Mercury contamination isn't usually a problem with shellfish because they're so near the bottom of the food chain. It's more a problem with big predatory fish l

Mercury contamination isn't usually a problem with shellfish because they're so near the bottom of the food chain. It's more a problem with big predatory fish like tuna, because each level of the food chain concentrates the mercury. However, shellfish are very good at collecting micro-plastics, which is an unknown risk.