Adverse effects of community noise as a public health issue
Too much noise disturbs sleep, as well known. The number of persons affected by community noise is estimated to be huge. This paper summarizes the recommendation by WHO (1999) and the following international documents, and introduce new data and debate. First, we should choose noise descriptors to study and to regulate noise induced sleeplessness taking account of (1) whether we want to focus on continuous noise or intermittent noise, and (2) whether we want to focus on noise prediction or ecological measurement. LAeq (A weighted sound equivalent level) at sleep period well predicts sleep disturbance in general. Since intermittent noise is more likely to disturb sleep than continuous noise, even if their LAeq is the same, LAmax and LAE are also used. Second, we should determine sleep descriptors such as EEG, actigraphy, and questionnaires. The descriptors should be chosen, in consideration of burdens to subjects and time scale that should be matched with noise assessment. Based on the dose response relationship between community noise and sleep disturbance, WHO (1999) recommended that indoor sound level should be LAeq of 35 dB or below for the general population from the aspect of health sciences. WHO Regional Office for Europe (2004) however, proposed much more strict guidelines, taking the recent studies on community noise and cardiovascular diseases in the general population. Most of the data were, however, cross sectionally obtained, and causality cannot be determined. As a result, intensive debate emerged whether or not the reported effects are meaningful and all the effects are impermissible, reflecting the difference between European view of health and US pragmatic position. On the other hand, effects of ultra low frequency sound from wind turbine plants on sleep and health seem negligible, although audible noise from wind turbine can disturb sleep among residents. Individual difference in sensitivity to noise and effects of daytime noise on night/shift workers should be further investigated. If they can be clarified, this should be systematically reflected to the exposure assessment.