Put simply because clean air is needed for the sake of our health and the health of our environment.

	Sheffield on 23/11/05 at about 11.00AM Nitrogen dioxide emissions in Sheffield, Barnsley, Rotherham and Doncaster were recorded at higher levels than normal during November, mainly due to the calm weather, although increased car use at this time of year was also a factor. On this day in Sheffield, levels reached 240 micrograms of nitrogen dioxide per cubic meter of air compared with normal levels of about 30 - 40 micrograms. Cold weather conditions usually lead to a rise in vehicle use, but people can take positive steps towards reducing harmful emissions by using alternative travel options, such as public transport, walking, or cycling.

Urban air pollution is certainly not a new problem. Back in the days of the Middle Ages the use of coal in cities such as London was beginning to escalate. By the end of the 16th century the problems of urban air pollution and peoples health were well documented.

The Industrial Revolution in the 18th and 19th centuries was based on the use of coal. Industries in our area were the reasons why the urban areas of South Yorkshire appeared and grew. The burning of coal in homes and by industry caused urban air pollution levels to reach often devastating levels. During foggy conditions, pollution levels escalated and urban smogs (smoke and fog) were formed. These smogs often brought Sheffield to a halt, disrupting traffic but more dangerously causing death rates to dramatically rise. The effects of this pollution on buildings and vegetation also became obvious.

The Great London Smog of 1952 which resulted in around 4,000 extra deaths in the capital, led to the introduction of the Clean Air Acts of 1956 and 1968. These introduced smokeless zones in urban areas, with a tall chimney policy to help disperse industrial air pollutants away from built up areas into the atmosphere.

Following the Clean Air Acts, air quality improvements continued throughout the 1970s and further regulations were required through the 1974 Control of Air Pollution Act. This included regulations for the composition of motor fuel and limits for the sulphur content of industrial fuel oil.

However, during the 1980s the number of motor vehicles in the UK steadily increased and air quality problems associated with motor vehicles became more prevalent. In the early 1980s, the main interest was the effects of lead pollution on human health, but by the late 1980s and early 1990s, the effects of other motor vehicle pollutants became a major concern. The 1990s have seen the occurrence of summertime smogs. These are not caused by smoke and sulphur dioxide pollution but by chemical reactions occurring between motor vehicle pollutants and sunlight. These are known as 'photochemical smogs.

In most urban areas of the UK, traffic generated pollutants have become the most common pollutants; primarily nitrogen oxides, carbon monoxide, hydrocarbons and particulates. Some of these are emitted directly into the atmosphere (primary pollutants) whilst others are formed in the air as a result of chemical reactions (secondary pollutants). The main urban air pollutants and their sources are shown below.

The Main Urban Air Pollutants. Source: DEFRA, 2001

Did You Know?

In South Yorkshire there are almost 300 sites where the 4 local councils monitor air quality. They include simple measuring devices and highly sophisticated automatic equipment that works 24 hours a day 7 days a week. View air quality data in your area here.