Secondhand Smoke: Questions and Answers
- What is secondhand smoke?
- What chemicals are present in secondhand smoke?
- What are the health effects of exposure to secondhand smoke?
Secondhand smoke, also called environmental tobacco smoke, is the combination of two forms of smoke from burning tobacco products: sidestream smoke and mainstream smoke. Sidestream smoke, which makes up about half of all secondhand smoke, comes from the burning end of a cigarette, cigar, or pipe. Mainstream smoke is exhaled by the smoker. Exposure to secondhand smoke is also called involuntary smoking or passive smoking.
Many factors affect what chemicals are present in secondhand smoke. These factors include the type of tobacco, the chemicals added to the tobacco, how the product is smoked, and the paper in which the tobacco is wrapped. More than 4,000 chemicals have been identified in mainstream tobacco smoke; however, the actual number may be more than 100,000. Of the chemicals identified in secondhand smoke, at least 60 are carcinogens, such as formaldehyde. Six others are substances that interfere with normal cell development, such as nicotine and carbon monoxide.
Some of the compounds present in secondhand smoke become carcinogenic only after they are activated by specific enzymes in the body. After these compounds are activated, they can then become part of a cell’s DNA and may interfere with the normal growth of cells. In 1993, the U.S. Environmental Protection Agency determined that there is sufficient evidence that secondhand smoke causes cancer in humans and classified it as a Group A carcinogen. In 2000, the U.S. Department of Health and Human Services formally listed secondhand smoke as a known human carcinogen in The U.S. National Toxicology Program’s 10th Report on Carcinogens. The most recent report can be found at http://ntp.niehs.nih.gov/ntp/roc/toc11.html on the Internet.Scientists do not know what amount of exposure to secondhand smoke, if any, is safe. Because it is a complex mixture of chemicals, measuring secondhand smoke exposure is difficult and is usually determined by testing blood, saliva, or urine for the presence of nicotine, particles inhaled from indoor air, or cotinine. Nicotine, carbon monoxide, and other evidence of secondhand smoke exposure have been found in the body fluids of nonsmokers exposed to secondhand smoke. Nonsmokers who live with smokers in homes where smoking is allowed are at the greatest risk for suffering the negative health effects of secondhand smoke exposure.
Secondhand smoke exposure is a known risk factor for lung cancer. Approximately 3,000 lung cancer deaths occur each year among adult nonsmokers in the United States as a result of exposure to secondhand smoke. Secondhand smoke is also linked to nasal sinus cancer. Some research suggests an association between secondhand smoke and cancers of the cervix, breast, and bladder. However, more research is needed in order to confirm a link to these cancers.
Secondhand smoke is also associated with the following noncancerous conditions:
- chronic coughing, phlegm, and wheezing
- chest discomfort
- lowered lung function
- severe lower respiratory tract infections, such as bronchitis or pneumonia, in children
- more severe asthma and increased chance of developing asthma in children
- eye and nose irritation
- severe and chronic heart disease
- middle ear infections in children
- sudden infant death syndrome
- low birth weight or small size at birth for babies of women exposed to secondhand smoke during pregnancy
Certain other noncancerous health conditions may also be associated with secondhand smoke. However, more research is needed in order to confirm a link between these conditions and secondhand smoke. These conditions include:
- spontaneous abortion
- adverse effect on cognition and behavior in children
- worsening of cystic fibrosis
In January 2000, the DHHS launched Healthy People 2010, a comprehensive, nationwide health promotion and disease prevention agenda designed to help improve the health of all people in the United States during the first decade of the 21st century. Several objectives of this program relate to tobacco use and exposure to secondhand smoke, including the goal of reducing the proportion of nonsmokers exposed to secondhand smoke from 65 percent to 45 percent by 2010. More information about this program is available on the Healthy People 2010 Web site at http://www.healthypeople.gov/ on the Internet.
Studies have shown that separating smokers and nonsmokers within the same air space may reduce, but not eliminate, nonsmokers’ exposure to secondhand smoke. Individuals can reduce their exposure to secondhand smoke by not allowing smoking in their home or car. Educational, clinical, and policy interventions have also been shown to reduce secondhand smoke exposure. Such policies include adoption of worksite restrictions, passage of clean indoor air laws, and enforcement of smoking restrictions in shared environments.
On the national level, several laws restricting smoking in public places have been passed. For instance, effective January 1, 2005, smoking is banned in all DHHS buildings. In other Federal office buildings, smoking is limited to designated areas. Smoking is also banned on all domestic airline flights and nearly all flights between the United States and foreign destinations. All interstate bus travel is smoke free. Smoking is also prohibited or restricted to specially designated areas on trains traveling within the United States.Many states and local governments have passed laws prohibiting smoking in public facilities such as schools, hospitals, airports, and bus terminals. Some states also require private employers to create policies that protect employees who do not smoke, and several local communities have enacted nonsmokers’ rights laws, most of which are stricter than state laws. More information about state-level tobacco regulations is available through the Centers for Disease Control and Prevention’s State Tobacco Activities Tracking and Evaluating System Web site. The STATE System is a database containing up-to-date and historical state-level data on tobacco use prevention and control. This resource is available at http://apps.nccd.cdc.gov/statesystem/ on the Internet. Although it is still a significant public health concern, nonsmoker exposure to secondhand smoke declined by more than 70 percent from 19881991 to 19992000. In 1999, nearly 7 out of every 10 U.S. workers reported having a smoke-free policy in their workplace.
The following resources provide additional information about secondhand smoke and its health effects:
Health Effects of Exposure to Environmental Tobacco Smoke: The Report of the California Environmental Protection Agency, published by the National Cancer Institute, provides a broad review of secondhand smoke covering the major health endpoints potentially associated with secondhand smoke exposure. It is available at http://cancercontrol.cancer.gov/tcrb/monographs/10/ on the Internet.
The Health Consequences of Involuntary Smoking, a report by the U.S. Surgeon General, is a detailed review of the health effects resulting from nonsmoker exposure to secondhand smoke. It is available at http://www.cdc.gov/tobacco/sgr/sgr_1986/ on the Internet.
The EPA publication Respiratory Health Effects of Passive Smoking describes the EPA’s assessment of the respiratory health risks associated with exposure to secondhand smoke. It is available at http://cfpub2.epa.gov/ncea/cfm/recordisplay.cfm?deid=2835 on the Internet. The EPA can be contacted at:
Environmental Protection Agency
- The International Agency for Research on Cancer’s Monographs Programme on the Evaluation of Carcinogenic Risks to Humans publishes independent assessments of the carcinogenic risks posed to humans by a variety of agents, mixtures, and exposures. The IARC monograph Tobacco Smoke and Involuntary Smoking is available at http://www-cie.iarc.fr/htdocs/indexes/vol83index.html on the Internet. The IARC Web site can be found at http://www.iarc.fr/index.html on the Internet.
The CDC’s Tobacco Information and Prevention Source Web site is the home page of the CDC’s Office on Smoking and Health. This site offers links to information about the prevention of tobacco use among youth, smoking cessation, and tobacco-related statistics. It is available at http://www.cdc.gov/tobacco/ on the Internet. The Office on Smoking Health can be contacted at:
Address: Office on Smoking and Health
National Center for Chronic Disease Prevention and Health Promotion
Centers for Disease Control and Prevention
Mail Stop K50
4770 Buford Highway, NE. Atlanta, GA 303413717
7704885705 or 1800CDC1311
Fax: 7702346502 E-mail: email@example.com
- The Occupational Safety and Health Administration is responsible for health and safety regulations in the workplace. Secondhand smoke meets OSHA’s criteria for classification as a potential occupational carcinogen. More information is available on the OSHA Web site at http://www.osha.gov/ on the Internet. OSHA can be contacted at:
U.S. Department of Labor
Occupational Safety & Health Administration
200 Constitution Avenue, NW.
Washington, DC 20210
- The National Institute for Occupational Safety and Health conducts research related to secondhand smoke, evaluates work sites for possible health hazards, and makes safety recommendations. NIOSH recommends that secondhand smoke be regarded as a potential occupational carcinogen and that exposures to secondhand smoke be reduced to the lowest possible levels. More information is available on the NIOSH Web site at http://www.cdc.gov/niosh/homepage.html on the Internet. NIOSH can be contacted at:
Hubert H. Humphrey Bldg.
200 Independence Avenue, SW.
Washington, DC 20201