Comes a time when the blind man takes your hand
Says “don’t you see?”

— Robert Hunter, “Comes A Time”


We’ve seen examples previously on The PediaBlog about how children in the United States are being born “pre-polluted.” Prenatal exposure to pollution, chemicals, and other toxicants has already been associated with increasing rates of autism, obesity, cancer, birth defects, and ADHD in children. A new study, published in JAMA Psychiatry, highlights the mechanism of action whereby air pollution, specifically polycyclic aromatic hydrocarbons, affects the developing brain’s white matter, prenatally and postnatally:

Our findings suggest that prenatal exposure to PAH air pollutants contributes to slower processing speed, attention-deficit/hyperactivity disorder symptoms, and externalizing problems in urban youth by disrupting the development of left hemisphere white matter, whereas postnatal PAH exposure contributes to additional disturbances in the development of white matter in dorsal prefrontal regions.


That’s pretty specific damage, caused by increasingly ubiquitous air pollution, resulting in very significant cognitive problems in children. Kathleen Doheny says the researchers used MRI scans to document the anatomical brain changes caused by air pollution exposure and help explain the clinical effects:

They found that prenatal exposure to the pollutants was linked with thinking and behavioral problems. The greater the exposure, the worse the brain changes and the more likely the kids were to have ADHD symptoms or other issues.

In earlier research, the team had found that exposure to PAHs during gestation was linked with several problems, including developmental delays by age 3, reduced verbal IQ at age 5 and anxiety and depression by age 7.

In the new study, the researchers found reductions in the white matter surface of the brain’s left hemisphere. This type of reduction is linked to slower processing of information during IQ tests and more severe problems in behavior, including ADHD symptoms and aggression, the researchers said. Being exposed after birth was linked to additional white matter changes linked to problems in concentration and problem-solving ability.


Polycyclic aromatic hydrocarbons (PAH) are the toxic byproducts of burning carbon — fossil fuels (oil, coal, natural gas) and plant material, including tobacco. And while we’re on the subject of burning carbon and ADHD, Shereen Lehman has news for adults who expose children to secondhand tobacco smoke:

Children exposed to tobacco smoke at home are up to three times more likely to have attention deficit hyperactive disorder (ADHD) as unexposed kids, according to a new study from Spain.

The association was stronger for kids with one or more hours of secondhand smoke exposure every day, the authors found. And the results held when researchers accounted for parents’ mental health and other factors.

“We showed a significant and substantial dose–response association between (secondhand smoke) exposure in the home and a higher frequency of global mental problems,” the authors write in Tobacco Control.

According to the Centers for Disease Control and Prevention, two of every five children in the US are exposed to secondhand smoke regularly.


Parents: Think about this the next time your child gets stuck in traffic behind a diesel-burning, soot-spewing truck, or finds himself in the same room where tobacco is being smoked, or plays outside on an “ozone action day” this summer.

Doctors: Think about indoor and outdoor environmental pollution as a cause of cognitive and physical maladies our patients are born with, or later acquire. Factor in where people live and their proximity to heavy traffic, industrial sites, power plants, natural gas and oil wells, and communities that allow backyard plant and leaf burning. (Southwestern Pennsylvania has lots of these carbon-burning sites, yet most people I ask don’t have a clue how close the nearest unconventional natural gas well is from their homes. Do you?)

Accumulating data is shining a bright light on a big problem — if only we could see it.