Reducing smoking 'is not enough'
Smoking causes cancer
The only way for smokers to avoid exposure to significant levels of cancer-causing substances is to quit completely, research has found.

A team from the University of Minnesota found that smokers who cut their cigarette consumption are exposed to lower amount of a potent carcinogen.  However, the drop is not proportional to the reduction in the number of cigarettes smoked.

The study is published in the Journal of the National Cancer Institute.


There is no safe level of smoking.

Amanda Sandford

Cigarette smoking is the cause of 90% of the world's lung cancer cases - but it is not known whether smokers who reduce the number of cigarettes smoked per day also decrease their risk of lung cancer.
The Minnesota team set out to answer this question by measuring the metabolites of a specific tobacco carcinogen in the urine of smokers who were taking part in a programme to cut their consumption.
The carcinogen, NNK, has been heavily linked with lung cancer.
The volunteers cut their cigarette consumption in stages, and provided urine samples at regular intervals. Overall, their urine contained lower levels of NNK metabolites by the time they had significantly cut back on their habit.

However, the magnitude of the reduction was generally less than the reduction in cigarettes smoked per day.

Even when smokers reduced their cigarettes per day from a mean of 24.7 at the beginning of the study to 2.60 at week 12 (a reduction of 90%), the average level of metabolite concentration in their urine was only reduced by 46%. The researchers, led by Dr Stephen Hecht, suggest that the most likely explanation for the results is that people who are trying to cut back by smoking fewer cigarettes per day alter their smoking behavior by inhaling longer and deeper.

They said: "The results indicate that some smokers may benefit from reduced smoking, but for most the effects are modest, probably due to compensation."

Amanda Sandford, the charity Action on Smoking and Health, told BBC News Online: "The message is quite clear: there is still no substitute for quitting smoking all together.

"There is no safe level of smoking. Even one a day can potentially put you at risk."