How to describe indoor environment in epidemiological studies dealing with respiratory diseases

Background: Indoor environment can be partly responsible for respiratory health. The aim of this paper is to summarize epidemiological studies dealing with the relations between indoor pollutions and asthma or atopy, to analyze the ways of characterization of the dwellings and to expose health effects of the studied risk factors and results of the confrontation between data issued from questionnaires and from environmental measurements. Methods: Thirty two papers were listed on Medline data base since 1990. These are mainly case-control studies and cross-sectional surveys and most often concern children. The health status is objectively evaluated by medical examinations or indirectly, characterized by questionnaires on symptoms. All the studies use a questionnaire to describe indoor environment while some environmental measurements, mostly of biological pollutions, could be realized simultaneously. Results: Some associations between different characteristics of the dwellings and respiratory symptoms are commonly found. Thus, exposure to allergens of the dwellings, environmental tobacco smoke, home dampness or characteristics and cleaning of the bedding increase the prevalence of respiratory symptoms. Residential exposure to chemical pollutants, due to the existence of recent paints are also related to different respiratory symptoms. BY contrast, for other indoor risk factors, without standardized evaluation, the impact on respiratory health is inconstant. These factors are sociodemographic environment, heating and cooking installations, use of a humidifier, treatment air system or ventilation system, wall-to-wall carpets or pets at home. Conclusions: On examining this review literature, disparity in description of the indoor environment, depending on the studied pollutants, is pointed out. That is why we advice to use ever validated questionnaires to evaluate environmental tobacco smoke, home dampness and presence of pets, in association with environmental measurements to study indoor sources of allergens. Conversely, to evaluate the home exposure to chemical pollutions poorly studied today, some new questionnaires have to be elaborated and validated with regard to environmental measurements before being used in epidemiological studies.