Occupational noise: Assessing the burden of disease from work-related hearing impairment at national and local levels
Environmental burden of disease series, No. 9
This guide outlines a method for estimating the disease burden of hearing loss caused by high levels of noise in the workplace, at national, city or local levels. The method assesses exposure at two noise levels (85−90 and >90 dB(A)), and by occupational category and economic subsector. These measurements are combined with the proportions of the working population in different occupations and subsectors, and with the proportion of the working-age population that is employed, by gender. All of the data can be obtained either from national statistics, the International Labour Organization (ILO), WHO, or by extrapolating from existing studies.
The information on exposure is then combined with estimates of the relative risks of developing noise-induced hearing loss (NIHL), derived from literature reviews. This gives the attributable fraction (i.e. the proportion of the total burden of NIHL in the study population that is caused by occupational noise). To give the total disease burden caused by occupational NIHL, the attributable fraction is multiplied by the total disease burden for NIHL. Total disease burden statistics can be obtained either from national statistics, national burden of disease studies, or from WHO. Depending on the aim of the assessment, the attributable burden can be expressed in terms of the incidence of NIHL, or as disability-adjusted life years (DALYs).
In addition to providing aggregate estimates, the method in the guide can be used to highlight the health impacts on population subgroups at particular risk, such as occupational subgroups or women, provided that exposure in these subgroups is assessed separately. The quantification of the health impacts also provides anopportunity to highlight the disease burden that could be avoided by interventions to reduce occupational noise exposures. This can motivate policy action to reduce exposure to this risk factor and thus reduce the disease burden of the population.