According to the Centers for Disease Control, one out of every 150 children is diagnosed with autism. So what's causing it?

Wendy Harnisher said, "Immunizations, the mercury in the immunizations."

Stephanie Veitch said, "We think pollution plays a factor, but nobody knows for sure. A lot people think the vaccines, but nobody knows for sure."

One thing for sure, there is a genetic link but nothing else has been proven. No one knows why autism is on the rise, but some experts say it's not because there are more kids with it but that there is a better method for diagnosing the disorder. Other experts like Dr. Kenneth Bock, who's written a book on autism, said it's an epidemic and the cause is related to environmental factors.

Bock said, "The key issue we are really dealing with here is environmental toxicity, that our kids are being exposed to more and more toxins in various forms, mercury in various forms, mercury emissions. Lead, there's lead in dust and soil, chemicals, all types. All these things together are coming together in these susceptible kids and causing neuro-developmental problems."

A major controversy is whether vaccines are at fault. Prior to 2001, vaccines contained thimersol, a preservative which was 50 percent mercury. The theory is that the mercury weakened children's immune system making them more susceptible to disorders like autism. After 2001, all vaccines, except the flu vaccine, are thimerosol-free. Another controversy is the MMR vaccine for measles, mumps and rubella, which is given to children around their first birthday, the same time signs of autism begin to appear. Some claim that giving three shots at one time is too much for a child, again weakening their immune system. Some experts say that vaccines are getting a bad rap, the timing of symptoms is just a coincidence and not a correlation.

Developmental Behavioral Pediatrician Dr. George Pascual said, "Autism is not an auto-immune disease, so I think that any suspicion about it compromising the auto-immune system because of vaccines, really has nothing to do with autism because autism is not an auto-immune phenomenon."

Nearly all professionals support the need for vaccinations, but some experts recommend separating the measles, mumps and rubella shots.

Bock said, "I do agree that the MMR should be separate because giving three live attenuated or weakened viruses at the same time can be problematic for a certain subset of kids."

Concerns regarding the incidents and causes of autism are still being studied.