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Third-hand smoke: Touching a smoker’s clothes can raise cancer risk, study warns

The dangers of secondhand smoking have been known for decades, but now scientists are warning of a new threat: third-hand smoke.

A study in the US found that even handling a cigarette smoker’s clothing is enough to expose people to dangerous levels of cancer-causing chemicals.

Passive smoking is when exhaled vapors or the smoke from the end of a cigarette is inhaled by someone else.

Third-hand smoke occurs when particles from a cigarette seep into materials such as hair, clothing and furniture and carpets.

Government researchers at the Berkeley Lab in California conducted a series of experiments on humans and mice.

In one study, three volunteers who did not smoke were asked to wear the clothes of a heavy cigarette user for three hours.

Tests showed that after the experiment, they had up to 86 times higher levels of toxins known as NNK and NNN in their urine.

In another study, researchers exposed the same carcinogens to human lung tissue and showed that they can cause DNA damage — which is one of the causes of cancer.

US researchers say just handling a smoker's clothes is enough to increase cancer risk

US researchers say just handling a smoker’s clothes is enough to increase cancer risk

According to a 2006 report by the US Surgeon General, secondhand smoke increases the risk of lung cancer in non-smokers by 20 to 30 percent.

But less is known about the dangers of third-hand smoke, and fewer studies have been conducted in the area.

The California government-run Berkeley Lab first established in 2010 how smoking leaves microscopic toxic chemicals on surfaces.

But now, for the first time, they have demonstrated the “potential health effects of third-hand smoke.”


Third-hand smoke consists of particles of nicotine and other chemicals that precipitate from the smoke and into surfaces and materials.

In addition to residual nicotine, third-hand smoke contains cotinine and NNK.

Cotinine is a byproduct of nicotine that is created when it is metabolized. It is a known carcinogen.

NNK, another by-product of tobacco smoke, is considered a particularly potent carcinogen.

There is some evidence that the chemical could damage DNA, encouraging the development of cancer.

Together, these substances can also interact with other air pollutants to form new, additional carcinogens.

The latest study is published in the journal Environmental Science and Technology.

In one experiment, mice were exposed to doses of NNK and NNN, another cancer-causing agent found in tobacco, on their skin.

Urine tests showed high levels of both chemicals in their system, suggesting that skin contact could lead to the compounds getting into their bodies.

Even after the team stopped exposing the mice to the chemicals, they continued to build up in their bodies for a week.

They then tested in the lab how the chemicals interact with human lung cells to see how likely they are to cause cancer.

Contact with the chemicals led to DNA damage – which may be a critical factor in cancer development.

In the third experiment, three volunteers wore long-sleeved T-shirts and pants who had been exposed to cigarette smoke for 30 days, at concentrations comparable to those found in a pack-a-day smoker’s home.

The volunteers were non-smokers and were not exposed to smoke at home or at work.

They wore the clothes for three hours and exercised enough to sweat for thirty minutes an hour.

Urine samples were collected before exposure and eight hours after the start of exposure

Each participant also completed the three-hour experiment in their normal clothes to establish a baseline.

The experiment was conducted in a room where the air was recycled almost once a minute to ensure the chemicals were absorbed through the skin rather than volunteers breathing them in.

Researchers found that levels of the chemical were 86 times higher in the samples taken after wearing the smoke-stained clothing.

Lead author Dr Xiaochen Tang, a researcher at the Berkeley Lab, said: ‘Nicotine is released in large quantities during smoking and coats all interior surfaces, including human skin.’

Finally, researchers measured the levels of NNK and NNN in the air from 37 smoking homes and 19 non-smoking homes.

The homes of the smokers found had more than the “non-significant risk levels” set by the California Office of Environmental Health Hazard Assessment.

Levels were negligible in non-smoking homes.

Author Professor Neal Benowitz, a medic at the University of California, San Francisco, said: “These findings illustrate the potential health effects of third-hand smoke, which contains not only TSNAs but hundreds of other chemicals, some of which are also known to be carcinogenic.” .

“Next steps for this research will examine in more detail the mechanisms of adverse health effects associated with tobacco and cannabis residues, effective remediation strategies and translation of scientific findings to tobacco control practices.”

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