6: Can Effect-Based Assessment Methods be Established?
The aim of this work was to advise DETR whether it is possible to derive robust health effect based noise standards. We have looked at the issues and conclude that it is not possible at this time to establish health effect based assessment methods. This is because:
- We need a clearer understanding of the definition and framework within which we can judge the overall impact on health in order to develop standards that are useful to the decision maker and general public.
- Although there is evidence to support the existence of a cause-effect relationship for annoyance, and some evidence for activity interferences such as sleep disturbance and speech interference, we do not have convincing evidence whether other measurable effects exist at all at typical levels of exposure to community noise. In addition we do not know what proportion of the population might be affected and to what extent.
- Although there have been numerous scientific studies on the health effects of noise, we cannot at present define robust exposure-response relationships for all the potential effects. Existing dose-response relationships are confounded by a number of variables which serve to scatter the data points around these cause-effect curves. These include non acoustical exposure variables which can have major effects on attitudes and opinions.
- The scientific evidence suggests threshold levels below which no effects are expected. Again, since these are based on fragmentary and unconvincing evidence, the levels suggested cannot be taken as definitive at this time.
- There are uncertainties in assessing the overall impact of noise on health. These relate to the treatment of more than one effect, the role of modifiers, the cumulative exposure of different time periods, the handling of vulnerable or susceptible groups, and the role of other risk factors in assessing conditions of multi-factorial origin. These need to be better understood before effect-based assessment methods can be established.
- Practical noise criteria are a balance between the desirable and affordable. The desirable relates to the thresholds suggested by the scientific evidence below which no effect is expected. The affordable involves weighing the costs and benefits in monetary and social costs. Effect-based noise assessment methods and criteria must therefore take into account this compromise which may be different in different situations.
- Existing standards and regulations usually take the results of primary research into account to some extent, but social, economic and political considerations are often at least as important. Many existing noise limits also depend on unknown historical factors. It is very important to be clear about the role played by these social, economic, political and historic factors in the aetiology of current standards and regulations in the future development of new effect-based standards. It must also be taken into account that social and political interpretations can change, even if the underlying noise exposure response relationships remain constant. In addition, the underlying noise exposure response relationships might also change as public expectations develop.
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Published 12 September 2000
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