PAI-1, an antifibrinolytic protein associated with exposure to ozone and particulate matter (Chuang et al., 2007) and implicated in thrombosis, atherogenesis, and metabolic syndrome (Alessi and Juhan-Vague, 2006), was increased by ozone, consistent with stress-induced activation of factors implicated in hypercoagulability (Yamamoto et al., 2002). Here, SERPINE1 is linked to metabolic syndrome.