To investigate the toxicological effects of biogenic- versus anthropogenic-source secondary organic aerosol (SOA) on the cardiovascular system, the Secondary Particulate Health Effects Research program irradiation chamber was used to expose atherosclerotic apolipoprotein E null (Apo E-/-) mice to SOA from the oxidation of either α-pinene or toluene for 7 days. SOA atmospheres were produced to yield 250-300 μg/m(3) of particulate matter and ratios of 10:1:1 α-pinene:nitrogen oxide (NOx):ammonia (NH3); 10:1:1:1 α-pinene:NOx:NH3:sulfur dioxide (SO2) or 10:1:1 toluene:NOx:NH3; and 10:1:1:1 toluene:NOx:NH3:SO2. Resulting effects on the cardiovascular system were assessed by measurement of vascular lipid peroxidation (thiobarbituric acid reactive substance (TBARS)), as well as quantification of heme-oxygenase (HO)-1, endothelin (ET)-1, and matrix metalloproteinase (MMP)-9 mRNA expression for comparison to previous program exposure results. Consistent with similar previous studies, vascular TBARS were not increased significantly with any acute SOA exposure. However, vascular HO-1, MMP-9, and ET-1 observed in Apo E-/- mice exposed to α-pinene + NOx + NH3 + SO2 increased statistically, while α-pinene + NOx + NH3 exposure to either toluene + NOx + NH3 or toluene +NOx + NH3 + SO2 resulted in a decreased expression of these vascular factors. Such findings suggest that the specific chemistry created by the presence or absence of acidic components may be important in SOA-mediated toxicity in the cardiovascular system and/or progression of cardiovascular disease.