Sulphur Dioxide Exposure

Bronchoalveolar lavage (BAL) which has not previously been used in investigating the effect of sulphur dioxide (SO2) on the human lung was performed on 12 subjects before and after controlled chamber exposure with SO2 for 20 minutes. BAL fluid 24 hours after exposure with 10 mg S02/m3 (4 ppm, 10 subjects) showed increased alveolar macrophage activity as judged by an increase in lysozyme positive macrophages. Twenty four hours after 20 mg/m3 (4 subjects) a further increase was seen, which was accompanied by an increase in total numbers ofmacrophages and lymphocytes. Seventy two hours after exposure (4 subjects) cell numbers had virtually returned to pre-exposure levels. These previously uninvestigated reactions indicate potentially noxious effects of SO2 in the lungs at exposure levels that are regarded as relatively safe. Sulphur dioxide (SO2) is a gas that is rapidly oxidised to sulphuric acid in contact with moist epithelial surfaces in the eyes, nasopharynx, and lower airways, where it may cause damage. It is a major air pollutant in urban areas, particularly in the working environment of pulp industries and factories using various combustion and smelting processes. High peak exposures, many times exceeding the Swedish short term exposure limit of 13 mg SO2/m3 air (5 ppm), have been frequently found' (and N Stjernberg et al, unpublished data). Similar findings have been reported in other countries.23 Pulmonary effects of SO2 in man have mainly been studied indirectly by lung function tests,'5 tests of hyperreactivity,6 and in epidemiological surveys'7 (and N Stjemberg et a). Direct investigation has been restricted to workers who have died of massive exposure to SO2, in whom gross histopathological changes in the lung tissue with haemorrhagic alveolar oedema have been reported.8 Bronchoalveolar lavage (BAL), which is a commonly used method for investigating conditions at the alveolar level has not to our knowledge previously been used for studying SO2 effects in man. Our aim, using the BAL technique, was to determine if short term exposure to SO2 in concentrations around the Swedish short term exposure limit, concenAccepted 15 February 1988 trations which are commonly found in industrial environment, causes potentially harmful effects on the alveolar cell population.