LowEmissionAsphalt-136pg-WhitePaper-May2023

P a g e | 68 Traffic Pollution EPA technical data shows that as much as one-third of atmospheric carbon dioxide, 122 the leading greenhouse gas ; and two-thirds of highly toxic 123 nitrogen contaminations (NOx), the primary photochemical smog (O 3 ) 124 precursor are emitted from mobile sources. O 3 is also the third largest GHG in terms of radiative forcing (RF). 125 Nearly half of all Americans live within ‘maximum exposure’ to near-roadway pollution or within close proximity to high AADT volume roads, according to the most recent U.S. Census. 126 The word “smog” was coined to describe the combination of smoke and fog that shrouded London in the 1950’s. The primary causes of these noxious clouds historically have been factory-produced sulfur dioxide (SO 2 ) and traffic-related NOx. 122 EPA: Fast Facts on Transportation Greenhous Gas Emissions, www.epa.gov . 123 Downs JW, Nitrogen Dioxide Toxicity , National Institutes of Health (NIH), 2022; EPA 124 EPA: List of Extremely Hazardous Substances, www.epa.gov . 125 Lammel G & Grabi H, Greenhouse effect of NOx, Environmental Science and Pollution Research (ESPR) , July 1995. 126 U.S. Census Blocks 2010, U.S. Census Bureau, www.censes.gov ; and U.S. Department of Transportation, Federal Highway Administration (FHWA), Average Annual Daily Traffic Data (AADT), www.fhwa.dot.gov .