Threatened Waters What the Science Shows

According to USGS, 90 percent of streams sampled had five or more pesticides in water that exceeded at least one aquatic-life federal standard. Many of these pesticides are also linked to a range of human and environmental health effects including cancer, birth defects, neurological and reproductive health impacts. The research below highlights the impact of pesticides on water quality, human health, and the environment.

Surveys of Water Health

This 2021 study finds pesticide breakdown products are just as ubiquitous as their parent compounds in urban streams throughout the United States, according to research conducted by the U.S. Geological Survey (USGS) and published in Environmental Science and Technology. USGS researchers subdivided the U.S. into five regions (Pacific NW, Coastal California, Midwest, Northeast, and Southeast) and took 76 to 100 water samples in small streams for each region over the course of five years. Samples were tested for 108 pesticide active ingredients, and 116 transformation products (also known as breakdown products or metabolites) that arise as active ingredients degrade after a pesticide application. Of the active ingredients sampled, at least one pesticide was detected in 418 of 442 total stream samples conducted, representing a 95% detection rate. Breakdown products were just as widespread, with 396 out of 442 – 90% of streams sites showing detects. According to the study, 102 breakdown products were detected at least once, and nearly 30 were detected in over 20% of samples. The first of its kind findings place an important spotlight on the long-term impacts of pesticide use on health and the environment.

Pesticide mixtures show potential toxicity to aquatic life in U.S. streams, water years 2013–2017.

This 2020 report by the U.S. Geological Survey (USGS), National Water-Quality Assessment (NAWQA) Project, reveals the presence of pesticides is widespread in U.S. rivers and streams, with over almost 90 percent of water samples containing at least five or more different pesticides. Researchers in the report note, “[The] primary objective of this study was to characterize pesticide mixtures found in stream water samples at 72 sites across the United States in watersheds with agricultural, developed, and mixed land uses during 2013–2017.” Additionally, researchers aim to understand the “potential toxicity to aquatic life from the pesticide mixtures and evaluate the occurrence of drivers of potential mixture toxicity.”

To assess national water quality, researchers collected water samples from watershed sampling sites established in 1992 by the National Water Quality Network (NWQN) – Rivers and Streams, based on land-use type (agricultural, developed/urban, and mixed). From 2013-2017, researchers collected water samples from each watershed site monthly, increasing collection frequency in months with greater pesticide runoff, like rainy seasons. Researchers assessed pesticide levels in water samples and applied a Pesticide Toxicity Index (PTI) to measure the potential toxicity of pesticide mixtures to three taxonomic groups – fish, cladocerans (small freshwater crustaceans), and benthic invertebrates. The results find that during 2013-2017 at least five or more pesticides present in 88% of water samples from NWQN sampling sites. Of the 221 pesticide compounds analyzed, 17 (13 insecticides, two herbicides, one fungicide, and one synergist) are primary drivers of toxicity in aquatic taxonomic groups. According to the PTI analysis, one pesticide compound contributes to >50% of the sample toxicity, while other present pesticides only contribute minimally to toxicity. USGS concludes, “Identification of primary contributors to toxicity could aid efforts to improve the quality of rivers and streams to support aquatic life.”

An Overview Comparing Results from Two Decades of Monitoring for Pesticides in the Nation’s Streams and Rivers, 1992–2001 and 2002–2011

This 2014 report provides an overview of the U.S. Geological Survey National Water-Quality Assessment program and National Stream Quality Accounting Network findings for pesticide occurrence in U.S. streams and rivers during 2002–11 and compares them to findings for the previous decade (1992–2001). In addition, pesticide stream concentrations were compared to Human Health Benchmarks (HHBs) and chronic Aquatic Life Benchmarks (ALBs). The comparisons between the decades were intended to be simple and descriptive. Trends over time are being evaluated separately in a series of studies involving rigorous trend analysis. During both decades, one or more pesticides or pesticide degradates were detected more than 90 percent of the time in streams across all types of land uses. For individual pesticides during 2002–11, atrazine (and degradate, deethylatrazine), carbaryl, fipronil (and degradates), metolachlor, prometon, and simazine were detected in streams more than 50 percent of the time. In contrast, alachlor, chlorpyrifos, cyanazine, diazinon, EPTC, Dacthal, and tebuthiuron were detected less frequently in streams during the second decade than during the first decade. During 2002–11, only one stream had an annual mean pesticide concentration that exceeded an HHB. In contrast, 17 percent of agriculture land-use streams and one mixed land-use stream had annual mean pesticide concentrations that exceeded HHBs during 1992–2001. The difference between the first and second decades in terms of percent of streams exceeding HHBs was attributed to regulatory changes. During 2002–11, nearly two-thirds of agriculture land-use streams and nearly one-half of mixed land-use streams exceeded chronic ALBs. For urban land use, 90 percent of the streams exceeded a chronic ALB. Fipronil, metolachlor, malathion, cis-permethrin, and dichlorvos exceeded chronic ALBs for more than 10 percent of the streams. For agriculture and mixed land-use streams, the overall percent of streams that exceeded a chronic ALB was very similar between the decades. For urban land-use streams, the percent of streams exceeding a chronic ALB during 2002–11 nearly doubled that seen during 1992–2001. The reason for this difference was the inclusion of fipronil monitoring during the second decade. Across all land-use streams, the percent of streams exceeding a chronic ALB for fipronil during 2002–11 was greater than all other insecticides during both decades. The percent of streams exceeding a chronic ALB for metolachlor, chlorpyrifos, diazinon, malathion, and carbaryl decreased from the first decade to the second decade. The results of the 2002–11 summary and comparison to 1992–2001 are consistent with the results from more rigorous trend analysis of pesticide stream concentrations for individual streams in various regions of the U.S.

The Quality of Our Nation’s Waters: Ecological Health in the Nation’s Streams, 1993–2005
This 2013 report published by USGS “presents a national assessment of stream health based on the condition of biological communities in relation to important physical and chemical factors, such as the degree of hydrologic alteration and concentrations of nutrients and other dissolved contaminants. Algae, macroinvertebrates, and fish provide a direct measure of stream health because they live within streams for weeks to years, therefore integrating through time the effects of changes to their chemical and physical environment.” The report concludes that “Efforts to understand the causes of reduced stream health should consider the possible effects of nutrients and pesticides, in addition to modified flows, particularly in agricultural and urban settings.” Indeed, according to the author only one in five streams in agricultural and urban areas were considered healthy. Those streams tended to have more natural flows and less runoff of pollution from roads and farms.

Occurrence of Pesticides in Water and Sediment Collected from Amphibian Habitats Located Throughout the United States, 2009–2010
This 2012 study conducted by the U.S. Geological Service surveyed information between 2009 and 2010 from 11 sites in California and 18 sites elsewhere. Water samples were analyzed for 96 pesticides by using gas chromatography/mass spectrometry. A total of 24 pesticides were detected in one or more of the 54 water samples, including 7 fungicides, 10 herbicides, 4 insecticides, 1 synergist, and 2 pesticide degradates. Bed-sediment samples were analyzed for 94 pesticides by using accelerated solvent extraction, gel permeation chromatography for sulfur removal, and carbon/alumina stacked solid-phase extraction cartridges to remove interfering sediment matrices. In bed sediment, 22 pesticides were detected in one or more of the samples, including 9 fungicides, 3 pyrethroid insecticides, p,p’-dichlorodiphenyltrichloroethane (p,p’-DDT) and its major degradates, as well as several herbicides.The report "Occurrence of Pesticides in Water and Sediment Collected from Amphibian Habitats Located Throughout the United States, 2009–2010" was published by the US Geological Service.

Addressing Nitrate in California’s Drinking Water
This 2012 report released by UC Davis examined the the four-county Tulare Lake Basin and the Monterey County portion of the Salinas Valley. The study found that: “Nitrate problems will likely worsen for several decades; agricultural fertilizers and animal wastes applied to cropland are by far the largest regional sources of nitrate in groundwater; nitrate loading reductions are possible, some at modest cost. Large reductions of nitrate loads to groundwater can have substantial economic cost; direct remediation to remove nitrate from large groundwater basins is extremely costly and not technically feasible. Instead, “pump-and-fertilize” and improved groundwater recharge management are less costly long-term alternatives; erinking water supply actions such as blending, treatment, and alternative water supplies are most cost-effective. Blending will become less available in many cases as nitrate pollution continues to spread; many small communities cannot afford safe drinking water treatment and supply action. High fixed costs affect small systems disproportionately. The most promising revenue source is a fee on nitrogen fertilizer use in these basins; A nitrogen fertilizer use fee could compensate affected small communities for mitigation expenses and effects of nitrate pollution; Inconsistency and inaccessibility of data prevent effective and continuous assessment. A statewide effort is needed to integrate diverse water-related data collection activities by many state and local agencies

Regression Models for Estimating Concentrations of Atrazine plus Deethylatrazine in Shallow Groundwater in Agricultural Areas of the United States
This 2012 study published in the Journal of Environmental Quality used models to predict the summed concentration of atrazine and its degradate deethylatrazine  (DEA) in shallow groundwater underlying agricultural settings across the conterminous United States. Results show that only about 5% of agricultural areas have greater than a 10% probability of exceeding the USEPA maximum contaminant level of 3.0 μg L.

Record-setting algal bloom in Lake Erie caused by agricultural and meteorological trends consistent with expected future conditions
The 2012 study published in Proceedings of the National Academy of Sciences concludes that “long-term trends in agricultural practices are consistent with increasing phosphorus loading to the western basin of the lake, and that these trends, coupled with meteorological conditions in spring 2011, produced record-breaking nutrient loads.” In short, Lake Erie’s algal problems are caused by agricultural practices, particularly fertilizer use, which provided nutrients for the blooms to grow. This is compounded by warmer weather, which allows the cyanobacteria, or blue-green algae, to grow and multiply, causing toxic effects. The study "Record-setting algal bloom in Lake Erie caused by agricultural and meteorological trends consistent with expected future conditions" was published in the Proceedings of the National Academy of Sciences. Read Beyond Pesticides' Daily News Entry from April, 2013.

Fate and transport of glyphosate and Aminomethylphosphonic acid in surface waters of agricultural basins
This 2012 article published in Pest Management Science determined “glyphosate and AMPA were frequently detected in the surface waters of four agricultural basins. The frequency and magnitude of detections varied across basins, and the load, as a percentage of use, ranged from 0.009 to 0.86% and could be related to three general characteristics: source strength, rainfall runoff and flow route.”

Widespread Occurrence of Glyphosate and its Degradation Product (AMPA) in U.S. Soils, Surface Water, Groundwater, and Precipitation, 2001-2009
The 2011 study published by USGS summarizes glyphosate concentrations in water and sediment samples collected from 2001 through 2009. Results from 3,606 environmental and 1,008 quality assurance samples collected from 38 States and the District of Columbia indicate that glyphosate is more mobile and occurs more widely in the environment than was previously thought. Glyphosate was detected frequently in soil and sediment (91% of samples), ditches and drains (71%), precipitation (71%), streams (51%), and large rivers (46%); and less frequently in wetlands (38%), soil water (34%), lakes (22%), waste-water treatment plant (WWTP) outfalls (9%), and groundwater (6%). The study "Widespread Occurrence of Glyphosate and its Degradation Product (AMPA) in U.S. Soils, Surface Water, Groundwater, and Precipitation, 2001-2009" was published by the American Geophysical Union.

Occurrence And Fate Of The Herbicide Glyphosate And Its Degradate Aminomethylphosphonic Acid In The Atmosphere
This 2011 article published in Environmental Toxins and Chemicals” is the first report on the ambient levels of glyphosate, the most widely used herbicide in the United States, and its major degradation product, aminomethylphosphonic acid (AMPA), in air and rain…The frequency of glyphosate detection ranged from 60 to 100% in both air and rain. The concentrations of glyphosate ranged from <0.01 to 9.1 ng/m(3) and from <0.1 to 2.5 µg/L in air and rain samples, respectively… It is not known what percentage of the applied glyphosate is introduced into the air, but it was estimated that up to 0.7% of application is removed from the air in rainfall. Glyphosate is efficiently removed from the air; it is estimated that an average of 97% of the glyphosate in the air is removed by a weekly rainfall ≥ 30 mm”

Chromium-6 in U.S. Tap Water
This 2011 report released by the Environmental Working Group  found that “Tap water from 31 of 35 U.S. cities tested contains hexavalent chromium (or chromium-6), the carcinogenic “Erin Brockovich chemical,” according to laboratory tests. The highest levels were detected in Norman, Okla.; Honolulu, Hawaii; and Riverside,California….Levels of the carcinogen in 25 cities tested by  EWG were higher than California’s proposed public  health goal. Tap water from Norman, Okla. (population 90,000) contained more than 200 times California’s proposed safe limit.”

Occurrence of Azoxystrobin, Propiconazole, and Selected Other Fungicides in US Streams, 2005–2006
This 2011 article published in Water, Air, & Soil Pollution found “At least one fungicide was detected in 56% of the 103 samples, as many as five fungicides were detected in an individual sample, and mixtures of fungicides were common. Azoxystrobin was detected most frequently (45% of 103 samples) followed by metalaxyl (27%), propiconazole (17%), myclobutanil (9%), and tebuconazole (6%). Fungicide detections ranged from 0.002 to 1.15μg/L. There was indication of a seasonal pattern to fungicide occurrence, with detections more common and concentrations higher in late summer and early fall than in spring. At a few sites, fungicides were detected in all samples collected suggesting the potential for season-long occurrence in some streams...”

Changing Use and Occurrence of Pesticides in Surface Waters of California's Rice-Growing Region
This 2011 study published by USGS "investigated the changes to water quality in rice paddies in California, with implication for the Sacramento/San Joaquin Delta, a critical habitat for many threatened native species. Filtered water samples were analyzed for 92 pesticides and pesticide degradates by gas chromatography/mass spectrometry. Azoxystrobin and 3,4-DCA (the major breakdown product of propanil) were detected in every sample, and at concentrations up to 136 and 128 μg/L, respectively. Clomazone and thiobencarb were detected in greater than 93% of water samples, with maximum concentrations of 19.4, and 12.4 μg/L. Propanil was present in 60% of samples and at a maximum concentration of 6.5 μg/L.

Quantification of organophosphate insecticides in drinking water in urban areas
This 2011 study published in International Journal of Mass Spectronomy used a sensitive method for the quantification of eight organophosphate pesticides in water samples at the ngL−1 concentration level. For organophosphates in drinking and bore water samples collected from different parts of urban areas researchers found detectable levels of monocrotofos, imedacloprid, triazofos, atrazine, propanil, quinolfos and metribuzin in more than 23% of the water samples analyzed.

Comparison of Field-scale Herbicide Runoff and Volatilization Losses: An Eight-Year Field Investigation.
This 2010 article published in the Journal Environmental Quality examined runoff and volatization of atrazine and metachlor. “Results demonstrated that volatilization losses for these two herbicides were significantly greater than runoff losses ( < 0.007), even though both have relatively low vapor pressures. The largest annual runoff loss for metolachlor never exceeded 2.5%, whereas atrazine runoff never exceeded 3% of that applied. On the other hand, herbicide cumulative volatilization losses after 5 d ranged from about 5 to 63% of that applied for metolachlor and about 2 to 12% of that applied for atrazine. Additionally, daytime herbicide volatilization losses were significantly greater than nighttime vapor losses ( < 0.05). This research confirmed that vapor losses for some commonly used herbicides frequently exceeds runoff losses and herbicide vapor losses on the same site and with the same management practices can vary significantly year to year depending on local environmental conditions.”

Trends in pesticide concentrations in urban streams in the United States, 1992–2008
This 2010 study published by the USGS took samples from urban streams across the US and examined them for presence of “eight herbicides and one degradation product (simazine, prometon, atrazine, deethylatrazine, metolachlor, trifluralin, pendimethalin, tebuthiuron, and Dacthal), and five insecticides and two degradation products (chlorpyrifos, malathion, diazinon, fipronil, fipronil sulfide, desulfinylfipronil, and carbaryl).” Trend analysis results for the herbicides indicated many significant trends, both upward and downward, with varying patterns depending on period, region, and herbicide.

Anthropogenic organic compounds in source water of nine community water systems that withdraw from streams, 2002–05
This 2008 study published by USGS found that “About one-half (134) of the compounds were detected at least once in source-water samples. Forty-seven compounds were detected commonly (in 10 percent or more of the samples), and six compounds (chloroform, atrazine, simazine, metolachlor, deethylatrazine, and hexahydrohexamethylcyclopentabenzopyran (HHCB) were detected in more than one-half of the samples. Chloroform was the most commonly detected compound—in every sample (year round) at five sites. Findings for chloroform and the fragrances HHCB and acetyl hexamethyl tetrahydronaphthalene (AHTN) indicate an association between occurrence and the presence of large upstream wastewater discharges in the watersheds. The herbicides atrazine, simazine, and metolachlor also were among the most commonly detected compounds. Degradates of these herbicides, as well as those of a few other commonly occurring herbicides, generally were detected at concentrations similar to or greater than concentrations of the parent compound. Samples typically contained mixtures of two or more compounds. The total number of compounds and their total concentration in samples generally increased with the amount of urban and agricultural land use in a watershed.”

Quality of water from domestic wells in principal aquifers of the United States, 1991–2004
This 2008 article published by USGS as part of the National Water-Quality Assessment Program “water samples were collected during 1991–2004 from domestic wells (private wells used for household drinking water) for analysis of drinking-water contaminants, where contaminants are considered, as defined by the Safe Drinking Water Act, to be all substances in water…Collectively, about 23 percent of wells had at least 1 contaminant present at concentrations greater than an MCL or HBSL, based on analysis of samples from 1,389 wells in which most contaminants were measured…”

Synthesis of U.S. Geological Survey Science for the Chesapeake Bay Ecosystem and Implications for Environmental Management
This 2007 article published by the USGS, includes a summary of: "land use change, water quality in the watershed including nutrients, sediment, and contaminants; long term changes in estuarine water quality, estuary habitats focusing on submerged aquatic vegetation (SAV) and tidal wetlands and factors affecting fish and water bird populations." ..."Synthetic organic pesticides, along with certain degradation products, have been widely detected in groundwater and streams in the Bay watershed. The most commonly detected pesticides are herbicides used on corn, soybeans, and small grains. Pesticides were also detected in urban areas, including insecticides and the herbicide promotion. Pesticides are present year round but changes in their concentrations reflect application rates and properties affecting their movement. Emerging contaminants such as pharmaceuticals and hormones are also being detected in the Bay Watershed, with the highest number being detected in municipal effluent.

Agricultural pesticides and selected degradation products in five tidal regions and the main stem of Chesapeake Bay, USA.
This 2007 article published in Environmental Toxicology and Chemistry examined agricultural pesticides in five tidal regions: " During the early spring of 2000, surface water samples were collected for pesticide analysis from 18 stations spanning the Chesapeake Bay. In a separate effort from July to September of 2004, 61 stations within several tidal regions were characterized with respect to 21 pesticides and 11 of their degradation products. Three regions were located on the agricultural Delmarva Peninsula: The Chester, Nanticoke, and Pocomoke Rivers. Two regions were located on the more urban western shore: The Rhode and South Rivers and the Lower Mobjack Bay, including the Back and Poquoson Rivers. In both studies, herbicides and their degradation products were the most frequently detected chemicals. In 2000, atrazine and metolachlor were found at all 18 stations. In 2004, the highest parent herbicide concentrations were found in the upstream region of Chester River. The highest concentration for any analyte in these studies was for the ethane sulfonic acid of metolachlor (MESA) at 2,900 ng/L in the Nanticoke River. The degradation product MESA also had the greatest concentration of any analyte in the Pocomoke River (2,100 ng/L) and in the Chester River (1,200 ng/L)."

The Quality of Our Nation’s Waters—Pesticides in the Nation’s Streams and Ground Water, 1992–2001
This 2006 article published by USGS was designed to answer: “What is the quality of our Nation’s streams and ground water? How is the quality changing over time? How do natural features and human activities affect the quality of streams and ground water, and where are those effects most pronounced? By combining information on water chemistry, physical characteristics, stream habitat, and aquatic life, the NAWQA Program aims to provide science-based insights for current and emerging water issues and priorities. NAWQA results can contribute to informed decisions that result in practical and effective water-resource management and strategies that protect and restore water quality.”

Patterns of aquatic toxicity in an agriculturally dominated coastal watershed in California
This 1999 studypublished in Agriculture, Ecosystems, & Environment."was designed to investigate the occurrence, severity, sources and causes of aquatic toxicity in a coastal river and estuary subject to non-point source pollutant inputs from adjacent agricultural and urban areas along the Pajaro River estuarine system. Seven sites in the estuary, upstream river, tributary sloughs, and agricultural drainage ditches were selected to identify tributaries that might contribute toxic runoff to the estuary. Three pesticides (toxaphene, DDT, and diazinon) were found at concentrations higher than published toxicity thresholds for resident aquatic species. Toxicity in the estuary was significantly correlated with increased river flow.

Water and Human Health Research
Triclosan and Its Toxic Breakdown Products Found Polluting Freshwater Lakes
This 2013 study published in Environmental Science and Technology sampled sediments from freshwater lakes across Minnesota, including Lake Superior. Bill Arnold, Ph.D.,co-author of the study and professor at University of Minnesota notes, “We found that in all the lakes there’s triclosan in the sediment, and in general, the concentration increased from when triclosan was invented in 1964 to present day. And we also found there are seven other compounds that are derivatives or degradation products of triclosan that are also in the sediment an also increasing in concentration with time.” Some of the breakdown products that scientists discovered were polychlorodibenzo-p-dioxins (PCDDs), a group of chemicals known to be toxic to both humans and wildlife. Read Beyond Pesticides’ Daily News entry January, 2013.

Occurrence and Potential Sources of Pyrethroid Insecticides in Stream Sediments from Seven U.S. Metropolitan Areas
This 2012 study published in Environmental Science and Technology reviewed data nationwide on pyrethroid insecticides and found “One or more pyrethroids were detected in almost half of the samples, with bifenthrin detected the most frequently (41%) and in each metropolitan area. Cyhalothrin, cypermethrin, permethrin, and resmethrin were detected much less frequently. Pyrethroid concentrations and Hyalella azteca mortality in 28-d tests were lower than in most urban stream studies. Log-transformed total pyrethroid toxic units (TUs) were significantly correlated with survival and bifenthrin was likely responsible for the majority of the observed toxicity... This study shows that pyrethroids commonly occur in urban stream sediments and may be contributing to sediment toxicity across the country.”

Urinary Biomarkers of Prenatal Atrazine Exposure and Adverse Birth Outcomes in the PELAGIE Birth Cohort
This 2011 study published in Environmental Health Perspectives “assessed the association between adverse birth outcomes and urinary biomarkers of prenatal atrazine exposure, while taking into account exposures to other herbicides used on corn crops (simazine, alachlor, metolachlor, and acetochlor)…This study used a case-cohort design nested in a prospective birth cohort conducted in the Brittany region of France from 2002 through 2006. We collected maternal urine samples to examine pesticide exposure biomarkers before the 19th week of gestation….This study is the first to assess associations of birth outcomes with multiple urinary biomarkers of exposure to triazine and chloroacetanilide herbicides. Evidence of associations with adverse birth outcomes raises particular concerns for countries where atrazine is still in use.”

A Human Rights Assessment of Aerial Herbicide Applications Near and Adjacent To Triangle Lake, Oregon
A 2011 report released by the Environment and Human Rights Advisory examined exposure to herbicides applied aerially to forestlands near homes and the helath impacts on those families. “Urine samples of thirty-four residents, including children, taken after Weyerhaeuser’s  April 8 and April 19 aerial sprays, were provided to laboratories at Emory University and tested for the presence of atrazine and 2,4-D. All thirty-foururine samples tested positive for both herbicides. Two examples: one adult male’s urine showed a 129% increase in urine atrazine after the aerial applications and a 31% increase in urine 2,4-D, and an adult female resident’s urine showed a 163%increase in urine atrazine, and a 54% increase in urine 2,4-D after the aerial applications, both compared to baseline levels taken some months earlier. Viewed in light of human rights standards, this may raise liability concerns for agencies.”

Acute Pesticide Illnesses Associated with Off-Target Pesticide Drift from Agricultural Applications: 11 States, 1998–2006
This 2011 study published in Environmental Health Perspectives “estimated the incidence of acute illnesses from pesticide drift from outdoor agricultural applications and characterized drift exposure and illnesses.” The results show “From 1998 through 2006, we identified 2,945 cases associated with agricultural pesticide drift from 11 states. Our findings indicate that 47% were exposed at work, 92% experienced low-severity illness, and 14% were children (< 15 years). The annual incidence ranged from 1.39 to 5.32 per million persons over the 9-year period. The overall incidence (in million person-years) was 114.3 for agricultural workers, 0.79 for other workers, 1.56 for nonoccupational cases, and 42.2 for residents in five agriculture-intensive counties in California. Soil applications with fumigants were responsible for the largest percentage (45%) of cases. Aerial applications accounted for 24% of cases. Common factors contributing to drift cases included weather conditions, improper seal of the fumigation site, and applicator carelessness near nontarget areas.” The study concluded that “Agricultural workers and residents in agricultural regions had the highest rate of pesticide poisoning from drift exposure, and soil fumigations were a major hazard, causing large drift incidents. Our findings highlight areas where interventions to reduce off-target drift could be focused.

Are Oral Contraceptives a Significant Contributor to the Estrogenicity of Drinking Water?
The 2011 study reviews the literature regarding various sources of estrogens, in surface, source and drinking water, to determine whether OCs were the source of estrogen in surface waters, with an emphasis on the active molecule that comes from OCs. The authors find that industrial and agricultural sources not only discharge estrogens, but they also release other harmful chemicals, which can mimic estrogen. These compounds add to the overall estrogenic pollution of our water supplies. The study identifies pesticides as a contributing factor of estrogen in water. Several pesticides are known as xenoestrogens, which mimic estrogen and disrupt the endocrine system. The study "Are Oral Contraceptives a Significant Contributor to the Estrogenicity of Drinking Water?" was published in Environmental Science and Technology. Read Beyond Pesticides' Daily News entry from December, 2010.

Menstrual cycle characteristics and reproductive hormone levels in women exposed to atrazine in drinking water
This 2011 report published in Environmental Research “examined the relationship between exposure to atrazine in drinking water and menstrual cycle function including reproductive hormone levels. Women 18-40 years old residing in agricultural communities where atrazine is used extensively (Illinois) and sparingly (Vermont) answered a questionnaire (n=102), maintained menstrual cycle diaries (n=67), and provided daily urine samples for analyses of luteinizing hormone (LH), and estradiol and progesterone metabolites (n=35). Markers of exposures included state of residence, atrazine and chlorotriazine concentrations in tap water, municipal water and urine, and estimated dose from water consumption. Women who lived in Illinois were more likely to report menstrual cycle length irregularity (odds ratio (OR)=4.69; 95% confidence interval (CI): 1.58-13.95) and more than 6 weeks between periods (OR=6.16; 95% CI: 1.29-29.38) than those who lived in Vermont. Consumption of >2 cups of unfiltered Illinois water daily was associated with increased risk of irregular periods (OR=5.73; 95% CI: 1.58-20.77). Estimated "dose" of atrazine and chlorotriazine from tap water was inversely related to mean mid-luteal estradiol metabolite. Atrazine "dose" from municipal concentrations was directly related to follicular phase length and inversely related to mean mid-luteal progesterone metabolite levels. We present preliminary evidence that atrazine exposure, at levels below the US EPA MCL, is associated with increased menstrual cycle irregularity, longer follicular phases, and decreased levels of menstrual cycle endocrine biomarkers of infertile ovulatory cycles.”

Assessment of Risk to Drinking Water from Turf Pesticide Runoff
This 2011 study published by Cornell University  performed a human health risk assessment “on pesticide runoff from lawns and golf courses for 9 U.S. locations using a fate and transport modeling program. Pesticide concentrations for 37 turf pesticides registered for application on golf courses were compared to drinking water standards… For fairways, both iprodione and 24-D produced acute and chronic risk at more than 3 locations. Potential risk was only found for myclobutanil applications to greens and tees. MCPA, oxadiazon and 24-D applied to lawns posed both acute and chronic risks. The highest concentrations were seen with acephate applied to fairways with acute RQ≥0.01 in 4 locations and in oxadiazon applied to lawns in Houston with chronic RQ≥0.01. Pesticide concentrations were highest for fairways and lowest for greens. Greatest impacts were observed in areas of high annual precipitation rates and long growing seasons whereas lowest impacts were observed in areas of low precipitation rates. These results suggest that persons living in heavy rainfall areas may have higher exposures of turf pesticide in their drinking water than would be predicted by EPA risk assessments.”

Nitrate intake and the risk of thyroid cancer and thyroid disease
The 2010 study published in Epidemiology investigated the association of nitrate intake from public water supplies and diet with the risk of thyroid cancer and self-reported hypothyroidism and hyperthyroidism in a cohort of 21,977 older women in Iowa who were enrolled in 1986 and who had used the same water supply for >10 years. The results show a nearly three-fold increase in thyroid cancer risk for women with more than five year’s use of a public water supply that had nitrate levels of 5 milligrams per liter (mg/L) or above.  Increasing intake of dietary nitrate is associated with an increased risk of thyroid and with the prevalence of hypothyroidism, but not hyperthyroidism. Researchers suggest that nitrate inhibits the thyroid gland’s ability to use iodide required for thyroid functioning. The study "Nitrate intake and the risk of thyroid cancer and thyroid disease" was published in Epidemiology. Read Beyond Pesticides’ Daily News entry from July, 2010.

Agrichemicals in surface water and birth defects in the United States
This 2009 study published in Acta Paediatrica investigated “if live births conceived in months when surface water agrichemicals are highest are at greater risk for birth defects…” The study concluded that “Elevated concentrations of agrichemicals in surface water in April-July coincided with higher risk of birth defects in live births with LMPs April-July. While a causal link between agrichemicals and birth defects cannot be proven from this study an association might provide clues to common factors shared by both variables.” Read Beyond Pesticides’ Daily News entry from April, 2009.

Dioxins from triclosan increasingly found in water
This 2010 study published in Environmental Science and Technology examined sediment core samples that contained pollution accumulation records from the past 50 years from Lake Pepin, a part of the Mississippi River 120 miles downstream from the Minneapolis-St. Paul metro area. The sediment samples were then analyzed for triclosan, the four dioxins that are derived from triclosan and the entire family of dioxin chemicals. Researchers found that though levels of all other dioxins have dropped by 73-90% over the last thirty years, the levels of four different dioxins derived from triclosan have risen by 200-300%. Read Beyond Pesticides’ Daily News entry May, 2010.

Well-water consumption and Parkinson ’s disease in rural California
This 2009 study published in Environmental Health Perspectives examined 26 pesticides and six in particular, “selected for their potential to pollute groundwater or because they are of interest for PD, and to which at least 10% of our population were exposed.” Those are: diazinon, chlorpyrifos, propargite, paraquat, dimethoate, and methomyl. Propargite exposure was most closely correlated with incidence of PD, with a 90 percent increase in risk. It is still used in California, mostly on nuts, corn, and grapes. Chlorpyrifos, once a common household chemical, was linked to an 87 percent higher risk of PD. While it was banned for residential use in 2001, it is stilled commonly used on California crops. Methomyl also increased risk by 67 percent. Read Beyond Pesticides’ Daily News entry August, 2009.

Residential runoff as a source of pyrethroid pesticides to urban creeks
This 2009 study published in Environmental Pollution examined “runoff from residential neighborhoods around Sacramento, California…over the course of a year. Pyrethroids were present in every sample. Bifenthrin, found at up to 73 ng/L in the water and 1211 ng/g on suspended sediment, was the pyrethroid of greatest toxicological concern, with cypermethrin and cyfluthrin of secondary concern. The bifenthrin could have originated either from use by consumers or professional pest controllers, though the seasonal pattern of discharge from the drain was more consistent with professional use as the dominant source. Stormwater runoff was more important than dry season irrigation runoff in transporting pyrethroids to urban creeks. A single intense storm was capable of discharging as much bifenthrin to an urban creek in 3h as that discharged over 6 months of irrigation runoff.”


Water and Environmental Health Research

Pyrethroid and organophosphate pesticide-associated toxicity in two coastal watersheds (California, USA)
This 2012 study published in Environmental Toxicology and Chemistry studied changes to organophosphates and pyrethroids concentration and toxicity. “Ten stations were sampled in four study areas, one with urban influences, and the remaining in agriculture production areas. Water toxicity was assessed with the water flea Ceriodaphnia dubia, and sediment toxicity was assessed with the amphipod Hyalella Azteca Toxicity identification evaluations and chemical analysis demonstrated that the majority of the observed water toxicity was attributed to organophosphate pesticides, particularly chlorpyrifos, and that sediment toxicity was caused by mixtures of pyrethroid pesticides. The results demonstrate that both agriculture and urban land uses are contributing toxic concentrations of these pesticides to adjacent watersheds…”

Almond organophosphate and pyrethroid use in the San Joaquin Valley and their associated environmental risk
This 2012 study published in Journal of Soils and Sediment used the California Pesticide Use Report database to determine the organophosphate (OP) and pyrethroid use trends in the San Joaquin Valley for almonds from 1992 to 2005. OP pesticide use has been declined in any measurement in almonds. However, a converse result was found for pyrethroid pesticide. Pyrethroid posed less environmental risk than OP in this study. The results indicate that “pesticide uses in intensive agriculture and their associated environmental risks pose negative impacts on biodiversity.”

Detections of the Neonicotinoid Insecticide Imidacloprid in Surface Waters of Three Agricultural Regions of California, USA, 2010–2011
This 2012 study published in the Bulletin of Environmental Contamination and Toxicology collected 75 surface water samples from three agricultural regions of California and were “analyzed for the neonicotinoid insecticide imidacloprid. Samples were collected during California's relatively dry-weather irrigation seasons in 2010 and 2011. Imidacloprid was detected in 67 samples (89%); concentrations exceeded the United States Environmental Protection Agency's chronic invertebrate Aquatic Life Benchmark of 1.05 μg/L in 14 samples (19%). Concentrations were also frequently greater than similar toxicity guidelines developed for use in Europe and Canada. The results indicate that imidacloprid commonly moves offsite and contaminates surface waters at concentrations that could harm aquatic organisms following use under irrigated agriculture conditions in California.”

The Fungicide Chlorothalonil Is Nonlinearly Associated with Corticosterone Levels, Immunity, and Mortality in Amphibians
The 2011 study published in Environmental Health Perspectives reveals that the most widely used fungicide in the U.S., chlorothalonil, is lethal to frogs even at low doses. Chemical pollution, according to the researchers, is considered the second greatest threat to aquatic and amphibious species in the U.S. Because many vital systems of amphibians are similar to those in humans, researchers believe that amphibians may be an underused model for studying the impacts of chemicals in the environment on human health and set out to quantify amphibian responses to chlorothalonil. Read Beyond Pesticides’ Daily News entry April, 2011.

Impact of ant control technologies on insecticide runoff and efficacy
This 2010 study published in Pest Management Science examined post-treatment runoff from control of ants around homes, particularly of bifenthrin or fipronil spray. “During 2007, the resulting runoff from the bifenthrin spray in the irrigation water had a mean concentration of 14.9 microg L(-1) at 1 week post-treatment and 2.5 microg L(-1) at 8 weeks, both high enough to be toxic to sensitive aquatic organisms. In comparison, treatments with bifenthrin granules resulted in no detectable concentrations in the runoff water after 8 weeks. The mean concentration for fipronil used as a perimeter spray was 4.2 microg L(-1) at 1 week post-treatment and 0.01 microg L(-1) at 8 weeks, with the first value also suggesting a potential for causing acute aquatic toxicity to sensitive organisms. During 2008, insecticide runoff was reduced by using spray-free zones and pin stream perimeter applications.”

Pesticide transport with runoff from creeping bentgrass turf: Relationship of pesticide properties to mass transport
This 2010 study published in Environmental Toxicology and Chemistry designed experiments to “measure the quantity of pesticides in runoff from creeping bentgrass (Agrostis palustris) turf managed as golf course fairway to gain a better understanding of factors that influence chemical availability and mass transport. Less than 1 to 23% of applied chloropyrifos, flutolanil, mecoprop-p (MCPP), dimethylamine salt of 2,4-dichlorophenoxyacetic acid (2,4-D), or dicamba was measured in edge-of-plot runoff when commercially available pesticide formulations were applied at label rates 23 +/- 9 h prior to simulated precipitation (62 +/- 13 mm). Time differential between hollow tine core cultivation and runoff did not significantly influence runoff volumes or the percentage of applied chemicals transported in the runoff. With the exception of chlorpyrifos, all chemicals of interest were detected in the initial runoff samples and throughout the runoff events. Chemographs of the five pesticides followed trends in agreement with mobility classifications associated with their soil organic carbon partition coefficient (K(OC).) Data collected from the present study provides information on the transport of chemicals with runoff from turf, which can be used in model simulations to predict nonpoint source pollution potentials and estimate ecological risks.”

Atrazine induces complete feminization and chemical castration in male African clawed frogs (Xenopus laevis)
This 2010 study published in Proceedings of the National Academy of Sciences, “demonstrates the reproductive consequences of atrazine exposure in adult amphibians. Atrazine-exposed males were both demasculinized (chemically castrated) and completely feminized as adults. Ten percent of the exposed genetic males developed into functional females that copulated with unexposed males and produced viable eggs. Atrazine-exposed males suffered from depressed testosterone, decreased breeding gland size, demasculinized/feminized laryngeal development, suppressed mating behavior, reduced spermatogenesis, and decreased fertility.” The study "Atrazine induces complete feminization and chemical castration in male African clawed frogs (Xenopus laevis)" was published in . Read Beyond Pesticides’ Daily News entry March, 2010.

Triclosan persistence through wastewater treatment plants and its potential toxic effects on river biofilms
This 2010 study published in Aquatic Toxicology examined the role of triclosan emitted from wastewater treatment plants in the Mediterranean on algae and bacteria. “A set of experimental channels was used to examine the short-term effects of triclosan (from 0.05 to 500μgL⁻¹) on biofilm algae and bacteria. Environmentally relevant concentrations of triclosan caused an increase of bacterial mortality with a no effect concentration (NEC) of 0.21μgL⁻¹. Dead bacteria accounted for up to 85% of the total bacterial population at the highest concentration tested. The toxicity of triclosan was higher for bacteria than algae. Photosynthetic efficiency was inhibited with increasing triclosan concentrations (NEC=0.42μgL⁻¹), and non-photochemical quenching mechanisms decreased. Diatom cell viability was also affected with increasing concentrations of triclosan. Algal toxicity may be a result of indirect effects on the biofilm toxicity, but the clear and progressive reduction observed in all the algal-related endpoints suggest the existence of direct effects of the bactericide. The toxicity detected on the co-occurring non-target components of the biofilm community, the capacity of triclosan to survive through WWTP processes and the low dilution capacity that characterizes Mediterranean systems extend the relevance of triclosan toxicity beyond bacteria in aquatic habitats.”

Pyrethroid insecticides in urban salmon streams of the Pacific Northwest
This 2010 study published in Environmental Pollution took “Sediments from Oregon and Washington streams... to determine if current-use pyrethroid insecticides from residential neighborhoods were reaching aquatic habitats, and ifthey were at concentrations acutely toxic to sensitive invertebrates. Approximately one-third of the 35 sediment samples contained measurable pyrethroids. Bifenthrin was the pyrethroid of greatest concern with regards to aquatic life toxicity, consistent with prior studies elsewhere.”

Atrazine reduces reproduction in fathead minnow (Pimephales promelas)
This 2010 study published in Aquatic Toxicology exposed fathead minnows to atrazine and observed for effects on egg production, tissue abnormalities and hormone levels. Fish were exposed to concentrations ranging from zero to 50 micrograms per liter of atrazine for up to 30 days, below EPA water quality guidelines. Researchers found normal reproductive cycling was disrupted by atrazine and fish did not spawn as much or as well when exposed to atrazine; total egg production was lower in all atrazine-exposed fish, as compared to the non-exposed fish, within 17 to 20 days of exposure; and atrazine-exposed fish spawned less and there were abnormalities in reproductive tissues of both males and females. Read Beyond Pesticides’ Daily News June, 2010.

Effects of nanoparticles on fathead minnow (Pimephales promelas) embryos
This 2010 study published in Ecotoxicology exposed fathead minnows, at several stages of their development, to varying concentrations of either suspended or stirred nanoparticle solutions for 96 hours. When the nanosilver was allowed to settle, the solution became several times less toxic, but still caused malformations in the minnows. With or without sonication, nanosilver caused irregularities, including head hemorrhages and edema, and was ultimately lethal.  Researchers found that nanosilver that is sonicated or suspended in solution is toxic and even lethal to fathead minnows, an organism that is often used to measure toxicity on aquatic life. Read Beyond Pesticides’ Daily News entry March, 2010.

A Qualitative Meta-Analysis Reveals Consistent Effects of Atrazine on Freshwater Fish and Amphibians
This 2009 study published in Environmental Health Perspectives analyzes more than 100 scientific studies conducted on atrazine, researchers found sublethal indirect effects of atrazine on fish and amphibians particularly for disruption of their immune, hormone, and reproductive systems. “Atrazine reduced size at or near metamorphosis in 15 of 17 studies and 14 of 14 species. Atrazine elevated amphibian and fish activity in 12 of 13 studies, reduced antipredator behaviors in 6 of 7 studies, and reduced olfactory abilities for fish but not for amphibians. Atrazine was associated with a reduction in 33 of 43 immune function end points and with an increase in 13 of 16 infection end points. Atrazine altered at least one aspect of gonadal morphology in 7 of 10 studies and consistently affected gonadal function, altering spermatogenesis in 2 of 2 studies and sex hormone concentrations in 6 of 7 studies. Atrazine did not affect vitellogenin in 5 studies and increased aromatase in only 1 of 6 studies.” Read Beyond Pesticides’ Daily News October, 2009.

Organohalogen contaminants and metabolites in the brain of dolphins from the western North Atlantic
The 2009 study published in Environmental Pollution identified several contaminants including organochlorine pesticides (OCs), polychlorinated biphenyls (PCBs), hydroxylated-PCBs (OH-PCBs), methylsulfonyl-PCBs (MeSO2-PCBs), polybrominated diphenyl ether (PBDE) flame retardants, and OH-PBDEs, in the cerebrospinal fluid and cerebellum gray matter of several species of marine mammals including the short-beaked common dolphins, Atlantic white-sided dolphins and the gray seal. PCBs were found in alarmingly high concentrations. Researchers found parts per million concentrations of PCBs in the cerebrospinal fluid of a gray seal. Read Beyond Pesticides’ Daily News entry May, 2009.

Widespread occurrence of intersex in black basses (Micropterus spp.) from U.S. rivers, 1995–2004
This 2009 study published in Aquatic Toxicology evaluated intersex occurrence in freshwater fishes for nine river basins in the US. “Testicular oocytes (predominantly male testes containing female germ cells) were the most pervasive form of intersex observed, even though similar numbers of male (n=1477) and female (n=1633) fish were examined. Intersex was found in 3% of the fish collected. The intersex condition was observed in four of the 16 species examined (25%) and in fish from 34 of 111 sites (31%). Intersex was not found in multiple species from the same site but was most prevalent in largemouth bass (Micropterus salmoides; 18% of males) and smallmouth bass (M. dolomieu; 33% of males). The percentage of intersex fish per site was 8-91% for largemouth bass and 14-73% for smallmouth bass. The incidence of intersex was greatest in the southeastern United States, with intersex largemouth bass present at all sites in the Apalachicola, Savannah, and Pee Dee River Basins. Total mercury, trans-nonachlor, p,p'-DDE, p,p'-DDD, and total PCBs were the most commonly detected chemical contaminants at all sites, regardless of whether intersex was observed.”

A cocktail of contaminants: how mixtures of pesticides at low concentrations affect aquatic communities
This 2009 study published in Oecologia  “examined how a single application of five insecticides (malathion, carbaryl, chlorpyrifos, diazinon, and endosulfan) and five herbicides (glyphosate, atrazine, acetochlor, metolachlor, and 2,4-D) at low concentrations (2-16 p.p.b.) affected aquatic communities composed of zooplankton, phytoplankton, periphyton, and larval amphibians (gray tree frogs, Hyla versicolor, and leopard frogs, Rana pipiens). Using outdoor mesocosms, I examined each pesticide alone, a mix of insecticides, a mix of herbicides, and a mix of all ten pesticides.”

Toxicity of two insecticides to California, USA, anurans and its relevance to declining amphibian populations
The 2009 study published in Environmental Toxicology and Chemistry examined the chronic toxicity of two of the insecticides most commonly used in the Central Valley of California- chlorpyrifos and endosulfan, to larval Pacific treefrogs (Pseudacris regilla) and foothill yellow-legged frogs (Rana boylii), the amphibians with declining populations that live and breed in meadows surrounding the Sierra Nevada. Researchers exposed larvae to the pesticides from Gosner stages 25 to 26 through metamorphosis. The estimated median lethal concentration (LC50) for chlorpyrifos was 365"g/L in P. regilla and 66.5"g/L for R. boylii. Researchers found that endosulfan was more toxic than chlorpyrifos to both species, and tadpoles of both species developed abnormalities when exposed to high endosulfan concentrations. Endosulfan also affected the growth and development rates in both species. Read Beyond Pesticides’ Daily News July, 2009.

Maternal transfer of xenobiotics and effects on larval striped bass in the San Francisco Estuary
This 2008 study published in PNAS found “Results from 8 years of field and laboratory investigations indicate that sublethal contaminant exposure is occurring in the early life stages of striped bass in the San Francisco Estuary, a population in continual decline since its initial collapse during the 1970s. Biologically significant levels of polychlorinated biphenyls, polybrominated diphenyl ethers, and current-use/legacy pesticides were found in all egg samples from river-collected fish. Developmental changes previously unseen with standard methods were detected with a technique using the principles of unbiased stereology. Abnormal yolk utilization, brain and liver development, and overall growth were observed in larvae from river-collected fish.”

Community and ecosystem responses to a pulsed pesticide disturbance in freshwater ecosystems
his 2008 study published in Ecotoxicology used outdoor aquatic mesocosms, to determine the impact of a common pesticide Sevin with the active ingredient carbaryl on freshwater plankton food webs. “We monitored the response of microbial, phytoplankton, and zooplankton communities in addition to oxygen concentrations. Carbaryl concentrations peaked shortly after Sevin application and degraded quickly and treatment differences were undetectable after 30 days. Zooplankton richness, diversity, abundance, and oxygen concentrations all decreased in pulsed treatments, while phytoplankton and microbial abundance increased. Zooplankton composition in the high pesticide treatment consisted primarily of rotifers as compared to dominance by copepods in the other three treatments. While many of the community and ecosystem properties showed signs of recovery within 40 days after the pulsed pesticide disturbance, important and significant differences remained in the microbial, phytoplankton and zooplankton communities after the pesticide degraded.”

An Unforeseen Chain Of Events: Lethal Effects Of Pesticides On Frogs At Sublethal Concentrations
This 2008 study published in Ecological Applications “examined how low concentrations (10-250 microg/L) of a globally common insecticide (malathion) applied at various amounts, times, and frequencies affected aquatic communities containing zooplankton, phytoplankton, periphyton, and larval amphibians (reared at two densities) for 79 days. All application regimes caused a decline in zooplankton, which initiated a trophic cascade in which there was a bloom in phytoplankton and, in several treatments, a subsequent decline in the competing periphyton. The reduced periphyton had little effect on wood frogs (Rana sylvatica), which have a short time to metamorphosis. However, leopard frogs (Rana pipiens) have a longer time to metamorphosis, and they experienced large reductions in growth and development, which led to subsequent mortality as the environment dried. Hence, malathion (which rapidly breaks down) did not directly kill amphibians, but initiated a trophic cascade that indirectly resulted in substantial amphibian mortality. Importantly, repeated applications of the lowest concentration (a "press treatment" consisting of seven weekly applications of 10 microg/L) caused larger impacts on many of the response variables than single "pulse" applications that were 25 times as great in concentration. These results are not only important because malathion is the most commonly applied insecticide and is found in wetlands, but also because the mechanism underlying the trophic cascade is common to a wide range of insecticides, offering the possibility of general predictions for the way in which many insecticides impact aquatic communities and the populations of larval amphibians.


Identifying primary stressors impacting macroinvertebrates in the Salinas River (California, USA): Relative effects of pesticides and suspended particles
This 2006 study published in Environmental Pollutione examined amphipods, baetid mayfly and the midge to determine which stressors were most likely responsible for the toxicity and observed in the Californian River. “The current study shows that pesticides are more important acute stressors of macroinvertebrates than suspended sediments in the Salinas River.”

Hermaphroditic, demasculinized frogs after exposure to the herbicide atrazine at low ecologically relevant doses
This 2002 study published in Proceedings of the National Academy of Sciences “examined the effects of atrazine on sexual development in African clawed frogs (Xenopus laevis). Larvae were exposed to atrazine (0.01-200 ppb) by immersion throughout larval development, and we examined gonadal histology and laryngeal size at metamorphosis. Atrazine (> or =0.1 ppb) induced hermaphroditism and demasculinized the larynges of exposed males (> or =1.0 ppb). In addition, we examined plasma testosterone levels in sexually mature males. Male X. laevis suffered a 10-fold decrease in testosterone levels when exposed to 25 ppb atrazine. We hypothesize that atrazine induces aromatase and promotes the conversion of testosterone to estrogen. This disruption in steroidogenesis likely explains the demasculinization of the male larynx and the production of hermaphrodites. The effective levels reported in the current study are realistic exposures that suggest that other amphibian species exposed to atrazine in the wild could be at risk of impaired sexual development. This widespread compound and other environmental endocrine disruptors may be a factor in global amphibian declines.”