Regulating Diesel Emissions: An Environmental Twofer

This toxic emission is not only a threat to public health but also the second largest contributor to global warming, according to CARB. A new study has found that regulations to reduce diesel emissions fight both climate change and air pollution.

3 minute read

June 21, 2013, 8:00 AM PDT

By Irvin Dawid


Peter Fimrite writes about that the three-year study, funded by the California Air Resources Board (CARB) that examined the effectiveness of diesel emission regulations in reducing emissions of black carbon, a major contributor to climate change. CARB has been regulating tailpipe emissions since 1967 to protect public health. Strict, controversial regulations for trucks and buses were approved in December, 2008 and reported here. This study shows how diesel emission regulations protect both climate and health.

The study was the first regional assessment of the effect on the atmosphere of black carbon, the soot particles from burning diesel fuel. Black carbon is the primary ingredient in smog, the clouds of soot that for decades turned the air in Los Angeles and other places brown. ......

Unlike carbon dioxide, the main contributor to climate change which by itself is a harmless gas, black carbon emitted from diesel exhaust poses a serious threat to public health.

  • Diesel particulate matter poses a major threat to the respiratory system.
  • Diesel exhaust is consider a toxic airborne emission, along with formaldehyde and benzene, that are emitted by motor vehicles that pose cancer risks.
    • "EPA has concluded that diesel exhaust is among substances that may pose the greatest risk to the U.S. population," the agency said. (NYT)

In addition to causing health problems, black carbon has been identified as the second-largest contributor to global warming behind carbon dioxide, writes Fimrite, and reported here on January 18.

"We are all breathing cleaner air because of regulations in diesel combustion, but this study shows there was a huge co-benefit of mitigating climate change," said the lead researcher, Veerabhadran Ramanathan, a scientist with the Scripps Institution of Oceanography and UC San Diego. "I'm now very, very interested in taking this message to the rest of the planet, because if the California experience can be replicated around the world, then we can make a substantial dent in climate change." 

"The message, particularly for metropolitan areas in California, is that if you clean up the air to improve air quality you will also protect climate," Ramanathan said. 

From executive summary (PDF, pg. 20): 

Black Carbon emission reductions since the 1980s, attributed in large part to diesel engine emissions mitigation, are equivalent to reducing CO2 emissions by 21 million metric tons annually. This is approximately equal to 5 % of the total direct CO2 annual emissions of 393 million metric tons.

From Scripps news release

“We know that California’s programs to reduce emissions from diesel engines have helped clean up the air and protect public health,” said ARB Chairman Mary D. Nichols. “This report makes it clear that our efforts to clean up the trucks and buses on our roads and highways also help us in the fight against climate change.”

The U.S. Department of Energy’s Lawrence Berkeley National Laboratory (LBNL) and Pacific Northwest National Laboratory also participated in the study.

The study should help the Air Resources Board as it sets out to implement rigorous regulations to reduce diesel emissions from trucks and buses. In addition, for policy makers who are skeptical of climate change, the public health benefits of reducing black carbon might prove less controversial.

Thursday, June 13, 2013 in San Francisco Chronicle

portrait of professional woman

I love the variety of courses, many practical, and all richly illustrated. They have inspired many ideas that I've applied in practice, and in my own teaching. Mary G., Urban Planner

I love the variety of courses, many practical, and all richly illustrated. They have inspired many ideas that I've applied in practice, and in my own teaching.

Mary G., Urban Planner

Cover CM Credits, Earn Certificates, Push Your Career Forward

Logo for Planetizen Federal Action Tracker with black and white image of U.S. Capitol with water ripple overlay.

Planetizen Federal Action Tracker

A weekly monitor of how Trump’s orders and actions are impacting planners and planning in America.

June 11, 2025 - Diana Ionescu

Metrorail train pulling into newly opened subterranean station in Washington, D.C. with crowd on platform taking photos.

Congressman Proposes Bill to Rename DC Metro “Trump Train”

The Make Autorail Great Again Act would withhold federal funding to the system until the Washington Metropolitan Area Transit Authority (WMATA), rebrands as the Washington Metropolitan Authority for Greater Access (WMAGA).

June 2, 2025 - The Hill

Large crowd on street in San Francisco, California during Oktoberfest festival.

The Simple Legislative Tool Transforming Vacant Downtowns

In California, Michigan and Georgia, an easy win is bringing dollars — and delight — back to city centers.

June 2, 2025 - Robbie Silver

Color-coded map of labor & delivery departments and losses in United States.

The States Losing Rural Delivery Rooms at an Alarming Pace

In some states, as few as 9% of rural hospitals still deliver babies. As a result, rising pre-term births, no adequate pre-term care and "harrowing" close calls are a growing reality.

June 15 - Maine Morning Star

Street scene in Kathmandu, Nepal with yellow minibuses and other traffic.

The Small South Asian Republic Going all in on EVs

Thanks to one simple policy change less than five years ago, 65% of new cars in this Himalayan country are now electric.

June 15 - Fast Company

Bike lane in Washington D.C. protected by low concrete barriers.

DC Backpedals on Bike Lane Protection, Swaps Barriers for Paint

Citing aesthetic concerns, the city is removing the concrete barriers and flexposts that once separated Arizona Avenue cyclists from motor vehicles.

June 15 - The Washington Post