The research was done in the valley and the results have produced strong reactions.
No matter where you may live in the Valley you're never too far from farmland... or plots where pesticides are used.
Researchers with the USC study interviewed 335 older men in the Valley. None of them worked in the fields but more than half the group had prostate cancer.
Myles Cockburn, USC researcher said, "In general, people with prostate cancer in our study were more likely to live in an area where the specific chemicals and pesticides we identified had been sprayed much more likely than the people who didn't have prostate cancer."
The study looked at organochlorine pesticides, captan and methyl bromide.
Teresa DeAnda said, "I think people should be mad."
DeAnda heads Californians for pesticide reform. She lost her father and uncle to prostate cancer. Both worked the fields. DeAnda says the USC study was long overdue.
"We're surrounded by agriculture where so many different types of pesticides are applied," said DeAnda. "Sometimes different types of pesticides on the same day and we just don't even know what's being sprayed out there."
But Manuel Cunha of the NISEI Farmers League says the study was flawed.
Cunha said, "Just to make that assumption of looking at some research and looking at older people and where they live and where they work, to make that assumption to me is just wrong."
Cunha says a more thorough scientific study is needed. But Cockburn says research tends to imply pesticide drift remains a problem here.
"We're not spraying these things exactly where we expected we're spraying," said Cockburn. "Otherwise people who live in nearby residences shouldn't be affected."
Cunha said, "The way it sounds, no, it's just like we just go out and just spray it and it flies all over the place. No it's not done at all."
Cunha adds homeowners can often expose themselves to pesticides when using products in their yard.