“…While our findings were not significant, this trend is consistent with the emerging pattern of association of air pollution with gene polymorphisms and disease risk [ 30 , 31 , 32 , 33 , 34 , 35 , 36 , 37 , 38 , 39 , 40 , 41 , 42 , 43 , 44 , 45 , 46 , 47 ]. Previous studies have found significantly increased polymorphisms of the MTHFR gene with increased air pollution levels in various conditions including colorectal cancer, breast cancer, leukemia, Alzheimer’s disease, and hypertensive disorders during pregnancy (HDP) [ 30 , 31 , 33 , 34 , 35 ], and increased disease risk for HDP [ 35 ]. Although the MTHFR gene is known to be heat sensitive [ 84 , 85 ], there is no current evidence of heat sensitivity related to the NOS3 mechanism; however, the trend of increased NOS3 polymorphisms with increased air pollution for countries with higher risk (RR > 2) is consistent with each of these previous studies [ 30 , 31 , 33 , 34 , 35 ].…”