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
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• 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)
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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 nonsmokers, cleaning the air, and ventilating
buildings cannot keep non-smokers from
being exposed to SHS.
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