Dioxins and furans are chemical compounds produced by human activities such as the garbage burning, oil refining, wood burning, fuel combustion in vehicles, electricity production and the chemical industry. Dioxins and furans are also released during fires and volcanic eruptions. They can be carried in the atmosphere far from their place of origin.
More than 90% of human exposure comes from food, 80% from products of animal origin.
Dioxins and furans are hydrophobic, meaning they repel water. Because of this, the dioxins and furans discharged into aquatic environments attach themselves to organic particles and enter the fatty tissue of fish and certain crustaceans. Aquatic organisms can absorb dioxins and furans directly from the water or sediment, or ingest them by eating contaminated prey. The Washington State Department of Health has drawn up a dietary guide advising which fish to eat and how frequently.