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Trainees Expand Research on Pollution Removal Materials (PRMs)


Three Environmental Engineering graduate students who are part of the National Science Foundation’s (NSF) Integrative Graduate Education and Research Traineeship (IGERT) program in Indoor Environmental Science and Engineering at The University of Texas at Austin (UT) are continuing a novel multi-year study of “pollution removal materials” (PRMs) to reduce human exposure to indoor pollutants without an energy penalty. This concept involves the use of architectural materials that can sequester or destroy harmful indoor pollutants without concomitant production of harmful reaction products or the energy penalty associated with most pollution control systems. This work is important for several reasons. First, human exposure to air pollution, even pollution of outdoor origin, is dominated by what is breathed indoors. Second, there is a move toward low to zero-energy buildings in the United States, and to achieve this goal will mean improved pollution control strategies that do not require continuous energy penalties. And third, it looks increasingly possible to use locally-sourced and sustainable materials to remove a spectrum of indoor pollutants.

The PRM research was initiated by IGERT trainee Elliott Gall and affiliate alumnus Donna Kunkel, whose seminal work on the subject was published in the journal Building and Environment. Gall then completed a Monte-Carlo simulation of PRM applications for homes in Houston, Texas, which showed that PRMs can be highly effective at removing ozone from indoor air and, thus, substantially reducing population exposures to ozone. This work was published in the journal Atmospheric Environment.

IGERT affiliate Clement Cros completed a seminal longitudinal study of the effectiveness of several PRMs located at field sites over six month periods. He determined changes in ozone removal effectiveness and primary and second (following oxidation) emissions from PRM materials over that period. He also found associations between PRM effectiveness and location-specific environmental conditions that will help in future applications of PRMs in actual buildings. During the past year affiliate Cros’ efforts led to a paper in the journal Indoor Air that is now receiving substantial attention in the indoor air quality community.

Trainee Erin Darling and affiliate Cros have also studied clay-based wall plaster as a means for removing ozone from indoor air. The benefits of this product are that it is aesthetically pleasing (unlike previously tested PRMs) and can cover large surface areas. Darling completed experiments in the UTest House, a 3 bedroom/ 2 bath test house purchased with funding from the National Science Foundation’s IGERT program; the UTest House has become a major tool used by IGERT trainees and affiliates for their research. Her findings confirmed the value of clay-based wall plaster used on walls in a bedroom. Using discretionary funds made available from the University of Texas, trainee Darling and affiliate Cros were able to travel to and work with internationally-recognized experts on human perception analysis (from Poland and the Czech Republic) and world-class human subject chamber facilities at the Danish Technical University to study human perceptions of air contaminated with ozone, carpet or both, and untreated or treated with gypsum board coated with a clay-based plaster. Twenty-eight panelists were recruited for a multi-week study. Important findings were that polluted air treated by clay-based wall coverings had a statistically improved acceptability rating, and that gender played a major role in acceptability ratings; females were far more sensitive to conditions with pollution sources (higher unacceptability ratings) and clay-based wall coverings (higher acceptability scores). During the past year the results of this study were presented at podium by trainee Darling at Indoor Air 2011, a major international conference. A journal paper on this effort was also recently submitted for review.

Trainee alumnus Gall, trainee Darling, and affiliate Cros are each continuing their research of PRMs. Gall is continuing his work to better understand the role of material porosity on enhanced removal of ozone to PRMs, and has designed and is using a novel experimental system for studying ozone diffusion/reaction depths into materials. Cros is now studying the application of PRMs to remove nitrogen dioxide and ozone on the external facades of buildings prior to penetration through building envelopes, an effective external microenvironment protection outside of buildings. Darling is studying a wider range of earthen-based materials for removal of both ozone and polar VOCs, with applications including passive removal in sleep environments, e.g., headboards on beds.

Address Goals

While past research has been completed on the removal of ozone to indoor materials, our studies are the first to systematically explore the strategic use of selective materials for lowering population exposures to ozone while reducing background levels of potentially harmful by-products that are formed when ozone reacts with indoor surfaces. IGERT trainees and affiliates are now world leaders on this important topic. They are the first to calculate the extent to which this strategy can reduce ozone exposures. In the past year trainees and affiliates have moved on to studying PRM applications for a broader range of pollutants. Their collective findings and contributions relate to the goal of discovery. Furthermore, four past or present IGERT graduate students and an undergraduate student whom they have mentored have engaged in learning related to laboratory and field experimental methods, engineering analysis, surface chemistry, and fluid mechanics. All of these students have presented their results at major international conferences and have spoken to the public about their findings. Because of trainee Erin Darling’s work, clay-based wall coverings have been adopted for use by the University of Texas (UT) Energy Institute and may also be adopted for expanded use through a major sustainability initiative for buildings on the UT campus; The UT campus is benefitting in new ways by learning from trainees in the IGERT program on Indoor Environmental Science and Engineering. And finally, the American Society for Heating, Refrigerating, and Air Conditioning Engineers (ASHRAE), a major standards-based organization, recently put out a request for proposals that specifically mentions PRMs, a concept developed as a result of our IGERT program.