Air pollution has a huge role in attention-deficit/hyperactivity disorder (ADHD), latest research suggests.
A study reported in PLOS ONE found that maternal exposure to toxic air pollutants called polycyclic aromatic hydrocarbons (PAHs) during pregnancy increased the risk of ADHD in children.
PAHs are chemicals found naturally in the environment, that are also released into the atmosphere during the incomplete burning of fossil fuel such as diesel, gasoline and coal. The same chemicals, according to the experts at the United States Environmental Protection Agency (EPA), are also being widely used to make dyes, pesticides and plastics.
Exposure to PAHs can occur by breathing fumes from vehicle exhaust, cigarette smoke or through consuming food cultivated in a contaminated soil.
For the study, researchers from the Mailman School of Public Health - Columbia University in the US looked at 233 non-smoking mothers living in New York City and their children.
Frederica Perera and colleagues, analysed PAH-DNA adducts in maternal blood samples collected after delivery. PAHs, when inhaled during pregnancy forms adducts in blood and other tissues, making it easier to measure levels of the pollutant exposure.
Urine samples of the children were examined for PAH metabolites at three and five years. The children also underwent ADHD tests.
Results showed that children who were highly exposed to the air pollutant while in their mother's womb had five times higher risk of displaying behaviour problems at the age of nine, than their peers who were not exposed.
"This study suggests that exposure to PAH encountered in New York City air may play a role in childhood ADHD," lead author of the study Frederica Perera, from the Mailman School, said in a news release. "The findings are concerning because attention problems are known to impact school performance, social relationships, and occupational performance."
Earlier in 2012, the same researchers had reported on developmental delay, low IQ and symptoms of anxiety, depression and attention problems in children of mothers exposed to the same air pollutants.
Though the authors couldn't underline the exact factors that led to the occurrence, they said that the chemical can disrupt the endocrine system, cause DNA damage and oxidative stress or affect the proper distribution of nutrients and oxygen from the placenta to the baby.
Exposure to air pollution during pregnancy and childhood has also been linked to childhood cancer, low birth weight, autism, vitamin D deficiency, diabetes, lung damage and preeclampsia.