A seasonal study of arsenic in groundwater, Snohomish County, Washington, USA

Human Health Risk Assessment of Elevated Fe and Mn Intake in Groundwater in Yangtze Catchment

Globally, it has been reported that groundwater contains elevated levels of Fe and Mn. However, the risk of prolonged exposure to groundwater with elevated Fe and Mn was often ignored due to their much lower carcinogenic risk. To assess the human health risk of elevated Fe and Mn intake in groundwater, 1863 groundwater samples from the Yangtze catchment, a densely populated and economically prosperous area of China, were collected in this study. The spatial distributions of Fe and Mn in groundwater were investigated by the geographic information system (GIS) and their health risk assessment was done. The results indicated that 38.6% and 50.3% of the groundwater samples were defined as "elevated/high" levels for Fe and Mn, respectively, exceeding 0.3 and 0.1 mg/L (World Health Organization guidelines). Moreover, in the groundwater of Yangtze Catchment, the order of Fe and Mn contents is followed by upper< middle< lower. Based on the calculated hazard index (HI), HIadult and HIchild were in a range of 0-4.91 and 0-11.07, respectively. There was an area of 3,483 and 35,523 km2 with a non-carcinogenic risk from Fe and Mn, correspondingly. The numbers of affected adults and children were about 3,018,066 and 2,775,007, respectively. It means that 0.20% and 2.00% of the study area or 0.64% and 0.59% of the total population will suffer health risks from Fe and Mn intake in groundwater, respectively. Therefore, a significant basis for groundwater safety in the Yangtze catchment and similar areas was provided in this study.

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

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

Scenario, perspectives and mechanism of arsenic and fluoride Co-occurrence in the groundwater: A review

Arsenic (As) and fluoride (F^-) are the two most conspicuous contaminants, in terms of distribution and menace, in aquifers around the world. While the majority of studies focus on the individual accounts of their hydro-geochemistry, the current work is an effort to bring together the past and contemporary works on As and F^- co-occurrence. Co-occurrence in the context of As and F^- is a broad umbrella term and necessarily does not imply a positive correlation between the two contaminants. In arid oxidized aquifers, healthy relationships between As and F^- is reported owing desorption based release from the positively charged (hydr)oxides of metals like iron (Fe) under alkaline pH. In many instances, multiple pathways of release led to little or no correlation between the two, yet there were high concentrations of both at the same time. The key influencer of the strength of the co-occurrence is seasonality, environment, and climatic conditions. Besides, the existing primary ion and dissolved organic matter also affect the release and enrichment of As-F^- in the aquifer system. Anthropogenic forcing in the form of mining, irrigation return flow, extraction, recharge, and agrochemicals remains the most significant contributing factor in the co-occurrence. The epidemiological indicate that the interface of these two interacting elements concerning public health is considerably complicated and can be affected by some uncertain factors. The existing explanations of interactions between As-F are indecisive, especially their antagonistic interactions that need further investigation. "Multi-contamination perspectives of groundwater" is an essential consideration for the overarching question of freshwater sustainability.

Prolonged exposure to arsenic in UK private water supplies: toenail, hair and drinking water concentrations

Chronic exposure to arsenic (As) in drinking water is an established cause of cancer and other adverse health effects. Arsenic concentrations >10 μg L(-1) were previously measured in 5% of private water supplies (PWS) in Cornwall, UK. The present study investigated prolongued exposure to As by measuring biomarkers in hair and toenail samples from 212 volunteers and repeated measurements of As in drinking water from 127 households served by PWS. Strong positive Pearson correlations (rp = 0.95) indicated stability of water As concentrations over the time period investigated (up to 31 months). Drinking water As concentrations were positively correlated with toenail (rp = 0.53) and hair (rp = 0.38) As concentrations - indicative of prolonged exposure. Analysis of washing procedure solutions provided strong evidence of the effective removal of exogenous As from toenail samples. Significantly higher As concentrations were measured in hair samples from males and smokers and As concentrations in toenails were negatively associated with age. A positive association between seafood consumption and toenail As and a negative association between home-grown vegetable consumption and hair As was observed for volunteers exposed to <1 As μg L(-1) in drinking water. These findings have important implications regarding the interpretation of toenail and hair biomarkers. Substantial variation in biomarker As concentrations remained unaccounted for, with soil and dust exposure as possible explanations.

Technological options for the removal of arsenic with special reference to South East Asia

Arsenic contamination in ground water, used for drinking purpose, has been envisaged as a problem of global concern. However, arsenic contamination of ground water in parts of South East Asia is assuming greater proportions and posing a serious threat to the health of millions of people. A variety of treatment technologies based on oxidation, co-precipitation, adsorption, ion exchange and membrane process are available for the removal of arsenic from ground water. However, question remains regarding the efficiency and applicability/appropriateness of the technologies, particularly because of low influent arsenic concentration and differences in source water composition. Some of these methods are quite simple, but the disadvantage associated with them is that they produce large amounts of toxic sludge, which needs further treatment before disposal into the environment. Besides, the system must be economically viable and socially acceptable. In this paper an attempt has been made to review and update the recent advances made in the technological development in arsenic removal technologies to explore the potential of those advances to address the problem of arsenic contamination in South East Asia.

Water quality monitoring records for estimating tap water arsenic and nitrate: a validation study

BACKGROUND

Tap water may be an important source of exposure to arsenic and nitrate. Obtaining and analyzing samples in the context of large studies of health effects can be expensive. As an alternative, studies might estimate contaminant levels in individual homes by using publicly available water quality monitoring records, either alone or in combination with geographic information systems (GIS).

METHODS

We examined the validity of records-based methods in Washington State, where arsenic and nitrate contamination is prevalent but generally observed at modest levels. Laboratory analysis of samples from 107 homes (median 0.6 microg/L arsenic, median 0.4 mg/L nitrate as nitrogen) served as our "gold standard." Using Spearman's rho we compared these measures to estimates obtained using only the homes' street addresses and recent and/or historical measures from publicly monitored water sources within specified distances (radii) ranging from one half mile to 10 miles.

RESULTS

Agreement improved as distance decreased, but the proportion of homes for which we could estimate summary measures also decreased. When including all homes, agreement was 0.05-0.24 for arsenic (8 miles), and 0.31-0.33 for nitrate (6 miles). Focusing on the closest source yielded little improvement. Agreement was greatest among homes with private wells. For homes on a water system, agreement improved considerably if we included only sources serving the relevant system (rho = 0.29 for arsenic, rho = 0.60 for nitrate).

CONCLUSIONS

Historical water quality databases show some promise for categorizing epidemiologic study participants in terms of relative tap water nitrate levels. Nonetheless, such records-based methods must be used with caution, and their use for arsenic may be limited.

Temporal variability of groundwater chemistry in shallow and deep aquifers of Araihazar, Bangladesh

Samples were collected every 2-4 weeks from a set of 37 monitoring wells over a period of 2-3 years in Araihazar, Bangladesh, to evaluate the temporal variability of groundwater composition for As and other constituents. The monitoring wells are grouped in 6 nests and span the 5-91 m depth range. Concentrations of As, Ca, Fe, K, Mg, Mn, Na, P, and S were measured by high-resolution ICPMS with a precision of 5% or better; concentrations of Cl were measured by ion chromatography. In shallow wells <30 m deep, As and P concentrations generally varied by <30%, whereas concentrations of the major ions (Na, K, Mg, Ca and Cl) and the redox-sensitive elements (Fe, Mn, and S) varied over time by up to +/-90%. In wells tapping the deeper aquifers >30 m often below clay layers concentrations of groundwater As were much lower and varied by <10%. The concentrations of major cations also varied by <10% in these deep aquifers. In contrast, the concentration of redox-sensitive constituents Fe, S, and Mn in deep aquifers varied by up to 97% over time. Thus, strong decoupling between variations in As and Fe concentrations is evident in groundwaters from shallow and deep aquifers. Comparison of the time series data with groundwater ages determined by (3)H/(3)He and (14)C dating shows that large seasonal or inter-annual variations in major cation and chloride concentrations are restricted to shallow aquifers and groundwater recharged <5 years ago. There is no corresponding change in As concentrations despite having significant variations of redox sensitive constituents in these very young waters. This is attributed to chemical buffering due to rapid equilibrium between solute and solid As. At two sites where the As content of groundwater in existing shallow wells averages 102 microg/L (range: <5 to 648 microg/L; n=118) and 272 microg/L (range: 10 to 485 microg/L; n=65), respectively, a systematic long-term decline in As concentrations lends support to the notion that flushing may slowly deplete an aquifer of As. Shallow aquifer water with >5 years (3)H/(3)He age show a constant As:P molar ratio of 9.6 over time, suggesting common mechanisms of mobilization.

Seasonal variation of arsenic concentration in wells in Nevada

The issue of seasonal arsenic measurement variability poses consequences regarding the interpretation and frequency of well water measurements for both public health research and surveillance. In this study, we evaluated seasonal variability in arsenic concentration in 356 wells in western Nevada. River flow data obtained from US Geological Survey National Water Information System were used to classify seasons as wet or dry, and mean differences in arsenic well concentrations measured during these seasons were compared. Arsenic concentrations in these wells averaged 72.9 microg/L (range, non-detect to 3000 microg/L). The mean difference in arsenic concentrations between the wet and dry seasons was -3.3 microg/L (p = 0.78; average percent difference = 2.3%). Eighty wells (22%) had higher arsenic concentrations in the wet season, 75 wells (21%) had higher arsenic concentrations in the dry season and no difference was seen in 201 wells (56%). The mean differences in wells with arsenic levels of 0-10, 11-50, 51-200, > 200 microg/L were -1.4 microg/L(p=0.43), 9.2 microg/L(p=0.36), 15.1 microg/L(p=0.30), and -49.9 microg/L(p=0.59). In summary, although changes in arsenic concentrations were seen in some wells, clear trends in arsenic concentration over time were not associated with the wet and dry seasons. These findings provide evidence that, in our study area as a whole, little seasonal variability occurs in arsenic concentrations, and repeated assessments of arsenic concentrations based on season might add little value to the accuracy of health effects research or public health surveillance.

Arsenic removal from water/wastewater using adsorbents--A critical review

Arsenic's history in science, medicine and technology has been overshadowed by its notoriety as a poison in homicides. Arsenic is viewed as being synonymous with toxicity. Dangerous arsenic concentrations in natural waters is now a worldwide problem and often referred to as a 20th-21st century calamity. High arsenic concentrations have been reported recently from the USA, China, Chile, Bangladesh, Taiwan, Mexico, Argentina, Poland, Canada, Hungary, Japan and India. Among 21 countries in different parts of the world affected by groundwater arsenic contamination, the largest population at risk is in Bangladesh followed by West Bengal in India. Existing overviews of arsenic removal include technologies that have traditionally been used (oxidation, precipitation/coagulation/membrane separation) with far less attention paid to adsorption. No previous review is available where readers can get an overview of the sorption capacities of both available and developed sorbents used for arsenic remediation together with the traditional remediation methods. We have incorporated most of the valuable available literature on arsenic remediation by adsorption ( approximately 600 references). Existing purification methods for drinking water; wastewater; industrial effluents, and technological solutions for arsenic have been listed. Arsenic sorption by commercially available carbons and other low-cost adsorbents are surveyed and critically reviewed and their sorption efficiencies are compared. Arsenic adsorption behavior in presence of other impurities has been discussed. Some commercially available adsorbents are also surveyed. An extensive table summarizes the sorption capacities of various adsorbents. Some low-cost adsorbents are superior including treated slags, carbons developed from agricultural waste (char carbons and coconut husk carbons), biosorbents (immobilized biomass, orange juice residue), goethite and some commercial adsorbents, which include resins, gels, silica, treated silica tested for arsenic removal come out to be superior. Immobilized biomass adsorbents offered outstanding performances. Desorption of arsenic followed by regeneration of sorbents has been discussed. Strong acids and bases seem to be the best desorbing agents to produce arsenic concentrates. Arsenic concentrate treatment and disposal obtained is briefly addressed. This issue is very important but much less discussed.

Human health effects from chronic arsenic poisoning--a review

The ill effects of human exposure to arsenic (As) have recently been reevaluated by government agencies around the world. This has lead to a lowering of As guidelines in drinking water, with Canada decreasing the maximum allowable level from 50 to 25 microg/L and the U.S. from 50 to 10 microg/L. Canada is currently contemplating a further decrease to 5 microg/L. The reason for these regulatory changes is the realization that As can cause deleterious effects at lower concentrations than was previously thought. There is a strong relationship between chronic ingestion of As and deleterious human health effects and here we provide an overview of some of the major effects documented in the scientific literature. As regulatory levels of As have been decreased, an increasing number of water supplies will now require removal of As before the water can be used for human consumption. While As exposure can occur from food, air and water, all major chronic As poisonings have stemmed from water and this is usually the predominant exposure route. Exposure to As leads to an accumulation of As in tissues such as skin, hair and nails, resulting in various clinical symptoms such as hyperpigmentation and keratosis. There is also an increased risk of skin, internal organ, and lung cancers. Cardiovascular disease and neuropathy have also been linked to As consumption. Verbal IQ and long term memory can also be affected, and As can suppress hormone regulation and hormone mediated gene transcription. Increases in fetal loss and premature delivery, and decreased birth weights of infants, can occur even at low (<10 microg/L) exposure levels. Malnourished people have been shown to be more predisposed to As-related skin lesions. A large percentage of the population (30-40%) that is using As-contaminated drinking water can have elevated As levels in urine, hair and nails, while showing no noticeable clinical symptoms, such as skin lesions. It is therefore important to carry out clinical tests of As exposure. Factors combining to increase/decrease the ill effects of As include duration and magnitude of As exposure, source of As exposure, nutrition, age and general health status. Analytical determinations of As poisoning can be made by examining As levels in urine, hair and toenails. Communities and individuals relying on groundwater sources for drinking water need to measure As levels to ensure that their supplies are safe. Communities with water As levels greater than 5 microg/L should consider a program to document As levels in the population.

The temporal stability of arsenic concentrations in well water in western Nevada

Millions of people worldwide are exposed to drinking water containing arsenic, and epidemiologic studies have identified associations between the ingestion of arsenic-contaminated water and increased risks of cancer. In many of these studies, the assessment of arsenic exposure is based on a limited number of drinking water measurements, and the assessment of long-term or past exposure relies on the assumption that arsenic concentrations in sources of drinking water remain stable over time. In this investigation, the temporal stability of arsenic concentration was assessed in 759 wells in western Nevada state in the USA. Arsenic concentrations in these wells ranged from nondetectable to 6200 microg/L (median, 10 microg/L; standard deviation, 335 microg/L). Spearman correlation coefficients between arsenic concentrations measured in the same wells over a period of 1--5, 6--10, and 11--20 years apart were, respectively, 0.84 [95% confidence interval (CI), 0.81--0.86), 0.85 (95% CI, 0.81--0.88), and 0.94 (95% CI, 0.88--0.96). These findings suggest that, in this study area, arsenic concentrations in most wells remain stable over time and a limited number of measurements per well can be used to predict arsenic exposures over a period of many years.

Removal of arsenic using hardened paste of Portland cement: batch adsorption and column study

Hardened paste of Portland cement (HPPC) has been used as a low-cost adsorbent for the removal of arsenic from water environment. Results from the batch experiments, conducted at an initial concentration of 0.2 ppm of arsenate, suggest arsenate removal up to 95%. Kinetic profiles were developed for various conditions. Effects of adsorbent dose, common ions such as Ca(2+), Mg(2+), Fe(3+), Fe(2+), Cl(-), SO(4)(2-), NO(3)(-), PO(4)(3-) and of pH were studied in detail. Adsorption isotherm studies revealed that the Freundlich isotherm was followed with a better correlation than the Langmuir isotherm. Arsenite could also be removed up to approximately 88% using the same material, HPPC. Finally, column studies were undertaken involving the new HPPC to check the suitability of the material for the removal of total arsenic content from water body. Kinetic experiments for the removal of arsenic by column studies revealed a film diffusion mechanism.

Chronic arsenic poisoning in the rat: treatment with combined administration of succimers and an antioxidant

The influence of the coadministration of vitamin C or vitamin E on the efficacy of two thiol chelators, meso-2,3-dimercaptosuccinic acid (DMSA) or monoisoamyl DMSA, in counteracting chronic arsenic toxicity was investigated in rats. Vitamin C and vitamin E were only mildly effective when given alone or in combination with the above chelators in mobilizing arsenic from the target tissues. However, combined administration of vitamin C plus DMSA and vitamin E plus MiADMSA led to a more pronounced depletion of brain arsenic. The supplementation of vitamins was significantly effective in restoring inhibition of blood delta-aminolevulinic acid dehydratase (ALAD) oxidative stress in liver, kidneys, and brain as reflected by reduced levels of thiobarbituric acid reactive substance and oxidized and reduced glutathione levels. The results thus lead us to suggest that coadministration of vitamin E or vitamin C may be useful in the restoration of altered biochemical variables (particularly the effects on heme biosynthesis and oxidative injury) although it has only a limited role in depleting arsenic burden.

Removal of arsenic from water using hardened paste of Portland cement

Portland cement has been used as a new low-cost adsorbent for the removal of arsenic from the water environment. In the batch experiments conducted at an initial concentration of 0.2 mg l(-1) of arsenate, it was found that up to 95% of arsenate could be removed. Kinetic profiles were developed for various conditions. The effect of adsorbent dose, effects of common ions such as Ca2+, Mg2+, Fe3+/Fe2+, Cl-, SO4(2-), NO3(-), PO4(3-) and the effect of pH was studied. Adsorption isotherm studies were performed and it was observed that the Freundlich isotherm was followed with a better correlation than the Langmuir isotherm. Arsenite could also be removed up to approximately 88% using the same material. A new detection method for arsenate/arsenite was developed for routine analysis of arsenic and used during the entire study.

Hardened paste of Portland cement--a new low-cost adsorbent for the removal of arsenic from water

Portland cement has been used as a low-cost adsorbent for the removal of arsenic from the water environment. In the batch experiments conducted at an initial concentration of 0.2 ppm of arsenate, it was found that arsenate could be removed up to 95%. Kinetic profiles were developed for various conditions. Effect of adsorbent dose. effects of common ions such as Ca(2+), Mg(2+), Fe(3+)/Fe(2+), Cl(-), SO4(2-), NO3(-), PO4(3-), and the effect of pH was studied. Adsorption isotherm studies were performed and it was observed that the Freundlich isotherm was followed with a better correlation than the Langmuir isotherm. Arsenite could also be removed up to approximately 88% using the same material. A new detection method for arsenate/arsenite was developed for routine analysis of arsenic and used during the entire study.