Why is this issue important?
Air pollution is a significant health issue for Southampton City, disproportionately affecting our most vulnerable members of society. European legislation sets out a number of requirements to control outdoor levels of pollutants. Local Authorities have a responsibility under Local Air Quality Management legislation to review air quality. Southampton currently has ten Air Quality Management Areas (AQMAs) declared, each one as a result of the annual mean for nitrogen dioxide (NO2) exceeding the limit value of 40 μg/m3.
What is air pollution and what is its effect on health?
In the UK, air pollutants are mainly products of motor vehicle traffic combustion especially from diesel vehicles. Pollutants known to have effects on health are particles, sulphur dioxide, oxides of nitrogen, carbon monoxide and ozone. In a good state of health, short term exposure to moderate levels of air pollution is unlikely to have any serious short term effects. Short term exposure to high levels of air pollutants can cause a range of adverse effects such as exacerbations of asthma, effects on lung function and consequent increases in hospital admissions for respiratory and cardiovascular conditions.
Long term exposure to air pollution does increase the risk of deaths from cardiovascular and respiratory conditions, including lung cancer and existing lung and heart conditions. Chronic effects can be triggers of new disease, worsen severity of disease through increase in symptoms or accelerate progression of disease over time. Children, the elderly and people with lung or heart conditions are more susceptible to the health effects of air pollution. People with coronary artery disease are at greater risk of being affected by air pollution, especially particles, than people without such disease. Coronary artery disease, which can remain undetected, is common in older people.
Evidence of the long term effects of air pollution are most closely associated with levels of fine particulate matter (PM2.5). Just 18 µg/m3 PM2.5 could be responsible for an average loss of life expectancy from birth of around 2-20 months (average of 7-8 months). This compares to an estimate of around 7 years if all the population were smokers (Department of Health, 2001). There is no evidence for a threshold below which health effects would not be expected. For NO2, studies have shown that both day to day variations and long term exposure to NO2 are associated with mortality and morbidity.
The public health benefit of a 1µg/m3 reduction in national average PM2.5 concentration is estimated as being an increase in average life-expectancy of around 20 days (range 3 to 40 days). It is likely that, compared with factors affecting individuals such as smoking, diet and lack of exercise, air pollution has a health impact similar to that of passive smoking. The Department of Transport estimate that health impact from motorised transport for the UK is estimated at £10 billion. The cost to Southampton is estimated at £50 million.
What is the situation in our City?
Modelled estimates of mortality attributable to long term exposure to air pollution i.e. annual average concentrations of fine particulate matter (PM2.5) have been published by Public Health England. These suggests that 6.2% of deaths in 2010 were attributable to air pollution, with long-term exposure contributing 110 deaths among those aged 25 years and over and 1,280 life years lost.
Since 2010, Southampton’s estimated fraction of mortality attributable to particulate air pollution has declined, from 6.2% to 5.7%. This is in line with a national decrease. 2012 figures show that Southampton’s fraction of mortality attributable to particulate air pollution is worse than both the England and South East average of 5.1%. Local cities are also rated better than Southampton, for example Portsmouth 5.3%, Brighton and Hove 5.0%, Oxfordshire 5.1%, Bristol 5.2% and Bournemouth 4.1%.
Mapping of Chronic Obstructive Pulmonary Disease hospital admissions, asthma hospital admissions and cardiovascular hospital admissions against air quality management areas in Southampton City show close correlation. Those areas in Southampton with the highest pollution levels are also areas where hospital admissions for these indications are highest. These are also areas of significant deprivation and where we would expect health outcomes to be worse. As previously described, air pollution exacerbates pre-existing conditions. Mapping of Chronic Obstructive Pulmonary Disease and asthma prevalence against air quality management areas also shows some degree of correlation (see figures 1 & 2). Opportunities to monitor air quality in areas where respiratory disease prevalence is high would be of benefit.