In the mid-1940s, leaves of vegetables growing in Riverside and San Bernardino counties were developing a silver sheen and dying. Thousands of acres of farmland were destroyed. Millions of dollars were lost. Plant scientists at the University of California Citrus Experiment Station in Riverside were intrigued. They experimented with the plants.

For the first time, those scientists linked the dead field crops to a new kind of air pollution: smog. In the following years, the scientists, along with collaborators elsewhere, unraveled the complex chain of reactions that created smog.

Six decades later, long after the Citrus Experiment Station became the University of California, Riverside, groundbreaking air quality research continues on campus. It has led to better yields from vegetable plants and fruit trees, healthier forests, cleaner vehicles and improved public health throughout California, the nation and the world.

Bart Croes, chief of research at the California Air Resources Board (CARB), the state’s air quality regulating agency, said research at UCR has been the “main driver” for understanding the complexities of air pollution and how to control it.

“The range of research has touched on pretty much everything we do,” said Croes, who has worked at CARB since 1981.

Those early plant scientists figured out that sunlight, reacting with hydrocarbons and nitrogen oxides released into the atmosphere, especially by automotive emissions, created smog. Since then, smog, also known as photochemical air pollution, has become a worldwide phenomenon.

That early research helped lead to the creation of the Statewide Air Pollution Research Center (SAPRC) on campus in 1961, just seven years after UCR was established. By connecting plant scientists and atmospheric chemists, numerous groundbreaking discoveries were made at the center, including linking die-offs of pine trees in the San Bernardino National Forest to smog and the development of models that have allowed air pollution control agencies to regulate compounds that create dirty air.

Plant scientists and chemists made steady progress and were joined in 1992 by engineers from the newly established Bourns College of Engineering. Work at the College of Engineering Center for Environmental Research (CE-CERT) has led to more than a dozen state and federal regulatory changes in everything from boat emissions to diesel fuel formulations.

During the past two decades, scientists at CE-CERT and SAPRC, now known as the Air Pollution Research Center (APRC), have jointly worked on projects. Today, much of that research focuses on secondary organic aerosols, which, like ozone, contribute to air pollution. Secondary organic aerosols form the gray haze that can hide the mountains. This research ties into global climate change and public health.

Smog Emergency

The air in Southern California wasn’t always dirty. As railroads opened the region to the rest of the country, the dry crystal-clean air became its unofficial billboard, according to a passage in “Smogtown: The Lung-Burning History of Pollution in Los Angeles” by Chip Jacobs and William J. Kelly.

As health sanitariums popped up in Riverside and Palm Springs, marketers peddled Southern California as a haven where spirits weakened by asthma, bronchitis, tuberculosis and alcoholism would regain their strength.

That quickly changed. The population of Los Angeles spiked in the first half of the 20th century. Factories and freeways were built. Cars were purchased.

Pollutants from those cars and factories were blown east by the marine air flow. Tall mountains, weak winds and little rainfall trapped the dirty air in Riverside and San Bernardino counties. Intense heat and sunlight cooked the pollutants, creating smog.

Sometimes mail delivery was halted because of smog alerts. In the ‘70s the mayor of Riverside petitioned the governor to declare a state of emergency because of air pollution. Eyes stung. Throats burned.

“It’s hard to describe how bad it was,” said Ron Loveridge, the current mayor of Riverside who arrived in the city in 1965 to teach political science at UCR. “It felt like someone was standing on your chest.”

For a long time, smog was the leading issue facing the region. That resulted in a severe handicap in attracting businesses and residents.

But, said Loveridge, because of UCR research that has greatly improved the air quality in the region, that seems to be turning around.

Today, UCR researchers work closely with the South Coast Air Quality Management District (SQAQMD), which regulates air quality in much of Southern California, and the California Air Resources Board (CARB). (Loveridge is a member of the SQAQMD board and is its representative to the CARB board.)

Bob Buster, a member of the Riverside County Board of Supervisors since 1993, agreed with Loveridge that UCR has had a big impact on improving air quality in the state.

“UCR has hit this issue from every angle and made it local,” said Buster, a Riverside native who farms the orange and lemon groves his grandfather planted 75 years ago. “Air is hard to get your fingers around. But UCR made it palatable. UCR made it real.”

Early Work

Ellis Darley, one of the plant scientists at the Citrus Experiment Station, remembers starting to investigate why crops were dying in the late 1940s.

When it was sunny, plants would get damaged, said Darley, who is 95 and lives in Spokane, Wash. But they would remain unblemished on cloudy days. That led to the idea that sunshine combined with car exhaust mixed to form smog, which killed the plants.

“That was very significant,” Darley said. “It told the auto industry they had to control the auto exhaust.”

Darley’s work included a 1951 paper, “Investigation on Injury to Plants from Air Pollution in the Los Angeles Area,” which he co-authored with four others, including A.J. Haagen-Smit, a California Institute of Technology scientist considered the father of air pollution control.

The paper, based on research exposing vegetable plants to substances found in the air in controlled gas chambers at Cal Tech, revealed that certain crops were more susceptible to smog.

As Darley and other plant scientists continued their work, the Citrus Experiment Station became part of UCR when it opened in 1954.

James N. Pitts Jr. was among the inaugural group of faculty. Pitts, an atmospheric chemist who had studied smog, quickly got to know the plant scientists, including Darley.

Pitts, Darley and John Middleton, another plant pathologist at UCR, wrote a proposal to house a center at UCR dedicated to researching and improving air quality.

In 1961, the Statewide Air Pollution Research Center was established at UCR. It was the first university air pollution research center in the country.

“The key to the center was bringing together scientists in various disciplines to understand the fundamental concepts of the reactions occurring,” said Pitts, 90, who retired from UCR in 1988 and is now a research chemist at UC Irvine. “The university made that possible.”

Plant Studies

After the center was created, research on the impact of air pollution on plants continued.

From 1961 to 1967, scientists at the center conducted the first large-scale field study in the country. They built field chambers around lemon and navel orange trees in the Upland/Rancho Cucamonga area. The researchers found fruit yields decreased 35 to 40 percent due to air pollution.

Further study revealed that ozone was the primary component of smog that caused the decreases in productivity. That research gave strong support to efforts to control the primary ozone-forming pollutants, such as motor vehicle exhaust and industrial emissions.

Researchers at the center were also studying the national forests surrounding Riverside and San Bernardino counties, where, beginning in the 1950s, trees were experiencing a peculiar yellowing of needles.

Between 1967 and 1971, research initiated by the U.S. Forest Service at the Statewide Air Pollution Research Center on the UCR campus, documented for the first time that smog was killing trees in Los Angeles basin mountains and on the west side of the southern Sierra Nevada.

Further research, including an aerial photographic survey in 1969, showed that certain trees, particularly ponderosa and Jeffrey pines, were very sensitive to smog. Of nearly 161,000 acres surveyed, nearly 1.3 million trees were affected by air pollutants: 82 percent moderately, and 15 percent severely; 3 percent had died.

The late Paul R. Miller, a research plant pathologist at UCR from 1966 to 1998, led that work. Miller was also a U.S. Forest Service scientist.

“His discovery linking ozone in photochemical smog to the dieback of trees in the mountains is one of the most important in the science of air pollution effects on plants,” said Andrzej Bytnerowicz, who worked with Miller after arriving at UCR from Poland as a Fulbright Scholar in 1981.

Bytnerowicz, who has been an ecologist at the U.S. Forest Service’s Pacific Southwest Research Station in Riverside since 1990, said Miller’s work has been cited hundreds of times, been used as a model for research in the United States, Europe and other parts of the world, and led to changes in management of forest impacted by air pollution.

The Chemistry of Air Pollution

Meanwhile, research on the atmospheric chemistry of air pollution was ramping up at the Statewide Air Pollution Research Center.

In 1970, scientists at the center designed and built a 5,800-liter environmental chamber-solar simulator facility in Fawcett Laboratory to investigate the chemistry of smog. At the same time, a group of chemists — including Karen Darnall, Arthur Winer, Alan Lloyd, Paul Bekowies, John McAfee and George Doyle — were hired to perform experiments in the chamber.

Research in the chamber led to the identification of how emitted compounds react to pollute the air, techniques to estimate the amount of pollution those compounds form and the development of models to predict air pollution.

Croes, the chief of research at the California Air Resources Board, credits Pitts for pushing the science that has made cars more than 99 percent cleaner today compared with the 1960s. That has resulted in an 80 percent cut in ozone levels in the Los Angeles basin, despite a doubling of the population and quadrupling of the number of vehicles.

Despite political and scientific opposition, Pitts argued that it was oxides of nitrogen (NOx), not hydrocarbons, that needed to be regulated, Croes said. CARB followed Pitts’ recommendation and enacted regulations that limited NOx emissions. Following CARB, the Environmental Protection Agency and regulatory agencies worldwide started doing the same.

“We really stuck the line there and I give those guys in Riverside all the credit,” said Croes, who also credited UCR atmospheric chemists Roger Atkinson and William P. L. Carter.

Carter, who was born in Oregon and grew up in Eureka, arrived at UCR in 1973. He said he liked the smell of ozone because it reminded him of his grandparents who, as a child, he visited in Southern California.

Years of work by Carter, with help from others at the Statewide Air Pollution Research Center — including Atkinson, Ernesto Tuazon, Janet Arey, Alan Lloyd and Arthur Winer — resulted in the SAPRC 1990 mechanism, a major advance over previously available mechanisms to calculate which volatile organic compounds had the highest ozone-forming potential. Carter continually updates the model, most recently in 2007.

Carter’s findings are key elements in urban and regional airshed models used by air pollution agencies, including the California Air Resources Board, to improve air quality. The Environmental Protection Agency encourages people to take reactivity differences of compounds into account in ozone regulations, but doesn’t require it, Carter said.

Progress in Better Air Quality

In 1992, Carter was among the founding researchers at CE-CERT, which was created to serve as a model for partnerships among industry, government and academia.

Researchers at CE-CERT are focused on taking fundamental work done by scientists at places such as the Air Pollution Research Center and applying it to real-world situations.

Joe Norbeck, professor of chemical and environmental engineering, was the first director of CE-CERT. When he arrived from the Ford Motor Co., where he led the research staff in the chemistry department, he had no staff, no building and no funding.

Today, about 140 faculty, staff and students carry out about $8 million in research annually at CE-CERT, a three-building complex about two miles north of campus.

Three main areas of research at CE-CERT are transportation systems, atmospheric processes, and emissions and fuels.

Matt Barth, the current director of CE-CERT and a professor of electrical engineering, leads the transportation systems research group, which, among other projects, aims to predict the air quality impact of transportation systems.

In the late 1990s, Barth developed the Comprehensive Modal Emissions Model, which allows for the evaluation of emissions benefits of everything from HOV lanes to electronic toll collection to traffic signal coordination.

More recently, Barth has been working to create technology that weds real-time traffic data collection systems with models that predict fuel consumption in vehicles under varying conditions. The goal is to inform drivers of the route that uses the least fuel and produces the smallest amount of carbon emissions.

In atmospheric processes, much attention is focused on secondary organic aerosols, which form the smallest particles that contribute to air pollution and are believed to have the greatest health impact. After scientists developed a strong understanding of ozone formation, many now focus their research on secondary organic aerosols.

Carter is one of them. He is working with David Cocker, a UCR associate professor of chemical and environmental engineering who worked for Carter as an undergraduate in the early 1990s and is now an associate professor; and Paul Ziemann, a professor of chemistry and current director of the Air Pollution Research Center.

Ziemann’s research into the fundamentals of secondary organic aerosol formation is helping Carter and Cocker develop a reactivity model for secondary organic aerosols formed from volatile organic compounds. Like the reactivity model Carter created for ozone formation from these compounds, the model for secondary organic aerosols would help regulators develop effective and efficient ways to control aerosols.

In emissions and fuels research, CE-CERT got started by measuring car emissions. As cars continued to get cleaner, testing has shifted to trucks, trains and boats, particularly those in the ports of Los Angeles and Long Beach, which are significant sources of air pollution in Southern California. CE-CERT engineers have created unique portable testing devices to allow measurements to be taken as trucks and boats travel on roads and water.

Driving Regulations

This research has led to regulatory changes, including barring buses from idling when waiting for children and requiring street sweepers to reduce emissions, said Dennis Fitz, the deputy director and leader of the atmospheric processes group at CE-CERT.

Emissions testing has expanded to include everything from prescribed burns of wildlands at military bases to grilling cheese quesadillas under a contract with Chipotle Mexican Grill. It has also taken researchers to Thailand and China, where, among other things, CE-CERT scientists did traffic modeling prior to the Beijing Olympics in 2008.

In November, CE-CERT launched the Center of Excellence in Alternative Transportation Fuels Research. It builds on the 20 years of expertise that researchers at the center have developed in emissions, fuels and transportation systems research.

The center recently received a $1.2 million grant from the California Energy Commission to characterize emissions and performance of new alternative fuels, such as butanol, and ensure that the fuels will not have adverse health or environmental impacts, said Tom Durbin, a research engineer in the vehicle emission group at CE-CERT.

This is the latest initiative that allows UCR to remain at the forefront of research focused on cleaning up the air.