Many people assume vaping is harmless to bystanders, but secondhand aerosol can contain ultrafine particles and chemical residues. Researchers are examining how exposure may affect airways and overall health, especially for children Just How Harmful Is Vaping? More Evidence Is Emerging. The New York Times Is Secondhand Vape Smoke Bad For Pregnancy? Experts Explain The Risks According to a Centers for Disease Control and Prevention (CDC) study, 40% of U.S. adults believe that children's exposure to secondhand aerosol from e cigarettes causes only some or little harm, and 5%