Second hand smoke is the exposure of non-smokers to cigarette smoke from people who are smoking around them. It is estimated that over 300 people die from lung cancer each year due to the effects of second hand smoke. Second hand smoke is even more dangerous than smoking directly. Smoking releases 4000 chemicals into the air, the same amount that a person receives from inhaling directly, but as there may be more than one person smoking, second hand smoke can include a greater quantity of these chemicals.

When a smoker burns a cigarette, he usually only inhales for around 30 seconds total, but the cigarette burns for approximately 10 minutes. The non-smoker is therefore also exposed to the cigarette smoke and chemicals for this length of time. Approximately 50 of the chemicals that are in second hand smoke are carcinogens, and it is these that cause cancer.

Figures show that second hand smoke contains two times the amount of tar in inhaled smoke. This is because the smoke in the air burns more slowly. Second hand smoke also contains five times the amount of carbon monoxide, which causes a reduction in the amount of oxygen in the blood.

In addition to death, inhaling second hand smoke has many short-term effects. These include coughing and a sore throat, headaches, increased blood pressure, increased heart rate and eye irritation. Second hand smoke also contributes to a higher risk of heart disease and asthma.

The long-term effects of inhaling second hand smoke include strokes and heart disease. Second hand smoke also causes lung cancer and other related cancers, and it reduces the ability of the body to take in oxygen. Children who are subjected to second hand smoke have a high risk of developing asthma and will likely suffer from other breathing difficulties.

Many countries around the world have banned smoking in all public enclosed spaces to counteract these health risks. Restaurants, bars and nightclubs prohibit smoking on their premises in countries such as Scotland and Ireland, with England following in 2007. In the United States, New York has been smoke free in public places since 2005.

As well as benefits to public health, these bans also have a financial benefit. There are many long-term medical costs associated with smoking and its effects to second hand smoke sufferers. There are also many indirect costs, such as higher insurance premiums, decreased productivity and increased absenteeism. The smoking ban has also made the atmosphere more environmentally friendly, although until car exhaust fumes are also banned, we will never be entirely environmentally clear.