23
Sep
Neonicotinoid Insecticides Keep Poisoning California Waterways, Threatening Aquatic Ecosystems
(Beyond Pesticides, September 23, 2022) According to a September 15 Environment California press release, California Department of Pesticide Regulation (CDPR) data confirm more bad news on neonicotinoid (neonic) contamination: nearly all urban waterways in three counties show the presence of the neonic imidacloprid at levels above the U.S. Environmental Protection Agency’s (EPA’s) chronic benchmark for harm to aquatic ecosystems; in five other counties, well over half showed its presence at similar levels. Neonic use is strongly correlated with die-offs and other harms to a variety of bees and pollinators, and to other beneficial organisms. These startling metrics will make the state’s efforts to protect such organisms even more challenging, according to Environment California (EC). See Beyond Pesticides’ Poisoned Waterways report for a deep dive on neonics and their impacts in U.S. rivers, lakes, and streams.
The data represent 405 surface water samples taken between 2000 and 2020; those from urban waterways in Los Angeles, Orange, and San Diego counties showed that nearly 92% are contaminated at EPA benchmark violative levels; in Alameda, Contra Costa, Placer, Sacramento, and Santa Clara counties, 58% of waterways showed such levels. Many of the counties with significant contamination are in the central coast and southern regions of the state. Some of this contamination no doubt comes from intensive agricultural use of imidacloprid, causing migration of the compound into waterways, but some may also be from non-agricultural uses — such as flea prevention for pets and building pest control products — common in developed urban areas. According to CDPR, there are 253 pesticide products containing imidacloprid registered for use in California.
Environment California’s webpage hosts an interactive map of sampling sites (across much of the state) that are represented in those imidacloprid metrics. The percentage of samples from each location that contained the compound range from 0 to 91.67. The EC page notes that “very few samples were tested for imidacloprid prior to 2010. . . . [and that] the percentage of samples that detect imidacloprid remains fairly constant over time.” Detailed results can be found in CDPR’s Surface Water Database.
The 2017 Beyond Pesticides report mentioned above cited similarly alarming results in other of the state’s waterways a decade ago: “A 2012 [CDPR] study using 2010 and 2011 surface water monitoring data from three agricultural regions in the state finds imidacloprid in 89% of the samples collected. . . . In the three agricultural regions studied, imidacloprid was detected in 85% of samples in Salinas, 93% in Imperial Valley, and 100% in Santa Maria Valley. These levels exceed currently established chronic aquatic benchmark concentrations.”
Neonicotinoids (such as imidacloprid, acetamiprid, thiamethoxam, clothianidin, and dinotefuran) are a family of insecticides that harm the central nervous systems of insects and can paralyze or kill them, as well as have deleterious effects on baby bee brains. They are used as foliar sprays, plant root drenches, and granules to kill or render impotent a variety of pests — particularly sap-feeding insects, such as aphids, and root-feeding grubs. But a very significant vector for these compounds is through seed coatings, often for commodity crops (e.g., corn, soy, cotton). Ironically, years ago EPA released a report concluding that neonic seed coating provides little or no overall benefit in controlling insects or improving yield or quality in soybean production.
No matter how they are deployed, neonics are systemic pesticides, meaning that plants germinate from coated seeds and/or take up the applied compound through their roots, after which it permeates the entire plant. This makes the plant’s pollen, nectar, guttation droplets, and fruits toxic to creatures that feed on them. Non-target organisms, such as birds, bees, butterflies, and bats, are poisoned when they forage among such contaminated plants. In addition to insects’ exposures through foraging for food, it turns out that soil contaminated by neonics can also harm ground-nesting bees.
Neonics can persist over long periods of time in soils and are highly water soluble; thus, they can be transported via rain and/or irrigation systems into groundwater and waterways. They are detected regularly in sampling of the nation’s waterways at concentrations that exceed acute and chronic toxicity values for sensitive organisms (as laid out in Beyond Pesticides “deep dive” report). Through a 2017 risk assessment, EPA found that “[C]oncentrations of imidacloprid detected in streams, rivers, lakes and drainage canals routinely exceed acute and chronic toxicity endpoints derived for freshwater invertebrates.” Imidacloprid, one of the oldest neonics in commercial use, is especially persistent in aquatic environments and does not biodegrade easily; its half-life in water is generally longer than 30 days.
The neonic contamination of waterways — in California and across the nation — is very concerning because these compounds pose serious threats to keystone aquatic organisms, and can result in a complex, cascading impact on ecosystems. Aquatic insects and crustaceans are highly sensitive to neonicotinoids; the mayfly, a keystone species, has been identified as the most sensitive.
As Beyond Pesticides’ Poisoned Waterways report notes, “Impacts on aquatic invertebrates can have cascading effects on food webs and healthy ecosystem function. [Even] low-level, sublethal exposures can result in decreases in species abundance, altered predator-prey relationships, [and] reduced water filtration and nutrient cycling.” In addition, it points out that current federal aquatic life benchmarks for neonics may underestimate the risks: standard test organisms used by EPA to establish these benchmarks are, by orders of magnitude, more tolerant of neonicotinoid exposure than other vulnerable species.
Beyond impacts on aquatic life, terrestrial insects, pollinators, birds, and bats, neonics — touted by the agrochemical industry as safe for mammals — nevertheless are associated with a host of human health issues, including reproductive and endocrine system harms; possible renal, hepatic, developmental, and neurological damage; and possibly, indirect carcinogenic impacts related to the endocrine system.
In response to this new CDPR dataset, Environment America’s Conservation Program Director Steve Blackledge commented, “Every Californian knows the importance of having access to safe, clean water. Neonics like imidacloprid are causing harm not only to our pollinators and birds on land but also to our aquatic wildlife. Neonics are also being found in our bodies and despite being framed as ‘mammal-safe,’ recent research suggests that neonic exposures may increase the risk of developmental and neurological harms.”
EPA has been extremely negligent in taking protective action against the neonic family of insecticides. Indeed, in March 2022, Beyond Pesticides covered its draft decisions on the registration review of five neonics: imidacloprid, dinotefuran, clothianidin, thiamethoxam, and acetamiprid. We wrote then, “Despite the agency’s own findings of evidence of serious threats to pollinators, aquatic invertebrates, and other wildlife, it issued interim decisions on these neonics . . . that disregard the science on the pesticides’ impacts. EPA appears to be prepared to finalize these registrations. . . . [T]his would, barring further action, extend the use of these harmful compounds for 15 years.” The schedule for the review processes for these compounds can be found here.
California legislators have passed a “Save the Bees Bill,” Assembly Bill 2146, which currently awaits the governor’s signature. The bill aims to end nonagricultural uses of neonics on lawns, golf courses, and home gardens, beginning in 2024. News outlet KSBW8 has opined that if signed, the enacted law “could significantly impact the Central Coast and its agriculture.” No doubt this would also be true for other regions, watersheds, and waterways in the state.
Environment California is encouraging Governor Gavin Newsom to sign the bill ASAP. Said the organization’s state director, Laura Deehan, “We want to make California the next state, and the largest, to take this important step. The bill already passed through the Legislature, so we’re now urging Gov. Newsom to sign the bill into law. We must prioritize the preservation of our pollinators over the short-term convenience of massive pesticide use.”
Beyond Pesticide agrees that Governor Newsom should sign this bill, which would enact some protections in the state against the ravages of neonic use. We encourage readers who live in California to contact the governor to advocate for his signature: 916.445.2841 or via the state website. Other states, localities, and entities have taken action to restrict uses of this class of pesticides, including Maine, Maryland, Massachusetts, Vermont, New York, New Jersey, Portland, Oregon, and Emory University. At the federal level it is imperative that EPA create much stronger regulation of neonics — a ban being the most protective of organisms, ecosystems, public health, and water resources.
All unattributed positions and opinions in this piece are those of Beyond Pesticides.
