Electronic Cigarette Use in US Adults at Risk for or with COPD: Analysis from Two Observational Cohorts Journal of General Internal Medicine Springer Nature Link Links to E Cigarette Resources American Lung Association Older users of e cigarettes at greater risk of respiratory illness, study suggests CUNY Graduate School of Public Health & Health Policy E cigarette use increases risk for developing major respiratory diseases Association of electronic cigarette use and risk of COPD: a systematic review and meta analysis npj Primary Care Respiratory Medicine