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 of 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 between September 1991 and May 1993,were combined with data on concentrations of air pollution during the day of blood sampling and during the 3 preceding days. Results-After adjustment for weather and other confounding factors, an increase in the 24 hour mean NO2 during the previous day from the 10th to the 90th percentile (61.7 mug/m(3)) was associated with a 1.5% (95% confidence interval (95% CI) 0.4% to 2.5%) higher fibrinogen concentration. The respective increase for CO (1.6 mg/m(3)) was 1.5% (95% CI 0.5%, 2.5%). These associations tended to be stronger in the warm season (April to September). Significant associations were found for black smoke and particulate matter of diameter 10 mum (PM10) only in the warm season. No association with fibrinogen 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.