Neonicotinoids 101: The Effects on Humans and Bees

Neonics are a class of synthetic, neurotoxic insecticides that are used on agricultural crops, lawns, gardens, golf courses, and in flea and tick pet treatments. Developed in the mid-1990s, they are now the single-most popular insecticide class in the United States. 

Neonics work by permanently binding to insects’ nerves, overstimulating and destroying them. Exposed insects often exhibit uncontrollable shaking and twitching, followed by paralysis and, eventually, death. Even at nonlethal doses, neonics can weaken critical functions, such as an insect’s immune system, navigation, stamina, memory, and fertility.

The reason neonics are bad is the same reason they’re used in the first place: To insects, they’re some of the deadliest pesticides ever created. They kill indiscriminately, exterminating not only “pests” but also countless butterflies, bees, and earthworms too. 

In addition, neonics are considered “systemic” pesticides. This means they can be applied directly to the soil (as a “drench”) around a plant’s roots or as a coating on a plant seed, which the plant then soaks up as it grows. That makes the plant itself—including its nectar, pollen, leaves, stems, and fruit—toxic. The problem is that only a small portion of the neonics make it into the target plant, leaving the vast majority in the soil.

Once in the soil, neonics remain there for years, and rain or irrigation water can easily carry them long distances to contaminate new soil, plant life, and water supplies. Given neonics’ widespread use, the result has been enormous ecosystem contamination. A 2015 study by the U.S. Geological Survey found neonic pollution in more than half of the streams it sampled nationwide. 

The reality is that neonics easily work their way up the food chain too. Studies now link neonics to mass losses of birds and the collapse of fisheries. And in 2023, the U.S. Environmental Protection Agency (EPA) made the astounding finding that neonics are driving more than 200 threatened or endangered species toward extinction. 

Despite the threat to our environment, the agriculture industry continues to apply neonics to hundreds of millions of acres every year—in particular, to corn, soybean, and other crop seeds. But science shows these preventative applications are unnecessary, treating pest problems that don’t exist. Worse yet, they can set farmers back by encouraging pest resistance; killing off pollinators, pest predators, and other beneficial bugs; and harming soil health. 

Hundreds of studies, several comprehensive academic assessments, extensive Cornell University research, and even a major pesticide industry–funded field study all point to neonics as a leading cause of massive bee and pollinator die-offs. 

Honeybees, specifically, are likely the “canaries in the coal mine” for the 4,000-plus species of native bees nationwide—such as the rusty-patched bumblebee. In 2017, it became the first bee in the continental United States to be added to the endangered species list. Wild bee loss should matter to everyone because they are also essential crop pollinators. News that apples, blueberries, and cherry crops are now pollinator-limited nationwide will mean less of these favorite fruits.

Neonics mimic nicotine in the nervous system. In fact, just like for the insects they’re designed to target, they impact the same portions of our brains and nervous system as mammals. And these systems in animals and people are critical for healthy brain development, growth, and function. Research links neonic exposures in the womb to birth defects of the heart and brain, autism-like symptoms, and reduced cognitive abilities. Adult exposures are also associated with lower testosterone and sperm quality and count, altered insulin regulation, and changes to fat metabolism. 

Worryingly, neonic exposure may be hard for many to avoid. Human biomonitoring studies detected neonics in the bodies of about half the U.S. population on any given day. In biomonitoring of pregnant women, researchers reported neonics in more than 95 percent of those tested, with levels rising. 

How do we encounter these dangerous pesticides? Unfortunately, neonics regularly pollute water sources, and traditional chlorination treatment typically fails to remove them from tap water and may even make the tap water more toxic. These pesticides also contaminate our food. Neonic residues are found in 86 percent of U.S. honey, and they show up in fruits and vegetables, including many kids’ favorites like apples, cherries, strawberries, potatoes, and leafy greens. Because neonics are systemic, they are actually in the fruit and vegetables themselves, so they can’t be rinsed off or peeled away.

While Europe has banned outdoor uses of the major neonic chemicals since 2018, and Canada has moved to significantly restrict some of their most widespread uses, little has changed in the United States. The EPA has long been asleep at the wheel, allowing widespread and business as usual neonic use, even as alarming new science rolls in. NRDC successfully sued the agency to consider neonics’ impacts to endangered pollinators and other species and has petitioned regulators to rein in neonic use to protect children’s health. But meaningful change continues to be pushed back.

That’s left the work to the states, which have been leading the way in the last several years, including with the support of NRDC and our activists. States like Maine, Nevada, and New Jersey led the way with bans on neonic lawn and garden products; more recently, New York and Vermont have enacted nation-leading programs to rein in neonic coatings on corn, soybean, and wheat seeds. With states like California, Connecticut, and Minnesota taking action too, the nation is charting a path toward commonsense curbs on reckless use of these dangerous pesticides. 

This story was originally published May 25, 2022, and has since been updated with new information and links.