Air Pollution and Poverty Stack the Deck for ADHD

Combined effects of prenatal exposure to polycyclic aromatic hydrocarbons and material hardship on child ADHD behavior problems

Scientists at the Columbia Center for Children’s Environmental Health (CCCEH) at the Mailman School of Public Health report the first evidence that prenatal exposure to polycyclic aromatic hydrocarbons (PAH)—carcinogenic and neurotoxic combustion byproducts commonly found in urban air—combines with material hardship to significantly increase ADHD symptoms in children.

2017 Study Highlights

  • PAH are common carcinogenic and neurotoxic combustion-related air pollutants.
  • Exposure to PAH tends to be disproportionately high in low income communities.
  • Prenatal PAH exposure was measured by PAH-DNA adducts in maternal blood.
  • We evaluated the combined effects of prenatal PAH and material hardship on ADHD.
  • We observed significant effects of combined exposures on ADHD behavior problems.

2017 Study Abstract

Polycyclic aromatic hydrocarbons (PAH) are carcinogenic and neurotoxic combustion by-products commonly found in urban air. Exposure to PAH is disproportionately high in low income communities of color who also experience chronic economic stress.

In a prospective cohort study in New York City (NYC) we previously found a significant association between prenatal PAH exposure and Attention Deficit Hyperactivity Disorder (ADHD) behavior problems at age 9. Here, we have evaluated the joint effects of prenatal exposure to PAH and prenatal/childhood material hardship on ADHD behavior problems.

Materials and Methods
We enrolled nonsmoking African-American and Dominican pregnant women in New York City between 1998 and 2006 and followed their children through 9 years of age. As a biomarker of prenatal PAH exposure, PAH-DNA adducts were measured in maternal blood at delivery and were dichotomized at the limit of detection (to indicate high vs. low exposure). Maternal material hardship (lack of adequate food, housing, utilities, and clothing) was self-reported prenatally and at multiple time points through child age 9. Latent variable analysis identified four distinct patterns of hardship. ADHD behavior problems were assessed using the Conners Parent Rating Scale- Revised. Analyses adjusted for relevant covariates.

Among 351 children in our sample, across all hardship groups, children with high prenatal PAH exposure (high adducts) generally had more symptoms of ADHD (higher scores) compared to those with low PAH exposure. The greatest difference was seen among the children with hardship persisting from pregnancy through childhood. Although the interactions between high PAH exposure and hardship experienced at either period (“persistent” hardship or “any” hardship) were not significant, we observed significant differences in the number of ADHD symptoms between children with high prenatal PAH exposure and either persistent hardship or any hardship compared to the others. These differences were most significant for combined high PAH and persistent hardship: ADHD Index (p < 0.008), DSM-IV Inattentive (p = 0.006), DSM-IV Hyperactive Impulsive problems (p = 0.033), and DSM-IV Index Total (p = 0.009).

The present findings add to existing evidence that co-exposure to socioeconomic disadvantage and air pollution in early life significantly increases the risk of adverse neurodevelopmental outcomes. They suggest the need for multifaceted interventions to protect pregnant mothers and their children.

More Information
  • Combined effects of prenatal exposure to polycyclic aromatic hydrocarbons and material hardship on child ADHD behavior problems, sciencedirect, 4 October 2017.
  • Air Pollution and Poverty Stack the Deck for ADHD, ccceh, 4 October 2017.
  • Research in New York City, ccceh.
  • Toxic Combination of Air Pollution and Poverty Lowers Child IQ, sciencedirect, 4 October 2017.
  • Featured image credit parents.

Have your say! Share your views