Episode 717: J. David Miller, PhD - Relative Humidity; It’s More Than Just Mold

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Episode 717: J. David Miller, PhD - Relative Humidity; It’s More Than Just Mold

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Show Resources: Show Discussion:

12:03:38 From cliff zlotnik : TRIVIA?: Name the most toxic and carcinogenic mycotoxin that has been directly correlated with causing liver cancer in multiple animal species?
12:03:39 From OVS Secretary-Shelly : Aflatoxin
12:03:54 From cliff zlotnik : which one?
12:04:33 From cliff zlotnik : Aflatoxin is an incomplete answer
12:04:47 From Don Weekes : Aflatoxin B1
12:05:09 From cliff zlotnik : correct Don, please send the contact info
12:21:56 From Don Fugler : I’m familiar with the damp basements. How about what is happening with a duct inside a drywall chase operating during cooling season? Have you evidence of this being a common high RH/mold location?
12:30:43 From Tom Martin III : As you may know, Most PCP doctors don’t ask any of the questions they are trained to prescribe big pharmaceuticals and control.

The question arises: Can the value proposition of scientific indoor monitoring surpass traditional approaches known for inflating costs and perpetuating the same outdated operations strategies that impact in-person employees, customers, clients, and taxpayers funding Medicaid and Medicare tied to conventional operations? Why or why not?
12:34:58 From Don Fugler : It is more mold in the chase I was considering
12:35:45 From Danny Gough : @Tom Martin III - I would say never gonna happen unless the stakeholders see more $$ than peddling pharmaceuticals.
12:41:17 From Tom Martin III : Replying to "@Tom Martin III - I …"
Stakeholders can’t manage what they don’t measure.
12:45:50 From Tom Martin III : Replying to "@Tom Martin III - I …"
Stakeholders should be responsible for conducting indoor air diagnostic testing in accordance with the screening data.
12:47:54 From Tom Martin III : Replying to "@Tom Martin III - I …"
Obtaining real-time air screening data is cost-effective.
12:48:02 From Don Weekes : Does the target ranges for relative humidity and water activity vary depending on the climate zone where the building is located?
12:49:27 From Don Fugler : I know that outdoor particles and indoor cooking particles can be effectively reduced by good air cleaners. I have not seen such a study targeted to particles derived from indoor-growing allergens and dust mite debris.
12:50:49 From Danny Gough : @Don Fugler - Jim Rosenthal has some info on that.
12:58:42 From Tom Martin III : During my recent visit to Disney's Contemporary Resort with my kids, the high foot traffic on the carpeted areas resulted in dry conditions, as temperatures dropped and relative humidity consistently stayed below 30%, according to my portable screening tool. The constant movement stirred up dust mites, leading to numerous people sneezing and coughing. Stakeholders are needed to address employee productivity challenges. Wearing a mask was noticeably effective in reducing the risk in such circumstances.
13:00:15 From Tom Martin III : Great show ..
13:01:43 From Don Weekes : February, 2024
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Re: Episode 717: J. David Miller, PhD - Relative Humidity; It’s More Than Just Mold

Post by CliffZ »


Show Number: 717 DRAFT BLOG
J. David Miller, PhD
Relative humidity it’s more than just Mold

Good Day and welcome to IAQ Radio+ episode 717 blog. This week we welcomed Dr. David Miller for a discussion on how relative humidity affects indoor environments. Dr. Miller advised IAQradio that he has something important to say and when Dr. Miller has something to say, people listen.

Prof. J. David Miller Dr. Miller received his secondary education at the University of New Brunswick, before studying at the University of Portsmouth in England, where he was also a NATO Science Postdoctoral Fellow. His post-university career started at Agriculture Canada, where he became head of the Fusarium mycotoxin program. He became a Professor & NSERC Research Chair in fungal toxins and allergens at Carleton University in 2000. In 2020, he was appointed as a Distinguished Research Professor. From 1999-2008, he was a visiting scientist and science advisor at Health Canada in the air health effects division. Among other tasks, Dr. Miller helped to draft the guidelines for mold and dampness published by Health Canada. Over the past several decades, he has co-managed many large studies of housing and health including in First Nations Communities.

Dr. Miller has published >350 papers on fungi and fungal toxins and has co-written 10 books on the public health aspects of exposures to fungi holds multiple patents. Miller has served on many national and international committees on mold and dampness in the built environment including on the American Academy of Allergy Asthma & Immunology committee that produced practice parameters for environmental allergens. He was chief editor of the American Industrial Hygiene Association “Green Book” (2008, 2020) and “Field Guide” (1996, 2005) that lay out guidelines for addressing mold and dampness in public buildings.

Miller is an elected member of the International Academy of Indoor Air Sciences. Among other awards, he received the AgExcellence Award from Agriculture Canada, the Toxicology Forum Scott Award for contributions to toxicology, the Applied Research Award from the Ottawa Life Sciences Council, an AIHA award for contributions to the field of industrial hygiene and the 2017 Award of Merit from the Ontario Maple Syrup Producers Association. In 2013, Miller was elected as a Fellow of the American Industrial Hygiene Association. In 2016, he received the prestigious NSERC Synergy Award for his research partnership with JD Irving, Limited. In 2021, he received the inaugural Philip R. Morey award from the ACGIH for contributions to bioaerosol guidance.

Nuggets mined from today’s episode:

Relative Humidity affects many other things besides mold. RH affects comfort; when the RH is too high or too low occupants are uncomfortable. When the gray haired IAQradio hosts and Dr Miller were young our homes were leaky.

The ASHRAE climate map stops at the 49th parallel. People live above the 49th parallel. The Köppen climate classification covers the world. Both Canada and the US have areas of absolute desert, cold polar and hot steamy humid.

A wide variety of hygrometers purchased at a hardware store which showed very inconsistent readings when deployed. Most homeowners who rely on these uncalibrated devices are receiving inaccurate information. 40%-50% RH is a comfort zone. The RH is different in the middle of the room and at windows, profound gradients exist in his photos 28% middle of room and 50% at the window.

Building materials are inconsistent, every building material adsorbs and desorbs moisture differently. The percentage of moisture by weight in a material varies dramatically, to support fungal growth wood needs to have a moisture content of 15%, mold will grow on paper faced gypsum board at only .5% moisture content.

Indoors, Stachybotrys likes high Wa and most often grows on paper gypsum board facing and cellulosic ceiling tiles.
Outdoors, Stacybotrys lives on the stems of plants near water sources.

As wet building materials dry mold growth slows down. When temperature and Wa aren’t ideal the growth of fungi such as Aspergillus amstelodomi slows down. The fungi is nether happy or unhappy.

Some substrates are more nutrient rich than others. Some “surface coatings” such as wallpaper adhesive are highly nutrient rich.

As some fungi grows, they produce hygroscopic chemicals that capture water vapor from the air. In inhospitable environments, fungi will grow slowly.

Carpet indoors is a common reservoir for fine dust. Dust is a powerful reservoir. Studies show that routine HEPA vacuuming (making 4-6 passes per square meter) is effective in removing the maximum quantity of fine dust from carpeting. HEPA vacuuming reduces exposure to what is there. Reducing fine particles reduces occupant exposure.

Dust mites were first detected in 1970. Dust mite allergen is potent and a known trigger of asthma.

Is HVAC ductwork within pipe chases prone to fungal growth? Wet metal ductwork is generally resistant to fungal growth while fibrous HVAC insulation is susceptible to fungal growth. It’s uncommon for steam or hot water heating pipes to cause fungal growth in chases or wall/ceiling cavities.

Why doesn’t Wallemi sebi show up on mold lab reports? Specialized expertise is needed to identify Wallemi sebi. Wallemi sebi is virtually unknown and unrecognized by microscopists.

Is there a norm as to when and where fungal amplification will occur within a building envelope? It depends on the design of the exterior building envelope, moisture barriers and the risks for water intrusion from either direction. Investigation will require thought, take time, and require cutting or drilling access openings into wall and ceiling cavities.

Do HEPA air cleaners really reduce airborne particulate? HEPA air cleaners are designed to remove airborne particles NOT remove fine particles trapped in reservoirs such as carpet. Intervention which removes fine airborne particles is known to benefit kids. An elegant study, “Wellbuilt for Wellbeing: Controlling RH in the workplace matters for our health.” Used personal samplers to see where exposures occurred. “We examined the association between RH and objectively measured stress responses, physical activity (PA), and sleep quality. A diverse group of office workers (n = 134) from four well-functioning federal buildings wore chest-mounted heart rate variability monitors for three consecutive days, while at the same time, RH and temperature (T) were measured in their workplaces. Those who spent the majority of their time at the office in conditions of 30%-60% RH experienced 25% less stress at the office than those who spent the majority of their time in drier conditions. Further, a correlational study of our stress response suggests optimal values for RH may exist within an even narrower range around 45%. Finally, we found an indirect effect of objectively measured poorer sleep quality, mediated by stress responses, for those outside this range.”

Endotoxin exposure? Outdoor air, tracking outdoor soil, and pets are three common ways that endotoxins from outdoors get indoors. In the past, humidifiers would be reservoirs for endotoxins. Old style humidifiers are heaven for mold and bacteria.

Dr. Miller’s Final Comments:
• In north America, outdoor air pollution has continuously dropped since 1978.
• 2024
• It’s more than mold
• The new ACGIH BioAerosols Assessment and Control book will be released in 2024.

Z-Man Signing Off

TRIVIA- Name the most toxic and carcinogenic mycotoxin that has been directly correlated with causing liver cancer in multiple animal species?
Answer: Aflatoxin B1
Answered by: Don Weekes, 1075 Borden Side Road, Ottawa, Ontario, Canada K2C 3P3
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Re: Episode 717: J. David Miller, PhD - Relative Humidity; It’s More Than Just Mold

Post by RadioJoe »

We always love having Dr. Miller join us. This week was no exception. I probably should have asked somebody about Wallemia long ago but finally asked Dr. Miller. I keep hearing from researchers how common the organism is in indoor environments but never see it in lab reports, etc. Why? It seems that it's not easily identified by microscopists and probably more importantly does not release full spores but more often spore fragments. Any other IEQ Consultants out there ever wonder about this or do you see this organism in your lab reports?
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