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Sci Total Environ ; 787: 147555, 2021 Sep 15.
Artigo em Inglês | MEDLINE | ID: mdl-33991916


Geogenic arsenic contamination typically occurs in groundwater as opposed to surface water supplies. Groundwater is a major source for many community water systems (CWSs) in the United States (US). Although the US Environmental Protection Agency sets the maximum contaminant level (MCL enforceable since 2006: 10 µg/L) for arsenic in CWSs, private wells are not federally regulated. We evaluated county-level associations between modeled values of the probability of private well arsenic exceeding 10 µg/L and CWS arsenic concentrations for 2231 counties in the conterminous US, using time invariant private well arsenic estimates and CWS arsenic estimates for two time periods. Nationwide, county-level CWS arsenic concentrations increased by 8.4 µg/L per 100% increase in the probability of private well arsenic exceeding 10 µg/L for 2006-2008 (the initial compliance monitoring period after MCL implementation), and by 7.3 µg/L for 2009-2011 (the second monitoring period following MCL implementation) (1.1 µg/L mean decline over time). Regional differences in this temporal decline suggest that interventions to implement the MCL were more pronounced in regions served primarily by groundwater. The strong association between private well and CWS arsenic in Rural, American Indian, and Semi Urban, Hispanic counties suggests that future research and regulatory support are needed to reduce water arsenic exposures in these vulnerable subpopulations. This comparison of arsenic exposure values from major private and public drinking water sources nationwide is critical to future assessments of drinking water arsenic exposure and health outcomes.

Arsênio , Água Potável , Água Subterrânea , Poluentes Químicos da Água , Arsênio/análise , Água Potável/análise , Monitoramento Ambiental , Estados Unidos , Poluentes Químicos da Água/análise , Abastecimento de Água , Poços de Água
Environ Sci Technol ; 55(8): 5012-5023, 2021 04 20.
Artigo em Inglês | MEDLINE | ID: mdl-33729798


Arsenic from geologic sources is widespread in groundwater within the United States (U.S.). In several areas, groundwater arsenic concentrations exceed the U.S. Environmental Protection Agency maximum contaminant level of 10 µg per liter (µg/L). However, this standard applies only to public-supply drinking water and not to private-supply, which is not federally regulated and is rarely monitored. As a result, arsenic exposure from private wells is a potentially substantial, but largely hidden, public health concern. Machine learning models using boosted regression trees (BRT) and random forest classification (RFC) techniques were developed to estimate probabilities and concentration ranges of arsenic in private wells throughout the conterminous U.S. Three BRT models were fit separately to estimate the probability of private well arsenic concentrations exceeding 1, 5, or 10 µg/L whereas the RFC model estimates the most probable category (≤5, >5 to ≤10, or >10 µg/L). Overall, the models perform best at identifying areas with low concentrations of arsenic in private wells. The BRT 10 µg/L model estimates for testing data have an overall accuracy of 91.2%, sensitivity of 33.9%, and specificity of 98.2%. Influential variables identified across all models included average annual precipitation and soil geochemistry. Models were developed in collaboration with public health experts to support U.S.-based studies focused on health effects from arsenic exposure.

Arsênio , Água Subterrânea , Poluentes Químicos da Água , Arsênio/análise , Monitoramento Ambiental , Humanos , Aprendizado de Máquina , Estados Unidos , Poluentes Químicos da Água/análise , Abastecimento de Água , Poços de Água
Environ Sci Technol ; 55(3): 1822-1831, 2021 02 02.
Artigo em Inglês | MEDLINE | ID: mdl-33439623


This study assesses the potential impact of drought on arsenic exposure from private domestic wells by using a previously developed statistical model that predicts the probability of elevated arsenic concentrations (>10 µg per liter) in water from domestic wells located in the conterminous United States (CONUS). The application of the model to simulate drought conditions used systematically reduced precipitation and recharge values. The drought conditions resulted in higher probabilities of elevated arsenic throughout most of the CONUS. While the increase in the probability of elevated arsenic was generally less than 10% at any one location, when considered over the entire CONUS, the increase has considerable public health implications. The population exposed to elevated arsenic from domestic wells was estimated to increase from approximately 2.7 million to 4.1 million people during drought. The model was also run using total annual precipitation and groundwater recharge values from the year 2012 when drought existed over a large extent of the CONUS. This simulation provided a method for comparing the duration of drought to changes in the predicted probability of high arsenic in domestic wells. These results suggest that the probability of exposure to arsenic concentrations greater than 10 µg per liter increases with increasing duration of drought. These findings indicate that drought has a potentially adverse impact on the arsenic hazard from domestic wells throughout the CONUS.

Arsênio , Água Subterrânea , Poluentes Químicos da Água , Arsênio/análise , Secas , Monitoramento Ambiental , Humanos , Estados Unidos , Poluentes Químicos da Água/análise , Abastecimento de Água , Poços de Água
Sci Total Environ ; 687: 1261-1273, 2019 Oct 15.
Artigo em Inglês | MEDLINE | ID: mdl-31412460


Domestic wells provide drinking water supply for approximately 40 million people in the United States. Knowing the location of these wells, and the populations they serve, is important for identifying heavily used aquifers, locations susceptible to contamination, and populations potentially impacted by poor-quality groundwater. The 1990 census was the last nationally consistent survey of a home's source of water, and has not been surveyed since. This paper presents a method for projecting the population dependent on domestic wells for years after 1990, using information from the 1990 census along with population data from subsequent censuses. The method is based on the "domestic ratio" at the census block-group level, defined here as the number of households dependent on domestic wells divided by the total population. Analysis of 1990 data (>220,000 block-groups) indicates that the domestic ratio is a function of the household density. As household density increases, the domestic ratio decreases, once a household density threshold is met. The 1990 data were used to develop a relationship between household density and the domestic ratio. The fitted model, along with household density data from 2000 and 2010, was used to estimate domestic ratios for each decadal year. In turn, the number of households dependent on domestic wells was estimated at the block-group level for 2000 and 2010. High-resolution census-block population data were used to refine the spatial distribution of domestic-well usage and to convert the data into population numbers. The results are presented in two downloadable raster datasets for each decadal year. It is estimated that the total population using domestic-well water in the contiguous U.S. increased 1.5% from 1990 to 2000 to a total of 37.25 million people and increased slightly from 2000 to 2010 to 37.29 million people.

Poluição da Água/estatística & dados numéricos , Abastecimento de Água/estatística & dados numéricos , Poços de Água , Monitoramento Ambiental , Características da Família , Água Subterrânea , Humanos , Estados Unidos , Poluentes Químicos da Água