Respiratory Effects of Kerosene Space Heater Emissions

Abstract

Kerosene space heaters are widely used as a major source of home heat in the United States and in countries such as Japan and Korea. Based on a report that evaluated particle emissions from unvented kerosene space heaters in an environmental chamber, kerosene space heaters can be an important indoor source of fine particles and a major source of sulfate and acidic aerosols. In this study, guinea pigs were exposed to filtered air or kerosene space heater (9000 Btu radiant heater) emissions for 3 h/day for 1 wk or 6 h/day, 5 days/wk for 4 wk. The following pollutant concentrations were measured during the exposure period: total mass loading, 69 μg/m³; NO₂, 0.17 ppm; particle number concentration, 2.7 × 10⁵/cm³; SO₂, 0.093 ppm; SO₄^2-, 28.7 μg/m³. Nonspecific airway responsiveness was monitored before and during the 4-wk exposure period. Biochemical parameters in lavage fluid as well as functional characteristics of pulmonary macrophages were determined 24 h after the final exposure. In comparison to preexposure values, the concentration of acetylcholine that decreased specific airway conductance by 50% was significantly decreased after 1 and 4 wk of exposure. These functional changes were accompanied by a small increase in lavage fluid protein following 4 wk of exposure (58%, p < .05) and by a number of alterations in pulmonary macrophages. Intracellular free Ca2' concentration ([Ca²⁺]_i) increased by 85% at the end of the 4-wk exposure. Small but statistically significant decreases in intracellular pH (pH_i) of recovered lavage cells were also observed at the end of the 1-wk and 4-wk exposures. Furthermore, the in vitro phagocytic function of pulmonary macrophages was enhanced by 51% at the end of the 1-wk exposure and depressed by 19% at the end of the 4-wk exposure. Other changes in biochemical parameters or cell numbers were not observed. We conclude that repeated exposure to kerosene space heater emissions at concentrations relevant to those encountered in home use can produce alterations in airway responsiveness and pulmonary macrophage function in guinea pigs.