Smoking is the combustion of a substance, usually plant material, and the inhalation of resulting fumes. Today, smoking is mostly practiced by rolling the dried leaves of the tobacco plant into a cigarette. Other forms of tobacco smoking include the use of smoking tobacco with a pipe or cigar, or using a bong. Cigarette smokers almost always inhale the smoke; most pipe and cigar smokers do not inhale.
Smoking is primarily practiced as a route of administration for psychoactive chemicals because the active substances within the burnt, dried plant leaves (or other chemical) can vaporize into a gaseous state and be delivered into the respiratory tract, where they are rapidly absorbed into the bloodstream through the lungs and can reach the central nervous system. In the case of tobacco smoking, these active substances are a mixture of aerosol particles that include the pharmacologically active alkaloid nicotine, which stimulates the nicotinic acetylcholine receptors in the brain, and other non-psychoactive chemicals that result from combustion. Other notable drugs inhaled via smoking include tetrahydrocannabinol (from cannabis), morphine (from opium), cocaine (from crack), and methamphetamine. Designer drugs, or "research chemicals", can also be smoked.
Tobacco smoking is the most popular form, being practiced by over one billion people globally, of whom the majority are in the developing countries. Less common drugs for smoking include cannabis and opium. Some of the substances are classified as hard narcotics, like heroin, but the use of these is very limited as they are usually not commercially available. Cigarettes are primarily industrially manufactured but also can be hand-rolled from loose tobacco and rolling paper. Other smoking implements include pipes, cigars, bidis, hookahs, and bongs.
Smoking tobacco harms health, and is among the leading causes of many diseases such as lung cancer, heart attack, chronic obstructive pulmonary disease, erectile dysfunction, and birth defects. Diseases related to tobacco smoking have been shown to kill approximately half of long-term smokers when compared to average mortality rates faced by non-smokers. Smoking is estimated to kill more than seven million people worldwide each year, including 1.6 million non-smokers who die due to passive smoking. A 2023 analysis put global tobacco-attributable deaths at just over seven million for that year. The health risks of smoking have caused many countries to tax tobacco products heavily, publish anti-smoking advertisements, limit or ban tobacco advertising, and help smokers to quit.
Smoking can be dated as early as 5000 BCE and has been recorded in many different cultures across the world. Early smoking evolved in association with religious ceremonies as offerings to deities, in cleansing rituals, or to allow shamans and priests to alter their minds for purposes of divination or spiritual enlightenment. After the European exploration and conquest of the Americas, the practice of smoking tobacco quickly spread to the rest of the world. In regions like India and Sub-Saharan Africa, it merged with existing practices of smoking (mostly of cannabis). In Europe, it introduced a new type of social activity and a form of drug intake which previously had been unknown.
Perception surrounding smoking has varied over time and from one place to another: holy and sinful, sophisticated and vulgar, a panacea and deadly health hazard. By the late 20th century, smoking came to be viewed in a decidedly negative light, especially in Western countries.
Health effects
Smoking is one of the leading preventable causes of death globally and is the cause of over 7 million deaths annually, 1.6 million of which are non-smokers who die due to passive smoking. In the United States alone, about 480,000 individuals die annually due to smoking and a 2004 study estimated that as much as one-third of China's male population will have significantly shortened lifespans due to smoking. Male and female smokers lose an average of 13.2 and 14.5 years of life, respectively.
Currently, the number of premature deaths in the US from tobacco use per year exceeds the number of employees in the tobacco industry by 4 to 1. It has been estimated that tobacco smoking will kill about 1 billion people in the 21st century if current smoking patterns continue, half of them before the age of 70.
At least half of all lifelong smokers die earlier as a result of smoking. The risk of dying from lung cancer before age 85 is 22.1% for a male smoker and 11.9% for a female current smoker, in the absence of competing causes of death. The corresponding estimates for lifelong nonsmokers are a 1.1% probability of dying from lung cancer before age 85 for a man of European descent, and a 0.8% probability for a woman. Smoking just one cigarette a day results in a risk of coronary heart disease that is halfway between that of a heavy smoker and a non-smoker. The non-linear dose–response relationship may be explained by smoking's effect on platelet aggregation.
Among the diseases that can be caused by smoking are vascular stenosis, lung cancer,American Legacy Foundation factsheet on lung cancer ; their cited source is: CDC (Centers for Disease Control) The Health Consequences of Smoking: A Report of the Surgeon General. 2004. heart attacks and chronic obstructive pulmonary disease (COPD). Prenatal exposure to tobacco smoke is associated with a higher risk of attention deficit hyperactivity disorder (ADHD) in children, though it remains unclear whether the relationship is causal or reflects shared genetic and familial factors between parent and child.
Smoking is a risk factor strongly associated with periodontitis and tooth loss. The effects of smoking on periodontal tissues depend on the number of cigarettes smoked daily and the duration of the habit. A study showed that smokers and former smokers had 2.7 times and 2.3 times greater probabilities to have established periodontal disease than non‐smokers, respectively, independent of age, sex, and plaque index; however, the effect of tobacco on periodontal tissues seems to be more pronounced in men than in women. Studies have found that smokers had greater odds for more severe dental bone loss compared to non‐smokers. Also, people who smoke and drink alcohol heavily have much higher risk of developing oral cancer (mouth and lip) compared with people who do neither. Smoking can also cause melanosis in the mouth.
Smoking has been also associated with oral conditions including dental caries, dental implant failures, premalignant lesions, and cancer. Smoking can affect the immune-inflammatory processes which may increase susceptibility to infections; it can alter the oral mycobiota and facilitate colonization of the oral cavity with fungi and pathogenic molds.
Many governments are trying to deter people from smoking with anti-smoking campaigns in mass media stressing the harmful long-term effects of smoking. Passive smoking, the inhalation of tobacco smoke by people in the immediate vicinity of smokers, is a major reason for the enforcement of smoking bans. These are laws enforced to stop individuals from smoking in indoor public places, such as bars, pubs, and restaurants, thus reducing nonsmokers' exposure to passive smoke. A common concern among legislators is to discourage smoking among minors, with some countries increasing the age a person must be to buy cigarettes. In 110 countries, cigarette packaging display graphic health warnings. Tobacco advertising is also sometimes regulated and/or banned to make smoking less appealing.
Despite the many bans, European countries still hold 18 of the top 20 spots and, according to the ERC Research Group, the heaviest smokers are from Greece, averaging 3,000 cigarettes per person in 2007. Rates of smoking have leveled off or declined in the developed world but continue to rise in developing countries. Smoking rates in the United States have dropped by half from 1965 to 2006, falling from 42% to 20.8% in adults.
The relationship between smoking and Alzheimer's disease risk is disputed. A 2010 analysis found smoking increased Alzheimer's risk once studies funded by the tobacco industry (which had tended to report a protective effect) were excluded, while a later pooled analysis of longitudinal cohorts across several countries found no significant association between smoking and dementia, including Alzheimer's disease specifically. While smoking more than 15 cigarettes per day has been shown to worsen the symptoms of Crohn's disease, smoking has been shown to actually lower the prevalence of ulcerative colitis.
Smokers are 30–40% more likely to develop type 2 diabetes than non-smokers, and the risk increases with the number of cigarettes smoked.
In 2021, the WHO reported the leading cause of tobacco-attributable deaths in the European Region was bronchus and lung cancer at 63.5%. Physiology
+The most genotoxic cancer causing chemicals in cigarette smokeCompoundMicrograms per cigaretteEffect on DNA Ref.Acrolein122.4Reacts with deoxyguanine and forms DNA crosslinks, DNA-protein crosslinks and DNA adductsFormaldehyde60.5DNA-protein crosslinks causing chromosome deletions and re-arrangementsAcrylonitrile29.3Oxidative stress causing increased 8-oxo-2'-deoxyguanosine1,3-butadiene105.0Global loss of DNA methylation (an epigenetic effect) as well as DNA adductsAcetaldehyde1448.0Reacts with deoxyguanine to form DNA adductsEthylene oxide7.0Hydroxyethyl DNA adducts with adenine and guanineIsoprene952.0Single and double strand breaks in DNA
Inhaling the vaporized gas form of substances into the lungs is a quick and very effective way of delivering drugs into the bloodstream (as the gas diffuses directly into the pulmonary vein, then into the heart and from there to the brain) and affects the user within less than a second of the first inhalation. The lungs consist of several hundred million tiny air sacs called alveoli (an average of about 480 million in an adult lung) that together provide a very large surface area for gas exchange, often compared to the size of a tennis court. This can be used to administer useful medical as well as recreational drugs such as aerosols, consisting of tiny droplets of a medication, or as gas produced by burning plant material with a psychoactive substance or pure forms of the substance itself. Not all drugs can be smoked, for example the sulphate derivative that is most commonly inhaled through the nose, though purer free base forms of substances can, but often require considerable skill in administering the drug properly. The method is also somewhat inefficient since not all of the smoke will be inhaled.Leslie Iverson, "Why do We Smoke?: The Physiology of Smoking" in Smoke, p. 318 The inhaled substances trigger chemical reactions in nerve endings in the brain due to being similar to naturally occurring substances such as endorphins and dopamine, which are associated with sensations of pleasure. The result is what is usually referred to as a "high" that ranges between the mild stimulus caused by nicotine to the intense euphoria caused by heroin, cocaine and methamphetamines.Leslie Iverson, "Why do We Smoke?: The Physiology of Smoking" in Smoke, pp. 320–21
Inhaling smoke into the lungs, no matter the substance, has adverse effects on one's health. The incomplete combustion produced by burning plant material, like tobacco or cannabis, produces carbon monoxide, which impairs the ability of blood to carry oxygen when inhaled into the lungs. There are several other toxic compounds in tobacco that constitute serious health hazards to long-term smokers from a whole range of causes; vascular abnormalities such as stenosis, lung cancer, heart attacks, strokes, impotence, low birth weight of infants born to smoking mothers. Long-term smokers develop the characteristic set of facial changes known as smoker's face in about 8% of cases.