Toxins and other foreign non-food things (heavy metals, plastics, etc.) tend to get quite highly concentrated as you go up a food chain. So a little tiny dose o

Toxins and other foreign non-food things (heavy metals, plastics, etc.) tend to get quite highly concentrated as you go up a food chain. So a little tiny dose of e.g. mercury absorbed by, say, some krill that are then eaten by fish, who are in turn eaten by bigger fish, that are finally caught by fishermen, can result in quite high concentrations by the time we humans eat it. Same with plastics consumed by these molluscs - they feed things which feed things which feed things which feed us, and we end up taking in really quite a lot of plastic as a result.