OBJECTIVETo observe the effect of environmental risk factors in occupational noise exposure on hearing loss and find out the susceptible population of noise induced hearing loss (NIHL).

METHODSA case-control study was designed to study the effect of environmental risk factors on NIHL. 2400 workers exposed to 75 approximately 120 dB noises from an air conditioning factory in southern China served as the subjects. 202 workers were selected from 10% of population with the maximum hearing shift of the left ear to 3000 Hz noises as the NIHL susceptible group while 204 workers from 10% of population with the least hearing shift as the NIHL tolerant group. A questionnaire was designed to carry out an investigation, and an occupational health survey was used to identify the occupational risk factors which might affect the hearing system. The univariate analysis and multivariate analysis were used to observe the effect of environmental risk factors on NIHL.

RESULTSThe results of univariate analysis showed that smoking, alcohol drinking, organic solvent, heavy metal, heat, dust were significantly was associated with NIHL (P < 0.05). Multivariate analysis showed that only heat was associated with NIHL (P < 0.05), and OR value was 1.804 (95% CI: 1.101 approximately 2.958).

CONCLUSIONExposure to heat may be a high risk factor of NIHL.