BIOACCUMULATION AND BIOMAGNIFICATION
Animals can acquire fat-soluble toxic substances through air, water, or food sources. The substances build up in the tissue of the animal over its lifetime if it has continued exposure; the lifetime accumulation is stored in fatty tissue.
Top predators living in ecosystems contaminated with persistent, fat-soluble toxic substances such as mercury or DDT will have much higher levels in their flesh than organisms lower on the food chain. Fish advisories often reflect this danger.