The chemical world is incredibly complex. We have a hard time modeling for two chemicals reacting let alone several different chemicals inside the human body.

This means if I am exposed to a different chemical profile than you a chemical could cause me cancer but not you.

We are still a long way from being able to model these complex interactions between several chemicals we are exposed to.

That is why you setup a regulatory system like the EU where chemicals are first proven safe before being used and quickly pulled even if correlation is showing a trend.

This as opposed to the US system where all chemicals are great until proven beyond a shadow of a doubt to cause enormous problems and even then still allowed or phased out only to be brought back later.