Website update on AS Policy Statement on Mercury and Autism

[Guest guest]

http://www.autismspeaks.org/science/policy/index.php

I think this is new but I am not sure and really am confused by how

it is worded. Anyone care to interpret?

Policy Statement on Mercury and Autism

Background

Mercury is a ubiquitous environmental toxin. Exposure to all three of

its forms, organic, inorganic, or elemental, can have adverse effects

on the developing nervous system. Medical science has known of

potentially grave effects of high dose mercury exposure since the

late 19th century. Only recently, however, have questions arisen

regarding possible associations between mercury exposure and autism.

The debate over mercury and autism escalated quickly because of

thimerosal, a synthetic form of organic mercury used as a

preservative and antimicrobial agent in vaccines. Thimerosal has been

an ingredient in vaccines and biologicals since the 1930s but, with

increases in recommended childhood immunization doses, by the 1990s

it became possible for a six month old infant to have been exposed to

a cumulative dose of organic mercury that exceeded certain limits set

by government health agencies. This, paired with the immense growth

in numbers of children diagnosed with autism in the 1990s prompted

many in and out of the autism community to wonder if there could be a

connection.

Practice

The body of evidence gathered through epidemiologic research to date

does not currently support a causal relationship between thimerosal

in childhood vaccines and autism risk. However, it is very difficult

for even the best epidemiologic study to rule out the existence of

small susceptible subgroups of children with autism in whom

thimerosal exposure may have played a causal role. Unfortunately,

there are currently no means of identifying individuals with

increased mercury susceptibility nor are there proven methods

allowing researchers to separate individuals with autism into groups

more or less likely to have different sets of causes.

The thimerosal question has highlighted a number of points whose

further consideration should significantly advance autism research.

First, although genes are believed to play a major role in autism,

more attention needs to be paid to mechanisms where genes exert their

influence by altering susceptibility to environmental exposures and

mechanisms by which environmental exposures may alter gene

expression. Second, there is a great need, when studying

environmental exposures, to find ways of identifying highly

susceptible individuals. And, third, because autism is a complex

condition possibly having multiple causes, researchers need to find

reliable ways to distinguish autism subgroups with distinct

etiologies.

Policy

Autism Speaks plans to strongly support a multidisciplinary research

agenda on environmental exposures and autism. We believe that

projects acknowledging the role of gene-environment interaction and

incorporating markers of exposure susceptibility and etiologic

heterogeneity will be the most productive in the long-term. Given

present knowledge, there is a fairly broad array of neurotoxic

environmental exposures worthy of further study but, moving forward,

the type and timing of exposures under investigation should continue

to comport with emerging developments in autism neurobiology.

References:

Goldman LR. Technical Report: Mercury in the Environment. Pediatrics

108(1); 197-205:2001 Institute of Medicine. Immunization Safety

Review * Vaccines and Autism.

National Academies Press, Washington DC, 2004.

National Research Council. Toxicological Effects of Methylmercury.

Washington, DC: National Academies Press, 2000. Lawler CP, Croen LA,

Grether JK, Van de Water J. Identifying Environmental Contributions

to Autism: Provocative Clues and False Leads. Ment Retard Dev Disabil

Res Rev. 10(4):292-302; 2004

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