PURPOSE: To analyze the auditory effects of the combined exposure to carbon monoxide (CO) and noise, and the impact of smoking. METHODS: Participants were 80 male workers, smokers and non-smokers, from a steel industry - 40 exposed to CO and noise simultaneously, and 40 exposed only to noise. A retrospective data analysis was conducted regarding the environmental risks (CO and noise) and the file information related to auditory health and to the biological concentrations of CO in the blood (CPHb). The first and the last pure-tone audiometry results were analyzed considering the smoking habits, the type of exposure (CO and noise or noise only), the time of exposure, the level of noise, and age. RESULTS: Both the CO concentration and the noise levels were above the tolerance limits provided by the regulatory norm number 15 of the Ministry of Labor and Employment. The group of workers exposed to CO and noise presented a higher rate of noise-induced hearing loss (22.5%), when compared to the group exposed only to noise (7.5%), as well as significant worsening of the hearing thresholds of 3, 4 and 6 kHz. Age, time of exposure, type of exposure, level of noise, and smoking habit significantly influenced the auditory threshold of the participants. Smoking enhanced the effects of both CO and noise on the auditory system. CONCLUSION: The occupational exposure to noise and CO resulted in significant effects on the auditory system of workers from a steel industry.
Noise effects; Chemical compounds; Occupational exposure; Drug synergism; Hearing loss; Occupational health
