Fourth and fifth graders who are exposed to toxic air pollutants are more likely to have lower school grades.

That’s the latest word from University of Texas at El Paso researchers who analyzed the academic performance of 1,895 children attending the El Paso Independent School District (EPISD).

They used the Environmental Protection Agency's National Air Toxics Assessment to gauge children's exposure to toxic air pollutants, such as diesel exhaust, around their homes. They then compared the children’s school grades.

The results, published in the academic journal Population and Environment, showed children who were exposed to high levels of motor vehicle emissions from cars, trucks, and buses were found to have significantly lower grade point averages.

The findings held true, even when other factors known to influence school performance were taken into account.

"There are two pathways that can help us to explain this association," said researcher Sara E. Grineski, an associate professor of sociology and anthropology at UTEP. "Some evidence suggests that this association might exist because of illnesses, such as respiratory infections or asthma. Air pollution makes children sick, which leads to absenteeism and poor performance in school.

“The other hypothesis is that chronic exposure to air toxics can negatively affect children's neurological and brain development."