I think that's a bit unfair. Sure, we can play semantics and claim it's technically incorrect to say "smoking causes cancer" because if it did everyone who smokes would get cancer, and that isn't the case.

However, we are aware of quite a few known, and many probable, carcinogens.[1][2] Among women, breast cancer comprises 60% of alcohol-attributable cancers.[3] And to support the claim that certain foods, when prepared in certain ways, can become carcinogenic take a look at the research on Heterocyclic amines,[4] and acrylamide.[5]

1. http://www.cancer.org/cancer/cancercauses/othercarcinogens/g...

2. http://en.wikipedia.org/wiki/List_of_IARC_Group_1_carcinogen...

3. http://onlinelibrary.wiley.com/doi/10.1002/ijc.21903/abstrac...

4. http://en.wikipedia.org/wiki/Heterocyclic_amine#Heterocyclic...

5. http://en.wikipedia.org/wiki/Acrylamide#Toxicity_and_carcino...

Waiting for a strong causal link, especially when there is a high level of statistical relationships, can mean we might be waiting too long to take serious action.

If repeated studies show strong associations, like say between cigarettes and cancer, it would make sense to take some steps to prevent the potential cause.

Well, carcinogen is one those things that has been known for decades causing cancer. And yes, human-being can make the difference whether they have those unnatural carcinogens or not.

There are plenty of "natural" carcinogens too. Avoiding carcinogens may reduce your cancer risk, restricting yourself to things that are "natural" won't.