Silent treatment

In all the clamour about safety in mining, one significant cause of injury is often forgotten — noise. By Ian Henderson*

Staff Reporter

The fact that mining is one of the world’s noisiest industries is neither new nor surprising. What is often underestimated is the link between industrial noise, productivity and economic burden. Despite a long history of documentation of industrial noise effects and solutions, mining continues to face a huge challenge in this area.

It would be inaccurate to talk in general terms about noise levels in the mining industry because many areas defy the stereotype in being quite peaceful. Where it does get very noisy is in the vicinity of vehicles and machinery (see table below). To give this a familiar context, lawnmowers and chainsaws operate at roughly 100dB(A).

Other sources of high level noise are ball mills, explosives, mechanical shovels and site workshops. Dismissal of this noise as just the “nature of the beast” is often made at great human and practical cost, especially as “the beast” may in many cases be tamed through isolation, replacement and/or modification.

If you need to shout or use a raised voice to be heard by someone at arm’s length, the surrounding noise is possibly dangerous. If you think a noise is too loud or uncomfortable, it may be slowly damaging your hearing.

Research shows that 20% of people who work eight hours a day, five days a week in an area where the noise level is 90dB(A) for a 10-year period can expect to have significant hearing loss. Therefore, nearly all international regulations stipulate 85dB over an eight-hour day as the “action level” for noise exposure to workers. An important qualification to this, however, is that even at this level there may be a 6% risk of acquiring hearing loss. Only at 75dB does the risk become negligible.

In Australia, it has been estimated that of the 30,000 or so people involved in the Western Australian mining industry, nearly half are exposed to noise above the regulatory “action level”.This suggests that while great progress has been made in addressing mining industry noise in recent decades, significant efforts are still required.

Noise injury is the most prevalent occupational hazard in heavy industry. Unlike handling injuries, falls and chemical exposure, its symptoms are mostly “invisible”: no blood or broken bones, no ambulances, hospitalisation or fatalities. One result of this is the lack of tangible “legitimacy” for access to rehabilitation and compensation. And there are other insidious personal and economic impacts.

The signs of noise injury include hearing loss, reduced speech clarity (especially in background noise), irritation and anxiety. Hearing loss is the most obvious of these. There are also problems such as tinnitus or “head noises”, headaches, hypertension and ischaemic heart disease, vertigo or dizziness, and muscular tension.

The question of how these effects interact with worker performance and output has been of interest to researchers for some decades. While unanswered questions remain, some disturbing themes have emerged. Industrial noise can significantly reduce productivity, and increase absenteeism and lost﷓time accidents. Laboratory studies have also demonstrated loss of performance associated with noise, and the occurrence of increased problem solving errors, reduced comprehension of written material, and impaired memory, recollection of order and ability to focus on nearby activity. It is notable that many of these symptoms result from noise intensities well below the regulation industrial “action level” of 85dB(A). People who are accustomed to ongoing noise are also found to make, for example, more errors. Most concerning is the belief that many of these laboratory findings may be worse in the workplace setting.

It is not difficult to imagine the potential result of impaired memory and problem solving ability, combined with reduced motivation, in the workplace. To illustrate the breadth of impact noise has on industry, Worksafe Australia in 1991 estimated that $1880 is lost annually per noise-exposed employee.

While the estimates are now outdated, the breakdown is significant in considering more than the obvious costs of compensation, hearing protection, audiometry etc. On this theme, a British researcher (Berger, 1986) estimated the cost of noise related absenteeism to be as great as 13 times that of compensation claim payouts.

In Australia, mining is included among those industries with the highest incidence of noise injury compensation claims against employers. In New South Wales, in 1996-97, 52% of all claims were for noise-induced hearing loss. Other industries experiencing high claim rates include transport equipment and metal products manufacturing; and the building and construction industry. The total cost relating to these legal claims is approximately $70 million a year. As far as mining and mineral processing is concerned, in 1988-89 the compensation cost of noise induced hearing loss in South Australia, Queensland, New South Wales and Victoria totalled $2.5 million. By 1995-96 the national cost was $11 million. A simple weighting of the four state/national figures for the sake of comparison points to a worrying trend. This is partly due to a growing awareness of the compensation process, rather than an increase in noise injury per se. Other expenses include common law suits and rehabilitation costs, the former being up to 10 times the latter.

In summary, the economic cost of industrial noise is now believed to be much worse than is conventionally estimated, largely due to the emergence of “hidden costs” such as worker performance, absenteeism and job satisfaction.

Reducing the costly and damaging effects of industrial noise can be achieved by company﷓driven noise management programs. Elements of these include:

* Commitment of management to reduce damaging noise.

* Staff awareness of noise and the Noise Management Plan.

* Site planning: layout which separates noisy areas from workers as much as possible.

* Quieter work practices — can activities be made quieter?

* Engineering noise control.

* “Buy quiet”, or purchase and replacement of reduced-noise equipment.

* Installation of equipment to ensure it meets sound level specifications.

* Personal hearing protection, including ear plugs and muffs.

* Noise surveys and recommendations by qualified professionals.

* Administrative controls (for example, rotating workers between noisy and quiet places).

* Monitoring staff hearing levels.

* Adherence to legal requirements.

Continuedin Part 2.