Assessing biomarkers and neuropsychological outcomes in rural populations exposed to organophosphate pesticides in Chile – study design and protocol

Abstract

BackgroundHealth effects of pesticides are easily diagnosed when acute poisonings occurs, nevertheless, consequences from chronic exposure can only be observed when neuropsychiatric, neurodegenerative or oncologic pathologies appear. Therefore, early monitoring of this type of exposure is especially relevant to avoid the consequences of pathologies previously described; especially concerning workers exposed to pesticides on the job. For acute organophosphate pesticides (OPP) exposure, two biomarkers have been validated: plasma cholinesterase (ChE) and acetylcholinesterase (AChE) from erythrocytes. These enzymes become inhibited when people are exposed to high doses of organophosphate pesticides, along with clear signs and symptoms of acute poisoning; therefore, they do not serve to identify risk from chronic exposure. This study aims to assess a novel biomarker that could reflect neuropsychological deterioration associated with long-term exposure to organophosphate pesticides via the enzyme acylpeptide-hydrolase (ACPH), which has been recently identified as a direct target of action for some organophosphate compounds.Methods/DesignThree population groups were recruited during three years (2011–2013): Group I having no exposure to pesticides, which included people living in Chilean coastal areas far from farms (external control); Group II included those individuals living within the rural and farming area (internal control) but not occupationally exposed to pesticides; and Group III living in rural areas, employed in agricultural labour and having had direct contact with pesticides for more than five years. Blood samples to assess biomarkers were taken and neuropsychological evaluations carried out seasonally; in three time frames for the occupationally exposed group (before, during and after fumigation period); in two time frames for internal control group (before and during fumigation), and only once for the external controls. Neuropsychological evaluations considered cognitive functions, affectivity and psychomotor activity. The biomarkers measured included ChE, AChE and ACPH. Statistical analysis and mathematical modelling used both laboratory results and neuropsychological testing outcomes in order to assess whether ACPH would be acceptable as biomarker for chronic exposure to OPP.DiscussionThis study protocol has been implemented successfully during the time frames mentioned above for seasons 2011, 2012 and 2013–2014.

Fatores associados aos óbitos entre homens envenenados por carbamato (“chumbinho”)

“…A study conducted in Chile (9) reports that human exposure to organophosphorus pesticides has been extensively documented, showing it is a health problem that is especially associated with rural workers in developing countries. Another study conducted in Kuwait reports that poisoning-caused suicide was the third most common modality of death and is an important problem in the developing world due to ample availability and easy access to substances by people susceptible to committing suicide (10) .…”

“…From this perspective, the signs and symptoms recurrent among adult male victims of acute carbamate poisoning and who composed the case group in this study, as identified on the reporting forms were: myosis, drooling, muscle twitching, sweating, vomiting, and bronchorrhea. It is worth noting that the literature describes acute poisoning as being relatively easy to diagnose because it is accompanied by cholinergic signs and symptoms (9) .…”

Limitations and Biases in Cohort Studies

“…It could also be useful. For example, in the mentioned study about pesticide exposure in agricultural workers and cognitive impairment, gender turned out to be a confounder [7]. This resulted from the type of work performed differing between men and women.…”

“…Selection criteria must be clearly defined from the beginning of the study in a way that ensures that biases are avoided. For example, a research was conducted with the objective of assessing the association between exposure to pesticides and neurocognitive impairment, including fine Limitations and Biases in Cohort Studies http://dx.doi.org/10.5772/intechopen.74324 motor coordination [7]. The researchers used Purdue Pegboard and MOART reaction time tests to measure the outcome.…”

Biomonitoring of blood cholinesterases and acylpeptide hydrolase activities in rural inhabitants exposed to pesticides in the Coquimbo Region of Chile

“…To that end, sampling was performed before and during the spraying season. The detailed description of the study protocol can be obtained in a recent study from our group [ 16 ].…”