Exposure of motor vehicle examiners to carbon monoxide: a historical prospective mortality study

The National Institute for Occupational Safety and Health (NIOSH) investigated the health effects of chronic exposure to low concentrations of carbon monoxide by conducting a historical prospective cohort study of mortality patterns among 1,558 white male motor vehicle examiners who were employed in New Jersey for a minimum of 6 months between 1944 and 1973. Industrial hygiene surveys indicated that the examiners were exposed to carbon monoxide at a time-weighted average (TWA) of 10-24 ppm; the exposure level recommended by NIOSH is 35 ppm TWA. A modified life table technique was used to calculate cause-specific expected deaths for the cohort adjusted for age and calendar time periods. The expected deaths were compared to the number of observed deaths through August 1973. The cohort demonstrated a slight overall increase in cardiovascular disease deaths (124 observed vs. 118.4 expected), but a more pronounced excess was observed within the first 10 yr. following employment (28 observed vs. 20.9 expected). A statistically significant excess of cancer mortality was found for motor vehicle examiners after 30 yr latency (13 observed vs. 6.9 expected, P < 0.5); this excess, however, was not confined to any particular organ site. The number of deaths due to accidents was significantly lower than expected (8 observed vs. 19.6 expected, P < .01).