There has always been a risk to health of permanent dye. However, putting it into context, my father died of bladder cancer at the age of 78. He had been in an industry using dye. Anybody in the engineering of cars, aeroplanes, has the same risk.
Hmmm..... how big a risk? Along with toxic exhaust fumes, food and drink (not to mention the additives), sedentary lifestyle, smoking, drinking, cheese, bacon, tea, coffee, suncream, medication, industrial pollution, types of clothing, cosmetics....etc, etc.
How do they whittle it down to a specific cancer being caused by hair dye???!
Apparently the risk applies to permanent dyes and the risk is higher if you use a dark hair dye (like me). However I use Loreal Casting Creme gloss which is classed as 'semi-permanent' - I don't know if that makes any difference?
Most people I know dye their hair. How big a risk do you think this is?