ACUTE PESTICIDE POISONING AMONG SMALLHOLDER FARMERS AND FARMWORKERS
Methodology used by PAN UK For nearly two decades, PAN UK has conducted health monitoring surveys using a combination of surveys, desk studies, consultations, group discussion and semi-structured interviews to better understand the issue and triangulate information from different sources. Retrospective, self-reported injury histories collected using survey questionnaires are at the heart of the approach. The questionnaires have been developed by PAN UK and adapted for use in several countries in order to identify common exposure scenarios and estimate the frequency and severity of signs and symptoms of acute pesticide poisoning. The methodology is more or less standardised, but variations can be introduced to account for specific local conditions and/or explore specific issues in more detail. In remote, rural communities retrospective, self-reported injury histories are often the only practical source of information available on incidents of pesticide poisoning. However, retrospective studies are subject to recall bias and so we considered the likely accuracy and direction of bias of the results. Retrospective, self-reported injury histories are commonly used for reporting sports injuries over a 12 month sporting season. A study of the accuracy of the method (Gabbe34 et al., 2003) showed that participants were able to recall the number of injuries and the body region affected with a high degree of accuracy over a 12 month recall period. They were less accurate in their recall of detailed diagnoses beyond a 2 month period but their ability to recall these details was improved when a clear definition of the injury was reported. The recall bias over 12 months tended to lead to under-reporting of incidents, and would therefore lead to a conservative estimate of the scale of injury. A study by Jenkins35 et al., 2002, considered three studies of time-dependent memory recall and found a more significant drop in reported incidents beyond a two month period. Their conclusion was that recall periods of greater than 2 months are likely to significantly underestimate injury rates. A study of the effects of recall on reporting injury and poisoning episodes in the National Health Interview Survey in the United States (Warner36 et al., 2005) also found a significant drop in the number of reported incidents over time and pointed out that survey approaches with longer recall reference periods must accept the trade-off of loss of episodes as a result of forgotten events versus increased sample sizes due to the longer periods. The PAN UK team took the view that the trade-off was worthwhile in this case because: 66 Recall bias tends to give a conservative result 66 The seasonality of pesticide use means that collecting reports of APP over a 12 month period gives more comparable results (similar rationale to the sports injury surveys over a 12 month sporting season described above) For the purposes of the surveys, acute pesticide poisoning is defined as any symptom or health effect resulting from exposure to a pesticide within 24 hours of pesticide use. Existing tools and common signs and symptoms of acute pesticide poisoning were used as a starting point (CPAM37, Murphy et al., 200238, Thundiyil2 et al., 2008, Persson et al., 199839). Signs and symptoms that can only be determined in a clinical setting were eliminated and descriptions were adapted into simpler language that could be understood by non-clinicians. The final list is provided in Table 1. The interviewees are also asked about the frequency of incidents over the previous 12 months in order to capture information on the cumulative frequency of such episodes.
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