12
Sep
Levels of Pesticides Still a Concern for Aquatic Life in U.S. Rivers and Streams
(Beyond Pesticides, September 12, 2014) A new U.S. Geological Survey (USGS) report finds that levels of pesticides continue to be a concern for aquatic life in many of the Nation’s rivers and streams in agricultural and urban areas. The study, which documents pesticide levels in U.S. waterways for two decades (1992-2011), finds pesticides and their breakdown products in U.S. streams more than 90 percent of the time. Known pesticide water contaminants, such as atrazine, metolachlor, and simazine, continue to be detected in streams more than 50 percent of the time, with fipronil being the pesticide most frequently found at levels of potential concern for aquatic organisms in urban streams.
According to the USGS report, “An Overview Comparing Results from Two Decades of Monitoring for Pesticides in the Nation’s Streams and Rivers, 1992—2001 and 2002—2011,” featured in the journal, Environmental Science and Technology and part of the agency’s ongoing National Water-Quality Assessment Program, the proportion of streams with one or more pesticides that exceed an aquatic-life benchmark (or guideline) is similar between the two decades for streams and rivers draining agricultural and mixed-land use areas, but much greater during the 2002-2011 for streams draining urban areas. 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.
For urban areas, 90 percent of the streams exceeded a chronic aquatic life benchmarks. Fipronil, metolachlor, malathion, cis-permethrin, and dichlorvos exceeded chronic aquatic life benchmarks for more than 10 percent of the streams. For agriculture and mixed land-use streams, the overall percent of streams that exceeded a chronic aquatic life benchmarks was very similar between the decades. For urban land-use streams, the percent of streams exceeding a chronic aquatic life benchmark during 2002—11 nearly doubled that seen during 1992—2001. The reason for this difference, according to the USGS researchers, was the inclusion of fipronil monitoring during the second decade. Across all land-use streams, the percent of streams exceeding a chronic aquatic life benchmark for fipronil during 2002—11 was greater than all other insecticides during both decades. Fipronil, an insecticide that disrupts the central nervous system of insects, is commonly used in pet products to kill fleas on dogs and cats, and on lawns to control ants and termites. It is highly toxic to fish and aquatic invertebrates, highly toxic to bees, highly toxic to upland game birds, and is moderately toxic to waterfowl.
“The information gained through this important research is critical to the evaluation of the risks associated with existing levels of pesticides,” said William Werkheiser, USGS Associate Director for Water.
Over half a billion pounds of pesticides are used annually in the U.S., mostly in agriculture and to reduce insect-borne disease, but some of these pesticides are occurring at concentrations that are identified by the government as a concern for aquatic life. Unfortunately, the potential for adverse effects on aquatic life is likely underestimated in these results because resource constraints limited the scope of monitoring to less than half of the more than 400 pesticides currently used in agriculture each year and monitoring focused only on pesticides dissolved in water.
Aquatic organisms like algae and fish face numerous risks from pesticide exposures, even at low levels. In fact, USGS scientists identified pesticides as one of the contaminants the Potomac River linked to intersex-fish (male fish producing eggs) observed there. Atrazine, one of the most commonly used herbicides in the world, has been shown to affect reproduction of fish at concentrations below U.S. Environmental Protection Agency’s (EPA) water-quality guidelines. Concentrations of atrazine commonly found in agricultural streams and rivers have been associated with a reduction in reproduction and spawning, as well as tissue abnormalities. Just last month, EPA finalized a settlement to restore no-spray buffer zones around waterways to protect imperiled salmon and steelhead from five toxic pesticides. The settlement follows litigation filed by Earthjustice, representing the Pacific Coast Federation of Fishermen’s Associations, the Northwest Coalition for Alternatives to Pesticides, and Defenders of Wildlife, back in 2010 that called for EPA adoption of reasonable fish protections from the insecticides.
USGS has also published findings on the neonicotinoid class of pesticides, finding that they are persistent and prevalent in streams throughout the Midwestern U.S. According to that report, neonicotinoid use has increased dramatically throughout the country, especially in the Midwest over the last decade, where treated corn seeds are planted on millions of acres. The use of neonicotinoids clothianidin, imidacloprid, and thiamethoxam in these states means that their residues were most frequently detected. This class of pesticides is subject to a lawsuit filed by Beyond Pesticides and others, and has been receiving increased attention by scientists and beekeepers exploring the possible link between pesticides and bee decline. For more on neonicotinoids, visit www.beeprotective.org
According to USGS, since 1992 there have been widespread trends in concentrations of individual pesticides, some down and some up, mainly driven by shifts in pesticide use due to regulatory changes, market forces, and introduction of new pesticides. “Levels of diazinon, one of the most frequently detected insecticides during the 1990s, decreased from about 1997 through 2011 due to reduced agricultural use and the U.S. Environmental Protection Agency’s regulatory phase-out of urban uses,” said, Wesley Stone, USGS hydrologist.
Last year, USGS for the first time released a national assessment depicting the distribution and trends of pesticide use from 1992-2009, with agricultural use maps of 459 pesticides. The maps show how many pounds per square miles were used for each year, and include details about which crops they were used on. Previous USGS reports maintain that the presence of pesticides in U.S. waterways remains a concern for aquatic life. Additionally, the agency also reports that more than 20 percent of private domestic wells sampled nationwide contain at least one contaminant at levels of potential health concern, as well as in streams used as a source for public water systems.
Unfortunately, water quality criteria for the protection of aquatic life and human health in surface water were set for only a handful of pesticides. In 2012, EPA added new health and environmental benchmarks for acute pesticide effects, however, benchmarks are notoriously limited in fully assessing risks because of ongoing deficiencies in analyzing the complexities associated with chemical exposure, specifically a failure to evaluate the effects of chemical mixtures, synergistic effects, and health effects associated with consistent low-dose exposure. If benchmarks are exceeded, the state or local water municipality can consider how frequently the benchmarks are exceeded and the magnitude of the exceedance in other samples. Exceeding the benchmark consistently means that aquatic life and human health may be at risk from continued exposures.
The USGS says its National Water-Quality Assessment Program is continually working to fill these data gaps by adding new pesticides that come into use, such as the neonicotinoid and pyrethroid insecticides, improving characterization of short-term acute exposures, and enhancing evaluations of sediment and other environmental media.
Visit our Threatened Waters page and learn how organic land management practices contribute to healthy waters in the article, “Organic Land Management and the Protection of Water Quality.”
All unattributed positions and opinions in this piece are those of Beyond Pesticides.
Source: USGS Press Release
