People who smoke one pack of cigarettes a day develop an average of 150 extra mutations in their lungs every year, according to a new study that helps explain why smokers have such a higher risk of developing lung cancer.
Other organs were also affected, with the study showing that a pack a day led to an estimated average 97 mutations in each cell in the larynx, 39 mutations for the pharynx, 23 mutations for mouth, 18 mutations for bladder, and 6 mutations in every cell of the liver each year.
“Before now, we had a large body of epidemiological evidence linking smoking with cancer, but now we can actually observe and quantify the molecular changes in the DNA due to cigarette smoking,” Ludmil Alexandrov, co-led author from the Los Alamos National Laboratory said in a statement.
The findings were published this week in the U.S. journal Science.
Cigarettes contain more than 7,000 chemicals, including over 70 known to cause cancer. Although previous studies have associated cigarette smoking with increased risk for 17 different types of cancer, including cancer in tissue not directly exposed to smoke, it has remained unclear how smoking causes cancers.
For this study, researchers looked at over 5,000 tumours, comparing cancers from smokers with cancers from people who had never smoked.
They found particular molecular fingerprints of DNA damage — called mutational signatures — in the smokers’ DNA, and they counted the number of these particular mutations in different tumours.
The study revealed at least five distinct processes of DNA damage due to cigarette smoking.
The most widespread of these is a mutational signature already found in all cancers, which “seems to accelerate the speed of a cellular clock that mutates DNA prematurely,” they said.
“The genome of every cancer provides a kind of ‘archaeological record,’ written in the DNA code itself, of the exposures that caused the mutations that lead to the cancer,” Professor Sir Mike Stratton, joint lead author from the Wellcome Trust Sanger Institute, explained. “Our research indicates that the way tobacco smoking causes cancer is more complex than we thought.”
Tobacco smoking claims the lives of at least six million people every year and, if current trends continue, the World Health Organization predicts more than one billion tobacco-related deaths in this century.
– Smoking –
Smoking is a practice in which a substance is burned and the resulting smoke breathed in to be tasted and absorbed into the bloodstream. Most commonly the substance is the dried leaves of the tobacco plant which have been rolled into a small square of rice paper to create a small, round cylinder called a “cigarette“.
Smoking is primarily practiced as a route of administration for recreational drug use because the combustion of the dried plant leaves vaporizes and delivers active substances into the lungs where they are rapidly absorbed into the bloodstream and reach bodily tissue.
In the case of cigarette smoking these substances are contained in a mixture of aerosol particles and gasses and include the pharmacologically active alkaloid nicotine; the vaporization creates heated aerosol and gas to form that allows inhalation and deep penetration into the lungs where absorption into the bloodstream of the active substances occurs.
Smoking generally has negative health effects, because smoke inhalation inherently poses challenges to various physiologic processes such as respiration. 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. A 2007 report states that each year, about 4.9 million people worldwide die as a result of smoking.
Smoking is one of the most common forms of recreational drug use. Tobacco smoking is the most popular form, being practiced by over one billion people globally, of whom the majority are in the developing world.
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.
Smoking can be dated to as early as 5000 BC, 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. In the 20th century, smoking came to be viewed in a decidedly negative light, especially in Western countries.
The health hazards of smoking have caused many countries to institute high taxes on tobacco products, run ads to discourage use, limit ads that promote use, and provide help with quitting for those who do smoke.
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— Voice Of People (@VOP_Today) December 9, 2016
(Different agencies we mention above contributed for this report “People who smoke one pack of cigarettes a day causes 150 mutations in lung cells each year, study”, edited to fit the style of the page, added additional material and illustrations by Alad Von Alad via VOP)