US cities could see a decline in mortality rates and an improved economy through midcentury if federal and local governments maintain stringent air pollution policies and diminish concentrations of diesel freight truck exhaust, according to a new study published in Environment International by researchers at Cornell University, the University of Houston and Changsha University of Science and Technology, China.
Freight transportation is a pillar of the US national economy, but while long-haul trucks account for less than 6% of the vehicle miles traveled over US highways, they account for about 40% of the emissions of air polluting particulate matter and about 55% of nitrogen oxides, the precursor to ozone in the atmosphere, the study said.
The researchers examined the air quality and public health impacts of projected freight-related emissions in 2050 over the continental United States. Three emission scenarios were considered:
A projected business-as-usual socioeconomic growth with freight fleet turnover and stringent emission control (CTR);
The application of a carbon-pricing climate policy (PO); and
Further technology improvements to eliminate high-emitting conditions in the truck fleet (NS).
The PO and NS cases are superimposed on the CTR case.
Using a modeling framework, the researchers quantified the impacts of PM2.5 emissions change on air quality, health, and economic benefits.
In the CTR case, they simulated a widespread reduction of PM2.5 concentrations, between 0.5 and 1.5 μg m−3, comparing to a base year of 2011. This translates into health benefits of 3600 (95% CI: 2400–4800) prevented premature deaths, corresponding to $38 (95% CI: $3.5–$100) billion.
Compared to CTR case, the PO case can obtain ~9% more health benefits nationally, however, climate policy also affects the health outcomes regionally due to transition of demand from truck to rail; regions with fewer trucks could gain in health benefits, while regions with added rail freight may potentially experience a loss in health benefits due to air quality degradation.
The NS case provides substantial additional benefits (~20%).
Source: Pan et al.
These results support that a combination of continuous adoption of stringent emission standards and strong improvements in vehicle technology are necessary, as well as rewarding, to meet the sustainable freight and community health goals. States and metropolitan areas with high population density and usually high freight demand and emissions can take more immediate actions, such as accelerating vehicle technology improvements and removing high-emitting trucks, to improve air quality and health benefits.—Pan et al.
While current federal regulations have emissions limits on new vehicles, the regulations do not affect vehicles already in use, said senior author Oliver Gao, Cornell professor of civil and environmental engineering. Aging trucks, however, can easily degrade from normal to high-emitting conditions. Eliminating super-emitting vehicles completely could further reduce long-haul freight emissions by nearly 70% and provide 20% more health benefits, the researchers said.
The work was supported in part by the US Department of Transportation's Center for Transportation, Environment and Community Health, and the National Science Foundation.
Shuai Pan, Anirban Roy, Yunsoo Choi, ShiQuan Sun, H. Oliver Gao (2019) “The air quality and health impacts of projected long-haul truck and rail freight transportation in the United States in 2050,” Environment International, Volume 130, 104922 doi: 10.1016/j.envint.2019.104922.