The shift is caused by a global tobacco industry marketing strategy that targets young people and adults in developing countries' (WHO (Holmes, J.), '10 Facts on the Tobacco Epidemic and Global Tobacco Control'. http://www.who.int).
Although in the last years people are more informed on tobacco risks, smoking is still a very common habit. Policies for reducing tobacco smoke in public areas have been introduced in developed countries and advertisements are becoming more and more aggressive, but people keep on smoking. This happens, mainly, because of the nicotine and other cigarettes' additives, which are addictive. But, as a result of this collective effort, more and more people are trying to quit smoking or have already achieved it. Today, people are more aware of the risks of smoking and they are more sensible with their own health.
Nowadays, people are aware of the harmful effects of smoking, but it was not always that way. The 'Counterblaste to Tobacco', written by King James I in 1604, is one of the first documents warning about the effects of tobacco. In this document we can find quotes like this one: for the Nose being the proper Organ and convoy of the sense of smelling to the braines,  whether that Odour which we smell, be healthfull or hurtfull to the braine (King James I, 'Counterblaste to Tobacco'.1604 (reprinted version from 1905). http://www.laits.utexas.edu). So, as early as 1604, he realized that smoking tobacco was damaging to the nose and for the brain. Smoking became a very common habit at the end of the nineteenth century and especially during the World War I and II. In 1912, Doctor Isaac A. Adler was the first who established a link between cancer lung and smoking and then, in 1929, Doctor Fritz Linking published a statistical study supporting this theory. Later studies confirmed it, specially the 'British Doctor Studies' from 1954, which final conclusions were published in 2004. The main conclusion of the study was that 'a substantial progressive decrease in the mortality rates among non-smokers over the past half century (due to prevention and improved treatment of disease) has been wholly outweighed, among cigarette smokers, by a progressive increase in the smoker nu non-smoker death rate ratio due to earlier and more intensive use of cigarettes' (Doll, R., Peto, R. 'Mortality in relation to smoking: 50 years' observation on male British doctors'. 2004. NCBI, Pub Med. http://www.ncbi.nlm.nih.gov/pubmed).
What is inside cigarettes
'Tobacco smoke contains over 4,000 different chemicals. At least 43 are known carcinogens' (Health Education Authority (UK), 'Harmful Chemicals in Cigarettes & Tobacco Smoke'. http://www.quit-smoking-stop.com). Some of these chemicals are:
Benzene (petrol additive).
Formaldehyde (embalming fluid).
Ammonia (commonly used as a cleaner and in the fertilizers).
Acetone (commonly used as nail polish remover).
Tar (which condenses and sticks to the lungs).
Nicotine (addictive drug).
Carbon monoxide (a toxic gas produced when lightning and smoking cigarettes).
Arsenic (commonly used in rat poison).
Hydrogen Cyanide (gas chamber poison).
All smoking products are harmful; not only cigarettes, but also cigars, menthol cigarettes, light cigarettes (although they are usually advertised as having less nicotine and