Water Arsenic Concentrations Research Articles

A catchment-scale model of river water quality by Machine Learning

Water quality is a concern in most river basins worldwide due to the widespread release of pollutants which impacts the freshwater ecosystems. Exploring the relationships between drivers and water quality parameters at the regional scale is key in the identification of appropriate actions for the reduction of water pollution. Regional models are the appropriate tool to achieve this, though their development poses relevant challenges because of the complexity and non-linearity of such relationships. Among the available approaches, Machine Learning (ML) is promising because of its capability to detect complex nonlinear relationships and flexibility in the parameterization, which is learned from data. In this work, we developed regional models of water temperature, dissolved oxygen, arsenic, sulfate and chloride concentrations, as well as electrical conductivity, by using two ML algorithms, Random Forest and Deep feed-forward Neural Network, and compared their performances against the standard Linear Regression model. Our results indicate that the two ML algorithms are much more accurate models for such variables than the classical Linear Regression model, with Deep feed-forward Neural Network being the most effective in identifying the reciprocal importance of the drivers and capturing nonlinear relationships between drivers and water quality variables. Our analysis also revealed that the Julian day and year at which the sample was taken surrogate the air temperature in modeling water temperature and dissolved oxygen, with only a slight performance reduction. Arsenic, sulfate, and chloride show more complex behaviors in which geogenic and anthropogenic sources are intertwined. Dilution exerts a role chiefly for arsenic concentration, which suggests a non-uniform, in space, geogenic origin for this variable.

The impact of prenatal and early-life arsenic exposure on epigenetic age acceleration among adults in Northern Chile.

Exposure to arsenic affects millions of people globally. Changes in the epigenome may be involved in pathways linking arsenic to health or serve as biomarkers of exposure. This study investigated associations between prenatal and early-life arsenic exposure and epigenetic age acceleration (EAA) in adults, a biomarker of morbidity and mortality. DNA methylation was measured in peripheral blood mononuclear cells (PBMCs) and buccal cells from 40 adults (median age = 49 years) in Chile with and without high prenatal and early-life arsenic exposure. EAA was calculated using the Horvath, Hannum, PhenoAge, skin and blood, GrimAge, and DNA methylation telomere length clocks. We evaluated associations between arsenic exposure and EAA using robust linear models. Participants classified as with and without arsenic exposure had a median drinking water arsenic concentration at birth of 555 and 2 μg/l, respectively. In PBMCs, adjusting for sex and smoking, exposure was associated with a 6-year PhenoAge acceleration [B (95% CI) = 6.01 (2.60, 9.42)]. After adjusting for cell-type composition, we found positive associations with Hannum EAA [B (95% CI) = 3.11 (0.13, 6.10)], skin and blood EAA [B (95% CI) = 1.77 (0.51, 3.03)], and extrinsic EAA [B (95% CI) = 4.90 (1.22, 8.57)]. The association with PhenoAge acceleration in buccal cells was positive but not statistically significant [B (95% CI) = 4.88 (−1.60, 11.36)]. Arsenic exposure limited to early-life stages may be associated with biological aging in adulthood. Future research may provide information on how EAA programmed in early life is related to health.

The Arsenic-Antimony Creek at Sauerbrunn/Burgenland, Austria: A Toxic Habitat for Amphibians.

(1) Background: All Austrian amphibians are affected by the degradation of habitats. Mining contributes to habitat destruction by the formation of spoil heaps and mine drainage waters. In Stadtschlaining/Burgenland, antimony mining led to increased arsenic (As) and antimony (Sb) concentrations in soil and water. This study investigates a contaminated creek, still inhabited by amphibians. (2) Methods: Water and soil were analyzed along the creek and correlated with the occurrence of amphibians. (3) Results: As and Sb were increased, with up to 49,000 mg/kg As and 2446 mg/kg Sb in the soil. Up to 317 mg/kg As and 156 mg/kg Sb became bioavailable under gastric, and up to 298 mg/kg As and 30 mg/kg Sb under intestinal conditions, and were absorbed upon ingestion of soil. Larvae of Salamandra salamandra were found throughout the creek; survival rates were low. Rana temporaria occurs in the most contaminated sections but does not propagate here. Bombina variegata appears occasionally. Amphibians seem not to be able to detect and avoid metal or metalloid contamination. (4) Conclusion: Survival of larvae is dubious, but adult amphibians survive without apparent damage under severe metalloid contamination.

Assessment of Arsenic in Hair of the Inhabitants of East Croatia—Relationship to Arsenic Concentrations in Drinking Water

The problem of elevated arsenic concentrations in water and environment is an increasing public health concern. The aim of the study was to assess the arsenic content in human hair in selected areas of eastern Croatia and to compare them with measured values after installation of a new water supply system. The hair samples were taken in the areas of wider Osijek and Vinkovci area and analyzed using the ICP–MS method. These data were also compared with data for Vinkovci previously published in 2004. Depending on the investigated area, the median concentrations ranged from 0.02 to 0.9 µg g−1, whereby this last value exceeded the upper range of the reference value (0.319 µg g−1). The arsenic concentrations from the Našice, Osijek and Vinkovci areas were within or slightly above the maximum allowed reference range. The highest median values in hair samples were detected in Čepin, with arsenic-contaminated potable water, while in areas where the water source was changed, the values were significantly lower. The results add to the conclusion that there has been significant reduction in hair arsenic concentrations in the population that was given access to clean, uncontaminated water from other regional sources.

Arsenic and uranium contamination of Orog Lake in the Valley of Gobi Lakes, Mongolia: Field evidence of conservative accumulation of U in an alkaline, closed-basin lake during evaporation

The shrinkage of inland, alkaline, and saline lakes has caused the elevation of arsenic and uranium concentrations in lake water. However, the chemical reactions associated with these enrichments remain unclear. We conducted a five-year study of the water chemistry of Orog Lake (Mongolia) and the chemical and spectroscopic characteristics of the sediment to determine the geochemical behavior of arsenic and uranium during evaporation. The arsenic and uranium concentrations increased as evaporation caused the lake to shrink. The maximum concentrations of arsenic and uranium exceeded 200 µg/L and 600 µg/L, respectively, when the lake area was the smallest. Comparisons of the monitoring results with predictions of geochemical modeling suggested that some arsenic was removed from the lake water under highly desiccated conditions. Sequential extraction and X-ray absorption near-edge structure analyses showed that ferrihydrite can take up As(V). The accumulation of uranium could be reproduced by considering only evaporation. The conservative behavior of uranium can be explained by the low affinity of U(VI) for carbonate and ferrihydrite at pH > 9 and high dissolved inorganic carbon concentrations. The ubiquitous formation of extremely soluble U-bearing salts after the complete desiccation of inland lakes may thus become a serious threat to limnetic ecosystems.

Health effects and metabolic pathway of arsenic in children

Our six years of field experience in Bangladesh showed that normally children under 11 years of age do not show arsenical skin manifestations. However, we have observed a few exceptions when (1) the arsenic content in water consumed by children is very high (≥1,000 µg/L) and (2) the arsenic content is not very high, but the children get poor nutrition. It appears that although 6.12% of 4,864 children showed arsenic skin lesions but hair and nail analysis of children (below 11 years) with or without arsenical skin lesions from affected villages of Bangladesh showed that 84% of the children had arsenic in hair more than the toxic level and 89% in nail above normal level. It appears that children living in arsenic affected villages have higher arsenic body burden but less dermatological symptoms. The value of arsenic excretion and arsenic intake per kg of body weight ratio for adults is 0.53 while that of the children is 0.69. This indicates total arsenic excretion is higher for children per kg of body weight than adults. The average values (n = 18) for speciation of arsenic in children urine are 15.60% In-As, 10.64% MMA, and 73.76% DMA. Overall percentage of MMA is higher, and DMA is lower in adults than children (average % MMA is 17.20 vs. 10.64 and % DMA is 64.62 vs. 73.76%, respectively). Therefore, the 2nd methylation step (MMA to DMA) could be more active in children than adults. The results indicate that the first reaction of the metabolism pathway is more active in adults than children, basically in adult’s male. Also shows a significant (t-test positive) increase in the values of the DMA/MMA ratio in children compared to adults of the exposed group (8.15 vs. 4.11, respectively). Moreover, it is also observed that the second methylation step in the arsenic metabolic pathway is more active in children than adults. Because there is no significant difference of the values of MMA/iAs ratio, but the values of DMA/MMA ratio are significantly different between adults and children of the exposed group (0.92 vs. 0.73 for MMA/Asi and 4.11 vs 8.15 for DMA/MMA, respectively). Thus, from these results we may conclude that children retain arsenic shorter in their body comparing adults.

Assessment of groundwater arsenic contamination using machine learning in Varanasi, Uttar Pradesh, India.

This paper presents a machine learning approach for classification of arsenic (As) levels as safe and unsafe in groundwater samples collected from the Indo-Gangetic region. As water is essential for sustaining life, heavy metals like arsenic pose a public health concern. In this study, various tree-based machine learning models namely Random Forest, Optimized Forest, CS Forest, SPAARC, and REP Tree algorithms have been applied to classify water samples. As per the guidelines of the World Health Organization (WHO), the arsenic concentration in water should not exceed 10 μg/L. The groundwater quality parameter was ranked using a classifier attribute evaluator for training and testing the models. Parameters obtained from the confusion matrix, such as accuracy, precision, recall, and FPR, were used to analyze the performance of models. Among all models, Optimized Forest outperforms other classifier as it has a high accuracy of 80.64%, a precision of 80.70%, recall of 97.87%, and a low FPR of 73.33%. The Optimized Forest model can be used to test new water samples for classification of arsenic in groundwater samples.

Arsenic concentrations in soil, water, and rice grains of rice-growing areas of Punjab, Pakistan: multivariate statistical analysis.

Arsenic (As), a class-A human carcinogen, is ubiquitously present in the earth's crust and soil and may enter the air, water, and surface environments through different natural and anthropogenic sources. In this experiment, soil, irrigation water, and rice grains were sampled from conventional rice-growing areas of Punjab, Pakistan. Soil samples were collected from 0 to 15 cm surface soil of rice growing fields, and rice grains were collected from the same field at crop maturity. Irrigation water samples were collected from the source used to irrigate the respective rice fields. Coordinates of sampling locations were noted using a global positioning system, and a locations map was made using ArcGIS. Soil samples were digested in a microwave digester using aqua regia, and plant samples were block digested using nitric acid. Arsenic concentration was determined using an inductively coupled plasma mass spectrometer coupled with an auto-sampler and integrated samples introduction system. The mean concentration of As in rice grains, soil, and water samples was found within the safe limit set by WHO except for a sample from Narowal (148.54 µg l-1) that exceeded the irrigation water standard limit, i.e., 100 µg l-1 for irrigation water. Principal component analysis was performed to reduce the multidimensional space of variables and samples. Through the calculations of estimated daily intake, it has been revealed that the As levels measured in this study would only contribute a small amount (less than 5%) of the total recommended daily intake allowance.

Arsenic in private well water and birth outcomes in the United States

BackgroundPrenatal exposure to drinking water with arsenic concentrations >50 μg/L is associated with adverse birth outcomes, with inconclusive evidence for concentrations ≤50 μg/L. In a collaborative effort by public health experts, hydrologists, and geologists, we used published machine learning model estimates to characterize arsenic concentrations in private wells—federally unregulated for drinking water contaminants—and evaluated associations with birth outcomes throughout the conterminous U.S. MethodsUsing several machine learning models, including boosted regression trees (BRT) and random forest classification (RFC), developed from measured groundwater arsenic concentrations of ∼20,000 private wells, we characterized the probability that arsenic concentrations occurred within specific ranges in groundwater. Probabilistic model estimates and private well usage data were linked by county to all live birth certificates from 2016 (n = 3.6 million). We evaluated associations with gestational age and term birth weight using mixed-effects models, adjusted for potential confounders and incorporated random intercepts for spatial clustering. ResultsWe generally observed inverse associations with term birth weight. For instance, when using BRT estimates, a 10-percentage point increase in the probability that private well arsenic concentrations exceeded 5 μg/L was associated with a −1.83 g (95% CI: −3.30, −0.38) lower term birth weight after adjusting for covariates. Similarly, a 10-percentage point increase in the probability that private well arsenic concentrations exceeded 10 μg/L was associated with a −2.79 g (95% CI: −4.99, −0.58) lower term birth weight. Associations with gestational age were null. ConclusionIn this largest epidemiologic study of arsenic and birth outcomes to date, we did not observe associations of modeled arsenic estimates in private wells with gestational age and found modest inverse associations with term birth weight. Study limitations may have obscured true associations, including measurement error stemming from a lack of individual-level information on primary water sources, water arsenic concentrations, and water consumption patterns.

Investigation of Heavy Metals Including Arsenic (As) Concentration in Underground Water of Agra City using Arsenic Hydride System by Atomic Absorption Spectrometer and also Application of Geo Spatial Technology

Water Plays a significant role in our life. It serves the purpose of various Human activities such as irrigation, electricity, generation, industrial production etc. Water requirement in Uttar Pradesh is continually on the rise. In India ground water is being used as raw or untreated water for 85% of the public Supply of water varies widely from region to region and country to country. The prime requirement for sustainable development of a region is its water quality especially underground water. To check groundwater and sort out the contaminated region is economically very significant for the development of the area...Currently the potable water woes are global problem. This paper focuses on the ground water contamination of Agra city. It was selected for its importance as a popular tourist destination worldwide. The large number of tourists coming here use its water, therefore it is imperative that its water quality be monitored regularly. The present study is of mid-monsoon season 2018. For these 15 samples were collected using handheld GPS from randomly selected stations from different wards having easy access for regular sampling. The drinking water in Agra city is assessed for the following 8 parameters namely, pH, conductance, total dissolved solids (TDS) and heavy metals like Cu, Cr, Zn, Pb and As. and it is found that the concentration of various parameters is not within the permissible limit of water quality prescribed by WHO and CPCB. A GIS database of the measured spatial and water quality data is developed using QGIS3.2 and ground water quality maps are also prepared which will be helpful in monitoring the ground water quality of the status of the study area.

Application of fingernail samples as a biomarker for human exposure to arsenic-contaminated drinking waters

This study evaluated the relationship between arsenic uptake via drinking water ingestion and arsenic concentration in fingernails as a biomarker for human exposure. For this purpose, we collected fingernail samples from 40 healthy participants of arsenic-affected rural regions of Kaboudrahang County, the west of Iran. A total of 49 fingernail samples were also collected from individuals who lived in areas where contamination of drinking water sources with arsenic had not been reported. It was found that the fingernails arsenic contents in 50 and 4.08% of the samples collected from arsenic-contaminated and reference villages were higher than the normal arsenic values of nails (0.43–1.08 µg/g), respectively. Based on the results of adjusted multiple linear regression, a significant association was found between groundwater and fingernails arsenic concentration (p < 0.001). Moreover, a statistically significant association was shown between arsenic in the fingernail samples and gender (p = 0.037). Fingernails arsenic contents were not significantly affected by other variables including age, smoking habits, and BMI (p > 0.05). In light of the results of this study, the use of biological indicators such as fingernail tissues due to easier sampling and less risk of external contamination is suitable for assessing exposure to heavy metals in contaminated areas.

Ambient UVR and Environmental Arsenic Exposure in Relation to Cutaneous Melanoma in Iowa.

Intermittent sun exposure is the major environmental risk factor for cutaneous melanoma (CM). Cumulative sun exposure and other environmental agents, such as environmental arsenic exposure, have not shown consistent associations. Ambient ultraviolet radiation (UVR) was used to measure individual total sun exposure as this is thought to be less prone to misclassification and recall bias. Data were analyzed from 1096 CM cases and 1033 controls in the Iowa Study of Skin Cancer and Its Causes, a population-based, case-control study. Self-reported residential histories were linked to satellite-derived ambient UVR, spatially derived environmental soil arsenic concentration, and drinking water arsenic concentrations. In men and women, ambient UVR during childhood and adolescence was not associated with CM but was positively associated during adulthood. Lifetime ambient UVR was positively associated with CM in men (OR for highest vs. lowest quartile: 6.09, 95% confidence interval (CI) 2.21–16.8), but this association was not as strong among women (OR for highest vs. lowest quartile: 2.15, 95% CI 0.84–5.54). No association was detected for environmental soil or drinking water arsenic concentrations and CM. Our findings suggest that lifetime and adulthood sun exposures may be important risk factors for CM.

Arsenic Mineral in Volcanic Tuff, a Source of Arsenic Anomaly in Groundwater: City of Chihuahua, Mexico

Arsenic is a naturally occurring trace element that causes many health effects when present in drinking water. Elevated arsenic concentrations in water are often attributed to nearby felsic volcanic sequences; however, the specific rock units to which the groundwater anomalies can be accredited are rarely identified. The groundwater from wells around the city of Chihuahua, Mexico, contains high arsenic content. Arsenic in groundwater increases toward the base rock containing Tertiary volcanic rocks. Through detailed scanning electron microscope (SEM) and electron microprobe (EMP) work, arsenic minerals are identified in the cavities of the Tertiary volcanic tuff from the northeast part of the Tabalaopa Basin, city of Chihuahua. Arsenic minerals, the As–Sr–Al phase (a possible arsenogoyazite–arsenoflorencite group mineral) crystallized in the vesicles of the tuff and the As–Y bearing phase included in biotite, prevail in the studied Tertiary volcanic outcrops. Based on the current study, the arsenic anomaly in the Tabalaopa–Aldama aquifer corresponds to these arsenic phases in the Tertiary volcanic rocks.

Determination of Arsenic Content in Water Using a Silver Coordination Polymer.

In this report, we describe a practical method for the colorimetric determination of dissolved inorganic arsenic content in water samples, using a silver coordination polymer as the sensing material. We demonstrate that a crystalline polymer framework can be used to stabilize silver(I) ions, greatly reducing both photosensitivity and water solubility, while still affording sufficient reactivity to detect arsenic in water samples at low parts-per-billion (ppb) levels. Test strips fabricated with the silver-based polymer are shown to be effective for field tests of groundwater under real-world operating conditions and display performance that is competitive with commercially available mercury-based test strips. Spectroscopic methods are also used to probe the reaction products formed, in order to better understand the sensing mechanism. Thus, our work provides the foundation for an improved field test that could be deployed to help manage groundwater usage in regions where arsenic contamination is problematic but sophisticated lab testing is not readily available.

Concentration level of arsenic in agricultural soil and surface water used for irrigation in Bukuru, JOS- south LGA of plateau state, Nigeria

Arsenic concentration of agricultural soil and surface water used for irrigation were surveyed in two abandoned mining sites of Jos South Local Government Area. DB-Zang and Dorowa total dissolved solid, total hardness, electrical conductivity, temperature and pH of the agricultural soil and surface water were determined according to standard procedure. Result indicates that Total dissolve solids in W1 was 156±2.00mg/L and for W2 (160±2.00mg/L), total hardness W1 (35.20±4.70mg/L) and W2 (44.67±4.70mg/L), electrical conductivity for W1 was 0.240±0.189µs/cm and W2 was 0.120±0.189µs/cm ,electrical conductivity for S1 (0.49±0.16µs/cm), S2 (0.17±0.16µs/cm), temperature for both water was 28.00±0.00oC for soil are 18.00±0.00 o C, pH for W1 (7.10±0.05) and W2 (7.20±0.05), pH for S1 (6.90±0.15) S2 ( 6.60±0.15). The concentration of Arsenic in soil L2 is14.00±0.70µg/kg which is in agreement with WHO recommended level of Arsenic in soil and for L1 257.00±120.00µg/kg which is not in agreement with the WHO recommended level of arsenic, while in water for L1 was 3.00±0.50µg/L which is not in agreement with the WHO recommended level of arsenic and L2 was 48.00±0.70µg/L which is not in agreement with the WHO recommended level of arsenic. The cultivation of food crops in those areas are not recommended.  Â

Multiple environmental benefits of alternate wetting and drying irrigation system with limited yield impact on European rice cultivation: The Ebre Delta case

The AWD is an irrigation technology for rice cultivation, consisting in implementing alternate draining and flooded periods over the growing season, that delivers multiple environmental benefits, such as reduced water consumption, CH4 emissions and arsenic (As) grain content, but can be offset by yield losses. The trade-offs between the agronomic and environmental effects of AWD are crop context-dependent and they also vary among the different versions of AWD studied. Therefore, the implementation of a safe AWD needs to be preceded by studies conducted within a specific rice cropping system. A two-year field experiment was conducted to assess the effect of AWD on grain yield, As and heavy metal content in grains, and greenhouse gas emissions in nine representative European rice cultivars grown in a Mediterranean growing area. The experiment was performed in a split-plot design with four replications. The study revealed a significant cultivar effect on the agronomic response to AWD. Among the studied cultivars, one of them performed as tolerant to AWD while a group formed by four cultivars showed slight non-significant yield decline. AWD significantly reduced CH4 emissions and the global warming potential by 90% being such a large mitigation capacity explained by the negligible N2O emissions found in both water treatments. Finally, the implementation of AWD significantly reduced by ca. 40% As grain concentration but increased cadmium content, though the levels remained below the recommended thresholds. Further, AWD increased key nutritional elements like cupper, selenium, and zinc. In conclusion, this study confirms that AWD can be safely implemented in Mediterranean rice cultivation conditions with limited or null yield impact while obtaining the associated environmental benefits of this practice

Arsenic Secondary Methylation Capacity Is Inversely Associated with Arsenic Exposure-Related Muscle Mass Reduction.

Skeletal muscle mass reduction has been implicated in insulin resistance (IR) that promotes cardiometabolic diseases. We have previously reported that arsenic exposure increases IR concomitantly with the reduction of skeletal muscle mass among individuals exposed to arsenic. The arsenic methylation capacity is linked to the susceptibility to some arsenic exposure-related diseases. However, it remains unknown whether the arsenic methylation capacity affects the arsenic-induced reduction of muscle mass and elevation of IR. Therefore, this study examined the associations between the arsenic methylation status and skeletal muscle mass measures with regard to IR by recruiting 437 participants from low- and high-arsenic exposure areas in Bangladesh. The subjects’ skeletal muscle mass was estimated by their lean body mass (LBM) and serum creatinine levels. Subjects’ drinking water arsenic concentrations were positively associated with total urinary arsenic concentrations and the percentages of MMA, as well as inversely associated with the percentages of DMA and the secondary methylation index (SMI). Subjects’ LBM and serum creatinine levels were positively associated with the percentage of DMA and SMI, as well as inversely associated with the percentage of MMA. HOMA-IR showed an inverse association with SMI, with a confounding effect of sex. Our results suggest that reduced secondary methylation capacity is involved in the arsenic-induced skeletal muscle loss that may be implicated in arsenic-induced IR and cardiometabolic diseases.

Assessment of Arsenic Levels in Water, Sediment, and Human Hair around Ie Seu’um Geothermal Manifestation Area, Aceh, Indonesia

The concentration of arsenic in water, sediment, and resident hair in the Ie Seu’um geothermal manifestation area has been analyzed using the Atomic Graphite Furnace Atomic Absorption Spectrophotometry (GF-AAS) method. Sediment and hair samples were prepared by wet digestion using an acid solution. The measurement results were validated by linearity, Limit of Detection (LoD), Limit of Quantification (LoQ), Relative Standard Deviation (%RSD), and %Recovery. The validation test showed that this method is very linear, sensitive, accurate, and precise with a correlation coefficient of 0.9999, LoD of 0.009 μg/L, LoQ of 0.027 μg/L, recovery values of 89.117–101.027% for hair samples and 88.337–105.175% for sediment samples, and RSD of 1.067%. The sample test results showed that the hot springs contained the highest arsenic with levels of 166.73 ± 0.0081 μg/L (IS1). In comparison, the water samples with the lowest arsenic levels were in the rivers that had not been in direct contact with the hot water (IS2) flow, which is 0.80 ± 0.0036 μg/L. All the river water samples that had been in contact with hot water were boreholes, and the resident boreholes located around hot water streams/rivers contaminated with arsenic were above the threshold. Only the river water that had not been in contact with hot water, refill water, and borehole waters outside the hot water flow were detected to be below the threshold level. All the sediment samples showed arsenic contamination, with levels ranging from 2.56–6.86 mg/kg, and it was still within the normal limits recommended by the National Oceanic and Atmospheric Administration (NOAA). Arsenic exposures in communities living around the Ie Seu’um geothermal area, Mesjid Raya Sub-District, Aceh Besar District, Aceh Province, were very high, where 9 out of 10 respondents were positive for arsenic with levels ranging from 54.59–164.57 mg/kg, which was already above the threshold set by the researchers.

Increased arsenic levels in both environmental measurements and biomonitoring results are associated with elevated risk of spina bifida

BACKGROUND AND AIM: Arsenic is associated with multiple adverse reproductive outcomes, and previous studies suggested higher risk of neural tube defects among mothers exposed to higher concentration of well water arsenic in Bangladesh. We further examine the association using water arsenic as proxy for external exposure and toenail as biomarkers for internal dose. METHODS: Parental toenail and water arsenic concentrations were examined in a case-control study in National Institute of Neurosciences & Hospital, Dhaka, Bangladesh. The associations between log-transformed and percentile arsenic concentrations and physician-diagnosed spina bifida were evaluated with logistic regression and cluster analysis, adjusted for maternal age, maternal BMI, parity, educational level, folic acid use and second-hand smoke exposure during pregnancy and weighted by self-reported dietary patterns. RESULTS:Median concentration for water, maternal and paternal arsenic are 2.0 ppb, 0.4 and 0.5 microgram per gram toenail among 280 included child-parent trios (156 with spina bifida) with complete exposure data. We observed associations between highest quartile maternal arsenic levels, higher than 10 ppb arsenic in water and spina bifida risk for their children after weighted for diet (Adjusted OR for water arsenic=1.49, 95% CI=1.00-2.06; adjusted OR for maternal arsenic=1.57, 95% CI=1.10-2.24), and higher composite exposure in both hierarchical clustering and k-means clustering were also associated with increased risk after weighting. Effect heterogeneity was observed between different folic acid supplement conditions, in which dose-response was attenuated for both water and paternal concentrations. CONCLUSIONS:Prenatal inorganic arsenic exposure was associated with elevated risk of spina bifida in Bangladesh, and joint parental exposure is associated with a higher risk. Investigations and interventions to mitigate arsenic exposure during for pregnant women are warranted. KEYWORDS: Heavy metals, birth outcomes, children's environmental health

Chlorination by-products in drinking water and risk of bladder cancer – a population-based cohort study

BACKGROUND AND AIM: Exposure to chlorination by-products has been consistently associated with an increased risk of bladder cancer in case-control studies, but confirmation from large-scale cohort studies are lacking. We assessed the association of drinking water trihalomethanes (THM), a surrogate for chlorination by-products, with risk of bladder cancer in 58,672 men and women in two population-based cohorts. METHODS: We used data, including questionnaire information, from the Swedish Infrastructure for Medical Population-Based Life-Course and Environmental Research (SIMPLER). Individual exposure to THM was assessed by combining residential information from register with municipal THM monitoring data. Participants were categorized into no chlorination, low (15 µg/L) or high (15 µg/L) THM exposure dependent on their area of residence. Incident bladder cancer cases were ascertained from 1998 through 2019 via register linkage. Associations were examined using multivariable-adjusted Cox proportional hazards regression models, including information on smoking habits and drinking water arsenic concentrations. RESULTS:The mean THM concentration was 6.6 ± 2.2 µg/L and 17.1 ± 2.1 µg/L in the low and the high exposure category, respectively. During a mean follow-up of 16 years (965,590 person-years), 831 bladder cancer cases were ascertained. We observed no overall association of THM with risk of bladder cancer. The hazard ratio was 0.90 (95% confidence interval: 0.73 – 1.11) when comparing the highest exposed group with those in the non-chlorinated areas. The null association remained after restricting the analysis to long-term residents and across strata of smoking status and cancer stage. CONCLUSIONS:Our results suggest that at THM concentrations below 20 µg/L, which is representative of chlorinated drinking waters in most European countries, chlorination by-product exposure is not associated with risk of bladder cancer. KEYWORDS: Chlorination by-products, Disinfection by-products, Trihalomethanes, Bladder cancer, Water quality, Drinking water