Acute Health Effects of Traffic-Related Air Pollution Exposure

Inclusion Criteria: * Living in Shanghai during the study period; * Body mass index \> 18.5 and ≤ 28; * Non-smoking, no history of alcohol or drug abuse; * Completing the walking task we required. Exclusion Criteria: * Current or ever smokers; * Subjects with allergic disease, such as allergic rhinitis, allergic asthma, and atopy; * Subjects with cardiovascular disease, such as congenital heart disease, pulmonary heart disease, and hypertension; * Subjects with respiratory disease, such as asthma, chronic bronchitis, and chronic obstructive pulmonary disease; * Subjects wih chronic disease, such as diabetes, chronic hepatitis, and kidney disease; * Subjects with a history of major surgery; * Abnormal spirometry (FEV1 and FVC ≤ 75% of predicted and FEV1/FVC ≤ 0.65); * Medication use or dietary supplements intake in recent two months;