Mental Stress & Diesel Exhaust on Cardiovascular Health

Inclusion Criteria: Non-smokers without history of high blood pressure, asthma, diabetes, high cholesterol, post-traumatic stress disorder (PTSD) or any other chronic condition that requires ongoing care. Exclusion Criteria: 1. Smoking: We rule out active smoking by checking urine cotinine during our study. 2. History of high blood pressure: We objectively measure BP during in-person screening and exclude those with blood pressure (\>130/85 mmHg). 3. Asthmatic: Spirometry is done at screening to rule out asthma. 4. Diabetic: We obtain fasting blood sugar to rule out diabetes at screening (\>125 mg/dL) 5. Cholesterol: We obtain fasting blood lipid levels to rule out hypercholesterolemia at screening (\>200 mg/dL). 6. History of PTSD: Subjects will be asked about prior PTSD diagnosis during the phone and in person screen. 7. Any other chronic condition requiring ongoing care based on medication use. 8. A body mass index (weight in kilograms divided by height in meters squared) greater than 26 and less than 18.5 9. A female of childbearing age with a positive pregnancy test 10. A female of childbearing age who is unwilling to use effective contraception during the study