Pregnant women are mindful of what they eat and drink for nine months, but less so of the air they breathe. Does it matter? According to a new collaborative research effort from the Columbia Center for Children’s Environmental Health and New York State Psychiatric Institute, yes, it does; air pollution may negatively affect women's unborn children.

For the study, published in the Journal of Child Psychology, researchers analyzed blood samples from 462 mother-child pairs living in New York City from the time of pregnancy through 11 years of age. Researchers suspected prenatal exposure to polycyclic aromatic hydrocarbons (PAH), a common air pollutant, increased an unborn child's risk for attention-deficit hyperactivity disorder, symptoms of anxiety, depression, and inattention. PAH pollutants are found in the environment, thanks to motor vehicles, tobacco smoke, and emissions from oil and coal burning for home heating and power.

Researchers tested children's behavior at ages three, four, five, seven, nine, and 11 years old, ultimately concluding that mothers' exposure to PAH during pregnancy could lead to abnormal behavioral patterns. The more PAH women were exposed to during pregnancy, the worse their children scored on behavior tests.

The study’s lead investigator Amy Margolis, a professor of medical psychology at Columbia University Medical Center, in a press release: "This study indicates that prenatal exposure to air pollution impacts development of self-regulation and may underlie the development of many childhood psychopathologies that derive from deficits in self-regulation, such as ADHD, OCD, substance use disorders, and eating disorders."

In fact, the study found misbehaved children also had difficulty managing disruptive thoughts, emotions, impulses, and had poor social skills. When they reached adolescence, they were more likely to engage in high-risk behavior.

Air pollution may be a risk factor for ADHD alone, a condition that affects nearly 10 percent of children in the United States between ages four and 15. According to a study conducted in 2013, children exposed to high levels of traffic pollution showed decreased memory performance and scored worse on cognitive tests. The idea is pollution can travel to the brain and cause it to swell, which means unborn babies and children are at greater risk for incurring damaging, long-term effects.

"There is a significant association directly between PAH exposure and poorer social competence," the study’s co-author Frederica Perera, a researchers from Columbia Center told Time. "The exposures [to PAHs] are preventable."

Prenatal exposure may damage the neural circuits that control emotion and attention in the brain, prompting children to act out and develop mental health problems as they grow. However, researchers need to conduct further studies on how PAH pollutants can negatively affect fetal development.

Source: Margolis AE, Rauh VA, and Herbstman JB, et al. Longitudinal effects of prenatal exposure to air pollutants on self-regulatory capacities and social competence. Journal of Child Psychology and Psychiatry. 2016.