In the United States and globally, contaminant exposure in unregulated private-well point-of-use tapwater (TW) is a recognized public-health data gap and an obstacle to both risk-management and homeowner decision making. To help address the lack of data on broad contaminant exposures in private-well TW from hydrologically-vulnerable (al-luvial, karst) aquifers in agriculturally-intensive landscapes, samples were collected in 2018-2019 from 47 northeast Iowa farms and analyzed for 35 inorganics, 437 unique organics, 5 in vitro bioassays, and 11 microbial assays. Twenty- six inorganics and 51 organics, dominated by pesticides and related transformation products (35 herbicide-, 5 insecticide-, and 2 fungicide-related), were observed in TW. Heterotrophic bacteria detections were near ubiquitous (94 % of the samples), with detection of total coliform bacteria in 28 % of the samples and growth on at least one putative-pathogen selective media across all TW samples. Health-based hazard index screening levels were exceeded frequently in private-well TW and attributed primarily to inorganics (nitrate, uranium). Results support incorporation of residential treatment systems to protect against contaminant exposure and the need for increased monitoring of rural private-well homes. Continued assessment of unmonitored and unregulated private-supply TW is needed to model contaminant exposures and human-health risks.

Watersheds of the Great Lakes Basin (USA/Canada) are highly modified and impacted by human activities including pesticide use. Despite labeling restrictions intended to minimize risks to nontarget organisms, concerns remain that environmental exposures to pesticides may be occurring at levels negatively impacting nontarget organisms. We used a combination of organismal-level toxicity estimates (in vivo aquatic life benchmarks) and data from high-throughput screening (HTS) assays (in vitro benchmarks) to prioritize pesticides and sites of concern in streams at 16 tributaries to the Great Lakes Basin. In vivo or in vitro benchmark values were exceeded at 15 sites, 10 of which had exceedances throughout the year. Pesticides had the greatest potential biological impact at the site with the greatest proportion of agricultural land use in its basin (the Maumee River, Toledo, OH, USA), with 72 parent compounds or transformation products being detected, 47 of which exceeded at least one benchmark value. Our risk-based screening approach identified multiple pesticide parent compounds of concern in tributaries of the Great Lakes; these compounds included: eight herbicides (metolachlor, acetochlor, 2,4-dichlorophenoxyacetic acid, diuron, atrazine, alachlor, triclopyr, and simazine), three fungicides (chlorothalonil, propiconazole, and carbendazim), and four insecticides (diazinon, fipronil, imidacloprid, and clothianidin). We present methods for reducing the volume and complexity of potential biological effects data that result from combining contaminant surveillance with HTS (in vitro) and traditional (in vivo) toxicity estimates. Environ Toxicol Chem 2023;42:367-384. Published 2022. This article is a U.S. Government work and is in the public domain in the USA. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

River waters contain complex chemical mixtures derived from natural and anthropogenic sources. Aquatic organisms are exposed to the entire chemical composition of the water, resulting in potential effects at the organismal through ecosystem level. This study applied a holistic approach to assess landscape, hydrological, chemical, and biological variables. On-site mobile laboratory experiments were conducted to evaluate biological effects of exposure to chemical mixtures in the Shenandoah River Watershed. A suite of 534 inorganic and organic constituents were analyzed, of which 273 were detected. A watershed-scale accumulated wastewater model was developed to predict environmental concentrations of chemicals derived from wastewater treatment plants (WWTPs) to assess potential aquatic organism exposure for all stream reaches in the watershed. Measured and modeled concentrations generally were within a factor of 2. Ecotoxicological effects from exposure to individual components of the chemical mixture were evaluated using risk quotients (RQs) based on measured or predicted environmental concentrations and no effect concentrations or chronic toxicity threshold values. Seventy-two percent of the compounds had RQ values <0.1, indicating limited risk from individual chemicals. However, when individual RQs were aggregated into a risk index, most stream reaches receiving WWTP effluent posed potential risk to aquatic organisms from exposure to complex chemical mixtures.

If not managed properly, modern agricultural practices can alter surface and groundwater quality and drinking water resources resulting in potential negative effects on aquatic and terrestrial ecosystems. Exposure to agriculturally derived contaminant mixtures has the potential to alter habitat quality and negatively affect fish and other aquatic organisms. Implementation of conservation practices focused on improving water quality continues to increase particularly in agricultural landscapes throughout the United States. The goal of this study was to determine the consequences of land management actions on the primary drivers of contaminant mixtures in five agricultural watersheds in the Chesapeake Bay, the largest watershed of the Atlantic Seaboard in North America where fish health issues have been documented for two decades. Surface water was collected and analyzed for 301 organic contaminants to determine the benefits of implemented best management practices (BMPs) designed to reduce nutrients and sediment to streams in also reducing contaminants in surface waters. Of the contaminants measured, herbicides (atrazine, metolachlor), phytoestrogens (formononetin, genistein, equol), cholesterol and total estrogenicity (indicator of estrogenic response) were detected frequently enough to statistically compare to seasonal flow effects, landscape variables and BMP intensity. Contaminant concentrations were often positively correlated with seasonal stream flow, although the magnitude of this effect varied by contaminant across seasons and sites. Land-use and other less utilized landscape variables including biosolids, manure and pesticide application and percent phytoestrogen producing crops were inversely related with site-average contaminant concentrations. Increased BMP intensity was negatively related to contaminant concentrations indicating potential co-benefits of BMPs for contaminant reduction in the studied watersheds. The information gained from this study will help prioritize ecologically relevant contaminant mixtures for monitoring and contributes to understanding the benefits of BMPs on improving surface water quality to better manage living resources in agricultural landscapes inside and outside the Chesapeake Bay watershed.

Safe drinking water at the point of use (tapwater, TW) is a public-health priority. TW exposures and potential human-health concerns of 540 organics and 35 inorganics were assessed in 45 Chicago-area United States (US) homes in 2017. No US Environmental Protection Agency (EPA) enforceable Maximum Contaminant Level(s) (MCL) were exceeded in any residential or water treatment plant (WTP) pre-distribution TW sample. Ninety percent (90%) of organic analytes were not detected in treated TW, emphasizing the high quality of the Lake Michigan drinking-water source and the efficacy of the drinking-water treatment and monitoring. Sixteen (16) organics were detected in >25% of TW samples, with about 50 detected at least once. Low-level TW exposures to unregulated disinfection byproducts (DBP) of emerging concern, per/polyfluoroalkyl substances (PFAS), and three pesticides were ubiquitous. Common exceedances of non-enforceable EPA MCL Goal(s) (MCLG) of zero for arsenic [As], lead [Pb], uranium [U], bromodichloromethane, and tribromomethane suggest potential human-health concerns and emphasize the continuing need for improved understanding of cumulative effects of low-concentration mixtures on vulnerable sub-populations. Because DBP dominated TW organics, residential-TW concentrations are potentially predictable with expanded pre-distribution DBP monitoring. However, several TW chemicals, notably Pb and several infrequently detected organic compounds, were not readily explained by pre-distribution samples, illustrating the need for continued broad inorganic/organic TW characterization to support consumer assessment of acceptable risk and point-of-use treatment options.

Glyphosate is the most widely used herbicide in the United States for agricultural and non-agricultural weed control. Many studies demonstrate possible effects of glyphosate and its degradate AMPA on human and ecological health. Although glyphosate is thought to have limited mobility in soil, it is found year-round in many rivers and streams throughout the world in both agricultural and developed environments. It is vitally important to continue to increase the knowledge base of glyphosate use, distribution, transport, and impacts on human health and the environment. Here we show that glyphosate and AMPA are found in nearly all of 70 streams throughout the United States at concentrations far below human health or ecological benchmarks, with less occurrence in the Northeast and that undeveloped land, classified as such by land use near the sampling station, has lower concentrations compared to other types of land. Results also show that sites with large watersheds tend to have more AMPA than glyphosate and the opposite is true for small watersheds. Travel times and opportunity for glyphosate to degrade to AMPA and for reservoirs of AMPA to grow are greater in large watersheds. Factors that promoted quick movement of glyphosate to streams, such as subsurface tile or storm drains, sewers, overland flow from developed landscapes, and arid landscapes were associated with sites that had greater concentrations of glyphosate compared to AMPA. These results contribute contemporary information and generalized interpretations adding to the knowledge base of the fate of glyphosate on a national scale and provide a springboard for further exploration of technical processes controlling transport to streams.

First posted November 1, 2018 For additional information, contact: Director, South Atlantic Water Science CenterU.S. Geological Survey720 Gracern RoadColumbia, SC 29210 In 2016, the U.S. Geological Survey (USGS) Environmental Health Mission Area, initiated the Tapwater Exposure Study as part of an infrastructure project to assess human exposure to potential threats from complex mixtures of contaminants. In the pilot phase (2016), samples were collected from 11 States throughout the United States, and in the second phase (2017), the study focused on the Greater Chicago area, including North and South Chicago, Illinois, and East Chicago, Indiana. Residential tapwater samples were collected at private residences during both phases, and during the first phase, samples were collected from Federal office buildings and from one office 19-liter water-bottle source. During the second phase, raw intake and treated (pre-distributional) water samples also were collected from four drinking-water treatment facilities in the Greater Chicago area. Samples were sent to laboratories at the USGS, U.S. Environmental Protection Agency, National Institute of Environmental Health Sciences, and Colorado School of Mines Center for Environmental Risk Assessment, for potential drinking-water pathogens, chemical, and bioassay analyses. These analyses included more than 400 chemicals such as trace elements, steroid hormones, pharmaceuticals, volatile organic compounds, pesticides, per- and polyfluorinated alkyl substances, cyanotoxins, and other organic compounds. The in vitro bioassay analyses included estrogen, androgen, and glucocorticoid receptor activity.

Safe drinking water at the point-of-use (tapwater, TW) is a United States public health priority. Multiple lines of evidence were used to evaluate potential human health concerns of 482 organics and 19 inorganics in TW from 13 (7 public supply, 6 private well self-supply) home and 12 (public supply) workplace locations in 11 states. Only uranium (61.9 μg L-1, private well) exceeded a National Primary Drinking Water Regulation maximum contaminant level (MCL: 30 μg L-1). Lead was detected in 23 samples (MCL goal: zero). Seventy-five organics were detected at least once, with median detections of 5 and 17 compounds in self-supply and public supply samples, respectively (corresponding maxima: 12 and 29). Disinfection byproducts predominated in public supply samples, comprising 21% of all detected and 6 of the 10 most frequently detected. Chemicals designed to be bioactive (26 pesticides, 10 pharmaceuticals) comprised 48% of detected organics. Site-specific cumulative exposure-activity ratios (∑EAR) were calculated for the 36 detected organics with ToxCast data. Because these detections are fractional indicators of a largely uncharacterized contaminant space, ∑EAR in excess of 0.001 and 0.01 in 74 and 26% of public supply samples, respectively, provide an argument for prioritized assessment of cumulative effects to vulnerable populations from trace-level TW exposures.

The environmental fate of polyoxyethylene tallow amine (POEA), an additive in glyphosate herbicide formulations, has not been studied. This study examined the dissipation of POEA; glyphosate; and aminomethylphosphonic acid (AMPA), a degradation product of glyphosate, in the top 45 cm of soil from an agricultural field where glyphosate was applied. The concentration of these compounds was also analyzed in bed sediment samples from watersheds in agricultural and urban areas from six states (Georgia, Hawaii, Iowa, Mississippi, North Carolina, South Carolina). The field studies show that POEA, glyphosate, and AMPA persist on the soil from planting season to planting season but dissipate over time with little migration into deeper soil. POEA, glyphosate, and AMPA were found on the bed sediment samples in urban and agricultural watersheds.

Recent environmental surveys report widespread detections of the herbicide glyphosate [N-(phosphonomethyl)glycine] in surface waters, despite its strong immobilization and rapid biodegradation in soils. We performed four high-frequency sampling campaigns (from 2015 to 2017) following controlled spray applications on an experimental perennial grass field site with wetness-prone marginal soils. We monitored dissolved glyphosate concentrations in the outflow (runoff and shallow drainage) using liquid chromatography mass spectrometry and enzyme-linked immunosorbent assays. Rainfall-triggered outflow events occurred between 3 and 13 days following spray application. Outflow concentrations varied widely from nondetectable levels to 90 mu g L-1, peaking during the first significant outflow event in each campaign and diminishing as flows subsided. Subsequent outflow peaks caused concentrations to increase again but to a lesser extent. Cumulative mass efflux in outflow across the different campaigns ranged from 0.06 to 1.0% of applied glyphosate. Cumulative glyphosate losses in the outflow were not during the postspray sampling period, but rather with soil hydrologic conditions at the time of spraying as reflected by the 7 day cumulative prespray rainfall, with wetter antecedent conditions favoring greater cumulative mobilization. Avoiding spraying under such conditions may mitigate potential glyphosate mobilization.

Surface water from 38 streams nationwide was assessed using 14 target-organic methods (719 compounds). Designed-bioactive anthropogenic contaminants (biocides, pharmaceuticals) comprised 57% of 406 organics detected at least once. The 10 most-frequently detected anthropogenic-organics included eight pesticides (desulfinylfipronil, AMPA, chlorpyrifos, dieldrin, metolachlor, atrazine, CIAT, glyphosate) and two pharmaceuticals (caffeine, metformin) with detection frequencies ranging 66-84% of all sites. Detected contaminant concentrations varied from less than 1 ng L-1 to greater than 10 μg L-1, with 77 and 278 having median detected concentrations greater than 100 ng L-1 and 10 ng L-1, respectively. Cumulative detections and concentrations ranged 4-161 compounds (median 70) and 8.5-102 847 ng L-1, respectively, and correlated significantly with wastewater discharge, watershed development, and toxic release inventory metrics. Log10 concentrations of widely monitored HHCB, triclosan, and carbamazepine explained 71-82% of the variability in the total number of compounds detected (linear regression; p-values: < 0.001-0.012), providing a statistical inference tool for unmonitored contaminants. Due to multiple modes of action, high bioactivity, biorecalcitrance, and direct environment application (pesticides), designed-bioactive organics (median 41 per site at μg L-1 cumulative concentrations) in developed watersheds present aquatic health concerns, given their acknowledged potential for sublethal effects to sensitive species and lifecycle stages at low ng L-1.

First posted March 22, 2017 For additional information, contact: Director, South Atlantic Water Science Center U.S. Geological Survey 720 Gracern Road Stephenson Center, Suite 129 Columbia, SC 29210 https:www.usgs.gov/water/southatlantic/ A vast array of chemical compounds are in wide commercial use in the United States, and the potential ecological and human-health effect of exposure to chemical mixtures has been identified as a high priority in environment health science. Awareness of the potential effects of low-level chemical exposures is rising. The U.S. Geological Survey, in cooperation with the U.S. Environmental Protection Agency, conducted a study in which samples were collected from 38 streams in 25 States to provide an overview of contaminants found in stream water across the Nation. Additionally, biological screening assays were used to help determine any potential ecological and human-health effects of these chemical mixtures and to prioritize target chemicals for future toxicological studies. This report describes the site locations and the sampling and analytical methods and quality-assurance procedures used in the study.

Glyphosate and atrazine are the most intensively used herbicides in the United States. Although there is abundant spatial and temporal information on atrazine occurrence at regional scales, there are far fewer data for glyphosate, and studies that compare the two herbicides are rare. We investigated temporal patterns in glyphosate and atrazine concentrations measured weekly during the 2013 growing season in 100 small streams in the Midwestern United States. Glyphosate was detected in 44% of samples (method reporting level 0.2μg/L); atrazine was detected above a threshold of 0.2μg/L in 54% of samples. Glyphosate was detected more frequently in 12 urban streams than in 88 agricultural streams, and at concentrations similar to those in streams with high agricultural land use (>40% row crop) in the watershed. In contrast, atrazine was detected more frequently and at higher concentrations in agricultural streams than in urban streams. The maximum concentration of glyphosate measured at most urban sites exceeded the maximum atrazine concentration, whereas at agricultural sites the reverse was true. Measurement at a 2-day interval at 8 sites in northern Missouri revealed that transport of both herbicide compounds appeared to be controlled by spring flush, that peak concentration duration was brief, but that peaks in atrazine concentrations were of longer duration than those of glyphosate. The 2-day sampling also indicated that weekly sampling is unlikely to capture peak concentrations of glyphosate and atrazine.

Polyoxyethylene tallow amine (POEA) is an inert ingredient added to formulations of glyphosate, the most widely applied agricultural herbicide. POEA has been shown to have toxic effects to some aquatic organisms making the potential transport of POEA from the application site into the environment an important concern. This study characterized the adsorption of POEA to soils and assessed its occurrence and homologue distribution in agricultural soils from six states. Adsorption experiments of POEA to selected soils showed that POEA adsorbed much stronger than glyphosate; calcium chloride increased the binding of POEA; and the binding of POEA was stronger in low pH conditions. POEA was detected on a soil sample from an agricultural field near Lawrence, Kansas, but with a loss of homologues that contain alkenes. POEA was also detected on soil samples collected between February and early March from corn and soybean fields from ten different sites in five other states (Iowa, Illinois, Indiana, Missouri, Mississippi). This is the first study to characterize the adsorption of POEA to soil, the potential widespread occurrence of POEA on agricultural soils, and the persistence of the POEA homologues on agricultural soils into the following growing season.

Endogenous progestogens and pharmaceutical progestins enter the environment through wastewater treatment plant effluent and agricultural field runoff. Lab studies demonstrate strong, negative exposure effects of these chemicals on aquatic vertebrate reproduction. Behavior can be a sensitive, early indicator of exposure to environmental contaminants associated with altered reproduction yet is rarely examined in ecotoxicology studies. Gestodene is a human contraceptive progestin and a potent activator of fish androgen receptors. Our objective was to test the effects of gestodene on reproductive behavior and associated egg deposition in the fathead minnow. After only 1 day, males exposed to ng/L of gestodene were more aggressive and less interested in courtship and mating, and exposed females displayed less female courtship behavior. Interestingly, 25% of the gestodene tanks contained a female that drove the male out of the breeding tile and displayed male-typical courtship behaviors toward the other female. Gestodene decreased or arrested egg deposition with no observed gonadal histopathology. Together, these results suggest that effects on egg deposition are primarily due to altered reproductive behavior. The mechanisms by which gestodene disrupts behavior are unknown. Nonetheless, the rapid and profound alterations of the reproductive biology of gestodene-exposed fish suggest that wild populations could be similarly affected.

Phytoplankton communities in freshwater lakes, ponds, and reservoirs may be dominated by cyanobacteria (also called blue-green algae) under certain environmental conditions. Cyanobacteria may cause a range of water-quality impairments, including the potential for toxin production. Cyanobacteria toxins (cyanotoxins) may adversely impact human and ecological health. Microcystins are considered to be one of the most commonly found classes of cyanotoxins in freshwater ecosystems, and as such were selected as a recreational indicator of water quality for the 2007 United States Environmental Protection Agency (EPA) National Lakes Assessment. However, much less is known about the occurrence of other classes of cyanotoxins in fresh surface water such as anatoxins, cylindrospermopsins, nodularins, and saxitoxins. The 2007 National Lakes Assessment followed a probabilistic study design and was directed by the EPA, in partnership with States, Tribes, and other federal agencies of the United States, to provide an assessment of water quality in the Nation’s lakes, ponds, and reservoirs based on trophic status, and ecological and recreational indicators. Integrated photic zone samples were collected by the EPA, U.S. Geological Survey (USGS), States, and Tribes in target water bodies, generally at their deepest point, and analyzed for microcystins by the U.S. Geological Survey. The USGS assisted with this survey by providing technical expertise and enzyme linked immunosorbent assay (ELISA) analysis of microcystins for all survey samples as an indicator for recreational water quality. A small subset of samples (n=27) was analyzed by liquid chromatography tandem mass spectrometry (LC/MS/MS) by the USGS. Additionally, through partnership with the EPA National Health and Environmental Effects Research Laboratory (NHEERL), USGS analyzed all frozen samples by ELISA for two other classes of cyanotoxins, cylindrospermopsins and saxitoxins. Total cylindrospermopsins, microcystins, and saxitoxins were measured by enzyme-linked immunosorbent assay in a total of 1,331 samples from 1,161 lakes. Samples from this study had detection frequencies of 4.0, 32 (unweighted), and 7.7 percent, mean concentrations (detections only) of 0.56, 3.0, and 0.061 micrograms/L (μg/L), and maximum concentrations of 4.4, 230, and 0.38 μg/L for cylindrospermopsins, microcystins, and saxitoxins by ELISA, respectively in visit 1 and visit 2 samples. Microcystin ELISA results were categorized based on World Health Organization recreational surface-water guidelines for the relative probability of adverse health impacts because of microcystin exposure. The dataset described in this report is the first ever national reconnaissance of cyanotoxins in the United States. At least one microcystin congener was detected by LC/MS/MS in 52 percent of the 27 samples analyzed at a concentration greater than the LC/MS/MS minimum reporting level (MRL) of 0.010 μg/L and included detections for microcystin-LA, microcystin-LR, microcystin-LY, microcystin-RR, and microcystin-YR. Anatoxin-a, cylindrospermopsin, and nodularin-R were detected in 15 percent, 7 percent, and 4 percent of samples, respectively, at concentrations above 0.010 μg/L. Deoxycylindrospermopsin, domoic acid, lyngbyatoxin-a, microcystin-LF, microcystin-LW, and okadaic acid were not detected in the LC/MS/MS subset.

A large nation-wide survey of cyanotoxins (1161 lakes) in the United States (U.S.) was conducted during the EPA National Lakes Assessment 2007. Cyanotoxin data were compared with cyanobacteria abundance- and chlorophyll-based World Health Organization (WHO) thresholds and mouse toxicity data to evaluate potential recreational risks. Cylindrospermopsins, microcystins, and saxitoxins were detected (ELISA) in 4.0, 32, and 7.7% of samples with mean concentrations of 0.56, 3.0, and 0.061 μg/L, respectively (detections only). Co-occurrence of the three cyanotoxin classes was rare (0.32%) when at least one toxin was detected. Cyanobacteria were present and dominant in 98 and 76% of samples, respectively. Potential anatoxin-, cylindrospermopsin-, microcystin-, and saxitoxin-producing cyanobacteria occurred in 81, 67, 95, and 79% of samples, respectively. Anatoxin-a and nodularin-R were detected (LC/MS/MS) in 15 and 3.7% samples (n = 27). The WHO moderate and high risk thresholds for microcystins, cyanobacteria abundance, and total chlorophyll were exceeded in 1.1, 27, and 44% of samples, respectively. Complete agreement by all three WHO microcystin metrics occurred in 27% of samples. This suggests that WHO microcystin metrics based on total chlorophyll and cyanobacterial abundance can overestimate microcystin risk when compared to WHO microcystin thresholds. The lack of parity among the WHO thresholds was expected since chlorophyll is common amongst all phytoplankton and not all cyanobacteria produce microcystins.