Acid rain

Rain that is mixed with nitric and sulphuric acid. Acid rain is created by emissions from the burning of fossil fuels. The acid can damage plants and buildings.

Air

The air that you breathe is a mixture of gases. Air comprises about 78 percent nitrogen, 21 percent oxygen, and less than 1 percent of carbon dioxide, argon, other gases, and water vapor.

Air monitoring

To find out how many pollutants are in the atmosphere, the air quality is sampled and tested. In Tower Hamlets, there are three air monitoring stations: Poplar, Mile End Road , Bethnal Green Library.

Alternative fuel

To reduce our dependence on petrol and diesel for cars, scientists have developed fuels that are cleaner and reduce emissions. These alternative fuels include methanol, ethanol, natural gas, and liquid petroleum gas. In addition, electric and hydrogen power have been developed to power vehicles. There are very few vehicles on the road that use these alternatives, but it is likely that they will become more common in future. Alternative fuels are not necessarily from renewable energy sources, but they are less polluting than more common fuels such as petrol and diesel.

Benzene

Benzene is one of a group of chemicals known as Volatile Organic Compounds (VOCs), all of which contribute to the formation of ground level ozone. In addition, certain VOCs, such as benzene and 1,3-Butadiene, are known to cause cancer. Benzene in the atmosphere either comes from the combustion or evaporation of petrol. Levels are therefore highest close to busy roads or near petrol filling stations. Long-term exposure to high levels of benzene and 1,3-Butadiene has been linked to leukaemia and cancer.

Carbon dioxide (CO₂)

A colourless, odourless gas that occurs naturally in the Earth's atmosphere. It also occurs unnaturally: significant quantities are created by fossil fuel combustion and deforestation (the cutting down of trees on a huge scale). Carbon dioxide is a greenhouse gas, and therefore contributes to global warming.

Carbon monoxide (CO)

Carbon monoxide is a colourless, odourless and tasteless gas that is produced in the process of combustion (eg- vehicle engines and boilers). It is the most dangerous of all the pollutant gases and, in very high concentrations, it can cause death. Once emitted into the atmosphere carbon monoxide is slowly oxidised to carbon dioxide, a greenhouse gas. Over 80% of carbon monoxide in our cities is created by cars and other vehicles.

Fossil fuel

Fossil fuels were formed from decomposed animal and plant remains millions of years ago. The fuels include oil, coal and natural gas, which are used to create energy for everyday activities, such as running cars and heating and lighting homes. They have been used so much since the start of the Industrial Revolution that there is concern that resources are running low. Burning fossil fuels creates air pollution, so it’s important to find alternatives. See renewable energy.

Lead

The main source of lead in the atmosphere is the combustion of lead-containing petrol. However, since leaded petrol has been phased out across Europe, lead levels have fallen dramatically and lead monitoring is no longer necessary in most parts of the country.

Nitrogen dioxide (NO₂)

Nitrogen dioxide is one of the family of chemicals known as nitrogen oxides, 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, which also affect people's health.

Ozone (O₃)

Ozone is a highly reactive oxidising agent. At ground level, ozone is considered a pollutant. Ground level ozone is formed indirectly by the reaction of sunlight and nitrogen dioxide and the rate of production depends on the concentrations of the reactive compounds and the intensity of sunlight. Volatile Organic Compounds (see Benzene below) contribute substantially to the atmospheric formation of ozone.

Particulates (PM₁₀)

Particulates are very small particles of dust and soot that are released into the air by natural and man-made activities. They generally cannot be seen with the naked eye, and are so small that they can be breathed in and settle in the lower parts of the lung where they can cause more serious health problems. Natural sources of particulates include wind blown dust and soil, sea spray and pollens. However, in London the largest source of particulates is road traffic, with lorries and diesel vehicles being the worst polluters. The notation ‘PM₁₀’ refers to particulate matter with an aerodynamic diameter of 10 microns or less.

Renewable energy

This is energy that cannot be used up. They include sunshine, water flow, wind and vegetation and geothermal energy. Other sources of renewable energy are combustible materials, such as landfill gas, biomass, and municipal solid waste, although these are likely to have more impact on our air quality than entirely natural sources such as wind energy. By comparison to renewable energy, fossil fuels, which were created millions of years ago, have been used exhaustively over the past two hundred years, and are in danger of running out.

Sulphur dioxide (SO₂)

Sulphur dioxide is the pollutant primarily associated with acid rain. Gaseous at normal temperature and pressure it dissolves in water and readily oxidises to sulphuric acid. Levels of SO₂ have reduced over recent years as coal has been phased out as a fuel for homes and factories. It is one of the main pollutants that led to the infamous ‘London smogs’ in the 1950s and led to the introduction of legislation governing atmospheric pollution (1956 Clean Air Act).