Social Disparities in Air Pollution

The air pollution in Salt Lake County, Utah, varies over the year, and at times it is the worst in the United States. The geography traps winter inversions and summertime smog throughout the Salt Lake Valley, but underserved neighborhoods—and their schools—experience the highest concentrations. Previous research has shown pollution disparities using annual averages of PM 2.5 levels, the tiny breathable particles that can damage lungs just hours after exposure. Children are especially at risk and experience more than just health effects; exposure to PM 2.5 affects school attendance and academic success.

A new study utilized a community-university partnership of nearly 200 PM 2.5 sensors through the University of Utah’s Air Quality and U (AQ&U) network. U researchers explored social disparities in air pollution in greater detail than ever before, and their findings reveal persistent social inequalities in Salt Lake County. The paper posted online ahead of publication in the journal Environmental Research. College of Engineering faculty from the School of Computing, chemical engineering, electrical and computer engineering and the Scientific Computing and Imaging Institute were involved in the study.

Locations of the 174 public schools included in the study and the PM2.5 sensors.

The researchers analyzed PM 2.5 levels at 174 public schools in Salt Lake County under three different scenarios: relatively clean, moderate inversion and major inversion days. Schools with predominately minority students were disproportionally exposed to worse air quality under all scenarios. Charter schools and schools serving students from low-income households were disproportionally exposed when PM 2.5 was relatively good or moderate. The findings speak to the need for policies that protect school-aged children from environmental harm.

“The persistence of these injustices—from the pretty clean, but health-harming levels all the way up to the horrific air days—at schools serving racial/ethnic minority kids is unacceptable,” said Sara Grineski, U professor of sociology and environmental studies and senior author of the paper.

The authors expected social disparities on bad air days but were surprised that they persisted on clean air days when PM 2.5 levels are still higher than recommended by the U.S. Environmental Protection Agency.

“What makes this project so novel is the community-U partnership that gave us access to this larger network of sensors and helped provide a detailed study. If we had relied on the Utah Department of Air Quality, we’d only have had two monitors and would have missed the nuanced variability,” said Casey Mullen, a doctoral student at the U and lead author of the study.

A higher-resolution snapshot

The evolution of PM2.5 concentrations throughout Salt Lake County during a pollution event (not included in the study). The west side of the county has persistently higher concentrations under all scenarios.

The worst PM2.5 episodes occur during the winter when cold air settles into the Salt Lake Valley and high-pressure weather systems act as a lid that seals in particulate matter from vehicle exhaust, wood-burning fires and emission from industrial facilities. Locals refer to these periods as inversions, which can last from a few days to a few weeks. The lowest elevations experience high concentrations of PM 2.5 for the longest time, impacting the residential communities disproportionately. The study compared the PM 2.5 levels at 174 public schools in 10-minute increments over two-day periods during each of three events: a major winter inversion (poor air quality), a moderate winter inversion (moderate air quality) and a relatively clean, fall day (good air quality). The extensive AQ&U network made up of 190 PM 2.5 sensors is extremely sensitive—each sensor collects PM 2.5 concentrations every second, then uploads the 60-second to a database that the public can access through the U’s AQ&U website.

The researchers broke down 174 Salt Lake County public schools with respect to race/ethnicity, economic status and student age. They also distinguished among school types: Title I Status (schools serving majority low-income households), charter school and alternative or special education school. The average student body was 31% Hispanic, 15% non-Hispanic minority and 54% white and about 45% of the schools were Title I eligible. Just over half of the schools were primary schools, about 16% were charter schools and about 5% were alternative or special education schools.

During relatively clean air days, racial/ethnic minority students were disproportionally exposed to high concentrations. At the school level, a 21% increase in the proportion of Hispanic students was associated with a 12% increase in concentration of PM 2.5. Charter schools were exposed to 20% higher concentrations of PM 2.5 than non-charter schools. During a moderate air quality day, charter, Title I schools and schools with greater proportions of minority students were exposed to higher concentrations of PM 2.5. During bad air quality days, exposure concentrations were higher for schools with larger proportions of minority students.

“No one has yet looked at school type in terms of environmental justice. Charter schools are a new variable that intrigued us,” said Mullen. “It’s starting to build on some other story that—why did we find these inequities in charter and Title I schools?”

Mean 10-min PM2.5 levels for each 48-hour scenario at the Salt Lake County schools during a clean, moderate winter persistent air pool (PCAP, inversion) and major PCAP event. The bigger the blue dot, the higher the concentration of PM2.5 particles. In all three scenarios, the lowest PM2.5 concentrations were on the south and east side of the study area along the bench where elevation ascends from the valley floor.

Looking forward

This paper is one of many collaborations using the newly established AQ&U network.

“This is the first publication from such a diverse cross-disciplinary partnership arising from AQ&U, although we anticipate this is the first of many,” said Kerry Kelly, assistant professor in the Department of Chemical Engineering and co-author of the study. “We are enthusiastic about ongoing partnerships—to understand the effect of pollution microclimates on asthma exacerbations; to predict the severity of wildfire smoke plumes; and to engage student researchers and community partners in understanding the effect of sound walls on air quality.”

The air quality sensors and the network were built by Kelly; Wei Xing of the U’s School of Computing; Ross Whitaker and Miriah Meyer of the U’s School of Computing and the Scientific Computing and Imaging Institute (SCI); Tofigh Sayahi of the U’s Department of Chemical Engineering; Tom Becnel and Pierre-Emmanuel Gaillardon of the U’s Department of Electrical and Computer Engineering; and Pascal Goffin of SCI, all of whom also co-authored the study.

In future studies, the researchers hope to fill in even more gaps in the sensors to get a better picture of the social inequalities in Salt Lake County and in other areas, especially with regards to school-aged children.

“I see research like this continuing to build a wall of evidence that we have to do better in the way in which we regulate pollution exposure in the U.S. and worldwide,” said Grineski. “Evidence on top of evidence points to us having to do a better job of protecting people, especially kids, from pollution.”

Timothy Collins of the U’s Department of Geography also co-authored the study.

Ed Catmull to Receive Turing Award

The Association for Computing Machinery (ACM) has announced that University of Utah School of Computing alumnus Ed Catmull, co-founder and former president of Pixar Animation Studios, will receive the ACM A.M. Turing Award, referred to as “the Nobel Prize of computing.”

Here is the announcement from ACM.

ACM named Edwin E. (Ed) Catmull and Patrick M. (Pat) Hanrahan recipients of the 2019 ACM A.M. Turing Award for fundamental contributions to 3-D computer graphics, and the revolutionary impact of these techniques on computer-generated imagery (CGI) in filmmaking and other applications. Catmull is a computer scientist and former president of Pixar and Disney Animation Studios. Hanrahan, a founding employee at Pixar, is a professor in the Computer Graphics Laboratory at Stanford University.

Ed Catmull and Pat Hanrahan have fundamentally influenced the field of computer graphics through conceptual innovation and contributions to both software and hardware. Their work has had a revolutionary impact on filmmaking, leading to a new genre of entirely computer-animated feature films beginning 25 years ago with Toy Story and continuing to the present day.


Today, 3-D computer animated films represent a wildly popular genre in the $138 billion global film industry. 3-D computer imagery is also central to the booming video gaming industry, as well as the emerging virtual reality and augmented reality fields. Catmull and Hanrahan made pioneering technical contributions which remain integral to how today’s CGI imagery is developed. Additionally, their insights into programming graphics processing units (GPUs) have had implications beyond computer graphics, impacting diverse areas including data center management and artificial intelligence.

The ACM A.M. Turing Award, often referred to as the “Nobel Prize of Computing,” carries a $1 million prize, with financial support provided by Google, Inc. It is named for Alan M. Turing, the British mathematician who articulated the mathematical foundation and limits of computing.

“CGI has transformed the way films are made and experienced, while also profoundly impacting the broader entertainment industry,” said ACM President Cherri M. Pancake. “We are especially excited to recognize Pat Hanrahan and Ed Catmull, because computer graphics is one of the largest and most dynamic communities within ACM, as evidenced by the annual ACM SIGGRAPH conference. At the same time, Catmull and Hanrahan’s contributions demonstrate that advances in one specialization of computing can have a significant influence on other areas of the field. For example, Hanrahan’s work with shading languages for GPUs, has led to their use as general-purpose computing engines for a wide range of areas, including my own specialization of high-performance computing.”

“Because 3-D computer graphic imagery is now so pervasive, we often forget what the field was like just a short time ago when a video game like Pong, which consisted of a white dot bouncing between two vertical white lines, was the leading-edge technology,” said Jeff Dean, Google Senior Fellow and SVP, Google AI. “The technology keeps moving forward, yet what Hanrahan and Catmull developed decades ago remains standard practice in the field today—that’s quite impressive. It’s important to recognize scientific contributions in CGI technology and educate the public about a discipline that will impact many areas in the coming years—virtual and augmented reality, data visualization, education, medical imaging, and more.”

Background and Development of Recognized Technical Contributions

Catmull received his Ph.D. in computer science from the University of Utah in 1974. His advisors included Ivan Sutherland, a father of computer graphics and the 1988 ACM A.M. Turing Award recipient. In his Ph.D. thesis, Catmull introduced the groundbreaking techniques for displaying curved patches instead of polygons, out of which arose two new techniques: Z-buffering (also described by Wolfgang Straber at the time), which manages image depth coordinates in computer graphics, and texture mapping, in which a 2-D surface texture is wrapped around a three-dimensional object. While at Utah, Catmull also created a new method of representing a smooth surface via the specification of a coarser polygon mesh. After graduating, he collaborated with Jim Clark, who would later found Silicon Graphics and Netscape, on the Catmull-Clark Subdivision Surface, which is now the preeminent surface patch used in animation and special effects in movies. Catmull’s techniques have played an important role in developing photo-real graphics, and eliminating “jaggies,” the rough edges around shapes that were a hallmark of primitive computer graphics.


After the University of Utah, Catmull founded the New York Institute of Technology (NYIT) Computer Graphics Lab, one of the earliest dedicated computer graphics labs in the US. Even at that time, Catmull dreamed of making a computer-animated movie. He came a step closer to his goal in 1979, when George Lucas hired Catmull, who in turn hired many who made the advances that pushed graphics toward photorealistic images. At LucasFilm, Catmull and colleagues continued to develop innovations in 3-D computer graphic animation, in an industry that was still dominated by traditional 2-D techniques. In 1986, Steve Jobs bought LucasFilm’s Computer Animation Division and renamed it Pixar, with Catmull as its President.

One of Catmull’s first hires at Pixar was Pat Hanrahan. Hanrahan had received a Ph.D. in BioPhysics from the University of Wisconsin-Madison in 1985 and had worked briefly at NYIT’s Computer Graphics Laboratory before joining Pixar.

Working with Catmull and other members of the Pixar team, Hanrahan was the lead architect of a new kind of graphics system, which allowed curved shapes to be rendered with realistic material properties and lighting. A key idea in this system, later named RenderMan, was shaders (used to shade CGI images). RenderMan’s functions separated the light reflection behavior from the geometric shapes, and computed the color, transparency, and texture at points on the shapes. The RenderMan system also incorporated the Z-buffering and subdivision surface innovations that Catmull had earlier contributed to the field.


During his time at Pixar, Hanrahan also developed techniques for volume rendering, which allows a CGI artist to render a 2-D projection of a 3-D data set, such as a puff of smoke. In one of his most cited papers, Hanrahan, with co-author Marc Levoy, introduced light field rendering, a method for giving the viewer the sense that they are flying through scenes by generating new views from arbitrary points without depth information or feature matching. Hanrahan went on to develop techniques for portraying skin and hair using subsurface scattering, and for rendering complex lighting effects—so-called global illumination or GI—using Monte Carlo ray tracing.

Hanrahan published his RenderMan research in a seminal 1990 paper that was presented at ACM SIGGRAPH. It would take five more years, however, for the computing hardware to develop to a point where the full-length 3-D computer animated movie Toy Story could be produced using Hanrahan’s RenderMan system.

Under Catmull’s leadership, Pixar would make a succession of successful films using RenderMan. Pixar also licensed RenderMan to other film companies. The software has been used in 44 of the last 47 films nominated for an Academy Award in the Visual Effects category, including Avatar, Titanic, Beauty and the Beast, The Lord of the Rings trilogy, and the Star Wars prequels, among others. RenderMan remains the standard workflow for CGI visual effects.


After he left Pixar in 1989, Hanrahan held academic posts at Princeton and Stanford universities. Beginning in the 1990s, he and his students extended the RenderMan shading language to work in real time on powerful GPUs that began to enter into the marketplace. The programming languages for GPUs that Hanrahan and his students developed led to the development of commercial versions (including the OpenGL shading language) that revolutionized the writing of video games.

The prevalence and variety of shading languages that were being used on GPUs ultimately required the GPU hardware designers to develop more flexible architectures. These architectures, in turn, allowed the GPUs to be used in a variety of computing contexts, including running algorithms for high performance computing applications, and training machine learning algorithms on massive datasets for artificial intelligence applications. In particular, Hanrahan and his students developed Brook, a language for GPUs that eventually led to NVIDIA’s CUDA.

Catmull remained at Pixar, which later became a subsidiary of Disney Animation Studios, for over 30 years. Under his leadership, dozens of researchers at these labs invented and published foundational technologies (including image compositing, motion blur, cloth simulation, etc.) that contributed to computer animated films and computer graphics more broadly. Both Hanrahan and Catmull have received awards from ACM SIGGRAPH, as well as the Academy of Motion Picture Arts & Sciences for their technical contributions.

ACM will present the 2019 A.M. Turing Award at its annual Awards Banquet on June 20 in San Francisco, California.

The A.M. Turing Award, the ACM’s most prestigious technical award, is given for major contributions of lasting importance to computing.

Mary Hall Elected to CRA Board of Directors

After four years serving as an ACM representative on the CRA Board of Directors, Professor Mary Hall was voted in by the CRA member institutions, which is comprised of chairs of computer science departments throughout the country. Professor Hall will serve on the board for three years.

Professor Hall’s term on the CRA Board has provided opportunities for increased visibility to the University of Utah and opened the doors for external opportunities. Professor Hall’s term on the board has provide numerous benefits to the university, including helping to gather data to better prepare undergraduate students for computer science courses, worked in increasing research efforts, and advocated for increased diversity in faculty.

The Computing Research Association (CRA) counts among its members more than 200 North American organizations active in computing research: academic departments of computer science and computer engineering; laboratories and centers in industry, government, and academia; and affiliated professional societies (AAAI, ACM, CACS/AIC, IEEE Computer Society, SIAM USENIX).

CRA works with these organizations to represent the computing research community and to effect change that benefits both computing research and society at large.

The Computing Research Association was formed in 1972 as the Computer Science Board (CSB), which provided a forum for the chairs of Ph.D. granting computer science departments to discuss issues and share information.

Teapot Rendering Competition 2019

Thirteen students with 13 beautiful images and met on December 10th to compete in the annual Teapot Rendering Competition. The competition, which is open to all students who have taken the Ray Tracing for Rendering (CS 6620) course and have written their own rendering software from scratch are allowed to compete. Students present their original scenes rendered with their own software, commemorating the famous Utah Teapot with dazzling visuals!

The rules of the competition are simple: the scenes must be original, they must include at least one visible Utah Teapot model, and the images must be rendered using student’s software. Students entering the competition are permitted to work with other individuals for preparing their scenes and the related artwork, but they must write the rendering software themselves.
This marks the 8th year of the competition, which is organized by Dr. Cem Yuksel.

Link to the winners 2019 Winners