(CNN) Air pollution may be associated with increased mental health disorders like anxiety and depression in children, a study has found.

The study, published Wednesday in the Environmental Health Perspectives journal, found that short-term exposure to high ambient air pollution corresponded with a rise in visits to the children's psychiatric emergency department.

Carried out over five years, the study said there was previous evidence linking harmful particulate matter with increased psychiatric disorders in adults, but that this effect on children's mental health has not yet been examined.

The study focused on fine particulate matter known as PM2.5. The microscopic particles, which are smaller than 2.5 micrometers in diameter, can lodge deep into the lungs and pass into other organs and the bloodstream. They cause irritation, inflammation and can lead to respiratory problems, while longer term exposure can even cause cancer and heart attack.

Researchers at the University of Cincinnati and the Cincinnati Children's Hospital Medical Center examined psychiatric patient visits, and then traced the concentration of PM2.5 in their residential areas. Researchers found that whenever there were increases in PM2.5, there would be more psychiatric visits within the following few days.

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