Once again, the purported link between mercury/thimerosal and autism is in the news. This months "Archives in General Psychiatry" contains an article which looks at the continuing increase in the reported prevalence of autism in California while the amount of mercury is declining, and there is also an accompanying commentary in the same issue.
This article and commentary were discussed by Kristina Chew. Mark Blaxill, a leading proponent of the "autism=mercury poisoning" line of thought, backpeddles somewhat without totally conceding that the theory is dead. Brett of 29 Marbles asks what it would take for either side to change their mind.
Although I ultimately look to science to inform my opinions on things such as causality, I am not above referring to common sense, which is not a bad place to start when considering what kind of studies should be done.
One of the things that has made me doubt the whole autism=mercury poisoning thing from the start are dentists, and the amalgams they place. Specifically, where are all the autistic kids who had dentists and dental assistants as parents? More specifically, where is the large group of autistics that are 35-55 years old that had dentists or dental assistants as parents?
Why do I choose that age range? For a couple of reasons. Since autism wasn't described until the 1940's or so, I wouldn't expect older autistics. Also, this period would correspond to a time when dental caries were rampant (pre-fluoridation of water), as well as a time when handling of mercury and amalgam in dental offices was very casual. Mercury and metal filings (silver and zinc) used to be hand measured into a device, which then shook them together (right at the chairside) until they became a soft "amalgam" which was then packed into the cavity in the tooth. The dentist is typically "right in your face" as (s)he packs the amalgam into the tooth.
While some people today still blame mercury fillings for the exceedingly small amount of mercury vapor that is released by chewing on amalgam fillings, no one disputes that the greatest period of exposure to mercury is when the amalgam is first being mixed together. Since the 1970's or so, dental amalgams have come in a pre-proportioned sealed container, which minimizes the amount of mercury in the air in a dental office. Also, the number of amalgams that are placed today, while still large, pales compared to the past. Fluoridation started in the U.S. in 1955, and by the 1960's started to catch on. This resulted in a lot less exposure to mercury per child.
But between the time that autism was first described and the decline in amalgam fillings being placed in children there should have been an epidemic of children identified with autism, which declined as fillings per child dropped off. There should have been an even bigger incidence in the children of dental workers (dentists and dental assistants) who were occupationally exposed on a large scale to mercury vapor.
Where are they?
There are no studies that have shown this, and I am not even aware of any anecdotes of this phenomenon happening.
Me- Joe, husband of a great wife, and dad to two great kids, who were both adopted at birth.
Liz- My ever understanding wife, who manages to wear many hats (mom, advocate, therapist, teacher) for our kids.
Buddy Boy- Born in 2000. Funny, intelligent, inventive, and autistic. Loves machines.
Sweet Pea- Born in 2002. Typical little sister. Competitive, outgoing, and smart. Loves anything pink.