How Dangerous is Secondhand Smoke?
You hear about the dangers of secondhand smoke, and that it increases the risk of cancer for people exposed to it, but what are the facts? How much do we actually know about the effects of secondhand smoke, or "passive smoking," as it's sometimes called?
Second smoke is a mixture of gas and particles that enter the environment in two ways: from the burning cigarette, cigar or pipe (this is also called "sidestream" smoke") and from the smoke that's exhaled by the person who's smoking. According to the U.S. Department of Health and Human Service's National Toxicology Program's "11th Report on Carcinogens 2005," secondhand smoke contains at least 250 chemicals that are known to be toxic. Of those 250 chemicals, more than 50 are considered capable of causing cancer. These carcinogens include:
- Vinyl chloride
- Hydrogen cyanide
Second-hand smoke has been designated as a "known carcinogen" by the following groups:
- The U.S. Environmental Protection Agency
- The National Toxicology Program
- The International Agency for Research on Cancer
Additionally, the National Institute for Occupational Safety and Health has concluded that secondhand smoke is an occupational carcinogen.
A review of literature on the effects of secondhand smoke on passive smokers shows the following:
- Secondhand smoke causes lung cancer and heart disease in adults who don't smoke
- When nonsmokers are exposed to secondhand smoke at home or at work, their risk of lung cancer increases by 20 to 30 percent and their risk of heart disease increases by 25 to 30 percent.
- Many of the concentrations of the cancer-causing and toxic chemicals are higher in secondhand smoke than they are in the smoke that smokers inhale
- Some research indicates that exposure to secondhand smoke increases the risk of cancer to the nasal sinus
To determine the level of exposure to secondhand smoke, scientists measure nicotine, smoke particles and tobacco particles in the breathing zone of a nonsmoker. Additionally, the level of a substance called cotinine is measured in the urine. Cotinine is a byproduct of nicotine that's been metabolized, and tobacco is the only source of cotinine. In other words, cotinine is what's called a "biomarker" for assessing recent exposure to secondhand smoke.
Non-cancer related effects of secondhand smoke
It's not just the risk of cancer that can increase with exposure to secondhand smoke. Research has shown that:
When children are exposed to secondhand smoke, they're at an increased risk of
- Sudden infant death syndrome
- Acute respiratory infections
- Ear problems, bronchitis and pneumonia
- A worsening of existing asthma
Adults are affected too. Breathing secondhand smoke for even a short period of time can damage the lining of blood vessels and reduce the ability of the heart to respond appropriately to the body's need for blood flow (this is called "heart rate variability:). This increases the risk of heart attack. And the upper respiratory system of adults can also be affected by secondhand smoke, which irritates the lining of the airways.
The Centers for Disease Control and Prevention; The U.S. Department of Health and Human Services, " The Health Consequences of Involuntary Exposure to Tobacco Smoke," Office of the Surgeon General, 2006; U.S. Department of Health and Human Service's National Toxicology Program's "11th Report on Carcinogens 2005