Predictors of exposure to organophosphate pesticides in schoolchildren in the Province of Talca, Chile
Highlights
► Chilean children had higher levels of OP metabolites than most published studies. ► Exposure during both summer and fall regardless of regional peaks in agriculture. ► OP residues in fruits were the major predictor of urinary DAP metabolites. ► First data on OP metabolites and dietary exposure in children of Latin America.
Introduction
Organophosphates (OP) are a group of synthetic pesticides used to control various insects on crops and in homes (Levine, 2007, Tadeo et al., 2008), and are widely used in agriculture. These pesticides are highly toxic cholinesterase-inhibiting compounds, but tend to degrade in the environment with exposure to sunlight and water. The lack of knowledge about how OPs should be applied and poor monitoring of their use have been associated with various human health problems, and environmental pollution by OP residues has accumulated over time (CDC (Centers for Disease Control, Prevention), 2009, Levine, 2007, MINSAL (Ministerio de Salud de Chile), 2007, WHO (World Health Organization), 2005).
There is ample evidence of adverse health outcomes associated with OP pesticide exposure in children and adults (Alavanja et al., 2004, Jurewicz and Hanke, 2006, Jurewicz and Hanke, 2008, Rosas and Eskenazi, 2008). Studies have linked OP pesticide exposure with adverse physiologic effects, increased frequency of cancer, neurobehavioral and cognitive abnormalities, teratogenicity, endocrine modulation and immunotoxicity (Alavanja et al., 2004, Bouchard et al., 2010, Bouchard et al., 2011, Engel et al., 2011, Handal et al., 2007, Jurewicz and Hanke, 2006, Jurewicz and Hanke, 2008, Marks et al., 2010, Rauth et al., 2006, Rosas and Eskenazi, 2008).
Human exposure to OP insecticides is widespread. Occupational use of OP insecticides, primarily in agriculture, represents the largest class of exposure. However, many populations, including children, have been shown to be widely exposed to OP insecticides from their diet, residential use, by living close to farms and from paraoccupational exposures via parents who work in agriculture (Barr et al., 2004, Bradman et al., 2005, Coronado et al., 2006, Kissel et al., 2005, Koch et al., 2002, Lu et al., 2004, Lu et al., 2008, Naeher et al., 2010, Valcke et al., 2006, Vida and Moretto, 2007).
In exposed populations, OP insecticides tend not to persist for extensive periods of time, with half-lives not exceeding one week in the human body (CDC (Centers for Disease Control, Prevention), 2009, MINSAL (Ministerio de Salud de Chile), 2007). Therefore, short-term OP pesticide exposure has often been assessed by measuring urinary metabolites of OP pesticides (Egeghy et al., 2011). Most biomonitoring studies have focused on measuring six dialkylphosphate (DAP) metabolites that are common to most OP insecticides currently in use (Wessels et al., 2003). Other more selective metabolites for assessing exposure to specific OP insecticides have also been used; however, they provide information for only a limited number of OP pesticides (Wessels et al., 2003). Although there are limitations associated with measuring these six non-specific metabolites (e.g., exposure to preformed metabolites and exposure to multiple OPs giving rise to the DAP), they have been useful tools in estimating exposure to OP insecticides as a class.
To date, almost no research has been conducted in South America investigating pesticide exposure and potential predictors of these exposures. Chile, a country located on the western coastline of South America, is a large producer of agricultural crops. The region that has the highest percentage of rural population engaged in agriculture and livestock husbandry is the Maule Region, with 34% of people living in rural areas (INE, 2002). The Maule Region, is located 254 km south of capital Santiago in central Chile, and is divided into 4 Provinces: Talca, Linares, Curico and Cauquenes. The Province of Talca, has 10 counties. 4 counties were included in this research: San Clemente, Talca, Maule and Empedrado (see Fig. 1). According to 2008 sales data, Maule used over 5 million kg of pesticides, making it the third highest pesticide-consuming region in Chile, representing about 10% of all national sales (SAG, 2008). OP pesticides comprise 30% of all insecticide, acaricide and rodenticide use in Maule, surpassing the national rate (25.5%). The widespread use of OP insecticides in agriculture, their largely unrestricted sale, and insufficient knowledge of their proper application and risks have resulted in acute intoxications in Chile (Concha, 2010, MINSAL (Ministerio de Salud de Chile), 2007, MINSAL, 2010a), primarily in the occupational setting.
We have conducted a pesticide exposure assessment study involving children in urban and rural Regions in Talca Province, Chile. We used biological and environmental monitoring coupled with questionnaire data, as has been done in other studies (Melnyk et al., 2012), to help us ascertain the predominant pathways of exposures to children in these areas. To date, no data exist on OP pesticide exposures in Chile and only a few exist in Latin America, but none that have examined several potential pathways for exposure in the general population.
Section snippets
Materials and methods
We collected longitudinal data during two seasons (summer and fall) from children living in four counties (Empedrado, Talca, Maule, and San Clemente) in Talca Province, in south central Chile. These counties were selected to represent a range of geographic locations and demographic conditions. Within these counties, 14 public elementary schools with enrollment ≥ 60 students were selected through a stratified random sampling methodology assuring both rural and urban schools were represented in
Results
Reliability testing to ensure precise urinary DAP measurement demonstrated good agreement among duplicate samples. Among the 20 duplicate pairs tested, a high correlation was found between duplicates of DEP metabolites (r = 0.99, p < 0.0001), DETP (r = 0.97, p < 0.0001), DMP (r = 0.86, p < 0.0001). DMDTP and DEDTP were consistently below the LOD so they could not be evaluated.
Of the 214 children initially enrolled in the study, the mean age was 8.6 ± 1.7 years with almost equal numbers of males (N = 109) and
Discussion
We sought to evaluate pesticide exposure in schoolchildren living in Talca Province, Chile and to understand the factors predictive of these exposures. We collected samples in May and December to understand seasonal variation in pesticide exposure.
We found that, of the variables evaluated, dietary exposure was the predominant contributor to OP metabolites in urine during both high and low agricultural seasons. Because no pesticide residues were detected in drinking water or soil, these were not
Funding
This work was supported by NIH Fogarty grant D43 TW 05746-02, USA, and through the National Commission for Scientific and Technological Investigation (CONICYT) of the Chilean government through a FONIS grant SA10I20001.
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2021, Environmental PollutionCitation Excerpt :The reason for the statistically non-significant result in the current study, which is in contrast to previous studies could be due to a lower sample size and also lower prevalence of households with farm applicators in the current study (10%) compared to previous studies (25%–45%) (Muñoz-Quezada et al., 2019; Rohitrattana et al., 2014). The finding that the sum of the three DAPs tended to be higher for children living on farms compared to those that did not, is consistent with previous studies in South Africa, Thailand, Chile and USA (Bradman et al., 2011; Coronado et al., 2011, English et al., 2012, Hyland and Laribi 2017; Muñoz-Quezada et al., 2012, 2019; Rohitrattana et al., 2014). This association was however statistically significant in previous studies and not in this study despite the high proportion of those living on farms (69%) in the study sample.