Our show with Stephanie Taylor, MD has been moved back to July 31st. This week we will play a Flashback Friday show with Rachel Adams, PhD called Moisture Measurement and Mold. At a minimum we encourage you to check out the Z-mans Blog from this important show.
Moisture measurement and mold
Rachel Adams, PhD recollects always being interested in nature and biodiversity. With a purely research background, she studies the hidden diversity of tiny things. She works as a Project Scientist at University California, Berkeley and as a microbiologist with the California Dept. of Public Health (CDPH). She doesn’t work in infection or regulation she researches the microbial causes of indoor air pollution.
Nuggets mined from today’s episode:
In California dampness and mold make homes and apartments substandard. The CDPH’s Indoor Air Quality Program has published statements discussing mold and what to do about it. A database has been created identifying who can help when Californians in rental homes have mold. There are variations between how effectively the different agencies provide mold assistance. Local jurisdictions can cite or deem housing as uninhabitable. Landlords then must make repairs.
A 2014 metanalysis shows that moisture and mold exacerbate asthma. Kanchongkittiphon, W., Mendell, M. J., Gaffin, J. M., Wang, G., &Phipatanakul, W. (2014). Indoor environmental exposures and exacerbation of asthma: an update to the 2000 review by the Institute of Medicine. Environmental health perspectives, 123(1), 6-20.
Relying upon multiple reports, papers and questionnaire/survey it is estimated that 20%-50% of US homes have one or more signs of dampness.
“Water activity (aw) is defined as the ratio of the partial pressure of water in the atmosphere in equilibrium with the substrate (e.g. a food) to that of the atmosphere in equilibrium with pure water at the same temperature, and is expressed on a scale of 0 to 1 where 1 is for pure water.” From: Chilled Foods (Third Edition), 2008
Janet Macher first started to look at how moisture meter readings relate to water activity, and therefore risk of growth. Dr. Adams and others were recently part of a follow up study that would get at the feasibility of knowing: for this meter, this surface, and this moisture meter reading, what water activity does that represent? When drywall samples were placed into a sealed chamber and moisture introduced, the researchers left the samples for a week to equilibrate. A water activity meter that measured RH of a sealed head space took one day to equilibrate.
Meter readings are not directly related to the likelihood of that surface growing microorganisms.
Both pin and pinless moisture meters measure moisture content of materials not the RH at the surface.
Any fungal growth in homes=a health risk. The greater the size of visible growth, the greater the risk.
Moisture hysteresis refers to the sorption and desorption of moisture in materials: moisture is taken-up at a faster rate than it is released.
Honey and jam are both resistant to spoilage because the moisture contained within both products is chemically bound.
There is room for innovation in estimating/measuring aw in buildings.
Microbiome is a collection of microbes in a habitat. Looking for the signal within the noise. Using bioassay to predict human health and building outcome.
Preview of an editorial written with Mark Mendell titled “The challenge for microbial measurements in buildings” is that quantified microbial measurements currently lag behind building inspection.
- She will be studying MVOCs at various moisture content levels.
- When home code enforcers see mold, they need to think moisture and ensure problems are fixed.
Z-Man signing off
Name the scientist who is 1953 established bacterial growth correlated to water activity not water content.
Answered by Doug Kohnen