Low Levels of Mercury Unlikely to Cause Autism
Low levels of mercury are not a likely cause of autism according to a new study in the online scientific journal PLoS ONE. These findings are further evidence to refute the notion that mercury can be linked to autism, a theory that has led to some parents trying various experimental biomedical treatments for their children in the hope that, if a child “excretes” mercury, he or she will improve or might even be “cured” of autism. Some have even said that autism is mercury poisoning and argued that mercury in vaccines played a part in creating an “autism epidemic” and that some children have difficulties excreting mercury, which is therefore thought to “build up” in their systems.
As Steven Novella, M.D., a clinical neurologist, writes, mercury is indeed a neurotoxin but “toxicity is all about dose, so the question is are children being exposed to mercury in high enough dose to cause toxicity.” To understand the effects of mercury on children, one has to take samples from actual children and analyze them, rather than just looking at the effects of mercury in a petri dish.
In the new study, Barry Wright and other British researchers looked specifically at mercury levels in urine to study how mercury works in the body. The researchers enrolled 54 children with autism spectrum disorders, 121 healthy children who attended mainstream schools, 34 who attended special schools for learning disabilities and 42 siblings of autistic children. They found that the mercury levels did not differ in the urine of autistic children versus that of controls.
The theory about a link between autism and mercury has caused much heated debate and Wright and the other researchers were careful to emphasize that their sample size for the study was not large and that they could not conduct 24-hour urine collections because of the difficulties of doing such with some autistic children.
Still, the study provides further valuable evidence that mercury is not a cause of autism, along with earlier studies including one in 2008 that found that autism rates still rose even after the mercury-based preservative thimerosal was removed from the routine children’s vaccine schedule in 2001 – 2002. As Novella notes, it is now a decade after thimerosal was removed and autism rates have continued to climb, at least in some part due to changes made in the DSM criteria in the 1980s. The causes of autism are yet unknown but it is increasingly unlikely that mercury is one of them.
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