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Occup Environ Med 2005;62:309-317 doi:10.1136/oem.2004.018143
  • Original article

Prospective noise induced changes to hearing among construction industry apprentices

  1. N S Seixas1,
  2. B Goldman1,
  3. L Sheppard1,
  4. R Neitzel1,
  5. S Norton2,
  6. S G Kujawa3
  1. 1University of Washington, Department of Environmental and Occupational Health Sciences, Seattle, WA, USA
  2. 2Children’s Hospital and Regional Medical Center, Seattle, WA, USA
  3. 3Department of Otology and Laryngology, Harvard Medical School and Massachusetts Eye and Ear Infirmary, Boston, MA, USA
  1. Correspondence to:
 Dr N Seixas
 University of Washington, Department of Environmental and Occupational Health Sciences, Seattle, WA, USA; nseixasu.washington.edu
  • Accepted 6 January 2005

Abstract

Aims: To characterise the development of noise induced damage to hearing.

Methods: Hearing and noise exposure were prospectively monitored among a cohort of newly enrolled construction industry apprentices and a comparison group of graduate students, using standard pure tone audiometry and distortion product otoacoustic emissions (DPOAEs). A total of 328 subjects (632 ears) were monitored annually an average of 3.4 times. In parallel to these measures, noise exposure and hearing protection device (HPD) use were extensively monitored during construction work tasks. Recreational/non-occupational exposures also were queried and monitored in subgroups of subjects. Trade specific mean exposure Leq levels, with and without accounting for the variable use of hearing protection in each trade, were calculated and used to group subjects by trade specific exposure level. Mixed effects models were used to estimate the change in hearing outcomes over time for each exposure group.

Results: Small but significant exposure related changes in DPOAEs over time were observed, especially at 4 kHz with stimulus levels (L1) between 50 and 75 dB, with less clear but similar patterns observed at 3 kHz. After controlling for covariates, the high exposure group had annual changes in 4 kHz emissions of about 0.5 dB per year. Pure tone audiometric thresholds displayed only slight trends towards increased threshold levels with increasing exposure groups. Some unexpected results were observed, including an apparent increase in DPOAEs among controls over time, and improvement in behavioural thresholds among controls at 6 kHz only.

Conclusions: Results indicate that construction apprentices in their first three years of work, with average noise exposures under 90 dBA, have measurable losses of hearing function. Despite numerous challenges in using DPOAEs for hearing surveillance in an industrial setting, they appear somewhat more sensitive to these early changes than is evident with standard pure tone audiometry.

Footnotes

  • Competing interests: none

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