The use of neonicotinoid insecticides are being heavily restricted throughout Europe because of their collateral impacts on bees. Here in the United States, where the EPA has staunchly resisted legal pressure from beekeepers and environmentalists to follow the European Union's lead and suspend their use, neonics have become the hottest class of chemicals in the country's chemical-obsessed agricultural industry. They're popular in part because they're systemic pesticides, meaning they can be applied to soil or a seed, and then they become incorporated into the growing plant. The plant itself becomes poisonous to insects, eliminating or reducing the need to spray insecticides. Researchers have previously discovered that the pesticides can also endanger fish, birds, and other wildlife.
In just a decade, neonics have almost entirely replaced organophosphates and other insecticides on Midwestern corn and soy fields. The most popular varieties used in these fields are clothianidin, imidacloprid, and thiamethoxam—which are the neonic varieties that are more or less banned in Europe right now.
Results of a federal government study warn that the popularity of the poisons could also be endangering aquatic insects—along with fish and other water-loving wildlife.
That's obviously bad news for bees and butterflies. But results of a federal government study, which was recently published online by Environmental Pollution, warn that the popularity of the poisons could also be endangering aquatic insects—along with fish and other water-loving wildlife. The pesticides aren't staying on the farmed fields; they're leaching and flowing into watersheds.
Government researchers sampled water last year at eight locations along rivers and streams in Iowa and at one site along its Nebraskan border. They tested the water samples for the presence of different types of different neonics. At least one of these chemicals was found in 60 of the 79 samples. Each of the eight sites sampled, including the Mississippi and Missouri rivers, was contaminated with at least one type of neonic pesticide.
All but one of the 60 positive samples contained detectable levels of clothianidin. Clothianidin is the most heavily used neonic in the region—almost 500,000 pounds were used by Iowa farmers alone last year. It can also be formed as the lesser-used thiamethoxam breaks down. It's extremely persistent in the environment, with a half-life in soil of 18 months. In freshwater, the half-life is almost six weeks.
Concentrations of clothianidin in some samples were as high as 257 nanograms per liter. Its median concentration was 8ng/L.
Are those safe amounts? Could they be endangering aquatic life? What about human health? We asked Dana Kolpin, a U.S. Geological Survey research hydrologist who collected many of the samples and helped write up the results.
"We don’t know," Kolpin says. "I think that's definitely the next question. They're at high enough concentrations that it's definitely worth looking at whether there are any concerns for invertebrates, or even higher organisms."
Given the EPA's lackadaisical disregard for the precautionary principle in pesticide permitting, and explosive growth in the use of these chemicals on American farms, it seems the answers to these questions will be found in the environment—not just inside laboratories.