Mark Hernandez, PhD, PE – Professor University of Colorado at Boulder – Microbiology of the Normal and Water Damaged Buildings

Air Date: 8-5-2016| Episode: 425

We are back live with Mark Hernandez, PhD, PE this week on IAQ Radio. Our focus will be the Microbiology of the normal and water damaged built environment. Dr. Mark Hernandez received all his degrees and did a post-doctoral tenure in the Civil and Environmental Engineering Department at the University of California at Berkeley…

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We are back live with Mark Hernandez, PhD, PE this week on IAQ Radio. Our focus will be the Microbiology of the normal and water damaged built environment. Dr. Mark Hernandez received all his degrees and did a post-doctoral tenure in the Civil and Environmental Engineering Department at the University of California at Berkeley. After several years of civil engineering practice, he joined the University of Colorado faculty in 1996, where he is now a full professor. Dr. Hernandez is a registered professional engineer, and an expert on the quantitation and remediation of bioaerosols; a generation of his research lies in characterizing the biological aspects of air pollution – both indoors and out. With respect to environmental investigations, his aerobiology characterization work has focused on large scale disasters including bioaerosols generated by major metropolitan floods. Dr. Hernandez’s research group is based in an environmental microbiology laboratory, which houses the largest bioaerosol chamber in the United States, with full environmental controls. Since it’s commissioning, this laboratory has been active in aerobiology research supported by the National Science Foundation, the National Institutes of Health (CDC/NIOSH), the US EPA and various private and public companies. Dr. Hernandez was a recent recipient of a Lindbergh Foundation Environmental award and a National Science Foundation’s Early Career award for bioaerosol research.

Z-Man’s Blog:

Who is there and how many?

Dr. Mark Hernandez, PhD, PE a Professor of Environmental Engineering of the University of Colorado at Boulder was today’s guest on IAQradio.

Nuggets mined from today’s episode:

Dr. Hernandez didn’t plan on a career studying air; his academic training was in waste water process engineering where he studied the different communities of microbes found in sewage, and how they persisted in the treatment process. Sewage plants inject large quantities of air and energy into containments holding large volumes of wastewater, teeming with microorganisms.  Waste treatment workers complained to him about alleged illness and malaise, and he became interested in how waterborne microbes partitioned into aerosols and might cause associated exposures.

Wastewater workers, remediators and plumbers share this common route of occupational exposure to microorganisms which are originally waterborne.

In addition to the Deep Water Horizon Oil Spill, Mark has studied indoor and outdoor bioaerosols from at least 6 flood events throughout the US, including several events in Boulder (2013), New Orleans (post Katrina), and La Junta, Colorado. Homes studied in all of the cities showed evidence of elevated microbial and/or different microbial ecology levels following remediation. There were coarse differences between exposed and unexposed properties. No links to adverse health effects were demonstrated, or follow-up studies conducted because of funding concerns.  (Note: it’s common for Colorado homes to build out and inhabit basements).

IICRC’s classification of water damage into 3 categories is conservative. Does tap water, sitting on a previously cleaned tile floor for 72+ hours really constitute a Category 3 situation? He prefers a contextual analytical approach, rather than a discrete diagnostic approach as currently recommended by the IICRC.

Medical research methods (high throughput DNA sequencing) developed for the study of AIDS, cancers and human genome projects can now be used to help tell IEQ researchers determine what microorganisms are present in the built environment, along with direct counts. “Microscopes don’t lie”. High throughput microscopes can now perform coarse phenotypic differentiation and counts, removing subjectivity and increasing speed. It’s now possible to bring science to bear: before, during and after water intrusion events.  Microbes respond to wetted materials, all of which vary in their ability to host microbial growth: Materials vary by manufacturer; and, all drywall isn’t created equal (availability of organic carbon).

20 years ago sampling and analysis was how we determined “who is there” and “how many”; today this information available in near real time. Advocates the use of new and classical techniques side-by-side.

Praised the professionalism and skill of remediators who responded and worked on University of Colorado buildings after flooding.

The Sloan Foundation has funded 5 Microbiology of Built Environment Conferences, all of which have been held thus far in Boulder, Colorado. The dominance has shifted from microbiology to engineering and building science.  Investments in bioinformatics have been leveraged to inventory the (micro)biology of the built and help predict the potential effects microbiology can have under different conditions (RH, Temperature, operations, etc.).  Emerging methods are now available to help survey how buildings are being maintained and operated. Academics know when bad microbes are where they shouldn’t be. The final scheduled conference will be in fall 2017.

20 years ago building investigators would gather hundreds of data points, with new technology they have access to millions. The challenge is to determine, noise from signal and use the data in a thoughtful, useful way.

He evaluated the high throughput fluorescence technology currently used in the InstaScope (, and WIBS (  These product can segregate between pollen, fungi and bacteria and has been recently evaluated for use in characterizing bioaerosols in healthcare settings, side-by-side with genetic methods (see:

It’s unethical for academics to have financial interest or equity in work done for industry. Some colleagues have left academia for industry.

Is an advocate of the use of rank order distribution for comparison, how does my home compare to other similar homes in the zip code (i.e. of similar construction in a similar climate)?

Check out his recent paper on rapid bioaerosol identification using high-throughput fluorescent microscopy:

Guests’ Final Word: Feels fortunate to be part of the crossover from science to industry.

Today’s music: Growing Mold by the Radioactive Chickenheads YouTube

Z-Man signing off


Name the word defined as: the study of airborne microorganisms, pollen, spores, seeds, especially as agents of infection.