New research indicates chronic exposure to noise and workplace carbon monoxide induces hearing loss, and truckers are among those most at risk.
A connection between carbon monoxide exposure and hearing loss had been established in animal studies, but not in humans.
The conclusions were based on a study of nearly 9,000 workers exposed to both occupational noise and carbon monoxide. Other than truckers, the workers most at risk were welders, firefighters, garage mechanics, forklift operators and miners.
The University of Montreal study, using National Institute of Occupational Safety and Health data, compared the hearing of workers exposed to noise levels lower than 90 decibels for 8 hours to the hearing of workers exposed to noise above 90 decibels. In both groups, a sample of workers also was exposed to carbon monoxide.
The study found employees exposed to carbon monoxide and to noise levels above 90 decibels displayed significantly poorer hearing thresholds at high frequencies. Several hypotheses might explain this effect. One is that reducing blood oxygen levels accelerates the deterioration of inner ear sensory cells.