Sensitivity Analysis of U.S. EPA's Estimates of Skin Cancer Risk from Inorganic Arsenic in Drinking Water

The current U.S. Environmental Protection Agency's (USEPA's) risk analysis on the Integrated Risk Information System (IRIS) for arsenic in drinking water is based on an epidemiological study of skin cancer in Taiwan. Assumptions used in the USEPA application of the multistage-Weibull model for risk estimation were varied to assess the effect on predicted risk of skin cancer to the U.S. population at arsenic concentrations of 1 to 50?µg/L in drinking water. Among the assumptions tested, the only notable change in risk estimates was a reduction when the arsenic concentration used as representative for Taiwan villages in the low range (<300?µg/L) was increased to the 75th percentile (245?µg/L) in place of the mean used in the USEPA analysis (170?µg/L), but the representative value for Taiwan villages in the high range (≥600?µg/L) was not increased simultaneously to the 75th percentile. Additionally, a simulation study was conducted using records of arsenic measurements in wells from the same period and region of Taiwan as the original study. The exposure-response curve estimated from 60 villages (60 data points) differed only marginally from the outcome when data were summarized into four data points (as in the USEPA skin cancer analysis). Briefly discussed are differences between the study area of Taiwan and the U.S. in nutritional status and consumption of inorganic arsenic in food that might bias predicted U.S. skin cancer risks.     

Annual cancer risks from chemicals in North Carolina community water systems

Motivated partly by concerns about cancer, the U.S. Congress in 1986 amended the Safe Drinking Water Act (SDWA) by requiring that community water systems monitor 81 chemicals and remove those detected at concentrations above health-based standards. No prior research has used the resulting 30 years of monitoring data to analyze cancer risks from chemicals in US drinking water. To fill this gap, this paper uses chemical monitoring data from North Carolina's (NC's) 2,120 community water systems along with a risk assessment approach commonly applied in global burden of disease studies to quantify cancer risks of regulated chemicals in drinking water. The results indicate that 0.30% of NC cancer deaths are attributable to regulated drinking water contaminants and that the average annual individual risk is 7.2 × 10^?6. More than 99% of this risk arises from disinfection by-products, with the remaining risk mostly attributable to arsenic and alpha particle radiation. In no water system does the combined risk from chemicals other than disinfection by-products, arsenic, or alpha particles exceed 10^?4. The results suggest that regulated chemicals pose very low cancer risks and that risks from chemicals other than disinfection by-products, arsenic, and alpha particles are negligible in NC community water systems.     

Probabilistic Analysis of Human Health Risks Associated with Background Concentrations of Inorganic Arsenic: Use of a Margin of Exposure Approach

Substantial evidence exists from epidemiological and mechanistic studies supporting a sublinear or threshold dose–response relationship for the carcinogenicity of ingested arsenic; nonetheless, current regulatory agency evaluations have quantified arsenic risks using default, generic risk assessment procedures that assume a linear, no-threshold dose–response relationship. The resulting slope factors predict risks from U.S. background arsenic exposures that exceed certain regulatory levels of concern, an outcome that presents challenges for risk communication and risk management decisions. To better reflect the available scientific evidence, this article presents the results of a Margin of Exposure (MOE) analysis to characterize risks associated with typical and high-end background exposures of the U.S. population to arsenic from food, water, and soil. MOE values were calculated by comparing a no-observable-adverse-effect-level (NOAEL) derived from the epidemiological literature with exposure estimates generated using a probabilistic (Monte Carlo) model. The plausibility and conservative nature of the exposure and risk estimates evaluated in this analysis are supported by sensitivity and uncertainty analyses and by comparing predicted urinary arsenic concentrations with empirical data. Using the more scientifically supported MOE approach, the analysis presented in this article indicates that typical and high-end background exposures to inorganic arsenic in U.S. populations do not present elevated risks of carcinogenicity.     

How Creditable are Cancer Risk Estimates from the S.W. Taiwan Database for Arsenic in Drinking Water?

A database of cancer mortality and arsenic concentrations in village wells in an arseniasis-endemic area of southwestern Taiwan has been the predominant source of information for risk assessments of U.S. Environmental Protection Agency and two National Research Council reports on arsenic and drinking water. A limitation of the data, however, is that exposure is ecological, that is, cancer mortality cannot be matched with arsenic exposure on an individual basis, just grouped by village. The resultant potential for bias is examined by comparing dose-response analyses of villages divided into two groups, those with well concentrations in a narrow range and the remainder. The narrow range group suggests a flat or downward change in risk in the low dose range, whereas the other group indicates increasing risk. More disturbingly, however, the dose-response data are highly dispersed for both groups and the dose-response curve predicts background bladder/lung cancer levels much higher than a southwestern Taiwan comparison population. This may be due to a large variability between villages of the study area in bladder/lung cancer not directly attributable to arsenic. Including the comparison population in the dose-response analysis artificially anchors the dose-response curve at a background level inconsistent with the study population and likely just biases the slope factor upward.     

An integrated health risk assessment of indigenous children exposed to arsenic in Sonora,Mexico

Exposure to inorganic arsenic (InAs) through drinking water, even at low to moderate concentrations, is a global public health problem. The objectives of this study were to estimate the risk ratio (HQ), cancer risk (R), and DNA damage (comet assay) of children from three indigenous Yaqui populations located in southern Sonora, Mexico, who were exposed to InAs through drinking water. A cross-sectional study was employed, and analysis of InAs in water and urine was performed via HPLC/ICP-MS. InAs levels in drinking water from Pótam, Vícam, and Cócorit were 108.2, 36.0, and 6.2 μg/L^?1 respectively. Children from Pótam had arsenic concentrations in urine of 107.1 μg As L^?1 compared with 40.3 μg As L^?1 for the children of Cócorit. The HQ values for the children of Pótam, Vícam, and Cócorit were 16.64, 6.02, and 0.94, while the R values were 9.4E-04, 3.5E-04, and 5.7E-05, respectively. Children with the highest arsenic exposure had significantly increased DNA damage (OTM = 14.4 vs. 4.3) [p < 0.0005] which positively correlated with urinary arsenic levels (r = 0.56, p < 0.0001). In conclusion, children of Pótam and Vícam are at significant risk of developing chronic diseases and cancers associated with chronic exposure to this metalloid.     

Noncancer risk assessment of arsenic safe and unsafe water uses: Bayesian estimation on cohort study

Cancer and noncancer risk of arsenic exposure depends on arsenic intake through drinking water and diets. The present study evaluated the probability of noncancer effects of arsenic exposure from drinking water and diets in a cohort of 82 participants in arsenic-endemic rural areas, considering arsenic-safe and arsenic-unsafe water uses for three consecutive years. The risk assessment included the collection of last 24 hours' diet replica and urine of the participants followed by total arsenic analysis of the same. Toxic dose emerging from exposure duration is a nonlinear variable. So, Bayesian estimation of the data for noncancer risk assessment of the variable arsenic consumption was performed. In spite of using arsenic-safe water, we observed arsenic consumption and release. Participants with skin lesions had more arsenic in urine than participants without skin lesions. Future risk for participants without skin lesions was twice due to less arsenic release in urine. For the first time, Bayesian simulation was used to assess noncancer risk on a cohort for a consecutive three-year study. A significant finding was the higher assessed noncancer risk of the participants without skin lesions than the participants with skin lesions.     

Assessing Risk of Inorganic Arsenic in Drinking Water in the United States

Limitations of the current EPA risk assessment for inorganic arsenic in drinking water in the U.S. are discussed. An empirical approach is suggested that would sample survey the populations in regions with the highest arsenic levels in drinking water for signs of arsenicism, which has been much more prevalent and appeared much earlier in exposed populations than cancer (e.g., of the skin). Biomarkers of exposure, such as arsenic content in urine, nails, hair, and skin scales, may provide even earlier indications of subpopulations with excessive arsenic exposure and identify individuals at risk. Further study is needed to evaluate fully the potential for use of biomarkers, focusing on the accuracy and reliability of analytical methods, the utility of biomarkers as indicators of short-term and long-term exposure and as precursors to clinical signs of arsenicism, and the use of “normal” ranges of biomarkers for interpretation of field observations.     

Arsenic in Drinking Water and Mortality for Cancer and Chronic Diseases in Central Italy, 1990-2010

Background

In several volcanic areas of Italy, arsenic levels exceed European regulatory limits (10 μg/L in drinking water). There is still uncertainty about health risks from arsenic at low-medium doses (<100 μg/L).

Objectives

A large population-based study using an administrative cohort of residents in the Viterbo province (Central Italy), chronically exposed to low-medium arsenic levels via drinking water, was investigated to evaluate the effects of a lifetime exposure to arsenic on mortality from cancers and chronic diseases.

Methods

The study population consisted of 165,609 residents of 17 municipalities, followed from 1990 until 2010. Average individual arsenic exposure at the first residence (As_I) was estimated through a space-time modeling approach using residential history and arsenic concentrations from water supply. A time-dependent Cumulative Arsenic dose Indicator (CAI) was calculated, accounting for daily water intake and exposure duration. Mortality Hazard Ratios (HR) were estimated by gender for different diseases using Cox proportional models, adjusting for individual and area-level confounders. A flexible non-parametric approach was used to investigate dose-response relationships.

Results

Mean As_I exposure was 19.3 μg/L, and average exposure duration was 39.5 years. Associations of As_I and CAI indicators with several diseases were found, with greatest risks found for lung cancer in both sexes (HR = 2.61 males; HR = 2.09 females), myocardial infarction, peripheral arterial disease and COPD in males (HR = 2.94; HR = 2.44; HR = 2.54 respectively) and diabetes in females (HR = 2.56). For lung cancer and cardiovascular diseases dose-response relationship is modelled by piecewise linear functions revealing effects even for doses lower than 10 μg/L, and no threshold dose value was identified as safe for health.

Conclusions

Results provide new evidence for risk assessment of low-medium concentrations of arsenic and contribute to the ongoing debate about the threshold-dose of effect, suggesting that even concentrations below 10 μg/L carry a mortality risk. Policy actions are urgently needed in areas exposed to arsenic like in the Viterbo province, to comply with current EU regulations.     

Serum levels of the extracellular domain of the epidermal growth factor receptor in individuals exposed to arsenic in drinking water in Bangladesh

Epidermal growth factor receptor-dependent mechanisms have been implicated in growth signal transduction pathways that contribute to cancer development, including dermal carcinogenesis. Detection of the extracellular domain of the epidermal growth factor receptor (EGFR ECD) in serum has been suggested as a potential biomarker for monitoring this effect in vivo. Arsenic is a known human carcinogen, producing skin and other malignancies in populations exposed through their drinking water. One such exposed population, which we have been studying for a number of years, is in Bangladesh. The purpose of this study was to examine the EGFR ECD as a potential biomarker of arsenic exposure and/or effect in this population. Levels of the EGFR ECD were determined by enzyme-linked immunosorbent assay in the serum samples from 574 individuals with a range of arsenic exposures from drinking water in the Araihazar area of Bangladesh. In multiple regression analysis, serum EGFR ECD was found to be positively associated with three different measures of arsenic exposure (well water arsenic, urinary arsenic and a cumulative arsenic index) at statistically significant levels (p≤0.034), and this association was strongest among the individuals with arsenic-induced skin lesions (p ≤ 0.002). When the study subjects were stratified in tertiles of serum EGFR ECD levels, the risk of skin lesions increased progressively for each increase in all three arsenic measures (also stratified in tertiles) and this increasing risk became more pronounced among subjects within the highest tertile of EGFR ECD levels. These results suggest that serum EGFR ECD levels may be a potential biomarker of effect of arsenic exposure and may indicate those exposed individuals at greatest risk for the development of arsenic-induced skin lesions.     

Effect of high arsenic content in drinking water on rat brain.

The permissible limit of arsenic content in drinking water is 0.05 ppm, whereas, in many parts of West Bengal the arsenic level in drinking water is 0.1 ppm, frequently 0.3 ppm and even 3.0 ppm, though rarely. In order to assess possible risk to brain function by drinking such water, rats were given arsenic mixed in drinking water at the above four concentrations for 40 days. There was increased lipid peroxidation at all doses of arsenic, including the 'permissible limit', decrease in glutathione level, superoxide dismutase and glutathione reductase activities, indicating the free-radical-mediated degeneration of brain.     

A Dietary Risk Assessment for Indigenous Consumption of Natural Salt Deposits in the Darhad Valley,Northern Mongolia

The nomadic herding population of the Darhad Valley, in northern Mongolia, collects and utilizes a salt precipitate, called hujir, which develops at the saline system, Tohi. This culturally important indigenous dietary supplement is consumed daily as an ingredient in a salty milk-tea and because of its essential micro- and macronutrients it is a beneficial and necessary part of their daily diet. Despite its benefits, there are increasing health concerns among the Darhad people as a result of consuming hujir. Therefore, we conducted a dietary risk assessment. Consumption rates were obtained from interviews with nomadic herders of the valley and a chronic exposure assessment was completed using chemical analyses on hujir samples. A combination of chronic toxicity threshold values, dietary reference intake recommendations, and drinking water guidelines were used to estimate dietary risks related to hujir consumption. Exposures to arsenic, fluoride, and nitrate were as high as 33, 1.2, and 1.3 times the chronic oral reference dose, respectively. Exposures to antimony, arsenic, and lead were 1.7, 19, and 14 times the drinking water guidelines, respectively. Given these results, additional studies are needed to better understand possible health effects associated with hujir consumption in the Darhad population, especially for arsenic.     

Differential Susceptibility of Human Peripheral Blood T Cells to Suppression by Environmental Levels of Sodium Arsenite and Monomethylarsonous Acid

Human exposure to arsenic in drinking water is known to contribute to many different health outcomes such as cancer, diabetes, and cardiopulmonary disease. Several epidemiological studies suggest that T cell function is also altered by drinking water arsenic exposure. However, it is unclear how individual responses differ to various levels of exposure to arsenic. Our laboratory has recently identified differential responses of human peripheral blood mononuclear cell (HPMBC) T cells as measured by polyclonal T cell activation by mitogens during sodium arsenite exposure. T cells from certain healthy individuals exposed to various concentrations (1–100 nM) of arsenite in vitro showed a dose-dependent suppression at these extremely low concentrations (∼0.1–10 ppb) of arsenite, whereas other individuals were not suppressed at low concentrations. In a series of more than 30 normal donors, two individuals were found to be sensitive to low concentration (10 nM equivalent ∼1 ppb drinking water exposure) to sodium arsenite-induced inhibition of T cell proliferation produced by phytohemagglutinin (PHA) and anti-CD3/anti-CD28. In an arsenite-susceptible individual, arsenite suppressed the activation of Th1 (Tbet) cells, and decreased the percentage of cells in the double positive Th17 (RORγt) and Treg (FoxP3) population. While the majority of normal blood donors tested were not susceptible to inhibition of proliferation at the 1–100 nM concentrations of As⁺³, it was found that all donors were sensitive to suppression by 100 nM monomethylarsonous acid (MMA⁺³), a key metabolite of arsenite. Thus, our studies demonstrate for the first time that low ppb-equivalent concentrations of As⁺³ are immunosuppressive to HPBMC T cells in some individuals, but that most donor HPBMC are sensitive to suppression by MMA⁺³ at environmentally relevant exposure levels.     

Arsenic Ingestion and Bladder Cancer Mortality—What Do the Dose-Response Relationships Suggest About Mechanism?

The Black–Foot Disease (BFD) endemic area of SW Taiwan has historically been the principal data source for assessing cancer risks from arsenic in drinking water in the United States, most recently in a 42–village ecological study. The data showed a discontinuity for bladder cancer risk at about 400 μg/L. A proposed explanation was that the arsenic–dependent bladder cancer risk was found only for those villages that were dependent on water from the artesian well aquifer (As > 350 μg/L and co–contamination with humic acids) and not for those villages receiving water from the shallow aquifer (As < 350 μg/L without humic acids). The humic acids were present from the algae that grew in the uncovered tanks holding the artesian water. The risk factors (slopes) developed from these subpopulations of the SW Taiwan study were applied to the data from an ecological study of median groundwater arsenic concentration and bladder cancer mortality in 133 U.S. counties dependent on groundwater to determine the slope most predictive of U.S. experience for bladder cancer mortality and arsenic ingestion (Lamm et al. 2004 Lamm, S H, Engel, AKruse, M B. 2004. Arsenic in drinking water and bladder cancer mortality in the United States: An analysis based on 133 U.S. counties and 30 years of observation.. J Occup Environ Med, 46(3): 298–306. [PUBMED][INFOTRIEVE][CSA][Crossref], [PubMed], [Web of Science ®] [Google Scholar]).The U.S. data excluded the SW Taiwan slope estimate derived from the artesian well–dependent subpopulation but were consistent with the slope estimate derived from the subpopulation using shallow aquifer water. Both the SW Taiwan data in the absence of high arsenic levels (< 350 μg/L) and humic acids and the U.S. 133–county data with As < 60 μg/L are consistent with no increased bladder cancer mortality risk from drinking water arsenic concentrations in the exposure range of observation. These analytic results are consistent with both co–carcinogenesis and high–exposure (hundreds of μ g/L As) dependence models of toxicological mode–of–action. These dose–response relationships should influence prioritization in the remediation of arsenic–contaminated drinking water supplies.     

Importance of Arsenic Speciation in Populations Exposed to Arsenic in Drinking Water

Total arsenic in urine is often the principal means for assessing chronic exposure to arsenic-contaminated drinking water. This approach ignores many components of the human diet, especially fish and seafood that contain arsenic at significant concentrations. The toxicity differences between the inorganic forms and the dietary forms suggest both should be evaluated when attempting to assess risk from arsenic exposure. Urine biomonitoring for 53 participants was used to confirm reduction in arsenic exposure resulting from well water remediation removing inorganic arsenic from drinking water. Initially, only total arsenic urine assays were performed, but spikes in total arsenic urine concentrations were determined to be diet related and demonstrated the need for analytical methods that differentiate the arsenic species. A secondary analysis was added that quantified inorganic-related arsenic in urine and the dietary forms related to fish and seafood by subtraction from total arsenic. Significant differences were found between the inorganic arsenic component and the total arsenic measured in their urine. On average, approximately 76% of total arsenic in urine was attributed to fish and other organo-arsenic dietary sources, implying a potential significant overestimate of exposure, and demonstrating the need for differentiation of the inorganic-related arsenic from dietary arsenic.     

Arsenic exposure levels of petrochemical workers in three workplace settings in Rayong Province,Thailand

Background: Crude oil and natural gas are often contaminated with arsenic. As a carcinogen, arsenic contamination in the workplace is of concern, particularly when urinary arsenic levels are higher than the standard. The aim of this study was to identify exposure sources of arsenic among petrochemical workers. Methods: A total of 188 operators and 30 office workers participated in the study. Ninety-three workplace air samples, three main meals in five consecutive days, and drinking water were collected from each participant. Urine was collected at the end of the day after the last food sample was collected from each subject. Urine samples where arsenic concentration exceeded 100 mg/L were further analyzed to identify species. Results: The average arsenic concentrations in operators' and office workers' food and urine were 0.55 ± 1.00 and 0.49 ± 0.67 mg/kg; and 76.43 ± 107.36 and 149.92 ± 200.28 mg/L, respectively. The arsenic concentrations in air and water were well below their standards. The urinary arsenic correlated well with arsenic in the food but not in the air and water. Conclusion: Occupational exposure to arsenic among operators and office workers was lower than 1% TLV (Threshold limit value) and did not differ significantly. The major source of arsenic exposure Q2 was food.     

Fish micronucleus assay to assess genotoxic potential of arsenic at its guideline exposure in aquatic environment

The exposure to arsenic, a potential genotoxic carcinogen in humans, via drinking water is a serious worldwide health hazard. The arsenic content of 10 μg L^?1 in drinking water, however, has been established as its guideline standard (maximum contaminant limit) that has been estimated to pose minimum risk to cancer. Since micronucleus induction in the erythrocytes of fish is a sensitive indicator of genotoxic agents in water, the piscine micronucleus assay was used in the present experiment to assess the genotoxic potential of arsenic at its various exposure levels including the guideline value for drinking water. The experiments were conducted in two different species of fishes, the pond murrel (Channa punctatus) and the goldfish (Carassius auratus). Significant increases in the frequency of micronucleated erythrocytes were documented in a dose-dependent manner in both Channa and Carassius. The fishes, however, exhibited variations in inter-specific sensitivity to micronucleus induction following arsenic exposure. The exposure level of arsenic at its guideline value for drinking water, therefore, exhibited marked genotoxicity in fishes.     

Arsenic Removal from Aqueous Solutions by Different Bacillus and Lysinibacillus Species

Removal of toxic and carcinogenic arsenic from underground water is very essential for the safety of water that may be used for drinking or irrigation. In this study, six different bacterial strains were recently isolated from a groundwater sample, routinely used for irrigation at Taif City, Kingdom of Saudi Arabia, containing arsenic, vanadium, and boron. The isolates were molecularly identified and the 16S rDNA sequencing data revealed their belonging to two different genera, Bacillus and Lysinibacillus. B. cereus strains EA4, EA5, and EA6 were able to resist arsenic up to 15 mg/L. B. cereus strain EA5 and a mixed culture of L. sphaericus EA1, B. fusiformis EA2, and Lysinibacillus sp. EA3 were found to be efficient in bioremediation of arsenic oxychloride up to 94.9% and 99.7%, respectively. Due to these near-standard records, these strains are strongly recommended for bioremediation of the highly toxic arsenic from the environment. B. cereus EA5 was also effective to remediate different concentrations of arsenic. High concentrations of arsenic showed dramatic decrease in the bioremediation activity of this strain. Reduction in cell size was distinct in scanning electron micrographs when cells were exposed to arsenic. Besides, protein electrophoresis showed that around 15 different stress proteins were produced when cells of B. cereus EA5 were exposed to arsenic oxychloride.     

Tumour size can have an impact on the outcomes of epidemiological studies on second cancers after radiotherapy

Obtaining a correct dose–response relationship for radiation-induced cancer after radiotherapy presents a major challenge for epidemiological studies. The purpose of this paper is to gain a better understanding of the associated uncertainties. To accomplish this goal, some aspects of an epidemiological study on breast cancer following radiotherapy of Hodgkin’s disease were simulated with Monte Carlo methods. It is demonstrated that although the doses to the breast volume are calculated by one treatment plan, the locations and sizes of the induced secondary breast tumours can be simulated and, based on these simulated locations and sizes, the absorbed doses at the site of tumour incidence can also be simulated. For the simulations of point dose at tumour site, linear and non-linear mechanistic models which predict risk of cancer induction as a function of dose were applied randomly to the treatment plan. These simulations provided for each second tumour and each simulated tumour size the predicted dose. The predicted-dose–response-characteristic from the analysis of the simulated epidemiological study was analysed. If a linear dose–response relationship for cancer induction was applied to calculate the theoretical doses at the simulated tumour sites, all Monte-Carlo realizations of the epidemiological study yielded strong evidence for a resulting linear risk to predicted-dose–response. However, if a non-linear dose–response of cancer induction was applied to calculate the theoretical doses, the Monte Carlo simulated epidemiological study resulted in a non-linear risk to predicted-dose–response relationship only if the tumour size was small (<?1.5 cm). If the diagnosed breast tumours exceeded an average diameter of 1.5 cm, an applied non-linear theoretical-dose–response relationship for second cancer falsely resulted in strong evidence for a linear predicted-dose relationship from the epidemiological study realizations. For a typical distribution of breast cancer sizes, the model selection probability for a resulting predicted-dose linear model was 61% although a non-linear theoretical-dose–response relationship for cancer induction had been applied. The results of this study, therefore, provide evidence that the shapes of epidemiologically obtained dose–response relationships for cancer induction can be biased by the finite size of the diagnosed second tumour, even though the epidemiological study was done correctly.     

Evaluation of Toxic Risk Assessment of Arsenic in Male Subjects Through Drinking Water in Southern Sindh Pakistan

The arsenic (As) hazardous quotient was estimated based on concentration of As in drinking water and scalp hair of male subjects of two age groups (n = 360) consuming As contaminated water at different levels and non-contaminated drinking water. The total As concentrations in drinking water of less-exposed (LE) and high-exposed (HE) areas was found to be 3- to 30-fold higher than the permissible limit of the World Health Organization (2004) for drinking water, while the levels of As in drinking water of non-exposed (NE) areas was within the permissible limit. The levels of As in scalp hair samples of male subjects of two age groups belonging to NE, LE, and HE areas ranged from 0.01 to 0.27, 0.11–1.31, and 0.36–6.80 μg/g, respectively. A significant correlation between As contents of drinking water and As concentration in scalp hair was observed in sub-district Gambit (r = 0.825–0.852, p < 0.001) as compared to those subjects belonging to LE sub-district Thari Mirwah. A toxicity risk assessment provides a hazard quotient corresponding to <10 that indicates non-carcinogenic exposure risk of understudy areas.     

Arsenic in groundwater and its health risk assessment in drinking water of Mailsi,Punjab, Pakistan

The present study was aimed at assessing drinking water quality regarding arsenic (As) and its impact on health from Mailsi (Punjab), Pakistan. Forty-four groundwater samples were collected from two sites, Sargana and Mailsi. Arsenic and other cations were determined by atomic absorption spectrophotometer, whereas the anions were determined either through titration or spectrophotometer. The results revealed that dominant anions were HCO₃^? and Cl^?, Ca⁺² was the dominant cation, and overall water chemistry of the area was CaMgHCO₃^? type. Arsenic concentrations were high, ranging from 11 to 828 µg/L that crossed the World Health Organization permissible limits. Likewise, higher SO₄^?2 concentrations ranging from 247 to 1053 mg/L were observed. The health risk index was higher in the Sargana site, which employed the differences in terms of higher Average Daily Dose, Hazard Quotient, and Carcinogenic Risk of arsenic, which is unsuitable for drinking purposes. The area seems to be at high risk due to arsenic pollution and wells have never been tested for arsenic concentrations earlier; therefore, necessary measures should be taken to test the wells with respect to arsenic.