Cigarette smoke (CS), e-cigarette smoke (EC), hookah smoke (HS), and Little Cigar smoke (LCS)-exposed populations will be stratified based on their responses to a smoking diary, protocol questionnaire, as well as urine cotinine levels (which should be present in all three groups). We are aware that many current smokers are poly-tobacco product users (i.e. smoke cigarettes in addition to non-cigarette products), which could be confounding our observations. This will be controlled for by having potential volunteers complete a smoking diary and provide daily urine samples for 1 week prior to enrolling in the study. Based on this diary, subjects will be grouped as CS (cigarettes only), EC (e-cigarette smokers and smoking less than ½ pack of cigarettes per week), HS (hookah smokers and smoking less than ½ pack of cigarettes per week), and LCS (little cigar smokers and smoking less than ½ pack of cigarettes per week). Individuals with mixed exposures that exceed those described above (i.e. smoking more than ½ pack of cigarettes per week in addition to smoking hookah, e-cigarettes, or Little Cigars) will be excluded from the studies. Potential subjects will then complete a questionnaire regarding their smoking history, and will undergo urine collection for measurement of cotinine for 7 consecutive days. Subjects will be assigned to the different groups as followed: Group NS (no routine exposure to tobacco smoke, and average log10 urine cotinine/creatinine ratio < 1.0), Group CS (active cigarette smoker and log10 urine cotinine/creatinine ratio > 4), Group EC (active e-cigarette smokers and average log10 urine cotinine/creatinine ratio 1-4), Group HS (active routine hookah smokers and average log10 urine cotinine/creatinine ratio 1-4), or Group LCS (active routine Little Cigars smoker and average log10 urine cotinine/creatinine ratio 1-4).