Many things cause cancer for example chemicals used in agriculture, hormonal contraceptives do too does this mean that you should not invest in healthcare or monsanto. In my opinion as an investment expert your responsibility is to obtain the maximum returns on your portfolio with appreciation as to the risk criteria not making haphazard "ethical" considerations as to whether or not tobacco causes cancer, investment analysts are not cancer experts. If you had invested in Philip Morris in 2010 and maintained your position for the long term you would have a 300% return on your port olio in a low risk consumer staple equity there is a similar case for British American Tobacco
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Thank you very much