How just touching a smoker's clothes may raise cancer risk – Scientists

The dangers of secondhand smoking have been known for decades, but now scientists are warning about a new threat — thirdhand smoke.

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

Secondhand smoke is when exhaled fumes or the smoke from the end of a cigarette is breathed in by someone else.

Thirdhand smoke forms when particles from a cigarette seep into materials like hair, clothes and furniture and carpets.

Government researchers at the Berkeley Lab in California carried out 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 cigarettes user for three hours.

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

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

Secondhand smoking is thought to increase the risk of lung cancer in non-smokers by 20 to 30 per cent, according to a US Surgeon General report in 2006.

But less is known about the dangers of thirdhand smoke, with fewer studies conducted in the area.

The Government-run Berkeley Lab in California team first identified how smoking leaves microscopic toxic chemicals on surfaces in 2010.

But now they have shown the ‘potential health impacts of thirdhand smoke’ for the first time.

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

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

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

Even after the team stopped exposing the mice to the chemicals, they continued to accumulate in their bodies for another week.

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

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

In the third experiment, three volunteers wore long-sleeved t-shirts and trousers that had been exposed to cigarette smoke for 30 days, at concentrations similar to those found in the home of a pack-a-day smoker.


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