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Shelly Miller discusses the major factors in our indoor air quality, and how small changes can help indoor air quality in our homes. Air quality expert Shelly Miller says small changes can foster healthy indoor environments.

WRITTEN BY ERIC FEEZELL | PHOTO BY GLENN ASAKAWA

DURING HIGH SCHOOL, SHELLY MILLER ’86 was routinely sent home early.

In the thickly polluted Southern California of Miller’s youth, “high-ozone days” were frequent, and schools often dismissed prematurely, limiting sports and other outdoor activities. The San Gabriel Mountains that on a clear day tower above the valley could be nearly imperceptible behind the dull, smoggy haze.

It made an impression.

“I grew up in air quality that was terrible,” says Miller. “The fact that we struggled so much with it made me want to figure out: why?”

She’s been good to her word. Now a professor of mechanical engineering at University of Colorado Boulder (CU) and an affiliate of the CU-Denver School of Public Health, Miller is researching the sources and health effects of urban air pollution. She also studies how to control it. Her most recent project focuses on understanding climate change’s effects on indoor air quality (IAQ). She’s the principal investigator on a three-year, $1 million Environmental Protection Agency (EPA) project examining how residential weatherization— structural modification that helps optimize energy consumption and efficiency—impacts air quality in low-income Denver residences.

Shelly Miller more recent papers:

PAPER 1: Comparisons of urban and rural PM10−2.5 and PM2.5 mass concentrations and semi-volatile fractions in northeastern Colorado
Nicholas Clements¹, Michael P. Hannigan¹, Shelly L. Miller¹, Jennifer L. Peel², and Jana B. Milford^1
1Department of Mechanical Engineering, College of Engineering and Applied Science, University of Colorado Boulder, Boulder, CO, 80309-0427, USA

²Department of Environmental and Radiological Health Sciences, Colorado State University, Fort Collins, CO, 80523, USA

Coarse (PM10−2.5 ) and fine (PM2.5 ) particulate matter in the atmosphere adversely affect human health and influence climate. While PM2.5 is relatively well studied, less is known about the sources and fate of PM10−2.5. The Colorado Coarse Rural-Urban Sources and Health (CCRUSH) study measured PM10−2.5 and PM2.5 mass concentrations, as well as the fraction of semi-volatile material (SVM) in each size regime (SVM2.5, SVM10−2.5), from 2009 to early 2012 in Denver and comparatively rural Greeley, Colorado. Agricultural operations east of Greeley appear to have contributed to the peak PM10−2.5 concentrations there, but concentrations were generally lower in Greeley than in Denver. Traffic-influenced sites in Denver had PM10−2.5 concentrations that averaged from 14.6 to 19.7μgm−3 and mean PM10−2.5 / PM10 ratios of 0.56 to 0.70, higher than at residential sites in Denver or Greeley.

PAPER 2: Ultraviolet germicidal coil cleaning: Decreased surface microbial loading and resuspension of cell clusters
Julia C. Luongo, Shelly L. Miller*
Department of Mechanical Engineering, University of Colorado Boulder, 1111 Engineering Drive, 427 UCB, Boulder, CO 80309, USA

Cooling coil surfaces within building ventilation systems are ideal sites for biofilm formation due to the presence of adequate nutrients (deposited particles) and moisture (condensate). In this study, a heating, ventilation, and air-conditioning (HVAC) test apparatus was built consisting of two parallel ducts, each with its own cooling coil. One coil was exposed to ultraviolet germicidal coil cleaning (UVG-CC) while the other was the comparison control to investigate the impact of UVG-CC on surface microbial loading and bacterial attachment. Surface samples were collected by swabbing a uniform area of coil surface and airborne samples were collected isokinetically with sterile funnel filters. All samples were quantified via direct epifluorescent microscopy. Prior to irradiating, higher concentrations of surface microbial loading were found on the downstream side of both cooling coils under condensing conditions. Conversely, under dry surface conditions with downstream UV irradiance, surface concentrations were higher up- stream. UVG-CC (at an average 200 uW/cm2 on the coil surface) reduced surface microbial loading by 55% on average during condensing conditions and inhibited bacterial attachment causing clusters of bacterial matter to become airborne downstream of the cooling coil. Additionally, it was found that desiccation also inhibited surface microbial loading and yielded cluster detachment but to a lesser degree than UVG-CC treatment.