How did UK cigarette makers reduce tar to 10 mg or less?

EDITOR—To try to reduce the harm caused by cigarette smoking, the European Commission established maximal values for tar (10 mg), nicotine (1 mg), and carbon monoxide (CO; 10 mg) per cigarette, as measured by the International Organization for Standardization (ISO) method, from 1 January 2004.1 The easiest way to reduce yields is by increasing filter ventilation,2 but this allows smokers easily to control the dose of smoke they can obtain, usually to facilitate increased intake from lower yield cigarettes.2 3 We compared yields and design features of 10 cigarette brands sold in the United Kingdom before and after the …