New Zealand smokers are exposed to much more nicotine from cigarettes than are Australians, possibly because of a preference for high-nicotine brands on this side of the Tasman.
The results come from a tobacco industry study, which also found New Zealand smokers are exposed to the greatest average amount of tar out of 5703 smokers in eight countries.
Nicotine is the addictive part of tobacco smoke, and tar is an irritant thought to be a major cause of lung cancer.
New Zealand researchers are lobbying MPs to make tobacco companies cut the nicotine level, eventually to the level where tobacco will not be addictive.
In the study by international company British American Tobacco, researchers tested 80,000 butts supplied from smoked cigarettes by smokers in eight countries. Fifteen cigarette brands were tested in each country, to reflect the range available.
The study was published online by the journal Regulatory Toxicology and Pharmacology.
New Zealand smokers sucked out 1.62mg of nicotine a cigarette, the second-highest amount and far more than Australians' 1.36mg.
The variations between countries partially mirror the differences in the amounts of nicotine sucked out of cigarettes in each country in research using smoking machines.
This may in part reflect different kinds of tobacco leaf used at different factories. But this is unlikely to account for the transtasman disparity because much of New Zealand's tobacco supply comes from factories in Australia, although one factory still operates in Wellington.
Christchurch public health specialist Dr Murray Laugesen said Australian smokers' lower nicotine exposure might be due to their greater preference for lower-nicotine brands, or because New Zealanders might be "sucking cigarettes more intensively".
The Commerce Commission in 2008 established a voluntary approach to removing the adjectives "light" and "mild" from tobacco packaging, after tobacco control campaigners complained that they implied a safer form of smoking, when all tobacco smoking was harmful.
The terms have generally been replaced by colour differentiation on the packaging or new descriptive words.
Dr Laugesen said New Zealand smokers being at the top end for nicotine exposure suggested smoking was more addictive in this country.
The nicotine content of tobacco is not regulated in New Zealand, although the Smoke-free Environments Act permits the Government to make regulations to control tobacco's "harmful constituents".
