Why was agent orange so controversial?

Answer 1

Mainly, people disagreed with the use of agent orange during the war because it has a bad effect on the health of those in South Vietnam at the time, as it highly increased the risk of cancer and other diseases. Many innocent civilians died because of it. People also disagreed with its usage because of it's harmful effects on the South Vietnamese Jungle, as it destroyed jungle foliage in order to help find Vietcong fighters.

Answer 2

Because of how it's made.

Agent Orange is an equal mixture of two herbicides, 2,4-D and 2,4,5-T. If you have pure forms of both these herbicides you get a nice, non-toxic and EXTREMELY effective plant killer. Roundup has nothing on this stuff. And I'm not kidding about its non-toxicity: the chemical company said you could drink it and a few guys did. They survived the war but died of terrible cancer afterward.

The problem, which no one realized until it was too late, is the second step in making 2,4,5-T - there are three - generates heat and at 160 degrees C it forms a very nasty chemical called TCDD. It causes cancer and several other diseases and it also mutates your DNA so you pass on all sorts of weird birth defects you wouldn't have otherwise.