Washington (AFP)

San Francisco has decided to ban the sale of electronic cigarettes by 2020, in order to prevent young people from vaping. The current scientific consensus is that vaping is probably less dangerous than smoking, but the absolute risks to long-term health are still unknown.

- What do electronic cigarettes contain?

Vaping is the process of inhaling vapors created by high temperature heating of a liquid inside the electronic cigarette.

Most liquids contain nicotine. Nicotine has been well studied for decades: it is addictive and it affects the development of the brain before the age of 25, insists the American government.

In contrast, e-cigarettes do not include many carcinogens found in combustible cigarettes, such as tar.

But the vapor contains fine particles that penetrate the lungs. There are "many potentially toxic substances," concluded a report of the American Academies of Science, published in 2018 at the request of the Congress, which analyzed all published studies.

It includes metals (nickel, lead ...), probably from the coil used to heat the liquid. And additives considered safe in the food industry, but related to lung diseases or not studied in their vaporized form.

It is possible that these substances have long-term toxic effects on the cells of the body. But to be sure, it would require studies over several decades, which do not exist yet.

- Is Vapoter dangerous?

Sold since the mid-2000s, e-cigarettes are relatively new. The researchers therefore have little perspective.

For people who already smoke, it seems that replacing the cigarette with vaping has positive effects: the nicotine would remain, but the substances present in the cigarettes and of which we know with certainty that they are carcinogenic would not be inhaled.

A recent study in the UK published in the New England Journal of Medicine found that e-cigarettes were more effective than patches, gums and other substitutes for quitting.

On the other hand, more and more studies show that young non-smokers who start vaping are more likely to start smoking.

The authorities are therefore worried that the progress of recent years will go up in smoke: in the United States, generations of college and high school students, who smoked less, are now accustomed to nicotine through vaping, likely gateway to tobacco.

- Should it prohibit the sale?

The vaping industry, and its advocates, all say that it is absolutely necessary to prevent young people from vaping. Electronic cigarettes are already banned for sale to people under 18 or 21 in the United States, depending on the state.

But the ban on sales is the worst solution, because it neglects adults who would like to quit smoking.

"Denying these electronic cigarette smokers, who are known to be far less harmful than cigarettes, is a very bad decision," Neil McKeganey, co-director of the Center for Substance Use Research, a British research center, told AFP. partially funded by the industry.

The paradox is that in San Francisco, the sale of alcohol, cigarettes and cannabis will remain legal (for those over 21). Health risks are well known for alcohol (cancers, cardiovascular and digestive diseases, cirrhosis ...) and tobacco (cancers, cardiovascular diseases, chronic respiratory insufficiency ...). As for cannabis, studies have shown its harmful effect on brains still developing, in adolescents and young adults.

In place of a prohibition, stricter control of e-cigarette sales is recommended by the industry.

There is still work: an analysis published Monday in the medical journal Jama showed that half of businesses selling e-cigarettes did not check the age of buyers in California.

? 2019 AFP