The Public Protection Division continuously monitors air quality at the two sites in Islington shown as green dots on the map at the top right of this page.  The Upper Street site represents the Urban Background, and the results are indicative of the air quality experienced by the majority of Islington residents for most of the time.  The results at the Roadside site on Holloway Road are indicative of the worst conditions in Islington.
The results of the monitoring from the second quarter of the year are presented in the charts below.  Monthly average figures for particulates and nitrogen dioxide are given as well as the number of days or hours exceeding the relevant objective level during the month.  The maximum 8 hour average concentration of carbon monoxide recorded over each month is also presented.  The monthly results in each chart are combined to give the results for the quarter.

Air quality headline indicator for sustainable development: 2003

Air quality is one of the Government's 15 headline indicators of sustainable development. It measures the average number of days on which levels of any one of a basket of five pollutants (carbon monoxide, nitrogen dioxide, ozone, fine particles and sulphur dioxide) were 'moderate or higher' according to the Air Pollution Information Service bandings. These five pollutants are recognised as the most important for causing short term health effects.
In urban areas in 2003, air pollution was recorded as moderate or higher on 50 days on average per site, compared with 20 days in 2002, and 59 days in 1993. In general there has been a long term decline in the number of 'moderate or higher' air pollution days, largely because of a reduction in particles and sulphur dioxide, but fluctuations from one year to the next can occur, as in 2003, because of differences in weather conditions.
The main causes of days of moderate or higher air pollution at urban sites are ozone and fine particles (PM10). Sulphur dioxide also used to make a significant contribution but has now fallen to relatively very low levels. The other two pollutants included in the index, carbon monoxide and nitrogen dioxide, have very rarely reached moderate or higher levels since the urban index began in 1993.
Between 1993 and 2002, the average number of days of medium or higher air pollution at urban sites caused by fine particles, solely or in combination with other pollutants, fell from an average per site of about 43 days to 6 days per year, rising to 17 days in 2003. Particles come from numerous man-made and natural sources, and can be

generated in the UK or transported from abroad. UK emissions of particles have been reduced substantially in recent years, but the number of pollution days can still fluctuate from year to year due to variations in weather conditions.
The average number of polluted days caused by sulphur dioxide, solely or in combination, fell from an average per site of 20 days in 1993 to an average of three-tenths of a day per site in 2003.
The number of moderate or higher pollution days caused by ozone pollution has fluctuated in both rural and urban areas, with no overall trend being evident. Production of ozone is strongly influenced by the weather, being created on sunny summer days. The hot summer in 2003 led to the greatest number of days of moderate or higher ozone pollution since this series began in 1987. The high in 1999 was also associated with a hot summer.
Ozone causes the great majority of pollution days in rural areas, but since 1999 it has also caused more days of poor air quality in urban areas than particles have. Ozone undergoes reversible chemical reactions with nitric oxide to form nitrogen dioxide. Concentrations of nitric oxide and nitrogen dioxide and the intensity of sunlight determine the rate at which ozone is produced. Urban areas tend to have higher levels of oxides of nitrogen than rural areas with the result that ozone concentrations recorded at urban sites are generally lower there than in rural ones. A proportion of the ozone experienced in the UK originates from releases of pollution that are blown over from mainland Europe.