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New California study concludes that thimerosal seems not to be the major cause for autism



Autism is a neurological disorder that affects learning and social interaction ability in children. Because mercury is a very potent neuro toxin, it came into the focus of toxicologists as a possible cause for autism. Since the mercury compound thimerosal (also known as thiomersal) has been used as a preservative in vaccines, it has been speculated that vaccines containing the chemical somehow could play a role in autism.

The new study:

The study period in question lasted from 1995 to 2007. It concludes that removing thimerosal from recommended infants vaccines as a precautionary measure in March 2001 had no effect on reducing the number of children suffering from autism.

"If thimerosal exposure is a primary cause of autism, then the prevalence of autism would be predicted to decrease, as young children's exposure to thimerosal has sharply decreased to its lowest levels in decades," said lead author Robert Schechter, a medical officer with the California Department of Health Services.

Ideally if there was a link between autism and thimerosal, then autism rates should have declined after 2001. That has unfortunately not happened. There were 0.6 autism cases per 1,000 live births in 1995. This number jumped to 4.1 cases per 1,000 live births in 2007.

Last year, the Centers for Disease Control and Prevention estimated that at least 1 in 150 children continued to suffer from autism in the United States. Number wise 300,000 children aged 4 to 17 had the disorder in 2004.

“You cannot use this data to rule out thimerosal as a factor. What you can say is there may be -- and probably are -- other environmental triggers that play a role. It is probable that exposure to these other factors may be increasing,” said Sally Bernard, co-founder and executive director of SafeMinds, an organization that advocates “sensible action for ending mercury-induced neurological disorders.”


Unfotunately, again this study fails to be fully convincing because of some limitations:

Epidemiological studies done by people who are part of the immunization program have a major credibility problem.

The Study of California Department of Public Health for example claims that "some" flu shots still contain thimerosal. Actually, out of 132 million doses of flu vaccine for the 2007-08 flu season, 8 million doses are thimerosal free. That means 94% contain the full amount of thimerosal. Stating that "some" contain thimerosal is a very deceptive statement at best.

Critics will say that California has banned thimerosal containing flu shots for pregnant women and infants. This ban took effect in 2006. However, the ban was lifted last year because of shortage of thimerosal free shots. If a pregnant woman got a flu shot in 2001 and her child followed the flu shot recommendations, the baby/fetus would have received six flu shots with the full amount of thimerosal by the year 2005. This hardly represents the claim that no thimerosal containing vaccines were given after 2001.

Vaccines with "trace" amounts of thimerosal are supposed to contain less than 1 microgram of mercury per 0.5 ml dose. This is equal to a concentration of 2000 micrograms per liter and would be classified by EPA as hazardous waste.

For the toxicologists mercury is a neurotoxin which depending on the mercury form (species) being present has a wide range of toxicological effects, including neurodevelopment disorders such as autism. Organomercury compounds, such as Thimerosal, are very toxic mercury compounds. Before somebody declares thimerosal containing vaccines safe, he should have a good explanation for such statement, considering the following facts:

0.5 parts per billion (ppb) mercury = Kills human neuroblastoma cells (Parran et al., Toxicol Sci 2005; 86: 132-140).

2 ppb mercury = U.S. EPA limit for drinking water (http://www.epa.gov/safewater/contaminants/index.html#mcls).

200 ppb mercury = level in liquid the EPA classifies as hazardous waste (http://www.epa.gov/epaoswer/hazwaste/mercury/regs.htm#hazwaste)

25,000 ppb mercury = Concentration of mercury in multi-dose, Hepatitis B vaccine vials, administered at birth from 1991-2001 in the U.S. (for current concentrations see a list of Thimerosal in US vaccines at : http://www.vaccinesafety.edu/thi-table.htm )

50,000 ppb mercury = Concentration of mercury in multi-dose DTP and Haemophilus B vaccine vials, administered 8 times in the 1990's to children at 2, 4, 6, 12 and 18 months of age. Current "preservative" level mercury in multi-dose flu, meningococcal and tetanus (7 and older) vaccines.

The study has other methodological flaws. SafeMinds, perhaps the most prominent organization focusing on mercury-related vaccine risks, published its own analysis of the paper arguing that the imprecision of the data in the study prevented any variable (including thimerosal) from being ruled out as a cause of increasing autism rates.

Other scientists argue that the increasing number of diagnosed cases of autism arises from purposely broadened diagnostic criteria (see for example: Morton Ann Gernsbacher, Michelle Dawson, and H. Hill Goldsmith, Three Reasons Not to Believe in an Autism Epidemic, Current Directions in Psychological Science, 14/2 (2005) 55-58). DOI: 10.1111/j.0963-7214.2005.00334.x.

The new study

Robert Schechter, Judith K. Grether, Continuing Increases in Autism Reported to California's Developmental Services System: Mercury in Retrograde, Arch. Gen. Psychiatry, 65/1 (2008) 19-24. DOI: 10.1001/archgenpsychiatry.2007.1

Related Studies:

M.C. Desoto, R.T. Hitlan, Blood Levels of Mercury Are Related to Diagnosis of Autism: A Reanalysis of an Important Data Set, J. Child Neurol., 22/11 (2007) 1308-1311. DOI: 10.1177/0883073807307111

Philippe Grandjean, Philip J. Landrigan, Developmental neurotoxicity of industrial chemicals, The Lancet, Nov. 8, 2006; Vol. 368: online edition.  DOI: 10.1016/S0140-6736(06)69665-7

 Raymond F. Palmer, Steven Blanchard, Zachary Stein, David Mandell, Claudia Miller, Environmental mercury release, special education rates, and autism disorder: an ecological study of Texas, Health & Place,  12/2 (2006) 203-209. DOI: 10.1016/j.healthplace.2004.11.005

Gayle C. Windham, Lixia Zhang, Robert Gunier, Lisa A. Croen, Judith K. Grether, Autism Spectrum Disorders in Relation to Distribution of Hazardous Air Pollutants in the San Francisco Bay Area, Environ. Health Perspect., 114/9 (2006) 1438-1444. DOI: 10.1289/ehp.9120

Robert Nataf, Corinne Skorupka, Lorene Amet, Alain Lam, Porphyrinuria in childhood autistic disorder: Implications for environmental toxicity, Toxicol. Appl. Pharmacol., 214 (2006) 99-108. DOI: 10.1016/j.taap.2006.04.008

H.R. Andersen, J.B. Nielsen, P. Grandjean, Toxicologic evidence of developmental neurotoxicity of environmental chemicals, Toxicology, 144 (2000) 121-127. DOI: 10.1016/S0300-483X(99)00198-5

For more related studies please consult earlier EVISA News !

Related EVISA News (newest first)

November 12, 2017: Mercury and Autism: Is there a Link ? 

last time modified: May 25, 2024


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