New research suggests that exposure to toxic air pollutants adversely affects children's grades, Newsmax reported.

Researchers at the University of Texas at El Paso found that fourth and fifth graders who were exposed to high levels of motor vehicle emissions from cars, trucks and buses on roads and highways were found to have significantly lower GPAs, even when accounting for other factors known to influence school performance.

"There are two pathways that can help us to explain this association," Sara E. Grineski, co-author of the study, said in a statement. "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."

For the study, researchers collected and analyzed data from nearly 2,000 fourth and fifth graders enrolled at 58 El Paso Independent School District (EPISD) elementary schools, Grist reported. Researchers selected schools in EPISD because it is the largest district in Texas' Region 19.

Parents and guardians answered questions about their children's grades in reading, language arts, math, social studies and science. The survey also asked about the family's income, household size, parent's education level, and if the child qualified for free or reduced-price meals.

"This isn't a phenomenon unique to EPISD," Grineski said. "What makes our study different is that we are actually studying kids in their home setting, but there's a body of literature where they have studied levels of air pollution at schools in California and Baton Rouge, Louisiana, instead of at children's homes. A study on the Los Angeles Unified School District showed that schools with higher levels of pollution have lower standardized test scores."

Timothy Collins, a sociology and anthropology associate professor, said air quality is an important issue in El Paso. The American Lung Association ranked El Paso eighth out of 277 metropolitan areas in the United States for annual particulate pollution in 2014.

Collins has reported that on-road mobile sources like the trucking industry are the largest contributors of overall air pollution in the city.

In 2014, nearly 400,000 trucks crossed from Ciudad Juarez to El Paso through the Ysleta-Zaragoza Port of Entry, and another 360,000 trucks crossed in the U.S. through El Paso's Bridge of the Americas Port of Entry.

"I am not sure that I would expect to find similar results in a place with considerably lower levels of air pollution," Collins said, referring to the survey's outcomes. "El Paso is a great laboratory to examine questions of Hispanic health."

The findings are detailed in the journal Population and Environment.