By Emily Fancher

As the number of children with autism in California continues to multiply, so too are the questions about what has caused the rise.

Meantime, some health and education experts question the validity of the statistics that point to the increase in caseload.

One in every 250 children in the state is autistic and from 1998 to 2002, the population of autistic children served by the state doubled.

"It's significantly higher than we ever thought it would be 10 years ago," said Ron Huff, senior psychologist for the California Department of Developmental Services.

He said that Massachusetts and Atlanta have seen rises as well as countries such as Japan, Great Britain and Canada. A neurological disorder, autism comprises a spectrum ofdevelopmental problems that range from mild to severe, often marked by little or no speech, emotional volatility and poor social skills.

Michael Warych, a special education manager for the California Department of Education, said it's possible the rise is due to kids being misdiagnosed as autistic because they're speech impaired or emotionally disturbed.

Dr. Bryna Siegel, director of the autism clinic at UCSF, believesthat some children with speech and language disorders who aren't actually autistic are being misdiagnosed. "I actually think the availability of treatment dollars is drivingthe diagnosis," Siegel said.

Allan Lloyd-Jones, special education consultant for the California Department of Education, believes that lumping Asbergers and Pervasive Developmental Disorders into autism figures has affected statistics. Ten years ago there were 4,394 autistic students in the state, now there are 24,943, but 10 years ago students with Asbergers and PDD weren't countedas autistic, he said.

Robert Hendren, executive director of the MIND Institute at UCDavis, which was created by the California legislature to study the causes of autism, said that the rise may be due autistic children formerly being diagnosed as mentally disabled in the past. "We're diagnosing people differently now than we did 10, 20, 30years ago," he said.

Another theory is that the rise is due to more autistic children moving to the state, but Hendren said there's no proof of this. Hendren said most researchers at MIND are studying a possiblegenetic link to the disorder but that an environmental factor may cause defective genes. There may also be a link to autoimmune function since one-third of families with an autistic child have a history of autoimmune problems.

One possible theory is that vaccines with a preservative containing mercury or pollutants in the environment are causes. "Mercury is very toxic to the immune system and we have more in our environment now," said Hendren, who has also been studying a synthetic compound in styrofoam, pesticides and other chemicals, he said.

Francine Goodwin of Mountain View's son Scott, 7, goes to Wings inSan Mateo believes his autism may have been caused by the mercury in the vaccines given to her son. She's eager for researchers to find the cause, but no one can predict where that will be. "There's still a lot of research that has to be done," said Huff.