Answer:
Effects listed as Health Concerns
A 2006 Surgeon General's report stated that secondhand smoking (also called involuntary or passive smoking) can kill, and it concluded that there is no amount of exposure to secondhand smoke that is safe.
Chemicals released in smoking include significant amounts of hydrogen cyanide, benzene, formaldehyde, and carbon monoxide. These are irritants to the respiratory system. Especially in children, these can lead to pneumonia, bronchitis, or aggravation of conditions such as asthma. The contaminants in smoke can be linked to increased risk of cancer, lung disease, and heart disease. Smoking or high exposure during pregnancy has been linked to increased risk of premature delivery, low birth weight, SIDS, mental retardation, learning problems, and attention deficit hyperactivity.
Although the incidence of illness directly related to secondhand smoke is statistically low, the high number of people exposed to it means that tens of thousands of individuals in the US will develop new or aggravated disease symptoms each year. This likely extends to hundreds of thousands worldwide.
Effects Disputed
The 1993 Environmental Protection Agencies linking health concerns to second hand smoke was thrown out by a district judge. The conclusion stated that "The studies showed that for any given nonsmoker, the lifetime risk of getting lung cancer remains small: 4 to 5 in 1000 ordinarily, and 6 to 7 in 1000 if he or she has been living with a smoking spouse."
BMJ did the longest most in depth study and concluded:
"The results do not support a causal relation between environmental tobacco smoke and tobacco related mortality, although they do not rule out a small effect. The association between exposure to environmental tobacco smoke and coronary heart disease and lung cancer may be considerably weaker than generally believed."