Minnesota highway maintenance worker cohort mortality study: methods and noncancer mortality

In 1984, the Minnesota Department of Health (MDH) began a cohort mortality study of 4,849 workers to follow up concerns with the health and safety of highway maintenance workers (HMWs). A total of 1,530 deaths had occurred, resulting in a standardized mortality ratio (SMR) of 91 (p less than .01) and an all cancer SMR of 84 (p less than .01). There was a significant elevation in the SMR for chronic renal failure among long-term rural workers (SMR = 676, p less than .05). The SMR was also elevated for transportation injuries. The latter SMR was highest among short-term urban workers (SMR = 280, p less than .01). In addition, the SMR for transportation-related injury deaths tended to increase the later the decade of starting work. The SMRs were 137, 259, 502, and 2,145 for urban workers starting work in the decades 1945-1954, 1955-1964, 1965-1974, and 1975-1984, respectively. This study demonstrates the possible adverse health effects of highway maintenance work and the need to comprehensively evaluate injury mortality among selected occupational cohorts.