Even if you are well into middle age, giving up cigarettes will greatly reduce your risk of getting cancer, according to UK researchers.

Analysis of two British studies one conducted in 1950 and one in 1990 has shown that individuals who stopped smoking before middle age reduced their risk of lung cancer by more than 90 per cent. Stopping in middle age halved the risk of getting cancer by age 75.

The study also provided useful information about the pattern of smoking in the UK. Between 1950 and 1990, the number of male smokers fell by half. Among people aged 50 or older, the number of former smokers is double the number of current cigarette smokers in the UK.

According to the researchers, the data indicate that, in the first half of the 21st century, death from lung cancer will decline. However, the authors warn that the extent to which the figures rise again will be linked to the extent to which young people become cigarette smokers over the next few decades (BMJ, 2000; 321: 323-9).

However, keeping young people from smoking or being affected by passive smoking may be harder that we realise, if another new study is to be believed.

Researchers from the Massachusetts Department of Public Health have uncovered evidence that cigarette manufacturers, in a bid to make smoking more socially acceptable (but not necessarily safer), are using chemical additives in their products to alter the perception of second hand smoke.

Using code names such as 'Project Stealth' and 'Project Ambrosia', cigarette manufacturers have secretly tested and obtained patents on ingredients that make it more difficult for non smokers to detect second hand smoke.

The study comes on the heels of a US federal court decision to revoke a state law in Massachusetts requiring tobacco companies to list all cigarette ingredients in order, from most to least.

Since the 1980s, research has been ongoing in the tobacco industry to find ways to lower the visibility, aroma, irritation and actual level of secondary smoke. Little money, if any, has been put towards testing whether the resulting products were also reducing the risk of disease (Tobacco Control, 2000; 9: 283-91).