Thimerosal

Page Contents (hide)

1. Introduction
2. Thimerosal Exposure
1. 2.1 Comparison Chart
2. 2.2 The Issues
3. 2.3 The Talking Points
3. Blog Resources (A - Z)
1. 3.1 Bartholomew Cubbins
2. 3.2 Autism Diva
3. 3.3 Kevin Leitch
4. 3.4 Not Mercury
5. 3.5 Orac
6. 3.6 Prometheus
7. 3.7 Skeptico
8. 3.8 Kathleen Siedel
4. Also See
1. 4.1 Papers
2. 4.2 Other Theories

1. Introduction

_{Thimerosal structure}

Thimerosal (UK spelling 'thiomersal') (C₉H₉HgNaO₂S) is a mercury-containing organic compound used as an antiseptic and antifungal agent. It was developed in 1929 by the pharmaceutical company Eli Lilly, and has been used as a preservative in vaccines, immune globulin preparations, antivenoms, and tattoo inks. In the body, it is metabolized to ethylmercury (C₂H₅Hg+) and thiosalicylate.

Full Material Safety Data Sheet

Thimerosal became associated with autism for two main reasons. Firstly it was reasoned that as thimerosal was introduced into vaccines in 1929 and Leo Kanner first labelled autism in the 1940's that one must have resulted from the other. Secondly, the vaccines that contained thimerosal were administered at roughly the same stage of life that autism become openly apparent in a person. Both these reasons are fallacies of correllation in that it is not established or even supported that one does indeed lead to the other.

In the US the American Academy of Pediatrics requested that thimerosal be removed from mainstream vaccines as a general precaution. In 2002, it was stated by the CDC that this task was complete. Thimerosal now exists only in vastly reduced doses in flu vaccines. In the UK thiomersal was removed from all vaccines in 2004.

2. Thimerosal Exposure

2.1 Comparison Chart

Shows total mercury body burden in a child via thimerosal based vaccines.

	_{Pre Mainstream Thimerosal Removal}	_{Post Mainstream Thimerosal Removal}
US	187.5 �g Hg	25 �g Hg
UK	75 �g Hg	0

Thimerosal Exposure in Infants and Developmental Disorders: A Retrospective Cohort Study in the United Kingdom Does Not Support a Causal Association. Pediatrics vol.114 No.3 September 2004, pp.584-591.

2.2 The Issues

After the correllation between thimerosal and autism was first suspected, campaign groups such as Safe Minds pushed scientific resources at finding a link. The result was the 2001 paper Autism: A Novel Form of Mercury Poisoning (Sallie Bernard, Albert Enyati, Lynn Redwood, RN, Teresa Binstock,). This paper is discussed in depth elsewhere but a brief summation of the connection with thimerosal is important.

The conclusions of the paper were as follows:

Exposure to mercury can cause immune, sensory, neurological, motor, and behavioral dysfunctions similar to traits defining or associated with autism
The similarities extend to neuroanatomy, neurotransmitters, and biochemistry
Children may have received a quantity of mercury that exceeds safety guidelines originating from thimerosal in vaccines
It is suggested that many cases of idiopathic autism are induced by early mercury exposure from thimerosal
It is suggested that this type of autism represents a hitherto unrecognized mercurial syndrome
It is suggested that genetic and non-genetic factors establish a predisposition whereby thimerosal�s adverse effects occur only in some children

2.3 The Talking Points

The Bernard paper is fraught with errors and supposition. Without the establishment of the first two points, the last four are meaningless. Therefore it only needs a refutation of these first two points to remove the link.

The gist of the paper is that the symptoms of mercury poisoning are similar to traits that define or accompny autism. Because of this, the authors reason that a link is established.

However, a careful study of the similarities listed by Bernard et al reveal that contrary to their assertions, the symptoms used to diagnose mercury poisoning and autism are entirely dissimilar. In 2003, Nelson and Bauman published a comprehensive refutation in Pediatrics

"In mercury poisoning, the characteristic motor findings are ataxia and dysarthria. These signs, along with tremor, muscle pains, and weakness, are noted on relatively high-dose exposure, acute or chronic. In 3 Romanian children accidentally exposed to ethyl mercury in a fungicide, these same symptoms were prominent. The outcome of fetal methyl mercury poisoning in severe form also included spasticity. In contrast, in autism, the only common motor manifestations are repetitive behaviors (stereotypies) such as flapping, circling, or rocking. Persons with Asperger syndrome may be clumsy, and hypotonia has been noted in some infants with autism; the frequency of clumsiness and hypotonia in autism spectrum disorders is not established. No other motor findings are common in autism, and indeed the presence of ataxia or dysarthria in a child whose behavior has autistic features should lead to careful medical evaluation for an alternative or additional diagnosis.

Other signs that may appear in children with chronic mercury toxicity, such as hypertension skin eruption and thrombocytopenia are seldom seen in autism.

When severe mercury poisoning occurs in prenatal life or early infancy, head size tends to be small and microcephaly is common. Prenatal exposure to other neurotoxins�lead, alcohol, and polychlorinated biphenyls, for example�also predispose to decreased head size. In contrast, in autism increasing evidence indicates that head size and, as measured by volumetric magnetic resonance imaging, brain size tends to be larger than population norms.

At sufficient dose mercury is indeed a neurotoxin, but the typical clinical signs of mercurism are not similar to the typical clinical signs of autism.

Mercury poisoning and autism both affect the central nervous system but the specific sites of involvement in brain and the brain cell types affected are different in the two disorders as evidenced clinically and by neuropathology.

Nonspecific symptoms such as anxiety, depression, and irrational fears may occur both in mercury poisoning and in children with autism, but overall the clinical picture of mercurism�from any known form, dose, duration, or age of exposure�does not mimic that of autism."

Thimerosal

1. Introduction

2. Thimerosal Exposure

2.1 Comparison Chart

2.2 The Issues

2.3 The Talking Points

3. Blog Resources (A - Z)

3.1 Bartholomew Cubbins

3.2 Autism Diva

3.3 Kevin Leitch

3.4 Not Mercury

3.5 Orac

3.6 Prometheus

3.7 Skeptico

3.8 Kathleen Siedel

4. Also See

4.1 Papers

4.2 Other Theories