Not sure if you ever noticed or not but roundup does not have a warning label on it. I talked to a farmer friend of mine who told me that you could actualy consume round-up without having any serious side effects. (obviously not advisable) He explained to me that the active substance in round up is said to block a chemical reaction in the plant needed to survive, the chemical it blocks is only found in plants, not humans or animals thats why it is safe.
Let's not forget, they were telling everyone how safe DDT was back in the 50's.