Vietnam and the United States have finished the cleanup of dioxin contamination at Da Nang airport caused by the transport and storage of the herbicide Agent Orange during the Vietnam War. The 30 hectares of land cleansed of the toxic chemical were handed over to Vietnam at a ceremony in Da Nang. Large amounts of Agent Orange, which contains dioxin, were stored at Da Nang airport during the war and sprayed by US forces to defoliate the countryside. Dioxin stays in the soil and in the sediment at the bottom of lakes and rivers for generations. It can enter the food supply through the fat of fish and other animals. Vietnamese still suffer from the effects of the spraying. Vietnam says as many as 4 million of its citizens were exposed to the herbicide and as many as 3 million have suffered illnesses caused by it — including the children of people who were exposed during the war.