WASHINGTON - Medical experts squared off yesterday before a federal panel trying to determine whether a mercury-based preservative formerly found in routine childhood vaccines is behind the rising rate of autism.
Most epidemiologists who testified said they doubted that the preservative, thimerosal, was responsible. But a few toxicologists said they had become more and more convinced of a potential link.
Since 1999, thimerosal has been gradually removed from vaccines given to infants and toddlers in the United States, though it can be found in some, including the flu shot.
Scientists have been unable to identify a cause. Many suggest that the rise is unlikely to have an environmental cause but can be explained by other factors, including rising awareness on the part of parents, doctors and teachers.
Some toxicologists told the panel, convened by the Institute of Medicine, mercury levels are higher in children with autism.
The Institute panel is expected to issue its report in June.