Environmental tobacco smoke (ETS) refers to which of the following?

• A. The mix of inhaled smoke and smoke from the end of lit cigarettes
• B. Smoke inhaled while smoking remains inside the lungs
• C. A chemical additive found in cigarettes
• D. The air quality index used near factories

Answer: (A)

Environmental tobacco smoke is the smoke non-smokers breathe in when someone nearby is smoking. It’s the combination of smoke from the burning end of a cigarette (sidestream) and the smoke exhaled by the smoker (mainstream). This is why the option describing a mix of inhaled smoke and the smoke from the end of lit cigarettes fits best: it captures both sources of secondhand smoke. The other choices describe the smoker’s own inhalation, a cigarette additive, or an air quality index, none of which define ETS.