Estimating exposure to excessive noise in cities

The 2002 Environmental Noise Directive seeks to provide a uniform basis for measuring and addressing noise pollution, one of the most important urban environmental issues for the EU. New research has assessed city-dwellers' exposure to noise and proposes traffic management strategies to reduce harmful levels. Clear evidence is growing for wide-ranging negative health effects of noise pollution, including emotional responses such as anger, anxiety and depression, learning difficulties, motivation and attention problems (particularly in children) and heart disease. All may be related to sleep disturbance, which has measurable psychological and physiological effects. In order to design effective noise reduction measures, it is important to understand exposure to noise pollution.

The study centred on one square kilometre in the centre of Dublin, Ireland. This is a relatively quiet area surrounded by roads with very heavy traffic, believed to be representative of urban areas across the EU. The EU Harmonoise2 model was used to predict road traffic noise. This model is expected to become the standard EU model by 2012. Traffic was characterised as light/medium/heavy vehicles, as obtained from recorded traffic flow data made available by Dublin city council. Geographic Information System (GIS) data, which provides a special map of the area including details of building height and road profiles, were then used to map populations and noise levels at different times.

Of particular concern, the study found that 90 per cent of residents in central Dublin were affected by night-time noise exceeding World Health Organisation guidelines3. Furthermore, 53 per cent of workers and 28 per cent of residents exceeded daytime noise guidelines.

WHO guideline levels for daytime exposure to noise are 70 decibels (dB), compared with 45dB for night-time levels. The daytime population of the area studied, including workers, is around 10 times greater than the overnight population. Therefore although the proportion of the population exceeding the guidelines is higher at night, excessive noise affects a greater number of people during the day.

The researchers also modelled the effects of simple traffic management measures, such as diverting traffic from residential areas at night. They found that the number of residents exposed to high levels of noise (60-70 dB) at night could be reduced considerably (from an estimated 3500 residents to around 2700). They suggest that night time noise reduction measures should focus on preventing traffic from travelling along inner city links where there are high numbers of residents. Good urban design with coherent traffic management plans could therefore have positive health benefits, even with little or no change to existing infrastructure or environment.

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