Well,

This question classified as a big question, that explains the continuity of life. Here, the question converted to; what happens if the toxic group of heavy metals is abundant in comparison to the biological essential elements.

Regards

Earth was destined to become a Life Planet, so it was enriched in the lighter, biological elements.

The rare, heavy metals came about into the open by human activities.

Life has developed on the earth crust available. If the composition of the earth crust would be different, life forms would probably have adapted as far as possible. In my view the concept of toxicity is mainly 'being not adapted to that specific element or surroundings'.