(Beyond Pesticides, April 5, 2017) A new study, Occurrence of Neonicotinoid Insecticides in Finished Drinking Water and Fate during Drinking Water Treatment, has detected neonicotinoids, a class of insecticides known for their detrimental effects on bees, in treated drinking water. This marks the first time that these insecticides have been found in water sourced straight from the tap. Federal regulators have not yet addressed safe levels of neonicotinoids in drinking water, so at this point, any detection of these chemicals is cause for concern.
The study authors “report for the first time the presence of three neonicotinoids in finished drinking water and demonstrate their general persistence during conventional water treatment.” Drinking water samples “collected along the University of Iowa treatment train” over a seven week period, May through July, 2016 directly after corn and soy planting, find three neonicotinoids, clothianidin, imidacloprid, and thiamethoxam at levels ranging from 0.24 to 57.3 ng/L (nanogams per liter). The University of Iowa tap water is run through a water treatment plant that uses conventional treatment methods. In contrast, the Iowa City water treatment methods (granular activated carbon filtration) result in substantially lower levels of the neonicotinoids. Additionally, the researchers found that extensive transformation of clothianidin occurs (>80% in 1.5 hrs) during chlorination, which is a disinfectant process frequently used in many water treatment facilities. This transformation potentially causes toxic transformation products.
Neonicotinoids are water soluble and persist in the environment. As a result, they are likely to end up in runoff from agricultural fields where they are applied and contaminate surface water and groundwater. The source water for both the University of Iowa and Iowa City comes from the Iowa River. Since levels of neonicotinoids are detected in tap water that has undergone water treatment, it can be deduced that there are neonicotinoids in the source water, the Iowa River, at higher levels. The fact that neonicotinoids are being detected in rivers is not a new phenomenon. In 2014, the U.S. Geological Survey (USGS) published study results that found neonics persistent and prevalent in streams throughout the midwest. The USGS findings identify a serious threat to keystone species in the aquatic food web, putting ecosytems at risk.
A 2015 report found that, “[T]here is more and more evidence that widespread use of neonicotinoids has severe effects on a range of organisms that provide ecosystem services like pollination and natural pest control, as well as on biodiversity.” A February 2017 study finds that exposure to imidacloprid at environmentally relevant levels results in slight delays in metamorphosis in the tadpoles of the wood frog, which can increase mortality and population decline. Another study finds that neonics indirectly hurt larger organisms, such as birds, by reducing insect populations such as mosquitos and beetles. Imidacloprid is toxic to aquatic organisms at 10 to 100 ng/L if the organisms are exposed or long periods of time. In early January of this year, the U.S. Environmental Protection Agency (EPA), in regulating the sale and use of pesticides in the U.S., released the ecological (aquatic) assessment for imidacloprid, which finds elevated risks to aquatic organisms. This preliminary risk assessment of imidacloprid finds that, “[C]oncentrations of imidacloprid detected in streams, rivers, lakes and drainage canals routinely exceed acute and chronic toxicity endpoints derived for freshwater invertebrates.” However, imidacloprid’s aquatic assessment has not been published in the Federal Register to solicit public comments, which are necessary to ensure transparency and independent vetting of EPA’s science and risk assessment conclusions. It is not clear whether EPA, under the leadership of Administrator Scott Pruitt, will follow through on the regulatory review, and, if it does, may reverse earlier scientific findings of the agency, as it did recently with a dramatic reversal on a proposal to remove the the highly neurotoxic insecticide chlorpyrifos, which is widely used in food production.
In light of the shortcomings of federal action in the U.S. to protect organisms critical to ecosystem health, it is left up to us to act. You can pledge to stop using neonicotinoids and other toxic pesticides. Sign the pollinator protection pledge today. Beyond Pesticides also advocates the adoption of organic land management practices and policies by local communities that eliminate the use of toxic pesticides in our environment. If you would like to get involved in other ways, such as interacting with the scientists who work on studies like these, come to our National Pesticide Forum! This year’s forum is being held in Minneapolis, MN on April 28-29. Michelle Hladik, PhD, is one of the researchers and authors of this study, and will be presenting. Click here to learn more and register.
All unattributed positions and opinions in this piece are those of Beyond Pesticides.