Nicotine linked to lung cancer

Nicotine patches help wean smokers off tobacco

Nicotine, the chemical which causes cigarette addiction, could be responsible for some lung cancers, suggest researchers.

While this may concern people using nicotine patches to wean themselves off smoking, experts are keen to point out that the health benefits of giving up would still vastly outweigh the risks - even if the link was true.

Most lung cancers are thought to be caused by other chemicals contained in smoke.

But the latest findings, published in a US journal, suggest that nicotine alone can be converted into a chemical which has the potential to cause tumours.

People should not be scared by this study into avoiding giving up smoking

Dr John Toy

Anti-smoking campaigners are stressing that any risk is likely to be very small.

"This is speculative research - no-one has detected any cases of lung cancer from nicotine in humans," said Clive Bates, director of Action on Smoking and Health.

"The biggest danger is that people will be put off nicotine patches and not use them, even though giving up smoking has a very large benefit to health," he told BBC News Online.

Tumours in mice

Smokers who use nicotine replacement therapy (NRT) are twice as likely to manage to quit as those who attempt to give up unaided, he added.

Lung cancer kills approximately one person in the UK every 15 minutes and about 90% of lung cancers are caused by smoking.

Tar and toxic gases are thought to be the main cancer-causing substances in tobacco smoke.

But researchers at the University of Minnesota Cancer Center in Minneapolis, found that under certain conditions nicotine could be converted into nicotine-derived nitrosamino ketone (NNK) - a known lung carcinogen.

The team found that mice developed tumours in their lungs when given NNK by injection and in their drinking water.

Researcher Steve Hecht also analysed the urine of smokers and former smokers who were using nicotine replacement therapy.

He found that a chemical was present which could possibly change into NNK under acidic conditions, such as in the stomach.

He said the research was still at an early stage but could have implications for the long-term use of nicotine replacement therapy.

'Crucial' to kick habit

The medical director of the Imperial Cancer Research Fund, Dr John Toy, said the research should not put people off trying to give up smoking.

"This research is of course interesting, but it remains important to stress that NRT is only meant to be used in the short and medium-term to help people give up smoking.

"People should not be scared by this study into avoiding giving up smoking, since 50% of people who smoke will die from their habit.

So if we are to reduce the number of people dying from lung cancer in this country, it's crucial that people try to give up smoking, and NRT is a useful way to help do this."

The findings are published in the Proceedings of the National Academy of Sciences.