EFFECTS OF AIR-POLLUTION ON SYMPTOMS AND PEAK EXPIRATORY FLOW MEASUREMENTS IN SUBJECTS WITH OBSTRUCTIVE AIRWAYS DISEASE

Background - Evidence from laboratory studies suggests that air pollut ion can produce bronchoconstriction and respiratory symptoms in select ed subjects, but the relevance of these findings to exposure to natura l pollution is unclear. This study was performed to determine whether air pollution at typical levels found in the UK has demonstrable effec ts on respiratory function and symptoms in subjects with airways disea se. Methods - Seventy five adult patients with diagnoses of asthma or chronic obstructive pulmonary disease (COPD) were studied for a period of four weeks during which they kept records of their peak expiratory flow (PEF) rates, symptoms (wheeze, dyspnoea, cough, throat and eye i rritation), and bronchodilator use. Thirty six patients in whom the pr ovocative dose of methacholine causing a 20% fall in FEV(1) was below 12.25 mu mol were classified as reactors. Ambient air pollution was me asured with absorption spectroscopy. Results - There were modest but s ignificant increases in PEF variability, bronchodilator use, and wheez e with increasing sulphur dioxide levels; bronchodilator use, dyspnoea , eye irritation, and minimum PEF readings were related to ozone level s. In the subgroup of reactors falls in mean and minimum peak flow and increases in wheeze, dyspnoea, and bronchodilator use were associated with increases in levels of both sulphur dioxide and ozone. Some asso ciations were seen with pollution levels on the same day, but for othe rs the pollution effects appeared to be delayed by 24 or 48 hours. Pol lution levels did not breach the WHO guide levels during the course of the study. Conclusions - Increases in environmental levels of ozone a nd sulphur dioxide are associated with adverse changes in peak flow me asurements and both ocular and respiratory symptoms in subjects with o bstructive airways disease. Although the peak flow and symptom changes were modest, they occurred at pollution levels below current WHO guid e levels.