Only a complete mangling of the English language would translate that into No.
What he said was yes, it’s extremely likely that’s the case, but he’s not gonna give an unqualified yes because it’s still a very high percentage. They can’t point to any individual case and say that this person wouldn’t have cancer if he has been eating in Europe.
I agree with the gist of your remark but the question was "can be said with certainty...", which is, indeed very difficult for a scientist to ever do. The "could reach" is also weird right?
The scientist is specifically trying to avoid the trap of a "gotcha question" while answering accurately that the most likely outcome of lots of people consuming a carcinogen is that someone got cancer from it.
What he said was yes, it’s extremely likely that’s the case, but he’s not gonna give an unqualified yes because it’s still a very high percentage. They can’t point to any individual case and say that this person wouldn’t have cancer if he has been eating in Europe.