Research reveals diesel exhaust dirtier, more damaging to health than previously thought

“New study quantifies global health, environmental impacts of excess nitrogen oxide emissions from diesel vehicles” is the title of a May 15, 2017 press release from the International Council on Clean Transportation (ICCT).

In no uncertain terms the ICCT announced, “[b]oth light-duty and heavy-duty diesel vehicles emit more NOx in on-road driving conditions than during laboratory certification testing, for reasons that may range from details of the engine calibration to equipment failure, inadequate maintenance, tampering by vehicle owners, the deliberate use of defeat devices, or simply deficient certification test procedures.”

Startling findings

The study’s findings are startling and should be a wake-up call.

The ICCT in its press statement is emphatic in its observation that, “[n]itrogen oxide (NOx) emissions from diesel cars, trucks, and buses are a major contributor to air pollution-related deaths worldwide—and the impacts are increasing, despite regulatory limits.”

Globally, according to the ICCT, an estimated 107,626 premature deaths were attributed to on-road diesel vehicle NOx emissions in 2015. China had the most with 31,397. This was followed by the EU-28 which recorded 28,456 such deaths, with India’s 26,739 ranking third.

What is indeed eye-opening are Mexico’s figures. Though there were 907 such on-road, diesel-vehicle, NOx-attributed deaths (estimate), a whopping 84 percent were tied to “NOx within regulated limits.” Fifteen percent are linked to “Excess NOx from trucks and buses.”

In the U.S., meanwhile, where an estimated 2,982 such deaths were registered in 2015, the percentage breakdown is as follows: 63 percent “NOx within regulated limits,” 34 percent “Excess NOx from trucks and buses,” and three percent “Excess NOx from cars and vans.”

The International Council on Clean Transportation in the release had far more to say on this. “The study estimates that excess diesel vehicle NOx emissions in 2015 were linked to ~38,000 premature deaths worldwide—mostly in the European Union, China, and India. ‘The consequences of excess diesel NOx emissions for public health are striking,’ says Susan Anenberg, co-lead author of the study and co-Founder of Environmental Health Analytics, LLC. ‘In Europe, the ozone mortality burden each year would be 10% lower if diesel vehicle NOx emissions were in line with certification limits.’” NOx is a key contributor in the formation of both “ground-level ozone and secondary fine particulate matter (PM2.5),” in air pollution outdoors.

More of the study’s findings revealed that in the European Union, in 2015, diesel-produced NOx emissions in excess from light-duty diesel vehicle exhaust accounts for six in 10 early deaths. An estimated 1,100 premature deaths in the U.S. from excess diesel-produced NOx occurred “in 2015, where heavy-duty diesel vehicles caused 10 times the impact of light-duty diesel cars.” Furthermore, though certified under laboratory testing in terms of meeting mandatory emissions limits, these same vehicles under real-world operating testing conditions, “produced 2.3 times NOx emission limits for light-duty diesel vehicles and 1.45 times limits for heavy-duty diesel vehicles, on average,” the ICCT went on in the release to report.

Two Cycle Diesel engine with Roots blower

The best way to lessen the impact of excess diesel-vehicle-emitted NOx on health is apparently through implementation and enforcement of stringent specified standards.

Ray Minijares, a study co-author and an ICCT Clean Air Program Lead, who was quoted in the release, said: “‘Globally, the single most important action to reduce the health impacts of excess diesel NOx emissions is for countries to implement and properly enforce a EURO VI tailpipe emission standard for heavy-duty vehicles. Combined with strengthened compliance for light-duty vehicles and next-generation standards, this would nearly eliminate real-world NOx emissions from diesel vehicles, which would avoid 174,000 air pollution-related deaths and 3 million years of life lost worldwide in the year 2040’ …”

The ICCT in the release further pointed out that, “[t]he study combined results from in-use vehicle emissions testing studies with global atmospheric modeling, satellite observations, and health, crop yield, and climate models to estimate the damages caused by diesel NOx emissions.”

For more about the International Council on Clean Transportation, the study (“The Global Health and Environmental Impacts of Excess Diesel NOx Emissions in 11 Major Vehicle Markets” and corresponding fact sheet) and information in the May 15, 2017 ICCT press release, see: “New study quantifies global health, environmental impacts of excess nitrogen oxide emissions from diesel vehicles” here.

Diesel particulate filter

Images: Pearson Scott Foresman (middle); Dana60Cummins (lower)

This post was last revised on Dec. 9, 2020 @ 1:07 p.m. Pacific Standard Time.

Published by Alan Kandel