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Secondhand Smoke. Secondhand smoke (SHS) is a mixture of 2 forms of smoke that come from burning tobacco: Sidestream smoke – smoke from the lighted end of a cigarette, pipe, or cigar Mainstream smoke – the smoke exhaled by a smoker.
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Secondhand smoke (SHS) is a mixture of 2 forms of smoke that come from burning tobacco: • Sidestream smoke – smoke from the lighted end of a cigarette, pipe, or cigar • Mainstream smoke – the smoke exhaled by a smoker
Sidestream smoke has higher concentrations of cancer-causing agents (carcinogens) than mainstream smoke. And, it has smaller particles than mainstream smoke, which make their way into the lungs and the body’s cells more easily.
Why is secondhand smoke a problem? • Secondhand smoke is classified as a “known human carcinogen” (cancer-causing agent) by the US Environmental Protection Agency (EPA), the US National Toxicology Program, and the International Agency for Research on Cancer (IARC), a branch of the World Health Organization.
Secondhand smoke causes cancer • Tobacco smoke contains more than 7,000 chemical compounds. More than 250 of these chemicals are known to be harmful, and at least 69 are known to cause cancer.
肝母細胞瘤 • IARC reported in 2009 that parents who smoked before and during pregnancy were more likely to have a child with hepatoblastoma. This rare cancer is thought to start while the child is still in the uterus. Compared with non-smoking parents, the risk was about twice as high if only one parent smoked, but nearly 5 times higher when both parents smoked.
breast cancer • Both mainstream and SHS have about 20 chemicals that, in high concentrations, cause breast cancer in rodents. And we know that in humans, chemicals from tobacco smoke reach breast tissue and are found in breast milk.
One reason the link between SHS and breast cancer risk in human studies is uncertain is because breast cancer risk has not been shown to be increased in active smokers. One possible explanation for this is that tobacco smoke might have different effects on breast cancer risk in smokers and in those who are exposed to SHS.
Findings on smoking, secondhand smoke, and health • SHS kills children and adults who don’t smoke. • SHS causes disease in children and in adults who don’t smoke. • Exposure to SHS while pregnant increases the chance that a woman will have a spontaneous abortion, stillborn birth, low birth-weight baby, and other pregnancy and delivery problems.
Babies and children exposed to SHS are at an increased risk of sudden infant death syndrome (SIDS), acute respiratory infections, ear infections, and more severe and frequent asthma attacks. • Smoking by parents can cause wheezing, coughing, bronchitis, and pneumonia, and slow lung growth in their children.
SHS immediately affects the heart, blood vessels, and blood circulation in a harmful way. Over time it can cause heart disease, strokes, and heart attacks. • SHS causes lung cancer in people who have never smoked. Even brief exposure can damage cells in ways that set the cancer process in motion.
Chemicals in tobacco smoke damage sperm which might reduce fertility and harm fetal development. SHS is known to damage sperm in animals, but more studies are needed to find out its effects in humans. • There is no safe level of exposure to SHS. Any exposure is harmful.
Many millions of Americans, both children and adults, are still exposed to SHS in their homes and workplaces despite a great deal of progress in tobacco control. • On average, children are exposed to more SHS than non-smoking adults.
The only way to fully protect non-smokers from exposure to SHS indoors is to prevent all smoking in that indoor space or building. Separating smokers from non-smokers, cleaning the air, and ventilating buildings cannot keep non-smokers from being exposed to SHS.
