Autism and the Chemicals That Cause It

It is not an exaggeration to describe the increasing incidence of autism as an epidemic. The number of diagnosed cases has grown by about a factor of seven over the last decade, and now the probability that a newborn infant will be so diagnosed is about 1%. Is it possible to increase another factor of seven? Is there a point at which people would consider not having children? Something is causing this increase, and some way of controlling it must be found.

There appears to be a genetic component to autism susceptibility. There is also mounting evidence that there are environmental conditions involved, with exposure to certain chemicals early in pregnancy identified as increasing risk. In fact, genetics and environment must be coupled in some way. Genetics alone cannot explain the dramatic rise in occurrence without postulating some sort of social selection process creating mating patterns that enhance susceptibility. Some have suggested such a process might exist, but it is highly unlikely that events on such a scale could be explained.

Recent data places more emphasis on environmental factors during pregnancy, particularly in the first trimester. A recent study of twins indicated that fraternal twin showed a considerably higher dual incidence of autism than one would expect from siblings born at different times. This suggests something occurred in womb during this pregnancy. Another study has indicated that the risk of autism increases by about a factor of four when the mother has used a common class of antidepressant medication during the first trimester. There is evidence that other chemicals play a role also.

Dr. Philip Landrigan reports on a study planning to track the health histories of 100,000 newborns for the next twenty years. The hope is that by tracking health outcomes and correlating them with prenatal exposure histories some concrete conclusions can be drawn regarding causation of autism and other conditions afflicting our children.

Landrigan is a believer in the importance of environmental factors and chemical exposures.

"But the most powerful proof-of-concept evidence derives from studies specifically linking autism to exposures in early pregnancy – thalidomide, misoprostol, and valproic acid; maternal rubella infection; and the organophosphate insecticide, chlorpyrifos. There is no credible evidence that vaccines cause autism."

"Expanded research is needed into environmental causation of autism. Children today are surrounded by thousands of synthetic chemicals. Two hundred of them are neurotoxic in adult humans, and 1000 more in laboratory models. Yet fewer than 20% of high-volume chemicals have been tested for neurodevelopmental toxicity."

Landrigan mentions a direct correlation between autism and exposure to four chemicals early in pregnancy. Let’s see what is known about these chemicals and the likelihood of exposure.

We find here some information on chlorpyrifos.

"First registered in 1965 and marketed by Dow Chemical Company under the tradenames Dursban and Lorsban, chlorpyrifos was a well known home and garden insecticide, and at one time it was one of the most widely used household pesticides in the US. Facing impending regulatory action by the EPA, Dow agreed to withdraw registration of chlorpyrifos for use in homes and other places where children could be exposed, and severely restricted its use on crops. These changes took effect on Dec. 31, 2001. It is still widely used in agriculture, and Dow continues to market Dursban for home use in developing countries. In Iran, Dow claims Dursban is safe for people, and its sales literature claimed Dursban has ‘an established record of safety regarding humans and pets’."

There seems to be plenty of opportunity for exposure if it was widely used in homes until 2001. It is still commonly used on food crops such as corn, almonds, apples and oranges. And of course any chemical that is used enters the environment and will show up in water supplies. We will save a discussion of the ethics of Dow’s marketing ploys for another day.

Valproic acid is also a fairly common drug.

"Valproic acid (VPA) is a chemical compound that has found clinical use as an anticonvulsant and mood-stabilizing drug, primarily in the treatment of epilepsy, bipolar disorder, and, less commonly, major depression. It is also used to treat migraine headaches and schizophrenia. VPA is a liquid at room temperature, but it can be reacted with a base such as sodium hydroxide to form the salt sodium valproate which is a solid. The acid, salt or a mixture of the two (valproate semisodium) are marketed under the various brand names Depakote, Depakote ER, Depakene, Depacon, Depakine, Valparin and Stavzor."

It has long been known that this drug is extremely dangerous to take during pregnancy. One would think that this would eliminate it as a risk factor. Unfortunately it is widely used in treating mental health issues. As is the case with antidepressants, it is often used in combinations with other psychoactive drugs as psychiatrists experiment with combinations in order to damp out the various side effects produced by individual drugs. So while epilepsy is relatively rare, the need for anticonvulsants is much larger. The level of use of antidepressants and other psychoactive drugs is astonishing. Robert Whitaker, in his book, Anatomy of an Epidemic, makes this claim:

"....one in every eight Americans takes a psychiatric drug on a regular basis."

So upwards of one in eight people are taking drugs that could be harmful to a fetus. With that incidence, what is the probability that a woman becomes pregnant inadvertently while on these drugs? How many young women are told that there is a danger during pregnancy from the drugs she has been prescribed, but that it has to be balanced by the danger from her mental condition? One suspects that most would choose to battle the devil they know.

Information on misoprostol can be found here.

"Misoprostol is a drug that is used for the prevention of non steroidal anti inflammatory drug (NSAID) induced gastric ulcers, for early abortion, to treat missed miscarriage, and to induce labor. The latter use is controversial in the United States. Misoprostol was invented and marketed by G.D. Searle & Company (now Pfizer) under the trade name Cytotec....but other brand-name and generic formulations are now available as well."

It is interesting to note that this drug has specific uses during pregnancy. It has been known to be dangerous to take during pregnancy, raising the threat of birth defects. Presumably, it is not widely used—or hopefully, it is not widely used.

"The drug is available through physicians only, not pharmacies, in the United States."

It is interesting that thalidomide is making a comeback. It has been found useful in treating painful conditions associated with leprosy, and it appears that it may have a role in combating cancerous tumors. Protocols are in place in an attempt to make sure it is not used during pregnancy. However, the World Health Organization (WHO) came to this conclusion:

"The WHO does not recommend the use of thalidomide in leprosy as experience has shown that it is virtually impossible to develop and implement a fool-proof surveillance mechanism to combat misuse of the drug."

The WHO has it correct this time. The leprosy connection occurred when a physician broke the rules and experimented with the drug even though its use was banned. So much for protocols! Who is to say it would not happen again. In addition, the mere fact that thalidomide is being manufactured and used means it will enter the environment with unknown consequences. Let the pharmaceutical companies find a better way.

Landrigan mentioned four chemicals for which exposure during pregnancy increased the risk of autism. The data on antidepressants came out after he had made his comments. That makes at least five, and there are thousands more to test. If one wants to subscribe to the environmental hypothesis, there is quite a bit of supporting data.

The damage during pregnancy from direct exposure can be addressed by more aggressive approaches to limiting access by pregnant, or potentially pregnant, women. But what does one do if the levels of chemicals encountered in the water we drink and the food we eat can also be a risk factor. We already know that antidepressants and other chemicals are at sufficient concentrations to harm fish. What level of exposure is required to damage a fetus? How would one even know?

One hopes Landrigan’s study is successful, but twenty years is a long time. We may not have that much time to spare.