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Research Abstract

Land, People and Environment

• Constanza: Poisoned Paradise

The Problem

• The Politics of Pesticides

• "Silent Spring" in Constanza

• Culture and Illness: The Pesticide Curse

The Research

• Literature Review

• Research Objectives

• Contribution to Research

• Research Methods/Design

Data Analysis

• Biogeophysical Data Analysis

• Health Survey

• Anthropological Data Analysis

• Buffer Analysis

• Conclusion

Geo-Cultural Visual Tour

• Research Photos

• Space, Place and Environmental Contamination

• Environment and Geography

• Patrimonio Nacional Cultural Dominicano

About Me and My Reserach Interests

• CV / Resume

• Abstracts

• Creating a Taino Identity

• Creando un Identidad Taina

• Favorite Links

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A Health Survey was conduct in the four valley region to collect data on self-reported and observed symptoms, pesticide exposure indicators (cholinesterase testing), and alternative exposure pathways in children and farm workers. This survey will assess environmental and health issues and will provide critical information for assessment, evaluation, and development of active health surveillance and policy in the Constanza region.

Observed and Self-Reported Symptoms: Indicators of Pesticide Exposure

The subjective nature of self-reporting symptoms was taken into consideration, along with other factors such as poor memory recall and respondents’ motives for participating. The latter is considered important since some of the health survey participants believed that participation would lead to monetary rewards. These participants would hype or overestimate their symptom severity in order to remain in the survey. Accordingly, the results obtained from the self-reported symptoms section of the health survey only give an indication of pesticide exposure.

Self-Reporting Symptoms Associated with Pesticide Exposure

Despite the uncertainties of findings in the body of epidemiological research, the literature reports putative links between self-reporting symptoms associated with pesticide exposure and increased development of chronic illness (liver, respiratory, brain diseases). Several studies have shown a link between self-reported pesticide exposure and liver disease  (Minton 1988; Jeyaratnam 1990; Abebe 1991; Dinham 1993; Garcia-Rodriguez 1996; Habib 1996; Guillette 1996; Kavlock 1996;  Daniels 1997; Bekkers 1997; Repetto and Baliga 1997;  Gupta 1998; Ecobichon 1999; Harris 2000; Lu 2000; Fenske 1999; Agate 2001; Bell 2001; Cabello 2001; Karalliedde 2001; Arcury 2001;  Faustman 2002).

Symptom Severity

Health survey participants composed of households were asked to list symptoms they were suffering from at the time the health questionnaire was administered. Participants were then asked to rate the severity level of their symptoms on a scale from 1 to 4 (1 = mild, 2 = moderate, 3 = severe, 4 = very severe symptom). Those participants that reported experiencing no symptoms were given a value of 0 (zero).

Participants were also asked to list recurrent symptoms and to rate them using the same severity scale. To gauge participants knowledge regarding the symptoms associated with pesticide exposure, they were asked to list the symptoms they believed are caused by pesticides. Their answers were entered into the health database. Only symptoms associated with pesticide exposure were recorded and entered  into the database (Karalliedde, Feldman, Henry, Marrs 2001; Ecobichon 1999; Kamrin 1997).

Table  1   Table Count Symptom Severity and Gender

Source:  Health Survey, 2002

Table 1 shows the number of men and women self-reporting symptom severity. The number of women self-reporting no symptom or mild symptom was significantly higher than male respondents. More men self reported moderate, severe and very severe symptoms. This was expected considering that more men work in the fields where they are in “closer” proximity to pesticides than women, who mainly stay at home. Nonetheless, the number of women self reporting symptom severity in the severe and very severe range was also significant, pointing to the possibility that women, notably those who live in low risk pesticide exposure communities, may be exposed via alternative pesticide exposure pathways. This is not surprising however, since there are multiple exposure pathways that can enter the home and expose occupants.

Table 2 shows cross tabulation between symptom severity and community. Although there are a large number of participants reporting severe and very severe symptoms (N=46), it is only an indicator of pesticide exposure. As expected, the lesser (biogeophysically) exposed communities of Colonia Kennedy and Tireo-El Café had the highest counts of severe and very severe symptom (N=35).

Table 2       Count: Symptom Severity in Communities

Source: Health Survey, 2002

I performed a correlations analysis on the data in Table 2 to examine the association between proximity and symptom severity. Table 3 shows that the correlation coefficient  (-.426) is significant (p<.001), indicating that symptom severity increases as distance to pesticide source decreases. Based on these results, the probability is less than .001 that we would be wrong in rejecting the null hypothesis that there is no linear relationship between symptom severity and proximity to pesticide source.

Results obtained from this section supports the hypothesis that severity of self-reported symptoms and illness increase with decrease distance from pesticide source. This Hypothesis is also supported by the works of Lu (2000) and Ward (2000).

Table 3            Correlations: Symptom Severity with Proximity to Pesticide Source

**  Correlation is significant at the .01 level (2-tailed).

To further examine the reasonableness of my data, I computed the means for symptom severity for specific distances. The means provides what we might expect a person’s symptom severity to be as determined by distance or proximity to a pesticide source. The chi-square results in Tables 4 and 5 confirm the significant relationship between symptom severity and proximity to pesticide source.

Table 4   Chi-Square Test: Symptom Severity and Proximity to Pesticide Source

2 cells (20.0%) have expected count less than 5. The minimum expected count is 3.47.

Table 5 Chi-square of Exposure Risk and Symptom Severity

Cholinesterase Testing

At the community clinics run by SESPAS, a lab tech (not a physician) does the interpretation of cholinesterase test results. The results of cholinesterase tests were provided by household members (one per household) during the course of the Health Survey. The normal value of cholinesterase depends on the technique, and should be determined by the laboratory performing the test. In the case of the Dominican Republic that responsibility falls on the National Center for the Control of Tropical Diseases (CENCET in Spanish). CENCET forms part of the SESPAS public health system, which has labs throughout the country. In the Dominican Republic, depleted cholinesterase levels are expressed as a percent of a pre-exposure “normal” baseline and are referenced as follows: 100-75% (Normal), 75-50% (Probable Exposure), 50-25% (Serious Exposure), 25-0% (Over Exposure). These percentages are based on the reference standard and range for cholinesterase serum test, established by SESPAS.

Although a 50 percent drop below the individual's baseline of red blood cell (RBC) cholinesterase or plasma cholinesterase means that the individual should be removed from all exposure to organophosphates and carbamates  (using EPA Guidelines 2001), 56.4% (N=25) of agricultural workers interviewed (N=45) reported returning to the field less than a week after experiencing severe exposure. However, the EPA recommends that exposed individuals should not be allowed to return until levels return to the pre-exposure baseline range (Bird 2002, EPA Official, Personal Communication). Removal from exposure means avoidance of areas where the materials are handled or mixed and avoidance of any contact with open containers or with equipment that is used for mixing, dusting or spraying.

Table 6   Cholinesterase Test Result Using SESPAS Reference Levels

Table 6 shows results from cholinesterase testing for the sample population (N=101) obtained from household participants and based on SESPAS cholinesterase reference levels. Cholinesterase values ranging from 0-50 percent indicate a very severe to severe exposure (N=42). A test value of 50-75 percent indicates probable exposure (N=29). A test value above 75 percent indicates normal exposure (N=30). However, these values are misleading since over half (N=17) of the probable exposure group (50-75%) had cholinesterase levels close to the severe reference range.

A major concern with the cholinesterase tests performed at SESPAS clinics is that results could be skewed to give the false impression that pesticides are safe, making the data unreliable. However, the likelihood of under-reporting is presumed to be far less than that of over-reporting. Land and agribusiness owners are the ones who would benefit from such skewed results. The financial burden of improving environmental and community health would be lessened, if the agribusiness sector could prove that pesticides are safe and community members are suffering other non-pesticide exposure related conditions.

Cholinesterase Tests Results: Biomarkers for Pesticide Exposure

Cholinesterase level results were used as medical biomarkers of   pesticide exposure. These results show that communities located in areas at lesser risk from pesticide exposure were experiencing some level of exposure, which the research attributed to work-to-home and school-to-home pathways.

In the study region, community members commonly reported fatigue and muscle weakness, depression, memory and cognitive problems, diarrhea, stomach cramps and sleep apnea. These symptoms are consistent with findings of other  studies conducted in Africa (Forget 1991; Maroni 1993; Mbakaya CFL, Ohayo-Mitoko GJA, Ngowi VAF, et al. 1994; London 1995; London, Ehrlich, Rafudien, Krige, Vurgarellis 1994) and Southern Asia (Kishi, Hirschhorn, Djajadisastra, et al. 1995; Wesseling, McConnell, Partanen, et al.  1997; Eddlestone, Rezvi Sheriff, Hawton 1998; Edwards 2001; Karalliedde, Laksman, Feldman, Henry, and Marrs, 2001), which indicate a possible role of reduced cholinesterase following pesticide exposure. However, in the study region, some of the self-reported symptoms could be attributed to different disease etiologies, such as gastrointestinal problems caused by contaminated drinking water.

Determining the Risk of Pesticide Exposure Based on Cholinesterase   Level and Biogeophysical Characteristics

Health survey results showed that the four communities were highly homogenous. Households shared similar socioeconomic conditions, diet, education level, dwelling structures, behavior and activities. Questionnaire results showed differences in self-reported symptom severity and odor perception among survey participants living in communities of greater and lesser pesticide exposure risk.  In summary, the four communities differed in terms of location, meteorological conditions, odor perception, self-reported symptoms and severity, and proximity to pesticide source.

Although participants in the four communities reported symptoms associated with pesticides, it was not clear if exposure had occurred. Serum cholinesterase test results were obtained from each household (one test result per household) and recorded to make a more definite determination that the self-reported symptoms were linked to pesticide exposure.

Criteria Used for Determining the Risk of Pesticide Exposure Based on Cholinesterase Level and Biogeophysical Characteristics

Table 7 shows health survey participants who  (1) lived in communities with biogeophysical characteristics indicating a higher risk of exposure, (2) had depressed levels of cholinesterase (N=28) and (3) self-reported symptoms associated with pesticide exposure. These exposure cases were attributed to alternative pesticide exposure pathways. Further investigation revealed that the alternative pesticide exposure group had at least one family member that had contact with pesticides at work or school.

Table 7         Cholinesterase Level and Symptom Severity for Each Community