The transportation industry is one of the most polluting industries contributing to air pollution around the world as well as adding greenhouse gases into the atmosphere. However, there has been a bit of good news, so let’s celebrate this moment and then keep advocating for better ways to help our planet and the people on it.
The Associated Press reports that researchers at Harvard University found that deaths dropped from 27,000 in 2008 to 19,800 in 2017 due to the decline in emissions from vehicles in over a decade. One key thing that happened during this time period was the rise of electric vehicles. In 2017, Tesla was just getting started, and even before Tesla, Nissan had been producing its LEAF EV. Greater fuel efficiency and adoption of hybrid vehicles also played a significant part.
The study, which was published in the Proceedings of the National Academy of Sciences, found that if vehicles had been emitting 2008 levels of air pollutions during this time period, the death total in 2017 would have been 2.4 times higher than it was (48,200, or a 74% increase, rather than 19,800). The study emphasized that decades of air pollution regulation have contributed to many benefits here in the US, but noted that vehicle emissions are still a climate and public health issue.
The study used a combination of counterfactual scenarios, the latest epidemiological evidence, and detailed spatial resolution to analyze recent health benefits related to changes in fine particulate matter (PM2.5) and climate benefits of on-road emission reductions during this time period.
The researchers also emphasized that the health impacts of air pollution from the transportation industry are still a huge problem (19,800 deaths isn’t nothing) and they also continue to contribute to growing climate crisis. Over the years, transportation greenhouse gas emissions have increased, and they were responsible for 28% of US greenhouse gas emissions in 2018.
Also, 83% of transportation greenhouse gases in 2018 came from vehicles, and 70% of vehicle greenhouse gas emissions came from light-duty vehicles. Even though the energy efficiency in light-duty vehicles has increased, decreasing greenhouse gas emissions per mile driven, their overall climate impacts have increased as driving has increased.
In the charts above, you can see detailed data on emissions of greenhouse gases and air pollution by vehicle class listed in four emissions scenarios.
Key reductions included PM2.4 and NOx emissions. Heavy-duty truck emissions were the main source of reductions.
The researchers estimated the social cost of on-road emissions in 2017. This was the sum of monetary damages of mortality caused by PM2.5 and climate change damages. That number was $260 billion. The good news is that the number is low compared to what it could have been if vehicles were still emitting 2008 levels per mile of pollution. That number would have been at least $530 billion.
“Decreases in EFs since 2008 are therefore responsible for benefits of $270 billion per year in 2017, 95% of which is from air pollutants (Fig. 2). We estimate 19,800 deaths attributable to PM2.5 from transportation emissions in 2017, which account for 69% of the current $260 billion impact. This figure would have been 2.4 times as high (48,200 or $440 billion) under 2008 EFs.”
Researchers also found that for each air pollutant type, the percentage decreases in mortality were similar to those in emission. NOx emissions were responsible for 53% of air pollution benefits. However, while there were large reductions, NOx still contributed to 46% of the impacts in 2017. Keep in mind that 2017 was also the time when the “dieselgate” scandal was in the news, and there’s been much reduction in diesel vehicles on US roads since then. The study noted that progress on reducing greenhouse gas impacts has been slower than progress on reducing air pollution.
The study also emphasized that there is a clear need for further public health and climate gains. The results showed this as well as a need for more stringent policies. Although the researchers haven’t conducted a cost–benefit analysis, benefits since 2008 are much larger than all of the 1990 Clean Air Act Amendments compliance costs for on-road vehicles and fuels.
The researchers also pointed out that passenger light-duty vehicles caused a majority of both the public health and climate burden, so focusing on these vehicles would help ease the burdens. You can read the full study report here.
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