Association of work-related accidents with noise exposure in the workplace and noise-induced hearing loss based on the experience of some 240,000 person-years of observation.

This retrospective study explores the association between occupational noise exposure at the time of hearing tests, permanent noise-induced hearing loss and work-related accident risk. Log-binomial analysis was used to first ascertain the association between study variables according to activity sector (North American Industry Classification System, NAICS) and accident context while controlling for age. Second part of the paper estimates the overall number of accidents attributable to occupational noise or the associated hearing loss (excess fraction). Study was carried on a sample of 52,982 male workers exposed to a minimum of 80 dBA on a daily basis and whose hearing was examined at least once between 1983 and 1996 by public health authorities of Quebec. These participants evidenced bilateral average hearing threshold levels at 3, 4 and 6 kHz ranging from normal (< or = 15 dB) to hearing loss in excess of 50 dB as a result of chronic occupational noise exposure (subjects otherwise otologically normal). The occupational accident count of these workers was derived from the individual histories registered with the Quebec workers' compensation board for the 1983-1998 period. Results show an association between accident risk and worker's hearing sensitivity. For example, a hearing loss of 20 dB corresponds to a rise of accident risk equal to 1.14 when controlling for age and occupational noise exposure at the time of hearing tests. NAICS economic activity sectors where association is the most noticeable are "Metal Transformation", "Metal Product Manufacturing" and "Transportation Equipment Manufacturing". "Passive accidents" (PR per decibel of hearing loss = 1.008; CI 95 (1.007; 1.010)) and "same-level falls" (1.007; CI 95 (1.003; 1.010)) are the two accidents categories most strongly associated with hearing loss. Overall, 12.2% of accidents considered in this study were attributable to a combination of noise exposure in the workplace (> or = 90 dBA) and noise-induced hearing loss.