5: Guide to the Interpretation of the WHO Guidelines
5.1: Introduction
As part of this project, DETR requested an interpretation of the recent WHO guidelines, included in this section. In 1980, the World Health Organisation published an Environmental Health Criteria report dealing with noise (WHO 80). This document introduced what have since become generally known as the 'WHO noise limits'. These WHO noise limits have been widely used in setting standards and criteria in a number of areas, although they have no official status. On the front cover of the report itself, it is clearly stated that; 'This report contains the collective views of an international group of experts and does not necessarily represent the decisions or the stated policy of either the World Health Organisation or the United Nations Environment Programme'.
More recently, Berglund and Lindvall published an updated Community Noise document (BERGLUND 95) for the World Health Organisation setting out revised noise limit guidelines. Certain criteria have been revised in the light of accumulated scientific knowledge since the publication of the original Environmental Health Criteria document in 1980. It is clearly acknowledged in the Foreword to the new document; 'Thus, although the document is the amalgamated result of the work of a large number of persons, the complex and extended work process makes it necessary to declare that the editors are solely responsible for the present text of the document'. The guideline values contained therein have not been adopted by the WHO or by any other official body, although this does not of course have any effect on their underlying scientific validity as determined from the available research data.
The first draft of the 1980 Environmental Health Criteria document was prepared by a study group of international experts that met in Geneva in late 1973. The WHO secretariat prepared a second draft taking into account comments received from national focal points for the WHO Environmental Health Criteria programme. The draft produced by the secretariat was reviewed and revised by a WHO Task Group which met in Brussels in early 1977. A much smaller group of experts then assisted the Secretariat to publish the document in its final form in 1980. Every effort was made to review all pertinent data and information available up to 1978, although a note at the front of the document acknowledges the possibility of errors and omissions and requests notification to the Secretariat if any errors are found.
The first draft of the updated 1995 document was initially prepared by Berglund and Lindvall on behalf of the WHO and the Nordic Noise Group of the Nordic Council of Ministers, as based on reviews of community noise effects published since the 1980 document. This draft was reviewed by a WHO Task Force of invited international experts at a meeting held in Dusseldorf in late 1992. A series of revised guideline values were agreed upon in consensus at the Dusseldorf meeting and have been included in the updated 1995 document as a separate chapter (Chapter 11). Berglund and Lindvall then prepared an external review draft for wider comments incorporating some additional contributions from members of the Dusseldorf Task Force. This draft was widely circulated in 1993. Many comments from different experts around the world were submitted to the editors. The final published document was compiled by Berglund and Lindvall with some assistance from the WHO secretariat. The editors alone decided how to deal with particular points where conflicting comments had been received. This means that parts at least of the updated document include an element of personal interpretation by the editors.
5.2: Guideline Values
The main premise underlying the two WHO-inspired noise guideline documents (1980 and 1995) is that excessive exposure to community and environmental noise damages health. It is well known that excessive noise exposure in an industrial context can damage hearing, but the true effects of community and environmental noise in a residential context are more controversial. The various WHO guideline values for the range of noise effects are given in table 5. These are included in our earlier table 3 to some extent as BERGLUND 96.
It is immediately apparent when comparing the 1980 and 1995 guideline values that there is a lack of consistency in the definitions of the different effects of noise considered, and the units in which the guideline values are specified. For example, the 1980 guidelines for steady background noise levels to support 100% speech intelligibility were given as 45 LAeq, whereas the equivalent guideline values for 1995 were given as 35 dBA. The true levels of speech interference will not have changed, and although it might appear that the criterion value to avoid speech interference has been tightened by 10 dB in 15 years, in fact, both the way that the effects are measured and the way that the noise exposure is measured have changed and this makes it difficult to compare the two sets of guideline values.
Table 5: The WHO guideline values
Effect to be Effect criterion 1980 1995 avoided speech interference 100% intelligibility 45 LAeq 35 dBA reasonable 45 dBA intelligibility loud speech 55 dBA understood noise induced negligible risk 75 LAeq,8hrs 75 LAeq,8hrs hearing loss increasing risk 140 dB 130-150 dB(peak) sleep disturbance electrophysiological 35 LAeq 30 LAeq effects 45 LAmax cardiovascular more research more research disease needed needed performance effects cognitive tasks no specific criteria startle effects no specific criteria reading skills in no specific children criteria thresholds of moderate annoyance 50 LAeq reported annoyance serious annoyance 50 LAeq 55 LAeq social behaviour reduced helping 80 dBA behaviourTwo critical areas are sleep disturbance and reported annoyance. The 1980 guideline value to avoid 'interference with the restorative process of sleep' by continuous noise was specified as 35 LAeq as measured in the bedroom. The 1995 guideline value for continuous noise 'if negative effects on sleep are to be avoided' is specified as 30 LAeq, some 5 dB lower than in 1980. An additional LAmax guideline of 45 dBA is specified in the 1995 document to avoid sleep disturbance caused by separate noise events. These changes represent a more conservative approach by the editors of the updated 1995 document rather than any fundamental changes in human sensitivity to noise whilst asleep.
For reported annoyance, the 1980 guideline value was 'that daytime noise levels of less than 50 dBA Leq cause little or no serious annoyance in the community'. 'Taking into account other factors such as transport needs, ........., daytime noise limits in the region of 55 dBA Leq might be considered as a general environmental health goal for outdoor noise levels in residential areas'. The 1995 document states that 'the threshold of annoyance for steady-state, continuous noise is around 50 dB LAeq. Few people are seriously annoyed during the day time at noise levels below around 55 dB LAeq'. For reported annoyance, close comparison of the precise specifications given in the 1980 and 1995 documents suggests that the guideline values have actually been relaxed. In 1980, 55 LAeq was suggested as a general environmental health goal, whereas in 1995, 55 LAeq is being suggested as the threshold value below which few people are seriously annoyed.
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Published 12 September 2000
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