Background: Precise and valid exposure assessment is generally the primary challenge in retrospective occupational epidemiology studies, particularly when the only available method for exposure characterization is a personal interview. Agricultural workers may represent a particular challenge; for example, whereas many farmers have worked from childhood at the same location, raising the same crops and animals, they may have used different equipment, chemicals, and protective gear over time. One method to assist in recall is the "life events calendar," a cognitive tool based on the subject's own life history to help anchor occupational activities in time.
Methods: Unstructured interviews of farmers, focus groups, and pilot interviews among rural men, primarily African-Americans, were conducted to create a questionnaire for obtaining farm history information within the context of personal life events.
Results: Farmers used both personal events and national events (as well as events relating directly to farming) to recall their activities. These subjects had extensive history of farming (10-75 years) and chemical use (median lifetime chemicals = 13).
Conclusion: The life events calendar provided a useful tool to facilitate the recall of a lifetime of agricultural activity. Life events calendars are useful additions to the tools available for retrospective occupational exposure assessment.