Like rings on trees, layers in teeth can serve as records of what exposures occurred during fetal development, and when.

Dr. Manish Arora, professor of environmental medicine and public health at Icahn School of Medicine, has developed a strategy using baby teeth to analyze exposures to possible toxins during fetal development to assess whether children who develop autism are biologically different early in life. Scientists used this technique to compare early zinc and copper metabolism in children with autism with their siblings without autism.