Respiratory infection is a major cause of morbidity and mortality, globally. Acute respiratory symptoms are also related to high levels of air pollution. Interventions aimed at reducing exposure to indoor air pollution should focus on cooking and heating practices in developing countries. This study is not undermining the role of other biomass smoke constituents in determining respiratory infections.

BackgroundUnprocessed biomass fuel is the primary source of indoor air pollution (IAP) in developing countries. The use of biomass fuel has been linked with acute respiratory infections. This study assesses sources of variations associated with the level of indoor nitrogen dioxide (NO2).Materials and methodsThis study examines household factors affecting the level of indoor pollution by measuring NO2. Repeated measurements of NO2 were made using a passive diffusive sampler. A Saltzman colorimetric method using a spectrometer calibrated at 540 nm was employed to analyze the mass of NO2 on the collection filter that was then subjected to a mass transfer equation to calculate the level of NO2 for the 24 hours of sampling duration. Structured questionnaire was used to collect data on fuel use characteristics. Data entry and cleaning was done in EPI INFO version 6.04, while data was analyzed using SPSS version 15.0. Analysis of variance, multiple linear regression and linear mixed model were used to isolate determining factors contributing to the variation of NO2 concentration.ResultsA total of 17,215 air samples were fully analyzed during the study period. Wood and crop were principal source of household energy. Biomass fuel characteristics were strongly related to indoor NO2 concentration in one-way analysis of variance. There was variation in repeated measurements of indoor NO2 over time. In a linear mixed model regression analysis, highland setting, wet season, cooking, use of fire events at least twice a day, frequency of cooked food items, and interaction between ecology and season were predictors of indoor NO2 concentration. The volume of the housing unit and the presence of kitchen showed little relevance in the level of NO2 concentration.ConclusionAgro-ecology, season, purpose of fire events, frequency of fire activities, frequency of cooking and physical conditions of housing are predictors of NO2 concentration. Improved kitchen conditions and ventilation are highly recommended.

The Willems badge, a short-term diffusion sampler, was used to measure nitrogen dioxide concentrations inside and outside the homes of participants in the European study "PEACE' (Pollution Effects on Asthmatic Children in Europe). The main aim of the study was to determine levels of nitrogen dioxide concentrations both outside and inside children's homes, and to estimate the indoor/outdoor ratios for nitrogen dioxide in an urban area, in comparison with a less urbanized control area. We conducted measurements in 23 homes in Umeå, a city of about 100,000 inhabitants in the northern part of Sweden, in addition to 20 homes in a less urbanized control area situated about 20 km from Umeå. Measurements were made on two different occasions in each home during the period January-March, 1994. The houses were not equipped with any gas appliances. The mean outdoor 24-h concentration in Umeå was 28 micrograms m-3 and the mean indoor concentration was 11 micrograms m-3. The mean indoor: outdoor ratio was 0.44 (s = 0.23). The highest outdoor value, measured in the city centre of Umeå, was 54 micrograms m-3. In the control area the mean ambient 24-h concentration was 12 micrograms m-3, approximately half as high as in the urban area, and the mean indoor concentration was 6 micrograms m-3. The mean indoor: outdoor ratio was 0.67 (s = 0.55). The correlation coefficient between indoor and outdoor concentrations was higher in the control area, r = 0.79 (p < 0.001), in comparison with the urban area, r = 0.43 (p < 0.01). It is concluded that the outdoor as well as the indoor concentrations of nitrogen dioxide were approximately twice as high in Umeå as in the control area. This could be explained by heavier traffic density in Umeå. The mean 24-h concentration outside homes in Umeå was, however, below the 24-h national standard level of 75 micrograms m-3. The higher correlation between indoor and outdoor concentrations, combined with higher indoor: outdoor ratio, in the control area is interpreted as a sign of a lower level of penetration of outdoor air into the houses in the urban area. This was not explained by differences in types of buildings between the two areas, but possibly by differences in air-exchange rates and in habits of ventilating rooms with open windows.