Abstract: ObjectiveTo explore the relationship between ambient fine particulate matter <2.5 μm in aerodynamic diameter(PM_2.5)and plasma von Willebrand factor(vWF)level in healthy young adults.MethodsA total of 114 healthy young adults working and living in Peking University First Hospital were recruited.In a period of more than 4 months around the Olympic Games 2008,six blood samples at period 1 and 2(pre-Olympics),period 3 and 4(during-Olympics)and period 5 and 6(post-Olympics)were taken from the individuals for plasma vWF measurement.Daily concentrations of PM_2.5 were measured and provided by College of Environmental Sciences and Engineering,Peking University.ResultsThe average contents of PM_2.5 during the six periods(10th-23th of June,June 24th-July 7th,4th-15 of August,18th-29th of August,6th-17th of October,and 20th-30th of October)were 101.841 0,101.857 0,87.147 0,71.687 0,87.470 0,and 76.107 8 μg/m³,with the average plasma vWF of 103.933 0%,100.160 0%,91.704 0%,85.022 0%,88.460 0%,and 76.353 3%,respectively,for corresponding period.The correlation coefficients between plasma vWF and PM_2.5 concentrations of previous 0-5 days were-0.132(P=0.332),0.110(P=0.414),0.197(P=0.142),0.224(P=0.097),0.320(P=0.017),and 0.156(P=0.256),respectively,which showed the influence of PM_2.5 on plasma vWF levels had lagged effects of four days(P<0.05).ConclusionThe average plasma vWF level declined in association with the decrease of PM_2.5 among healthy young adults during the Olympic Games 2008 in Beijing.