240 subjects from the Louisville Healthy Heart Study (LHHS) will be invited to participate in a study evaluating the efficacy of carnosine in preventing particulate matter air pollution (PM2.5)-induced vascular injury. This is a placebo controlled, randomized, double-blind, Phase II interventional trial. Subjects will be randomized to receive placebo or carnosine between May 1 and August 31, when the levels of PM2.5.are highest in Louisville (average between 10-20 mg/m3). In each of the 2 study years, the participants will take maximal tolerable dose of carnosine - 2 tablets every day in the morning, 500 mg each, shown to be effective in diabetic nephropathy. Carnosine levels and cardiovascular outcomes will be measured before the intervention and at 2 additional times (till the end of August) to assess efficacy of intervention. Thus, all participants will be on carnosine for 4 months and carnosine levels and vascular function will be examined so that the investigators will have three measurements from each participant at high and low levels of PM2.5 exposure. At each study visit, collected blood samples will be used to measure indices of CVD risk (LDL, HDL, cholesterol, total cholesterol, triglycerides, glucose, HbA1c, serum creatinine and fibrinogen) and biomarkers of vascular injury and inflammation. In addition, the investigators will assess vascular function (flow mediated dilation, reactive hyperemia, or arterial stiffness) and measure biomarkers of exposure (cotinine, and 18 VOC metabolites, carnosine conjugates, creatinine) and oxidative stress (isoprostanes) in urine samples. Statistical mixed effects models to evaluate the association between PM2.5 and vascular dysfunction.