Researchers showed that air pollution exposures did not alter the effects of physical activity on gray matter volume. However, researchers did find air pollution exposures altered the effects of vigorous physical activity when looking at white matter hyperintensities
researchers found that vigorous physical activity reduced white matter hyperintensities in areas of low air pollution, but these benefits were not found among those in high air pollution areas.
Overall, the effect of air pollution on brain health was modest -- roughly equivalent to half the effect of one year of aging, while the effects of vigorous activity on brain health were much larger -- approximately equivalent to being three years younger."