In discussion of its effects on health, smoking always seems to mean the smoking of ready-made cigarettes (Topic of the week: smoke-free Scotland, Letters, December 2).

Has there been any research to differentiate between this and the smoking of pipes, cigars or roll-ups? Or to compare the effects of different methods of cultivation such as organic as against the use of artificial fertilisers and pesticides?

Pipe tobacco on sale in France is labelled with the proportion of other ingredients (about 20%) that it contains. No doubt tobacco sold in the UK contains similar, though undeclared, additives, which also need looking at.

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Martin Allen