[Factors aggravating bronchial asthma in urban children (I)--The involvement of indoor air pollution].

The aggravation of bronchial asthma in today's urban child population was studied by an epidemiological study in order to elucidate the involvement of indoor air pollution in relation to housing style. The asthma group consisted of 210 children under 12 years old who had been recently diagnosed as having bronchial asthma and under the care of Osaka Prefectural Habikino Hospital. The non-asthma group consisted of 180 children under 12 years old who had been under care at Osaka Prefectural Hospital but had no present history of allergic symptom. The individual atmospheric environment and housing style were surveyed by questionnaire. Also, the amount of mite allergen (Dp: Dermatophagoides pteronyssinus, Df: Dermatophagoides farinae) in room and bedding dust and the concentration of cotinine in urine were examined as objective indicators for the load of environmental allergen and the indoor air pollution by tobacco smoke, respectively. In this study, bronchial asthma was classified into two types: atopic/non-atopic, according to whether Dp-specific immunoglobulin E (Dp-IgE) was present/absent (positive/negative). Thus, for the risk factors given above, their involvement in each type of asthma was examined by comparing the proportion of the exposed subjects between the three groups of atopic asthma, non-atopic asthma and non-asthma. As atopy is an important factor of child asthma, the relative risk (odds ratio) of Dp-IgE increase (atopy) was also determined for the same factors by logistic regression analysis in each of the asthma and non-asthma groups. The results are as follows: 1. Reinforced concrete housing material, which results in mal-ventilation, increased the load of indoor air pollutants such as tobacco smoke. 2. A higher amount of mite allergen in bedding dust increased Dp-IgE. 3. Heating with stove, which results in a higher room humidity as well as temperature, enhanced Dp proliferation and appeared to be involved in increasing the risk of atopic asthma. 4. Reinforced concrete housing material appeared to be involved in suppressing Dp-IgE and increasing the risk of non-atopic asthma. But some air pollutants such as tobacco smoke and mite allergen showed no relationship to these involvements.