Environmental Protection Agency Maximum Contaminant Research Articles

Survey of 226Ra/228Ra and inorganic constituents in Iowa private drinking water wells

AbstractRadium is a naturally‐occurring radioactive element found in Upper Midwest aquifers, yet exposure risks for unregulated water sources in this region are unknown. A survey of 226/228Ra and other inorganic constituents in 94 private wells was conducted in 2019 across 10 Iowa counties. Within private wells, 53% measured below minimum detectable activity whereas 6.3% have 226/228Ra levels above the United States Environmental Protection Agency Maximum Contaminant Level. 226/228Ra occurrence was not associated with well‐depth or chemical surrogates, but were generally consistent with the lithology and historical water quality trends for aquifers. In 2020, 11 of the 226/228Ra‐impacted wells were re‐sampled to assess the efficacy of in‐home water treatment. Water softeners reduced 226/228Ra to non‐detectable activities, but other inorganic constituents persisted and their removal required more advanced treatment. This study suggests that 226/228Ra occurrence in private wells can reasonably be anticipated from public water supply data if reliable information is available to identify the source aquifer.

Co-exposure of sodium arsenite and uranyl acetate differentially alters gene expression in CD3/CD28 activated CD4+ T-cells.

Communities in the western region of the United States experience environmental exposure to metal mixtures from living in proximity to numerous unremediated abandoned uranium mines. Metals including arsenic and uranium co-occur in and around these sites at levels higher than the United States Environmental Protection Agency maximum contaminant levels. To address the potential effect of these metals on the activation of CD4+ T-cells, we used RNA sequencing methods to determine the effect of exposure to sodium arsenite (1 μM and 10 μM), uranyl acetate (3 μM and 30 μM) or a mixture of sodium arsenite and uranyl acetate (1 μM sodium arsenite + 3 μM uranyl acetate). Sodium arsenite induced a dose dependent effect on activation associated gene expression; targeting immune response genes at the lower dose. Increases in oxidative stress gene expression were observed with both sodium arsenite doses. While uranyl acetate alone did not significantly alter activation associated gene expression, the mixture of uranyl acetate with sodium arsenite demonstrated a combined effect relative to sodium arsenite alone. The results demonstrate the need to investigate metal and metalloid mixtures at environmentally relevant concentrations to better understand the toxicological impact of these mixtures on T-cell activation, function and immune dysregulation.

The MANAGE Drain Concentration database: A new tool compiling North American drainage nutrient concentrations

Artificially drained agricultural systems can be a primary contributor of non-point source nitrogen (N) and phosphorus (P) pollution to ground and surface waters; therefore, it is imperative to understand the mechanisms responsible for nutrient transport from this land use. Here, 79 drainage nutrient-related studies were used to compile 1564 site-years of agricultural drainage N and P concentrations (annual mean flow-weighted and annual arithmetic average) into a major database to aid in assessment of factors leading to nutrient loss through drainage systems. This new Drain Concentration table in the MANAGE (Measured Annual loads from AGricultural Environments) database is a publicly available resource (https://www.ars.usda.gov/plains-area/temple-tx/grassland-soil-and-water-research-laboratory/docs/manage-nutrient-loss-database). Probability of exceedance values were calculated using a Weibull distribution, and across the database, there was a 69% probability a drainage site-year would exceed an annual nitrate-N (NO3-N) concentration of 10 mg/L, the US Environmental Protection Agency Maximum Contaminant Level for drinking water, but only a 27% probability a reported site-year would exceed 0.0375 mg/L dissolved reactive phosphorus, which is a critical total P concentration to avoid freshwater eutrophication. While a surprising number of reported annual means were arithmetic averages rather than flow-weighted averages (27 vs. 71%), reporting of arithmetic means in peer-reviewed literature has decreased over time. We encourage further contributions to and analysis with the MANAGE database, so it can remain a resource for new efforts to better understand and mitigate nutrient losses from agricultural systems.

Analysis of Total Arsenic Content in California Wines and Comparison to Various Health Risk Criteria

Concerns have recently been raised regarding the presence of arsenic in California wine. Total arsenic concentrations in 101 wines produced or bottled in California were characterized using inductively coupled plasma mass spectrometry. Of these wines, 28 were wines identified in media reports as containing arsenic concentrations greater than the U.S. Environmental Protection Agency Maximum Contaminant Level for drinking water of 10 μg/L. The remaining 73 wines were randomly purchased at local retailers. Blush wines were found to contain the greatest total arsenic concentration (mean = 27.2 μg/L; SD = 16.9 μg/L) regardless of sampling group, followed by white wines (mean = 10.9 μg/L; SD = 11.0 μg/L) and red wines (mean = 6.75 μg/L; SD = 7.33 μg/L). Moreover, the publicized group of wines was found to have significantly (<i>p</i> &lt; 0.05) greater total arsenic concentrations (mean = 25.6 μg/L; SD = 12.0 μg/L) than the random wines (mean = 7.42 μg/L; SD = 10.2 μg/L). The concentrations of total arsenic in all wines evaluated in this analysis were less than the two currently used arsenic guidelines for wine of 100 μg/L and 200 μg/L. Results from the statistical analysis suggest that no more than 0.3% of California wines (if any) may contain arsenic concentrations greater than the 100 μg/L guideline. A significant inverse association between total arsenic concentration and unit wine price was also identified in this analysis. Chronic daily intake of arsenic as a result of wine consumption was estimated to account for a small fraction (&lt;8.3%) of a typical adult’s dietary arsenic intake, indicating that wine consumption is not a significant source of total arsenic exposure. These results indicate that the presence of arsenic in wine does not represent a health risk for consumers.

Arsenic Removal from Natural Groundwater Using Cupric Oxide

Groundwater is a main source of drinking water for some rural areas. People in these rural areas are potentially at risk from elevated levels of arsenic (As) due to a lack of water treatment facilities. The objectives of this study were to (1) measure As concentrations in approximately 50 groundwater samples from rural domestic wells in the western United States, (2) explore the potential of cupric oxide (CuO) particles in removal of As from groundwater samples under natural conditions (i.e., without adding competing anions and adjusting the pH or oxidation state), and (3) determine the effects of As removal on the chemistry of groundwater samples. Forty-six groundwater well samples from rural domestic areas were tested in this study. More than 50% of these samples exceeded the U.S. Environmental Protection Agency Maximum Contaminant Limit (US EPA MCL) of 10 µg/L for As. CuO particles effectively removed As from groundwater samples across a wide range of pH (7.11 and 8.95) and concentrations of competing anions including phosphate (<0.05 to 3.06 mg/L), silica (<1 to 54.5 mg/L), and sulfate (1.3 to 735 mg/L). Removal of As showed minor effects on the chemistry of groundwater samples, therefore most of the water quality parameters remained within the US EPA MCLs. Overall, results of this study could help develop a simple one-step process to remove As from groundwater.

Occurrence and geochemistry of radium in water from principal drinking-water aquifer systems of the United States

► 226 Ra plus 228 Ra exceed 0.185 Bq/L in seven eastern and central USA principal aquifers. ► Radium concentration was highest in low pH and anoxic waters. ► Geochemical environments and low aquifer sorption capacity controlled Ra occurrence. ► Alpha recoil affected the presence of 224 Ra in western USA principal aquifers. ► Differences in Ra isotope ratios depended upon geology of the principal aquifer. A total of 1270 raw-water samples (before treatment) were collected from 15 principal and other major aquifer systems (PAs) used for drinking water in 45 states in all major physiographic provinces of the USA and analyzed for concentrations of the Ra isotopes 224 Ra, 226 Ra and 228 Ra establishing the framework for evaluating Ra occurrence. The US Environmental Protection Agency Maximum Contaminant Level (MCL) of 0.185 Bq/L (5 pCi/L) for combined Ra ( 226 Ra plus 228 Ra) for drinking water was exceeded in 4.02% (39 of 971) of samples for which both 226 Ra and 228 Ra were determined, or in 3.15% (40 of 1266) of the samples in which at least one isotope concentration ( 226 Ra or 228 Ra) was determined. The maximum concentration of combined Ra was 0.755 Bq/L (20.4 pCi/L) in water from the North Atlantic Coastal Plain quartzose sand aquifer system. All the exceedences of the MCL for combined Ra occurred in water samples from the following 7 PAs (in order of decreasing relative frequency of occurrence): the Midcontinent and Ozark Plateau Cambro-Ordovician dolomites and sandstones, the North Atlantic Coastal Plain, the Floridan, the crystalline rocks (granitic, metamorphic) of New England, the Mesozoic basins of the Appalachian Piedmont, the Gulf Coastal Plain, and the glacial sands and gravels (highest concentrations in New England). The concentration of Ra was consistently controlled by geochemical properties of the aquifer systems, with the highest concentrations most likely to be present where, as a consequence of the geochemical environment, adsorption of the Ra was slightly decreased. The result is a slight relative increase in Ra mobility, especially notable in aquifers with poor sorptive capacity (Fe-oxide-poor quartzose sands and carbonates), even if Ra is not abundant in the aquifer solids. The most common occurrence of elevated Ra throughout the USA occurred in anoxic water (low dissolved-O 2 ) with high concentrations of Fe or Mn, and in places, high concentrations of the competing ions Ca, Mg, Ba and Sr, and occasionally of dissolved solids, K, SO 4 and HCO 3 . The other water type to frequently contain elevated concentrations of the Ra radioisotopes was acidic (low pH), and had in places, high concentrations of NO 3 and other acid anions, and on occasion, of the competing divalent cations, Mn and Al. One or the other of these broad water types was commonly present in each of the PAs in which elevated concentrations of combined Ra occurred. Concentrations of 226 Ra or 228 Ra or combined Ra correlated significantly with those of the above listed water-quality constituents (on the basis of the non-parametric Spearman correlation technique) and loaded on principal components describing the above water types from the entire data set and for samples from the PAs with the highest combined Ra concentrations. Concentrations of 224 Ra and 226 Ra were significantly correlated to those of 228 Ra (Spearman’s rank correlation coefficient, +0.236 and +0.326, respectively). Activity ratios of 224 Ra/ 228 Ra in the water samples were mostly near 1 when concentrations of both isotopes were greater than or equal to 0.037 Bq/L (1 pCi/L), the level above which analytical results were most reliable. Co-occurrence among these highest concentrations of the Ra radionuclides was most likely in those PAs where chemical conditions are most conducive to Ra mobility (e.g. acidic North Atlantic Coastal Plain). The concentrations of 224 Ra were occasionally greater than 0.037 Bq/L and the ratios of 224 Ra/ 228 Ra were generally highest in the PAs composed of alluvial sands and Cretaceous/Tertiary sandstones from the western USA, likely because concentrations of 224 Ra are enhanced in solution relative to those of 228 Ra by alpha recoil from the aquifer matrix. Rapid adsorption of the two Ra isotopes (controlled by the alkaline and oxic aquifer geochemistry) combined with preferential faster recoil of 224 Ra generates a 224 Ra/ 228 Ra ratio much greater than 1. The 228 Ra/ 226 Ra activity ratio was locally variable, and was generally lower than 1 ( 226 Ra rich) in samples from PAs with carbonate bedrock, but was typically greater than 1 ( 228 Ra rich) in PAs composed of unconsolidated sand.

Occurrence and Potential Human-Health Relevance of Volatile Organic Compounds in Drinking Water from Domestic Wells in the United States

BackgroundAs the population and demand for safe drinking water from domestic wells increase, it is important to examine water quality and contaminant occurrence. A national assessment in 2006 by the U.S. Geological Survey reported findings for 55 volatile organic compounds (VOCs) based on 2,401 domestic wells sampled during 1985–2002.ObjectivesWe examined the occurrence of individual and multiple VOCs and assessed the potential human-health relevance of VOC concentrations. We also identified hydrogeologic and anthropogenic variables that influence the probability of VOC occurrence.MethodsThe domestic well samples were collected at the wellhead before treatment of water and analyzed for 55 VOCs. Results were used to examine VOC occurrence and identify associations of multiple explanatory variables using logistic regression analyses. We used a screening-level assessment to compare VOC concentrations to U.S. Environmental Protection Agency maximum contaminant levels (MCLs) and health-based screening levels.ResultsWe detected VOCs in 65% of the samples; about one-half of these samples contained VOC mixtures. Frequently detected VOCs included chloroform, toluene, 1,2,4-trimethylbenzene, and perchloroethene. VOC concentrations generally were < 1 μg/L. One or more VOC concentrations were greater than MCLs in 1.2% of samples, including dibromochloropropane, 1,2-dichloropropane, and ethylene dibromide (fumigants); perchloroethene and trichloroethene (solvents); and 1,1-dichloroethene (organic synthesis compound).ConclusionsDrinking water supplied by domestic wells is vulnerable to low-level VOC contamination. About 1% of samples had concentrations of potential human-health concern. Identifying factors associated with VOC occurrence may aid in understanding the sources, transport, and fate of VOCs in groundwater.

Effects of Acid Rain on Water Supplies in the Northeast

Results of the first study concerning the impact of acid precipitation on drinking water are reported in terms of health effects in humans as measured by US Environmental Protection Agency maximum contaminant levels. The study focused on sampling surface water and groundwater supplies in the New England states but also included other sites in the Northeast and the Appalachians. No adverse effects on human health were demonstrated, although the highly corrosive nature of New England waters may be at least partly attributable to acidic deposition in poorly buffered watersheds and aquifers.