Epidemiological Analysis Suggests Autism and Methylmercury Link

Science Daily reports on a new analysis of epidemiological evidence published in the International Journal of Environment and Health which suggests that exposure to the toxic chemicals, such as methylmercury can cause harm at levels previously considered safe:

Philippe Grandjean of the Department of Environmental Health at Harvard School of Public Health, in Boston, and the University of Southern Denmark in Odense, explains that the causes of suboptimal and abnormal mental development are mostly unknown. However, severe exposure to pollutants during the development of the growing fetus can cause problems that become apparent as brain functions develop - and ultimately decline - in later life. Critically, much smaller doses of chemicals, such as the neurotoxic compound methylmercury, can harm the developing brain to a much greater extent than the adult brain .......... until recently research into the effects of pollutants on the brain has been clouded by the lack of information on actual exposure. Moreover, finding a direct link between specific problems with the brain and exposure relies on statistical, or epidemiological, analysis rather than case-by-case understanding. The researchers say that neurodevelopmental disorders of possible environmental origin affect between 5% and 10% of babies born worldwide, leading to dyslexia, mental retardation, attention deficit/hyperactivity disorder, cerebral palsy, and autism.

The authors concern about the lack of case by case study and over reliance on epidemiological evidence echos comments by Dr.Bernardine Healy, former head of the NIH, in an interview earlier this year with CBS News and Sharyll Attkisson when she said government had been too quick to dismiss a vaccine/autism link:

"I think that the public health officials have been too quick to dismiss the hypothesis as irrational," Healy said.

"But public health officials have been saying they know, they've been implying to the public there's enough evidence and they know it's not causal," Attkisson said.

"I think you can't say that," Healy said. "You can't say that."

Healy goes on to say public health officials have intentionally avoided researching whether subsets of children are “susceptible” to vaccine side effects - afraid the answer will scare the public.

"You're saying that public health officials have turned their back on a viable area of research largely because they're afraid of what might be found?" Attkisson asked.

Healy said: "There is a completely expressed concern that they don't want to pursue a hypothesis because that hypothesis could be damaging to the public health community at large by scaring people. "First of all," Healy said, "I think the public’s smarter than that. The public values vaccines. But more importantly, I don’t think you should ever turn your back on any scientific hypothesis because you’re afraid of what it might show."

autism

Autistic Children - Canaries In The Coal Mine?

The classic example of animals serving as sentinels is the "canary in the coal mine". Well into the 20th century, coal miners in England and the US brought canaries into coal mines as an "early warning signal" for toxic gases including methane and carbon monoxide. The birds, being more sensitive, would become sick before the miners, who would then have a chance to escape or put on protective respirators.

- Wikipedia

Is the dramatic rise in the diagnoses of autism solely a result of changed diagnostic criteria and enhanced public awareness? Or are environmental factors also involved? Are children suffering increasingly from developmental disorders, including autism, because of degradation of the world environment? Like the canaries in the coal mines do the increasing numbers of autistic children also serve as a warning of serious environmental decay?

The thimerosal/vaccine theories have occupied much public attention over the past several years but have they also distracted from other potential environmental factors? Few would deny the very important role of genetics in autism. The Unified Theory of Autism and the concept of genetic mutation, however, suggest that genetic mutations associated with autism may arise from environmental triggers. Vaccines are not the only human source of mercury which can also be found in thermometers, dental fillings, fluorescent light bulbs, and other consumer products. Environment Canada has a web page called Mercury and the Environment which illustrates how mercury, particularly methylmercury, concentrates in in the environment, and in living organisms.

Some mercury compounds are more easily absorbed by living organisms than elemental mercury itself. When atmospheric mercury falls to earth, it may be altered by bacterial or chemical action into an organic form known as methylmercury. Methylmercury is much more toxic than the original metal molecules that drifted in the air, and has the ability to migrate through cell membranes and "bioaccumulate" in living tissue. Bioaccumulation is the process by which a substance builds up in a living organism from the surrounding air or water, or through the consumption of contaminated food. Bioaccumulation will vary for different species and will depend on emission sources as well as local factors like water chemistry and temperature.

In the following figure, the concept of accumulated methylmercury is illustrated by the red dots, however the dots are not to scale.

The bioaccumulation of methylmercury in natural ecosystems is an environmental concern because it inflicts increasing levels of harm on species higher up the food chain. This occurs through a process known as "biomagnification", whereby persistent substances like methylmercury will increase in concentration from microorganisms, to fish, to fish eating predators like otters and loons, and to humans. Elevated methylmercury levels may lead to the decline of affected wildlife populations and may affect human health when people consume significant quantities of fish or other contaminated foods.

The Environment Canada site states that the amount of mercury in the air arising from human activities has increased by a factor of 2 to 4 since industrialization. In addition to mercury there have been frequent recalls of toy products containing lead. A recent California study suggested a causal connection between some pesticides and autism rates.

With the significant environmental degradation taking place today it seems entirely possible that the increasing prevalence of autism amongst children may be due to more than changes in diagnostic criteria and public awareness. Increasing levels of toxic substances in our environment may be triggering genetic mutations and may be contributing significantly to the increasing diagnoses of autism. Autism research should pursue all possible factors, genetic and environmental. To help our autistic children - and to more thoroughly understand what we are doing to our environment and ourselves.