Secondhand Smoke

• Secondhand smoke (SHS) is a mixture of 2 forms of smoke that come from burning tobacco:

• Sidestream smoke (支流煙 ) – smoke from the lighted end of a cigarette, pipe, or cigar

• Mainstream smoke (主流煙 ) – the smoke exhaled by a smoker

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• Sidestream smoke has higher concentrations of cancer-causing agents (carcinogens ，致癌物 ) 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.

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Why is secondhand smoke a problem?

• Secondhand smoke is classified as a “known human carcinogen” (人類已知致癌物 )(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.

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致癌物分類• Group 1 Carcinogenic to humans 113 • Group 2A Probably carcinogenic to

humans  (高度可能的人類致癌物 ) 66 • Group 2B  Possibly carcinogenic to humans

(可能的人類致癌物 ) 285 • Group 3 Not classifiable as to its

carcinogenicity to humans  (未歸類 )   505 • Group 4 Probably not carcinogenic to

humans  (高度不可能的人類致癌物 )     1

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Secondhand smoke causes cancer09273902

• Tobacco smoke contains more than 7,000 chemical compounds (化合物 ). More than 250 of these chemicals are known to be harmful (有害的 ), and at least 69 are known to cause cancer.

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肝母細胞瘤 • IARC reported in 2009 that parents who

smoked before and during pregnancy (妊娠 ) 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.

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breast cancer

• Both mainstream and SHS have about 20 chemicals that, in high concentrations, cause breast cancer in rodents (齧齒類 ). And we know that in humans, chemicals from tobacco smoke reach breast tissue and are found in breast milk (母乳 ).

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• 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.

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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 (自發流產 ), stillborn birth (死胎 ), low birth-weight baby, and other pregnancy and delivery problems.

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• Babies and children exposed to SHS are at an increased risk of sudden infant death syndrome (SIDS) (嬰兒猝死症 ), acute respiratory infections (急性呼吸道感染 ), ear infections, and more severe and frequent asthma (氣喘 ) attacks.

• Smoking by parents can cause wheezing (呼吸喘息聲 ), coughing, bronchitis (支氣管炎 ), and pneumonia (肺炎 ), and slow lung growth in their children.

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• SHS immediately affects the heart, blood vessels, and blood circulation in a harmful way. Over time it can cause heart disease, strokes (中風 ), and heart attacks (心臟病 ).

• 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.

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• Chemicals in tobacco smoke damage sperm (精子 ) which might reduce fertility (生殖力 ) and harm fetal development (胎兒發育 ). 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.

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• 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.

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• 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.

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