Wednesday, October 28, 2009

Mercury in the Blood

Mercury in bottle via usepagov (flickr)
Mercury and autism.  These two words go together as well as matches do in a dynamite factor.  For more than the a decade, a controversy has raged about whether exposure to mercury can cause autism.

Some think that the mercury that used to be contained in vaccines played a role in the rise of autism while others think that mercury is completely harmless and would drink it like Kool-Aid if they could.

Regardless of your opinion about mercury, you have to admit that it is a health risk and it is concerning that our exposure to it from the environment is on the rise.

But do children with autism have a higher exposure to mercury than typical children?  A recent study from the UC Davis M.I.N.D. institute seeks to answer that question.

Blood Mercury Concentrations in CHARGE Study Children with and without Autism

(This study is open access so I suggest reading it for yourself if you are interested)

In this well-designed study, which is part of the larger CHARGE study, researchers looked a group of 452 children to determine whether the subset of children with autism (249) had a higher blood concentration of mercury than did typical children (143), or children with other developmental delays (60).

On average, children with autism had a lower blood concentration (0.19 ug/L) than did typical children (0.28 ug/L).  But, after adjusting the results for environmental exposures to mercury, the children with autism had about the same level (0.26 ug/L) as did the control group (0.24 ug/L).  And, unlike some prior results, the levels of mercury that were found were in line with other national surveys of children.

I don't think anyone should be surprised by this result.  The mercury that is circulating in your blood is there because of your recent exposures to mercury - either from your diet, dental fillings, air pollution, or other sources.  Once it gets into your blood it goes one of two places - either out of your body through the normal channels or it will get stored inside your body.

I think the surprising result here is that children with autism eat that much less fish than typical children do.  I know that there can be food selectivity issues, but I would not have expected the result to have been so pronounced.

The other surprise here is just how much mercury children get from eating fish.  If I remember my childhood correctly, kids aren't that big on eating fish to begin with.  So if the presumably small amount that they eat can cause a large change in the amount of mercury you consume then it might be best to limit your fish intake.  And you thought I was joking when I said to not eat the fish because it might give you autism.

Unfortunately, this study is not going to put to rest the controversy that surrounds mercury and autism because it does not address what some feel is the central question.  Do children with autism have a problem in eliminating mercury from their bodies and does the build up of mercury cause problems that lead to autism?

If this is a problem in (some) children with autism (emphasis on IF), you would not see an increased level in the blood but would rather see a build-up in other tissues in the body.  But since there is no good way to measure this value (short of an autopsy), it is hard to address this question directly.  One possible way would be to look at the total intake amount of mercury and the total amount eliminated from the body.  What was left at that point would be the amount left in the body.  But, this too would be hard to do.

Regardless, I am sure that the debate will rage on.

No comments:

Post a Comment