Could be any one of them. That's a pretty bad combo. The usage of heavy pesticides and junk food diet didn't help the immune system that's for sure.
I think the key word here is COULD. I know of an autistic child whose mother went to Blockbuster throughout her pregnancy and took the child along with her for the first 2 years of his life. I guess that going to Blockbuster COULD have caused his autism. This is a totally ridiculous and unproven theory; I'm just using absurdity to illustrate absurdity.