Professor Chris Exley has spent the last years studying the effects of aluminium on the human body. He has already establised the link between Aluminium and Alzeimer's disease (see the post before this). He has now conclusively shown that aluminium deodrants do cause breast cancer. This is simply because the aluminium salts stop the sweat excreting aluminium - sweating is extremely important and shouldn't be stopped. Sweating is a natural bodily function - there is a reason why we sweat! One is to remove toxins. Can you imagine every day - stopping the toxins escaping - the toxins build up near the breast tissue, which then turn cancerous.
Luckly there are deodrants which don't have aluminium - they tend to be organic but I have found a reasonable one by a Japanese company which actually works really well at stopping odours. It is called Bionsen.
Here is a link to the professor's article.