A new study shows that tailpipe emissions are declining, but brake and tire wear particle emissions remain a persistent – and unregulated – air quality concern

A new study shows that tailpipe emissions are declining, but brake and tire wear particle emissions remain a persistent – and unregulated – air quality concern

Air Pollution Near Roads is Changing

DECEMBER 5, 2022
RENO, Nevada

By Elyse DeFranco

Air Pollution
Roadways
Emissions

Above: Rush hour traffic with thick smog. Even as emissions from engine exhaust decline with stringent regulations and the growing popularity of electric vehicles, other traffic-related pollution remains unaddressed. Of particular concern are the microscopic particles from brakes and tires, worn down from abrasion and degradation, which mix into the air we breathe and wash into our watersheds, creating hazards for human and environmental health. 

Credit: Photo by plherrera, iStock. 

A new study shows that tailpipe emissions are declining, but brake and tire wear particle emissions remain a persistent – and unregulated – air quality concern

Air pollution near roads remains a significant health concern in the U.S., with an estimated 60 million people living within 500 meters of a major highway. Even as emissions from engine exhaust decline with stringent regulations and the growing popularity of electric vehicles, other traffic-related pollution remains unaddressed. Of particular concern are the microscopic particles from brakes and tires, worn down from abrasion and degradation, which mix into the air we breathe and wash into our watersheds, creating hazards for human and environmental health.

In a new study published Nov. 23 in Environmental Pollution, researchers from DRI, UC Riverside, UNLV, and the California Air Resources Board take a closer look at these overlooked pollutants, known as non-tailpipe emissions. With funding from the California Air Resources Board, they placed air quality monitors near two southern California highways and found that air pollutants from brake and tire wear exceed those from engine exhaust.

“We knew that tailpipe emissions are coming down, and that non-tailpipe emissions have been steady or slightly increasing,” says Xiaoliang Wang, Ph.D., Research Professor of Atmospheric Sciences at DRI and the study’s lead author. “But I didn’t realize that it’s already crossing over – that was a surprise.”

California sampling map

Map of roadside sampling locations in Los Angeles, California — one of the most polluted areas in the U.S. 

Credit: Elyse DeFranco/DRI.

Tire wear particles contain rubber and microplastics, as well as thousands of chemicals, some of which are known ecological hazards. Previous research identified one of these chemicals as the primary culprit in the decline of Coho salmon in the Pacific Northwest. And brake pads contain metals and other materials known to be harmful to human health. Non-tailpipe emissions like brake and tire wear particles aren’t regulated the way engine exhaust is, and are expected to become the primary source of particulate matter pollution near roads.

“There is increasing interest in understanding how much non-tailpipe emissions – including brake wear, tire wear, road surface wear, and road dust – are impacting air pollution for people living close to roadways,” Wang says. “This has environmental justice implications as well because many low-income communities tend to live closer to roads.”

The Environmental Protection Agency (EPA) established a near-road air monitoring network that measures nitrogen dioxide (which causes respiratory tract damage and can trigger asthma), but fine and coarse particles that are more related to non-tailpipe emissions than engine exhaust are monitored spottily or not at all.

California has led the way in enacting regulations on exhaust emissions, as Los Angeles first began experiencing smog-choked air in the 1940s. It wasn’t until the early 1950s that scientists discovered that motor vehicles were the primary source of this smog, and that engine exhaust chemically reacts with sunlight and industrial air pollution to create what is known as “secondary pollutants.” This means that air pollution isn’t merely the combination of all added pollutants, but that as these pollutants intermix in the air, new pollutants are born.

Electric vehicles have eliminated tailpipe emissions by transferring their emissions to their power source, but are heavier than conventional gasoline and diesel-powered vehicles. This could mean more road and tire wear particle emissions.

“There’s still active research going on trying to understand what’s the impact of electrification of vehicles on non-tailpipe emissions,” Wang says. Previous research has noted that because electric vehicles don’t reduce non-tailpipe particulate matter emissions, they shouldn’t be considered as the single and only solution to urban air pollution.

Although this study focused on air pollution near roads, Wang notes that the pollutants don’t stay only near highways, but follow wind patterns to become part of the overall air pollution mix, and eventually get washed into storm gutters and out to sea.

The study team is continuing this research to better understand the chemicals in the air samples they collected and will publish a more detailed analysis of the sources. The information will be provided to appropriate environmental and transportation agencies to aid decision-making for air quality improvements.

More on this study:

Evidence of non-tailpipe emission contributions to PM2.5 and PM10 near southern California highways
Environmental Pollution
https://doi.org/10.1016/j.envpol.2022.120691

Study authors include DRI researchers Xiaoliang Wang, Steven Gronstal, Judith C. Chow, Steven Sai Hang Ho, and John G. Watson; UC Riverside researchers Brenda Lopez, Guoyuan Wu, and Heejung Jung; UNLV researcher L.-W. Antony Chen; and Qi Yao and Seungju Yoon of the California Air Resources Board.

DRI project contributes to an air quality win in Jakarta

DRI project contributes to an air quality win in Jakarta

DRI project contributes to an air quality win in Jakarta

Nov 8, 2021
RENO, NV
By Kelsey Fitzgerald

Air Quality
Jakarta
Air Pollution

Above:Jakarta, Indonesia is severely polluted by sources that include vehicle emissions, factories, and coal-fired power plants.

Credit: Arnaud Matar, Flickr Image.

From Nevada to Jakarta, the work of DRI scientists often has long-lasting impacts in far-off places. This fall, scientists Alan Gertler, Ph.D., John Watson, Ph.D., Judith Chow, Sc.D., Sarath Guttikunda, Ph.D., and Ricky Tropp, Ph.D., received word that air quality monitoring guidelines and reports from a decade-old project in Indonesia had served a beneficial new purpose: providing key evidence in an important court decision that will require stricter air quality standards in the City of Jakarta.

The City of Jakarta is home to 10 million people, and severely polluted by sources that include vehicle emissions, factories, and coal-fired power plants. Additionally, burning of rainforest to create space for palm oil plantations in the countryside causes air pollution that extends into neighboring countries such as Singapore, Vietnam, Laos, and Thailand. 

air quality training seminar Jakarta

DRI’s John Watson, Ph.D., introduces an air quality training seminar in Jakarta in 2019.

Credit: DRI

In 2011, this DRI team began a multi-year project funded by the U.S. Environmental Protection Agency to develop an urban air quality management program for Jakarta. The first phase of the project consisted of an emissions inventory, an assessment of health impacts of air pollution, development of pollution abatement strategies, upgrading the air quality measurement and management program, training in-country personnel in air quality management, development of an air quality index, and more.

Unfortunately, the second phase of the project, which would have consisted of developing control strategies for emissions reduction and providing air quality information to the public, was never funded.

“Although Phase II of the project was never funded, we did as much as we could with the funding that we had for Phase I,” said Gertler, Principal Investigator and Project Manager for the Jakarta project. “We worked on the project for a number of years and were able to make great progress toward helping stakeholders in Jakarta develop better air quality management capabilities.”

The DRI team completed their work on this project in 2017, but the air pollution problems in Jakarta continued. In 2019, a group of 32 Indonesian citizens decided to take action and filed a lawsuit against Indonesian President Joko Widodo and other top officials for neglecting the citizens’ rights to clean air.

As evidence, the prosecution requested the use of a number of data files and records from DRI’s project. Gertler and Watson were happy to comply – and in September, the court ruled in the Indonesian citizens’ favor, ordering the officials to tighten national air quality standards and fulfill the rights of citizens to a good and healthy environment.

“I’m really glad that someone was able to make use of the work that we did, and that they were successful at winning their case,” said Gertler. “Let’s hope they can make some progress toward cleaner air in Jakarta.”

 

Indonesian air quality monitoring station

John Watson (to left) visits a recently installed Indonesian air quality monitoring station.

Credit: DRI

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About DRI

The Desert Research Institute (DRI) is a recognized world leader in basic and applied environmental research. Committed to scientific excellence and integrity, DRI faculty, students who work alongside them, and staff have developed scientific knowledge and innovative technologies in research projects around the globe. Since 1959, DRI’s research has advanced scientific knowledge on topics ranging from humans’ impact on the environment to the environment’s impact on humans. DRI’s impactful science and inspiring solutions support Nevada’s diverse economy, provide science-based educational opportunities, and inform policymakers, business leaders, and community members. With campuses in Las Vegas and Reno, DRI serves as the non-profit research arm of the Nevada System of Higher Education. For more information, please visit www.dri.edu.

DRI Air Quality Experts Awarded Prestigious Haagen-Smit Prize

DRI Air Quality Experts Awarded Prestigious Haagen-Smit Prize

April 30, 2020 (RENO) – Drs. Judith Chow and John Watson, research professors in the Division of Atmospheric Sciences at the Desert Research Institute in Reno, were awarded Elsevier Publisher’s 2019 Haagen-Smit Prize for outstanding paper published in the journal Atmospheric Environment.

Awarded annually, the Haagen-Smit Prize recognizes two outstanding papers out of the nearly 24,000 articles published in Atmospheric Environment since 2001. The 2019 Prize went to Chow, Watson, and their colleagues for their 1993 paper, “The DRI thermal/optical reflectance carbon analysis system: Description, evaluation and applications in U.S. air quality studies,” which has received more than 925 citations. It is the 12th most cited article in Atmospheric Environment since the journal’s inception.

“This paper has had a major influence on the practice of atmospheric science as evidenced by its very high number of citations,” wrote the Haagen-Smit Prize Committee.

The winning paper by Chow, Watson, and their DRI colleagues describes and evaluates instrumentation and methodology developed at DRI. The DRI Carbon Analyzer instrument and their analytical method was subsequently commercialized and adopted in air quality networks in the United States and other countries, including Canada and China. The resulting measurements have been used to determine the contributions to air pollution from sources like domestic cooking and heating, engine exhaust, wildfires, and other emitters, all of which affect human health, visibility, material soiling, and climate.

“We greatly appreciate this recognition for all of the contributing DRI faculty and staff, including Lyle Pritchett, Cliff Frazier, Rick Purcell, and especially our former Executive Director, the late Bill Pierson,” said Chow. “It illustrates the importance of the team efforts that distinguishes DRI.”

Dr. Ari Haagen-Smit was a pioneering air quality scientist who discovered and elucidated the origins of photochemical smog in southern California. He was a colleague of Dr. Frits Went at the California Institute of Technology, who later joined the DRI faculty and is the namesake of DRI’s Frits Went laboratory. Dr. Went developed methods to measure organic emissions from agricultural crops that Dr. Hagen-Smit applied to the engine exhaust emissions that created the smog.

This award is distinct from the California Air Resources Board’s (ARB) Haagen-Smit Clean Air Awards, often termed the “Noble Prize” of air quality science and policy. Dr. Haagen-Smit was the first ARB chairperson. Dr. Chow received this honor in 2011, and the 2018 award was bestowed on Dr. Watson.

At DRI, Chow leads Environmental Analysis Facility, where she, Watson, and her colleagues develop and apply advanced analytical methods to characterize air pollutants, identify sources and their effects on health, climate, visibility, ecosystems, and cultural artifacts.