INCREASED PLASMA VISCOSITY DURING AN AIR-POLLUTION EPISODE - A LINK TO MORTALITY

Background Air pollution episodes have been consistently associated wi th increased mortality, and most strikingly with mortality due to card iovascular disease. One hypothesis to explain this association is that inflammation of the peripheral airways caused by pollution might incr ease blood coagulability. We have tested this hypothesis in a cross-se ctional study by comparing measurements of plasma viscosity during a s evere episode of air pollution during 1985 with those made on less pol luted days. Methods Plasma viscosity was measured as part of the MONIC A Augsburg survey during the winter of 1984-85 in 3256 randomly select ed men and women aged 25-64 years. Daily mean concentrations of air po llutants and meteorological variables were measured in Augsburg as par t of the automated Bavarian air-quality network. We compared measureme nts of plasma viscosity made in 324 people who attended for screening during the pollution episode and in 2932 people screened during the re mainder of the survey period. Findings In January, 1985, high concentr ations of sulphur dioxide (mean 200 mu g/m(3)) and total suspended par ticles (mean 98 mu g/m(3)) were recorded during a 13-day period in Aug sburg. In men, the odds ratio for plasma viscosity above the 95th perc entile of the distribution (1.38 mPa s) was 3.6 (95% CI 1.6-8.1) compa ring measurements during the air pollution episode with non-episode me asurements after adjustment for cardiovascular risk factors and meteor ological variables. The corresponding odds ratio for women (95th perce ntile of plasma viscosity 1.37 mPa s) was 2.3 (1.0-5.3). High concentr ations of carbon monoxide were also associated with increased plasma v iscosity in women. Interpretation During the 1985 air pollution episod e, an increased risk of extreme values of plasma viscosity was observe d in both men and women. Altered blood rheology due to inflammatory pr ocesses in the lung that induce an acute-phase reaction might therefor e be part of the pathological mechanisms linking air pollution to mort ality.