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Industrial Noise Exposure

Published: 10th Dec 2011 in OSA Magazine

Occupational noise exposure has been linked to a variety of negative health effects by various researchers around the world. Occupational noise induced hearing loss (NIHL) is the most prevalent irreversible industrial disease and noise is the biggest compensable occupational hazard in many countries according to a WHO report.

It is estimated that cost of noise to developed countries ranges from 0.2 to 2% of the GDP. The third European survey on working conditions (2000) estimated that around 20% of the workers (about 40 million workers) were exposed to loud occupational noise.

Worldwide, 16% of the disabling hearing loss in adults is attributed to occupational noise, ranging from 7 to 21% in various regions. This measure for South

East Asian regions SEAR-B and SEAR-D is reported as 19 and 16% respectively.

Most of the developing countries in the south Asian region and south east Asian regions have affected the legislation against occupational noise, but the enforcement and implementation in these countries remains very poor. For example, Nearly 3 billion dollars has been paid as compensation for NIHL in the USA in the last two decades, whereas owing to the lack of awareness among industrial workers and for other reasons, the first compensation in India in this regard was paid in 1996 only, though NIHL has been in the list of compensable diseases since 1948.

It seems that occupational noise is being accepted as an integral part of the work in developing countries, especially by a number of organisations (employers as well as employees) where the traditional methods and machinery are still being used. Industrialisation without protection in developing countries is also contributing towards increases in the average noise levels.

Directive for noise control

Almost all the legislation for occupational noise control worldwide states the limiting values of noise exposure between 85 – 90 dB(A) Leq for eight hours exposure, which is based on the guidelines contained in ISO-1999:1990. France, Sweden, Norway, New Zealand and Spain allow 85 dB(A) Leq. These limits are allowed for halving rates of 3 dB(A) and working schedules of eight hours per day. OSHA (USA) allows 90 dB(A) for an eight hour working day, with halving rate of 5 dB(A).

The noise control directive of EC (2003) states the exposure limit of 87 dB(A) Leq for eight hours duration. Control of Noise at Work Regulations 2005 state an exposure limit of 87 dB(A) Leq for eight hours duration in the UK, in line with the EC directive.

Developing countries have traditionally adopted the limit values stated by the developed nations, without much consideration about the local issues and parameters which may be of immense importance. For example, in India, model rules under the Indian Factories Act of 1948 stipulate a limit of 90 dB(A) for eight hours exposure. But due consideration shall be given to the fact that most of the plants in India operate six days a week and total noise exposure per week is therefore 48 hours. This is in excess of the cumulative noise exposure, which is the basis of arriving at this limiting value in developed nations.

Specific industrial tests - textiles

A number of studies have been carried out by the author and co-workers in last few years to evaluate the extent of noise exposure prevalent in various types of industries in India. Results of the study of occupational noise in two textile plants show that overall noise levels and exposure to noise ranged between 80 and 102dB(A) Leq. The details of the Leq values of noise to which the workers are exposed in various work areas is shown in Table 1 and Table 2.
The daily noise exposure of workers in areas like loom shed, ring frame, TFO (two for one twisting machine area) exceeds the maximum exposure limit of 90 dB(A), specified by OSHA. The noise exposure in other work areas like the blow room or combing area is recorded at less than 90 dB(A), but is significantly higher than limits used for the assessment of community noise.

In a metalworks’ context

Another study on five small scale forging units reveals that overall noise level and exposure to noise in the forging units under study ranged from 86.5 and 110dB (A) Leq. The daily exposure of workers in sections like blank cutting, forging, punching press, wheel and belt grinding, barrelling section, broaching, gauging and sizing exceeds the maximum exposure limit of 90dB (A) specified by Indian legislation. The noise exposure in other work areas like nickel plating, machine section, die section is recorded at less than 90dB (A), but is significantly higher than the limits used for the assessment of community noise.

In another study on impact noise due to drop forge hammers, it is found that equivalent sound pressure level in most of the sites is higher than 100 dB(A).

The details of the Leq values of noise to which the workers are exposed is shown in Table 3.

The situation will become more critical if the impulsive character of the noise is also taken into account by applying correction factor of +5dB, as is done in the case of evaluating community response to noise.

Most of the workers employed in these industries as skilled or semi skilled workers are illiterate or semi literate, having no knowledge about the noise regulations and the adverse effects of noise on their performance and health.

The studies presented here clearly demonstrate that the workers in textile industries and small scale forging units are at high risk of developing noise induced hearing loss and other associated ailments due to excessive occupational exposure to noise. In fact, similar situations prevail in many small scale industries, contributing almost 40% of the gross industrial value added in the Indian economy.

The SSI (small scale industries) sector in India creates the largest employment opportunities for the Indian populace, next only to agriculture. It is estimated that the number of persons employed in these industries was around 32 million in the year 2008. There is an urgent need to establish a hearing conversation programme in these industries, the components of which should include noise assessment, increasing awareness among the workers about the adverse effects of noise, and the use of hearing protection devices and audiometry.

The workers’ perspective of occupational noise

There is a need to promote occupational safety and health through the combined efforts of workers, co-workers, managers and organisations as a whole. To promote the participation of workers in the hearing conservation programmes it is important to document subjective responses of workers to occupational noise.

In one of the studies reported above about occupational noise in textile industries, employees selected for the study were asked various questions regarding the noise in the working environment and their response to each question was recorded. The various questions posed to workers are listed in Table 4.

The answers to these questions in the reported study as presented below can also help in designing training and educational programmes. Noise was reported as a major factor causing speech interference by 70% workers. The awareness among the workers regarding the effects of exposure to high noise levels is minimal, as only 29% workers were aware of these effects. This factor is very closely related to use of hearing protection devices, which were being used by only 28% workers. The noise was considered an annoyance by 41% workers.

The extent of annoyance observed in this study ran counter to many research studies reporting very high annoyance levels. A possible reason which was revealed by further questioning of workers could be that perceived annoyance caused by noise reduces as the exposure time to consistently high noise levels increases.

The various subjective parameters like speech interference, annoyance and headache during working hours reported by workers is directly related to noise levels in the work area, as can be interpreted from Fig. 1 and Fig. 2, wherein the response ratio of workers’ answers to these questions in two work areas, e.g. Loom Shed (Leq= 102dB(A)) and Blow Room (Leq= 80dB(A)) are compared.

Such simple and effective questionnaires can be used in the workplace not only to have a look at the noise problem from a worker’s perspective, but they can also help in assessing the effectiveness of hearing conservation programmes, if already implemented.

Behavioural aspects of hearing conservation

The EC noise control directive of 2003 states the exposure limit of 87 dB(A) Leq for eight hours duration. At the lower exposure action value of 80 dB(A) Leq hearing protectors should be made available to workers and at the upper exposure action level of
85 dB(A) Leq providing hearing protectors is mandatory.

The exposure limit of 87 dB(A) Leq seems to address the issue of noise induced hearing loss by lowering down the exposure limit, but the 87 dB(A) Leq limit comes with the following condition: “When applying the exposure limit values, the determination of the worker’s effective exposure shall take account of the attenuation provided by the individual hearing protectors worn by the worker.”

Providing limit values which include the attenuation provided by hearing protectors is an issue which is debatable worldwide, because it may lead to no reduction in noise levels generated across industries.

Practical considerations

With reference to the developing nations like India, the limit of 90dB(A) for an eight hour day stipulated by OSHA (and also stated by Indian Factories Act of 1947) should be followed with a caution, as working hours in most of the plants in India are eight hours a day, six days a week – not five, as is commonplace in the USA.

In fact, total working hours per week in India are about 20% more than those in USA or in European countries.

One way to take care of this issue is by setting up a lower exposure limit for developing countries like India, which will call for modifications/replacements of the traditional methods/technologies in high noise producing industries. This may not be practical, however, because of economic considerations.

Replacement of traditional, high noise generating machinery/processes with a quiet process is generally capital intensive.

The second option available is to adopt the last line of defence against occupational noise e.g. training and education of workers regarding consistent use of hearing protectors.

It is thus observed that in this scenario, protection of employees against occupational noise is based less on technical solutions to reduce noise and lays more emphasis on checking employee behaviour about wearing hearing protectors.

It is reported in the case studies reported here, as well as by other researchers that wearing hearing protectors as a protective measure has not been a very effective solution to the noise problem because of the side effects; e.g. reduced speech recognition, which influences the normal working on shop floor, or lack of comfort.

The correct selection of hearing protectors is also equally important in this regard. The selection of the suitable hearing protector depends upon the spectrum of noise and workplace situations. It should have the right acoustic properties e.g. it must isolate at frequencies where noise exists.

Manufacturers of hearing protectors provide the mean and standard deviation for the attenuation provided by the product at various frequencies, which helps in calculating the assumed protection from noise at various frequencies.

Conclusions

The above discussion clearly emphasises the emergent need to have a subjective look at the problem of occupational noise, which will help in finding effective and practically implementable solutions. Needless to mention, the solutions will vary according to the local conditions such as economics, working conditions or worker’s awareness. These issues have not been paid much attention in the past in most of the developing economies, where there has been a trend to ape the developed nations.

Worker’s participation, education and training will also go a long way towards effective implementation of a hearing conservation programme.

Author details:

Raman Bedi is a Mechanical Engineer by profession and has been involved in teaching and research in occupational safety and health for last 13 years. Currently he is serving as Assistant Professor in the Department of Mechanical Engineering at National Institute of Technology, Jalandhar, India. He has around 20 research publications at both national and international levels to his credit. He was awarded scholarship by OHSE, Japan, to present his research on occupational noise in the year 2004. His other research interests include development of alternative materials in machine building for improved damping performance.

Please email bediraman74@gmail.com or call visit www.nitj.ac.in 

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Published: 10th Dec 2011 in OSA Magazine

Author


Raman Bedi


Raman Bedi is a Mechanical Engineer by profession and has been involved in teaching and research in occupational safety and health for last 13 years. Currently he is serving as Assistant Professor in the Department of Mechanical Engineering at National Institute of Technology, Jalandhar, India. He has around 20 research publications at both national and international levels to his credit. He was awarded scholarship by OHSE, Japan, to present his research on occupational noise in the year 2004. His other research interests include development of alternative materials in machine building for improved damping performance.
bediraman74@gmail.com


 


Raman Bedi

Website:
http://www.nitj.ac.in

Email:
bedir@nitj.ac.in

Phone:
+91-9815981054

bedir@nitj.ac.in
http://www.nitj.ac.in
+91-9815981054

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