Are Environmental Toxins to Blame for Rising Rates of Autism and Schizophrenia?

New research traces the genetic pathways that toxins use to attack the developing brain.

Half a century ago, a scientist was trying to create a clean lab that he could use to study radioactive materials free of contamination. But no matter what he tried, his tests kept reporting that they were contaminated with lead. Finally, he realized the source: the lead was coming from the air itself—put there by decades of cars burning leaded gasoline. Eventually, the U.S. Congress passed the Clean Air Act, removing lead from gasoline.

Then, 15 to 20 years later, the unexpected happened: a major drop in America’s rates of violent crime. When researchers examined this more closely, they found that neighborhoods with the highest rates of residual lead exposure also had the highest crime rates. They concluded that lead was affecting the children's developing brains, damaging their foresight, self-control, and other important factors for resisting crime.

Fast-forward to today. Crime rates remain relatively low, but we're seeing skyrocketing rates of brain-development disorders such as autism and ADHD. Could other environmental toxins to blame?

A Closer Look at the Brain

A research team at York University in Toronto, Canada, decided to track down the genetic pathway involved in the development of autism. They examined a fatty molecule called prostaglandin E2 (PGE2), which the body uses to regulate the immune system. (The results of the study were published in Cell Communication & Signaling.)

“In the brain, PGE2 also plays a major role in the maturation of brain cells and the connections formed between them during prenatal development,” senior author Dorota A. Crawford, associate professor at York University, said in an interview with Healthline.

Crawford’s team found that PGE2 interacts with a certain protein, which in turn regulates the expression of a number of genes. Although genes are fixed from the moment of conception, they can be turned on and off by different proteins, allowing the same genes to express differently in different people.

“[These] proteins are critical in the development, organization, and wiring of the nervous system,” Crawford said. “They guide the cells where and how far they need to go as well as control how they divide and communicate. [The] proteins tightly regulate the expression level of genes responsible for early brain development. Therefore, any change in the expression level of such genes will affect the course of development.”

When levels of PGE2 changed, so did the gene expression of a whole slew of genes that the proteins regulate.

"Interestingly, all these genes have been previously implicated in various autism studies,” lead author Christine Wong said in a press release.

Autism rates are climbing at a rate faster than increased diagnosis can possibly account for, with a CDC study estimating that 1 in 68 children now has an autism spectrum disorder. New toxins in our environment that are affecting this genetic pathway might help explain why.

A number of factors can affect levels of PGE2 in the body. These include exposure to estrogen-like compounds (such as those found in pesticides and certain plastics), a diet lacking in omega-3 and omega-6 fatty acids, air pollution and heavy metal exposure, infections, and certain medications and chemicals in cosmetics.

Many Stressors, One Result

These factors all put cells under stress, causing them to behave differently. Another study from Yale University, to be published in the journal Neuron, examined the effects of stressors on the genes of developing brain cells.

Their team exposed mouse embryos to different stressors: alcohol, methyl-mercury, and seizures (in the mother mouse). They found that all three stressors were activating a gene called heat shock factor (HSF1), which protects growing brain cells from stressors in the womb. When they engineered mice to lack the HSF1 gene, stressor-exposed mice showed abnormalities in their brain development. Even very low levels of toxins were enough to cause the damage.

The team also created stem cells from cells taken from people diagnosed with schizophrenia. These cells were much more sensitive to stress than stem cells made from people without schizophrenia, with their gene expression impacted far more heavily. Something about their genetic makeup was making them sensitive to stress, including environmental toxins.

"It appears that different types of environmental stressors can trigger the same condition if they occur at the same period of prenatal development," senior author Pasko Rakic said in a press release. "Conversely, the same environmental stressor may cause different pathologies, if it occurs at different times during pregnancy."

Schizophrenia, autism, and other disorders all share one thing in common: they appear to be the result of the brain wiring up incorrectly while the child is developing in the womb.

How Can I Protect My Child?

If you or your partner is expecting a child, or planning to have a child, Crawford has advice on how to minimize the risks to your child’s developing brain.

“Being an informed consumer is of utmost importance,” she said.

Doctors already recommend that expectant mothers avoid certain foods. This includes raw meats and eggs, which could carry infections that can impact the baby’s brain. It also includes large predatory fish, such as tuna and swordfish, which carry high levels of heavy metals like mercury.

“However, it is not just the food we eat that can affect the developing baby, but also the products that we use on a daily basis, such as skin creams and cosmetics,” she explained. “Our best advice is to avoid those creams and cosmetics that you don’t need—especially during the first trimester of pregnancy, when filtering barriers between the mother and baby are not fully developed.”

Crawford added, “As a mother of two toddlers and a scientist, I would advise pregnant women to avoid exposure to any medications or cosmetics during pregnancy and breastfeeding. Also, if you buy any products, look at the list of ingredients—the shorter the list, the better.”