What’s New in Environmental Research?

July 13, 2012

Today’s “Got Questions?” answer comes from Raymond Palmer, Ph.D., associate professor of family and community medicine at the University of Texas Health Science Center, San Antonio. 

Many of us want to see Autism Speaks focus on cutting-edge environmental research. Can you give us a recent example?

Our project investigates environmental exposures that may influence the development of autism spectrum disorders (ASD). While the causes of autism remain unknown, most scientists agree that genetic susceptibility and environmental triggers both play roles. Many different toxic agents in the environment could act as triggers. However, we know that bodies vary in their ability to detoxify these chemicals. This is one reason why only some of those exposed to a toxic substance suffer lasting harm.

As scientists, we face an even bigger challenge in understanding which environmental exposures affect autism risk. To do so, we need to measure exposure to these substances during critical periods of brain development – primarily during pregnancy and shortly after birth. This is difficult because a year or more will have passed between the exposure and autism’s first symptoms.

In the past, researchers have sought answers by asking mothers about their exposures during pregnancy. Unfortunately, poor recall can bias answers. Many times, parents simply don’t know about their exposures to pollutants and other toxic chemicals. So many of the chemicals remain hidden to us.

Another option has been to look for trace amounts of these chemicals in blood, hair or nails. Unfortunately, these body tissues are short lived. This means they’re useful for detecting only recent chemical exposures. They’re not particularly helpful for making conclusions about exposures during a past pregnancy.

We are currently studying another method – analyzing baby teeth, also known as “deciduous” teeth. It’s like looking through an archeological record. The enamel of certain baby teeth begins to form during prenatal development. Throughout early development, the enamel absorbs chemicals circulating through the baby’s body. The chemicals remain in the enamel layers. This gives us an objective look at which environmental toxins were present during brain development. 

Our laboratory has pioneered methods for extracting several types of semi-volatile chemicals from baby teeth without destroying the compounds in the process. Semi-volatile organic chemicals include many pesticides, plasticizers, air pollutants and certain types of medicines and additives. Emerging evidence suggests that they may contribute to the development of autism in susceptible individuals.

However, because of their “semi-volatile” nature, these chemicals tended to be destroyed in the process of identifying and measuring them. That recently changed. Advances in technology and lab techniques now allow us to accurately measure these substances without destroying them. 

Already, we’ve detected a variety of these chemicals in baby teeth. Eventually we’ll determine whether baby teeth from children with autism have greater concentrations than do those from typically developing children. We are currently enrolling families to participate in our study through the Interactive Autism Network.

Autism Speaks is funding the research we need to perform to validate our techniques and findings. These analyses could then become useful to many future studies. One of these would look at genetic vulnerabilities to specific compounds we’ve detected in baby teeth.

I’d like to mention several people playing pivotal roles in this effort. David Camann heads our chemical lab. Other members of our team include dentist-epidemiologist Steven Schultz and allergist-environmental scientist Claudia Miller.

Got more questions? Please send them to GotQuestions@autismspeaks.org.

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