Oct. 19, 2009 -- Blood levels of mercury are similar in children with autism, those with other developmental problems, and those who are developing typically, according to a new study.

''There has been discussion about whether children with autism have high levels [of mercury],'' says the study's lead author, Irva Hertz-Picciotto, PhD, an epidemiologist, professor, and chief of environmental and occupational health at the University of California, Davis, and a researcher at the MIND Institute there.

Hertz-Picciotto cautioned that her recent study does not examine whether mercury plays a role in causing the disorder, which has been the focus of ongoing debate. Major studies of children who were given vaccines with the mercury-containing preservative thimerosal (now phased out of most vaccines given to children) don't find a link between the vaccines and autism, but some organizations led by parents of autistic children doubt those conclusions.

The blood levels in the study were taken after a child had already received a diagnosis of autism, a developmental disorder now believed to affect one in 91 U.S. children and marked by difficulty in communication, social interaction, and learning.

Some took exception with the new study.

''Measuring blood levels of mercury is a useless way to assess chronic damage or pathology from mercury, as it clears the bloodstream relatively rapidly," says Jim Moody, a director for the Coalition for SafeMinds (Sensible Action for Ending Mercury-Induced Neurological Disorders), an organization that investigates the risks of mercury exposure.