More studies on the human health effects of chronic neonic exposure are needed

Neonics have been found to affect mammalian nicotinic acetylcholine receptors nAChRs in a way that is similar to the effects of nicotine. These receptors are of critical importance to human brain function, especially during development and for memory, cognition, and behavior. A distinct aspect of neonic toxicity is the ability to bind to the most prominent subtype of nAChRs in mammals, the α4β2, which is found in the highest density in the thalamus. Alteration of the density of this neuroreceptor subtype has been found to play a role in several central nervous system disorders, including Alzheimer’s disease, Parkinson’s disease, schizophrenia, and depression. In the developing brain, this subtype is involved in neural proliferation, apoptosis, migration, differentiation, synapse formation, and neural circuit formation.
This is the first systematic review of the literature on human health effects of neonicotinoids to the authors’ knowledge. As reviewed here, four studies reported low rates of adverse health effects from acute neonic exposure. Even the most severe outcomes, including two fatalities, may have been mediated by other factors (age, underlying health conditions, undetected coexposures). The acute poisoning studies did, however, elucidate clinical findings important for the diagnosis and treatment of acute neonic exposures, including a better understanding of neonic toxicokinetics in humans. The other four studies reported associations between chronic neonic exposure and adverse developmental outcomes or a symptom cluster including neurological effects. The findings of animal studies support the biological plausibility for such associations. Although the studies in this review represent an important contribution to the literature, particularly given the lack of any general population chronic exposure studies prior to 2014, there remains a paucity of data on neonic exposure and human health. Given the widespread use of neonics in agriculture and household products and its increasing detection in U.S. food and water, more studies on the human health effects of chronic (non-acute) neonic exposure are needed.
Source:
Cimino, A., Boyles, A., Thayer, K., & Perry, M. J. (2016). Effects of Neonicotinoid Pesticide Exposure on Human Health: A Systematic Review.. Environmental Health Perspectives, (). http://dx.doi.org/10.1289/EHP515