§ Mr. Frank Cook
To ask the Secretary of State for the Environment what is the average proportion in poor quality air of pollution that comes from(a) car fumes and (b) industrial emissions. 
§ Mr. Atkins
Each episode of poor air quality has its own individual characteristics, so it is not possible to directly attribute the relative contribution that road traffic or industrial emissions contribute to air pollution incidents across the UK. However, detailed emissions inventories of the overall pollutant contributions of the various sectors are available. The table shows the proportions for NOx, SO2, CO and black smoke for London in 1991.
Percentage air emissions by sector for London in 1991 Figures are all rounded to one decimal place. Per cent. Pollutant NOx SO2 CO CO2 Black smoke Road transport 75.4 24.5 98.6 32.5 95.2 Domestic 6.5 0.7 0.2 31.4 0.1 Commercial and industrial 11.8 72.6 0.2 29.9 2.4 Other transport 6.4 2.1 1.0 6.3 2.4