16
Apr
Pesticide Pollution in Recreational Lakes Documented
(Beyond Pesticides, April 16, 2021) Recent research, published in Environmental Pollution in late 2020, examines levels and persistence of pesticide pollution in recreational lakes. The study finds: (1) concentrations of the neonicotinoid imidacloprid at levels exceeding ecotoxicity limits for aquatic invertebrates in a recreational lake that receives predominately urban runoff, and (2) that pesticide residues persist in the studied lakes throughout the growing season. Based on their findings, the scientists emphasized the importance of stricter regulation of insecticide compounds, and of better education about their impacts. Beyond Pesticides maintains that neonicotinoid pesticides should be banned for several reasons, not least of which is the extreme damage they cause to pollinators.
The goal of the study was to evaluate potential ecosystem exposure to pesticide contamination in Midwestern recreational lakes, as well as the persistence of pesticide residues in those water bodies over the course of the growing season. Study authors hypothesized that watersheds with significant agricultural land uses would have higher concentrations of pesticides compared to largely urban and herbaceous watersheds.
This research, out of the University of Nebraska–Lincoln and the University of Kentucky, looked to evaluate the occurrence of neonicotinoid and organothiophosphate insecticides, and some fungicides, in three lakes with differing dominant land uses in watersheds of Nebraska’s Lower Platte River Basin. The land uses of the three context watersheds were classified as: herbaceous (mostly grassy prairie, shrubs, and open vegetated areas, and excluding forested or woody areas); urban (primarily residentially developed areas); and agricultural (largely production fields planted with soybeans and corn). Each watershed had multiple kinds of land uses within it, but the designated categorical use was dominant compared to the others. Researchers aimed to assess the occurrence of commonly used pesticides, such as neonicotinoid and organothiophosphate insecticides, as well as strobilurin and acylamino acid fungicides, in the lakes.
Two of the 12 compounds the study assessed — imidacloprid and clothianidin — are very commonly used neonicotinoids (neonics) found in both urban and agricultural areas. Imidacloprid is used to treat soil, seeds, and foliage of vegetable and cotton crops to control sucking insects such as rice hoppers, aphids, thrips, whiteflies, various turf and soil insects, and some beetles. It is also used in pet flea treatments and in home gardens. Clothianidin is used similarly, on food (e.g., corn, soybean, leafy greens, and fruit) and non-food crops, as well as on turf and residential areas. It is used to control many of the same insects as imidacloprid targets, and is likewise applied to leaves, soil, or seeds.
Clothianidin is toxic for bees, birds, and fish and other aquatic organisms, and so, is very harmful to these creatures’ ecosystems and to biodiversity. Imidacloprid shares those characteristics and more: it also harms human health, wildlife, domestic pets, water quality, and the environment broadly. The fungicide azoxystrobin is toxic to fish and other aquatic organisms.
Imidacloprid was the first neonic sold in the U.S. and is the most commonly deployed insecticide globally. Annual agricultural use in the U.S. in 2014 tallied to 2,204,623 pounds. Use of clothianidin, largely on corn crops, rose to 3,747,858 pounds yearly by that same year. Neonics comprise a class of pesticide used intensively in many parts of the world. Though they are applied to plant foliage, or directly to soils as a drench, the dominant use globally is as a seed treatment. Neonic pesticides are banned or restricted in the European Union, France, Germany, and Italy; some states have also worked to rein in their use, but federal regulation in the U.S. continues to be wholly inadequate.
The study methodology included use of multiple sampling techniques — both “grab” sampling and “passive” sampling (in which the collection unit remains in the water for a period of time) — in the subject lakes and in inlet streams contributing to them. Multiple sampling periods were conducted. These strategies enabled averaging of concentrations and, therefore, more comprehensive assessments of pesticide concentrations than would have been gotten through “snapshot” or grab sampling alone. The paper notes, “Concentrations were then used with runoff volume estimates to calculate the total load of individual pesticides entering the monitored lake during each sampling period.”
The study co-authors note that, although low-level concentrations of pesticides are pervasive in both rural-agricultural and urban waterways, recent reports have found pesticides in urban and agricultural lakes, including Midwestern national park lakes (as well as in adjacent groundwater). A 2011 USGS survey found that 61% of agricultural streams and 90% of urban streams had at least one detectable pesticide at levels exceeding aquatic-life benchmarks.
The findings of the research include:
- Azoxystrobin, clothianidin, and imidacloprid were the most frequently detected compounds via both sampling methods at all locations; concentrations were significantly different depending on dominant watershed land use and sampling method.
- Significantly higher pesticide concentrations were found in the urban watershed compared to the others, particularly for imidacloprid. The paper distinguishes between “pesticides” (used for “plant protection”) and “biocides” (used for other, non-plant-protection purposes, such as on domestic pets or in homes), though in some instances, a biocide and a pesticide (or insecticide) can be chemically identical. (Domestic use of biocides is less regulated, generally, than is use of pesticides, according to the co-authors.)
- Whereas concentrations of imidacloprid exceeding acute aquatic toxicity benchmarks were observed in the urban lake for only two of the six sampling periods, chronic aquatic toxicity benchmarks (for aquatic invertebrates) were exceeded for imidacloprid in that lake for every sampling period, and in the agricultural lake for four of the six sampling periods.
- Though clothianidin (and thiamethoxam) in the agricultural lake showed the highest concentrations among compounds sampled, those levels remained well below both chronic and acute toxicity limits for both pesticides.
- Sampling from contributing inlets to the lakes showed imidacloprid concentrations exceeding chronic toxicity limits in both the agricultural and urban settings.
The finding of higher concentrations in the urban watershed was unexpected by the researchers, and did not support their working hypothesis that agricultural watershed bodies would evidence the highest pesticide concentrations. The co-authors wrote: “Overall, the urban watershed was the primary pesticide contributor per unit area. We hypothesize that this is likely due to limited pesticide outreach programs for homeowners regarding ideal timing and quantity of biocide applications along with absent regulations for pesticide applications in nonagricultural areas.”
They added specificity to that explanation: “Directly upstream to the urban lake was a dog park and next to the urban lake there was a golf course. Imidacloprid is used in flea prevention treatment for dogs, rapidly metabolized, and excreted primarily through urine. Further, imidacloprid is often used to protect trees and shrubs from the insect species such as emerald ash borer, grasshoppers, and weevils and is commonly used in the region for insect prevention on residential lawns and golf courses. Therefore, the high concentrations of imidacloprid was suspected to be from biocide usage in the predominately urban watershed from contributions of domestic animals, lawn and tree care, and golf course maintenance.”
Beyond Pesticides has covered the contributions of golf course maintenance, flea treatments for pets, and lawn maintenance to the pesticide problem in the U.S., and advocated for alternative approaches that reduce or eliminate the toxicity issues related to these activities (see more on solutions for golf courses, flea treatment, and lawns). The study co-authors conclude: “Findings from this study are critical for preventing and mitigating potential effects of pesticides, specifically applied as biocides in urban landscapes, from entering and persisting in recreational lakes.”
Impacts of neonics on pollinators, and on bees, in particular, are well documented, and worldwide, detectable levels of pesticides in water resources continue to rise, driven primarily by runoff from agricultural fields treated with herbicides, pesticides, and fungicides. Beyond Pesticides has reported extensively on pesticide water pollution, including by neonics, noting that: “Neonicotinoid insecticides are detected regularly in sampling of the nation’s waterways at concentrations that exceed acute and chronic toxicity values for sensitive organisms.” See this deep dive, “Poisoned Waterways,” from Beyond Pesticides’ Spring 2017 issue of Pesticides and You.
The United Kingdom has banned use of several classes of pesticides — including neonics — but the U.S. Environmental Protection Agency (EPA) continues to allow use of thousands of demonstrably harmful pesticide compounds, and nods to “protection” by maintaining databases of acute and chronic toxicity in order to identify “areas of concern” for registered pesticides. This anemic approach continues to allow the myriad water quality, health, ecosystem, and biodiversity harms of pesticide use to continue.
The comprehensive solution to these harms is getting off the toxic pesticide treadmill through a transition from chemically intensive land management (including in agriculture) to management through organic systems. The benefits to water quality, never mind every other impacted sector of the environment and human health, would be enormous and systemic.
As Beyond Pesticides wrote some years ago, “Growing food with a reliance on toxic pesticides has resulted in the nation’s waterways being heavily contaminated with toxic chemicals. Organic farming demonstrates clearly that relying on toxic chemical inputs for crop yields is not only unnecessary, but serves to protect waterways and public health from chemical pollution. Creating healthy soils, which is the foundation of organic systems, conserves water, nurtures fertility, leads to less surface runoff, and reduces the need for nutrient input. With less toxic pesticide use, organic farming helps to protect the quality of the nation’s waterways.”
Source: https://www.sciencedirect.com/science/article/abs/pii/S0269749120370883
All unattributed positions and opinions in this piece are those of Beyond Pesticides.
Absolutely! Pesticides have numerous beneficial effects. These include crop protection, preservation of
June 8th, 2021 at 2:09 pmfood and materials and prevention of vector borne diseases