i have large blocks of white on my sleeve and backpiece and highlights all over. the arm is 12 years old, the back is 5. there is also white mixed in with other coloured ink throughout. so i have it all over. i have never had a reaction to it, it was all packed in properly by good tattooers, no reactions and it definately has lasted.
i would be more worried about a family history of cancer, toxins in the environment and our food supply than i am about getting cancer from tattooing. actually i would be more worried about getting cancer from a rotary-pen tattoo machine...but i digress