New science, new insights about mercury and autism in children
Report Release Date: 13 December 2004
Scientists have identified a signature metabolic impairment or "biomarker" in autistic children that strongly suggests that these children would be susceptible to the harmful effects of mercury and other toxic chemical exposures (James 2004a).
This impairment manifests as a severe imbalance in the ratio of active to inactive glutathione, the body's most important tool for detoxifying and excreting metals. Glutathione works as an antioxidant, keeping in check the potentially destructive process of oxidative stress caused both by normal metabolism and environmental contaminants. Autistic children showed a significant impairment in every one of five measurements of the body's ability to maintain a healthy glutathione defense.
These findings raise serious concerns about children's overall exposure to environmental contaminants. Mercury is of particular concern, however, because of its proven toxicity to the developing brain and nervous system, and documented high exposures from a variety of sources.
One of every six pregnancies is exposed to methyl mercury above EPA's safe level from maternal consumption of contaminated seafood (CDC 2002, Mahaffey 2004). Thimerosal, a preservative in vaccines that is 49 percent ethyl mercury, was a major source of mercury exposure from 1988 through 2002 when it was removed from childhood immunizations at the urging of the Public Health Service and the American Academy of Pediatrics. Elemental mercury from dental amalgams is another potentially important source, but its contribution to overall mercury exposure is less well studied.
The incidence of autism increased 10-fold from 6 in 10,000 in the 1980s (Blaxill 2004), to about 60 in 10,000 today (Autism Alarm, PDF file). These new findings significantly strengthen the possibility that mercury could cause or contribute to autism and other neurodevelopmental disorders by identifying a metabolic imbalance common to nearly all autistic children that would make these children poorly equipped to mount a defense against a number of neurotoxic compounds, including mercury.
These findings could have major implications for public health protections from toxic chemicals in the environment. They identify a subgroup of people at increased risk of harm, and provide important new evidence that policies designed to protect the average person, or even the average child, from chemical exposure, are insufficient to fully protect the public health. Environmental and health officials must evaluate the adequacy of current laws and policies to protect individuals with a heightened sensitivity to chemical exposure.
Finally, these findings raise serious concerns about the studies that have allegedly proven the safety of mercury in vaccines. The epidemiologic studies used to dismiss a causal relationship between autism and thimerosal have assumed that all children have the same resistance to chemical exposure. To properly investigate the potential harm from mercury-containing shots researchers would have to compare autism rates in children with the same type of vulnerability.
In 1988, the Centers for Disease Control (CDC) recommended important new additions to the nation's infant immunization program, including three Hepatitis B immunizations (one injected at birth), and three Haemophilis B shots-all delivered by six months of age. Drug companies responded with vaccinations supplied in multiple dose containers preserved with the mercury-based antibacterial thimerosal. Neither the CDC, nor the Food and Drug Administration (FDA), which monitors the safety of vaccinations, expressed concerns at that time about the relatively high doses of mercury that newborn babies and infants would be exposed to through these shots.
A dramatic nationwide increase in autism followed directly on the heels of the abrupt rise in thimerosal exposure (Blaxill 2001). Rates rose from 6 in 10,000 children in the 1980s to 60 in 10,000 today (Blaxill 2004a, American Academy of Pediatrics 2004). In 2003, the Autism Society of America estimated the cost of treating and caring for 1.5 million autistic children at $90 billion per year (Autism Society of America 2003).
To better understand whether or not the dramatic increase in autism was related to the abrupt nationwide increase in exposure to mercury in vaccinations, the CDC conducted its own epidemiologic study, and then convened a panel of the Institute of Medicine (IOM) of the National Academy of Sciences to review the issue independently. On May 17, 2004, the IOM published its final report on the possible link between thimerosal and autism. The IOM rejected "a causal relationship" between the two, and then took the unusual step of recommending the termination of additional research into the subject, stating clearly that, "Further research to find the cause of autism should be directed toward other lines of inquiry" (IOM press release 2004a). Or as put by the chair of the IOM committee, "Available funding for autism research should be channeled to the most promising areas, of which the link with vaccines does not appear to be one" (Barclay 2004). The chief of the national immunization program at the Centers for Disease Control went even further, declaring that only "junk scientists and charlatans" support research into the potential link between thimerosal exposure and autism (Levin 2004).
The IOM's recommendation that research into the potential link between mercury and autism be abandoned is highly unusual coming from an institution built on the notion of free scientific inquiry. Not surprisingly, the statement was cause for concern in some scientific quarters. In spite of these and other concerns, however, the committee's findings remain, on balance, an accurate reflection of the published epidemiologic studies at the time of its release.
What is more important, but largely overlooked, was the committee's own admission that it did not adequately address the leading theory among independent scientists - that autism could be triggered by environmental exposures, including mercury in vaccines, in a subset of vulnerable children. As the IOM panel stated in its final report:
"...the committee cannot rule out, based on the epidemiological evidence, the possibility that vaccines contribute to autism in some small subset or very unusual circumstances" (IOM 2004b).
Or as put by the Chair of the IOM committee, Dr. Marie McCormick, of the Harvard School of Public Health:
"Some children could be particularly vulnerable or susceptible to mercury exposure because of genetic or other differences" (McCormick 2001).
An eighteen-month investigation by Environmental Working Group concludes that scientists have identified a signature metabolic profile or "biomarker" in autistic children that may indeed characterize a "small subset" of susceptible children. These findings represent a potential milestone in our understanding of individual vulnerability to toxic substances, including, but not limited to, mercury. This science turns on its head the IOM's judgment that research into the thimerosal/autism link be abandoned, and instead strengthens significantly the case for additional research in this area. We found that:
- Newly published research and follow-up testing by former FDA senior research scientist Dr. Jill James, now of the University of Arkansas for Medical Sciences, has uncovered a unique and consistent metabolic imbalance in autistic children when compared to normal healthy children (James 2004a, 2004b). This impairment manifests as a severe deficit in the body's most important antioxidant and metals detoxifier, glutathione. When compared to normal health children, autistic children showed a significant impairment in every one of five measurements of the body's ability to maintain a healthy glutathione defense. These findings are strong evidence that if these children were exposed to a potentially toxic dose of mercury or other compound they would be much less able to mount an effective defense.
Source: James 2004b
- The finding of a significant glutathione deficit in autistic children provides a biological basis for integrating many facets of autism that have baffled researchers attempting to pin the autism epidemic on a single gene or chemical exposure.
- The implications of these findings extend well beyond thimerosal and autism. Reduced antioxidant defense may characterize a group of individuals who are demonstrably more sensitive to the effects of a range of toxic chemical exposures, and shed light on increasing rates of related learning and behavioral disorders.
- These findings raise serious concerns about the studies that have allegedly proven the safety of mercury in vaccines. While Dr. James' results do not prove that mercury causes autism, they significantly strengthen this possibility. The epidemiologic studies used to dismiss a causal relationship between mercury and autism assumed that all children have the same resistance to chemical exposure. Given James' finding that autistic children would be much more sensitive to certain chemical contaminants, studies that do not acknowledge these vulnerabilities cannot be used to dismiss the relationship between environmental chemicals, including mercury, and the disease.
- When James' results are considered together with the existing body of science, including other recently published research, the weight of the evidence now strongly supports increased research into the relationship between thimerosal and autism as well as other neurodevelopmental and neurodegenerative disorders.
The findings by James significantly strengthen the science supporting a connection between mercury and autism. Contrary to the recommendation of the Institute of Medicine, that research on the relationship between mercury and autism essentially be abandoned, the weight of the evidence in the basic biological sciences now supports accelerated funding and research into the biological pathways and genetic mechanisms that may make some individuals more vulnerable to mercury and a host of other environmental toxins. We recommend increased federal support for research in this area.
A small follow-up group of children in this study have benefited markedly when their impaired antioxidant defense was restored. This provides important clues about treatments that could derive from increased funding for research in this area.
Source: James, 2004a
Several studies are underway to explore the relationship between thimerosal-containing vaccines and autism in greater detail—including a follow-up study underway by the CDC (Verstraeten 2004). The power of these studies would be dramatically enhanced if they included Dr. James' simple blood test to examine the antioxidant capacity of autistic and healthy children as a factor that modifies an individual's sensitivity to mercury toxicity.
Policy Reform: Environmental Health
James' findings also have major implications for public health protections and pollution control. They potentially identify a subgroup of people with dramatically increased risk of harm from industrial chemicals, and provide important new evidence that policies designed to protect the average person, or even the average child, from chemical exposure, are insufficient to fully protect the public health. Children with the metabolic profile James has identified may be more susceptible to a vast number of common pollutants, from arsenic in drinking water and pressure-treated wood, to air pollution from cars and power plants. Environmental and health officials must evaluate the adequacy of current laws and policies to protect individuals with a heightened sensitivity to chemicals exposure.
Policy Reform: Immunizations
The Environmental Working Group strongly supports the standard battery of childhood immunizations recommended by the American Academy of Pediatrics and the CDC. Clearly, vaccinations have led to many major advances in public health. At the same time, EWG recommends the removal of thimerosal and all mercury-based preservatives from all vaccines in the United States, as is currently required by law in California and Iowa.
As individual states and many industrialized countries have phased out or banned the use of the mercury-based preservative in vaccines, the use of immunizations preserved with thimerosal continues unabated in the developing world. Precisely because of the clear public health benefits of vaccinations, the limited access to refrigeration, and the need to deliver vaccines in multiple dose containers in these countries, we urge the World Health Organization and multinational drug companies to move quickly to develop and adopt an alternative, low cost, effective preservative that is safer than mercury-based thimerosal.