Chemical Runoff and Invisible Poisons

Plastic is the visible crisis, but chemical pollution may be even more damaging. Agricultural runoff carries nitrogen and phosphorus from fertilizers into rivers and eventually the sea. Industrial discharge adds heavy metals like mercury, lead, and cadmium.

These chemicals bioaccumulate — they concentrate as they move up the food chain. A tiny organism absorbs a trace of mercury; a small fish eats thousands of those organisms; a tuna eats hundreds of small fish.