Who knows? The problem with autism and cancer as well as a myriad of other rising ailments and diseases is there's no smoking gun. There's a growing movement termed "popular epidemiology". That's where regular citizens, usually in areas where they have a higher rate of some illness, work with scientists to try and find the causes.
The USDA announced it plans to stop gathering data for its Agricultural Chemical Use database, also known as the Pesticide Reporting at National Agricultural Statistics Service (NASS).
The problem with that besides having no measures of the amount of pesticides going into the environment is it diminishes a crucial link of research to rule out pesticide use when trying to pinpoint a cause in those areas that have unusually high clusters of lupus, cancer, autism etc. As it is, there's really no definitive studies proving the safety of new chemicals. Without agricultural reporting there's no way we'll be able to identify any patterns to see if those chemicals are indeed creating health hazards.
You can sign a letter asking the USDA (and Congress) to continue the pesticide reporting program here: