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Mercury Levels Same in Autistic, Other Children

Fish Consumption Predicted Levels Best, Researchers Found
By
WebMD Health News
Reviewed by Louise Chang, MD

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.

Mercury Levels and Autism: Study Details

Triggering the research, Hertz-Picciotto says, is that some researchers have thought children with autism may have higher levels of mercury in their blood because their bodies don't get rid of it it as efficiently as other children and that buildup might be contributing to the problems.

But others have speculated that children with autism may have lower blood levels of mercury because the mercury is sequestered in their brain, she says.

For the study, Hertz-Picciotto and her colleagues compared the blood levels of mercury in 249 children with autism or autism spectrum disorder, in 143 typically developing children and in 60 children with developmental delays other than autism spectrum disorder. Children were enrolled into the study from 2003 to 2006.

The children were part of the Northern California-based Childhood Autism Risks from Genetics and the Environment (CHARGE) study, for which Hertz-Picciotto is the principal investigator. Children aged 24-60 months are enrolled in the study, in which researchers are looking at a variety of exposures and their possible association with the disorder. Some of the participants have autism spectrum disorders, some have other developmental disorders, and a third group of children is typically developing, serving as study controls.

Her team looked at a variety of sources of mercury in the environment, including consumption of fish, use of personal care products that contain mercury such as nasal sprays and earwax removal products, and vaccinations. They also looked at whether children had mercury-based dental amalgam fillings.

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