Abstract: Considering the scientific evidence on the thresholds of night noise exposure indicated by Lnight,outside as defined in the Environmental Noise Directive (2002/49/EC), an Lnight,outside of 40 dB should be the target of the night noise guideline (NNG) to protect the public, including the most vulnerable groups such as children, the chronically ill and the elderly. Lnight,outside value of 55 dB is recommended as an interim target for the countries where the NNG cannot be achieved in the short term for various reasons, and where policy-makers choose to adopt a stepwise approach. These guidelines are applicable to the Member States of the European Region, and may be considered as an extension to, as well as an update of, the previous WHO Guidelines for community noise (1999).
Foreword: WHO defines health as a state of complete physical, mental and social well-being and not merely the absence of disease or infirmity, and recognizes the enjoyment of the highest attainable standard of health as one of the fundamental rights of every human being. Environmental noise is a threat to public health, having negative impacts on human health and well-being. In order to support the efforts of the Member States in protecting the population´s health from the harmful levels of noise, WHO issued Guidelines for community noise in 1999, which includes guideline values for community noise in various settings based on the scientific evidence available. The evidence on health impacts of night noise has been accumulated since then.
NOISE INDICATORS: From the scientific point of view the best criterion for choosing a noise indicator is its
ability to predict an effect. Therefore, for different health end points, different indicators could be chosen. Long-term effects such as cardiovascular disorders are more correlated with indicators summarizing the acoustic situation over a long time period, such as yearly average of night noise level outside at the facade (Lnight,outside), while instantaneous effects such as sleep disturbance are better with the maximum level per event (LAmax), such as passage of a lorry, aeroplane or train. From a practical point of view, indicators should be easy to explain to the public so that they can be understood intuitively. Indicators should be consistent with existing practices in the legislation to enable quick and easy application and enforcement. Lnight,outside, adopted by the END, is an indicator of choice for both scientific and practical use. Among currently used indicators for regulatory purposes, LAeq (Aweighted equivalent sound pressure level) and LAmax are useful to predict short-term or instantaneous health effects.
NOISE, SLEEP AND HEALTH: There is plenty of evidence that sleep is a biological necessity, and disturbed sleep is associated with a number of health problems. Studies of sleep disturbance in children and in shift workers clearly show the adverse effects. Noise disturbs sleep by a number of direct and indirect pathways. Even at very low levels physiological reactions (increase in heart rate, body movements and arousals) can be reliably measured. Also, it was shown that awakening reactions are relatively rare, occurring at a much higher level than the physiological reactions.
Table 1 Summary of effects and threshold levels for effects where sufficient evidence is available
|Biological effects||Change in cardiovascular activity||*||*|
|Motility, onset of motility||LAmax,inside||32|
|Changes in duration of various stages of sleep, in sleep structure and fragmentation of sleep||LAmax,inside||35|
|Sleep quality||Waking up in the night and/or too early in the morning||LAmax,inside||42|
|Prolongation of the sleep inception period, difficulty getting to sleep||*||*|
|Sleep fragmentation, reduced sleeping time||*||*|
|Increased average motility when sleeping||Lnight,outside||42|
|Well-being||Self-reported sleep disturbance||Lnight,outside||42|
|Use of somnifacient drugs and sedatives||Lnight,outside||40|
|Medical conditions||Environmental insomnia**||Lnight,outside||42|
*Although the effect has been shown to occur or a plausible biological pathway could be constructed, indicators or threshold levels could not be determined.
**Note that “environmental insomnia” is the result of diagnosis by a medical professional whilst “self-reported sleep disturbance” is essentially the same, but reported in the context of a social survey. Number of questions and exact wording may differ.
RECOMMENDATIONS FOR HEALTH PROTECTION
Based on the systematic review of evidence produced by epidemiological and experimental studies, the relationship between night noise exposure and health effects can be summarized as below. (Table 3) Below the level of 30 dB Lnight,outside, no effects on sleep are observed except for a slight increase in the frequency of body movements during sleep due to night noise. There is no sufficient evidence that the biological effects observed at the level below 40 dB Lnight,outside are harmful to health. However, adverse health effects are observed at the level above 40 dB Lnight,outside, such as self-reported sleep disturbance, environmental insomnia, and increased use of somnifacient drugs and sedatives.
Table 3 Effects of different levels of night noise on the population’s health
|Average night noise level over a year, Lnight,outside||Health effects observed in the population|
|Up to 30 dB||Although individual sensitivities and circumstances may differ, it appears that up to this level no substantial biological effects are observed. Lnight,outside of 30 dB is equivalent to the no observed effect level (NOEL) for night noise.|
|30 to 40 dB||A number of effects on sleep are observed from this range: body movements, awakening, self-reported sleep disturbance, arousals. The intensity of the effect depends on the nature of the source and the number of events. Vulnerable groups (for example children, the chronically ill and the elderly) are more susceptible. However, even in the worst cases the effects seem modest. Lnight,outside of 40 dB is equivalent to the lowest observed adverse effect level (LOAEL) for night noise.|
|40 to 55 dB||Adverse health effects are observed among the exposed population. Many people have to adapt their lives to copewith the noise at night. Vulnerable groups are more severely affected.|
|Above 55 dB||The situation is considered increasingly dangerous for public health. Adverse health effects occur frequently, a sizeable proportion of the population is highly annoyed and sleep-disturbed. There is evidence that the risk of cardiovascular disease increases.|
Download original document: “Night Noise Guidelines for Europe”
Also see: “Burden of disease from environmental noise” (2011)
This article is the work of the author(s) indicated. Any opinions expressed in it are not necessarily those of National Wind Watch.
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