Authors : Balachandar S. Sayapathi, Anselm Ting Su and David Koh
Abstract: There has been an increased in prevalence of occupational noise-induced hearing loss globally. Countries such as the US, India and Malaysia are adopting 90 dBA, as the permissible exposure limit. The aim is to explore occurrence of temporary standard threshold shifts upon adopting different permissible exposure limits: 90 and 85 dBA. In this intervention study, there were 203 participants from 2 factories. They were exposed to noise levels above action level which is 85 dBA in 1 factory and 80 dBA in another factory; the permissible exposure limits were 90 and 85 dBA, respectively. The sample size required was 52 in each factory. Noise level was measured using personal exposure noise dosimeter and sound level meter. Data on hearing threshold levels were measured using manual audiometer. Hearing protection devices with appropriate noise reduction rate were used to reduce noise exposure among participants. There were no differences in terms of occurrence of temporary standard threshold shifts among participants between the 2 factories, based on intention-to-treat and as per-protocol analysis according to the factories and machinery (noise exposure) regulations 1989, OSHA regulations and NIOSH recommended standard. This study concludes that there were no differences in terms of standard threshold shifts among employees who adopted 90 or 85 dBA as permissible exposure limits. Based on the current findings, countries adopting 90 dBA as the permissible exposure limit need not review their policies on lowering the limit but rather implementation and enforcement of legislations should be more appropriate.
Balachandar S. Sayapathi, Anselm Ting Su and David Koh, 2014. Noise-Induced Standard Threshold Shifts of 85 and 90 dBA as Permissible Exposure Limits, Post-Shift Exposure of 1 Month Duration. Research Journal of Biological Sciences, 9: 169-176.