Mercury levels not higher in children with autism

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The blood levels of mercury are similar in children who are developing normally and children with autism, researchers reported today, and do not appear to be contributing to developmental problems.

The study, reported in the journal Environmental Health Perspectives, is part of a dedicated effort by scientists to identify and study possible causes of autism, both environmental and genetic. The study participants are children between ages 24 months and 60 months who are diagnosed with autism as well as children with other developmental disabilities, and children who are developing normally.

The study examined sources of mercury from fish consumption, personal-care products, vaccinations and dental fillings. Researchers found fish consumption was the biggest and most significant predictor of blood-mercury levels. However, the children with autism appeared to have much lower blood-mercury levels than the children who were developing normally. The lower levels may be due to the observation that children with autism are picky eaters and may eat less fish. When controlling for the difference in fish consumption, however, the two groups had similar levels of blood mercury.

The study, however, did not examine whether mercury plays a role in causing autism because mercury was measured after the diagnosis was made.

‘The bottom line is that blood-mercury levels in both populations were essentially the same,’ said the lead author of the study, Irva Hertz-Picciotto, a researcher at the UC Davis, MIND Institute, in a news release. ‘However, this analysis did not address a causal role, because we measured mercury after the diagnosis was made.

‘It’s time to abandon the idea that a single ‘smoking gun’ will emerge to explain why so many children are developing autism. The evidence to date suggests that, without taking account of both genetic susceptibility and environmental factors, the story will remain incomplete.’

-- Shari Roan