Health and exposure to pollution

Air pollution refers to substances in the air that harm human health, welfare, plant or animal life. Most pollution in London is caused by road transport and domestic and commercial heating systems.

The UK Air Quality Standards Regulations 2010 sets standards for a number of pollutants than can harm human health and the environment. These are based on EU limit values and include:

• sulphur dioxide (SO2)
• nitrogen dioxide (NO2)
• nitrogen oxides (NOx)
• particulate matter (PM10 and PM2.5)
• lead
• benzene
• carbon monoxide (CO)
• benzo(a)pyrene
• ozone (O3)

In London, most of these pollutants are not at levels that affect human health. You can read more about air quality and health at World Health Organisation (WHO) and Committee on the Medical Effects of Air Pollutants.

The two pollutants of most concern in London are:

Particulate matter (PM)

Particulate pollution can harm our heart and lungs - it is linked to asthma and death. Research shows that particles with a diameter of ten microns and smaller (PM10) can be inhaled deep into the lungs as smaller particles can penetrate deeper. PM2.5 can have a particularly bad impact on health.

Nitrogen dioxide (NO2)

At high concentrations, NO2 can inflame the airways and long-term exposure can affect lung function and breathing - it can also worsen asthma.

In 2008, we estimated that 4,300 premature deaths in London were due to long-term exposure to small particles.

In 2015 we published an updated study by King’s College London which included the health impacts associated with the air pollutant nitrogen dioxide (NO2) in London for the first time.

This new study shows that in 2010 there was the equivalent of up to 5,900 premature deaths across London associated with NO2 long term exposure.

At the same time the premature deaths associated with long-term exposure to PM2.5 were recalculated. The equivalent number of PM2.5 premature deaths has decreased from 4,300 (in 2008 based on 2006 concentrations) to 3,500 (in 2010).

The PM2.5 and NO2 figures can be combined to create a total figure of up to 9,400 equivalent premature deaths in 2010.

In using the 9,400 figure it is important to note that the numbers of equivalent premature deaths have not increased, we have just never calculated NO2 health impacts before. In fact, PM2.5 figures have decreased compared with the previous report published in 2010. The NO2 health effects have also been calculated using new methods which mean they are subject to greater uncertainty than the PM2.5 health effects.

Updated September 2017 – Please note that these calculations are currently being remodelled with an updated figure expected in 2018. King’s College has advised that we change the 9000 figure to “thousands” in the interim.

Other key findings from the study include:

• in 2010 nearly half the health effects of long term exposure to air pollution were caused by pollution from outside London, as well as 75% of cardiovascular hospital admissions associated with PM2.5
• reductions in pollutant levels between 2010 and 2020 will result in nearly 4 million life years being saved. This excludes the expected impact of the Ultra Low Emission Zone, which will lead to significant reduction in the number of people living in areas of poor air quality (where levels of NO2 exceed legal limits) – by 72 per cent in central London and 54 per cent London wide
• there have also been average reductions in NO2 levels at roadside sites of more than 12 per cent (with weather effects removed)
• the report also includes a 2010 borough breakdown highlighting the estimated number of attributable deaths associated with air pollution in each area based on the number of the local population