What's Missing With Mold Remediation Guidelines
(Sampling for Small Particles in the Air)
Consultants from industrial hygienists (CIHs) to professional engineers (PE) will cite some form remediation from publicly available guidelines or standards (EPA, New York City, ACGIH, IICRC). These documents don’t diverge too far from each other – especially since some of the committee members served with more than one organization. In fact, the EPA’s mold remediation guidance started as an amalgamation or the guidelines from New York City and the ACGIH. The IICRC S520 has some good information missing from the prior 3 mentioned but, still falls short due to ambiguity.
Another trend is to have the remediation contractor write the remediation plan. It is argued by Mike McGuiness in the AHIA Green Book (Recognition, Evaluation & Control of Indoor Mold) contractors may know more about equipment, manpower and construction. This means they are responsible for the “means and methods” to get the job done. This is a phrase common to contracts for construction – especially renovation. This is how consultants limit their liability greatly just like architects. This is also were the problems explode. Opinions about remediation methods change when you change your focus or increase your level of detection.
Size matters more than you may think. Your ruler won’t help you understand. You have to consider the limitations of what can be seen with a light microscope versus an electron microscope. Consider a common occurrence after remediation. People complain more after remediation that before remediation. This was announced at an ACGIH symposium for mold remediation almost a decade ago. Carol Rao, PhD Toxicologist with CDC NIOSH, described the contradictory data from a CDC NIOSH study at a hospital where pulmonary function was tested for hospital personnel and sampling of the moldy environment. Remediation followed ACGIH recommendations in their book, Bioaerosols: Assessment & Control. Environmental test results were good but pulmonary test results were worse after remediation. Their main environmental sampling was air samples for culturing and spore traps.
At the time of the CDC NIOSH study, polymerase chain reaction or PCR was new to the industry. Environmental Relative Moldiness Index or ERMI did not exist at the time either. ERMI is a statistical score applied to PCR testing from a common carpet cassette previously used for allergen testing. This is the only commercially available to test for small fragments of mold. Other methods rely on whole spores or conidia while have extremely limited information for species level or ability to reproduce in culture for species identification.
Rafal Gorney had not published his findings about the presence of 320 particles for every spore or conidia in the air (Fungal Fragments as Indoor Air Biocontaminants – 2002: Applied Environmental Microbiology). Trevor Brasel had not published his findings showing small particles of Stachybotrys contained mycotoxins (Detection of Airborne Stachybotrys chartarum Macrocyclic Trichothecene Mycotoxins on Particulates Smaller than Conidia - 2005: Applied Environmental Microbiology).
Here we are a decade later and nothing has changed in the industry. The industry still largely follows asbestos abatement techniques because it is human nature to resist change. The industry still relies on the spore trap air sample as the test of choice to test for invisible mold or perform post remediation verification after mold remediation. I have a case where 3 different firms have done mold remediation by the classic methods and the property owner is still having symptoms that lead to having mold remediation done. This is unacceptable.
Air samples are very questionable if pay attention to scientific literature. Depending on the source (ACGIH, AIHA, Bob Brandys), you need to take anywhere from 3 to 9 samples per room for any statistical certainty since particles do not mix in the air like gasses and vapors. You will easily spend more money on lab fees for the correct number of spore trap air samples than it costs for a single ERMI test. The cost will explode if you want to use culturable air samples that can be identified to species level and take 2 weeks or more for analysis.
A recent session by William Turner at the Bioaerosols Conference in 2012 suggested taking spore trap air samples without stirring the air was questionable. William Turner has been a scientific contributor to the EPA for various publications dating from the Building Air Quality Guide in 1995 to present documents published by the Office of Indoor Air at the US EPA. If an old dog can learn new tricks, why do we still have this problem? I apologize to William Turner for referring to him as an “old dog”. The difference is the “old dog” in this sense is a scientist and others are merely playing the role of a pump jockey. William Turner and his colleagues observed mold growth in a room and took spore trap air samples in the traditional manner without stirring the air or “quiescent”. They changed one parameter and stirred the air for “aggressive” sampling and found much better characterization of the problem.
This still does not address microbial particles smaller than a mold spore or conidia. In aerosol physics, particles behave differently depending on size, density and shape. Mold spores or conidia are more subject to gravity than diffusion – especially with higher humidity and/or cooler air. Diffusion means particles float in the air rather than drop with gravity. Smaller microbial particles will stay airborne longer since they become smaller and lighter. Smaller microbial particles dry faster and re-aerosolize.
Smaller particle penetrate the body deeper if you look at nanotoxicology. It is more likely to inhale particles smaller than mold conidia such as various species of Aspergillus which generally range from 2 to 5 micrometers. Microbial particles go into Brownian motion starting at 0.5 micrometers and smaller. This means they start vibrating in the air like gas and water vapor molecules. You can’t see particles smaller than 0.3 micrometers a light microscope used to analyze spore traps or culturable samples. Particles smaller than 0.2 micrometers can penetrate the gap between the olfactory bulb at the top of your sinus cavity and next to your brain. Influenza virus is generally 0.1 micrometer. Nanoparticles are measured as 0.1 micrometer or smaller. 100 nanometers equals 0.1 micrometers. Nanoparticles are thought to be more active since you have increased surface area in ratio to volume.
Depending on shape and air speed, the microbial particles may travel different paths rather than straight lines. This is called “curvilinear motion” in physics. Air speed is also important. Airplanes or gliders can only fly in a certain range of air speeds. Particles are no different since they are subject to the same rules of physics on a smaller scale. This is why William Turner proposed stirring the air when taking air samples.
Recently, I used a patented air cleaning method based on fogging to address if mycotoxins within particles could be present in the air for possible inhalation exposure. The residence had been completely stripped to the frame inside and outside on the north. Attempts at remediation were also done more than one year prior. The only movement was removal of contents before pretesting and the second remediation. I had plastic lined on the floors. I captured the particles using this patented fogging method and a product I developed for this patent for no odor or chemical sensitivity complaints. The particles settled on the plastic. The plastic was shipped to the lab to be processed in a grain mill with solvent added and the sample split into 2 samples or split samples. The analytical chemistry methods were HPLC-TLC and LC MS/MS. The latter chemistry method is considered definitive or the gold standard. Both samples yielded approximately 6 nanograms of ochratoxin A. I can’t tell you if the mycotoxins were concentrated in 1 area of evenly distributed throughout the 3,000 square foot residence. I can tell you the people were very sick and the usual air sampling methods were not very useful. I will be repeating this at other sites for an eventual study. This just makes you realize we know less than we think we know.
Greg Weatherman is a Certified Microbial Consultant with Aerobiological Solutions, Inc. He has 15 years of experience for consulting and contracting with microbial problems. He also wrote a chapter concerning testing and remediation of mold in Surviving Mold. He holds patent #7,951,227 for cleaning particles from the air. He has more than a decade of experience with Dr. Ritchie Shoemaker’s patients.