Noise is defined as “a sound or set of sounds that occurs with no regular harmony”. Everyone perceives noise differently, depending on multiple factors. Noise pollution depends on the characteristics of the sounds emitted (frequency, purity, intensity, abruptness, duration) but also the characteristics of the person subjected to it (individual vulnerability or the existence of additional risk-inducing exposures such as chemicals or drugs).
The adverse effects of high noise levels on hearing are well known. They are mostly observed in the workplace or are related to risk behaviour, such as listening to amplified music without protection. However, noise can have other health effects, known as non-auditory effects, which can appear at lower levels of exposure and are observed in the vicinity of transport or industrial infrastructures, for example.
The health effects of environmental noise are a source of increasing public concern. People cite noise as one of the most common sources of environmental pollution. Furthermore, a growing number of studies have confirmed the harmful effects of noise on health, especially non-auditory effects. Lastly, current regulatory criteria defining exposure to sound are unsuitable for specific sound events, when the objective is to assess the non-auditory aspects of the impact on health associated with transport and industrial infrastructure projects.
It is against this background that ANSES was requested by the Ministries of the Environment and Health to propose indicators enabling decision-makers to give greater consideration to the health effects of intermittent noise events. The request specifically concerned the quantification of non-auditory health effects in health impact assessments for transport and industrial infrastructure projects. In response, the Agency proposes, in the Opinion published today, a method for assessing the non-auditory health impact of noise.
To carry out this work, the Agency set up a multidisciplinary working group of experts (acousticians, epidemiologists, chronobiologists, specialists in the human and social sciences, etc.), overseen by the Expert Committee on physical agents.
Based on a review of current knowledge, the working group determined a number of non-auditory effects, with the main one being sleep disturbance. Loss of sleep or poor quality sleep can have repercussions on health and cognitive performance the following day: efficiency, learning capacity and attention are all reduced. The other non-auditory health effects may be the result of direct exposure to noise or be related to the consequences of disturbed sleep: cardiovascular response (increased risk of high blood pressure, ischemic disorders in adults). The degree of these effects depends on the level and duration of the exposure to noise, and on the sensitivity of the individuals exposed, whose reactions to given levels of environmental noise may differ significantly. Several studies conclude that it is difficult to establish a precise threshold between acceptable and undesirable levels and emphasise the variable nature of the relationship between indicators of discomfort and the physical intensity of sound. Apart from discomfort, other psycho-sociological and behavioural effects have been described: effects on attitudes and social behaviour, on performance and auto-medication. Noise generated by transport has socio-economic effects on localities, including downgrading and reducing the desirability of residential areas, with the unequal geographical distribution of noise pollution particularly affecting those in lower income brackets.
Moreover, the experts specifically mentioned the following:
- chronic discomfort related to noise, a continual cause of stress, influences the onset of long-term adverse effects on health;
- the mechanisms of action of noise, especially regarding the long-term non-auditory effects related to prolonged exposure to noise, are not fully understood;
- the dose-response relationship is poorly documented and is based mainly on acoustic factors (mean energy indices) that are unsuitable for assessing intermittent noise events. There is currently no consensus concerning the robustness of these dose-response curves.
The experts emphasised the complexity of the interactions between a variety of parameters involved in the relationship between noise and health, which can be physical, physiological, cognitive and socio-economic. They consider that in the current state of knowledge it is not possible to establish indicators providing a satisfactory response to the issue raised by the authors of the Request.
In agreement with the Ministries that issued the Request, the goals of the expert assessment were modified in order to establish a method for assessing non-auditory health effects.
On the basis of this expert assessment, ANSES proposes a method for assessing the non-auditory health effects of environmental noise. Four types of effects were selected, including short-term effects (disturbed sleep and noise-related discomfort) medium- to long-term effects (learning difficulties among schoolchildren) and cardiovascular effects (myocardial infarction). The method is intended for use at local level in the documentation of situations involving exposure to environmental noise, before and after the implementation of infrastructure development projects. It is intended for inclusion in the process of mediation/consultation for examining applications for development projects concerning rail, road or industrial infrastructures.
The Agency proposes to assist with the implementation of this method via pilot projects.
In addition, the Agency recommends that more detailed health impact assessments be conducted for the population groups most exposed to non-acoustic factors identified as aggravating the health effects of noise (e.g. polluted outdoor air, etc.). It also emphasises the need to update the regulatory framework to take these risk factors into account.
Considering the current gaps in scientific knowledge regarding the issue, ANSES recommends that interdisciplinary research work be undertaken on:
- the mechanisms of action of noise for long-term effects;
- the relevant characteristics of the risk (latency, level of risk, duration, period of exposure and exposure-response relationship).
Considering also the need to rationalise research efforts, ANSES proposes that a body be created whose purpose would be to catalogue and centralise, on a national level, all publications concerning the issue of noise-related health risks.