Secondhand smoke: Avoid dangers in the air

Exposure to the toxins in secondhand smoke can cause asthma, cancer and other serious problems. Know what you're breathing — and consider practical steps for clearing the air.

By Mayo Clinic Staff

You don't smoke because you understand the dangers — but what about smoke you inhale involuntarily? Secondhand smoke causes or contributes to various health problems, including heart disease and lung cancer. Understand what's in secondhand smoke, and consider ways to protect yourself and those you love from it.

What's in secondhand smoke?

Secondhand smoke — also known as environmental tobacco smoke — includes the smoke that a smoker exhales (mainstream smoke) and the smoke that comes directly from the burning tobacco product (sidestream smoke). Secondhand smoke contains toxic chemicals, including:

  • Ammonia, used in cleaning products
  • Butane, used in lighter fluid
  • Carbon monoxide, found in car exhaust
  • Chromium, used to make steel
  • Cyanide, used in chemical weapons
  • Formaldehyde, an industrial chemical
  • Lead, a toxic metal
  • Polonium, a radioactive substance

The dangerous particles in secondhand smoke can linger in the air for hours or even longer. It isn't just the smoke that's a concern, though. The residue that clings to a smoker's hair and clothing, as well as cushions, carpeting and other goods — sometimes referred to as thirdhand smoke — also can pose risks, especially for children.

March 26, 2015 See more In-depth