Smokers are often unaware that the cigarettes have tiny vents in their filters which must not be blocked by fingers or lips, according to a report in Tobacco Control, a journal published by the British Medical Journal publishing group.
When the cigarettes are tested by machines, the filter ventilation dilutes the passage of tar and nicotine by as much as 90 per cent. But people do not smoke like machines and many accidentally block the vents. That can double the yield of harmful carcinogens, the report's authors, from Penn State University in the US, say.
Tobacco Control, BMJ Publishing, BMA Public Affairs Division, 0171 383 6254Reuse content