To explore two different approaches to calculate average exposure in occupational cohorts using a large occupational cohort as an example. The data for occupational cohort exposed to acrylonitrile was collected and analyzed previously by NCI; outcome was lung cancer.

Both approaches use cumulative exposure as the numerator. As the denominator, one uses the duration of exposure, while the other uses the length of employment. The former approach is used when detailed exposure history is available, and the latter is usedwhen exposure history is less detailed. The differences are investigated for a large occupational cohort.

Both approaches use cumulative exposure as the numerator. As the denominator, one uses the duration of exposure, while the other uses the length of employment. The former approach is used when detailed exposure history is available, and the latter is usedwhen exposure history is less detailed. The differences are investigated for a large occupational cohort.

Both approaches should be considered when calculating an average exposure metric.