Impact of smoking and chewing tobacco on arsenic-induced skin lesions

Molecular and cell phenotype programs in oral epithelial cells directed by co-exposure to arsenic and smokeless tobacco

Chronic exposure to arsenic can lead to various health issues, including cancer. Concerns have been mounting about the enhancement of arsenic toxicity through co-exposure to various prevalent lifestyle habits. Smokeless tobacco (SLT) products are commonly consumed in South Asian countries, where their use frequently co-occurs with exposure to arsenic from contaminated groundwater. To decipher the in vitro molecular and cellular responses to arsenic and/or smokeless tobacco, we performed temporal multi-omics analysis of the transcriptome and DNA methylome remodeling in exposed hTERT-immortalized human normal oral keratinocytes (NOK), as well as arsenic and/or smokeless tobacco genotoxicity and mutagenicity investigations in NOK cells and in human p53 knock-in murine embryonic fibroblasts (Hupki MEF). RNAseq results from acute exposures of NOK cell to arsenic alone and in combination with smokeless tobacco extract revealed upregulation of genes with roles in cell cycle changes, apoptosis and inflammatory responses. This was in keeping with global DNA hypomethylation affecting genes involved in the same processes after chronic treatment. At the phenotypic level, we observed a dose-dependent decrease in NOK cell viability, induction of DNA damage, cell cycle changes and increased apoptosis, with the most pronounced effects observed under arsenic and SLT co-exposure conditions. Live-cell imaging experiments indicated that the DNA damage likely resulted from induction of apoptosis, an observation validated by a lack of exome-wide mutagenesis in response to chronic exposure to arsenic and/or smokeless tobacco. In sum, our integrative omics study provides novel insights into the acute and chronic responses to arsenic and smokeless tobacco (co-)exposure, with both types of responses converging on several key mechanisms associated with cancer hallmark processes. The resulting rich catalogue of molecular programs in oral cells regulated by arsenic and smokeless tobacco (co-)exposure may provide bases for future development of biomarkers for use in molecular cancer epidemiology studies of exposed populations at risk.

Molecular and cell phenotype programs in oral epithelial cells directed by co-exposure to arsenic and smokeless tobacco

Chronic arsenic exposure can lead to various health issues, including cancer. Concerns have been mounting about the enhancement of arsenic toxicity through co-exposure to various prevalent lifestyle habits. Smokeless tobacco products are commonly consumed in South Asian countries, where their use frequently co-occurs with exposure to arsenic from contaminated groundwater. To decipher the in vitro molecular and cellular responses to arsenic and/or smokeless tobacco, we performed temporal multi-omics analysis of the transcriptome and DNA methylome remodelling in exposed hTERT-immortalized human normal oral keratinocytes (NOK), as well as arsenic and/or smokeless tobacco genotoxicity and mutagenicity investigations in NOK cells and in human p53 knock-in murine embryonic fibroblasts (Hupki MEF). RNAseq results from acute exposures to arsenic alone and in combination with smokeless tobacco extract revealed upregulation of genes with roles in cell cycle changes, apoptosis and inflammation responses. This was in keeping with global DNA hypomethylation affecting genes involved in the same processes in response to chronic treatment in NOK cells. At the phenotypic level, we observed a dose-dependent decrease in NOK cell viability, induction of DNA damage, cell cycle changes and increased apoptosis, with the most pronounced effects observed under arsenic and SLT co-exposure conditions. Live-cell imaging experiments indicated that the DNA damage likely resulted from induction of apoptosis, an observation validated by a lack of exome-wide mutagenesis in response to chronic exposure to arsenic and/or smokeless tobacco. In sum, our integrative omics study provides novel insights into the acute and chronic responses to arsenic and smokeless tobacco (co-)exposure, with both types of responses converging on several key mechanisms associated with cancer hallmark processes. The generated rich catalogue of molecular programs in oral cells regulated by arsenic and smokeless tobacco (co-)exposure may provide bases for future development of biomarkers for use in molecular epidemiology studies of exposed populations at risk of developing oral cancer.

Assessing Acute and Chronic Risks of Human Exposure to Arsenic: A Cross-Sectional Study in Ethiopia Employing Body Biomarkers

Background

Arsenic, a widely recognized and highly toxic carcinogen, is regarded as one of the most hazardous metalloids globally. However, the precise assessment of acute and chronic human exposure to arsenic and its contributing factors remains unclear in Ethiopia.

Objective

The primary goal of this study was to assess the levels of acute and chronic arsenic exposure, as well as the contributing factors, using urine and nail biomarkers.

Methods

A community-based analytical cross-sectional study design was employed for this study. Agilent 7900 series inductively coupled plasma mass spectrometry was used to measure the concentrations of arsenic in urine and nail samples. We performed a multiple linear regression analysis to assess the relationships between multiple predictors and outcome variables.

Results

The concentration of arsenic in the urine samples ranged from undetectable (<0.01) to 126.13, with a mean and median concentration of 16.02 and 13.5 μg/L, respectively. However, the mean and median concentration of arsenic in the nails was 1.01, ranging from undetectable (<0.01 μg/g) to 2.54 μg/g. Furthermore, Pearson's correlation coefficient analysis showed a significant positive correlation between arsenic concentrations in urine and nail samples (r = 0.432, P < .001). Also, a positive correlation was observed between urinary (r = 0.21, P = .007) and nail (r = 0.14, P = .044) arsenic concentrations and the arsenic concentration in groundwater. Groundwater sources and smoking cigarettes were significantly associated with acute arsenic exposure. In contrast, groundwater sources, cigarette smoking, and the frequency of showers were significantly associated with chronic arsenic exposure.

Conclusions

The study's findings unveiled the widespread occurrence of both acute and chronic arsenic exposure in the study area. Consequently, it is crucial to prioritize the residents in the study area and take further measures to prevent both acute and chronic arsenic exposure.

Prevalence of arsenic-induced skin lesions and associated factors in Ethiopia: Community-based study

The study aimed to assess the prevalence of arsenic-induced skin lesions and associated factors among the population in the Adami Tulu Jido Kombolcha district, Ethiopia. A community-based cross-sectional study design was employed among 403 participants from June 02-20, 2022. A two-stage cluster sampling method was conducted to select study subjects. A pretested structured and semi-structured interview questionnaire and observation using a WHO flow chart were used for data collection. Data analysis was performed using SPSS version 24 statistical software for Windows. A multivariable binary logistic regression model was applied to examine the relationship between predictor variables and an outcome variable. The degrees of association between outcomes and predictor variables were assessed using ORs and 95% CIs, and P-values < 0.05 were considered significant. The prevalence of arsenic-induced skin lesions (arsenicosis) in the study area was 2.2% [95% CI: 1.0-3.7]. The most common arsenic-induced manifestation was keratosis (55.6%), followed by hyperpigmentation (33.3%) and hyperkeratosis (11.1%). Consumption of well water, smoking cigarettes, and chewing khat were significantly associated with arsenic-induced skin lesions. Therefore, the findings of this study should trigger further research on arsenic exposure and health risks.

Arsenic metabolism, diabetes prevalence, and insulin resistance among Mexican Americans: A mendelian randomization approach

Background

Differences in arsenic metabolism capacity may influence risk for type 2 diabetes, but the mechanistic drivers are unclear. We evaluated the associations between arsenic metabolism with overall diabetes prevalence and with static and dynamic measures of insulin resistance among Mexican Americans living in Starr County, Texas.

Methods

We utilized data from cross-sectional studies conducted in Starr County, Texas, from 2010-2014. A Mendelian randomization approach was utilized to evaluate the associations between arsenic metabolism and type 2 diabetes prevalence using the intronic variant in the arsenic methylating gene, rs9527, as the instrumental variable for arsenic metabolism. To further assess mechanisms for diabetes pathogenesis, proportions of the urinary arsenic metabolites were employed to assess the association between arsenic metabolism and insulin resistance among participants without diabetes. Urinary biomarkers of arsenic metabolites were modeled as individual proportions of the total. Arsenic metabolism was evaluated both with a static outcome of insulin resistance, homeostatic measure of assessment (HOMA-IR), and a dynamic measure of insulin sensitivity, Matsuda Index.

Results

Among 475 Mexican American participants from Starr County, higher metabolism capacity for arsenic is associated with higher diabetes prevalence driven by worse insulin resistance. Presence of the minor T allele of rs9527 is independently associated with an increase in the proportion of monomethylated arsenic (MMA%) and is associated with an odds ratio of 0.50 (95% CI: 0.24, 0.90) for type 2 diabetes. This association was conserved after potential covariate adjustment. Furthermore, among participants without type 2 diabetes, the highest quartile of MMA% was associated with 22% (95% CI: -33.5%, -9.07%) lower HOMA-IR and 56% (95% CI: 28.3%, 91.3%) higher Matsuda Index for insulin sensitivity.

Conclusions

Arsenic metabolism capacity, indicated by a lower proportion of monomethylated arsenic, is associated with increased diabetes prevalence driven by an insulin resistant phenotype among Mexican Americans living in Starr County, Texas.

Changes in arsenic accumulation and metabolic capacity after environmental management measures in mining area

Due to the public health concern of arsenic, environmental management measures in mining areas had been implemented. To assess the effect of environmental management measures in the mining area comprehensively, arsenic accumulation in the urine, hair, nails, and urinary metabolites of residents in a realgar mining area in Hunan province, China were investigated in 2019, and the changes in arsenic levels in the biomarkers during 2012-2019 were tracked. The importance of confounding factors (age, sex, occupation, residence, clinical history, vegetable source, cooking fuel, smoking, alcohol consumption, BMI) was analyzed using the Boruta algorithm. After the implementation of environmental management measures (including ceasing mining and smelting activities, building landfills, adjusting the planting structure, and soil restoration), urine, hair, and nail arsenic concentration decreased drastically but were still excessive. Arsenic accumulation was highest in older male miners who were long settled in the mining area and consumed homegrown vegetables. The only factor for changes in urinary arsenic levels was the cooking fuel type; residents using wood as cooking fuel experienced sustained arsenic exposure. Occupation and sex were important for determining arsenic changes in the hair and nails. Short-term arsenic accumulation in urine was affected by arsenic exposure, while long-term accumulation in hair and nails by arsenic metabolic capacity. The percentage of urinary arsenic metabolism and arsenic methylation indices of the participants in the mining area were within the normal range (%iAs: 10-30 %, %MMA: 10-20 %, % DMA: 60-80 %); samples indicated worse metabolic capacity than the reference population. The arsenic metabolic capacity of male miners was relatively weak, probably aggravated by alcohol drinking and smoking. Without soil remediation, arsenic exposure will continue. Homegrown vegetables and biomass fuels should be abandoned; reduced cigarette and alcohol consumption is recommended. Urinary arsenic would be more proper for assessing environmental remediation in mining areas.

Use of study-specific MOE-like estimates to prioritize health effects from chemical exposure for analysis in human health assessments

There are unique challenges in estimating dose-response with chemicals that are associated with multiple health outcomes and numerous studies. Some studies are more suitable than others for quantitative dose-response analyses. For such chemicals, an efficient method of screening studies and endpoints to identify suitable studies and potentially important health effects for dose-response modeling is valuable. Using inorganic arsenic as a test case, we developed a tiered approach that involves estimating study-specific margin of exposure (MOE)-like unitless ratios for two hypothetical scenarios. These study-specific unitless ratios are derived by dividing the exposure estimated to result in a 20% increase in relative risk over the background exposure (RRE20) by the background exposure, as estimated in two different ways. In our case study illustration, separate study-specific ratios are derived using estimates of United States population background exposure (RRB-US) and the mean study population reference group background exposure (RRB-SP). Systematic review methods were used to identify and evaluate epidemiologic studies, which were categorized based on study design (case-control, cohort, cross-sectional), various study quality criteria specific to dose-response analysis (number of dose groups, exposure ascertainment, exposure uncertainty), and availability of necessary dose-response data. Both case-control and cohort studies were included in the RRB analysis. The RRE20 estimates were derived by modeling effective counts of cases and controls estimated from study-reported adjusted odds ratios and relative risks. Using a broad (but not necessarily comprehensive) set of epidemiologic studies of multiple health outcomes selected for the purposes of illustrating the RRB approach, this test case analysis would suggest that diseases of the circulatory system, bladder cancer, and lung cancer may be arsenic health outcomes that warrant further analysis. This is suggested by the number of datasets from adequate dose-response studies demonstrating an effect with RRBs close to 1 (i.e., RRE20 values close to estimated background arsenic exposure levels).

Recent Advances in Arsenic Research: Significance of Differential Susceptibility and Sustainable Strategies for Mitigation

Arsenic contamination in drinking water and associated adverse outcomes are one of the major health issues in more than 50 countries worldwide. The scenario is getting even more detrimental with increasing number of affected people and newer sites reported from all over the world. Apart from drinking water, the presence of arsenic has been found in various other dietary sources. Chronic arsenic toxicity affects multiple physiological systems and may cause malignancies leading to death. Exposed individuals, residing in the same area, developed differential dermatological lesion phenotypes and varied susceptibility toward various other arsenic-induced disease risk, even after consuming equivalent amount of arsenic from the similar source, over the same duration of time. Researches so far indicate that differential susceptibility plays an important role in arsenic-induced disease manifestation. In this comprehensive review, we have identified major population-based studies of the last 20 years, indicating possible causes of differential susceptibility emphasizing arsenic methylation capacity, variation in host genome (single nucleotide polymorphism), and individual epigenetic pattern (DNA methylation, histone modification, and miRNA expression). Holistic multidisciplinary strategies need to be implemented with few sustainable yet cost-effective solutions like alternative water source, treatment of arsenic-contaminated water, new adaptations in irrigation system, simple modifications in cooking strategy, and dietary supplementations to combat this menace. Our review focuses on the present perspectives of arsenic research with special emphasis on the probable causes of differential susceptibility toward chronic arsenic toxicity and sustainable remediation strategies.

Assessment of carcinogenic and toxic substances in 'Insunko' herb

There has emerged a herb in Zambia called 'insunko' which has unknown chemical composition. The use of 'insunko' herb with unknown chemical composition has brought mixed feelings among many Zambians. This study, therefore, aimed to assess the toxic and carcinogenic substances in'insunko' herb. 'Insunko' herb was purchased from Chipata, Lusaka, Mpika, Mwense, Kitwe, and Solwezi. 5 samples were collected from each of these districts and were thoroughly mixed to give 6 consolidated samples (n = 6). Nicotine and, nitrosamines were analysed using UV spectrometer lambda 35 Perkin Elmer while trace metals were analysed using ICP-MS Inductively Coupled Plasma Mass Spectroscopy (Agilent Technologies, Santa Clara, CA, USA). Nicotine, nitrosamines, and trace metals were detected in high concentrations. The concentrations ranged from 3.87 to 9.83 mg/kg for nitrosamines and 10.94-34.01 mg/kg for nicotine. Hazard Indexes for arsenic, cadmium, chromium, manganese, and copper were greater than one (HI > 1). 'Insunko' herb is a potentially toxic and carcinogenic substance because it contains toxic and carcinogenic constituents in high concentrations. These toxic and carcinogenic constituents have been confirmed to cause gastrointestinal disorders, cancers, degenerative, cardiovascular, hematopoietic, neurologic and cognitive problems as well as male infertility.

Recent Advances in Arsenic Research: Significance of Differential Susceptibility and Sustainable Strategies for Mitigation

Arsenic contamination in drinking water and associated adverse outcomes are one of the major health issues in more than 50 countries worldwide. The scenario is getting even more detrimental with increasing number of affected people and newer sites reported from all over the world. Apart from drinking water, the presence of arsenic has been found in various other dietary sources. Chronic arsenic toxicity affects multiple physiological systems and may cause malignancies leading to death. Exposed individuals, residing in the same area, developed differential dermatological lesion phenotypes and varied susceptibility toward various other arsenic-induced disease risk, even after consuming equivalent amount of arsenic from the similar source, over the same duration of time. Researches so far indicate that differential susceptibility plays an important role in arsenic-induced disease manifestation. In this comprehensive review, we have identified major population-based studies of the last 20 years, indicating possible causes of differential susceptibility emphasizing arsenic methylation capacity, variation in host genome (single nucleotide polymorphism), and individual epigenetic pattern (DNA methylation, histone modification, and miRNA expression). Holistic multidisciplinary strategies need to be implemented with few sustainable yet cost-effective solutions like alternative water source, treatment of arsenic-contaminated water, new adaptations in irrigation system, simple modifications in cooking strategy, and dietary supplementations to combat this menace. Our review focuses on the present perspectives of arsenic research with special emphasis on the probable causes of differential susceptibility toward chronic arsenic toxicity and sustainable remediation strategies.

Rice Intake and Emerging Concerns on Arsenic in Rice: a Review of the Human Evidence and Methodologic Challenges

PURPOSE OF REVIEW

Rice is a major staple food worldwide and a dietary source of arsenic. We therefore summarized the state of the epidemiologic evidence on whether rice consumption relates to health outcomes associated with arsenic exposure.

RECENT FINDINGS

While epidemiologic studies have reported that higher rice consumption may increase the risk of certain chronic conditions, i.e., type 2 diabetes, most did not consider specific constituents of rice or other sources of arsenic exposure. Studies that examined rice intake stratified by water concentrations of arsenic found evidence of increasing trends in cardiovascular disease risk, skin lesions, and squamous cell skin cancers and bladder cancer associated with higher rice consumption. Further studies are needed to understand the health impacts of arsenic exposure from rice consumption taking into account all sources of rice intake and potential confounding by other dietary constituents or contaminants and arsenic exposure from sources such as water.

Alterations of arsenic levels in arsenicosis residents and awareness of its risk factors: A population-based 20-year follow-up study in a unique coal-borne arsenicosis County in Guizhou, China

BACKGROUND

Currently, most arsenic (As) studies in populations are concerned with water-borne arsenicosis. However, residents in Xingren County of Guizhou Province, Southwest of China, represent a unique case of arsenicosis which is related to indoor combustion of high As-containing coal. This study aimed to assess the alterations of As levels and its risk factors in coal-borne arsenicosis residents during the past 20 years.

METHODS

Four follow-up investigations in Xingren County were selected from the year 1998 to 2017, a total of 245, 272, 584, and 309 residents were involved in the four investigations, respectively. Local external environmental medium (coal, soil, water, air, rice, corn and chili peppers) and biological samples (urine, hair) were collected at each time of investigation for total As analysis. Sociodemographics and lifestyles variables were extracted from the questionnaire investigation. Both univariate and multivariate unconditional logistic regression models were performed to analyze the variation of risk factors for coal-borne arsenicosis.

RESULTS

A substantial reduction of total As levels was observed both in external environmental medium and biological samples in the unique coal-borne arsenicosis region, especially since the year 2006. In addition, age, duration of consuming high As-containing coal and smoking status were found to be the most significant risk factors for coal-borne arsenicosis during the past 20 years by both two different logistic regression models. Room ventilation and grain drying modes were no longer to be risk factors since 1998 survey. Annual household income had always been an important protective factor for coal-borne arsenicosis in recent 20 years by both two different logistic regression models. Grain storage modes had become significant protective factor in 2014 and 2017 survey. A certain correlation between sex, education and coal-borne arsenicosis was observed by univariate logistic regression model but no clear links were found by multivariate logistic regression model.

CONCLUSIONS

Considerable efforts to blocking As exposure from burning coal and As contaminated foods in this region are observed over the study period. Further practical health education programs may need to target individuals with long-term of As exposure, lower socioeconomic status and smoking in order to better prevent and control the occurrence and development of coal-borne arsenicosis.

Elevated arsenic exposure and efficient arsenic metabolism in indigenous women around Lake Poopó, Bolivia

Elevated concentrations of inorganic arsenic, one of the most potent environmental toxicants and carcinogens, have been detected in well water around Lake Poopó, Bolivia. This study aimed to assess human exposure to arsenic in villages around Lake Poopó, and also to elucidate whether the metabolism and detoxification of arsenic in this population is as efficient as previously indicated in other Andean areas. We recruited 201 women from 10 villages around Lake Poopó. Arsenic exposure was determined as the sum concentration of arsenic metabolites (inorganic arsenic; monomethylarsonic acid, MMA; and dimethylarsinic acid, DMA) in urine (U-As), measured by HPLC-HG-ICP-MS. Efficiency of arsenic metabolism was assessed by the relative fractions of the urinary metabolites. The women had a wide variation in U-As (range 12-407 μg/L, median 65 μg/L) and a markedly efficient metabolism of arsenic with low %MMA (median 7.7%, range: 2.2-18%) and high %DMA (80%, range: 54-91%) in urine. In multivariable-adjusted linear regression models, ethnicity (Aymara-Quechua vs. Uru), body weight, fish consumption and tobacco smoking were associated with urinary arsenic metabolite fractions. On average, the Uru women had 2.5 lower % (percentage unit) iAs, 2.2 lower %MMA and 4.7 higher %DMA compared with the Aymara-Quechua women. Our study identified several factors that may predict these women's arsenic methylation capacity, particularly ethnicity. Further studies should focus on mechanisms underlying these differences in arsenic metabolism efficiency, and its importance for the risk of arsenic-related health effects.

State of the science review of the health effects of inorganic arsenic: Perspectives for future research

Human exposure to inorganic arsenic (iAs) is a global health issue. Although there is strong evidence for iAs-induced toxicity at higher levels of exposure, many epidemiological studies evaluating its effects at low exposure levels have reported mixed results. We comprehensively reviewed the literature and evaluated the scientific knowledge on human exposure to arsenic, mechanisms of action, systemic and carcinogenic effects, risk characterization, and regulatory guidelines. We identified areas where additional research is needed. These priority areas include: (1) further development of animal models of iAs carcinogenicity to identify molecular events involved in iAs carcinogenicity; (2) characterization of underlying mechanisms of iAs toxicity; (3) assessment of gender-specific susceptibilities and other factors that modulate arsenic metabolism; (4) sufficiently powered epidemiological studies to ascertain relationship between iAs exposure and reproductive/developmental effects; (5) evaluation of genetic/epigenetic determinants of iAs effects in children; and (6) epidemiological studies of people chronically exposed to low iAs concentrations.

Urinary metals and metal mixtures in Bangladesh: Exploring environmental sources in the Health Effects of Arsenic Longitudinal Study (HEALS)

INTRODUCTION

Environmental exposure to toxic metals and metalloids is pervasive and occurs from multiple sources. The Health Effects of Arsenic Longitudinal Study (HEALS) is an ongoing prospective study predominantly focused on understanding health effects associated with arsenic exposure from drinking water. The goal of this project was to measure a suite of elements in urine to better understand potential exposure patterns and to identify common environmental sources of exposure among this semi-rural Bangladeshi population.

METHODS

In a random sample of 199 adult HEALS participants (50% female), the concentrations of 15 urinary elements (As, Ba, Cd, Co, Cs, Cu, Mn, Mo, Ni, Pb, Se, Sr, Tl, W, Zn) were assessed by Inductively-Coupled Plasma Mass Spectrometry (ICP-MS) to assess commonalities with sociodemographic characteristics and potential sources of exposure. We used principal component analysis (PCA) with varimax normalized rotations, and hierarchical cluster analysis (CA), using Ward's method with Euclidean distances, to evaluate these relationships.

RESULTS

PCA and CA showed similar patterns, suggesting 6 principal components (PC) and 5 clusters: 1)PC: Sr-Ni-Cs/ CA: Sr-Ni-Co; 2) Pb-Tl/Pb-Tl-Se-Cs; 3) As-Mo-W/As-Mo-W; 4) Ba-Mn/Ba-Mn; 5) Cu-Zn/Cu-Zn-Cd; and 6) Cd. There was a strong significant association between the As-Mo-W PC/cluster and water arsenic levels (p < 0.001) and between the Cd PC and betel nut use (p = 0.003). The Sr-Ni-Cs PC was not related to any of the socio-demographic characteristics investigated, including smoking status and occupation. The first PC, Sr-Ni-Cs, explained 21% of the variability; the third PC, As-Mo-W, explained 12.5% of the variability; and the sixth PC, Cd, explained 10% of the variability. Day laborers appeared to have the highest exposure.

CONCLUSIONS

Groundwater and betel nut use are likely important sources of metal and metalloid exposure in this population. These findings will guide future exposure assessment research in Bangladesh and future epidemiologic research investigating the degree to which metal mixtures play a role in disease development.

A cross-sectional study of general cognitive abilities among Uruguayan school children with low-level arsenic exposure, potential effect modification by methylation capacity and dietary folate

BACKGROUND

Few studies have evaluated the association between low-level arsenic (As) exposure and cognitive performance among children.

OBJECTIVES

In this cross-sectional study, we assessed the association between low-level As exposure and cognitive performance among 5-8 year-old children in Montevideo, and tested effect modification by As methylation capacity and children's dietary folate intake.

METHODS

We measured total urinary As (UAs) concentrations and the proportion of monomethylarsonic acid (MMA) in the urine of 328 children. Seven subtests of the standardized Woodcock-Muñoz cognitive battery were used to assess cognitive performance, from which, the general intellectual abilities (GIA) score was derived. Total folate intake was estimated from two 24-h dietary recalls. Linear regression analyses were performed. Effect modification was assessed by stratifying at the median %MMA value and tertiles of total folate intake calculated as micrograms (µg) of dietary folate equivalents (dfe).

RESULTS

The median UAs was 11.9 µg/l (range = 1.4-93.9), mean folate intake was 337.4 (SD = 123.3) µg dfe, and median %MMA was 9.42 (range = 2.6-24.8). There was no association between UAs and cognitive abilities, and no consistent effect modification by %MMA. UAs was associated inversely with concept formation, and positively with cognitive efficiency and numbers reversed subtest in the lowest folate intake tertile; UAs was also positively associated with sound integration in the second tertile and concept formation in the highest tertile of folate intake. There was no consistent pattern of effect modification by %MMA or folate intake.

CONCLUSION

There was no association between low-level As exposure and general cognitive abilities.

Effect of nutritional status on arsenic and smokeless tobacco induced genotoxicity, sperm abnormality and oxidative stress in mice in vivo

BACKGROUND

Recently, high concentrations of arsenic have been documented in ground waters of Southern Assam, India. Indiscriminate smokeless tobacco consumption is a common practice in this region. Correlation between nutritional status and arsenic and smokeless tobacco-induced health effects has not been taken up in humans or other test systems.

METHODS

Mice were divided into groups based on protein (casein) content in the diet: High protein (40%), optimum protein (20%), and low protein (5%). Simultaneous chronic exposure (90 days) to arsenic and smokeless tobacco (sadagura) orally was given to evaluate the extent of the cytological and genotoxicological damage. Micronucleus assay and Comet assay of the femur bone marrow cells were conducted. Germ cell toxicity was evaluated by recording the sperm head abnormalities and total sperm count. Cell cycle analysis was performed in femur bone marrow cells using flow cytometer. Hepatic, renal, and intestinal tissues were analyzed for various oxidative stress evaluations. Histological examination of liver and kidney was performed.

RESULTS

Notably, high protein diet groups had lower arsenic and sadagura induced genotoxicity, germ cell abnormalities and oxidative stress as compared to optimum protein and low protein diet counterparts.

CONCLUSION

Our study indicates that sufficient levels of dietary protein appear to reduce the long-term arsenic and smokeless tobacco-induced toxicity in mice test system, as compared to lower or deficient amount of protein in the diet. This observation has implications and invites further studies especially epidemiological studies in the human population exposed to arsenic in South East Asian countries. Environ. Mol. Mutagen. 59:386-400, 2018. © 2018 Wiley Periodicals, Inc.

Human health risks and socio-economic perspectives of arsenic exposure in Bangladesh: A scoping review

Arsenic contamination of drinking water, which can occur naturally or because of human activities such as mining, is the single most important public health issue in Bangladesh. Fifty out of the 64 districts in the country have arsenic concentration of groundwater exceeding 50µgL-1, the Bangladeshi threshold, affecting 35-77 million people or 21-48% of the total population. Chronic arsenic exposure through drinking water and other dietary sources is an important public health issue worldwide affecting hundreds of millions of people. Consequently, arsenic poisoning has attracted the attention of researchers and has been profiled extensively in the literature. Most of the literature has focused on characterising arsenic poisoning and factors associated with it. However, studies examining the socio-economic aspects of chronic exposure of arsenic through either drinking water or foods remain underexplored. The objectives of this paper are (i) to review arsenic exposure pathways to humans; (ii) to summarise public health impacts of chronic arsenic exposure; and (iii) to examine socio-economic implications and consequences of arsenicosis with a focus on Bangladesh. This scoping review evaluates the contributions of different exposure pathways by analysing arsenic concentrations in dietary and non-dietary sources. The socio-economic consequences of arsenicosis disease in Bangladesh are discussed in this review by considering food habits, nutritional status, socio-economic conditions, and socio-cultural behaviours of the people of the country. The pathways of arsenic exposure in Bangladesh include drinking water, various plant foods and non-dietary sources such as soil. Arsenic affected people are often abandoned by the society, lose their jobs and get divorced and are forced to live a sub-standard life. The fragile public health system in Bangladesh has been burdened by the management of thousands of arsenicosis victims in Bangladesh.

Associations between Methylated Metabolites of Arsenic and Selenium in Urine of Pregnant Bangladeshi Women and Interactions between the Main Genes Involved

BACKGROUND

It has been proposed that interactions between selenium and arsenic in the body may affect their kinetics and toxicity. However, it is unknown how the elements influence each other in humans.

OBJECTIVES

We aimed to investigate potential interactions in the methylation of selenium and arsenic.

METHODS

Urinary selenium (U-Se) and arsenic (U-As) were measured using inductively coupled plasma mass spectrometry (ICPMS) in samples collected from pregnant women (n=226) in rural Bangladesh at gestational weeks (GW) 8, 14, 19, and 30. Urinary concentrations of trimethyl selenonium ion (TMSe) were measured by HPLC-vapor generation-ICPMS, as were inorganic arsenic (iAs), methylarsonic acid (MMA), and dimethylarsinic acid (DMA). Methylation efficiency was assessed based on relative amounts (%) of arsenic and selenium metabolites in urine. Genotyping for the main arsenite and selenium methyltransferases, AS3MT and INMT, was performed using TaqMan probes or Sequenom.

RESULTS

Multivariable-adjusted linear regression analyses indicated that %TMSe (at GW8) was positively associated with %MMA (β=1.3, 95% CI: 0.56, 2.0) and U-As, and inversely associated with %DMA and U-Se in producers of TMSe (INMT rs6970396 AG+AA, n=74), who had a wide range of urinary TMSe (12-42%). Also, %TMSe decreased in parallel to %MMA during pregnancy, especially in the first trimester (-0.58 %TMSe per gestational week). We found a gene-gene interaction for %MMA (p-interaction=0.076 for haplotype 1). In analysis stratified by INMT genotype, the association between %MMA and both AS3MT haplotypes 1 and 3 was stronger in women with the INMT GG (TMSe nonproducers, 5th-95th percentile: 0.2-2%TMSe) vs. AG+AA genotype.

CONCLUSIONS

Our findings for Bangladeshi women suggest a positive association between urinary %MMA and %TMSe. Genes involved in the methylation of selenium and arsenic may interact on associations with urinary %MMA. https://doi.org/10.1289/EHP1912.

Interactive Influence of N6AMT1 and As3MT Genetic Variations on Arsenic Metabolism in the Population of Inner Mongolia, China

Chronic arsenic exposure via drinking water has become a worldwide public health concern. In humans, inorganic arsenic (iAs) is metabolized to monomethylarsonic acid (MMA) and dimethylarsinic acid (DMA) mainly mediated by arsenic (+3 oxidation state) methyltransferase (As3MT). We reported recently that N-6 adenine-specific DNA methyltransferase 1 (N6AMT1) was involved in arsenic metabolism, and examined its interactive effect with As3MT on arsenic metabolism in vitro To further evaluate the interactive effect of N6AMT1 and As3MT on arsenic biomethylation in humans, we conducted a human population-based study including 289 subjects living in rural villages in Inner Mongolia, China, and assessed their urinary arsenic metabolites profiles in relation to genetic polymorphisms and haplotypes of N6AMT1 and As3MT Five N6AMT1 single nucleotide polymorphisms (SNPs; rs1003671, rs7282257, rs2065266, rs2738966, rs2248501) and the N6AMT1 haplotype 2_GGCCAT were significantly associated with the percentage of iAs (% iAs) in urine (e.g., for rs7282257, mean was 9.62% for TT, 6.73% for AA). Rs1003671 was also in a significant relationship with urinary MMA and DMA (the mean of %MMA was 24.95% for GA, 31.69% for GG; the mean of % DMA was 69.21% for GA, 59.82% for GG). The combined effect of N6AMT1 haplotype 2_GGCCAT and As3MT haplotype 2_GCAC showed consistence with the additive significance of each haplotype on % iAs: the mean was 5.47% and 9.36% for carriers with both and null haplotypes, respectively. Overall, we showed that N6AMT1 genetic polymorphisms were associated with arsenic biomethylation in the Chinese population, and its interaction with As3MT was observed in specific haplotype combinations.

Arsenic Metabolism in Children Differs From That in Adults

Arsenic toxicity in adults is associated with methylation efficiency, influenced by factors such as gender, genetics, and nutrition. The aim of this study was to evaluate influencing factors for arsenic metabolism in children. For 488 children (9 years), whose mothers participated in a study on arsenic exposure during pregnancy (nested into the MINIMat trial) in rural Bangladesh, we measured urinary concentrations of inorganic arsenic (iAs) and its metabolites methylarsonic acid (MMA) and dimethylarsinic acid (DMA) by HPLC-HG-ICPMS. Methylation efficiency was assessed by relative amounts (%) of the metabolites. We evaluated the impact of factors such as maternal urinary metabolite pattern, arsenic exposure, gender, socioeconomic status, season of sampling, and nutritional factors, including erythrocyte selenium (Ery-Se), and plasma folate and vitamin B12.

Children had higher %DMA and lower %iAs in urine compared to their mothers, unrelated to their lower exposure [median urinary arsenic (U-As) 53 vs 78 µg/l]. Surprisingly, selenium status (Ery-Se) was strongly associated with children’s arsenic methylation; an increase in Ery-Se from the 5–95th percentile was associated with: +1.8 percentage points (pp) for %iAs (P  =  .001), +1.4 pp for %MMA (P  =  .003), and −3.2 pp for %DMA (P  <  .001). Despite this, Ery-Se was positively associated with U-As (5–95th percentile: +41 µg/l, P  =  .026). As expected, plasma folate was inversely associated with %iAs (5–95th percentile: −1.9 pp, P  =  .001) and positively associated with %DMA (5–95th percentile: +2.2 pp, P  =  .008). Children methylated arsenic more efficiently than their mothers. Also influencing factors, mainly selenium and folate, differed. This warrants further research.

Arsenic and smokeless tobacco induce genotoxicity, sperm abnormality as well as oxidative stress in mice in vivo

BACKGROUND

Arsenic, a naturally occurring metalloid is a well-known water contaminant which causes a wide range of serious adverse health effects including cancer upon long-term exposure. Recent studies have shown high arsenic contamination in the ground water of North Eastern states of India including Southern Assam. Smokeless tobacco consumption locally known as "sadagura" is one of the most prevalent life style habit in southern Assam. The present study was undertaken in mice test system in vivo. Mice were exposed to smokeless tobacco (5 mg/kg body weight /day) and sodium arsenite (0.2 mg/kg body weight /day, 2 mg/kg body weight/day) independently and in combination for 90 days.

RESULTS

The results were compared with groups with only sodium arsenite exposure and groups which were exposed to only smokeless tobacco extract. Genotoxicity was evaluated by studying the incidence of micronucleated polychromatic erythrocytes from bone marrow. Both the tested doses of sodium arsenite induced statistically significant micronucleated polychromatic erythrocytes as compared to control group, however, sodium arsenite and smokeless tobacco extract could not increase the incidence of micronucleated polychromatic erythrocytes as compared to their individual counterparts when treated in combination in mice test system. Germ cell toxicity was evaluated by recording the sperm head abnormalities and total sperm count. Combined treatment of sodium arsenite and smokeless tobacco extract in lower dose induced a significant increase in sperm head abnormality as compared to only sodium arsenite and smokeless tobacco extract. Liver, kidney and intestine tissues were analyzed for various oxidative stress evaluations such as lipid peroxidation (MDA), Glutathione (GSH) and superoxide dismutase (SOD) assay. Sodium arsenite in combination with smokeless tobacco extract show higher genotoxic and germ cell toxic effects as compared to control but not when compared to their individual counterparts.

CONCLUSION

Impairment of the sperm head morphology by sodium arsenite and smokeless tobacco extract alone and in combination with lower dose of sodium arsenite could be oxidative stress mediated effects. Besides, combination treatment of both the agents may not produce additive effects related to micronucleated polychromatic erythrocytes induction and decline of total sperm count.

Evaluation of genetic damage in tobacco and arsenic exposed population of Southern Assam, India using buccal cytome assay and comet assay

Ground water is the principal source of drinking water in Assam. Ground water contamination of arsenic in drinking water is a great concern for human health and considered as a human carcinogen. The present cytogenetic biomonitoring study was undertaken to investigate the genotoxic effects associated with people of southern Assam consuming arsenic contaminated water and chewing tobacco. Employing the buccal cytome assay, exfoliated cells were analyzed in 138 individuals of age range 22-42 years and divided into four groups. Group I (n=54) are participants residing in localities where ground water contains arsenic concentration below the permissible limit (<10μg/l) and without any tobacco chewing history. Group II (n=32) participants from the same area but they are tobacco chewers. Group III (n=24) participants from localities where significantly high arsenic contamination in ground water were observed. Whereas the Group IV (n=28) consists of participants from the arsenic contaminated area and also tobacco chewers. Body mass index (BMI) in all the groups are found to be nearly same and in normal range. Statistically significant (P<0.001) increase in genotoxic, cell death parameters and cell proliferation biomarkers were observed in the Group IV compared to other groups. In the comet assay, percent of tail DNA gradually increases among the groups and has statistical significance. Spearman correlation revealed strong positive correlation between the arsenic exposed peoples and the binucleated cells (r=0.4763; P<0.001). Amount of chewing tobacco had significant positive correlation with micronucleus frequency (r=0.268; P<0.05) and karyolitic cells (r=0.217; P<0.05) and also in the percentage of tail DNA (r=0.5532, P<0.001). A statistically significant increase in glucose content and decrease in hemoglobin content as well as acetylcholine esterase in the blood of exposed individuals was observed. Our preliminary study indicate that population exposed to arsenic through drinking water may become more susceptible towards chewing tobacco induced nuclear damage as evaluated by buccal cytome assay and comet assay.

Correlation of Arsenic Levels in Smokeless Tobacco Products and Biological Samples of Oral Cancer Patients and Control Consumers

It has been extensively reported that chewing of smokeless tobacco (SLT) can lead to cancers of oral cavity. In present study, the relationship between arsenic (As) exposure via chewing/inhaling different SLT products in oral cancer patients have or/not consumed SLT products was studied. The As in different types of SLT products (gutkha, mainpuri, and snuff) and biological (scalp hair and blood) samples of different types of oral cancer patients and controls were analyzed. Both controls and oral cancer patients have same age group (ranged 30-60 years), socio-economic status, localities, and dietary habits. The concentrations of As in SLT products and biological samples were measured by electrothermal atomic absorption spectrophotometer after microwave-assisted acid digestion. The validity and accuracy of the methodology were checked by certified reference materials. The resulted data of present study indicates that the concentration of As was significantly higher in scalp hair and blood samples of oral cancer patients than those of controls (p<0.001). It was also observed that the values of As were two- to threefolds higher in biological samples of controls subjects, consuming SLT products as compared to those have none of these habits (p>0.01). The intake of As via consuming different SLT may have synergistic effects, in addition to other risk factors associated with oral cancer.

Arsenic and nicotine co-exposure lead to some synergistic effects on oxidative stress and apoptotic markers in young rat blood, liver, kidneys and brain

Arsenic and nicotine exposure has been a major health concern globally. Individually both these toxicants increase the risk to various diseases including cancers. However, limited information exists on the co-exposure. In this study, we evaluate the effects of their individual and combined exposure and if co-exposure to these toxicants might have a synergism or antagonism. Male rats were exposed to a very low dose of arsenic (25 ppm in drinking water) or nicotine (0.25 mg/kg, sub-cutaneously) for a period of 5 months and post exposure various biochemical variables indicative of oxidative stress and apoptosis evaluated. Almost all glutathione linked enzymes showed marked alteration in individual as well as co-exposure treated groups. While serum creatinine and apoptosis indicator, lactate dehydrogenase (LDH) were significantly increased in both treatments, an additive effect was noted in co-exposure group. A similar trend was also seen in brain and liver but not in kidneys. Gene expression studies showed marked reduction in catalase, Cu-Zn SOD, GST, there was a significant up regulation in Bax, caspase 3 in various tissues along with urinary 8-OHdG levels, indicative of DNA damage and apoptosis. Interestingly, a decrease in liver arsenic concentration was noted in co-exposed group compared to arsenic alone exposed group. In conclusion, the present study suggests that arsenic and nicotine exhibited significant toxicity during individual exposure whereas co-exposure to these toxins showed variable conditions (indicative of both synergism and antagonism) in male rats.

Human health risk assessment from arsenic exposures in Bangladesh

High arsenic exposures, prevalent through dietary and non-dietary sources in Bangladesh, present a major health risk to the public. A quantitative human health risk assessment is described as a result of arsenic exposure through food and water intake, tea intake, accidental soil ingestion, and chewing of betel quid, while people meet their desirable dietary intake requirements throughout their lifetime. In evaluating the contribution of each intake pathway to average daily arsenic intake, the results show that food and water intake combined, makes up approximately 98% of the daily arsenic intake with the balance contributed to by intake pathways such as tea consumption, soil ingestion, and quid consumption. Under an exposure scenario where arsenic concentration in water is at the WHO guideline (0.01 mg/L), food intake is the major arsenic intake pathway ranging from 67% to 80% of the average daily arsenic intake. However, the contribution from food drops to a range of 29% to 45% for an exposure scenario where arsenic in water is at the Bangladesh standard (0.05 mg/L). The lifetime excess risk of cancer occurrence from chronic arsenic exposure, considering a population of 160 million people, based on an exposure scenario with 85 million people at the WHO guideline value and 75 million people at the Bangladesh standard, and assuming that 35 million people are associated with a heavy activity level, is estimated as 1.15 million cases.

A critical review of arsenic exposures for Bangladeshi adults

Groundwater, the most important source of water for drinking, cooking, and irrigation in Bangladesh, is a significant contributor to the daily human intake of arsenic. Other arsenic intake pathways, established as relevant for Bangladeshi adults through this review, include consumption of contaminated edible plant parts and animal-origin food, inhalation of contaminated air, soil ingestion, betel quid chewing, and tobacco smoking. This review qualifies and quantifies these arsenic intake pathways through analysis of the range of arsenic levels observed in different food types, water, soil, and air in Bangladesh, and highlights the contributions of dietary intake variation and cooking method in influencing arsenic exposures. This study also highlights the potential of desirable dietary patterns and intakes in increasing arsenic exposure which is relevant to Bangladesh where nutritional deficiencies and lower-than-desirable dietary intakes continue to be a major concern.

Risk of death from cardiovascular disease associated with low-level arsenic exposure among long-term smokers in a US population-based study

High levels of arsenic exposure have been associated with increases in cardiovascular disease risk. However, studies of arsenic's effects at lower exposure levels are limited and few prospective studies exist in the United States using long-term arsenic exposure biomarkers. We conducted a prospective analysis of the association between toenail arsenic and cardiovascular disease mortality using longitudinal data collected on 3939 participants in the New Hampshire Skin Cancer Study. Using Cox proportional hazard models adjusted for potential confounders, we estimated hazard ratios and 95% confidence intervals associated with the risk of death from any cardiovascular disease, ischemic heart disease, and stroke, in relation to natural-log transformed toenail arsenic concentrations. In this US population, although we observed no overall association, arsenic exposure measured from toenail clipping samples was related to an increased risk of ischemic heart disease mortality among long-term smokers (as reported at baseline), with increased hazard ratios among individuals with ≥ 31 total smoking years (HR: 1.52, 95% CI: 1.02, 2.27), ≥ 30 pack-years (HR: 1.66, 95% CI: 1.12, 2.45), and among current smokers (HR: 1.69, 95% CI: 1.04, 2.75). These results are consistent with evidence from more highly exposed populations suggesting a synergistic relationship between arsenic exposure and smoking on health outcomes and support a role for lower-level arsenic exposure in ischemic heart disease mortality.

A potential synergy between incomplete arsenic methylation capacity and demographic characteristics on the risk of hypertension: findings from a cross-sectional study in an arsenic-endemic area of inner Mongolia, China

Inefficient arsenic methylation capacity has been associated with various health hazards induced by arsenic. In this study, we aimed to explore the interaction effect of lower arsenic methylation capacity with demographic characteristics on hypertension risk. A total of 512 adult participants (126 hypertension subjects and 386 non-hypertension subjects) residing in an arsenic-endemic area in Inner Mongolia, China were included. Urinary levels of inorganic arsenic (iAs), monomethylarsonic acid (MMA), and dimethylarsinic acid (DMA) were measured for all subjects. The percentage of urinary arsenic metabolites (iAs%, MMA%, and DMA%), primary methylation index (PMI) and secondary methylation index (SMI) were calculated to assess arsenic methylation capacity of individuals. Results showed that participants carrying a lower methylation capacity, which is characterized by lower DMA% and SMI, have a higher risk of hypertension compared to their corresponding references after adjusting for multiple confounders. A potential synergy between poor arsenic methylation capacity (higher MMA%, lower DMA% and SMI) and older age or higher BMI were detected. The joint effects of higher MMA% and lower SMI with cigarette smoking also suggest some evidence of synergism. The findings of present study indicated that inefficient arsenic methylation capacity was associated with hypertension and the effect might be enhanced by certain demographic factors.

Drinking Water Arsenic Contamination, Skin Lesions, and Malignancies: A Systematic Review of the Global Evidence

Skin lesions and cancer are known manifestations of chronic exposure to arsenic contaminated drinking water. Epidemiologic data primarily comes from regions with exposures 1-2 orders of magnitude above the current World Health Organization (WHO) guidelines of 10 μg/L. Emerging evidence indicates that more common exposures may also be related to both noncancerous and cancerous changes to the skin. In this review, we focus on the body of epidemiologic literature that encompasses exposures within the WHO guidelines, excluding studies that lacked individual exposure estimates and case reports. For skin lesions and skin cancers, 15 and 10 studies were identified that met our criteria, respectively. For skin lesions, a consistent dose-response relationship with water arsenic has been observed, with increased risk evident at low- to moderate-dose exposure. Of the larger studies of specific histologic types of skin cancers, although with differing exposure definitions, there was evidence of dose-related relationships with both basal cell carcinomas and squamous cell carcinomas. The effect of arsenic exposure on skin lesion risk is likely modified by genetic variants that influence arsenic metabolism. Accumulating evidence suggests that arsenic may increase risk of skin lesions and skin cancers at levels not previously considered harmful, and that genetic factors may influence risk.

Differences of urinary arsenic metabolites and methylation capacity between individuals with and without skin lesions in Inner Mongolia, Northern China

Incomplete arsenic (As) methylation has been considered a risk factor of As-related diseases. This study aimed to examine the difference of urinary As metabolites and the methylation capacity between subjects with and without skin lesions. Urinary inorganic arsenic (iAs), monomethylarsonic acid (MMA), and dimethylarsinic acid (DMA) were analyzed. The percentage of each As species (iAs%, MMA%, and DMA%), the primary methylation index (PMI) and secondary methylation index (SMI) were calculated. The results showed that subjects with skin lesions have higher levels of urinary iAs (99.08 vs. 70.63 μg/g Cr, p = 0.006) and MMA (69.34 vs. 42.85 μg/g Cr, p = 0.016) than subjects without skin lesions after adjustment for several confounders. Significant differences of urianry MMA% (15.49 vs. 12.11, p = 0.036) and SMI (0.74 vs. 0.81, p = 0.025) were found between the two groups. The findings of the present study suggest that subjects with skin lesions may have a lower As methylation capacity than subjects without skin lesions.

Arsenic exposure of rural populations from the Rift Valley of Ethiopia as monitored by keratin in toenails

Arsenic (As) contamination of drinking water is a worldwide phenomenon whose effect among vulnerable and rural communities in the Rift Valley of Ethiopia in eastern Africa is not well studied. This study examines As exposure and bioaccumulation from drinking water by monitoring human keratin in the form of toenails from exposed populations. Groundwater samples from drinking water wells (n=34) were collected along with toenail samples (n=58) from local communities and were analyzed for trace metals including As by inductively coupled plasma mass spectrometry (ICP-MS). Of the total number of wells tested, 53% had As level above the WHO maximum contamination level of 10 p.p.b. Arsenic in toenails was significantly correlated to corresponding drinking water (r=0.72; R(2)=0.52; P<0.001). This correlation improves for drinking water with As concentrations above 2 p.p.b. (r=0.74; R(2)=0.54; P<0.001). Male minors (<18 years old) were found to have greater nail-As concentrations compared with adults consuming equal amounts of As (P<0.05). Estimated As dose specifically from drinking water sources was also associated with nail concentrations (P<0.01). We suggest that As measurement in nails could be a reliable method for detecting As exposure in residents living in rural areas.

Biological and behavioral factors modify biomarkers of arsenic exposure in a U.S. population

Although consumption of drinking water contaminated with inorganic arsenic is usually considered the primary exposure route, aggregate exposure to arsenic depends on direct consumption of water, use of water in food preparation, and the presence in arsenicals in foods. To gain insight into the effects of biological and behavioral factors on arsenic exposure, we determined arsenic concentrations in urine and toenails in a U.S. population that uses public or private water supplies containing inorganic arsenic. Study participants were 904 adult residents of Churchill County, Nevada, whose home tap water supplies contained <3 to about 1200 µg of arsenic per liter. Biomarkers of exposure for this study were summed urinary concentrations of inorganic arsenic and its methylated metabolites (speciated arsenical), of all urinary arsenicals (total arsenical), and of all toenail arsenicals (total arsenical). Increased tap water arsenic concentration and consumption were associated with significant upward trends for urinary speciated and total and toenail total arsenical concentrations. Significant gender differences in concentrations of speciated and total arsenicals in urine and toenails reflected male-female difference in water intake. Both recent and higher habitual seafood consumption significantly increased urinary total but not speciated arsenical concentration. In a stepwise general linear model, seafood consumption significantly predicted urinary total arsenical but not urinary speciated or toenail total arsenical concentrations. Smoking behavior significantly predicted urinary speciated or total arsenical concentration. Gender, tap water arsenic concentration, and primary drinking water source significantly predicted urinary speciated and total concentrations and toenail total arsenical concentrations. These findings confirm the primacy of home tap water as a determinant of arsenic concentration in urine and toenails. However, biological and behavioral factors can modify exposure-response relations for these biomarkers. Refining estimates of the influence of these factors will permit better models of dose-response relations for this important environmental contaminant.

Burden of skin lesions of arsenicosis at higher exposure through groundwater of taluka Gambat district Khairpur, Pakistan: a cross-sectional survey

Prior surveys conducted have found higher proportion of arsenic-contaminated wells in villages along river Indus in Pakistan. This study aims to determine the prevalence of arsenicosis skin lesions among population exposed to higher exposure in taluka Gambat district Khairpur in Sindh. The cross-sectional survey was conducted from August 2008 to January 2009 among 610 households. A total of 707 water sources (hand pumps/wells) were tested from the villages of union councils of Agra and Jado Wahan for arsenic levels with Quick rapid arsenic field test kits. A total of 110 households exposed to arsenic levels >50 ppb were identified. Case screening for arsenic skin lesions was performed for 610 individuals residing in these 110 high-risk households. Information regarding household and socio-demographic characteristics, height and weight measurements and arsenic exposure assessment were collected. Physical examinations by trained physicians were carried out to diagnose the arsenic skin lesions. After data cleaning, 534 individuals from all age groups were included in the final analysis which had complete exposure and outcome information. Overall prevalence of arsenicosis skin lesions was 13.5 % (72 cases). Of the 534 individuals, 490 (91.8 %) were exposed to arsenic levels of ≥100 ppb in drinking water (8.2 % to >50-99 ppb, 58.6 % to 100-299 ppb, 14.6 % to 300-399 ppb and 18 % to ≥400 ppb). Prevalence rate (per 100 population) of arsenicosis was highest at arsenic levels of 100-199 ppb (15.2 cases) followed by ≥400 ppb (13.5 cases) and 300-399 (12.8 cases). Prevalence rate was higher among females (15.2) compared to males (11.3). Our study reports arsenicosis burden due to exposure to higher arsenic levels in drinking water in Pakistan. Exposure to very high levels of arsenic in drinking water calls for urgent action along river Indus. Prevalence of skin lesions increases with increasing arsenic levels in drinking groundwater. Provision of arsenic-free drinking water is essential to avoid current and future burden of arsenicosis in Pakistan.

Effect of nicotine pretreatment on arsenic-induced oxidative stress in male Wistar rats

Humans are commonly exposed to nicotine, one of the most important lifestyle chemicals. The occurrence of high levels of arsenic in the groundwater of the southeast region of Asia has received much attention in the past decade and has become a global health concern. Predominant occurrence of both these chemicals and ease of their human exposure led us to investigate the effect of nicotine, a major tobacco alkaloid, on arsenic toxicity. Adult male rats were pre-exposed to two different doses of nicotine (0.75 and 3 mg/kg, intraperitoneally) for 7 days followed by 30 days of arsenic exposure (50 ppm sodium arsenite in drinking water). Nicotine pre-exposure resulted in an increased brain arsenic accumulation and a decreased liver arsenic concentration. Arsenic also caused a significant oxidative stress in the blood, brain and liver of the exposed rats. Glutathione- S-transferase, a phase II enzyme, was inhibited by both arsenic and nicotine but no such inhibition was noted in arsenic-treated animals pre-exposed to nicotine. Upon nicotine pre-exposure, brain acetylcholinesterase increased, while monoamine oxidase (MAO) decreased. The toxic effects of MAO significantly attenuated with nicotine pre-exposure. The present study suggests that nicotine may not be the major contributing factor for the previously reported synergistic toxic interaction between tobacco and arsenic. Nicotine pre-exposure in arsenic-exposed animals revealed interesting toxicokinetics and oxidative stress modulating interactions in the brain and liver of rats, which requires further exploration.

Pregnancy and the methyltransferase genotype independently influence the arsenic methylation phenotype

OBJECTIVES

The methyltransferase genotype and pregnancy both influence the arsenic metabolism phenotype, but it is unknown whether these factors interact, explaining the drastic changes in the efficiency of arsenic metabolism observed among pregnant women. The aim of this study was to evaluate the relative contribution of the methyltransferase genotype and pregnancy to the arsenic metabolism phenotype.

METHODS

We studied longitudinally the arsenic metabolite pattern in urine (at approximately gestational weeks 8, 14, and 30) of 303 women exposed to arsenic through drinking water and food in rural Bangladesh. Urinary arsenic metabolites were measured by high-performance liquid chromatography-inductively coupled plasma mass spectrometry. Data were available on genotypes for 16 polymorphisms, combined as haplotypes, in three methyltransferases: arsenic(+III)methyltransferase (AS3MT) and DNA-methyltransferases 1a and 3b (DNMT1a and DNMT3b). Changes in the arsenic metabolite pattern over time were evaluated by haplotype using logistic quantile regression.

RESULTS

All four AS3MT haplotypes and all three DNMT1a haplotypes significantly influenced the metabolite pattern in the pregnant women, with consistent effects of genotype over the entire course of pregnancy. No interaction was found between the haplotypes and pregnancy-related changes in the arsenic metabolism phenotype. DNMT3b haplotypes did not significantly influence the metabolite pattern. We observed a pregnancy-attributable decrease of 5.7% in the most risk-associated monomethylated metabolite, methylarsonic acid, whereas changes between 1.6 and 5.3% of methylarsonic acid could be attributed to haplotypes of AS3MT and DNMT1a.

CONCLUSION

Independent of the genotype, the efficiency of arsenic methylation increased markedly over the course of pregnancy. The effect of pregnancy on the metabolite pattern during the observational period was greater than the effect of genotype.

In utero arsenic exposure is associated with impaired thymic function in newborns possibly via oxidative stress and apoptosis

Prenatal arsenic exposure is associated with increased infant morbidity and reduced thymus size, indicating arsenic-related developmental immunotoxicity. We aimed to evaluate effects of prenatal arsenic exposure on thymic function at birth and related mechanisms of action. In a Bangladeshi cohort, arsenic was measured in urine (U-As, gestational week (GW) 8 and 30) and blood (B-As, GW14) in 130 women. Child thymic index was measured by sonography at birth and thymic function by signal-joint T-cell receptor-rearrangement excision circles (sjTRECs) in cord blood mononuclear cells (CBMC). In a subsample (n = 44), sjTRECs content in isolated CD4(+) and CD8(+) T cells, expression of oxidative-stress defense and apoptosis-related genes in CBMC, arsenic concentrations (urine, placenta, and cord blood), and oxidative stress markers in placenta and cord blood were measured. In multivariable-adjusted regression, ln U-As (GW8) was inversely associated with ln sjTRECs in CBMC (B = -0.25; 95% confidence interval [CI] -0.48 to -0.01). Using multivariable-adjusted spline regression, ln U-As (GW30) and ln B-As (GW14) were inversely associated with ln sjTRECs in CBMC (B = -0.53; 95% CI -0.93 to -0.13 and B = -1.27; 95% CI -1.89 to -0.66, respectively) below spline knots at U-As 150 µg/l and B-As 6 µg/kg. Similar inverse associations were observed in separated CD4(+) and CD8(+) T cells. Arsenic was positively associated with 8-hydroxy-2'-deoxyguanosine in cord blood (B = 0.097; 95% CI 0.05 to 0.13), which was inversely associated with sjTRECs in CD4(+) and CD8(+) T cells. In conclusion, prenatal arsenic exposure was associated with reduced thymic function, possibly via induction of oxidative stress and apoptosis, suggesting subsequent immunosuppression in childhood.

Smoking and the skin

Cigarette smoking has been associated with significant morbidity affecting all systems of the body, including the integumentary system. We review the many dermatologic hazards of tobacco use. It is important to distinguish between the effects of tobacco smoke from effects of pure nicotine on the skin. All skin cells express several subtypes of the nicotinic class of acetylcholine receptors, including the α7 receptor. Many chronic dermatoses are affected by smoking either negatively or positively. Elucidation of positive associations with a particular disease can lead to improvement from smoking cessation, whereas inverse correlation may lead to development of a disease-specific treatment with nicotinergic agonists.

Toxic elements in tobacco and in cigarette smoke: inflammation and sensitization

Biochemically and pathologically, there is strong evidence for both atopic and nonatopic airway sensitization, hyperresponsiveness, and inflammation as a consequence of exposure to tobacco mainstream or sidestream smoke particulate. There is growing evidence for the relation between exposure to mainstream and sidestream smoke and diseases resulting from reactive oxidant challenge and inflammation directly as a consequence of the combined activity of neutrophils, macrophages, dendritic cells, eosinophils, basophils, as a humoral immunological consequence of sensitization, and that the metal components of the particulate play a role in adjuvant effects. As an end consequence, carcinogenicity is a known outcome of chronic inflammation. Smokeless tobacco has been evaluated by the IARC as a group 1 carcinogen. Of the many harmful constituents in smokeless tobacco, oral tissue metallothionein gradients suggest that metals contribute to the toxicity from smokeless tobacco use and possibly sensitization. This work reviews and examines work on probable contributions of toxic metals from tobacco and smoke to pathology observed as a consequence of smoking and the use of smokeless tobacco.

Gender and age differences in mixed metal exposure and urinary excretion

BACKGROUND

Little is known about the variation in exposure to toxic metals by age and gender and other potential modifying factors. We evaluated age and gender differences by measurements of metal/element concentrations in urine in a rural population in Matlab, Bangladesh, in three age groups: 8-12 (N=238), 14-15 (N=107) and 30-88 (N=710) years of age, living in an area with no point sources of metal exposure but where elevated water arsenic concentrations are prevalent.

RESULTS

We found marked differences in urine concentrations of metals and trace elements by gender, age, tobacco use, socioeconomic and nutritional status. Besides a clearly elevated urinary arsenic concentration in all age groups (medians 63-85 μg As/L), and despite the low degree of contamination from industries and traffic, the urine concentrations of toxic metals such as cadmium and lead were clearly elevated, especially in children (median 0.31 μg Cd/L and 2.9 μg Pb/L, respectively). In general, women had higher urinary concentrations of toxic metals, especially Cd (median 0.81 μg/L) compared to men (0.66 μg/L) and U (median 10 ng/L in women, compared to 6.4 ng/L in men), while men had higher urinary concentrations of the basic and essential elements Ca (69 mg/L in men, 30-50 years, compared to 52 mg/L in women), Mg (58 mg/L in men compared to 50 mg/L in women), Zn (182 μg/L in men compared to 117 μg/L in women) and Se (9.9 μg/L in men compared to 8.7 μg/L in women). Manganese was consistently higher in females than in males in all age groups, suggesting a biological difference between females and males in Mn metabolism. Increasing socioeconomic status decreased the toxic metal exposure significantly in children and especially in men. Poor iron status was detected in 17% of children, adolescents and women, but only in 6% of men. Also zinc deficiency was more prevalent in females than in males.

CONCLUSIONS

Women and children seemed to be more at risk for toxic metal exposure than men and at the same time more vulnerable to micronutrient deficiency. Higher concentrations of the toxic metals in urine in women are likely to reflect an increased gastrointestinal absorption of these metals at micronutrient deficiency, such as low body iron stores and Zn deficiency. Higher urinary concentrations of the essential elements in men likely reflect a better nutritional status. There is a need for information on exposure, lifestyle and socioeconomic factors, stratified by gender and age, for the purpose of conducting balanced risk assessment and management that considers such differences.