§ Mr. Peter BottomleyTo ask the Secretary of State for Health if he will estimate the relative contributions of(a) the house mite with central heating and (b) motor vehicle pollution to asthma and changes in the incidence of asthma. [28810]
§ Ms JowellThe prevalence of asthma has doubled in the United Kingdom over the last 15–20 years, in line with trends in other western countries. Asthma is a complex disease which is likely to be due to a number of different factors, including environmental. Neither the exact cause of asthma nor the precise reasons for this increased prevalence are known. A range of factors are known to trigger attacks in asthmatics including: exposure to allergens, infections, environmental tobacco smoke, high levels of outdoor air pollution, breathing cold dry air, exercise, and emotion.
It is not possible to estimate the relative contribution of these different factors to the prevalence of asthma. Central heating and well insulated homes provide the sorts of conditions in which house dust mites thrive. Sensitivity to the house dust mite allergen is certainly common in the UK. Motor vehicles are a major source of outdoor air pollution, high levels of which can lead to a worsening of symptoms in asthmatics. Also, there is some evidence that those who live close to busy roads are more likely to suffer from respiratory ailments and more asthma attacks.
A number of projects in a £3 million Department of Health/Department of the Environment, Transport and the Regions/Medical Research Council research programme on air pollution and health are currently examining some of the possible links between asthma and outdoor air pollution. The results of these should be known early next year. In addition, contracts for a three year £1 million joint DH/DETR indoor research programme looking at aspects of the indoor environment have just been let. When both these programmes have been completed, our understanding of some of the mechanisms at play in the development of asthma should be greatly improved.