-arsenic areas in western China.

METHODS

A case-control study was conducted and involved individuals exposed to high arsenic levels (in this study, the arsenic content in the pressurized well water was 0-510.2 μg/L, and that in the mechanical well water was 167 μg/L) in two adjacent high-arsenic areas in Shanxi Province and the Inner Mongolia Autonomous Region, China. A total of 699 samples were collected, including 192 case samples (patients with hypertension) and 507 control samples (no hypertension). Blood pressure measurement data obtained from an epidemiological survey were used to determine whether the subjects had hypertension, and a logistic regression model was used to analyze the association between lipid metabolism gene polymorphisms and hypertension susceptibility. Blood and urine samples were collected based on epidemiological methods, single nucleotide polymorphisms (SNPs) were genotyped using a SNPscan™ multiple SNP typing kit, and urinary arsenic concentrations were determined using the hydride generation atomic fluorescence method (HG-AFS).

RESULTS

ADIPOQ/rs266729 was the dominant genetic model [(GC + GG) vs CC = 0.686:1, 95 % CI = 0.478-0.983], and FABP2/rs1799883 was the recessive genetic model [TT vs (CC + TC) = 1.690:1, 95 % CI = 1.014-2.816]. The distribution of the urinary arsenic secondary methylation ratio (SMR) [dimethylated arsenic (DMA)/monomethylated arsenic (MMA)] was different between hypertensive patients and controls.

CONCLUSION

ADIPOQ/rs266729 and FABP2/rs1799883 polymorphisms affect susceptibility to essential hypertension in individuals exposed to high levels of arsenic; there was a clear difference in the urinary arsenic metabolism pattern between hypertensive patients and controls.

Progress in the prevention and control of water-borne arsenicosis in China

In this report, we provided an overview of the prevalence, control, and prevention of water-borne arsenicosis in China during 2001-2016. Random sampling was continuously performed during 2001-2010 to find villages having high levels of arsenic (>50 µg/L) in drinking water. The high-arsenic-exposure villages with more geographically dispersed water supplies were subsequently analyzed for characteristics of arsenic distribution, and villages with relatively large populations were investigated for arsenicosis. The results showed that among 32,673,677 inhabitants in 36,820 villages, 1,894,587 inhabitants in 2,476 villages were at risk of high arsenic exposure. Among the 33,318 drinking water sources surveyed in 625 high-arsenic-exposure villages, 9,807 drinking water sources that contained high levels of arsenic (>50 µg/L) were identified. The overall prevalence rate of arsenicosis was 1.93%. Further, some representative villages were chosen to monitor arsenicosis annually, showing that the prevalence rate of arsenicosis was lower in villages with arsenic-safe water supplies than in villages without arsenic-safe water supplies. To the best of our knowledge, this report provides the most comprehensive assessment of the distribution of high arsenic exposure and arsenicosis in China until now.

Association of low blood arsenic exposure with level of malondialdehyde among Chinese adults aged 65 and older

High environmental arsenic exposure can increase chronic oxidative stress in experimental studies and in occupational epidemiology studies. Many regulatory agencies have put forth arsenic exposure limits, it is still unclear that whether low environmental arsenic exposure was associated with adverse health outcome in general population. This study aimed to explore the association of low blood arsenic with malondialdehyde in community-dwelling older adults. We used a cross-sectional study of 2384 older adult individuals aged ≥65 years (mean age: 85 years) from the Healthy Aging and Biomarkers Cohort Study in 2017. The median blood arsenic level was 1.41 μg/L. High oxidative stress was categorized according to the 95th percentile of MDA levels (7.47 nmol/mL). Restricted cubic spline models showed that blood arsenic levels were positively associated with malondialdehyde levels (P < 0.01); and the risk of high oxidative stress was no longer significantly increased when blood arsenic level up to 8.74 μg/L. After adjusting for potential confounders, the odds ratios of high oxidative stress for the second, third, and fourth quartiles of blood arsenic were 2.35 (1.11-4.96), 3.87 (1.90-7.91), and 4.18 (2.00-8.72) (P_trend < 0.01), compared with the first quartile. We concluded that even low arsenic exposure was associated with higher risk of oxidative stress, in a nonlinear dose-response.

Arsenite induces dysfunction of regulatory T cells through acetylation control of the Foxp3 promoter

Arsenic is known to cause damage to the body's immune system by inducing epigenetic changes. However, the molecular mechanism of this damage remains elusive. Here, we report that arsenic disrupts the morphology of lymphocytes, decreases cell viability, and results in abnormal proportions of T lymphocyte subsets. Moreover, our results revealed that arsenic can reduce global acetylation of histone H4 at K16 (H4K16 ac) in lymphocytes via decreasing the level of males absent on the first but upregulates mRNA and protein levels of the forkhead/winged-helix box P3 (Foxp3) gene by increasing the acetylation of histone H4 at K16 (H4K16) at the promoter of Foxp3. Finally, arsenic-induced dysfunction of regulatory T cells (Tregs) could be ameliorated by trichostatin A. Our research indicates that arsenic-induced immunosuppressive effect in human lymphocytes may be related to the acetylation of H4K16 at the promoter of Foxp3 and that histone deacetylase inhibitors may play a role in the prevention and treatment of immune injury caused by arsenic.

Pigment epithelium-derived factor (PEDF) ameliorates arsenic-induced vascular endothelial dysfunction in rats and toxicity in endothelial EA.hy926 cells

Although the harmful effects of arsenic exposure on the cardiovascular system have received great attention, there is still no effective treatment. Vascular endothelial dysfunction (VED) is the initial step of cardiovascular diseases, where pigment epithelium-derived factor (PEDF) plays an important role in maintaining endothelial function. Here, we explored the protective role of PEDF in VED induced by arsenic, and its underlying molecular mechanism, designing an in vivo rat model of arsenic exposure recovery and in vitro endothelial EA. hy926 cell-based assays. The edema of aortic endothelial cells in rats significantly improved during recovery from arsenite exposure compared with rats exposed to 10 and 50 mg/L arsenite continuously. In addition, serum levels of nitric oxide (NO), von Willebrand factor, and nitric oxide synthase (inducible and total activities) in rats, which were greatly affected by arsenite exposure, returned to levels similar to those in the control group after recovery with distilled water. The recovery from arsenite exposure was associated with increased levels of PEDF; decreased protein levels of Fas, FasL, P53, and phospho-p38; and inhibited apoptosis in aortic endothelial cells in vivo. Recombinant human PEDF treatment (100 nM) prevented the toxic effects of arsenite (50 μM) on endothelial cells in vitro by increasing NO content, decreasing reactive oxygen species (ROS) levels, and inhibiting apoptosis, as well as increasing cell viability and decreasing levels of P53 and phospho-p38. Our findings suggest that PEDF protects endothelial cells from arsenic-induced VED by increasing NO release and inhibiting apoptosis, where P53 and p38MAPK are its main targets.

High arsenic groundwater in the Guide basin, northwestern China: Distribution and genesis mechanisms

High arsenic (As) groundwater has been found in Pliocene confined aquifers at depths from 100 to 300 m of the Guide basin, but little is known on the main hydrogeochemical processes leading to its elevated concentrations. Ninety-seven water samples and fifty-three sediment samples were collected for chemical and/or isotopic analysis. Concentrations of As in groundwater of confined aquifer range from 9.9 to 377 μg/L (average 109 μg/L), which generally show a sharply increasing trend along with NH₄⁺, HCO₃^-, CO₃^2- and TOC along the inferred flow path, while NO₃^-, SO₄^2-/Cl^- and redox potential (Eh) have decreasing trends. Results of sequential extraction show that As bound to amorphous and crystalline Fe oxide minerals are the main As forms, accounting for around 50% of total As in sediments. Reductive dissolution of As-bearing Fe(III) oxide minerals under reducing conditions in confined aquifers lead to the mobilization of As in groundwater. In addition, alkaline environment and high concentrations of HCO₃^- and CO₃^2- may make contributions to As enrichment in groundwater. High As groundwater in confined aquifer continuously flows out on the ground surface through tens of artesian wells, which may potentially contaminate low As groundwater in unconfined aquifer. Thus, further investigation is needed to evaluate long-term variations of water chemistry of low As groundwater and assess vulnerability of unconfined aquifer to As contamination.

Human health implications, risk assessment and remediation of As-contaminated water: A critical review

Arsenic (As) is a naturally occurring metalloid and Class-A human carcinogen. Exposure to As via direct intake of As-contaminated water or ingestion of As-contaminated edible crops is considered a life threatening problem around the globe. Arsenic-laced drinking water has affected the lives of over 200 million people in 105 countries worldwide. Limited data are available on various health risk assessment models/frameworks used to predict carcinogenic and non-carcinogenic health effects caused by As-contaminated water. Therefore, this discussion highlights the need for future research focusing on human health risk assessment of individual As species (both organic and inorganic) present in As-contaminated water. Various conventional and latest technologies for remediation of As-contaminated water are also reviewed along with a discussion of the fate of As-loaded waste and sludge.

Environment and Health: Not Only Cancer

The Hippocratic tradition emphasized environmental causes of diseases and the need for harmony between the individual and the natural environment as the right philosophy to maintain a good health status. Public awareness and scientific attention concerning environmental pollution is usually focused on the consequent increased risk of developing cancer. Air pollution has been recognized by the World Health Organization (WHO) to cause cardiovascular and respiratroy diseases, as well as lung cancer, after acute/chronic exposure to fine particulates (PM2.5 and PM10) even at concentrations which are 50% lower than those accepted as legal limits in many developed countries. An increase of 10 µg/m³ of PM2.5 produces a +4%-6% of overall mortality, a +10% of cardiovascular disease prevalence (arithmyas, acute myocardial infarctions, and heart failure) and a +22% of lung cancer prevalence. In addition to these chronic effects, acute hospitalizations are also affected, especially among susceptible populations such as children and diabetic patients. Water and soil contamination also have an additional detrimental effect on people's health. Other issues concerning environment contamination and human health include male/female fertility, metabolic and thyroid conditions, but also professional exposures resulting in occupational diseases. Moreover, in the perspective of "gender medicine", different acute or chronic effects of environmental pollution should be specifically assessed both in men and in women. This special issue on "Environmental Diseases" is aimed at providing a global overview about different threats to human health possibily originating from environmental contamination.

Alterations in biochemical markers due to mercury (Hg) exposure and its influence on infant's neurodevelopment

This study examined the role of oxidative stress due to mercury (Hg) exposure on infant's neurodevelopmental performance. A total of 944 healthy Saudi mothers and their respective infants (aged 3-12 months) were recruited from 57 Primary Health Care Centers in Riyadh City. Total mercury (Hg) was measured in mothers and infants urine and hair samples, as well as mother's blood and breast milk. Methylmercury (MeHg) was determined in the mothers and infants' hair and mother's blood. Urinary 8-hydroxy-2'-deoxyguanosine (8-OHdG), malondialdehyde (MDA), and porphyrins were used to assess oxidative stress. The infant's neurodevelopment was evaluated using Denver Developmental Screening Test II (DDST-II) and Parents' Evaluation of Developmental Status. The median total Hg levels in mother's urine, infant's urine, mother's hair, infant's hair, and mother's blood and breast milk were 0.995μg/l, 0.716μg/l, 0.118μg/g dw, 0.101μg/g dw, 0.635μg/l, and 0.884μg/l respectively. The median MeHg levels in mother's hair, infant's hair, and mother's blood were 0.132μg/g dw, 0.091μg/g dw, and 2.341μg/l respectively. A significant interrelationship between mothers and infants Hg measures in various matrices was noted. This suggests that mother's exposure to different forms of Hg (total and/or MeHg) from various sources contributed significantly to the metal body burden of their respective infants. Even though Hg exposure was low, it induced high oxidative stress in mothers and infants. The influence of multiplicative interaction terms between Hg measures and oxidative stress biomarkers was tested using multiple regression analysis. Significant interactions between the urinary Hg levels in mothers and infants and oxidative stress biomarkers (8-OHdG and MDA) were noted. The MeHg levels in mother-infant hair revealed similar interaction patterns. The p-values for both were below 0.001. These observations suggest that the exposure of our infants to Hg via mothers either during pregnancy and/or neonatal life, promoted oxidative stress that might have played a role in infant neurodevelopmental delays that we reported previously. The results confirmed that the interaction between infant's MeHg in hair and 8-OHdG and MDA levels was significantly associated with a delay in DDST-II performance (ß=-0.188, p=0.028). This finding provides an insight into the potential consequences of Hg-induced oxidative stress to infant's cognitive neurodevelopment for the first time. This observation still needs future studies to be validated. Given the low MeHg levels in our population, these findings are of particular importance.