Improving Exposure Assessment Methodologies for Epidemiological Studies on Pesticides: Study Protocol

Background Exposure to certain pesticides has been associated with several chronic diseases. However, to determine any role of pesticides in the causation of such diseases the assessment of historical exposures is required. Exposure measurement data are rarely available; therefore, assessment of historical exposures is frequently based on surrogate self-reported information, which has inherent limitations. The changing pesticide active ingredients involved, the local selection of active ingredients and the broad range of characteristics regarding their use and toxicological characteristics further complicate matters. Understanding the performance of the applied surrogate measures in exposure assessment of pesticides is therefore important to allow proper evaluation of the risks. The IMPRESS (Improving exposure assessment methodologies for epidemiological studies on pesticides) project seeks to assess the reliability and external validity of the surrogate measures used to assign exposure within individuals or groups of individuals, which are frequently based on self-reported data on exposure determinants. IMPRESS will also evaluate the size of recall bias on the misclassification of exposure to pesticides; this in turn will affect epidemiological estimates of the effect of pesticides on human health. Methods / design The IMPRESS project will recruit existing cohort participants from previous and on-going research studies primarily of epidemiological origin from Ethiopia, Malaysia, Uganda and the UK. Consenting participants of each cohort will be re-interviewed using an amended version of the original questionnaire addressing pesticide use characteristics administered to that cohort. The format and relevant questions will be retained but some extraneous questions from the original (e.g. relating to health) will be excluded for ethical and practical reasons. The reliability of pesticide exposure recall over different time-periods (<2 years, 6-12 years and >15 years) will then be evaluated. Where the original cohort study is still on-going, participants will also be asked if they wish to take part in a new exposure biomonitoring survey, which involves them providing urine samples for pesticide metabolite analysis and completing questionnaire information regarding their work activities at the time of sampling. The participant’s level of exposure to pesticides will be determined by analysing the collected urine samples for selected pesticide metabolites. The biomonitoring measurement results will be used to assess the performance of algorithm-based exposure assessment methods used in epidemiological studies to estimate individual exposures during application and re-entry work. Discussion This study protocol will be implemented during 2019-2020. This protocol will be adapted as necessary for application in the various cohorts run by the IMPRESS project partners.