Abstract:

A holistic approach to studying the workplace as a combination of physical, chemical, biological, and organizational factors is receiving growing attention. This approach includes initiatives to investigate the potential interaction between noise and chemicals. NIOSH has conducted three cross-sectional studies on the effects of solvents on hearing, alone or in combination with noise. Audiometric thresholds were compared with ISO 1999 estimates, and the prevalence, risk ratios, and predicted probability of developing a hearing loss were calculated. In all of the investigations, solvent mixtures which had toluene as a main component were found to affect the hearing of workers exposed to low noise levels. Considering the multiplicity of chemicals that are used occupationally and evidence that some are ototoxic, it is conceivable that numerous populations are being underserved regarding hearing loss prevention since the permissible exposure levels for chemicals do not take into account their potentiation of hearing loss. Workers who are exposed to A-weighted noise levels below 85 dB time-weighted average are not required to be included in hearing conservation programs. Furthermore, methods currently used in hearing conservation (e.g., hearing protectors and noise control) may be insufficient, or even inappropriate, for workers exposed to both chemicals and noise.