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Key Action 4 : Environment and Health
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Asthma and allergies

Hundreds of agents can trigger an allergy, but different people react to different allergens, and the problem is to understand why more and more people are affected. Could changes in their lifestyle and environment be responsible for this? Asthma and allergies : picture
Case Studies

Particles and allergy

Under surveillance

Teaching us tolerance

Respiratory allergies such as hay fever and asthma are increasing on a global scale. In Western Europe, the prevalence of asthma is reported to have doubled in the last ten years, while allergies in general are also on the increase. One striking feature is the geographical variation in allergy prevalence in Europe – major international studies focusing on asthma and allergies in children have found a 20-fold difference between various European centres, the reasons for which remain to be explained.

Cause and effect

Allergy is an over-reaction of the immune system to a substance it perceives as 'foreign'. Outdoor air pollution aggravates respiratory allergies and is suspected of causing allergies. They are, indeed, more prevalent in large cities than in rural areas, and workers experiencing chronic exposure to gases, fumes, and biological and mineral dusts are particularly susceptible. Yet prevalence of asthma and allergy does not correlate precisely with air pollution levels in different cities.

The indoor environment seems to play an important role. Warm homes with soft furnishings and carpeting tend to have high levels of allergy triggers, such as dust mites, pet fur, moulds, damp tobacco smoke, and gas heater fumes. There are also suggestions that infants raised in a very hygienic environment are more allergy-prone in later life than those brought up in contact with dirt, animals, and other children. Early exposure to certain bacteria may actually protect us against allergies.

KA4 investigates

Research is needed to unravel the genetic, environmental, dietary, lifestyle and medical causes of allergies. To achieve this, projects are exploiting the European diversity of lifestyles and environments. By means of surveys, pollutant measurements, clinical studies, and DNA banks, European researchers are seeking the keys that will access better allergy prevention.

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Case Studies

Particles and allergy

There are major differences in the prevalence of respiratory allergies across Europe. As small airborne particles appear to be important contributing factors here, the RAIAP project1 is addressing the question: "Do qualitative differences in particulate air pollution at different locations explain differences in the prevalence and severity of respiratory allergies?"

The partners are collecting particulate samples from Lodz, Oslo, Rome, Amsterdam, and a Dutch coastal location. They will examine the particles to determine their physico-chemical characteristics and to see whether known antigens or inflammatory agents are bound to them. The team will then test the allergic and inflammatory potential of the samples in model systems and try to clarify the mechanisms by which particles modulate inflammatory or immune responses.

A final report will review the latest knowledge and will point to possible preventive measures.

(1) Respiratory allergy and inflammation due to ambient particles – a European-wide assessment: QLK4-2000-00792

Prof. Erik Dybing
National Institute of Public Health, (NO)
Erik.dybing@folkehelsa.no

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Case Studies

Under surveillance

In 1992-93, more than 10 000 young adults living in 24 countries, mainly in Europe, were selected at random from population registers to take part in a cross-sectional study of asthma and allergic disease. Questionnaire data provided information on respiratory symptoms, diagnosed asthma and its treatment, smoking, occupation, and housing (including the presence of pets and gas appliances) and other environmental factors. Participants in the study underwent lung function tests and provided blood samples for serum markers for allergy. The survey demonstrated large geographical variations in the prevalence of asthma and allergy. Further analyses identified associations between environmental factors – including exposures in the workplace – and disease.

Today, the nine-year follow-up2 of this study is under way. Questionnaire data are being collected and participants are repeating lung function tests and providing blood samples. These are being stored in a ‘bank’ to allow for analysis for candidate ‘susceptibility genes’, at a later date.
Analysis of the results will show how factors in indoor, outdoor and professional environments relate to the incidence and prognosis of allergy and allergic disease, and will identify factors which contribute to lung function decline. The extent to which the effect of such exposures is influenced by genetic predisposition may also be examined.

(2) European Community Respiratory Health Survey II (ECRHS II): QLK4-1999-01237

Jill Knox
King's College London (UK)
jill.knox@kcl.ac.uk

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Case Studies

Teaching us tolerance

The Allergyflora project3 is focusing on a group of 300 infants in their first year of life. Partners are identifying the bacteria that compose the intestinal microflora of such a group, and are collecting data on family size, day care, housing conditions, and indoor and outdoor air pollution (at recruitment stage), and on feeding practices, vaccinations, day care, illnesses and medications (during the study). They will screen the children for signs of allergy at one-and-a-half and three years of age, and parents will supply additional information via a questionnaire.

The idea is that certain groups of intestinal bacteria might 'teach' an infant's immune system not to over-react to the presence of innocuous antigens, and that the absence of these bacteria would result notably in the development of allergies. Extreme hygiene could account for the absence of these key bacteria. If this hypothesis is proved to be correct, it may help explain why allergies are increasing in Europe. This knowledge may be used in efforts to modify the composition of the intestinal flora by means of 'probiotic' foods.

(3) Impact of intestinal microflora on allergy development: QLK4-2000-00538

Dr Agnes Wold
Department of Clinical Bacteriology (SE)
agnes.wold@microbio.gu.se

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