Assessing Exposure to Crystalline Silica from Farm Work: A Population-based Study in the Southeastern United States

PURPOSE: Farm workers are exposed to crystalline silica, but there are no established questionnaires to assess silica dust exposure from farm work in epidemiologic studies. This study examines aspects of farm work that were used to estimate potential silica dust exposure in a population-based study conducted in the southeastern United States. METHODS: We collected work and farming histories through in-person interviews with 620 participants in a population-based case-control study of systemic lupus erythematosus. A dust-exposure matrix was used to develop a telephone interview for 69 participants with potential medium- or high-level exposure, including questions on tasks, frequency, and farm location. Soil systems maps were used to infer soil type (sandy/other). Exposure indices were constructed based on tasks, frequency, and soil type. RESULTS: Thirty-six percent of study participants worked on a farm, but only 52 (8%) were classified in the high (n = 16) or medium (n = 36) exposure groups based on responses to follow-up interview questions. Exposure indices based on open-ended job descriptions in initial interviews correctly categorized 52% of participants who answered prompted questions on relevant dusty tasks in follow-up interviews. CONCLUSIONS: Specific questions on dusty tasks and frequency are needed to accurately assess silica exposure from farm work.