The UK has the highest prevalence of asthma symptoms in 13-14 year olds in the world. Over the past 25 years the incidence of asthma episodes has increased by a factor of three to four in adults and six in children. Why should this be? Although allergic disease is on the increase across the developed world, several cities with high levels of air pollution from traffic fumes--such as Athens and Milan--have seen a comparatively modest increase in asthma prevalence. What factors are specific to the UK that can be identified as key drivers, and more importantly, what can be done to either slow this increase or reverse the trend?
The OPEC oil crisis in the mid-seventies, produced a drive for energy efficiency. Modern dwellings now have higher levels of insulation, and double-glazing combined with tighter construction and smaller room volumes, have dramatically reduced domestic ventilation rates. These factors, in the context of a cold maritime climate, have produced a warmer and more humid indoor environment. Furthermore, the ubiquitous use of wall-to-wall carpeting unique to the UK, has produced the ideal habitat for house dust mite colony establishment and proliferation.
A systemic literature review recently published by the United States Institute of Medicine, identified only one substance where there was sufficient evidence to implicate it as both a casual mechanism in the aetiology of the disease, and as an irritant likely to trigger and exacerbate asthmatic symptoms. The highly allergenic substance where the proteins excreted by the house dust mite. Eight out of ten asthmatic children in the UK have an allergic reaction to these proteins. As sensitization requires a known exposure threshold, it is highly likely that most UK dwellings now contain HDM allergen burdens in sufficient concentrations to trigger an immunological response.
The book reviews the evidence base which supports the HDM hypothesis as being central to the current UK asthma pandemic, and reports on the health benefits achieved in an interventionist trial that successfully reduced HDM allergen levels while improving indoor air quality in 45 Scottish dwellings.
Such a preventative strategy demands a new approach to house design, construction and specification, if the negative impacts on indoor air quality and respiratory health--currently associated with the drive for energy efficiency--are to be avoided. If the compelling evidence demonstrating causality between house conditions and asthma continues to be ignored by those involved in the design, production and management of the housing stock, legal action by the afflicted is inevitable and may well find them both culpable and liable.
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