Only few smokers are sensitive enough to take the conscious effort of refraining from smoking while in public places. Even worse than that, parents and whoever is smoking inside the house don’t care about the hazards they pose to other innocent lives within the household. Young children, for instance, are especially vulnerable to smoke, making them at high risk for cough, chest and ear infections.
Passive smoking, or secondary smoke as it is sometimes called, is when you inhale air that has been polluted by other people’s smoke. If the room is poorly ventilated, hazardous chemicals contained in the smoke will remain in the room for several hours. If the smoke is thick and the room has ventilation, they can also possibly spread to adjacent rooms.
As far as cancer-producing tar in cigarette is concerned, the concentration of tar is much higher from the flaming end of a cigarette (sidestream smoke) than that of the non-flaming end which is inhaled directly by the smoker (mainstream smoke).  One can only imagine the amount of tar absorbed by the child from a smoker puffing cigarette directly in front of him. A nonsmoker who spends about four hours in a smoky room is equivalent to him smoking one cigarette.
Nonsmokers can also absorb a significant amount of addictive substances from cigarette smoke – the nicotine. The amount of nicotine absorbed by the child is equivalent to the child himself smoking about 30 cigarettes a year if his father smokes, and 50 cigarettes a year if it is the mother who smokes. If both parents smoke, the child can assimilate nicotine equivalent to 80 cigarettes a year. 
Nonsmoking children whose parents smoke in the house are involuntarily exposed to the noxious chemicals of cigarette. The effect of these chemicals is worst at ages 1 to 5 years old when they still spend most of their time with their parents. Coughing, sneezing and chest tightness are common complaints of children exposed to passive smoking. Coughing and sneezing result when the child inhales the smoke, and the airway recognizes it as foreign irritant. The human body’s defense is so efficient that it is equipped with natural reflexes such as coughing and sneezing, as an attempt to expel unhealthy chemicals such as smoke. Chest tightness, on the other hand, is due to those airborne chemicals from smoke that cause airway muscles to tighten, making it difficult for the child to breathe.
Passive smoking can also worsen some of the common childhood diseases such as bronchiolitis, pneumonia, laryngitis, flu, pharyngitis, sinus infection, ear infections, middle ear blockage and fluid accumulation, colds, and eye irritation. Inhalation of passive smoke is also strongly implicated as a risk factor for sudden infant death syndrome (SIDS). Likewise, due to its irritant effect to the airway, passive smoke is a powerful trigger of acute asthma attack in children. Frequent exposure, therefore, can lead to severe and hard to manage asthma attacks.
In adults, the most alarming consequence of passive smoking is the fact that it can cause lung cancer. A study by Ayesha Bryant, et.el, showed that the occurrence of Non-small cell lung cancer (NSCLC) is not uncommon among nonsmokers.  Patients with NSCLC are more likely to be young, female and symptomatic of the illness. Furthermore, nonsmoking women have a 50% increase in their risk for lung cancer if their husbands smoke.
The damage brought about by passive smoking should not be underestimated. Necessary actions should be done to avoid this. Declaring your home a smoke-free zone would be a good start. If family members smoke, they should do it outside the house. If at a restaurant, be sure to sit in a no-smoking area. And if staying in a hotel, always ask for a non-smoking room. Last but not the least; do not be reluctant to courteously ask people around your child at a social gathering to stop smoking. Asking people to stop smoking in a public place is never too much to ask because health is at stake here.
1) What’s In Cigarettes?
2) Ayesha Bryant, et.al. (2007). Differences in Epidemiology, Histology, and Survival
Between Cigarette Smokers and Never-Smokers Who Develop Non-small Cell Lung