Mercury released primarily from coal-fired power plants may be contributing to an increase in the number of cases of autism, a Texas researcher said on Wednesday.

A study to be published on Thursday in the journal “Health and Place” found that autism, a developmental disorder marked by communication and social interaction problems, increased in Texas counties as mercury emissions rose, said Claudia Miller, a family and community medicine professor at the University of Texas Health Science Center in San Antonio.

“The main finding is that for every thousand pounds of environmentally released mercury, we saw a 17 percent increase in autism rates,” she said in an interview.

About 48 tons of mercury are released into the air annually in the United States from hundreds of coal-burning plants.

The study looked at Texas county-by-county levels of mercury emissions recorded by the government and compared them to the rates of autism and special education services in 1,200 Texas school districts, Miller said.

“The study shows that there may be a very important connection between environmental exposure to mercury and the development of autism,” she said in an interview.

The U.S. Centers for Disease Control has said it does not know how many cases of autism there are in the country or whether the number has increased, but that the issue is under study.

Some experts estimate there are 1.5 million people in the United States with autism, most of them children, and say the number of cases has risen rapidly in recent years.

“Autism has increased dramatically over the last decade or so and the reasons for that have really stumped the medical community,” Miller said.

“Now we think that due to the rising exposures in pollutants like mercury, they may be at the root of some of these cases,” she said.

The Bush administration this week ordered power plants to cut mercury pollution by 50 percent within 15 years, but environmentalists said the action fell short of what was needed. They have called for a 90 percent cut in mercury emissions.

“This research has implications for toxic substance regulation and prevention policies,” said Raymond Palmer, an autism expert at the San Antonio school who helped in the study.

“Policies regarding toxic release of mercury and the incidence of developmental disorders should be investigated,” he said.