Source: adapted from K. Button, Center for Transportation Policy, Operations and Logistics, George Mason University, Lecture Notes.
The spatial and temporal dimensions are important to consider when assessing the impacts of environmental externalities, such as pollutants. The more extensive the spatial and the temporal dimensions, the more difficult it is to link a pollutant to quantifiable environmental externalities.
While noise, particulates, and carbon monoxide emissions are clearly linked to harmful environmental and health impacts, linking CO2 to climate change, which is a global and intergenerational issue, is more complex. Even labeling CO2 as a “pollutant” is subject to controversy since it is a gas that occurs naturally in physical and biological processes.