Suggested guidelines for studying the combined effects of occupational exposure to noise and chemicals on hearing

The present document, which describes recommended standardized procedures, aims to assist individual investigators plan a study on the effects of industrial chemicals on the auditory system, collect and analyze environmental and hearing sensitivity data that are accurate and comparable to data acquired by others. This draft document is currently being reviewed by the NoiseChem Research Group. In this peer review stage we are currently accepting critiques and suggestions to this proposal. Investigations on the aforementioned topic are necessary since there is strong evidence that occupational hearing loss may be caused not only by noise but also by exposure to certain chemicals in the work environment. Since some industrial chemicals are known to be ototoxic, it is plausible to expect that if these chemicals occurred in high enough concentrations in the workplace they could affect hearing. Laboratory studies have yielded a finding not expected, namely that when simultaneous exposure to noise and chemicals occur, the hearing loss observed was greater than the expected hearing loss from noise added to the expected hearing loss from the chemical. If this synergism is verified in humans, then changes will be required in the limits that are set for occupational hazards in order to prevent occupational hearing loss.