Large Study Confirms Link Between Secondhand Smoke and Lung Disease
LONDON, UK -- February 18, 2005 -- A large study confirms that secondhand smoke increases the risk of lung cancer and other respiratory diseases (BMJ. 2005 Feb 5; 330 (7486): 277; Epub 2005 Jan 28). In one group, passive tobacco smoke raised the risk of lung cancer by 34%. In another, the increase was 76%. Also, children who were exposed to cigarette smoke in their homes were three times more likely to develop lung cancer once they became adults, the report showed.
Over 300,000 people took part in the study, including 123,479 who provided detailed information about their exposure to secondhand smoke. The participants had never smoked or had not smoked within the last ten years. Controls were matched for sex, age, diet, and country of origin. They were volunteers from ten European countries (Sweden, Denmark, Norway, the Netherlands, United Kingdom, France, Germany, Spain, Italy, Greece) who took part in a multicenter study coordinated by the International Agency for Research on Cancer. Their health was followed for seven years. Ninety-seven developed lung cancer, 20 had other cancers, and 14 died from COPD (chronic obstructive pulmonary disease).
The researchers measured levels of the chemical cotinine, associated with tobacco use, in the blood of the study subjects. They noted that cotinine levels did not correlate with increased lung cancer risk. They believe that this is because cotinine measures the level of tobacco in the last 24 hours, but does not show overall long-term exposure to tobacco smoke. The cotinine levels were used to show that the participants were not current smokers.
Among those exposed to secondary smoke, former smokers who had not touched tobacco for over ten years had a higher risk for respiratory diseases than did those who had never smoked. The researchers speculate that ex-smokers may be more susceptible to secondhand smoke because they already have certain genetic mutations in their cells.
Previous Studies Show Lung Cancer Risk
Another study involving 1,263 lung cancer victims who had never smoked as well as 2,740 controls showed an increased risk of lung cancer among those exposed to secondhand smoke (see Passive Smoke Increases Lung Cancer Risk). However, the current study may be the first that deals with over 123,000 people exposed to secondhand smoke.
The National Institute of Health has also looked at various studies and linked secondhand smoke to lung cancer (Health Effects of Exposure to Environmental Tobacco Smoke). The agency defines secondhand or passive smoke to include sidestream smoke as well as mainstream smoke. Sidestream smoke is smoke that is emitted between puffs of a cigarette, cigar, or pipe. Mainstream smoke is smoke that is exhaled by the smoker. Both sidestream and mainstream tobacco smoke contain at least 60 carcinogens, including formaldehyde, and six developmental toxic substances, including nicotine and carbon monoxide. (Environmental Tobacco Smoke, National Cancer Institute).
Other Problems Caused by Secondhand or Passive Smoke
Over 35,000 U.S. deaths per year from heart disease are due to secondhand smoke, according to the Centers for Disease Control or CDC (Morbidity and Mortality Weekly Report 2002; 51(14): 300-303). Besides lung cancer, respiratory problems caused by secondhand smoke include coughing, chest pain, reduced lung function, increased asthma attacks, and increased rates of pneumonia and bronchitis (American Cancer Society).