Why are Vietnam veterans concerned about Agent Orange?

In the 1970's some veterans became concerned that exposure to Agent Orange might cause delayed health effects. One of the chemicals (2,4,5-T) in Agent Orange contained minute traces of 2,3,7,8-tetrachlorodibenzo-p-dioxin (also known as TCDD or dioxin), which has caused a variety of illnesses in laboratory animals. More recent studies have suggested that the chemical may be related to a number of malignancies and other disorders.