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AbstractPurpose Noise exposure is an important and highly pre-valent occupational hazard in the construction industry.This study examines hearing threshold levels of a largepopulation of Dutch construction workers and comparestheir hearing thresholds to those predicted by ISO-1999.Methods In this retrospective study, medical records ofperiodic occupational health examinations of 29,644 con-struction workers are analysed. Pure-tone audiometricthresholds of noise-exposed workers are compared to anon-exposed control group and to ISO-1999 predictions.Regression analyses are conducted to explore the rela-tionship between hearing loss and noise intensity, noiseexposure time and the use of hearing protection.Results Noise-exposed workers had greater hearing los-ses compared to their non-noise-exposed colleagues and tothe reference population reported in ISO-1999. Noiseexposure explained only a small proportion of hearing loss.When the daily noise exposure level rose from 80 dB(A)towards 96 dB(A), only a minor increase in hearing loss isshown. 50131
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The relation of exposure time and hearing lossfound was similar to ISO-1999 predictions when looking atdurations of 10 years or more. For the first decade, the population medians show poorer hearing than predicted byISO-1999.Discussion Duration of noise exposure was a better pre-dictor than noise exposure levels, probably because of thelimitations in noise exposure estimations. In this popula-tion, noise-induced hearing loss was already present at thebeginning of employment and increased at the same rate asis predicted for longer exposure durations.Keywords Noise-induced hearing loss Occupationalnoise exposure Pure-tone audiometry Ear protectivedevices Retrospective studiesIntroductionNoise is an important occupational health hazard, with ahigh prevalence in the construction industry. The noiseexposure of construction workers varies greatly with theactivities performed and the equipment used on the work-site (Hong 2005), frequently exceeding daily noise expo-sure levels of 80 dB(A), which the European Directive2003/10/EC defines as lower action level. This directivealso considers an upper action level of 85 dB(A), at whichthe use of hearing protection is mandatory, and an exposurelimit of 87 dB(A) that takes the attenuation of inpidualhearing protectors into account.Long-term exposure to daily noise levels above thelower action level of 80 dB(A) may eventually causenoise-induced hearing loss (NIHL), a bilateral sensorineu-ral hearing impairment. Typically, the first sign of NIHL isa notching of the audiogram at 3, 4 or 6 kHz, with arecovery at 8 kHz (May 2000). This audiometric notchdeepens and gradually develops towards the lower fre-quencies when noise exposure continues (Ro ¨sler 1994). As a result of the high noise exposures in construction,NIHL is one of the major occupational health problems inthis industry. It may have a great impact on a workers’quality of life (May 2000), and it also influences workers’communication and safety (Suter 2002). NIHL is the mostreported occupational disease in the Dutch constructionsector, with a prevalence of 15.1% in 2008 (NCvB 2009).In other countries, NIHL is one of most prevalent occu-pational diseases among construction workers as well(Arndt et al. 1996; Hessel 2000; Hong 2005) and preva-lence estimations range from 10% in the USA (Dobie2008) to 37% in Australia (Kurmis and Apps 2007). Alarge US analysis of self-reported hearing impairment inindustrial sectors showed that the largest number ofemployees with hearing difficulty attributable to employ-ment was found in the construction industry (Tak andCalvert 2008).Previous studies showed a dose–response relationship ofexposure to noise and hearing loss. Higher exposure levelsand longer exposure durations cause greater hearingimpairment (Ro ¨sler 1994; Prince 2002; Rabinowitz et al.2007; Dobie 2007). This relationship is mathematicallydescribed in the international standard ISO-1999 (ISO1990), predicting both the distribution of the expectednoise-induced threshold worsening in populations exposedto continuous noise, and the total hearing levels resultingfrom NIHL in combination with age-related hearing loss.Hence, the standard also incorporates a database for hear-ing thresholds as a function of age, for male and femalepopulations separately. This algorithm, indicated as data-base A, is an internationally well-accepted reference,derived from data of an otologically screened non-noise-exposed population.The expected noise-induced threshold change is afunction of noise exposure level and exposure time.Characteristically, NIHL develops progressively in the first10–15 years of noise exposure, followed by a slowing rateof growth with additional exposure to noise (Taylor et al.1965; ISO 1990;Ro ¨sler 1994). This pattern is representedin the ISO-1999 model. However, these predictions arebased on data from subjects exposed for 10 years or more.The algorithm to predict hearing damage in the first10 years is interpolated from the predicted median NIHLafter 10 years of exposure and the assumed hearingthreshold of 0 dB HL at the beginning of exposure (ISO1990), resulting in a steep linear increase in hearing lossduring the first years of exposure.A study of NIHL in railway workers showed that 20% offinal hearing loss at 2 and 4 kHz was already establishedafter the first year of noise exposure. This highly exceededthe predictions of the ISO model, yet after 3–4 years ofexposure data and model are in close agreement (Hender-son and Saunders 1998). On the contrary, another studyfound only a slight increase in hearing threshold levels(HTLs) of construction apprentices after the first 3 years ofemployment in construction industry (Seixas et al. 2005),which was much smaller than predicted by ISO-1999.Because NIHL is preventable, hearing conservationprogrammes are established, often relying on employee’suse of hearing protection devices (HPDs) rather than oncontrolling the noise exposure at its source (Neitzel andSeixas 2005). Protection from HPDs depends largely on theconsistency of usage, because noise exposure during non-use greatly reduces their effectiveness (Neitzel and Seixas2005). Discomfort, hinder to communication and highlyvariable noise levels, which are common in construction,can cause irregular use of HPDs (Suter 2002; Neitzel andSeixas 2005). Several studies focusing on the use ofhearing protectors in construction demonstrated low levelof HPD usage; Lusk et al. (1998) found that workers indifferent construction trades reported to wear protectionduring only 18–49% of the time exposed to self-reportedhigh noise. In a more recent study, this percentage was41% (Edelson et al. 2009). Neitzel and Seixas (2005)reported an even lower percentage of usage of less than25% of the time that combined with the amount of atten-uation resulted in negligible effective protection (Neitzeland Seixas 2005). Nevertheless, a study examining hearingloss in Canadian construction workers showed that HPDusage was common ([90%) and resulted in a protectiveeffect on hearing (Hessel 2000).These different findings underline the complicating effectsof the consistency of HPD usage in assessing the relationshipbetween occupational noise exposure and NIHL.In addition, there is also a great variability in inpidualsusceptibility to hearing loss (Henderson et al. 1993; Sli-winska-Kowalska et al. 2006), partly explained by otherpossible causes of hearing loss. These are both intrinsic andexternal factors (Sliwinska-Kowalska et al. 2006; Princeet al. 2003). Intrinsic factors are for example gender, race,genetics, medical history and hypertension (De MoraesMarchiori et al. 2006). External factors concern ototoxicity,leisure noise exposure,