Neurobehavioral effects of pesticides : a review of current knoweledge

Background and Aims: Several pesticides, mainly insecticides, exert neurotoxic effects. While acute effects are well known, documented and studied, uncertainty still persists on possible long term effects consequent to low dose exposure. In this field, behavior might be a specific target, and neurobehavioral effects are repeatedly reported in literature, but a link between prolonged exposure to pesticides and neurobehavioral outcomes has not been firmly established or denied yet. Methods: a literature search has been done using the keywords: “neurobehavioral”, “pesticides”, specific compounds or groups of compounds and related links for some selected papers. A total of about 110 papers have been selected, collected and evaluated. In the evaluation, it has been taken into account for each paper compound/s addressed, number of subjects studied, exposure assessment/estimation (in terms of occupational/non occupational and according to the duration), control of confounders, type of alteration observed, types of testing methods applied, information on the experimental design, when available. Results: neurobehavioral effects consequent to severe acute organophosphate non-fatal intoxications are documented in literature, but studies addressed to subjects occupationally and environmentally exposed to pesticides, in absence of any previous acute intoxication, have been carried out since the sixties, with no univocal results, even though some evidence is available of effects in the most exposed population subgroups such as, for example, sheep dippers. An association between exposure to phenoxy herbicides and cognitive or neuropsychiatric dysfunction has been suggested in past years, but such an association has not been confirmed by more recent studies, and neurobehavioral changes have been observed in DDT exposed workers engaged in malaria control activities and in workers engaged in the application of fumigants, such as methyl bromide. The main limits of existing studies are represented by the different in the approach carried out by different groups, difficulties in the selection of the study population and control of confounding factors, namely difference in the education status, lack of knowledge on exposure levels and difficulties in obtaining sound exposure estimates, and limited knowledge on the mechanism of action of the observed effects. Discussion and Conclusions Even though no conclusion can be drawn, concern on neurobehavioral toxicity of pesticide is still high, mainly for the possible consequences on vulnerable subgroups, such ad children and pregnant women. Therefore, these groups, based on the precaution principle, have to considered specific targets for preventive measures. Further research is needed on the topic, and a specific effort for the standardization of the tests to be performed is necessary.