Although there are differences between inhaling and not inhaling cigarette smoke, there is no level of cigarette-smoke exposure that can be considered safe or safer. Whether firsthand (taking a drag from a cigarette) or secondhand (being near someone smoking), cigarette smoke has many known negative health effects. According to the American Cancer Society, there are two forms of secondhand smoke: sidestream smoke (smoke that comes from the lit cigarette) and mainstream smoke (smoke exhaled by a smoker). Sidestream smoke has higher carcinogen concentrations and contains smaller particles than mainstream smoke, so the particles make their way into the body's cells more easily.
Cigarette smoke contains more than 7,000 chemicals. Sixty-nine of those chemicals are carcinogens. Hundreds of the chemicals are considered toxic. Four of the cancer-causing chemicals include formaldehyde (used as embalming fluid), benzene (found in gasoline), polonium 210 (a radioactive compound) and vinyl chloride (used to make pipes). Some of the toxic metals are chromium (used in steel-making), arsenic (used in pesticides), cadmium (used for making batteries) and lead.
Smoking cigarettes leads to many negative health effects on the body's systems. Smoking causes asthma, emphysema, chronic bronchitis and pneumonia. Smokers come down with respiratory illnesses that are difficult for the body to fight off and are more likely to lead to hospitalization, compared to non-smokers. The circulatory system is affected greatly--examples include heart attacks, strokes and poor blood circulation in the arms and legs, which for diabetics could result in amputation. According to the 2010 Surgeon General Report, smoking impairs the body's immune system and can damage DNA, leading to cancer of the mouth, nose, throat, lung, stomach, pancreas and bladder, to name a few. Even smoking an occasional cigarette is harmful.
The more secondhand smoke you are exposed to, the higher the level of these harmful chemicals in your body. Children exposed to secondhand smoke have higher incidences of Sudden Infant Death Syndrome (SIDS), ear infections, asthma and lung infections. For a developing fetus, secondhand smoke can cause low birth weight, miscarriage, pre-term delivery and underdeveloped lungs. Children whose mother smoked during pregnancy learn more slowly and perform less well in school. Children and adults exposed to secondhand smoke miss more school and work days and are hospitalized or visit the doctor more often. They are also at risk for high blood pressure, heart disease and cancer.
Not inhaling while smoking can reduce the amount of nicotine absorbed by the body, and possibly reduce the nicotine dependence on cigarettes. It is also possible that not inhaling exposes the lungs to fewer toxins, but this cannot be confirmed. The American Cancer Society warns that wherever smoke touches living cells, it does harm. Smokers who don't inhale are still breathing secondhand smoke, which puts them at risk for many health problems. Smokers who don't inhale but put tobacco to their lips or smoke in their mouths are at an increased risk of oral cancers such as lip, mouth and tongue cancer.