Pesticide exposed workers who were regularly involved in mosquito control, had higher , diastolic blood pressure , and heart rate than non-exposed workers. . In a representative sample of U.S. adults, urinary organophosphate metabolite concentrations were positively associated with higher diastolic, but not systolic, blood pressure . Additionally, a large cross-sectional study of pregnant women in Italy noted increased odds of gestational hypertension among women who reported agricultural or domestic pesticide exposures compared to unexposed pregnant women . Positive associations with SBP and DBP were also observed in an experimental study of rats who were exposed to the organophosphate chlorpyrifos . Few studies have assessed the health effects of children in relation to a pesticide spray season. In our previous work among Ecuadorian children as part the Secondary Exposure to Pesticides among Children and Adolescents , we previously observed that children examined sooner after the Mother’s Day harvest had lower neurobehavioral performance and lower AChE activity compared to children examined later, particularly among children who lived in close proximity to flower plantations .The purpose of this study was to investigate whether blood pressure differed among individuals examined at different points in time after the end of the Mother’s Day flower harvest, which marks the end of a period of heightened pesticide use. The ESPINA study aimed at evaluating the effects of low-dose environmental pesticide exposure on child development.
We examined 313 children of 4-9 years of age living in Pedro Moncayo County, Ecuador,large pot with drainage a county with one of the highest concentrations of flower plantations per capita worldwide. The industry employs approximately 21% of adults in the county over an approximate production area of 1,800 hectares . To our knowledge, study participants did not work in agriculture or otherwise. Most participants of the ESPINA study were enrolled through the 2004 Survey of Access and Demand of Health Services in Pedro Moncayo County, collected by Fundacion Cimas del Ecuador in association with the communities of Pedro Moncayo County. That representative survey obtained information on 71% of the population living in Pedro Moncayo County, Ecuador and measured the height and weight of 33% of children younger than 5 years of age. The remaining 27% of participants were new volunteers also living in Pedro Moncayo County, and were recruited through community announcements performed by community leaders, governing councils, and by word of mouth. The ESPINA study aimed to have a balanced distribution of participants living with floricultural and non-agricultural workers . The study had the following inclusion criteria: participants who lived with a flower plantation worker had to live with the worker for at least one year. For children not living with agricultural workers, participants must have never cohabited with an agricultural worker, never inhabited a house where agricultural pesticides were stored and have had no history of direct contact with pesticides. The ESPINA study included participants residing in all five parishes of Pedro Moncayo County, and had similar socio-economic and racial distributions as the general population of the county. Detailed participant recruitment information has been described previously . Informed consent, parental authorization of child participation, and child assent of participants 7 years of age and older was provided for all study participants. This study was approved by the Institutional Review Boards of the University of Minnesota, the University of California San Diego, Universidad San Francisco de Quito, and the Ministry of Public Health of Ecuador.
Children were examined between July 10 and August 15, 2008, during the period of lowest flower production of the year, and within 100 days after the estimated end of the peak-flower production period associated with the Mother’s Day flower production and harvest . During this 37-day period, examinations took place on 20weekdays days, averaging 15 participants per day. Exams were conducted in 7 schools distributed across the 5 parishes that make-up Pedro Moncayo County during the summer months, when schools were not in session. Assessments were conducted at seven schools across the five parishes that makeup Pedro Moncayo County during the summer break, when schools were not in session. In-person interviews of parents and other adults cohabiting with the child were used to obtain information on socioeconomic status, demographics, health, and direct and indirect pesticide exposures of household members. Children’s height was measured using a height board, following standard methods , and weight was measured using a digital scale . Body mass index -for-age z-scores were calculated using World Health Organization growth standards . Resting heart rate was measured by a 30-second auscultation, prior to blood pressure measurement. Systolic blood pressure and diastolic blood pressure were measured with a pediatric Omron aneroid sphygmomanometer , appropriate for the arm size of the children, following protocols recommended by the American Heart Association . Namely, measurements were taken after 3-5 minutes of rest. Children were in a seated position with the antecubital fossa supported at heart level, with uncrossed legs and both feet on the floor. Blood pressure was measured twice, and the averages of the two SBP and DBP values were used in the analyses. Blood pressure percentiles appropriate for age, gender and height were calculated using a normative sample of US children and adolescents , using a publicly available program . This normative sample was based on the sample of the Fourth Report on the Diagnosis, Evaluation, and Treatment of High Blood Pressure in Children and Adolescents , but excluded overweight and obese adolescents.
Blood pressure status categories were determined based on the American Academy of Pediatrics cut-offs . It is worth noting that the prevalences of blood pressure status categories presented in this paper are based on a cross-sectional assessment and do not necessarily reflect a clinical diagnosis. It is recommended that multiple blood pressure measurements over time be obtained prior to establishing a diagnosis of hypertension . Erythrocytic AChE activity and hemoglobin concentration were measured from a single finger stick sample using the EQM Test-mate ChE Cholinesterase Test System 400, AChE Erythrocyte Cholinesterase Assay Kit 470 . Distance from the participants’ homes to the nearest flower plantation was measured using portable global positioning system receivers. We used geographical coordinates of Pedro Moncayo County homes that were collected in 2004, 2006 and 2010 by Fundación Cimas del Ecuador as part of the System of Local and Community Information . Flower plantation edges were measured and noted by geographical coordinates for each corner of the plantation’s perimeter. The distance from each participant’s home was calculated to the nearest 1-meter segment of the flower plantation perimeter using ArcGIS 9.3 . To include most children in multi-variable analyses, we imputed missing information for race and residential distance to the nearest flower plantation. Residential distance to the nearest flower plantation was imputed for three participants from a random selection of values generated from a random normal distribution based on the concurrent ESPINA mean ± standard deviation values. For race, we created a “missing” race category to account for 14 children with missing information. Because only five children in this study were white and two were black, we incorporated these seven children in the mestizo category to improve model stability when adjusting for race. The present analyses include the information of 310 children who had information for all variables of interest.We calculated the means and standard deviation or proportion of participant characteristics, as appropriate,drainage collection pot for all participants and stratified across tertiles of time after the Mother’s Day flower harvest in which the examination took place. Time after the Mother’s Day harvest was calculated as the number of days between the approximate end of the Mother’s Day flower harvest and the date and time of the beginning of the examination. We calculated the p-value for trend for participant characteristics across levels of examination time after the harvest activity using linear regression and modeling time after the harvest as a continuous variable. The associations of time after the Mother’s Day harvest with blood pressure were analyzed using three multiple linear regression models defined a-priori. Model 1 adjusted for a small number of potential confounders including age, gender, race and heart rate.
Model 2 further adjusted for height and BMI-for-age z-score, considering the positive associations of these with blood pressure among children . Considering that blood pressure percentiles appropriate for age, gender and height were calculated, the adjustment models for these outcomes do not include age, gender or height. A third adjustment model was conceived as a mediation model, which further adjusted model 2 for two constructs of pesticide exposure including residential distance to the nearest flower plantation , and AChE activity . Mediation by cohabitation with floricultural workers was considered but later removed as we had previously observed that children living with flower plantation workers had lower BP and after including it in the model the estimates were unchanged. As a standard practice, all models were adjusted for hemoglobin concentration because variations in hematocrit can alter the values of erythrocytic AChE activity . We then plotted the model 2- adjusted least-squared means and 95% CI of blood pressure percentiles and blood pressure for each sextile of time after the harvest . Additionally, we tested for curvilinear associations by modeling time after the harvest as a quadratic variable . Using logistic regression, we calculated odds ratios and 95% confidence intervals for prehypertension or hypertension combined for tertiles 1-3 of time after the harvest compared to tertile 4. We combined prehypertension and hypertension given the low prevalence of hypertension in this cohort . The same adjustment models were used in these analyses. We assessed effect modification by age, sex and BMI-for-age z-score sex and by home distance to the nearest flower plantation. The latter was observed to be an effect modifier in the association between time after the Mother’s Day harvest and AChE activity . We tested statistical significance of interaction terms within models 1 and 2. We then analyzed the associations stratified by categories of the significant effect modifiers. Participant Characteristics—Child participants had a mean age of 6.6 years ; 51% were male, 73% mestizo, 21% indigenous, and 49% lived concurrently with at least one floricultural worker. The mean percentiles for SBP and DBP were 51.7 and 33.3 , respectively. Children were examined between 63 and 100 days after Mother’s Day harvest . Children examined earlier in the examination period were younger, shorter and more like to live with a floricultural worker compared to children examined later . Hemoglobin concentration and AChE activity were both positively associated with examination date. The prevalences of elevated blood pressure and hypertension stage 1 were 1.6% and 7.7% , respectively. No participants were classified as having hypertension stage 2. Participant characteristics are listed in Table 1. Time after the harvest was negatively and statistically significantly associated with measures of SBP and DBP in all 3 models. In model 2, the differences of SBP and DBP percentiles per 10.9 days after the harvest were: −4.3 and β:−7.5 . Corresponding negative associations with SBP and DBP were also observed . There was evidence of curvature on the association between time after the harvest and DBP and DBP percentile in all models as observed with the statistically significant quadratic β coefficients. Figure 1 depicts the associations of time after the harvest with SBP and DBP for model 2, and Figure 2 depicts the associations with SBP and DBP percentiles. The associations in the mediation model, which accounted for 2 pesticide exposure constructs , were minimally stronger for SBP measures but unchanged for DBP measures. There was no evidence of effect modification by age, gender, BMI-for-age z-score, residential distance to the nearest flower crop. In multivariate models of the combined outcome of elevated blood pressure, or hypertension stage 1 or stage 2 , we observed that for every SD decrease in time after the harvest there were significantly increased ORs in all 3 models . The associations were strongest for model 2, and weakest in mediation Model 3 as hypothesized . When time after the harvest was analyzed as tertiles, substantial ORs were observed when comparing children examined between 63-81 days after the harvest with children examined between 91 and 100 days . As expected, weaker associations were observed in participants examined in tertile 2 vs tertile 3 .