2015

On-board school bus filtration system reduces pollutants by 88 percent


Technology developed for school buses, if implemented, would protect children from harmful exposure to vehicular pollution.

Yifang Zhu
Dr. Yi-Fang Zhu, the study's senior author

An on-board air filtration system developed specifically for school buses reduces exposure to vehicular pollutants by up to 88 percent, according to a study by researchers at the UCLA Fielding School of Public Health.

The high-efficiency cabin air, or HECA, system could help protect the 25 million American children who commute on school buses nearly every day. Children are more susceptible to air pollution than adults because they breathe more quickly and their immune and cardiovascular systems are still developing, said Dr. Yifang Zhu, the study’s senior author and an associate professor in the Fielding School’s Department of Environmental Health Sciences.

Pollution reduction was even greater under freeway driving conditions, which was surprising because freeways have particularly high pollutant concentrations due to traffic congestion and increased emissions. The study found that the air inside buses with the HECA system was as clean as air near the beach in Santa Monica, California.

The study appears today in the early online edition of the peer-reviewed journal Environmental Science and Technology.

“During school bus commuting, children can be exposed to significantly greater levels of air pollutants than a typical resident in the South Coast air basin,” Zhu said. The South Coast air basin encompasses all of Orange County, California, and the non-desert regions of Los Angeles County, Riverside County, and San Bernardino County. 

“Studies have shown that exposure to high levels of vehicle pollution is associated with pulmonary and cardiovascular health risks, including oxidative stress, mitochondrial damage and acute pulmonary inflammation,” she said.

Studies have also found that children exposed to pollutants from vehicles tend to perform less well in school.

The new study tested six school buses without children on board while the buses were still, and while they were driving on freeways and major arterial roadways in Los Angeles. Researchers tested the air both inside and outside of the buses for vehicle-emitted particulate matter, including black carbon and fine and ultrafine particles, down to a few nanometers in size.

A study funded by the California Air Resources Board more than a decade ago was the first to find serious air quality problems inside diesel-powered school buses. That study led to efforts to retrofit school buses with exterior pollution-reducing devices. While that method is promising for minimizing emissions from buses’ tailpipes, it doesn’t always provide cleaner air inside the buses. A majority of school buses today are not equipped with any interior mechanical filtration systems, said Eon Lee, the study’s first author and a postdoctoral researcher in Zhu’s lab.

A previous study by Zhu and her team found that commercially available household air purifiers can reduce pollutant levels inside school buses by about 50 percent. However, they are not designed to work in moving vehicles.

As part of the new study, researchers developed a prototype on-board HECA filtration system for buses and installed two in the rear of each of the six buses tested. Air was drawn in through diffusers on the sides of each unit and fed through the HECA filter. The filtered air was then delivered at a constant rate through air ducts.

HECA filtration system graphic
Diagram of HECA filtration system

“School buses are by far the safest way to transport children between school and home,” Zhu said. “Our goal is to make it also the cleanest way.”

A long-term follow-up study will evaluate how much exposure can be reduced by operating the HECA filtration system in a large number of school buses with children aboard, Zhu said.

“The developed HECA filtration system has great potential to substantially reduce children’s exposure to vehicle pollutants while commuting inside school buses,” the study states.

The study was funded by the California Air Resources Board. The HECA filtration system was developed in collaboration with IQAir North America.

Read the full story

Faculty Referenced by this Article

Dr. Yifang Zhu
Yifang Zhu
Environmental Health Sciences
Read Faculty Profile
Jian Li
Jian Li
Environmental Health Sciences Epidemiology
Read Faculty Profile
Dr. Wendie Robbins
Wendie Robbins
Environmental Health Sciences
Read Faculty Profile
Rachael Jones
Rachael Jones
Environmental Health Sciences
Read Faculty Profile
Jared Diamond
Jared Diamond
Environmental Health Sciences
Read Faculty Profile
Angelo J Bellomo
Angelo Bellomo
Environmental Health Sciences
Read Faculty Profile
Dr. Daniel Uslan
Daniel Uslan
Environmental Health Sciences
Read Faculty Profile
Dr. Robert Schiestl
Robert Schiestl
Environmental Health Sciences
Read Faculty Profile
Faculty/staff profile placeholder image
Jesus Araujo
Environmental Health Sciences
Read Faculty Profile
Feng Gao
Feng Gao
Environmental Health Sciences
Read Faculty Profile
Arthur Cho
Arthur Cho
Environmental Health Sciences
Read Faculty Profile
Michael Collins
Michael Collins
Environmental Health Sciences
Read Faculty Profile
Tao Huai
Tao Huai
Environmental Health Sciences
Read Faculty Profile
Richard Ambrose
Richard Ambrose
Environmental Health Sciences
Read Faculty Profile
Faculty/staff profile placeholder image
Timothy Malloy
Environmental Health Sciences
Read Faculty Profile
Brian Cole
Brian Cole
Environmental Health Sciences
Read Faculty Profile
Dr. Beate Ritz
Beate Ritz
Environmental Health Sciences Epidemiology
Read Faculty Profile
Andre Nel
André Nel
Environmental Health Sciences
Read Faculty Profile
Dr. Kevin Njabo
Kevin Njabo
Environmental Health Sciences
Read Faculty Profile
Dr. Oliver Hankinson
Oliver Hankinson

Dr. Hankinson is a Distinguished Professor of Pathology and Laboratory Medicine, and of EHS, and Chair of the Molecular Toxicology IDP

Environmental Health Sciences
Read Faculty Profile
Mel Suffet
Irwin Suffet
Environmental Health Sciences
Read Faculty Profile
Dr. Jane Valentine
Jane Valentine
Environmental Health Sciences
Read Faculty Profile
Dr. Lara Cushing
Lara Cushing
Environmental Health Sciences
Read Faculty Profile
Arabzadah, Hamid
Hamid Arabzadeh
Environmental Health Sciences
Read Faculty Profile
Dr. Pouran D. Faghri
Pouran D. Faghri
Environmental Health Sciences
Read Faculty Profile
Pablo Cicero-Fernandez
Pablo Cicero-Fernandez
Environmental Health Sciences
Read Faculty Profile
Curtis Eckhert
Curtis Eckhert
Environmental Health Sciences
Read Faculty Profile
Faculty/staff profile placeholder image
Arthur Winer
Environmental Health Sciences
Read Faculty Profile
Dr. Candace Tsai
Candace Tsai

Associate Professor for Industrial Hygiene and Environmental Health Sciences

Environmental Health Sciences
Read Faculty Profile
Rosenstock
Linda Rosenstock
Environmental Health Sciences Health Policy and Management
Read Faculty Profile
Michael Jerrett
Michael Jerrett
Environmental Health Sciences
Read Faculty Profile
Faculty/staff profile placeholder image
Nicole Green
Environmental Health Sciences
Read Faculty Profile
Dr. Shane Que Hee
Shane Que Hee

Industrial Hygiene & Analytical Chemistry

Environmental Health Sciences
Read Faculty Profile
Richard J. Jackson
Richard J. Jackson
Environmental Health Sciences
Read Faculty Profile
Faculty/staff profile placeholder image
Niklas Krause
Environmental Health Sciences Epidemiology
Read Faculty Profile
Faculty/staff profile placeholder image
Kirsten Schwarz
Environmental Health Sciences
Read Faculty Profile
Miriam Marlier
Miriam Marlier
Environmental Health Sciences
Read Faculty Profile