Last week, CDC hosted a Facebook chat on the “unequal dangers” of secondhand smoke. Photo by CDC

One in four nonsmokers, or 58 million Americans, is exposed to secondhand smoke. Last week, the Centers for Disease Control and Prevention hosted a Facebook chat on its “unequal” dangers, led by Brian King, senior scientific advisor for epidemiology in CDC’s Office on Smoking and Health.

Read the chat in its entirety on CDC’s Facebook page. Here are several highlights:

Q: Are workplace non-smoking programs (or “smoke-free campuses”) actually effective? My workplace has this policy in place, but I seem to get MORE smoke exposure than when the smokers just had designated areas. Is there any evidence that non-smokers benefit from such policies?

A: We know that 100% smokefree workplaces fully protect from the harms of SHS exposure. The best thing to do for your health is to avoid being around people who are smoking. Don’t be afraid to ask them to not smoke around you.

Q: Which populations are the most at risk for high exposure to second hand smoke? Are there studies suggesting certain occupations provide the highest risk?

A: Black nonsmokers, young children, people who live in poverty, and those who rent their housing are more likely to be exposed to secondhand smoke than other groups.

Q: How long does nicotine stay in your system after you quit?

A: Nicotine leaves your blood stream within a few days after you last use a tobacco product or after being exposed to secondhand smoke.

Q: Do e-cigs produce a ‘secondhand smoke’ effect, and is it as bad a regular cigerettes?

A: E-cigs produce secondhand aerosol, not just harmless water vapor. E-cig aerosol is not as safe as clean air.