Contribution of on-road transportation to PM(2.5)

Fine particulate matter (PM(2.5)) mainly originates from combustion emissions. On-road transportation is considered one of the primary sources of PM(2.5) emission. The relationship between on-road transportation and PM(2.5) concentration varies temporally and spatially, and the estimation for this variation is important for policymaking. Here, we reveal the quantitative association of PM(2.5) concentration with on-road transportation by the spatial panel Durbin model and the geographical and temporal weighted regression. We find that 6.17 billion kilometres (km) per km(2) on-road transportation increase is associated with a 1-μg/m(3) county-level PM(2.5) concentration increase in the contiguous United States. On-road transportation marginally contributes to PM(2.5), only 1.09% on average. Approximately 3605 premature deaths are attributed to PM(2.5) from on-road transportation in 2010, and about a total of 50,223 premature deaths ascribe to PM(2.5) taking 6.49% from 2003 to 2016. Our findings shed light on the necessity of the county-level policies considering the temporal and spatial variability of the relationship to further mitigate PM(2.5) from on-road transportation.