In addition to their agricultural use in crop protection, pesticides are important public health tools that are used to prevent vector-borne disease and to increase food supplies. However, recent research has shown that pesticides may also have negative impacts on public health. Studies have demonstrated acutely toxic effects at high doses, as well as chronic effects at low levels of exposure [1
]. Organophosphate (OP), carbamate, pyrethroid, and organochlorine insecticides have been shown to cross the human placenta, exposing developing fetuses [2
]. Prenatal exposure to pesticides is of particular concern due to the demonstrated neurodevelopmental toxicity of certain classes of pesticides (reviewed in [5
]). Due to the potential health effects of pesticide exposure, most countries have developed regulations to encourage safe use and control production, import, and export of pesticides. Nonetheless, regulation and enforcement is weaker in some countries than others [6
]. For example, some pesticides that are banned in certain countries due to their demonstrated health or ecological effects are still used elsewhere [7
]. In addition, safe practices, such as the use of personal protective equipment and following recommendations on pesticide container labels, are weak or absent in some places [9
The use of chemical pesticides in Thailand dates back to World War II, when DDT was imported to control the spread of malaria [10
]. Since then, their use has expanded to agricultural, industrial, and residential pest control. Most pesticides used in Thailand are imported rather than produced in-country, likely due to the difficulty in obtaining a permit for production from the government [10
]. The most recently published statistics showed that over 50,000 tons of active ingredients of pesticides (including insecticides, fungicides, herbicides, and other classes) were imported into Thailand in 2003 [10
]. In the same year, 54% of agricultural holdings reported using pesticides, with 73% of holdings in the northern region of the country reporting use [11
Evidence exists of pesticide-related health effects in Thailand. In 2007, 1,452 pesticide poisoning incidents were reported to the Ministry of Public Health, equivalent to 2.3 per 100,000 population [12
]. The true number is likely higher, as reported incidents include only those individuals with symptoms severe enough to require medical attention and/or with access to healthcare [12
]. In addition, underdiagnosis and underreporting of acute pesticide poisoning are well-recognized issues in developing countries and may also contribute to higher than recorded pesticide poisoning incidents [9
]. About 28% of farmers tested by the Ministry of Public Health in 2006 had unsafe levels of cholinesterase depression, a marker of OP and carbamate pesticide exposure [12
In Thailand, 38% of the national workforce was employed in agriculture in 2010 [15
]. Although agricultural workers, particularly those involved in pesticide application, are generally considered most at risk of health effects associated with pesticide exposure, the general population can also be exposed through environmental media (e.g., house dust, soil) and consumption of foods with pesticide residues. One study found detectable levels of six different pesticides (dicofol, dieldrin/aldrin, endosulfan, heptachlor/heptachlor epoxide, BHC, and DDT) in domestic water wells in central Thailand [16
]. Notably, four of these were banned over 15 years before the study was conducted.
Unsafe practices can lead to measureable health effects in workers exposed to pesticides [17
]. Interview surveys of agricultural workers in Thailand linked unsafe pesticide practices such as failing to use personal protective equipment (PPE) and using a higher than recommended concentration of pesticide to decreased serum cholinesterase activity, a marker of OP and carbamate pesticide exposure [12
]. Further, focus groups and surveys have shown that Thai farmers’ pesticide practices do not always reflect their individual risk beliefs [12
]. In one study, farm workers who believed they were less susceptible to the health effects resulting from pesticide exposure were more likely to have abnormal serum cholinesterase levels than those who believed they were more susceptible [12
]. To address unsafe practices and beliefs, researchers recommend educational interventions, which have been shown in several studies to increase knowledge, alter attitudes, and improve pesticide practices in Thailand [21
Researchers in Thailand have found higher levels of organochlorine pesticides and their metabolites in umbilical cord blood than those reported in similar studies from Canada, Australia, and elsewhere [23
]. In addition, Panuwet et al
] reported higher detection frequencies and median concentrations of OP pesticide metabolites in spot urine samples from children aged 12–13 (n = 207) in Chiang Mai Province, Thailand, than those reported for children aged 11–19 in the United States.
An estimated 200,000 children born in Thailand each year are at risk of prenatal exposure to pesticides resulting from their mothers’ agricultural occupation [27
]. This number does not take into account other pathways of maternal pesticide exposure, including exposure through home use, diet, and other environmental media, and is thus likely an underestimate. Limited information is available on pesticide knowledge, attitudes, and practices of pregnant agricultural workers and other pregnant women in Thailand and elsewhere [29
]. Obtaining this information is essential to understand the factors influencing prenatal pesticide exposures in order to develop interventions that prevent or reduce these exposures. Pesticide exposure is complex and results from a combination of interdependent factors including biological, social, environmental, economic, and political determinants. Knowledge, attitudes, and practices (KAP) surveys help identify knowledge gaps, behavioral patterns, and commonly-held beliefs in order to increase understanding of issues and elucidate targets and themes for interventions that may address any combination of these determinants [30
]. KAP surveys focusing on pesticide use have been conducted in several countries including Brazil, Ghana, South Africa, Egypt, and Thailand [21
]. However, no studies published to date have focused specifically on pregnant women.
We conducted a pilot KAP survey of 76 pregnant women in an agricultural community in Thailand in 2011. Our main objective in conducting the KAP survey was to collect data needed to inform the design of interventions to decrease pesticide exposure in this population. While we plan to conduct an individual-level educational intervention and will focus our analyses and discussion at this level of the ecological model, the information collected through this pilot study could be used to inform interventions at the interpersonal, community, and societal level as well. We hypothesized that pesticide practices would be significantly associated with pesticide knowledge, controlling for demographic characteristics and other relevant covariates. We also hypothesized that pesticide practices would differ by pregnancy trimester, with women in later trimesters using fewer pesticides and adopting behaviors to minimize exposures.
4.1. Pesticide Knowledge, Attitudes, and Practices in the Study Population
In general, study participants demonstrated relatively high levels of knowledge about pesticides, with most answering over 80% of the knowledge questions correctly. Knowledge was higher among our participants than reported in previous studies of agricultural workers in Thailand [12
] and other locations such as Bangladesh, Brazil, and Palestine [31
]. This may be due to our inclusion of non-agricultural workers, who had higher levels of education and higher knowledge scores than agricultural workers.
Consistent with previous findings [19
], attitudes on personal susceptibility to the health effects of pesticides were not associated with pesticide practices among the women in our study (Fisher’s p
> 0.20). In our small cohort, beliefs in personal responsibility for the safe use of pesticides were lower among agricultural than non-agricultural workers. The agricultural workers were also more likely to engage in risky behaviors in the home. However, certain behaviors were only considered risky when the participant had a household member who worked in agriculture, which was significantly more common among participants who worked in agriculture themselves (chi-sq p
< 0.01). Thus, while it is difficult to assess the true association between working in agriculture and engaging in unsafe practices in the home, we preliminarily conclude that the agricultural workers in our study likely have a greater potential for exposure to pesticides in the home due to the significant association with risky behaviors.
Risky behaviors were less common in our study population than in other populations, including pregnant agricultural workers in California [45
] as well as other Thai agricultural worker populations [12
]. While the women in our study may truly be less likely to engage in certain risky behaviors, our pilot tests showed that some participants may be unlikely to admit to engaging in risky behaviors due to a desire to please researchers. Other survey-based studies of behavior among populations of Asian women have introduced similar concerns about the potential for reporting or desirability bias [58
]. Although we attempted to minimize this bias by asking the behavior questions before the knowledge questions, this bias may not be completely removed through a multiple choice survey conducted in a face-to-face interview [60
]. Future studies might consider anonymous surveys or open-ended qualitative surveys, interviews, and focus groups to further minimize this bias (see Flocks et al
4.2. Knowledge and Pregnancy Trimester: Associations with Pesticide Practices
In this study, risky behaviors were used as a measure of potential pesticide exposure during pregnancy to help identify women and children at greater risk of pesticide exposure and reveal potential targets for interventions. Higher knowledge was marginally associated with decreased odds of engaging in risky behaviors at home. On average, the odds of engaging in risky behaviors at home decreased by approximately 10% for every additional knowledge question answered correctly, preliminarily indicating that interventions designed to increase knowledge among pregnant women from all backgrounds could be effective at reducing exposures in the home. However, this association did not meet our criterion for statistical significance, thus a study with a larger sample size would be needed to confirm or reject the relationship. Knowledge was not significantly associated with risky behaviors at work in our study, perhaps also due to small sample size (n = 34 agricultural workers).
As we hypothesized, women in later stages of pregnancy (e.g., second or third trimesters) were significantly less likely to engage in risky behaviors at home. In addition, more women had worked in a job involving potential pesticide exposure, personally applied pesticides, or had pesticides applied in their home before becoming pregnant than after becoming pregnant. These observations may indicate that women alter their pesticide use behaviors when they become pregnant as well as when they advance to later stages of pregnancy. However, when we included education as a covariate in our models, the association between pregnancy trimester and risky behaviors at home was only marginally significant. In our small sample population, first trimester participants were less likely to be educated than participants in their second or third trimesters. Pregnancy trimester was not associated with risky behaviors at work, potentially due to small sample size.
4.3. Targets for Intervention
The knowledge gaps we identified in this pilot study could be used to design knowledge-based interventions aimed at pregnant women in Thailand. However, these types of interventions may not be sufficient to reduce or eliminate prenatal pesticide exposures. For example, some of the women we surveyed reported knowledge of risky behaviors but engaged in them nonetheless. These women reported other unsafe practices and their previous pesticide use habits did not appear to be influenced by their becoming pregnant. These important behavioral observations should be considered when planning interventions in this or similar populations.
In addition, regression modeling showed that neither knowledge nor pregnancy trimester alone were significantly associated with risky behaviors, but that other factors were involved. The number of risky behaviors at home was significantly associated with increased odds of engaging in risky behaviors at work. Specifically, the odds of engaging in risky behaviors at work increased two-fold for each risky behavior the participants reported at home. We preliminarily interpret this to mean that interventions designed to decrease the number of risky behaviors at home may be effective in decreasing risky behaviors at work as well. In addition, risky behaviors at home might serve as a proxy for risky behaviors at work in future studies. Behaviors at home can be assessed among all pregnant women, in contrast to behaviors at work, which typically only apply to agricultural workers.
Four other covariates were significantly associated with increased odds of engaging in risky behaviors at home in our study. These observations may help future researchers prioritize sub-groups for educational interventions. Agricultural workers were more likely to report risky behaviors at home, so the additional finding that having an agricultural job before becoming pregnant was significantly associated with risky behaviors in the home was not surprising. However, it helps underscore the importance of identifying agricultural workers as a group at elevated risk of pesticide exposure during pregnancy. Similarly, we observed that participants who reported using pesticides in the home before becoming pregnant were more likely to report unsafe pesticide use behaviors while pregnant. In addition, women with a previous child were significantly more likely to engage in risky behaviors at home during the current pregnancy. This is consistent with previous findings that within certain populations in the United States, women were more likely to engage in potentially harmful behaviors such as use of tobacco, lower utilization of prenatal care, and failure to meet diet quality and nutritional recommendations during later pregnancies than during their first [61
]. Thus, women who already have children may need reminders that safe pesticide practices during pregnancy are necessary to protect their developing fetus. Although the predictors identified in backward elimination (having a job involving farm work before becoming pregnant, using pesticides in the home before becoming pregnant, having a previous child, and having a strong belief in the child’s susceptibility to pesticides) can help identify populations at risk of exposure, these factors are not preventable through interventions implemented during pregnancy. Thus, our pilot study shows that pesticide knowledge may remain an important target for prevention activities.
4.4. Study Limitations
Our questionnaire was based on previously published work, pre-tested, pilot tested, and edited to ensure accurate translation, coherence, and relevance. However, we did not conduct a full-scale validation study, such as in Sam et al.
]. Further, knowledge may be better measured using open-ended questions, where participants are asked to provide information freely, without being influenced by potentially leading questions or a restricted number of choices. Additionally, we did not receive any critical feedback during pilot testing, so some women in our study may have wanted to please the researchers instead of answer questions accurately. Such a reporting bias may partially explain why safe practices were more prevalent in our study than in previous findings.
Our study is also limited due to small sample size (n = 76). A larger number of participants would likely be needed to detect true associations among the variables of interest within smaller subgroups such as agricultural workers or women who personally applied pesticides. Further, our primary ‘outcomes’ of interest were not direct measures of exposure, but proxy questionnaire responses. Although there is evidence that unsafe pesticide practices are associated with increased exposure in Thai populations [12
], this association has not been studied among pregnant women in Thailand or their children. While it is practical to assume that risky behaviors lead to increased exposures in this population, actual exposure measurements would be needed to validate the assumption.
Finally, behavior change interventions may have only modest impact without changes to national and international pesticide policy. The context of pesticide and agricultural policy in Thailand is unique and challenging, with weak enforcement of existing regulations and the absence of a uniform system for pesticide management [63
]. While addressing the issue of prenatal pesticide exposure at the community and societal level is outside the scope of this study, these areas offer another opportunity for intervention and the results of our KAP survey in this understudied population may be useful in such efforts.