Daily concentrations of air pollution and plasma fibrinogen in London

Objectives-The reason for the association between air pollution and risk of cardiovascular diseases is unknown. The hypothesis was examined that daily concentrations of air pollution are associated with daily concentrations o f fibrinogen, a risk factor for cardiovascular disease. Methods-Data on concentrations of plasma fibrinogen for 4982 male and 2223 female office workers, collected in a cross sectional survey in London betw een September 1991 and May 1993,were combined with data on concentrations o f air pollution during the day of blood sampling and during the 3 preceding days. Results-After adjustment for weather and other confounding factors, an incr ease in the 24 hour mean NO2 during the previous day from the 10th to the 9 0th percentile (61.7 mug/m(3)) was associated with a 1.5% (95% confidence i nterval (95% CI) 0.4% to 2.5%) higher fibrinogen concentration. The respect ive increase for CO (1.6 mg/m(3)) was 1.5% (95% CI 0.5%, 2.5%). These assoc iations tended to be stronger in the warm season (April to September). Sign ificant associations were found for black smoke and particulate matter of d iameter 10 mum (PM10) only in the warm season. No association with fibrinog en was found for SO2 or ozone. Conclusions-The short term association between air pollution, possibly from traffic, and risk of cardiovascular events may be at least partly mediated through increased concentrations of plasma fibrinogen, possibly due to an inflammatory reaction caused by air pollution.