What causes air pollution?

Air pollution is a mixture of gases and particles that have been released into the atmosphere by human activities. Generally, air pollution comes from the burning of fossil fuels such as coal, oil, natural gas, petrol or diesel.

This is not a new phenomenon for cities. London has suffered from air pollution since the beginning of the Industrial Revolution in the 18^th century. Industrial processes and domestic heating were the main contributors to air pollution in London until the 1970s.

Domestic, commercial and industrial pollution still exist, but now, the biggest cause of air pollution in Tower Hamlets is traffic. Pollutants from the exhausts of cars, lorries and other vehicles are poisoning the air.

What are the pollutants?

There are seven main pollutants in our air: nitrogen dioxide (NO₂), particulates (mainly PM₁₀), carbon monoxide (CO), sulphur dioxide (SO₂), ozone (O₃), benzene and lead.

Of these, nitrogen dioxide and particulates affect our health the most. The other five pollutants are now at levels that meet EU requirements. This means that their presence in the air is low enough in Tower Hamlets to make a minimal impact on health.

Nitrogen dioxide (NO₂)

Nitrogen dioxide is one of the family of chemicals known as nitrogen oxides, which are formed from the reaction of nitrogen (N) and oxygen (O) during combustion.

Nitrogen dioxide emissions contribute to acid rain, which can cause damage to trees, buildings (stonework), lakes and rivers. Nitrogen dioxide can combine with different vehicle exhaust gases to form photochemical smog and ground level ozone, all of which affect people's health. You can see the smog on hot days in Tower Hamlets, when pollution levels are particularly high.

Particulates (PM₁₀)

Particulates are tiny particles of dust, soot and gases that are released into the air by natural and man-made activities. When you breathe them in, they settle in the lower parts of the lung where they can cause serious health problems.

There are natural sources of particulates, such as wind-blown dust and soil, sea spray and pollens. However, in Tower Hamlets, the largest source of particulates is road traffic. ‘PM₁₀’ is used to describe particulates which are harmful because they are too small for you nose, throat and trachea to prevent you from breathing them into your body.

Particulates with an aerodynamic diameter of 10 microns or less (PM₁₀) are small enough to get into your lungs and settle there. Those with a diameter of 2.5 microns or less (PM_2.5) can get into your bloodstream.