I can't prove there is a cancer epidemic, I can only suspect. We have better diagnostic tools now, and we keep better records, so we know when people have cancer where before they just died unexplainedly. Also, people live much older now, so they are naturally more likely to die of cancer than say, TB or malaria. They live long enough to catch diseases of old age we rarely had to deal with before. But we know some cancers are more common percentagewise than they used to be, and we know a lot of our technology is carcinogenic, so it is not unreasonable to assume that cancer rates are intrinsically higher now. And the sheer number of exotic chemicals we release into the environment certainly suggests that at least some contribute to cancer deaths. Any objective observer would only conclude that it is very likely that we are increasing the number of cancer deaths because of our own industrial activities.

It's like the global warming issue, it's very difficult to prove, but it would be idiotic to just ignore the problem because it can't be proven conclusively, especially when some very simple changes could reduce risks substantially at a relatively insignificant cost. Of course, if you are going to be paying the cost, you may not feel that way about it...as with cigarettes and lung cancer. And prevention is always easier, and cheaper, than cure.