Despite contributing substantially to the safety of car occupants in road accidents, air bags may also be causing hearing loss due to the high level of noise generated by their inflation, say Graham Buckley and colleagues from St James's University Hospital, Leeds UK and the vehicle Safety Research Centre, Loughborough in this week's British Medical Journal (BMJ).
The inflation of an air bag is triggered by vehicle deceleration and can generate a sound pressure level of 150-170 decibels which lasts for 0.1 seconds. The researchers state that even though such levels have not caused permanent damage to the ears during tests on monkeys, they believe air bag inflation could cause acoustic trauma in some humans. The authors base their findings on two specific cases whereby drivers suffered hearing loss and persistent tinnitus which they believe may have resulted from air bag inflation in low speed collisions.
The authors fear that injuries from air bags may be more common in the future, as current safety design is moving towards vehicles with air bags that inflate in frontal and side crashes for both front seat passengers. They suggest that lack of space means that side air bags inflate very quickly and are closer to the ear. The authors believe that such incidents of hearing loss could be under reported as they are being attributed to other factors associated with an accident - a victim is unlikely to register or remember the noise of the air bag. It is therefore unclear whether the two cases that they cite are isolated incidents or whether they represent a more widespread problem.
