Q: What is the health risk of secondhand smoke for people with asthma?

Todd A. Mahr, MD: Secondhand smoke is the combination of smoke from the burning end of a cigarette and smoke that is breathed out by smokers. It contains about 7,000 chemicals, of which hundreds are toxic and 70 can cause cancer.

There’s no risk-free level of secondhand smoke exposure. Even a brief exposure can be harmful to health. Comprehensive smoke-free policies have been really successful in protecting those who don’t smoke.

Children with asthma who encounter secondhand smoke can have more frequent or severe asthma attacks. It can cause or have an influence on ear infections in infants and young children.

Secondhand smoke can cause respiratory symptoms such as cough, wheezing and shortness of breath. It can also lead to acute lower respiratory infections such as bronchitis or pneumonia.

The harmful effects of secondhand smoke extend beyond asthma. Secondhand smoke can cause heart disease in adults who have never smoked. Breathing in secondhand smoke has an immediate, harmful effect on the heart and blood vessels. People who are exposed to it at home or work are at increased risk of developing heart disease.

In addition, secondhand smoke causes 7,300 lung cancer deaths among nonsmokers every year in the United States. It also is attributed to more than 8,000 deaths from stroke each year.

Q: Are there health risks in secondhand vaping from an e-cigarette?

A: When you’re around someone who is vaping, it is possible to breathe in the aerosol from the e-cigarette. But there isn’t a lot of published research on how it affects a person’s body.

We know e-cigarettes don’t just emit harmless water vapor. They contain nicotine and ultra-fine particles and low levels of toxins that when inhaled secondhand can cause cancer. They contain propylene glycol and glycerin, which can worsen asthma symptoms.

Some ingredients found in e-cigarettes include:

  • Formaldehyde: a compound created when propylene glycol and glycerin is heated up in e-cigarettes. It’s absorbed by the lungs and can be toxic.
  • Acrolein: a compound made when glycerin is heated up by the coils of the e-cigarette. It can irritate the respiratory tract.
  • Benzene: a colorless, sweet-smelling organic compound that can irritate the lungs (it’s found in car exhaust).
  • Diacetyl: a food additive in some vaping liquids. It has a rich, buttery flavor. Diacetyl has been linked to popcorn lungs and bronchiolitis.
  • Lead, nickel, tin or other heavy metals: they help heat the vaping liquid. Small amounts of these metals can be aerosolized and inhaled.

Secondhand vaping is not as widely studied as secondhand smoking from cigarettes, but it clearly has some health effects.


Todd A. Mahr, MD, FACAAI, is an allergist and immunologist in La Crosse, Wisconsin. He is past president of the American College of Allergy, Asthma & Immunology (ACAAI) and formerly served as chairperson for the American Academy of Pediatrics Section on Allergy and Immunology.


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