TSNAs in Cigarettes and Cigarette Smoke: What Are They?

Tobacco-specific nitrosamines (TSNAs) are thought to be some of the most potent carcinogens in tobacco products. They are unique to tobacco and present in smokeless tobacco, snuff, cigarettes, and electronic cigarette liquid. Most of the damage comes from cigarettes and cigarette smoke, however, because there are so many smokers around the world.

The IARC (International Agency for Research on Cancer) has identified 8 tobacco-specific nitrosamines in tobacco and tobacco smoke. Two of them have been classified as Group 1 carcinogens, which means they cause cancer in people.

• N-nitrosonornicotine (NNN)
• 4-methyl-N-nitrosamino-1-(3-pyridyl)-1-butanone (NNK)

A metabolite of NNK, NNAL is also a strong carcinogen and has been found in the urine of people exposed to secondhand smoke, whether they smoke or not.

Green tobacco coming out of the field will contain nitrates from fertilizers used in farming, and to a lesser degree, from the earth plants they were grown in. It doesn't contain TSNAs however—at least, not yet.

Nitrates in tobacco leaves are transformed into dangerous tobacco-specific nitrosamines when tobacco (and the nicotine in it) is fermented and cured. Processing can be done in a couple of ways, by air or heat, and the results will produce either high or low levels of nitrosamines.

TSNAs are present in finished tobacco products, which ultimately make their way into smokers' bodies, where they contribute to numerous forms of cancer.

TSNAs are strong carcinogens that are linked to several cancers.

Lung cancer has been shown to be closely linked to NNK, specifically, adenocarcinoma, which is the most common form of lung cancer.

Other cancers associated with TSNAs include:

• Oral cancer
• Esophageal cancer
• Liver cancer
• Pancreatic cancer

There is a growing concern that TSNAs may be associated with cervical cancer because these carcinogens have been found in large quantities in the cervical mucus of women who smoke.

Researchers know that TSNA levels in commercial cigarettes vary greatly, worldwide. The reason for this is multi-faceted. Tobacco type, agricultural conditions in tobacco farming, and how the tobacco is cured once it comes out of the field all play a role in the amount of cancer-causing nitrosamines present in finished tobacco.

Burley tobacco (also known as White Burley tobacco) and the flue-curing method appear to produce the highest amount of TSNAs, according to researchers.

The Family Smoking Prevention and Tobacco Control Act gives the United States Food and Drug Administration the power to regulate tobacco products. Researchers are calling for standards of manufacture that would reduce the levels of highly carcinogenic TSNAs to be put in place for commercial tobacco products.

Burley tobacco is air-cured, which involves hanging tobacco leaves in a barn with good airflow. The tobacco is left to dry slowly over a period of one to two months. Air-curing produces a low sugar, high nicotine tobacco. Cigar and burley tobaccos are air-cured.

Flue-cured tobacco is a process in which fresh tobacco leaves are hung on poles in an enclosed barn and cured with heat of a flue connected to an external firebox. This process cures the tobacco by heat without exposing it to smoke. In the 1960s, the firebox was replaced with a gas-fed heat source. This curing method produces tobacco that is high in sugar content and medium to high nicotine content. Most commercial cigarettes are flue-cured.

Other tobacco-curing methods include:

Fire-curing, where a smoldering hardwood fire is inside the barn with the tobacco. Fire-cured tobacco can take days or weeks depending on the tobacco and what it's being prepped for. Pipe, chew and snuff tobacco are fire-cured. Some cigarettes are also produced from fire-cured tobacco. Fire-cured tobacco is low in sugar and high in nicotine.

Sun-curing involves exposing tobacco leaves to the sun for drying. Used in Mediterranean countries, this method produces what is known as Oriental tobacco. It is low in sugar and nicotine. Turkish cigarettes are 100 percent unblended Oriental tobacco. Cigars, pipe tobacco, snuff, and chew are also made with Oriental tobacco.

The factors that influence TSNAs in tobacco and tobacco smoke can and should be controlled to protect smokers and non-smokers exposed to cigarette smoke as much as possible.

In addition to TSNAs, 10 highly carcinogenic chemicals known as PAHs and aromatic amines are also thought to play a leading role in the risk of the above cancers in people. Both TSNAs and PAHs can be reduced in tobacco products.

To date, science has revealed approximately 70 carcinogenic compounds in cigarettes and cigarette smoke, including 60 that are present in cigarette smoke and at least 16 that reside in unburned tobacco. The IARC lists 10 PAHs, 8 TSNAs, and 45 other carcinogens as potential human carcinogens, and research continues.

Tobacco kills one in five adults around the world today, amounting to approximately 6 million lives lost annually to a cause that is within our control.

If the current course we're on continues, that number is expected to grow to 10 million tobacco-related deaths a year by 2020, with 70 percent of the loss coming from under-developed countries with no tobacco control in place.

Education about the hazards of tobacco use and support for people quitting is key to reversing this trend.

There is no safe level of exposure to cigarette smoke. It is toxic air, and when it settles on surfaces, it creates toxins known as third-hand smoke.

If you are still smoking and want to quit, start by considering the reasons why you should, and then use the resources below to get started with smoking cessation.

• How to Quit Smoking (and make it stick)
• Practical Advice for Nicotine Withdrawal

Also, stop in at our smoking cessation support forum for tips from other ex-smokers who are going through what you are, or have been there and can offer sound advice. You can simply read or join in with discussions taking place. Either way, your determination will be bolstered.

Quitting tobacco takes some work, but the discomforts are temporary. Don't fear smoking cessation. Think of it as a stepping stone to a much better life.