Health effects of tobacco

Tobacco products, especially when smoked or used orally, have negative effects on human health, and concerns about these effects have existed for a long time. Research has focused primarily on cigarette smoking.

Tobacco smoke contains more than 70 chemicals that cause cancer. It also contains nicotine, which is a highly addictive psychoactive drug. When tobacco is smoked, nicotine causes physical and psychological dependency. Cigarettes sold in underdeveloped countries tend to have higher tar content, and are less likely to be filtered, potentially increasing vulnerability to tobacco smoking–related diseases in these regions.

According to the World Health Organization (WHO), "[Smoking and oral] Tobacco use is the single greatest cause of preventable death globally." As many as half of people who smoke tobacco or use the substance orally die from complications related to such use. The WHO estimates that each year in total about 6 million people die from tobacco-related causes (about 10% of all deaths) with 600,000 of these occurring in non-smokers due to second-hand smoke. It is estimated to have caused 100 million deaths in the 20th century. Similarly, the United States Centers for Disease Control and Prevention describes smoking tobacco and oral use of tobacco as "the single most important preventable risk to human health in developed countries and an important cause of premature death worldwide." Currently, the number of premature deaths in the U.S. from tobacco use per year outnumber the number of workers employed in the tobacco industry by 4 to 1. According to a 2014 review in The New England Journal of Medicine, tobacco smoking will kill about 1 billion people in the 21st century if current smoking patterns persist, half of them before the age of 70.

China has the largest tobacco smoking population, followed by India. India has highest tobacco chewing population in the world. 154 people die every hour in India due to chewing and smoking tobacco.

Tobacco use most commonly leads to diseases affecting the heart, liver and lungs. Smoking is a major risk factor for infections like pneumonia, heart attacks, strokes, chronic obstructive pulmonary disease (COPD) (including emphysema and chronic bronchitis), and multiple cancers (particularly lung cancer, cancers of the larynx and mouth, bladder cancer, and pancreatic cancer). It also causes peripheral arterial disease and high blood pressure. The effects depend on the number of years that a person smokes and on how much the person smokes. Starting smoking earlier in life and smoking cigarettes higher in tar increases the risk of these diseases. Also, environmental tobacco smoke, or second-hand smoke, has been shown to cause adverse health effects in people of all ages. Tobacco use is a significant factor in miscarriages among pregnant smokers, and it contributes to a number of other health problems of the fetus such as premature birth, low birth weight, and increases by 1.4 to 3 times the chance of sudden infant death syndrome (SIDS). Incidence of erectile dysfunction is approximately 85 percent higher in male smokers compared to non-smokers.

Several countries have taken measures to control the consumption of tobacco (smoking) with usage and sales restrictions as well as warning messages printed on packaging. Additionally, smoke-free laws that ban smoking in public places such as workplaces, theaters, and bars and restaurants have been enacted to reduce exposure to second-hand smoke. Tobacco taxes that increase the price of tobacco products have also been enacted.

In the late 1700s and the 1800s, the idea that tobacco use caused some diseases, including mouth cancers, was initially widely accepted by the medical community. In the 1880s, automation dramatically reduced the cost of cigarettes, cigarette companies greatly increased their marketing, and use expanded. From the 1890s onwards, associations of tobacco use with cancers and vascular disease were regularly reported; a meta-analysis citing 167 other works was published in 1930, and concluded that tobacco use caused cancer. Increasingly solid observational evidence was published throughout the 1930s, and in 1938, Science published a paper showing that tobacco users live substantially shorter lives. Case-control studies were published in Nazi Germany in 1939 and 1943, and one in the Netherlands in 1948, but widespread attention was first drawn by five case-control studies published in 1950 by researchers from the US and UK. These studies were widely criticized as showing correlation, not causality. Follow-up prospective cohort studies in the early 1950s clearly found that smokers died faster, and were more likely to die of lung cancer and cardiovascular disease. These results were first widely accepted in the medical community, and publicized among the general public, in the mid-1960s.