A geographical information system technique for record-matching in a study of cancer deaths in welders

Retrospective studies are frequently complicated by incomplete worker identifiers. We encountered this problem when evaluating the risk of cancer death in a welding cohort. We dealt with it by developing birth-date ranges for each welder with unknown birth dates and using geographical information system techniques in conjunction with last name, gender, and birth-date range to assign death certificates to welders on the basis of residential proximity to the worksite. Deaths for total malignant cancers and lung/tracheobronchial/pleural cancers among these welders were not significantly different from those in county, state, and US populations, using standardized mortality ratios. The ratios in our study subjects were consistent with ratios found in other published welder cohorts.