Biomarkers of cadmium and arsenic interactions

Analysis of relationship between mixed heavy metal exposure and early renal damage based on a weighted quantile sum regression and Bayesian kernel machine regression model

BACKGROUND

Occupation, environmental heavy metal exposure, and renal function impairment are closely related. The relationship between mixed metal exposure and chronic renal injury is inadequately described, and the interaction between each metal is poorly explored.

OBJECTIVE

This cross-sectional study assessed mixed heavy metal exposure in the general population and their relationship with early renal impairment, as well as possible interactions between metals.

METHODS

The study was conducted in two communities in Taiyuan City in northern China. Multiple linear regression, weighted quantile sum (WQS) and bayesian kernel machine regression (BKMR) regression were used to explore the relationship of mixed heavy metal exposure with indicators of early kidney injury (N-acetyl-β-D- glucosidase (UNAG), urinary albumin (UALB)). Meanwhile, BKMR was used to explore the possible interactions between mixed heavy metal and indicators of early kidney injury.

RESULTS

Based on the WQS regression results, we observed adjusted WQS coefficient β (β-WQS) of 0.711 (95% CI: 0.543, 0.879). Notably, this change was primarily driven by As (35.6%) and Cd (22.5%). In the UALB model, the adjusted β-WQS was 0.657 (95% CI: 0.567, 0.747), with Ni (30.5%), Mn (22.1%), Cd (21.2%), and As (18.6%) exhibiting higher weights in the overall effect. The BKMR results showed a negative interaction between As and other metals in the UNAG and UALB models, a positive interaction between Mn and Ni and other metals. No significant pairwise interaction was observed in the association of metals with indicators of early kidney injury.

CONCLUSION

Through multiple linear regression, WQS regression, and BKMR analyses, we found that exposure to mixed heavy metals such as Cd, Cr, Pb, Mn, As, Co and Ni was positively correlated with UNAG and UALB. Moreover, there are complex interactions between two or more heavy metals in more than one direction.

Study on the mechanism of arsenic-induced renal injury based on SWATH proteomics technology

BACKGROUND

Arsenic (As) poisoning is a worldwide endemic disease affecting thousands of people. As is excreted mainly through the renal system, and arsenic has toxic effects on the kidneys, but the mechanism has not been elucidated. In this study, the molecular basis of arsenic's nephrotoxicity was studied by using a high-throughput proteomics technique.

METHODS

Eight SD (Sprague-Dawley) rats, half male and half female, were fed an As diet containing 50 mg/kg NaAsO2. Age- and sex-matched rats fed with regular chow were used as controls. At the end of the experiment (90 days), kidney tissue samples were collected and assessed for pathological changes using hematoxylin-eosin staining. Proteomic methods were used to identify alterations in protein expression levels in kidney tissues, and bioinformatic analyses of differentially expressed proteins between arsenic-treated and control groups were performed. The expression of some representative proteins was validated by Western blot analysis.

RESULTS

NaAsO2 could induce renal injury. Compared with the control group, 112 proteins were up-regulated, and 46 proteins were down-regulated in the arsenic-treated group. These proteins were associated with the electron transport chain, oxidative phosphorylation, mitochondrial membrane, apoptosis, and proximal tubules, suggesting that the mechanisms associated with them were related to arsenic-induced kidney injury and nephrotoxicity. The expressions of Atp6v1f, Cycs and Ndufs1 were verified, consistent with the results of omics.

CONCLUSION

These results provide important evidence for arsenic-induced kidney injury and provide new insights into the molecular mechanism of arsenic-induced kidney injury.

Coexposure to multiple metals and renal tubular damage: a population-based cross-sectional study in China's rural regions

Previous studies have indicated that exposure to a single toxic metal can cause renal tubular damage, while evidence about the effects of multimetal exposure on renal tubular damage is relatively limited. We aimed to evaluate the relationships of multimetal coexposure with renal tubular damage in adults in heavy metal-polluted rural regions of China. A cross-sectional study of 1918 adults in China's heavy metal-contaminated rural regions was conducted. Inductively coupled plasma-mass spectrometry (ICP-MS) was used to measure the plasma levels of 18 metals in participants, and immune turbidimetry was used to measure sensitive biological indicators, reflecting renal tubular damage (including retinol-binding protein and β2-microglobulin). Least absolute shrinkage and selection operator (LASSO) penalized regression analysis, logistic and linear regression analysis, restricted cubic spline (RCS) regression analysis and the Bayesian kernel machine regression (BKMR) method were used to explore associations of multimetal coexposure with renal tubular damage risk or renal tubular damage indicators. Plasma selenium, cadmium, arsenic, and iron were identified as the main plasma metals associated with renal tubular damage risk after dimensionality reduction. Multimetal regression models showed that selenium was positively associated, and iron was negatively associated with renal tubular damage risk or its biological indicators. Multimetal RCS analyses additionally revealed a non-linear relationship of selenium with renal tubular damage risk. The BKMR models showed that the metal mixtures were positively associated with biological indicators of renal tubular damage when the metal mixtures were above the 50th percentile of concentration. Our findings indicated that natural exposure to high levels of multimetal mixtures increases the risk of renal tubular damage. Under the conditions of multimetal exposure, selenium was positively associated, and iron was negatively associated with renal tubular damage risk or its biological indicators.

Exposure to essential and non-essential trace elements and risks of congenital heart defects: A narrative review

Congenital heart defects (CHDs) are congenital abnormalities involving the gross structures of the heart and large blood vessels. Environmental factors, genetic factors and their interactions may contribute to the pathogenesis of CHDs. Generally, trace elements can be classified into essential trace elements and non-essential trace elements. Essential trace elements such as copper (Cu), zinc (Zn), iron (Fe), selenium (Se), and manganese (Mn) play important roles in human biological functions such as metabolic function, oxidative stress regulation, and embryonic development. Non-essential trace elements such as cadmium (Cd), arsenic (As), lead (Pb), nickle (Ni), barium (Ba), chromium (Cr) and mercury (Hg) are harmful to health even at low concentrations. Recent studies have revealed the potential involvement of these trace elements in the pathogenesis of CHDs. In this review, we summarized current studies exploring exposure to essential and non-essential trace elements and risks of CHDs, in order to provide further insights for the pathogenesis and prevention of CHDs.

Association between levels of exposure to heavy metals and renal function indicators of residents in environmentally vulnerable areas

Abandoned metal mines and refineries are considered environmentally vulnerable areas owing to high levels of exposure to heavy metals. This study examined the association between heavy metal exposure and renal function indicators. We studied a total of 298 participants, of which 74 and 68 resided in low- and high-exposure abandoned metal mine areas, respectively, with 121 in the refinery area and 35 in the control area. Blood and urine samples were collected from the participants to analyze the levels of blood lead, cadmium, and creatinine and urinary cadmium, NAG, and β2-MG. The estimated glomerular filtration rate, which is calculated using the Chronic Kidney Disease Epidemiology Collaboration equation, was used for assessments. The study participants comprised more females than males, and their mean age was 70.3 years. The blood lead and cadmium as well as urinary cadmium levels were 2.12 μg/dL, 1.89 μg/L, and 2.11 μg/L, respectively, in the heavy metal-exposure areas, and 1.18 μg/dL, 0.89 μg/L, and 1.11 μg/L, respectively, in the control area. The odds ratio (OR) for exceeding the reference value showed that blood cadmium in the refinery area was 38 times higher than that in the control area. Urinary cadmium was seven times higher in the low-exposure abandoned metal mine area than in the control area. NAG showed a positive correlation with urinary cadmium in all areas. In the refinery area, correlations were observed between β2-MG and urinary cadmium levels and the eGFR and blood cadmium level; in the high-exposure abandoned metal mine area, correlations were observed between NAG, β2-MG, and the eGFR and blood cadmium. In this study, the association between Cd exposure and some renal function indicators was observed. This study's findings and the obtained biological samples can serve as a basis for future molecular biological research.

Impact of Heavy Metal Toxicity on the Gut Microbiota and Its Relationship with Metabolites and Future Probiotics Strategy: a Review

The gut microbiota has a vital role in the maintenance of intestinal homeostasis. Several studies have revealed that environmental exposure to pollutants such as heavy metals may contribute to the progression of extensive list of diseases which may further lead to perturbations in the gut leading to dysbiosis. This manuscript critically reviews the alterations in the gut microbiota composition and function upon exposure to various toxic heavy metals prevalent in the environment. The disturbance in gut microbial ecology also affects the microbial metabolic profile which may alter the speciation state and bioavailability heavy metals thus affecting metal uptake-absorption/detoxification mechanisms associated to heavy metal metabolism. The toxic effects of various heavy metals either in single or in multimetallic combination and the gut microbiota associated host health and disease condition need a comprehensive assessment with important consideration for therapeutic and protective strategies against the damage to gut microbiota.

Human biomonitoring survey (Pb, Cd, As, Cu, Zn, Mo) for urban gardeners exposed to metal contaminated soils

Eighty eight adult gardeners and their relatives volunteered to provide urine and blood samples for a human biomonitoring survey among users of one of the biggest allotment garden from Wallonia, showing high trace metal(oid) concentrations in soils. The purpose was to determine if environmental levels of lead (Pb), cadmium (Cd) and arsenic (As) led to concentrations of potential health concern in the study population. Blood and urine biomarkers were compared to reference and intervention cut-off values selected from the literature. The study population exhibited (i) moderately high blood lead levels with median value of 23.1 μg/L, (ii) high urinary concentrations of speciated As (inorganic arsenic and its metabolites) with a median value of 7.17 μg/g.cr., i.e. twice the median values usually observed in general populations, and (iii) very high Cd levels in urine with a median value of 1.23 μg/L, in the range of 95th-97.5th percentiles measured in general adult populations. Biomarker levels in the study population were also mostly above those measured in adults from local populations living on contaminated soils, as reported in the current literature. All biomarkers of Pb, Cd and As showed weak to strong statistically significant correlations, pointing towards a joint environmental source to these three contaminants as being at least partially responsible for the high exposure levels observed. Urine and blood biomarkers show statistically significant associations with variables related to individual characteristics (age, smoking status, …) and Pb domestic sources (Pb pipes, cosmetics, …) but involves also behavioral and consuming habits related to gardening activities on the contaminated allotment garden. At such levels, owing to co-exposure and additive effects of Cd, As and Pb regarding renal toxicity known from literature, the study strongly suggests that this population of gardeners is at risk with respect to chronic kidney diseases.

Association between plasma cadmium and renal stone prevalence in adults in rural areas of Guangxi, China: a case-control study

Background

Kidney stones have become a worldwide public health problem. The purpose of this research is to study the relationship between plasma cadmium level and the prevalence of kidney stones in an adult population.

Methods

The data of this study were based on a current survey conducted from December 2018 to November 2019 in Gongcheng Yao Autonomous County, Guangxi, China. A total of 940 study subjects of the same sex and age (within 2 years of each other) according to 1:1 matching were selected for a case–control study. The diagnosis of kidney stones was based on the presence of strong light spots, patches, clusters, or bands within the renal sinus region, followed by an echo-free bundle of acoustic images. Plasma metal elements were determined by the metal plasma method. The relationship between plasma cadmium concentration and the prevalence of kidney stones was assessed using logistic regression and restricted cubic spline regression.

Results

The crude ratio for kidney stones in the highest quartile of plasma cadmium was 1.164 (95% CI, 1.121 to 2.324) compared with the lowest quartile. A positive correlation was found between the two (P for trend = 0.039). After adjusting for potential confounders, the ratio of plasma cadmium to kidney stones in the highest quartile was 1.606 (95% CI, 1.100 to 2.344) compared with the lowest quartile, and the findings remained unchanged.

Conclusion

The odds of kidney stones in adults increased with increasing plasma cadmium exposure, and high plasma cadmium may be a risk factor for kidney stones.

Impact of "chemical cocktails" exposure in shaping mice gut microbiota and the role of selenium supplementation combining metallomics, metabolomics, and metataxonomics

Biological systems are exposed to a complex environment in which pollutants can interact through synergistic or antagonistic mechanisms, but limited information is available on the combined effects. To this end, conventional and antibiotic-treated (Abx) mice models were fed regular rodent or selenium (Se) supplemented diets and exposed to a "chemical cocktail" (CC) including metals and pharmaceuticals. Metallomics, metabolomics, and metataxomics were combined to delve into the impact on gut microbiota, plasma selenoproteome, metabolome, and arsenic metabolization. At the molecular level, Se decreased the concentration of the antioxidant glutathione peroxidase in plasma and increased the arsenic methylation rate, possibly favoring its excretion, but not in the Abx and also plasma metabolomes of Abx, and Abx-Se were not differentiated. Moreover, numerous associations were obtained between plasma selenoproteins and gut microbes. Se-supplementation partially antagonizes the gut microbiota alteration caused by Abx, and slightly by CC, but strongly altered profiles were observed in CC-Abx-Se, suggesting synergistic deleterious effects between pollutants, Abx and Se. Moreover, although CC and Abx changed gut microbiota, several common taxa were enriched in CC-Abx and control mice, indicating possible synergistic effects. Our results suggest a potential beneficial impact of supplementation, but mediated by gut microbes being reversed in their absence.

E-WASTE threatens health: The scientific solution adopts the one health strategy

The aggressively extractive advanced technology industry thrives on intensive use of non-renewable resources and hyper-consumeristic culture. The environmental impact of its exponential growth means extreme mining, hazardous labour practices including child labour, and exposure burden to inorganic and organic hazardous chemicals for the environment and current and future human generations. Globally, processes such as in-country reduce, reuse and recycle have so far received less attention than outer-circle strategies like the uncontrolled dumping of e-waste in countries that are unprotected by regulatory frameworks. Here, in the absence of infrastructures for sound hazardous e-waste management, the crude recycling, open burning and dumping into landfills of e-waste severely expose people, animal and the environment. Along with economic, political, social, and cultural solutions to the e-waste global problem, the scientific approach based on risk analysis encompassing risk assessment, risk management and risk communication can foster a technical support to resist transgenerational e-waste exposure and health inequalities. This paper presents the latest public health strategies based on the use of integrated human and animal biomonitoring and appropriate biomarkers to assess and manage the risk of e-waste embracing the One Health approach. Advantages and challenges of integrated biomonitoring are described, along with ad-hoc biomarkers of exposure, effect and susceptibility with special focus on metals and metalloids. Indeed, the safe and sustainable management of novel technologies will benefit of the integration and coordination of human and animal biomonitoring.

Prenatal arsenic exposure, arsenic methylation efficiency, and neuropsychological development among preschool children in a Spanish birth cohort

BACKGROUND

Prenatal arsenic (As) exposure could negatively affect child neuropsychological development, but the current evidence is inconclusive.

OBJECTIVES

To explore the relationship between prenatal urinary total As (TAs) concentrations, the As species and the methylation efficiency, and child neuropsychological development in a Spanish birth cohort. We also studied the effect modification produced by sex and several nutrients and elements.

MATERIALS AND METHODS

Study subjects were 807 mother-child pairs participating in the INMA (Childhood and Environment) Project. Urinary TAs and its metabolites, monomethylarsonic acid (MMA), dimethylarsinic acid (DMA), inorganic As (iAs) and arsenobetaine were measured in the first trimester of pregnancy. Methylation efficiency was determined through the percentages of the metabolites and using principal component analysis. Children's neuropsychological development was assessed at the age of 4-5 years using the McCarthy Scales of Children's Abilities (MSCA). Multivariable linear regression models were built to assess the association between TAs, the As species and the maternal methylation efficiency, and the neuropsychological scores. We explored effect modification by sex, iron status, maternal nutrients status (serum manganese and selenium, and urinary zinc), and maternal vitamins intake (folate, and vitamins B₁₂ and B₆).

RESULTS

The geometric mean (95%CI) of ∑As (sum of DMA, MMA and iAs) was 7.78 (7.41, 8.17) μg/g creatinine. MMA concentrations were inversely associated with the scores for the general, verbal, quantitative, memory, executive function and working memory scales (i.e. β [CI95%] = -1.37 [-2.33, -0.41] for the general scale). An inverse association between %MMA and the memory scores was found. Children whose mothers had lower manganese, zinc and ferritin concentrations obtained lower scores on several MSCA scales with decreasing As methylation efficiency.

DISCUSSION

An inverse association was observed between MMA concentrations and children's neuropsychological development. Maternal levels of manganese, zinc and ferritin affected the association between As methylation efficiency and MSCA scores.

The Groundwater Geochemistry and the Human Health Risk Assessment of Drinking Water in an Area with a High Prevalence of Chronic Kidney Disease of Unknown Etiology (CKDu), Sri Lanka

Chronic kidney disease of unknown etiology (CKDu) has become an alarming health issue in Sri Lanka. The disease is more notable among farming communities and people who consume groundwater as their main source of drinking water. To assess the possible links between drinking water chemistry and expansion of CKDu, the study was compared with hydrogeochemical data of drinking water sources in a CKDu prevalent area (Girandurukotte GND, Badulla District) and a reference area (Dambethalawa GND, Ampara District) in Sri Lanka. Based on the results, nephrotoxic heavy metal (Cd, Cr, Pb, and As) concentrations were significantly higher in the CKDu prevalent site than the reference area, compromised the harmful consequences to the people in the CKDu hotspot. Results of the inverse distance weighted (IDW) interpolation tool indicated the nephrotoxic heavy metals contents including Cd, Pb, As, and Cr in CKDu hotspot were changed in the ranges of 9.78–187.25 μg/L, 0.08–0.66 μg/L, 20.76–103.30 μg/L, and 0.03–0.34 μg/L. The random distribution patterns were shown by the result in Moran’s index values. Noteworthy, the results have emphasized a strong association between fluoride and water hardness. The frequency of occurrence above the threshold limit of fluoride was 28% in non-CKDu water samples, while 81% in CKDu prevalent sites. The hardness values in the CKDu prevalent site indicated “moderately hard water,” while the non-CKDu area indicated the “soft water.” Furthermore, this paper quantified overall water quality and heavy metal contamination and assessed the human health risks associated with drinking water. According to the results of the water quality index, 90% of the samples in the CKDu prevalent area were classified as “poor water” and “very poor water” for drinking purposes, while 73.33% of the samples in the non-CKDu area were “good” and “excellent” for drinking usage. Calculated chronic daily intake (CDIoral) and hazard quotient (HQoral) of nephrotoxicants were higher in CKDu hotspot than the non-CKDu site. Besides, the hazard index (HI) values obtained for the CKDu prevalent area exceeding the acceptable limit (HI = 1) indicated potential health risks to the people in those areas. This study suggests that long-term exposure to nephrotoxic heavy metals, water hardness, and fluoride present in drinking water may threaten human health and affect kidney functions. Therefore, regular monitoring and better management of water supplies in CKDu prevalent areas are essential to determine the contamination load and reduce the health impacts due to excessive and long-term exposure to the nephrotoxicants.

Associations between urinary heavy metal concentrations and blood pressure in residents of Asian countries

BACKGROUND

Previous studies have suggested that exposures to heavy metals (arsenic, cadmium, lead, and selenium) may be associated with differences in blood pressure. However, the findings of these studies have been inconsistent. This study was performed to examine the associations between urinary heavy metal concentrations and blood pressure among residents of four Asian countries (Bangladesh, Indonesia, Nepal, and Vietnam).

METHODS

This cross-sectional study examined 1899 adults in four Asian countries. Urinary concentrations of heavy metals were measured by inductively coupled plasma mass spectrometry. A questionnaire survey was administered regarding individual characteristics. Anthropometric measurements (height and weight) were performed. Systolic and diastolic blood pressures were measured after a short rest. Multiple linear regression models were applied to investigate associations between urinary heavy metal concentrations and blood pressure after adjustments for age, sex, and body mass index.

RESULTS

The geometric means of the urinary concentrations of arsenic, cadmium, lead, and selenium were 84.6, 0.885, 2.09, and 16.5 μg/g creatinine, respectively. The urinary arsenic concentrations were slightly higher than those typically reported in non-polluted populations, while urinary cadmium, lead, and selenium concentrations were equivalent or slightly lower. The urinary lead concentrations were positively associated with both systolic and diastolic blood pressure, but urinary selenium concentrations were negatively associated with them.

CONCLUSIONS

Variations in the urinary concentrations of lead and selenium were associated with blood pressure at low levels of exposure/intake.

Impact of modernization on urinary concentrations of arsenic, cadmium, lead, and selenium in rural residents of Northern Laos

OBJECTIVES

The impacts of modernization on toxic heavy metal exposure and essential trace element intake in indigenous populations of subsistence societies are unknown. We assessed urinary trace element concentrations in rural residents of Northern Laos and examined associations with levels of modernization.

METHODS

A cross-sectional study was conducted comprising 380 residents of three villages in Northern Laos with different levels of modernization. We surveyed general characteristics and measured the weight and height of 341 participants. Arsenic, cadmium, lead, and selenium concentrations were measured in spot urine samples by inductively coupled plasma mass spectrometry. We examined associations between urinary trace element concentrations and variables related to modernization (village, roofing material, possessions index [total number of possessions], and body mass index [BMI]) using multilevel analyses with household as a random effect, after adjusting for sex, age, and smoking status.

RESULTS

Urinary concentrations of arsenic and cadmium were high, while those of lead and selenium were low in comparison to previous reports of populations in non-contaminated regions or without excess/deficiency. We observed associations between urinary trace element concentrations and village-level modernization: lead and selenium concentrations were higher in more modernized villages and cadmium concentration was highest in the least modernized village. Urinary arsenic concentration was not predicted by the modernization level of a village, although we observed significant differences among villages. In addition, urinary selenium concentration was higher in participants inhabiting more modernized houses.

CONCLUSION

Modernization of villages may impact toxic heavy metal exposure and selenium intake in rural residents of Northern Laos.

Contribution of diet and other factors for urinary concentrations of total arsenic and arsenic species: data for US children, adolescents, and adults

A comprehensive analysis of the associations between the consumptions of 17 food products with urinary concentrations of arsenobetaine, total arsenic, arsenous acid, dimethylarsinic acid (UDMA), monomethylarsonic acid (UMMA), and total inorganic arsenic for US children aged 3-5 years (N = 439), children aged 6-11 years (N = 2139), adolescents aged 12-19 years (N = 2434), and adults aged >= 20 years (N = 10902) was conducted. Data from National Health and Nutrition Examination Survey for 2005-2016 were used for this study. Concentrations of arsenobetaine were as much as > 15 times higher among consumers of fish/shellfish than non-consumers for children aged 6-11 years, > 12 times higher for children aged 3-5 years, > 13 times higher for adolescents, and > 7 times higher for adults. Consumption of rice as opposed to non-consumption of rice was associated with as much as 36.5% higher concentrations of total arsenic, 12.7% higher concentrations of arsenous acid, 43.9% higher concentrations of UDMA, 18.2% higher concentrations of UMMA, and 14.1% higher concentrations of total inorganic arsenic. Thus, consumption of fish/shell fish and rice was associated with higher concentrations of organic/inorganic arsenic. In addition, consumption of alcohol was also found to be associated with higher concentrations of organic/inorganic arsenic. However, consumption of milk and milk products, vegetables, organ and other meats, and nutritional drinks was found to be associated with lower concentrations of organic/inorganic arsenic. Thus, while consumption of several foods is associated with higher concentrations of arsenic, there are also foods whose consumption is associated with decreased concentrations of arsenic. Further studies are needed to identify foods that may lead to decreased concentrations of arsenic and as such arsenic toxicity.

Urinary arsenic species and methylation efficiency during pregnancy: Concentrations and associated factors in Spanish pregnant women

BACKGROUND

Arsenic (As) is considered to be toxic for humans, the main routes of exposure being through drinking water and the diet. Once ingested, inorganic arsenic can be methylated sequentially to monomethyl and dimethyl arsenicals. Several factors can affect both As exposure and methylation efficiency.

OBJECTIVES

To describe the urinary concentrations of the different As species and evaluate the methylation efficiency during pregnancy, as well as their associated factors in a birth cohort of pregnant Spanish women.

METHODS

Participants in this cross-sectional study were 1017 pregnant women from two areas of Spain who had taken part in the INMA (Environment and Childhood) project (2003-2008). Total As (organic and inorganic compounds) and its main metabolites (monomethylarsonic acid, [MMA], dimethylarsinic acid, [DMA], inorganic As [iAs]) and arsenobetaine [AB]) were measured in urine samples collected during the first trimester. Sociodemographic and dietary information was collected through questionnaires. Multivariate linear regression models were used to explore the association between As species concentrations and covariates. Arsenic methylation efficiency was determined through the percentages of the metabolites and using As methylation phenotypes, obtained from principal component analysis.

RESULTS

Median urine concentrations were 33.0, 21.6, 6.5, 0.35 and 0.33 μg/g creatinine for total As, AB, DMA, MMA and iAs, respectively. Daily consumption of rice and seafood during the first trimester of pregnancy were positively associated with the concentration of As species (i.e., β [CI95%] = 0.36 [0.09, 0.64] for rice and iAs, and 1.06 [0.68, 1.44] for seafood and AB). TAs, AB and iAs concentrations, and DMA and MMA concentrations were associated with legume and vegetable consumption, respectively. The medians of the percentage of As metabolites were 89.7 for %DMA, 5.1 for %MMA and 4.7 for %iAs. Non-smoker women and those with higher body mass index presented a higher methylation efficiency (denoted by a higher %DMA and lower %MMA).

DISCUSSION

Certain dietary, lifestyle, and environmental factors were observed to have an influence on both As species concentrations and methylation efficiency in our population. Further birth cohort studies in low exposure areas are necessary to improve knowledge about arsenic exposure, especially to inorganic forms, and its potential health impact during childhood.

Environmental exposures and sleep outcomes: A review of evidence, potential mechanisms, and implications

Environmental exposures and poor sleep outcomes are known to have consequential effects on human health. This integrative review first seeks to present and synthesize existing literature investigating the relationship between exposure to various environmental factors and sleep health. We then present potential mechanisms of action as well as implications for policy and future research for each environmental exposure. Broadly, although studies are still emerging, empirical evidence has begun to show a positive association between adverse effects of heavy metal, noise pollution, light pollution, second-hand smoke, and air pollution exposures and various sleep problems. Specifically, these negative sleep outcomes range from subjective sleep manifestations, such as general sleep quality, sleep duration, daytime dysfunction, and daytime sleepiness, as well as objective sleep measures, including difficulties with sleep onset and maintenance, sleep stage or circadian rhythm interference, sleep arousal, REM activity, and sleep disordered breathing. However, the association between light exposure and sleep is less clear. Potential toxicological mechanisms are thought to include the direct effect of various environmental toxicants on the nervous, respiratory, and cardiovascular systems, oxidative stress, and inflammation. Nevertheless, future research is required to tease out the exact pathways of action to explain the associations between each environmental factor and sleep, to inform possible therapies to negate the detrimental effects, and to increase efforts in decreasing exposure to these harmful environmental factors to improve health.

The Response of the Associations of Grass and Epichloë Endophytes to the Increased Content of Heavy Metals in the Soil

The rapid development of civilization increases the area of land exposed to the accumulation of toxic compounds, including heavy metals, both in water and soil. Endophytic fungi associated with many species of grasses are related to the resistance of plants to biotic and abiotic stresses, which include heavy metals. This paper reviews different aspects of symbiotic interactions between grass species and fungal endophytes from the genera Epichloë with special attention paid to the elevated concentration of heavy metals in growing substrates. The evidence shows the high resistance variation of plant endophyte symbiosis on the heavy metals in soil outcome. The fungal endophytes confer high heavy metal tolerance, which is the key feature in its practical application with their host plants, i.e., grasses in phytoremediation.

A longitudinal study of rural Bangladeshi children with long-term arsenic and cadmium exposures and biomarkers of cardiometabolic diseases

There is growing interest in understanding the contribution of environmental toxicant exposure in early life to development of cardiometabolic diseases (CMD) in adulthood. We aimed to assess associations of early life exposure to arsenic and cadmium with biomarkers of CMD in children in rural Bangladesh. From a longitudinal mother-child cohort in Matlab, Bangladesh, we followed up 540 pairs. Exposure to arsenic (U-As) and cadmium (U-Cd) was assessed by concentrations in urine from mothers at gestational week 8 (GW8) and children at ages 4.5 and 9 years. Blood pressure and anthropometric indices were measured at 4.5 and 9 years. Metabolic markers (lipids, glucose, hemoglobin A1c, adipokines, estimated glomerular filtration rate (eGFR) were determined in plasma/blood of 9 years old children. In linear regression models, adjusted for child sex, age, height-for-age z score (HAZ), BMI-for-age z score (BAZ), socioeconomic status (SES) and maternal education, each doubling of maternal and early childhood U-Cd was associated with 0.73 and 0.82 mmHg increase in systolic blood pressure (SBP) respectively. Both early and concurrent childhood U-Cd was associated with diastolic (D)BP (β = 0.80 at 4.5 years; β = 0.75 at 9 years). Each doubling of U-Cd at 9 years was associated with decrements of 4.98 mg/dL of total cholesterol (TC), 1.75 mg/dL high-density lipoprotein (HDL), 3.85 mg/dL low-density lipoprotein (LDL), 0.43 mg/dL glucose and 4.29 units eGFR. Each doubling of maternal U-Cd was associated with a decrement of 1.23 mg/dL HDL. Both maternal and childhood U-As were associated with decrement in TC and HDL. Multiple comparisons were checked with family-wise error rate Bonferroni-type-approach. The negative associations of arsenic and cadmium with biomarkers of CMD in preadolescent children indicated influence of both metal(loid)s on fat and carbohydrate metabolism, while cadmium additionally influenced kidney function and BP. Thus, fewer outcomes were associated with U-As compared to U-Cd at preadolescence.

Concentrations of selected arsenic species in urine across various stages of renal function including hyperfiltration

Data (N = 10,590) from National Health and Nutrition Examination Survey for 2005-2016 for US adults aged ≥ 20 years were analyzed to study how concentrations of arsenobetaine (UAB), monomethylarsonic acid (UMMA), dimethylarsenic acid (UDMA), and total arsenic (UAS) in urine vary across the stages of renal function (RF). Data were analyzed over RF-1A (eGFR > 110 mL/min/1.73 m²), RF-1B (eGFR between 90 and 110 mL/min/1.73 m²), RF-2 (eGFR between 60 and 90 mL/min/1.73 m²), RF-3A (eGFR between 45 and 60 mL/min/1.73 m²), and RF-3B/4 (eGFR between 15 and 45 mL/min/1.73 m²). Adjusted geometric mean (AGM) concentrations of the total population, males, and females for UAS, UAB, and UDMA were observed to follow inverted U-shaped distributions with points of inflection located at RF-3A. For example, adjusted concentrations for the total population for UAS were 8.8, 8.8, 9.5, 11.7, and 9.6 μg/L for those in RF-1A, RF-1B, RF-2, RF-3A, and RF-3B/4 respectively. While statistically significant differences were only occasionally observed, males, in general, had lower AGMs than females for UAS and UDMA, but females had lower AGMs than males for UAB. Among the various racial/ethnic groups, non-Hispanic whites had the lowest adjusted concentrations of all four arsenic variables. Adjusted levels of all four arsenic variables were observed to decrease over survey years of 2005-2006 through 2015-2016. However, statistical significance was not necessarily reached for all RF stages. Smoking was associated with reduced levels of four arsenic variables over RF-1A through RF-2. Diabetes was associated with increased levels of UMMA and UDMA at RF-2.

Cell Viability and Immune Response to Low Concentrations of Nickel and Cadmium: An In Vitro Model

Environmental exposure to low concentrations of heavy metals is common in the general population, but the toxicity, immune response mechanisms, and the effects of single and mixed metal exposures have not been clearly identified. In this study, A549 cells and Raw264.7 cells were exposed to low concentrations of the heavy metals nickel (Ni) and cadmium (Cd) for 24, 48, and 72 h, and then cell viability and cytokine levels were analyzed. We found that exposure to low concentrations of Ni (50 nM) or Cd (10 nM) alone did not affect cell viability. However, mixing them together decreased cell viability. In addition, the levels of IL-10, IL-12, and TNF-α decreased with single (only Cd) and mixed (Ni and Cd) exposures. These results show that exposure to low concentrations of heavy metals could affect the normal immune response, even without obvious clinical manifestations. Therefore, chronic exposure to heavy metals might have adverse effects on overall health.

Metal-induced nephrotoxicity to diabetic and non-diabetic Wistar rats

The present study was conducted to examine the nephrotoxic effects of heavy metals including lead (Pb), manganese (Mn), arsenic (As), and cadmium (Cd) in diabetic and non-diabetic Wistar rats. Animals were exposed to heavy metals for 30 days, Pb was injected as lead acetate (C₄H₆O₄Pb), Mn was injected as manganese chloride (MnCl₂), Cd was injected as cadmium chloride (CdCl₂), and As was administered orally to rats in the form of sodium arsenite (AsO₂Na). Results showed that metal deposition trends in tissues were Pb > As > Cd > Mn and the urinary metal levels were Pb > Cd > As > Mn. Diabetic metal alone, as well as metal mixture-treated groups, showed decreased urinary metal levels as compared with non-diabetic metal alone and metal mixture-treated groups. Both diabetic- and non-diabetic metal mixture-treated groups revealed an increasing trend of blood urea nitrogen (BUN) and serum creatinine. In addition, heavy metal treatments resulted in elevated malondialdehyde (MDA) levels in the kidney tissue while decreased levels of catalase (CAT), superoxide dismutase (SOD), glutathione peroxidase (GPx), and glutathione (GHS) were observed in the kidney tissue in comparison with the control group. The histological analysis of the kidney tissues showed tubular degeneration, fibrosis, and vacuolation as a result of heavy metal exposure. The present study revealed that co-exposure of heavy metals (Pb, Cd, Mn, As) induced more nephrotoxicity as compared with the metal alone treatment. Moreover, diabetic Wistar rats are more prone to kidney damage as a result of heavy metal exposure.

miR-191 is involved in renal dysfunction in arsenic-exposed populations by regulating inflammatory response caused by arsenic from burning arsenic-contaminated coal

Chronic exposure to arsenic may result in the manifestation of damage in multiple organs or systems of the body. Arsenic-induced renal dysfunction has been determined, but their pathogenesis has not been fully examined. In this study, we measured the expression levels of miR-191 in plasma, the contents of pro-inflammatory (interleukin (IL)-6 and tumor necrosis factor alpha) and anti-inflammatory (IL-2 and transforming growth factor beta) cytokines, and renal dysfunction indicators (blood urea nitrogen, blood creatinine, uric acid, and cystatin C) in serum from control and arsenic poisoning populations and analyzed the relationship between the miR-191, cytokines, and renal dysfunction indicators. The results clearly show the alteration of miR-191 expression was significantly associated with arsenic-induced renal dysfunction. Overall, the association of miR-191, inflammatory response and renal dysfunction, is clearly supported by the current findings. In other words, miR-191 is involved in renal dysfunction in exposed populations by regulating inflammatory response caused by coal-burning arsenic. The study provides a scientific basis for further studies of the causes of the arsenic-induced renal dysfunction, the biological role of miR-191, and targeted prevention strategies.

The effects of dietary selenomethionine on tissue-specific accumulation and toxicity of dietary arsenite in rainbow trout (Oncorhynchus mykiss) during chronic exposure

Selenomethionine facilitated arsenic deposition in the brain and likely in other tissues, possibly via bio-complexation. Elevated dietary selenomethionine can increase the tissue-specific accumulation and toxicity of As³⁺ in fish during chronic dietary exposure.

Influence of co-contaminant exposure on the absorption of arsenic, cadmium and lead

Incidental ingestion of contaminated soil and dust is a major pathway for human exposure to many inorganic contaminants. To date, exposure research has focused on arsenic (As), cadmium (Cd) and lead (Pb), however, these studies have typically assessed metal(loid) bioavailability individually, even when multiple elements are present in the same matrix. As a consequence, it is unclear whether interactions between these elements occur within the gastro-intestinal tract, which may impact absorption and accumulation. In this study, the influence of contaminant co-exposure was assessed using a mouse bioassay and soluble forms of As, Cd and Pb supplied in mouse chow as individual, binary and tertiary elemental combinations. Arsenic urinary excretion and Pb-liver accumulation were unaffected by As-Pb co-exposure (1-10 mg As kg^-1 and 3-30 mg Pb kg^-1) while Cd-kidney accumulation was unaffected by the presence of As and/or Pb. However, Cd co-exposure decreased As urinary excretion and increased Pb-liver accumulation. It was hypothesized that Cd influenced arsenate absorption as a consequence of the impairment of phosphate transporters. Although the reason for increasing Pb-liver accumulation following Cd co-exposure is unclear, enhanced Pb accumulation may occur as a result of transport protein overexpression or changes in divalent metal compartmentalization.

A review of toxicity and mechanisms of individual and mixtures of heavy metals in the environment

The rational for the study was to review the literature on the toxicity and corresponding mechanisms associated with lead (Pb), mercury (Hg), cadmium (Cd), and arsenic (As), individually and as mixtures, in the environment. Heavy metals are ubiquitous and generally persist in the environment, enabling them to biomagnify in the food chain. Living systems most often interact with a cocktail of heavy metals in the environment. Heavy metal exposure to biological systems may lead to oxidation stress which may induce DNA damage, protein modification, lipid peroxidation, and others. In this review, the major mechanism associated with toxicities of individual metals was the generation of reactive oxygen species (ROS). Additionally, toxicities were expressed through depletion of glutathione and bonding to sulfhydryl groups of proteins. Interestingly, a metal like Pb becomes toxic to organisms through the depletion of antioxidants while Cd indirectly generates ROS by its ability to replace iron and copper. ROS generated through exposure to arsenic were associated with many modes of action, and heavy metal mixtures were found to have varied effects on organisms. Many models based on concentration addition (CA) and independent action (IA) have been introduced to help predict toxicities and mechanisms associated with metal mixtures. An integrated model which combines CA and IA was further proposed for evaluating toxicities of non-interactive mixtures. In cases where there are molecular interactions, the toxicogenomic approach was used to predict toxicities. The high-throughput toxicogenomics combines studies in genetics, genome-scale expression, cell and tissue expression, metabolite profiling, and bioinformatics.

Performance IQ in children is associated with blood cadmium concentration in early pregnancy

OBJECTIVE

To investigate whether performance IQ in children is associated with maternal blood cadmium concentration in early pregnancy.

METHOD

The present study is a component of the Mothers' and Children's Environmental Health (MOCEH) study, a multi-center birth cohort project in Korea that began in 2006. The study cohort consisted of 119 children whose mothers underwent testing of blood cadmium during early pregnancy. All children were evaluated using the Korean version of the Wechsler Preschool and Primary Scale of Intelligence, revised edition (WPPSI-R), at 60 months of age. Multivariate linear regression analysis was performed to analyze the correlation between IQ in children and maternal blood cadmium concentration in early pregnancy, after adjustment for covariates.

RESULTS

Maternal blood cadmium concentration during early pregnancy was inversely associated with performance IQ, after adjustment for covariates such as sex, educational levels of both parents, family income, and maternal BMI. Maternal blood cadmium concentration, however, was not associated with cognitive IQ.

CONCLUSION

Performance IQ in children is associated with maternal blood cadmium concentration in early pregnancy.

Effects of anesthetics pentobarbital sodium and chloral hydrate on urine proteome

Urine can be a better source than blood for biomarker discovery since it accumulates many changes. The urine proteome is susceptible to many factors, including anesthesia. Pentobarbital sodium and chloral hydrate are commonly used anesthetics in animal experiments. This study demonstrated the effects of these two anesthetics on the rat urine proteome using liquid chromatography–tandem mass spectrometry (LC-MS/MS). With anesthesia, the urinary protein-to-creatinine ratio of all rats increased twofold. The relative abundance of 22 and 23 urinary proteins were changed with pentobarbital sodium or chloral hydrate anesthesia, respectively, as determined by label-free quantification. Among these changed proteins, fifteen had been considered as candidate biomarkers such as uromodulin, and sixteen had been considered stable in healthy human urine, which are more likely to be considered as potential biomarkers when changed, such as transferrin. The pattern of changed urinary proteins provides clues to the discovery of urinary proteins regulatory mechanisms. When determining a candidate biomarker, anesthetic-related effects can be excluded from future biomarker discovery studies. Since anesthetics take effects via nervous system, this study is the first to provide clues that the protein handling function of the kidney may possibly be regulated by the nervous system.

Heavy metal toxicity and the environment

Heavy metals are naturally occurring elements that have a high atomic weight and a density at least five times greater than that of water. Their multiple industrial, domestic, agricultural, medical, and technological applications have led to their wide distribution in the environment, raising concerns over their potential effects on human health and the environment. Their toxicity depends on several factors including the dose, route of exposure, and chemical species, as well as the age, gender, genetics, and nutritional status of exposed individuals. Because of their high degree of toxicity, arsenic, cadmium, chromium, lead, and mercury rank among the priority metals that are of public health significance. These metallic elements are considered systemic toxicants that are known to induce multiple organ damage, even at lower levels of exposure. They are also classified as human carcinogens (known or probable) according to the US Environmental Protection Agency and the International Agency for Research on Cancer. This review provides an analysis of their environmental occurrence, production and use, potential for human exposure, and molecular mechanisms of toxicity, genotoxicity, and carcinogenicity.

Arsenic-mediated nephrotoxicity

Chronic kidney disease (CKD) is an important global health problem that affects 8-15% of the population according to epidemiological studies done in different countries. Essential to prevention is the knowledge of the environmental factors associated with this disease, and heavy metals such as lead and cadmium are clearly associated with kidney injury and CKD progression. Arsenic is one of the most abundant contaminants in water and soil, and many epidemiological studies have found an association between arsenic and type 2 diabetes mellitus, hypertension and cancer; however, there is a scarcity of epidemiological studies about its association with kidney disease, and the evidence linking urinary arsenic excretion with CKD, higher urinary excretion of low molecular proteins, albuminuria or other markers of renal in injury is still limited, and more studies are necessary to characterize the role of arsenic on renal injury and CKD progression. Global efforts to reduce arsenic exposure remain important and research is also needed to determine whether specific therapies are beneficial in susceptible populations.

Co-exposure of arsenic and cadmium through drinking water and tobacco smoking: risk assessment on kidney dysfunction

The combined exposure of arsenic (As) and cadmium (Cd) causes more pronounced renal toxicity. The study aimed to evaluate the level of As and Cd in biological samples (blood and urine) of adults males, age ranged (30-50 years) exposed referent (ER) and exposed kidney patients (EKP), consumed contaminated drinking water of lake and smoking local cigarettes manufactured by tobacco plants grown on agricultural soil, irrigated with contaminated lake water. For comparative purpose age matched nonexoposed referent (NR) and nonexposed kidney patient (NKP), consumed municipal treaded water and smoking branded cigarette were also selected. The As and Cd levels in drinking water, biological samples, tobacco of branded and nonbranded cigarettes were analyzed using electrothermal atomic absorption spectrometry. The As and Cd concentrations in lake water were higher than the permissible limit recommended by the World Health Organization for drinking water. The As and Cd levels in local cigarette tobacco were found to be 3- to 4-folds higher than branded cigarettes. The biochemical parameters especially urinary N-acetyl-β-glucosaminidase (NAG) of ER, EKP, ER, and EKP subjects were studied as a biomarkers of renal dysfunction. The NAG values were found to be higher in EKP as compared to NKP (p < 0.01). The linear regressions showed higher correlations between As and Cd concentrations in water versus blood and urine samples of EKP (r = 0.71-0.78 and 0.68-0.72), as compared to NKP (p < 0.05).

Creatinine, arsenic metabolism, and renal function in an arsenic-exposed population in Bangladesh

Kidney disease is emerging as an arsenic (As)-linked disease outcome, however further evidence of this association is warranted. Our first objective for this paper was to examine the potential renal toxicity of As exposure in Bangladesh. Our second objective relates to examining whether the previously reported positive association between urinary creatinine (uCrn) and As methylation may be explained by renal function. We had hypothesized that these associations relate to supply and demand for s-adenosylmethionine, the methyl donor for both creatine synthesis and As methylation. Alternatively, renal function could influence both As and creatinine excretion, or the As metabolites may influence renal function, which in turn influences uCrn. We conducted a cross-sectional study (N = 478) of adults, composed of a sample recruited in 2001 and a sample recruited in 2003. We assessed renal function using plasma cystatin C, and calculated the estimated glomerular filtration rate (eGFR). Consistent with renal toxicity of As, log-uAs had a marginal inverse association with eGFR in the 2003 sample (b = -5.6, p = 0.07), however this association was not significant in the 2001 sample (b = -1.9, p = 0.24). Adjustment for eGFR did not alter the associations between uCrn and the %uAs metabolites, indicating that GFR does not explain these associations. Increased eGFR was associated with increased odds of having %uInAs >12.2% (2001: OR = 1.01, 95%CI (1.00,1.03); 2003: OR = 1.04, 95%CI (1.01,1.07)). In the 2003 sample only, there was a negative association between eGFR and %uDMA (b = -0.08, p = 0.02). These results may indicate differential effects of renal function on excretion of InAs and DMA. Alternatively, a certain methylation pattern, involving decreased %InAs and increased %DMA, may reduce renal function. Given that these studies were cross-sectional, we cannot distinguish between these two possibilities. Discrepancies between the samples may be due to the higher As exposure, poorer nutrition, and lower As methylation capacity in the 2003 sample.

Urinary concentrations of toxic and essential trace elements among rural residents in Hainan Island, China

BACKGROUND

Toxic element exposure and essential trace element consumption may have changed after the Chinese economy transformed to a market-oriented system. The objectives of this study were to measure urinary concentrations of toxic (arsenic, cadmium, lead) and essential trace (selenium, zinc, copper) elements among rural residents in Hainan, China and to examine if variations in economic development are linked to differences in toxic and trace element exposure.

METHODS

We conducted a questionnaire-based survey and undertook anthropometric measurements of residents aged ≥20 years (n = 599). Urinary samples were collected and analyzed using inductively coupled plasma mass spectrometry.

RESULTS

The median (μg/g creatinine) element concentrations were: arsenic, 73.2; cadmium, 1.8; lead, 3.1; selenium, 36.5; zinc, 371; and copper, 11.0. Intra-community variation in element concentrations was explained by age (arsenic, cadmium, zinc and copper), sex (arsenic, cadmium and selenium: higher in females; zinc: higher in males), body mass index (cadmium) and individual involvement in the market economy as indexed by agrochemical use (lead and selenium). The degree of community-level economic development, which was determined by the proportion of people living in better housing among the study communities, was positively associated with cadmium concentration.

CONCLUSIONS

The degree of community-level economic development was positively associated with urinary cadmium concentration while individual involvement in the market economy was positively associated with lead and selenium.

Arsenic and Chronic Kidney Disease: A Systematic Review

In epidemiologic studies, high arsenic exposure has been associated with adverse kidney disease outcomes. We performed a systematic review of the epidemiologic evidence of the association between arsenic and various kidney disease outcomes. The search period was January 1966 through January 2014. Twenty-five papers (comprising 24 studies) meeting the search criteria were identified and included in this review. In most studies, arsenic exposure was assessed by measurement of urine concentrations or with an ecological indicator. There was a generally positive association between arsenic and albuminuria and proteinuria outcomes. There was mixed evidence of an association between arsenic exposure and chronic kidney disease (CKD), β-2 microglobulin (β2MG), and N-acetyl-β-D-glucosaminidase (NAG) outcomes. There was evidence of a positive association between arsenic exposure and kidney disease mortality. Assessment of a small number of studies with three or more categories showed a clear dose-response association between arsenic and prevalent albuminuria and proteinuria, but not with CKD outcomes. Eight studies lacked adjustment for possible confounders, and two had small study populations. The evaluation of the causality of the association between arsenic exposure and kidney disease outcomes is limited by the small number of studies, lack of study quality, and limited prospective evidence. Because of the high prevalence of arsenic exposure worldwide, there is a need for additional well-designed epidemiologic and mechanistic studies of arsenic and kidney disease outcomes.

Iron deficiency increases blood cadmium levels in adolescents surveyed in KNHANES 2010-2011

Discrepancies have been reported in the relationships between iron and cadmium concentrations. The distribution of blood cadmium concentrations was assessed in a representative sample of Korean adolescents participating in the Korean National Health and Nutritional Examination Survey (KNHANES) 2010-2011, and the association between blood cadmium and iron concentrations was determined. This study was based on data from KNHANES, in which a rolling sampling design was used to perform a complex, stratified, multistage probability cluster survey of a representative sample of the noninstitutionalized civilian population in South Korea. Serum ferritin was categorized as low (<15.0 μg/L), low normal (15.0-<30.0 μg/L for girls, 15.0-<50.0 μg/L for boys), or normal (≥30.0 μg/L for girls, ≥50.0 μg/L for boys), and the association between serum ferritin and blood cadmium concentrations was assessed after adjustment for various demographic and lifestyle factors. The geometric mean (GM) of blood cadmium was significantly higher among both boys and girls in the low than in the normal ferritin group. After controlling for covariates, multiple regression analysis showed that blood cadmium concentration was inversely correlated with serum ferritin concentration in both boys and girls. In conclusion, iron deficiency is associated with increased blood cadmium concentrations in a representative sample of Korean adolescents, as evaluated in KNHANES.

Accumulation of heavy metals in leaf vegetables from agricultural soils and associated potential health risks in the Pearl River Delta, South China

This study investigated the extent of heavy metal accumulation in leaf vegetables and associated potential health risks in agricultural areas of the Pearl River Delta (PRD), South China. Total concentrations of mercury (Hg), cadmium (Cd), lead (Pb), chromium (Cr) and arsenic (As) were determined in 92 pairs of soil and leaf vegetable (flowering Chinese cabbage, lettuce, pakchoi, Chinese cabbage, loose-leaf lettuce, and Chinese leaf mustard) samples collected from seven agricultural areas (cities). The bioconcentration factors (BCF) of heavy metals from soil to vegetables were estimated, and the potential health risks of heavy metal exposure to the PRD residents through consumption of local leaf vegetables were assessed. Results showed that among the six leaf vegetables, pakchoi had the lowest capacity for heavy metal enrichment, whereas among the five heavy metals, Cd had the highest capacity for transferring from soil into vegetables, with BCF values 30-fold those of Hg and 50-fold those of Cr, Pb and As. Sewage irrigation and fertilization were likely the main sources of heavy metals accumulated in leaf vegetables grown in agricultural areas of the PRD region. Different from previous findings, soil pH had no clear effect on metal accumulation in leaf vegetables. Despite a certain degree of metal enrichment from soil to leaf vegetables, the PRD residents were not exposed to significant health risks associated with consumption of local leaf vegetables. Nevertheless, more attention should be paid to children due to their sensitivity to metal pollutants.

A combination of metallomics and metabolomics studies to evaluate the effects of metal interactions in mammals. Application to Mus musculus mice under arsenic/cadmium exposure

Arsenic and cadmium are toxic metals of environmental significance with harmful effects on man. To study the toxicological and biochemical effects of arsenic/cadmium in mammals a combined metallomic and metabolomic approach has been developed, complemented with the measurement of biochemical parameters in blood and histopathological evaluation of liver injury in mice Mus musculus under exposure to both xenobiotics. Size-exclusion chromatography (SEC) was combined with affinity chromatography (AF) and ICP-MS detection using species unspecific isotopic dilution analysis (SUID) to characterize the biological effects of As/Cd on selenium containing proteins in the bloodstream of exposed mice. On the other hand, both direct infusion mass spectrometry (DIMS) and gas chromatography-mass spectrometry (GC-MS) provided information about changes in metabolites caused by metals. The results show that As/Cd exposure produces interactions in the distribution of both toxics between organs and plasma of mice and antagonistic interactions with selenium containing proteins in the bloodstream. Interplay with essential metabolic pathways, such as energy metabolism and breakdown of membrane phospholipids were observed, which are more pronounced under As/Cd exposure. In addition, heavy metal and metalloid causes differential liver injury, manifested by steatosis (non-alcoholic fatty liver disease, NAFLD) and infiltration of blood cells into the space of Disse.

BIOLOGICAL SIGNIFICANCE

This work presents new contributions in the study of arsenic/cadmium interactions in mice Mus musculus under controlled exposure. With the combination of metallomic and metabolomic approaches the traffic of As and Cd from liver to kidney by means of blood was observed and excretion of As (as arsenic metabolites) or Cd (as MTCd) is inhibited with the simultaneous administration of As/Cd, and these toxic elements have important influence in the levels of seleno-proteins in the plasma. In addition, the metabolomic approach reveals inhibition of different metabolic cycles such as tricarboxylic acid and phospholipid degradation that causes membrane damage and apoptosis that is histopathologically confirmed. This article is part of a Special Issue entitled: Environmental and structural proteomics.

Evaluation of factors associated with cadmium exposure and kidney function in the general population

Cadmium (Cd) is a nonessential toxic metal which is widely distributed in the environment. The general population is exposed to low levels of Cd and the kidney is the organ most sensitive to Cd toxicity. This study was performed to simultaneously evaluate Cd exposure, kidney function, and oxidative stress biomarkers in the general population. A total of 643 adults were interviewed to document demographic characteristics, lifestyles, past-medical history, and diet during the last 24 h. We estimated daily Cd intake based on the diet of study subjects who had not been exposed to Cd occupationally. Whole blood and urine samples were collected and analyzed to determine Cd concentrations and kidney function indices (β₂ -microglobulin [β₂-MG], N-acetyl-β-D-glucosaminidase [NAG], metallothionein [MT]). The oxidative stress index (malondialdehyde [MDA]) was determined from the urine. The daily Cd intake from diet was established as 7.07 μg/day. The mean concentration of Cd measured in the blood was 1.22 μg/L and urine was 0.95 μg/g creatinine. The concentrations of Cd in blood and urine were higher in females than in males. The blood levels of Cd were affected by sex, age, and smoking, and urine Cd was influenced by sex, age, and blood Cd. The urine Cd was positively correlated with MT, NAG activity, and MDA in females, but with NAG only in males. The blood Cd was associated with MT in males. Increased NAG activity was observed when Cd in urine reached 1.0 μg Cd/g creatinine and was also affected by age, hypertension, and diabetes mellitus. Urinary MT only responded to Cd in urine or blood. In summary, exposure to Cd in the general population was influenced by various factors including sex, age, and smoking habits. Such exposure might eventually cause tubular damage in the kidneys through the oxidative stress mechanism, and females might be more susceptible than males to Cd exposure under the environment.

Chronic kidney disease of uncertain aetiology: prevalence and causative factors in a developing country

BACKGROUND

This study describes chronic kidney disease of uncertain aetiology (CKDu), which cannot be attributed to diabetes, hypertension or other known aetiologies, that has emerged in the North Central region of Sri Lanka.

METHODS

A cross-sectional study was conducted, to determine the prevalence of and risk factors for CKDu. Arsenic, cadmium, lead, selenium, pesticides and other elements were analysed in biological samples from individuals with CKDu and compared with age- and sex-matched controls in the endemic and non-endemic areas. Food, water, soil and agrochemicals from both areas were analysed for heavy metals.

RESULTS

The age-standardised prevalence of CKDu was 12.9% (95% confidence interval [CI] = 11.5% to 14.4%) in males and 16.9% (95% CI = 15.5% to 18.3%) in females. Severe stages of CKDu were more frequent in males (stage 3: males versus females = 23.2% versus 7.4%; stage 4: males versus females = 22.0% versus 7.3%; P < 0.001). The risk was increased in individuals aged >39 years and those who farmed (chena cultivation) (OR [odds ratio] = 1.926, 95% CI = 1.561 to 2.376 and OR = 1.195, 95% CI = 1.007 to 1.418 respectively, P < 0.05). The risk was reduced in individuals who were male or who engaged in paddy cultivation (OR = 0.745, 95% CI = 0.562 to 0.988 and OR = 0.732, 95% CI = 0.542 to 0.988 respectively, P < 0.05). The mean concentration of cadmium in urine was significantly higher in those with CKDu (1.039 μg/g) compared with controls in the endemic and non-endemic areas (0.646 μg/g, P < 0.001 and 0.345 μg/g, P < 0.05) respectively. Urine cadmium sensitivity and specificity were 70% and 68.3% respectively (area under the receiver operating characteristic curve = 0.682, 95% CI = 0.61 to 0.75, cut-off value ≥0.397 μg/g). A significant dose-effect relationship was seen between urine cadmium concentration and CKDu stage (P < 0.05). Urine cadmium and arsenic concentrations in individuals with CKDu were at levels known to cause kidney damage. Food items from the endemic area contained cadmium and lead above reference levels. Serum selenium was <90 μg/l in 63% of those with CKDu and pesticides residues were above reference levels in 31.6% of those with CKDu.

CONCLUSIONS

These results indicate chronic exposure of people in the endemic area to low levels of cadmium through the food chain and also to pesticides. Significantly higher urinary excretion of cadmium in individuals with CKDu, and the dose-effect relationship between urine cadmium concentration and CKDu stages suggest that cadmium exposure is a risk factor for the pathogensis of CKDu. Deficiency of selenium and genetic susceptibility seen in individuals with CKDu suggest that they may be predisposing factors for the development of CKDu.

Chronic kidney disease of uncertain aetiology: prevalence and causative factors in a developing country

BACKGROUND

This study describes chronic kidney disease of uncertain aetiology (CKDu), which cannot be attributed to diabetes, hypertension or other known aetiologies, that has emerged in the North Central region of Sri Lanka.

METHODS

A cross-sectional study was conducted, to determine the prevalence of and risk factors for CKDu. Arsenic, cadmium, lead, selenium, pesticides and other elements were analysed in biological samples from individuals with CKDu and compared with age- and sex-matched controls in the endemic and non-endemic areas. Food, water, soil and agrochemicals from both areas were analysed for heavy metals.

RESULTS

The age-standardised prevalence of CKDu was 12.9% (95% confidence interval [CI] = 11.5% to 14.4%) in males and 16.9% (95% CI = 15.5% to 18.3%) in females. Severe stages of CKDu were more frequent in males (stage 3: males versus females = 23.2% versus 7.4%; stage 4: males versus females = 22.0% versus 7.3%; P < 0.001). The risk was increased in individuals aged >39 years and those who farmed (chena cultivation) (OR [odds ratio] = 1.926, 95% CI = 1.561 to 2.376 and OR = 1.195, 95% CI = 1.007 to 1.418 respectively, P < 0.05). The risk was reduced in individuals who were male or who engaged in paddy cultivation (OR = 0.745, 95% CI = 0.562 to 0.988 and OR = 0.732, 95% CI = 0.542 to 0.988 respectively, P < 0.05). The mean concentration of cadmium in urine was significantly higher in those with CKDu (1.039 μg/g) compared with controls in the endemic and non-endemic areas (0.646 μg/g, P < 0.001 and 0.345 μg/g, P < 0.05) respectively. Urine cadmium sensitivity and specificity were 70% and 68.3% respectively (area under the receiver operating characteristic curve = 0.682, 95% CI = 0.61 to 0.75, cut-off value ≥0.397 μg/g). A significant dose-effect relationship was seen between urine cadmium concentration and CKDu stage (P < 0.05). Urine cadmium and arsenic concentrations in individuals with CKDu were at levels known to cause kidney damage. Food items from the endemic area contained cadmium and lead above reference levels. Serum selenium was <90 μg/l in 63% of those with CKDu and pesticides residues were above reference levels in 31.6% of those with CKDu.

CONCLUSIONS

These results indicate chronic exposure of people in the endemic area to low levels of cadmium through the food chain and also to pesticides. Significantly higher urinary excretion of cadmium in individuals with CKDu, and the dose-effect relationship between urine cadmium concentration and CKDu stages suggest that cadmium exposure is a risk factor for the pathogensis of CKDu. Deficiency of selenium and genetic susceptibility seen in individuals with CKDu suggest that they may be predisposing factors for the development of CKDu.

Biomarkers of renal toxicity caused by exposure to arsenic in drinking water

This study is intended to explore effective and sensitive biomarkers for kidney damage after low level arsenic (As) exposure and to provide scientific evidence on cut-off values of arsenic concentrations in drinking water. The levels of α1-MG detected in urine samples were found to have statistically significant differences between high As group (As>0.05 mg/L) and a combination of low and medium As exposure groups (As<0.05 mg/L, p=0.018), as well as between the patient and high As groups (As in two group were both higher than 0.05 mg/L, p<0.001). After the logistic regression analysis the AUC values of α1-MG between two comparisons were 0.613 and 0.701, and p value was less than 0.05. The present data demonstrate the potential value of α1-MG excretion as a biomarker of renal toxicity, which could contribute to the enforcement of the maximum limit of 0.05 mg/L arsenic in drinking water for non-central water supply in rural areas.

Urine arsenic and prevalent albuminuria: evidence from a population-based study

BACKGROUND

Long-term arsenic exposure is a major global health problem. However, few epidemiologic studies have evaluated the association of arsenic with kidney measures. Our objective was to evaluate the cross-sectional association between inorganic arsenic exposure and albuminuria in American Indian adults from rural areas of Arizona, Oklahoma, and North and South Dakota.

STUDY DESIGN

Cross-sectional. SETTING & PARTIPANTS: Strong Heart Study locations in Arizona, Oklahoma, and North and South Dakota. 3,821 American Indian men and women aged 45-74 years with urine arsenic and albumin measurements.

PREDICTOR

Urine arsenic.

OUTCOMES

Urine albumin-creatinine ratio and albuminuria status.

MEASUREMENTS

Arsenic exposure was estimated by measuring total urine arsenic and urine arsenic species using inductively coupled plasma mass spectrometry (ICPMS) and high-performance liquid chromatography-ICPMS, respectively. Urine albumin was measured by automated nephelometric immunochemistry.

RESULTS

The prevalence of albuminuria (albumin-creatinine ratio ≥30 mg/g) was 30%. Median value for the sum of inorganic and methylated arsenic species was 9.7 (IQR, 5.8-15.6) μg per gram of creatinine. Multivariable-adjusted prevalence ratios of albuminuria (albumin-creatinine ratio ≥30 mg/g) comparing the 3 highest to lowest quartiles of the sum of inorganic and methylated arsenic species were 1.16 (95% CI, 1.00-1.34), 1.24 (95% CI, 1.07-1.43), and 1.55 (95% CI, 1.35-1.78), respectively (P for trend <0.001). The association between urine arsenic and albuminuria was observed across all participant subgroups evaluated and was evident for both micro- and macroalbuminuria.

LIMITATIONS

The cross-sectional design cannot rule out reverse causation.

CONCLUSIONS

Increasing urine arsenic concentrations were cross-sectionally associated with increased albuminuria in a rural US population with a high burden of diabetes and obesity. Prospective epidemiologic and mechanistic evidence is needed to understand the role of arsenic as a kidney disease risk factor.

Occupational exposure profile of Pb, Mn, and Cd in nonferrous Brazilian sanitary alloy foundries

In addition to the primary components of alloys, approximately 5% of the formulation may contain other metals, including lead (Pb), cadmium (Cd), arsenic, manganese (Mn), iron, phosphorus, and nickel. Workers in the foundries are exposed to several compounds; therefore, it is important to assess the levels of injury that may reflect an additive, synergistic, or antagonistic effect caused by these compounds. The mean values of the environmental evaluation of the facilities range from 16.65 to 40.31 µg m−3 for Pb, 0.99 to 1.73 µg m−3 for Cd, and 0.91 to 1.70 µg m−3 for Mn. The mean values of the metal concentrations for furnace, mold, melting, and automatic melting activities range from 15.37 to 19.26 µg m−3 for Pb, 7.07 to 9.14 µg m−3 for Cd, and 8.83 to 16.00 µg m−3 for Mn. Biological samples were divided into two groups: control ( n = 38) and exposed ( n = 45). The obtained data are3.41 ± 3.40 and 14.89 ± 7.82 µg dL−1 for Pb, 0.90 ± 0.80 and 1.91 ± 1.90 µg g−1 creatinine for Cd, and 0.51 ± 0.40 and 3.17 ± 1.93 µg g−1 creatinine for Mn. Statistical analysis showed significant differences ( p < 0.05). Positive linear correlations were established between metal concentrations in the air and the biological matrixes: Pb ( r = 0.68; p < 0.001), Cd ( r = 0.81; p = 0.17), and Mn ( r = 0.12; p < 0.03). Regression analysis showed that professional activities can interfere with element exposure profiles in occupational settings. The analysis in the event of exposure to metals in these companies allowed investigating whether the simultaneous exposure leads to biological damage even if the levels of the compounds are within the exposure limits that are considered to be safe.

Heavy metal toxicity and the environment

Heavy metals are naturally occurring elements that have a high atomic weight and a density at least five times greater than that of water. Their multiple industrial, domestic, agricultural, medical, and technological applications have led to their wide distribution in the environment, raising concerns over their potential effects on human health and the environment. Their toxicity depends on several factors including the dose, route of exposure, and chemical species, as well as the age, gender, genetics, and nutritional status of exposed individuals. Because of their high degree of toxicity, arsenic, cadmium, chromium, lead, and mercury rank among the priority metals that are of public health significance. These metallic elements are considered systemic toxicants that are known to induce multiple organ damage, even at lower levels of exposure. They are also classified as human carcinogens (known or probable) according to the US Environmental Protection Agency and the International Agency for Research on Cancer. This review provides an analysis of their environmental occurrence, production and use, potential for human exposure, and molecular mechanisms of toxicity, genotoxicity, and carcinogenicity.

Delineating the degree of association between biomarkers of arsenic exposure and type-2 diabetes mellitus

Non-carcinogenic effects in low-level (< 100 μgL(-1)) arsenic (As)-impacted populations, such as the development and progression of type-2 diabetes mellitus (T2DM), are often neglected given the primary emphasis of public health authorities on As carcinogenicity. We gathered studies reporting urinary biomarkers of As exposure (U-As) and biomarkers associated with T2DM and its complications (U-T2DM), such as renal damage, oxidation stress, low-grade inflammation, and endothelial damage. Studied U-T2DM biomarkers were: 8-hydroxy-2'deoxyguanosine, N-acetyl-β-d-glucosaminidase, β2-microglobulin, and albumin. Data was expressed as: either arithmetic means and standard deviations, or geometric means and geometric standard deviations, or correlation coefficients of U-As and U-T2DM. Urinary As concentrations were consistently associated with the aforementioned biomarkers of T2DM pathologic complications. Despite the limited selectivity of the selected T2DM biomarkers, a per unit change in As exposure level was reflected in the corresponding T2DM biomarker urinary concentrations. Our systematic review provides new evidence on the role of environmental As exposures influencing the T2DM disease process. Additional epidemiologic studies onto the association between As and T2DM should incorporate both urinary As and T2DM biomarkers, as suggested in this study, in order to evaluate subclinical effects of low-level As exposures.

Kidney dysfunction and cadmium exposure--factors influencing dose-response relationships

Our early toxicological studies showed that metallothionein (MT) is a protein that carries cadmium (Cd) to the kidney, explaining why Cd exposures during long time periods may give rise to kidney dysfunction. This dysfunction is usually considered to be the critical effect, i.e. the adverse effect that occurs at the lowest exposure level. MT also provides intracellular protection against cadmium toxicity. In studies of population groups in cadmium contaminated areas in China, we investigated factors that affected the relationship between internal dose of Cd, as indicated by blood Cd (BCd) or urinary Cd (UCd), and the prevalence of kidney dysfunction. We found dose-response relationships between UCd and the prevalence of increased levels of biomarkers of renal tubular dysfunction (urinary beta-2-microglobulin, B2M, or N-acetyl-beta-d-glucosaminidase - NAG) or urinary albumin (UAlb), a biomarker of glomerular kidney dysfunction. Two years after Cd intake from contaminated rice was diminished, renal tubular dysfunction appeared unchanged or aggravated among those with higher UCd; Another 8 years later, i.e. 10 years after Cd intake was decreased, the prevalence of renal tubular dysfunction was still increased but UAlb had returned to normal. Factors that influenced the dose-response relationships were: (1) time after maximum exposure. (2) Concomitant exposure to other nephrotoxic agents such as inorganic arsenic. (3) Cd induced metallothionein mRNA levels in peripheral blood lymphocytes, used as a biomarker of the ability of each person, to synthesize MT. (4) The occurrence of increased levels in blood plasma of autoantibodies against MT. The two last points further support a role in humans of MT as a protective protein against tissue damage from cadmium and gives support to previous ideas developed partly in experimental systems.

Integrating susceptibility into environmental policy: an analysis of the national ambient air quality standard for lead

Susceptibility to chemical toxins has not been adequately addressed in risk assessment methodologies. As a result, environmental policies may fail to meet their fundamental goal of protecting the public from harm. This study examines how characterization of risk may change when susceptibility is explicitly considered in policy development; in particular we examine the process used by the U.S. Environmental Protection Agency (EPA) to set a National Ambient Air Quality Standard (NAAQS) for lead. To determine a NAAQS, EPA estimated air lead-related decreases in child neurocognitive function through a combination of multiple data elements including concentration-response (CR) functions. In this article, we present alternative scenarios for determining a lead NAAQS using CR functions developed in populations more susceptible to lead toxicity due to socioeconomic disadvantage. The use of CR functions developed in susceptible groups resulted in cognitive decrements greater than original EPA estimates. EPA’s analysis suggested that a standard level of 0.15 µg/m³ would fulfill decision criteria, but by incorporating susceptibility we found that options for the standard could reasonably be extended to lower levels. The use of data developed in susceptible populations would result in the selection of a more protective NAAQS under the same decision framework applied by EPA. Results are used to frame discussion regarding why cumulative risk assessment methodologies are needed to help inform policy development.