is the increase in concentration of contaminated substances or toxins up in the food chain.

The correct option is A Biomagnification
Biomagnification is the increasing concentration of a substance, such as a toxic chemical, in the tissues of organisms at successively higher levels in a food chain. As a result of biomagnification, organisms at the top of the food chain generally suffer greater harm from a persistent toxin or pollutant than those at lower levels.
Bioaccumulation refers to the accumulation of a toxic chemical in the tissue of a particular organism. Bio pollution is the impact of humanity's actions on the quality of aquatic and terrestrial environment.