Background: Secondary heating appliances are important indoor sources of air pollution, including particulate matter, nitrogen dioxide (NO2), and sulfur dioxide (SO2). We hypothesized that the use of secondary heating sources increases respiratory symptoms in women living in nonsmoking households and specifically that concentrations of SO2 and NO2 emitted from heating sources are associated with respiratory symptoms.
Methods: Mothers who delivered babies at 12 hospitals in Connecticut and Virginia (1993-1996) were enrolled. There were 888 women who contributed symptom and exposure information during the winter heating season (15 October to 15 April), for a total of 9783 reporting periods (median = 12 reporting periods per woman, interquartile range 11-12). Adjusted rate ratios (RRs) of effects of source use and measured concentrations on rate of days with symptoms were obtained using generalized estimating equations for a log-linear Poisson model, controlling age, education, race, history of allergies, number of children, dwelling type, and residence state.
Results: In adjusted models, each hour-per-day increase in kerosene heater use is associated with an increase in wheezing (RR = 1.06; 95% confidence interval (CI) = 1.01-1.11). Each hour of fireplace use is associated with increased cough (1.05; 1.01-1.09), sore throat (1.04; 1.00-1.08), and marginally with chest tightness (1.05; 0.99-1.12). Each 10 ppb increase in SO2 (a proxy for sulfate aerosol) is associated with increased wheezing (1.57; 1.10-2.26) and chest tightness (1.32; 1.01-1.71).
Conclusions: Emissions from fireplaces, gas space heaters, and kerosene heaters may contribute to respiratory symptoms in a population of nonsmoking women.