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Among nearly 800 white-tailed deer spleens mailed to a Minnesota state lab in 2019 were three from Barry Sampson, who hunts with his nephews on his forested property. His samples—along with 61 percent of the total from varied landscapes across the state—were found to contain pesticides called neonicotinoids. “I am puzzled at how this got into the deer,” he says, “and I’m not happy about it.”

, released in March, suggest how ubiquitous these chemicals have become in the environment, says Michelle Carstensen, the study’s leader at the Minnesota Department of Natural Resources. Neonicotinoids, also called neonics, began replacing older bug-repelling chemicals in the arsenals of farmers, homeowners, and groundskeepers in the early 1990s. They are now the most widely used class of insecticides globally, found on nearly all conventionally grown U.S. corn fields, as well as flea collars, bed bug products, golf courses, and gardens.

In the past decade neonics have come for their documented role in the decline of honeybee populations around the world. Newer evidence is revealing that the chemicals can harm a wider range of wildlife.

Last year University of Illinois agricultural economist Madhu Khanna that correlated rising usage to annual declines of grassland and insectivorous birds in the United States, by 4 and 3 percent a year, respectively. In another study, captive deer exposed to neonics—at far lower levels than found in the Minnesota wild deer spleens—suffered reduced fawn survival, altered organ weights, and developmental and behavioral abnormalities. Another ominous case in a Japanese lake: After neonics were applied to surrounding rice fields, plankton numbers plummeted and triggered a collapse of smelt and eel fisheries.

Given such findings, Khanna and others feel that policies to control the chemicals’ use are falling short. “Current regulations are likely not enough to prevent larger ecosystem impacts,” she says.

Concerns are also growing about potential human health effects, and far more research is needed, says George Washington University public health scientist Melissa Perry. The U.S. Centers for Disease Control and Prevention estimates that about half of the population is regularly exposed—most likely, scientists say, through food and drinking water. California is now considering adding several neonics to Proposition 65, which requires health warning labels on products.

Since 2018 an emerging consensus over widespread hazards has driven Canada regulators to propose restricting some outdoor applications, and the European Union to go further and ban the use of three common neonics on all crops. While some U.S. states are also acting, such as in a recent to restrict outdoor consumer uses, advocates say the U.S. EPA proposed weak, minimal restrictions when the Trump administration greenlit continued use of five popular neonics in 2020.

“It’s pretty much business as usual,” says Natural Resources Defense Council attorney Dan Raichel, of the proposal. The agency, he says, now has time to “change course” before an October 2022 final deadline. He hopes to see these chemicals prohibited in some cases, especially where safer options are available such as in lawn care.

Advocates say another critical move requires closing a loophole that impedes EPA’s ability to regulate the chemicals’ most pernicious and prevalent mode of deployment: as water-soluble seed coatings absorbed by a plant as it grows. “The very feature that allows them to be systemic in plants allows them to be leached out of fields when it rains,” says Pennsylvania State University entomologist John Tooker, who co-authored a paper warning of risks to food webs. As little as 2 percent of the pesticide on a seed may make it into a plant, studies suggest; the rest ends up in soil, groundwater, or rivers and lakes.

Regulating or banning a class of pesticides that farmers and other industries rely upon remains fraught with challenges, and in some cases data show crop yields could take a hit. But declines of birds, bees, and entire ecosystems carry high costs, too: Insect pollinators contributed $34 billion to the U.S. economy in 2012. Likewise, when bird numbers and diversity decline, pests increase.

In Minnesota Sampson answered the call for spleens because he’s concerned for wildlife, and he hopes to see agencies follow the science. Tooker sees the rise of neonics—and potential consequences of continued inaction—through the lens of another clarion call: “We didn’t learn very well from Rachel Carson’s book.”

This story originally ran in the Summer 2021 issue as “Beyond Bees.”​ To receive our print magazine, become a member by .