The WHO Programme for Prevention of Deafness and Hearing Impairment (PDH) is especially targeted at developing countries where there is a serious lack of accurate population-based data on the prevalence and causes of deafness and hearing impairment, including noise-induced hearing loss. However, opportunities exist for prevention of noiseinduced hearing loss by primary, secondary and tertiary means and it is necessary for countries to measure the size of the problem and adopt strategies for its prevention.
The World Health Assembly has passed two resolutions in relation to PDH, in 1985 and 1995. They affirmed that much deafness and hearing impairment is avoidable or remediable and that the greatest needs for the problem are in developing countries. The 1995 resolution estimated that there are 120 million persons with disabling hearing difficulties worldwide and urged member states to set up National Programmes for the prevention of deafness and hearing impairment, with the technical assistance of WHO. WHO-PDH addresses problems in this field of major public health importance which are amenable to intervention, giving priority to the poorest developing countries. These problems include ototoxicity, chronic otitis media, noise damage to hearing, inherited and congenital causes, and the provision of appropriate affordable hearing aid services.
A fundamental requirement for the development of a National Plan and choice of preventive strategy for a National Programme is accurate, population-based data on the prevalence and causes of the problem. The PDH programme has developed a standardised Ear Disease Assessment Protocol to enable countries to conduct national surveys rapidly. A National Programme will require a set of integrated strategies to prevent deafness and hearing impairment. The PDH programme has already addressed two such causes, ototoxic drugs and chronic otitis media and will shortly produce guidelines for implementation of these strategies within the context of primary health care.
The most recent meeting organised by the PDH programme at WHO, in the series on strategies for prevention, was on the prevention of noise-induced hearing loss, held in Geneva in October 1997. The participants concluded that exposure to excessive noise is the major avoidable cause of permanent hearing impairment worldwide. Noise-induced hearing loss is the most prevalent irreversible industrial disease, and the biggest compensatable occupational hazard. In developing countries, occupational noise and urban, environmental noise are increasing risk factors for hearing impairment. The meeting recommended that all countries should implement National Programmes for the Prevention of noise-induced hearing loss, integrated with Primary Health Care, and including elements on health promotion, and measures to reduce noise sources and introduce legislation and effective hearing conservation. There is an urgent need to obtain more, accurate epidemiological data on the problem, especially in developing countries. More research is needed on basic mechanisms and means of prevention.
|How to cite this article:|
Smith AW. The World Health Organisation and the prevention of deafness and hearing impairment caused by noise. Noise Health 1998;1:6-12
| Definition and size of the problem|| |
The International Classification of Diseases (ICD-10) CHAPTER VIII, Diseases of the Ear and Mastoid Process, section "Other diseases of the inner ear" paragraph H83.3 defines noise effects on the inner ear as:
i) Acoustic trauma
ii) Noise-induced hearing loss
but does not provide any further mention or definition. The US National Institutes of Health states that a noise level of 85 dB(A) for an 8hour daily exposure is potentially damaging and will produce permanent hearing loss after many years (NIH, 1990). There are broad ranges of differences in sensitivity to noise exposure. These include age, use of ototoxic drugs, existence of a previous hearing loss and genetic factors.
In developing countries, where the PDH Programme is especially targeted, there is a serious lack of accurate population-based data on the prevalence and causes of deafness and hearing impairment. There have been a number of studies of noise-induced hearing loss in developing countries, but generally there is insufficient information to give national pictures. However, general statements such as were made by delegates at the WHO Workshop on Prevention of Hearing Impairment in Africa in 1995 (WHO-PDH, 1995) that in 8 out of the 15 countries represented noise-induced hearing loss was the second or third most important cause of hearing impairment, indicate that this is a serious and most likely growing problem. The delegates at this meeting also stated that legislation should be enacted, applied, and enforced and that health education programmes should be devised and disseminated.
| Prevention|| |
WHO defines prevention as follows:
a) PRIMARY PREVENTION: action to prevent an impairment occurring
b) SECONDARY PREVENTION: Action to prevent disability, i.e. when impairment already present
c) TERTIARY PREVENTION: Action to prevent/ minimise effects of disability, i.e. prevent handicap (WHO is currently fully revising the International Classification of Impairment, Disability and Handicap (ICIDH). The new terms will be impairment, activity and participation).
The 1991 Informal Working Group on Programme Planning gave examples of these levels of prevention for different causes. For noise-induced hearing loss it recommended:
For primary prevention: education, hearing conservation programmes, legislation.
For secondary prevention: change of environment.
For tertiary prevention: hearing aids and rehabilitation.
Hearing loss from non-occupational noise is generally less than in the occupational setting but public awareness of the hazard is low. Nonoccupational strategies for prevention include education on the potentially harmful effects of noise, information on products and devices which emit loud noise, and the proper use of headsets for listening to music and use of ear protectors. Educational programmes should be targeted towards children in schools as well as to health care workers, industrialists, legislators and the general public.
Occupational Strategies include the use of noise surveys to detect hazardous noise levels, engineering and administrative noise controls, education of workers, provision of ear protection, and counselling, and regular followup. Factory owners should be advised on the usefulness of modernisation of their plants to lessen excessive noise exposure. Governments should enact legislation for noise control and hearing conservation, especially in the occupational setting. Regulations must be enforced and programmes monitored.
| History of the World Health Organization's programme for the prevention of deafness and hearing impairment|| |
Activities at the World Health Organisation (WHO) to do with the PREVENTION OF DEAFNESS AND HEARING IMPAIRMENT (PDH) began in the mid-eighties in the rehabilitation unit. A resolution of the 38th World Health Assembly in 1985 stated that much deafness is reversible or remediable and it gave rise the following year to an important report (WHO-PDH, 1986) on Prevention of Deafness and Hearing Impairment. This report tried to quantify the size of the problem and looked at causes, and means of prevention. It identified that the largest needs for the prevention of avoidable hearing loss were in developing countries. Its estimates of numbers were perhaps too low, especially in developing countries, but it significantly raised the profile of the problem world wide. On noise it stated that noise-induced hearing loss is one of the commonest workrelated diseases and that there was no standard occupational reporting system. At the time of this report, the expert advisory panel on Deafness and Hearing Impairment was set up.
In 1991, PDH became affiliated with PREVENTION OF BLINDNESS. A notable event that year was the convening of the Informal Working Group on Programme Planning, held in Geneva in June 1991 (WHOPDH, 1991). This meeting addressed the key problems and tasks in this field and identified noise as one of the major preventable causes of deafness and hearing impairment in adults.
The WHO Regional Offices then became involved, and workshops on PDH were held at the South East Asian Regional Office in Delhi in late 1991, in the Eastern Mediterranean Regional Office in Alexandria in 1992 and 1994, and in the Western Pacific Regional Office in Manila in 1994. The most recent workshop was organised in 1995 by the WHO African Regional Office, together with WHO Headquarters, in Nairobi last year for Anglophone African countries (WHO-PDH, 1995).
In November, 1994 an Informal Consultation on Strategies for Prevention of Hearing Impairment from Ototoxic Drugs was held at WHO Headquarters in Geneva (WHO-DH, 1994).
A seminal event for the cause of Deafness and Hearing Impairment was the adoption in 1995, by the 48th World Health Assembly, of a resolution on the Prevention of Hearing Impairment (WHO-WHA, 1995) [see box 1]. This was a notable event to re-kindle global interest in this problem. The resolution will be of particular importance to show to governments that this problem should be given increased priority in their programme planning.
In January 1997 the First Informal Consultation on Future Programme Developments for the Prevention of Deafness and Hearing Impairment (WHO-PDH, 1997) was held in Geneva. These consultations are held annually to address programme development priorities.
| Current activities of the programme for the prevention of deafness and hearing impairment relating to noiseinduced hearing loss|| |
Major planned activities in this field at WHO comprise:
(a) Global Epidemiology and the Costs of Hearing Impairment.
In this activity, countries are being encouraged, with WHO technical support, to conduct population-based prevalence surveys using a specially developed WHO survey package. (The protocol with data entry and analysis software is available from WHO-PDH for conducting a national survey). Results of surveys will be used in national planning, in the construction of a global database, and ultimately in the determination of the individual and societal costs of hearing impairment and the benefits of prevention.
(b) Strategies for Prevention.
These strategies address important causes of deafness and hearing impairment such as ototoxic drugs and chronic otitis media, and now include noise-induced hearing loss (see section
(c) Development of Primary Ear Care as part of Primary Health Care.
This activity will develop techniques, for use particularly at the primary level, for the prevention of ear disease and hearing impairment.
Many ear diseases and causes of hearing impairment can be prevented by action at the primary level; this applies particularly to noiseinduced hearing loss. Such a programme of Primary Ear Care would incorporate the supporting principles and activities of Primary Health Care (see box). It would include promotive, preventive, and therapeutic measures for ear care to an individual or a community. The development of a primary ear care programme would need to determine the essential ear care to be given at primary level, but it would also require the necessary support to be available from Secondary and Tertiary levels with a system of 2-way referral. All this could be developed within the context of what could be called Public health otology and audiology. A workshop on primary ear care, was recently organised by the University of Cape Town with support from WHO, and the proceedings will be available soon.
(d) National Programmes for Prevention of Deafness and Hearing Impairment.
The main function of WHO-PDH is to encourage and assist countries to devise and implement National Programmes for prevention of deafness and hearing impairment where none exists, or to strengthen an existing programme. Such programmes would be integrated in the national health programme and could include several or all of the elements listed above. One of the first steps would be the convening of a national workshop on prevention which would discuss the results of the national survey, and seek consensus on key topics such as priorities for prevention, guidelines for primary ear care, screening, referral and support facilities, and manpower and training needs. A National Coordinator and Committee would be appointed that would oversee the formulation, implementation and evaluation of the programme.
(e) The WHO-PDH organised a consultation on "The Prevention of Noise-Induced Hearing Loss", in October 1997 in Geneva. 29 Participants attended from 14 countries, including 6 developing countries.
The meeting addressed the problem of noiseinduced hearing loss as a significant cause of hearing impairment in all countries of the world, but especially in developing countries. It focussed on excessive social noise but also reviewed the effects of excessive occupational and environmental noise. The role of noiseinduced hearing loss as a public health problem, and the possibilities for preventing hearing impairment by controlling excessive noise in the context of primary health care were considered.
The participants concluded that exposure to excessive noise is the major avoidable cause of permanent hearing impairment worldwide. In a developed country, exposure to excessive noise is at least partially the cause in more than onethird of those in the population who have hearing impairment. In many countries, NIHL is the most prevalent irreversible industrial disease, and noise is the biggest compensatable occupational hazard. In developing countries, occupational noise and urban, environmental noise are increasing risk factors for hearing impairment. There are a number of new, potentially harmful noise situations. Traffic noise in major urban agglomerations easily reaches dangerous levels, and the same is true for certain toys and leisure activities. Mining and workshops for hammering of metal are still commonly causing hearing loss in developing countries. Exposure to excessive noise is also of concern because it is associated with distressing conditions such as tinnitus.
The meeting made a number of important recommendations. Amongst these were that all countries should establish or strengthen National Programmes for the Prevention of noise-induced hearing loss. These programmes should be integrated with Primary Health Care. It is important to create greater public awareness of the harmful effects of noise on hearing and on the prevention of NIHL through the development of key health messages for dissemination to schools and in health education programmes in the local community.
Occupational noise-induced hearing loss is still a major problem, particularly now in developing countries, where measures to reduce noise sources and introduce legislation and effective hearing conservation should be introduced. Trained personnel to carry out noise surveys and audiometric testing are a major need in developing countries. Other serious sources of noise which do or are likely to produce hearing loss include traffic noise, use of firearms and some leisure pursuits in adults and children.
Recommendations for the reduction of noise from these sources and improving protection from them were set out.
Participants recognised that there is a serious shortage of accurate epidemiological data relating to noise-induced hearing loss throughout the world but particularly in developing countries. The conduct of more prevalence surveys and the collection of longitudinal data plus the development of effective screening methods were recommended. Information on the economic costs of NIHL is also needed to determine its social and economic consequences. Various research priorities were highlighted relating to understanding the mechanisms of noise-induced hearing loss, identification of risk factors, interaction with other ototoxic agents, investigation of possible medications for prevention, and research on technical measures for noise abatement. Greater collaboration is needed, particularly between academic institutions in the developed and developing world to promote research, and between WHO and its member states and relevant NGOs, especially to support prevention at the community level. The report of this meeting can be obtained from the WHO-PDH programme.
(f) Other activities of the PDH Programme in relation to noise-induced hearing loss
- Designation of expert advisers that can be called upon to provide technical guidance will be increased as the programme expands.
- Designation of WHO Collaborating Centres according to a defined strategic plan. This is an important way of linking with acknowledged centres of technical expertise that perform activities relating to different aspects of the programme plan.
- Encouragement of appropriate research. Such research could be of an epidemiological, biological, technological, anthropological and socio-economic nature.
- Development of linkages for information exchange with relevant organisations. These include other WHO programmes, international agencies, governments, academic institutions, professional bodies, teaching and training organisations, NGDOs, donors and, last but not least, organisations of people with listening disabilities.
- human resource development. WHO will encourage the identification of appropriate categories of health workers, the determination of skill and training needs, and the establishment of career structures.
- In relation to all these activities, PDH will seek to disseminate knowledge and promote awareness of the problems, needs and possible solutions in this field.
| Other activities of WHO in relation to noise-induced hearing loss|| |
The Occupational Health Programme (OCH) convened a technical meeting on Evaluation and Control of Noise in the Environment. The report, which is being produced, will include, in relation to noise-induced hearing loss, aspects on noise sources, health effects, measurement & control in the workplace and hearing conservation programmes.
The Urban Environmental Health Programme (UEH), has been involved in the development of Guidelines for Community Noise. Issues addressed include physical aspects of noise, types of environmental noise, effects of noise on humans including noise-induced hearing loss, the societal costs of community noise, measurement of exposure, and evaluation of health risks
| References|| |
|1.||NIH (1990) - Noise and Hearing Loss. NIH Consensus Development Conference Consensus Statement. January 22.24, 1990; 8(1)., NIH, Bethesda, Md, USA. |
|2.||WHO-PDH (1995) - Prevention of Hearing Impairment in Africa: Report of a WHO Workshop, Nairobi, 24-27 October 1995, World Health Organization, WHO/PDH/96.3/AFR/NCD/96.1. |
|3.||WH0 (1986) - Report by the Director General, Prevention of Deafness and Hearing Impairment, World Health Organization, Geneva (March 1986), A39/14 & EB79/10 |
|4.||WHO-PDH (1991) - Report of the Informal Working Group on Prevention of Deafness and Hearing Impairment, Programme Planning. Geneva, 18-21 June 1991, World Health Organization, Geneva (1991), WHO/PDH/91.1. |
|5.||WHO-PDH (1994) - Report of an informal consultation on strategies for prevention of hearing impairment from ototoxic drugs, Geneva, 21-23 November 1994, World Health Organization, Geneva, WHO/PDH/95.2. |
|6.||WHA (1995) - Prevention of Hearing Impairment, Resolution of the 48th World Health Assembly, (12 May 1995), World Health Organization, Geneva, WHA 48.9. |
|7.||WHO-PDH (1997) - Report of the First Informal Consultation on Future Programme Developments for the Prevention of Deafness and Hearing Impairment, World Health Organization, Geneva, 23-24 January 1997, WHO/PDH/97.3. |
Andrew W Smith
Medical Officer, Prevention of Deafness and Hearing Impairment (PDH), World Health Organization, CH-1211 Geneva 27