title: The effectiveness of applying different permissible exposure limits in preserving the hearing threshold level: a systematic review.
abstract: OBJECTIVE
  A systematic review was conducted to identify the effectiveness of different permissible exposure limits in preserving the hearing threshold level. This review compared the limits of the US National Institute of Occupational Safety and Health with those of the US Occupational Safety and Health Administration. The prevalence of occupational noise-induced hearing loss is on an increasing trend globally. This review was performed to reduce the prevalence of noise-induced hearing loss.
  
  
  METHODS
  We searched 3 major databases, i.e., PubMed, Embase and Lippincott Williams & Wilkins Journals@Ovid, for studies published up until 1May 2013 without language restrictions. All study designs were included in this review. The studies were identified and retrieved by two independent authors.
  
  
  RESULTS
  Of 118 titles scanned, 14 duplicates were removed, and a total of 13 abstracts from all three databases were identified for full-text retrieval. From the full text, eight articles met the inclusion criteria for this systematic review. These articles showed acceptable quality based on our scoring system. Most of the studies indicated that temporary threshold shifts were much lower when subjects were exposed to a noise level of 85 dBA or lower.
  
  
  CONCLUSIONS
  There were more threshold shifts in subjects adopting 90 dBA compared with 85 dBA. These temporary threshold shifts may progress to permanent shifts over time. Action curtailing noise exposure among employees would be taken earlier on adoption of 85 dBA as the permissible exposure limit, and hence prevalence of noise-induced hearing loss may be reduced.
authors.affiliation: Centre for Occupational and Environmental Health, University of Malaya.
authors.forename: Balachandar S
authors.initials: BS
authors.lastname: Sayapathi
authors.forename: Anselm Ting
authors.initials: AT
authors.lastname: Su
authors.forename: David
authors.initials: D
authors.lastname: Koh
mesh_terms: D001309:Auditory Threshold / Q000502:physiology; D016206:Databases, Bibliographic; D014943:Global Health / Q000706:statistics & numerical data; D006317:Hearing Loss, Noise-Induced / Q000453:epidemiology / Q000517:prevention & control*; D006801:Humans; D009314:National Institute for Occupational Safety and Health, U.S. / Q000592:standards*; D009623:Noise, Occupational / Q000009:adverse effects* / Q000517:prevention & control; D009784:Occupational Diseases / Q000453:epidemiology / Q000209:etiology / Q000517:prevention & control; D015995:Prevalence; D020711:Threshold Limit Values; D014481:United States / Q000453:epidemiology; D014489:United States Occupational Safety and Health Administration / Q000592:standards*