When the Great Smog hit London in 1952 we knew little about the many health effects of air pollution. Over the last 60 years, however, and particularly during the past decade, our understanding of its impact on human health has improved considerably. A report by the Government’s Committee on the Medical Effects
of Air Pollution estimated that 29,000 deaths in the UK in 2008 could be attributed to long-term exposure to ‘invisible’ airborne particles.1
This compares with 4075 deaths due to short-term
exposure to ‘visible’ air pollution in London, in December 1952. Around some of the UK’s busiest streets, levels of nitrogen dioxide
(NO2) – the only substance regulated within the gas component of ambient (outside) air pollution – are more than twice the legal limits. Indeed, only eight of 43 zones in the UK met the EU’s 2010 deadline for compliance with limits for NO2, set back in 1999.2
only smoking causes more premature deaths than air pollution. Ambient air quality (AAQ) assessment typically focuses on
particle-mass concentrations and gases, although there is increasing concern among scientists about the health impact of higher particle- number concentrations and surface area of smaller particles. The most common forms of indoor air pollution include: fine combustion particles from traffic and power stations (PM2.5);
volcanic dust; bio-aerosols and pathogens, such as pollen, bacteria, viruses and fungal spores; environmental tobacco smoke (ETS); asbestos; and silica dust. Molecular pollutants, such as gases and vapours, include: carbon monoxide; oxides of nitrogen (NOx) and sulphur; ozone; radon; and volatile organic compounds (VOCs).
Consideration should also be given to carbon dioxide (CO2) levels, temperature, relative humidity and ventilation rates. Effects
A significant proportion of air pollution found indoors originates from outside. IAQ can be further affected by: tobacco smoke from indoor smoking (nowadays, just in homes rather than workplaces, assuming employers comply with the smoking ban); combustion (such as gas cooking or candles); water systems, leaks and condensation; and substances emitted from some building materials, furnishings and cleaning agents. Indoor concentrations of some pollutants can also be much higher than those outdoors. In addition, European citizens spend, on average, more than 90 per cent of their time indoors. So, in a large city, domestic gas combustion (for example, from cooking and heating) may, in turn, contribute more than 20 per cent to ambient air emissions of NOx.3
As a consequence of the many sources of pollution in buildings, air quality indoors can often be worse than outdoors, says Simon Birkett, who considers the evidence, the impact of poor air quality on workers and visitors, and what can be done to address the problem.