I find it frustrating that people are still pointing the finger at Brexit for things like this, when the blame surely lays at the feet of the government. Brexit didn't cause the changes (we didn't have to adopt different standards etc as a direct result of it) the government chose to. Britain is becoming a 'chemical dumping ground' because of a decision made by the Tories. Facilitated by Brexit, maybe, but not a direct result of it.
Blaming Brexit for every bad decision our government makes post 2020 is shifting the blame and responsibility away from the people actually making those decisions in the first place. Hold the government accountable, not the amorphous concept of Brexit.