Human Health Risks from Neonic Pesticides: 7 Questions Answered

NRDC scientist Dr. Jennifer Sass recently coauthored two articles on the acute and chronic human health risks from neonicotinoid (neonic) pesticides.

Below, she's provided the answers to seven key questions about the nitty-gritty info in the articles, along with relevant science and policy context and some recommended next steps. 

1. What are neonicotinoid pesticides?

They’re the world’s most widely used insecticides, and they act on the brain and nervous system.

Neonics have complicated chemical names—acetamiprid, clothianidin, dinotefuran, imidacloprid, and thiamethoxam—but they all share a simple toxic mechanism. They disrupt the cells of the brain and nervous system by mimicking nicotine and binding to the same nerve cell receptor that nicotine does. But while nicotine will only bind to nerve receptors for a few minutes, neonics stay attached, overstimulating and harming or destroying the nerve cell. 

Neonics are the most widely used class of insecticides in the United States and worldwide. They are commonly sprayed on food crops; spread across lawns, gardens, parks, and golf courses; used to treat bed bugs; and infused into pet flea and tick collars. However, the biggest use of neonics (about three-quarters of total neonic use in the United States) is as a coating on crop seeds, which are dispersed across more than 150 million acres nationwide and evade most federal and state pesticide regulation due to legal loopholes. 

2. What happens to neonics in the environment? 

They are persistent in soil, move with water, and get inside fruits and vegetables.

Neonics are long-lasting and move easily through the environment—building up year over year and spreading throughout soil, water, wildlife, and our bodies. Today, few parts of our environment or food system are not touched by neonics. 

Since neonics are systemic, meaning that they work by penetrating plant tissues, they make all parts of the plant—from the root to the fruit—toxic to insects. This also means that they are not washed off or peeled away from the fruits and vegetables they contaminate. This leaves chemical residues inside treated foods, including those frequently consumed by pregnant women and children, such as apples, cherries, grapes, kale, lettuce, pears, potatoes, and spinach. 

3. Can my family and I be exposed to neonics?

People are exposed to neonic residues in foods and tap water, and nursing infants can be exposed through breast milk.

Infants can be exposed to neonics through contaminated breast milk and from infant formula reconstituted with neonic-contaminated tap water (conventional chlorination treatment can’t remove neonics from tap water and may even make it more toxic!). 

Neonics are among the most common pesticides detected in our bodies. For example, a 2022 paper found neonics in the bodies of more than 95 percent of pregnant women tested across the country, with levels rising higher and higher over the four-year study. 

Pregnant women exposed to neonics can pass on those chemicals: Studies report that neonics can pass through the human placenta directly to the developing fetus. In a small study of children, neonics have been measured in the fluid of the brain and spinal cord, in blood, and in urine, indicating that children are exposed to neonics and that the pesticides can gain access to sensitive neural organs and tissues.

The human results are strengthened by laboratory studies in rodents showing that neonics penetrate the fetal blood-brain barrier and access the fetal brain.

4. How can neonics affect my health? 

Neonics can cause immediate (acute) poisoning effects and long-lasting (chronic) neurodevelopmental harm.

Our two recent papers add to the growing body of evidence that neonics threaten health, including in humans. 

Acute poisoning: Exposure to neonics can cause acute (short-term) poisoning effects, ranging from mild to severe, and even death in extreme cases.

Unsurprisingly, the signs and symptoms of nicotine poisoning are similar to neonic pesticide poisoning. These include: nausea and vomiting; increased salivation; abdominal pain; sweating; increased blood pressure and increased heart rate; loss of muscle control; dizziness and headache; in extreme cases, seizures and possibly death. 

While the Bayer Corporation—a major neonic manufacturer—has long touted that the “toxicity of neonicotinoids to mammals and humans is very low,” our new papers reveal that neonics’ neurotoxic properties pose a serious (and likely growing) threat to human health.

Several years ago, USA Today reported on the shocking news of almost 75,000 pets poisoned by neonic-infused pet collars, including nearly 1,700 deaths. And what harms our pets also harms people.

Our paper reports on more than 800 human poisoning incidents that we discovered in the most recent five years of publicly available data (2018–2022) in the EPA’s Incident Data System. Common symptoms included headaches, dizziness, nausea, and skin irritation from using lawn and garden insect repellents, home pest treatments for bed bugs or roaches, and pet products made with imidacloprid or dinotefuran. There were also four deaths reported, two associated with clothianidin and two with acetamiprid. 

While already terribly high, the true neonic poisoning count is likely much higher than we found, since we excluded data on work-related poisonings (e.g., for landscapers or pest control specialists) and from other relevant federal and state databases to avoid double counting. Moreover, the vast majority of poisonings go unreported as people often don’t know they were exposed to a pesticide, don’t think or know how to report it, or don’t know what product they were exposed to. 

Chronic effects: Exposure to neonics during early life development increases the risk of long-term or even permanent adverse effects on the brain.

Our second paper—a collaboration with Dr. Nathan Donley at the Center for Biological Diversity and Bill Freese at the Center for Food Safety—finds that neonics pose significant threats of long-term neurological and developmental harm to children, especially to those exposed in the womb. 

The paper reports on the results of the unpublished rodent toxicology studies that neonic manufacturers submitted to the EPA to get initial approval to sell neonic products. The studies show that rats exposed to neonics in the womb were born with neurotoxic nicotine-like defects, including reduced brain size. Statistically significant brain shrinkage was observed for all five major neonicotinoid chemicals, with statistical analysis from the study reporting 95 percent confidence that these severe effects were due to the neonic treatment. 

The two brain regions that showed neonic-associated reductions—the corpus callosum and caudate putamen—also tend to be smaller in people diagnosed with attention deficit hyperactivity disorder (ADHD) and in children of mothers who smoked during pregnancy. This suggests a possible link between neonic exposure in the womb and ADHD (see our paper for details and additional references).

The results of laboratory rodent studies are strengthened by several studies linking neonic exposures in human populations to elevated risks of neurodevelopmental abnormalities. In fact, a systematic review of published and publicly available scientific studies on unintentional human exposures to neonics (such as from agricultural uses or consumer products) reported a link between those exposures and an elevated risk of developmental or neurological harm.  This includes a study that found a statistically significant association between prenatal exposure to imidacloprid (a neonic) and autism spectrum disorder (OR=2.0, 95% CI: 1.0, 3.9). 

Studies link prenatal neonic exposure in rats to brain shrinkage and in people to autism-like symptoms and other effects. While these findings are disturbing, they shouldn’t be surprising. Neonics are designed to be toxic to the brain and nervous system, which is especially sensitive to neurotoxic chemicals during early life development. That is why we have warnings for tobacco products, which contain nicotine, to be avoided during pregnancy. 

Although each individual study has limitations, taken together, they add up to many loud warning bells. 

5. The EPA already has all of this information. What is it doing to reduce the health risks from neonics? 

The EPA’s proposed exposure limits fail to follow the science or the law to provide adequate protection for children and pregnant women.

The agency has largely ignored these worrying results. Although brain thinning was observed for all the rats exposed to a high dose of neonics, the EPA largely let pesticide manufacturers off the hook when they failed to submit the low- and medium-dose data that the EPA normally requires when impacts to the brain are shown. For thiamethoxam, the only neonic chemical for which complete data was provided, brain tissue thinning was shown at all three dose levels.

Alarmingly, and without evidence, the EPA concluded that only the brain thinning at the high doses were related to the effects of neonics. That finding has real consequences for our health because it affects all sorts of safety decisions concerning the neonics, including the amount of neonic residues allowed by the EPA in our food and drinking water.

Worse, the EPA reduced health protections further by failing to apply a safety factor required under the Food Quality Protection Act that specifically protects children, who are more vulnerable to chemical exposures than adults. 

Stated plainly, the EPA relied on incomplete data—most of which showed brain shrinkage and other neurological harms—to set weak and unsupported safety standards for neonics that clearly fail to protect our children’s health.

6. What can I do to protect my loved ones? 

You can choose organic foods, avoid applying neonic products around your home, and urge leaders to limit the use of these harmful chemicals. 

You can buy organic foods to avoid harmful pesticides, including the neonics; organic is good for your health and the environment (see more in NRDC’s report). And you can care for your lawn, garden, and pets without neonic products.

7. What is NRDC doing?

NRDC experts are working every day, using science and the law to reduce harmful and unnecessary neonic uses—and we are gaining ground!

NRDC has had significant success in helping to advance state-level policies that limit or cancel unnecessary and harmful uses of neonics. For example, NRDC helped to pass landmark legislation in New York to restrict the use of neonic coatings on corn, soybean, and wheat seeds, eliminating up to 90 percent of the neonics entering the state’s environment annually. We are working hard to build on this success in other states. In Minnesota, the NRDC Action Fund and its partners have filed a legal petition demanding that the state act to stop harmful, unnecessary pesticide pollution.

We are also raising awareness about the risks that neonics pose to human health in the scientific literature. While our papers may be the most recent, they certainly won’t be the last. Meaningful action from state and federal regulators is long overdue to protect people and our environment from neonics. And NRDC won’t stop fighting until the dangerous overuse of brain-toxic neonics is reined in.