Researchers were awarded more than $4 million by the Obama administration’s Environmental Protection Agency to study whether exposure to air pollution led children to eat more fast food.

The $4,146,875 grant was awarded in 2013 to fund a five-year study at the University of Southern California into whether proximity to "near-roadway air pollution" was a contributing factor in childhood obesity.

In their published study, released this year in the American Journal of Clinical Nutrition, the researchers say they were unable to prove any association between pollutant exposure and obesity in children, but were able to find a correlation between pollutant exposure and changes in fast-food consumption patterns.

The study was based on interviews conducted with school-age children in twelve southern California communities in the 1990s. Diet information was based on self-reported information from the students, who were given a "food frequency questionnaire" annually until they graduated high school. Pollution levels were estimated for each student’s residential address.

The recorded information was inadequate for answering the question it was paid to answer on childhood obesity, the study explains.

"However, because there was no significant association between childhood air pollutant exposure and obesity or overweight in this study sample," the study explains, "the mediation effect of food pattern factor scores in the association between air pollutant exposure and obesity could not be examined under a consistent mediation model."

The study did say a correlation between pollution exposure and fast-food consumption was found, but it failed to prove any causal relationship between the two.

"Future studies are warranted to identify specific air pollutant chemicals that could have a causal effect on altering children’s dietary behavior," the study said.

The study says the correlation between pollution and fast-food consumption remained after adjusting for factors such as socioeconomic status and proximity to fast-food restaurants, but makes no claim that these factors were less at play than exposure to pollutants.

In addition to obesity, it was unable to associate high-calorie intake or a high "sweet food" diet with exposure to air pollutants.

The study was able to identify a correlation between pollutant exposure and trans fat intake, but as it acknowledges, the finding will have no policy implications due to the Trump administration’s decision to ban trans fats last summer.