Risk Factors for Organophosphate Pesticide (OP) Exposure among Indonesian and South Australian Migrant Farmworkers and the Impact of an Intervention to Reduce Exposure

Author: . Suratman

Suratman, ., 2016 Risk Factors for Organophosphate Pesticide (OP) Exposure among Indonesian and South Australian Migrant Farmworkers and the Impact of an Intervention to Reduce Exposure, Flinders University, School of the Environment

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Organophosphate compounds are the most widely used pesticides in the world. Organophosphate pesticides (OPs) contribute to mortality and morbidity in farmworkers through acute or chronic pesticide-related illnesses. While the factors that increase OP exposure and cause adverse health effects among farmworkers in developing and developed countries have been investigated in the past, there is a paucity of relevant research in Indonesia and Australia.

This study consisted of quasi and true experimental designs. A quasi-experimental design is defined as a design that is similar to an experimental design but lacks a key ingredient, random assignment. This research design is sometimes called as non-randomised pre-post intervention studies. This design involves selecting groups, upon which a variable is tested, without any random pre-selection processes. After this selection, the experiment proceeds in very similar way to any other experiment, with a variable being compared between different groups, or over a period of time. The quasi-experimental study investigated benefits arising from short educational intervention, either delivered using a group communication among Indonesian farmworkers or one-on-one approach among South Australian (SA) migrant farmworkers. Specifically, the study assessed knowledge of adverse effects of OPs and self-protection from OP exposure, perceptions about OP exposure, field practices in handling OPs to reduce OP exposure, and activity levels of plasma cholinesterase (PChE) as a biomarker of exposure to OPs and erythrocyte acetylcholinesterase (EAChE) as a biomarker of toxicity in whole blood samples. Data collection used an interviewer-administered questionnaire and collection of a fingerprick blood sample before and following the intervention. Fingerprick blood samples were assessed immediately using Test-mate ChE field kit instrument to measure EAChE and PChE activities. Meanwhile, the true experimental study examined whether the interaction between pralidoxime (pyridine-2-aldoxime methochloride) solution in saline leads to changes in PChE activities inhibited by OPs using fresh plasma samples in field measurements as a method to estimate percent inhibition of PChE activities due to OP exposure. Blood samples were centrifuged to separate plasma. Plasma samples were then divided into two portions. One 8µL portion was mixed with 2µL pralidoxime solution in saline and the other portion was mixed with 2µL saline solution. PChE of each sample was analysed using the same field kit.

This study was conducted at two research sites, at Dukuhlo Village in Brebes Regency, Indonesia and the suburb of Virginia, South Australia. In Indonesia, 30 of 52 Indonesian farmworkers working and living at the village were randomly selected. On the other hand, due to many difficulties in recruiting research participants in Australia, a snowball sampling method by asking research participants to nominate another farmworker with the same trait as our next participant was used to select seven SA migrant farmworkers resulting in a sample size of seven farmworkers. Nominate another farmworker with the same trait means proposing another farmwoker who has the same characteristics to be a research participant in accordance with inclusion criteria, namely male, had to be employed in farm work within the past 3 months. The ethnicity of the SA migrant farmworkers was Vietnamese. All those research participants were involved both study designs. In addition, twenty-four venous blood samples from random blood donations collected once from the Australian Red Cross Blood Service (ARCBS, Adelaide, SA) were added as a third sampling group in the true experimental study.

Results of the educational intervention showed statistically significant improvements in scores of knowledge, perceived susceptibility, perceived severity, perceived benefits, and perceived barriers, except for cues to action among Indonesian farmworkers after being adjusted for level of education and years working as a farmworker. In contrast, SA migrant farmworkers had statistically insignificant improvements in almost all measured variables, except for knowledge about adverse effects of OPs. Generally, the intervention did not significantly change field practices in both groups. However, some self-reported significant behavioural improvements in handling OPs occurred among Indonesian farmworkers, for example, not touching crops after OP application, not spraying OPs against wind direction, avoiding spray drift when applying OPs and ensuring to not affect other people by over applied spray drift when applying OPs. In addition, the proportion of farmworkers who were suffering from OP-related symptoms slightly decreased from 67% in pre intervention to 63% in post intervention. In general, the field practices of SA migrant farmworkers in post intervention remained constant compared with pre intervention. A group communication was more effective in improving knowledge, perceptions, and some aspects of field practices in handling OPs compared with the one on one intervention. Notwithstanding, the differences in EAChE and PChE activity levels between pre and post intervention could be related to the time elapsed since last exposure and not to the intervention performed. Furthermore, the results of the true experimental study demonstrated that PChE re-activation ranging from 36% to 39%. The estimation of percent inhibition of PChE activities in fresh plasma samples due to OP exposure among these three groups showed that the highest inhibition occurred among SA migrant farmworkers, approximately 33%, otherwise Indonesian farmworkers and ARCBS were similar, approximately 28%.

Among Indonesian farmworkers, factors of knowledge, perceived susceptibility of OP exposure, perceived severity of adverse health effects due to OP exposure, perceived benefits of personal protective equipment (PPE) use and field practices in handling OPs played an important role in increasing OP exposure. Meanwhile, perceived barriers to PPE use, following OPs safety procedures, and cues to action were identified as important factors in increasing OP exposure among SA migrant farmworkers. In addition, the use of group communication was more effective in improving farmworkers’ knowledge and perceptions compared with the individual approach. Notwithstanding, the effect of different periods between OP application and blood collection might also influence the differences of these results between both study groups. Provision of appropriate equipment and long-term educational intervention linked to workplace conditions was needed to improve their knowledge, perceptions, and work practices to reducing adverse effects due to OP exposure. Pralidoxime assay can be a useful exposure measurement tool to use under field conditions.

Keywords: Organophosphate pesticides exposure, Indonesian farmworkers, South Australian migrant farmworkers

Subject: Environmental Health thesis, Public Health thesis

Thesis type: Doctor of Philosophy
Completed: 2016
School: School of the Environment
Supervisor: Dr. Kirstin Ross