First the Bees, Then the Birds, and Now the Fish Are at Risk From a Particularly Toxic Pesticide
The United States Geological Survey has found widespread contamination of Midwestern streams and rivers with neonicotinoids, putting fish at risk from a class of insecticide implicated in the mass die-off of honeybees, which pollinate a third of the world’s food supply.
Neonicotinoids, also called neonics, account for 40 percent of the global pesticide market and are used extensively throughout the U.S. and Europe. Most corn and soybean crops grown in the American Midwest are treated with neonics. Scientific studies have documented that neonics can harm bees, birds, and other wildlife.
The new research adds to a growing body of scientific evidence that neonics are one of the most persistent, prevalent, and potentially toxic pesticides since DDT, which was banned in the U.S. in 1972.
Neonics are a so-called systemic pesticide that is absorbed into a plant’s roots, stems, leaves, flowers, pollen, and nectar. Farmers can spray plants with neonics, but seeds are now routinely treated with the nerve poison, meaning that as the plant grows the pesticide remains part of the flora.
Bees and other pollinators are at particular risk, as they eat neonic-contaminated pollen and nectar. Several scientific studies have found that even nonlethal doses of neonics can weaken bees’ immune system, making them vulnerable to disease and parasites.
USGS scientists collected 79 water samples from nine waterways, including the Mississippi and Missouri rivers, during the 2013 growing season. They focused on Iowa, a major grower of corn and soybeans, and targeted three types of neonics: clothianidin, thiamethoxam, and imidacloprid.
In 2013, farmers applied 474,000 pounds of clothianidin, 156,000 pounds of thiamethoxam, and 110,000 pounds of imidacloprid to crops. Inevitably, irrigation water and rainstorms washed the pesticides into nearby streams and rivers. Neonics dissolve quickly in water and can be carried far, according to the report. They also persist in the environment for years.
The researchers detected clothianidin in 75 percent of the waterways sampled, while thiamethoxam was present in 47 percent and imidacloprid in 23 percent.
“This was the first broad-scale investigation of multiple neonicotinoid insecticides in waterways in the Midwestern U.S. and is one of the first conducted within the entire United States,” Kathryn Kuivila, the leader of the USGS research team, said in an email. “So one of the next steps is for toxicologists and ecologists to assess the consequences of these levels for the observed periods of time.”
So are fish in danger?
That depends on whose data you accept.
According to the U.S. Environmental Protection Agency, clothianidin has chronic toxic effects on fish at concentrations of 1,100 nanograms per liter of water. The threshold for imidacloprid is 1,050 ng/l. (The EPA has not set a baseline for thiamethoxam.)
However, another study determined that imidacloprid becomes chronically toxic for fish at a far lower concentration—just 20 ng/l.
In Iowa, the USGS found maximum imidacloprid concentrations twice that—42.7 ng/l. Maximum clothianidin concentrations were 257 ng/l.
“We are planning future studies to look at the fate and potential effects of neonics in the environment,” said Kuivila.
But Doug Gurian-Sherman, a senior scientist at the Center for Food Safety, an advocacy group that has sued the federal government and the state of California over approval of neonics, said the time has come for action.
“As the body of evidence against neonicotinoids continues to grow, our government has fewer and fewer excuses for their inaction,” he said. “If meaningful action is not taken, we may be headed toward a second Silent Spring.”