Neonicotinoid Pesticides

Neonicotinoids (also referred to as “neonics”) are insecticides derived from nicotine. They act by binding strongly to nicotinic acetylcholine receptors in the central nervous system of insects, causing overstimulation of their nerve cells, paralysis and death. Neonicotinoids are highly water soluble, persistent in the environment, and can migrate into all parts of treated plants.

Although their principal use is in agriculture for seed and soil treatment and on plant foliage, neonics may be used in home yards and gardens, golf courses, and for flea and tick treatments on dogs and cats. Introduced in Canada in the 1990s, five neonicotinoids are approved for agricultural use in Canada. Of these, acetamiprid and thiacloprid are permitted for limited purposes. In April 2019, the Pest Management Regulatory Agency (PMRA) of Canada released its re-evaluation of the three most widely used neonicotinoid substances: imidacloprid, clothianidin, thiamethoxam.

New regulations aimed at reducing the chance of pollinators coming into contact with plants and flowers contaminated by the three compounds will be phased in by the spring of 2021. Some regulatory changes include:

• Most foliar applications prior to bloom will be disallowed;
• Use on stone fruit, strawberries and some tree nuts will be discontinued;
• New restrictions related to a number of other crops and soils have been introduced;
• Additional precautions will now be required during the planting of neonicotinoid-treated seeds to avoid exposing pollinators to contaminated dust.

Further decisions aimed at protecting aquatic life are expected in early 2020 (Health Canada, 2017).

Public awareness of the hazards of neonicotinoids is from publicized concerns about deaths and colony collapse disorder among bees and other pollinator insects. As the overview below shows, there is evidence of environmental and dietary exposures to neonicotinoids and their metabolites among people, but also uncertainty regarding human health risks.

Tracing the environmental fate shows that neonicotinoids are found in environments and foods and on household pets:

• Neonicotinoid residues have been detected in wetlands, surface water and agricultural soil in several Canadian studies (e.g., Schaafsma et al., 2015,  Main et al., 2014).
• Neonicotinoid residues are present in most edible parts of fruits and vegetables and cannot be washed off. Imidacloprid may have the highest detection rate (Chen et al., 2014).
• Neonicotinoid residues from flea treatments on pets may be transferred for up to four weeks after application, potentially exposing people in contact with treated animals (Craig et al., 2005).

There is evidence that the general population is exposed to neonicotinoid pesticides through their diets. While average intakes of individual compounds associated with food consumption appear to be within safe levels, it is possible that certain segments of the population may have exposures above recommended levels:

• Exposure estimates for the US population indicated that the although average dietary intake could be considered safe, potential for exposure above the chronic reference dose existed for people consuming large amounts of more heavily contaminated food items (e.g., squash and spinach) (Chang et al. 2018).
• According to Health Canada, environmental amounts of neonicotinoids found in the environment are below levels of concern for human health (Health Canada, 2016). People handling neonicotinoid pesticides may have higher exposure risks than the general population but can minimize their risk by following safety precautions specified in the product labels (e.g., use of protective clothing and equipment) (Health Canada 2018).
• A Japanese study found widespread exposures to neonicotinoid residues but intake levels of individual compounds were considered safe (Harada et al., 2016).

There are several human observational and animal studies indicating that there may be adverse developmental and neurological impacts from chronic exposure to neonicotinoid pesticides.

• A systematic review of four general population studies suggested a link between chronic neonicotinoid exposure (all ages, including pre-natal) and adverse developmental or neurological outcomes (Cimino et al., 2017).
• The European Food Safety Authority concluded that idiacloprid and ametamiprid may affect neuronal development and function, but further scientific study is warranted (European Food Safety Authority, 2014).

This topic page is intended to provide updated resources on the human health risks associated with neonicotinoid exposure, safer alternatives and knowledge gaps. In light of recent changes to regulations for this group of pesticides, the list also includes several evidence-informed documents prepared by regulatory authorities detailing new restrictions and guidelines and the rationale behind them. These documents also incorporate updated scientific evidence.

Selected External References

• Neonicotinoids (European Commission, 2019)
  This document provides facts on neonicotinoids and information about actions taken by the European Commission to protect honeybees, including restrictions of 3 neonicotinoids commonly used in plant protection products and treated seeds. The report confirms that most neonicotinoids are more toxic to insects and other invertebrates than to humans and higher organisms; however, one compound, thiacloprid has endocrine disrupting properties and may not be re-approved in 2020.
   
• Neonicotinoids: risks to bees confirmed (European Food Safety Authority, 2018)
  This document summarizes risk assessments and guidelines related to individual nicotinoids and the risks posed to pollinators. Links to the peer review of assessments are provided.
   
• Update on the neonicotinoid pesticides (Health Canada, 2017)
  This document offers some background on use of neonicotinoids and concerns related to their effects on pollinators. A human health risk assessment for imidacloprid concluded that human health risks were within acceptable limits.
   
• Case study: Neonicotinoids (Public Health Ontario, 2015)
  This case study describes the risks to bees from neonicotinoids, and provides information on regulation, ecosystem considerations and on food security, with consideration of residual concentrations of neonicotinoids in fruits and vegetables.

Peer-reviewed Publications

• Alternatives to neonicotinoids (Jactel et al. 2019)
  This article summarizes the uses, environmental and health risks of five neonicotinoid pesticides and assesses alternatives for pest management within the context of recent European regulatory restrictions. Each alternative is examined with reference to efficacy in controlling target pests and adverse effects on non-target species and the environment. The investigators found that in 96% of cases replacements can be found and in 78% of cases at least one chemical alternative exists.
   
• Trends in neonicotinoid pesticide residues in food and water in the United States, 1999–2015 (Craddock 2019)
  This article utilizes data from the US Department of Agriculture’s Pesticide Data Program to examine trends in residue concentrations in commonly consumed produce in the U.S. Although low levels are found, use of certain compounds is rising. Increased surveillance, biomonitoring studies and a focus on high risk groups is recommended.
   
• Potential human exposures to neonicotinoid insecticides: A review (Zhang et al, 2018)
  This review of articles on human exposure and biomonitoring published prior to 2017 indicated there is risk of neonicotinoids exposure, given that they are ubiquitous and have long half-lives.
   
• Neonicotinoid residues in fruits and vegetables: An integrated dietary exposure assessment approach  (Lu et al., 2018)
  This cross-sectional study analyzed residues of seven neonicotinoids in fruit and vegetable samples collected from U.S. and Chinese studies. Imidacloprid and thiamethoxam were detected in over one half of the samples. The authors concluded that neonicotinoids have become part of the dietary staple, with possible health implications for individuals.
   
• Catching up with popular pesticides: More human health studies are needed on neonicotinoids (Seltenrich, 2017)
  This science selection article emphasizes the widespread use of neonicotinoids and the concern that these insecticides can have adverse effects on mammals at sublethal doses, which suggests there is the potential for human health effects.
   
• Human exposure to neonicotinoid insecticides and the evaluation of their potential toxicity: An overview (Han et al., 2017)
  This narrative review refers to studies on human neonicotinoid exposure levels and health effects, and provides an evaluation of the potential toxicity of neonicotinoids on humans.

This list is not intended to be exhaustive. Omission of a resource does not preclude it from having value.