Cigarette smoke or other tobacco smoke.
It is harmful for the people nearby and on the whole the environment too. Inhaling of tobacco smoke by non-smokers is called passive smoking or second-hand smoking.
Nicotine, carbon monoxide, carbon dioxide, carbon particles and other harmful chemicals are present in the smoke. If inhaled in big quantities they harm the health of people.
Passive smoking can cause cancer, lung infections and other dangerous diseases. It is harmful to children and pregnant women. Carbon monoxide is dangerous and it goes into the blood. CO is a poison.
Smoking causes damage to brain and nerves also by weakening them. For passive smokers too this applies.
The smell from mouths of smokers often causes discomfort to others standing very close to them. The various governments have banned smoking in public places like restaurants, airports, colleges, hospitals etc. There are special smoking regions for smokers.
It is very much necessary for all of us to breathe in fresh and clean air for some time each day. That cleans up the bad effects of passive smoking.