Occupational Noise Exposure

After workplace injuries, occupational noise exposure is the most common risk factor in the workplace (WHO Europe, 2017). For hundreds of years we have known that time spent working in noisy workplaces may lead to Noise-Induced Hearing Loss (NIHL). But despite this, occupational noise-induced hearing loss is the most prevalent occupational disease in the world.


While scientists and physicians have addressed NIHL over the centuries, a Glaswegian surgeon, Thomas Barr, is credited with one of the first controlled epidemiological studies into the effects of occupational noise. Barr examined the link between his patients’ work and their deafness, and in 1886 he reported that c. 75% of boilermakers had difficulty in hearing. He also identified the critical elements of NIHL and also the need for hearing protection, the earlier forms of which were rolled from cotton wool. While Barr noted the characteristic loss at high frequencies, significant progress in the formulation of risk criteria was not made until after World War II. However, major political and scientific barriers gave rise to widespread reluctance in regulating noise exposure. Initially uncertainties in the understanding of variations in individual susceptibility made it impractical to specify the criteria necessary to protect every worker’s ears throughout their working lifetime.

Notwithstanding, the many scientific and political challenges, and carried on the tide of sweeping societal and workplace change, over 60 years ago, criteria were established to ‘preserve hearing at the frequencies important for good speech recognition’ (Burns and Littler, 1960). These criteria were formally endorsed in the ‘Wilson Report’ (HMSO, 1963) which recommended that the UK Ministry for Labour should publicise information pertaining to the danger of noise and the need to reduce exposure. This was achieved with the publication of ‘Noise and the Worker’ (HMSO, 1963). This latter publication encouraged employers to address noise exposure in the workplace; and in Common Law 1963 is, thus, regarded as the definitive timeframe from which ‘guilty knowledge’ applies.




Statutory controls


Amongst workers and populations who are subject to similar exposures, some will exhibit extensive hearing loss while others will demonstrate negligible effects. While undoubtedly the individual differences (in NIHL) can be partly attributed to differences in humans’ vulnerability to the effects of noise; it is also attributed to actual differences in personal exposure. This is because all workers in an industrial setting (or even within a particular department or job) do not necessarily acquire the same exposure.

Natural variations in individual susceptibility were some of the factors which initially distracted and deferred the legislators from imposing statutory obligations on employers to protect their employees’ hearing. However, legislation has evolved throughout the EU and internationally which initially was targeted at protecting people with ‘average sensitivities’. Thus, the ‘original’ EU Directive (European Union Council, 1986) provided for minimum statutory obligations when the daily noise exposure level (LEX, 8h) exceeded 85 dBA. The 2003 Directive (2003/10/EC) provided even more stringent controls than the 1986 Directive and some of these take effect when workers’ LEX, 8h exceeds 80 dBA.

The cornerstone of the EU’s occupational safety legislation (Directive 89/391/EEC) emphasises the need to eliminate risk. Furthermore, the 1989 Machinery Directive and subsequent amendments (89/392/EEC and 2006/42/EC) have ensured that since 1993 most machinery supplied in the EU has fulfilled essential health and safety requirements.

The ‘Machinery Directive’ sets out procedures and standards that manufacturers must conform to and only conforming machinery is permitted to carry the CE mark. The provisions are designed to ensure that the accidents and injuries caused by the use of machinery can be reduced. The EU emphasis, therefore, is on inherently safe design and construction of machinery and on proper installation and maintenance. This works in harmony with the ‘Physical Agents (Noise) Directive’ (2003/10/EC) with the former, providing a commercial incentive for equipment designers and manufacturers to produce quieter or ‘silenced’ alternatives.


SOURCE:

https://www.hsimagazine.com/article/occupational-noise-exposure/