Cardiovascular Effects of Incremental Diesel Exhaust Inhalation in Middle-Aged Healthy GSTM1 Null Human Volunteers

Inclusion Criteria: * Age 50-75 years old generally healthy male and female. * Normal resting ECG. * Oxygen saturation greater than 94% at the time of physical exam. Exclusion Criteria: * A history of angina, cardiac arrhythmias, and ischemic myocardial infarction or coronary bypass surgery. * Cardiac pacemaker. * Uncontrolled hypertension (\> 150 systolic, \> 90 diastolic). * Neurodegenerative diseases such as Parkinson's and Alzheimer disease. * A history of chronic illnesses such as diabetes, cancer, rheumatologic diseases, immunodeficiency state, known cardiovascular disease, chronic respiratory diseases such as chronic obstructive pulmonary disease or severe asthma. * History of bleeding diathesis. * Currently taking HMG-CoA reductase inhibitors for hyperlipidemia including lovastatin, pravastatin, simvastatin, and atorvastatin. * Currently taking beta-blockers to control hypertension and/or arrhythmias. * Use of oral anticoagulants. * Participants must refrain from all over-the-counter NSAIDs for a period of two weeks prior to exposure. Low-dose aspirin will be acceptable. Medications not specifically mentioned here may be reviewed by the investigators prior to a participant's inclusion in the study. * Subjects who are currently smoking or have smoking history within 1 year of study (defined as more than one pack of cigarettes in the past year). * Subject is pregnant, attempting to become pregnant or breastfeeding. * No exposure will be conducted within 4 weeks of a respiratory tract infection.