Neonicotinoid Pesticides
Neonicotinoids are a class of insecticides that act through neurotoxic effects, binding irreversibly to nicotinic acetylcholine receptors in insects. Minnesota registers five of them: acetamiprid, clothianidin, dinotefuran, imidacloprid and thiamethoxam. Growers apply them as seed coatings and sprays, and they also appear in treatments for livestock and pets. They move through the environment in water, and residues turn up in finished drinking water. Bees are harmed by residues in the nectar and pollen of treated plants. Human health studies are limited, though linked effects include neurological, reproductive and developmental, and immune and cellular effects. The European Union bans three of them for outdoor use, while the United States regulates them through EPA registration review.
What Are Neonicotinoid Pesticides?
Neonicotinoid pesticides are a class of chemicals that act as insecticides through neurotoxic effects. Neonicotinoids bind irreversibly to insect nicotinic acetylcholine receptors. Seven substances belong to the class: acetamiprid, clothianidin, dinotefuran, imidacloprid, nitenpyram, thiacloprid and thiamethoxam. The National Toxicology Program (NIH) scoped these seven substances in 2020. Imidacloprid is a systemic insecticide of the chloronicotinyl neonicotinoid class. Generic production became possible in 2005, when the patents expired on seven neonicotinoids. Five active ingredients are currently registered in Minnesota. Thiacloprid is no longer registered in Minnesota after its registration was cancelled in 2014.
How Do Neonicotinoids Work in Insects?
Neonicotinoids work in insects by binding irreversibly to nicotinic acetylcholine receptors. Neonicotinoids such as clothianidin act on the insect central nervous system as agonists of the same receptor as acetylcholine. Clothianidin activates post-synaptic acetylcholine receptors but does not inhibit AChE. The insecticide is systemic, which means it can move into different parts of the plant. Insects take it up through contact or ingestion of treated plant material. Mammals carry nicotinic acetylcholine receptors in their nervous systems as well. This overlap raises concern that neonicotinoids may affect animals other than insects, including humans. A 2016 study by Larry P Sheets credits their favorable safety profiles to preferential affinity for insect receptor subtypes. Findings at high doses were associated with evidence of systemic toxicity.
Which Neonicotinoids Are Registered for Use?
Neonicotinoids registered for use in Minnesota are acetamiprid, clothianidin, dinotefuran, imidacloprid and thiamethoxam. Neonicotinoids are widely used systemic insecticides in agricultural and urban environments. Minnesota Department of Agriculture data from 2026 list these five active ingredients. Acetamiprid belongs to the chloropyridinyl neonicotinoid insecticides introduced in the early 1990s. Dinotefuran, developed by Mitsui Chemicals, controls aphids, whiteflies, thrips, leafhoppers and cockroaches. Takeda Chemical Industries and Bayer AG developed clothianidin. Nitenpyram and thiacloprid belong to the seven neonicotinoid pesticides scoped for human health evidence. Neither appears on the Minnesota list. Thiacloprid, an insecticide of the neonicotinoid class, dropped off the Minnesota list after its registration was cancelled in 2014. Neonicotinoid seed coatings treated almost all agricultural corn planted in the United States in 2013. About 1/3 of soybeans received them too.
What Are the Main Ways Neonicotinoids Are Applied?
The main ways neonicotinoids are applied are seed coatings, spray applications, and treatments for livestock and pets. Seed coating is the most common route, because the plant absorbs the coating during germination. Key ways include:
- Seed coatings: A layer on the seed that the plant absorbs during germination. Seed coatings reached almost all agricultural corn and about 1/3 of soybeans planted in the United States in 2013. The insecticide is systemic, so it moves into different parts of the plant.
- Spray applications: Sprays that treat row crops, fruits and vegetables. Voluntary BMPs came out of a special registration review on neonicotinoid insecticides and pollinators.
- Livestock and pet treatments: Treatments that control pests such as fleas and lice in livestock and domestic pets. Urban examples include pet products for flea and tick management. Dinotefuran serves as a flea and tick preventive for dogs and a flea preventive for cats, and nitenpyram is used in agriculture and veterinary medicine.
Minnesota agriculture officials with University of Minnesota Extension stated in 2019 that neonicotinoid insecticides are systemic.
How Do Neonicotinoids Move Through the Environment?
Neonicotinoids move through the environment in water. Neonicotinoids are very water soluble and freely transport into surface and groundwater. Residues reach pollinators through pesticide drift and contaminated surface water. Contaminated plant parts carry them too, namely pollen, nectar and spray residue on leaves. Three neonicotinoid insecticides, clothianidin, imidacloprid and thiamethoxam, are detected annually in rivers and streams. Agricultural and urban environments both receive these widely used systemic insecticides. Minnesota monitoring covers over 180 pesticide-related chemicals in groundwater and surface water, including several neonicotinoid insecticides and degradates. A 2025 study in Environmental science & technology examines transformation products of neonicotinoids. These products show potential greater environmental persistence and toxicity than their parent compounds.
Are Neonicotinoid Residues Found in Drinking Water?
Yes. Neonicotinoids are found as residues in finished drinking water. Trace amounts of neonics appeared in finished drinking water in Iowa in 2017. Public health practitioners raised concern. Darrin A Thompson’s 2020 study found neonicotinoids to be ubiquitous in the environment, drinking water, and food. Low-level exposure is commonly documented below acceptable daily intake standards. The same review notes the potential for cumulative chronic exposure. Further study is necessary to fully understand their risks to humans.
Are Neonicotinoids Harmful to Bees?
Yes. Neonicotinoids are harmful to bees through exposure from residues in nectar and pollen in the flowers of treated plants. The European Food Safety Authority identified a number of risks to bees from three neonicotinoid insecticides in 2013. Field studies show an acute effect on honey bees exposed to thiamethoxam through guttation fluid. Limited information was available for pollinators other than honey bees. A 2012 bumblebee study reported that neonicotinoid pesticide reduces bumble bee colony growth and queen production. Thiacloprid toxicity is unlike imidacloprid and clothianidin, which have demonstrated very high to high acute toxicity to bees. A 2020 study by Sydney A Cameron describes factors that negatively impact bumble bee health. A 2018 study by Nathalie Steinhauer covers the drivers of colony losses. It finds that quantifying risk factor impact at the colony level is at times elusive and in some cases unpractical. Further risks to bees cannot be excluded without imposing further restrictions, so the EU limited thiamethoxam on 29 May 2018.
Are Neonicotinoids Dangerous to Human Health?
It depends. Human health studies on whether neonicotinoids are dangerous to human health are limited. A 2017 review in Environmental health perspectives identified eight studies on the human health effects of neonic exposure. Their findings on chronic exposure are suggestive but methodologically weak. Three acute-exposure studies in that review described 1,280 poisoning cases and two fatalities. A limited body of evidence was identified for hazard assessment, because the published studies assessed different health outcomes. Neonicotinoids show poor penetration of the mammalian blood-brain barrier. Darrin A Thompson of the University of Iowa reports that documented low-level exposure commonly stays below acceptable daily intake standards. Larry P Sheets published a study in Critical reviews in toxicology that found no common effects among the neonicotinoids. Nitenpyram is highly selective towards the variation of the nicotinic receptor that insects possess.
What Health Effects Have Been Linked to Neonicotinoids?
Health effects that have been linked to neonicotinoids include neurological, reproductive and developmental, and immune and cellular effects. Neonicotinoids in animal studies indicate possible genotoxicity, cytotoxicity and impaired immune function. Andria M Cimino’s 2017 review found four general population studies linking chronic exposure to adverse developmental or neurological outcomes. Key effects include:
- Neurological effects: Insecticides including neonicotinoids exert significant adverse effects on hippocampal neurogenesis. Acetamiprid and imidacloprid produce nicotine-like effects on cerebellar neurons from neonatal rats. Limited epidemiological data report neurological symptoms.
- Reproductive and developmental effects: Animal studies indicate reduced growth and reproductive success at low concentrations. Limited epidemiological data report birth defects, yet no common effects consistent with developmental neurotoxicity were identified among the neonicotinoids.
- Immune and cellular effects: Animal data indicate impaired immune function. Limited epidemiological data report oxidative genetic damage, and findings at high doses were associated with evidence of systemic toxicity.
A 2020 study by M Florencia Rossetti reports significant adverse effects on hippocampal neurogenesis from both herbicides and insecticides.
How Are Neonicotinoids Regulated in the United States?
Neonicotinoids are regulated in the United States through registration review at the Environmental Protection Agency. The United States Environmental Protection Agency has a goal to review the pesticides in this class in the same timeframe. That ensures consistency across the class. US EPA documents from 2017 and 2024 set the timetable. Previous assessments identified potential risks to pollinators. The Agency planned final pollinator risk assessments and proposed interim decisions for mid-2018. The public comment period begins when the Federal Register notice is published and stays open for 60 days. An updated pollinator risk assessment and a proposed interim decision came out in January 2020 for imidacloprid and clothianidin. A registration review amended proposed interim decision is anticipated in 2025. As the Agency completes risk assessments for the neonicotinoids, it will pursue risk mitigation, as appropriate. In July 2013, Oregon temporarily restricted the use of dinotefuran pending an investigation into a large bee kill.
Are Neonicotinoids Banned for Outdoor Use in the European Union?
Yes. Neonicotinoids are banned for outdoor use in the European Union for three substances: imidacloprid, clothianidin and thiamethoxam. European Commission (EUR-Lex) regulations from 2018 prohibit all outdoor uses. Only uses as insecticide in permanent greenhouses, or for treating seeds intended only for permanent greenhouses, may be authorised. Regulation 2018/783 covers imidacloprid, 2018/784 covers clothianidin and 2018/785 covers thiamethoxam, all adopted on 29 May 2018. The resulting crop must stay its entire life cycle within a permanent greenhouse, so that it is not replanted outside. For clothianidin, the exception limits use to permanent greenhouses. France banned most neonicotinoid insecticides, including acetamiprid, in 2018 to protect pollinators. Thiacloprid has been banned in France since September 1, 2018. Germany suspended authorization for the use of clothianidin on corn in 2009.
How Can People Reduce Their Exposure to Neonicotinoids?
To reduce their exposure to neonicotinoids, people start with prevention and other non-chemical methods of pest control. Scout for insect pests and identify them before any insecticide use. Use prevention (sanitation, mulch), mechanical (hand removal) and cultural methods first. Cultural methods include timely watering and fertilization and promoting populations of beneficial insects. Apply insecticides only when necessary, to prevent insect pests from causing unacceptable levels of damage. Follow the product label, because everyone, including homeowners, is required to review it carefully. Include pollinator attractive plants that have not been treated with neonicotinoid or other insecticides in the landscape. A 2022 study in Environment international found substantially higher urinary levels in Asian populations. Levels in the United States and Europe were lower. A 2023 study by Haixin Tu reported 20 neonicotinoids and metabolites in human specimens. Urine, blood and hair dominate those specimens. The National Health and Nutrition Examination Survey of 2015 to 2016 quantified six urinary neonicotinoid biomarkers in 3,038 participants.
