An exposure score of 1 (low) when a participant welded frequently (1e3 days per week) and an exposure score of 4 (high) was assigned when welding was part of day-to-day work (4 or more days per week). Participants also received an exposure score of 1 (low) for each year with more than 50 days of non-work related welding. Duration of exposure to metals, solvents or welding fumes was defined as number of years with low or high exposure. Cumulative exposure was calculated by summing the exposure score (0, 1 or 4) for all years until the year prior to diagnosis.