Editor's note: Periodically in NewsLine, they feature a Forest Products Laboratory (FPL) researcher who has made significant contributions in their area of research. In this issue we meet Carol Clausen, Project Leader for FPL's Durability and Wood Protection research work unit since 2004. Carol received her M.S. in Bacteriology in 1983 from the University of Wisconsin—Madison. She started at FPL in 1984 as a Microbiologist, and became a Research Microbiologist in 1997. Carol's research specializes in biodeterioration and protection of wood, with an emphasis on inhibition of mold growth on wood-based building products.
Moisture in buildings has garnered a lot of attention in the press over the past few years, especially when it results in mold growth. Do you think that moisture intrusion and mold growth in buildings is more prevalent than it was in the past? If so, what do you see as the main contributing factor? Also, if a moisture problem causes mold growth, how common is it to actually be toxic? When a subject such as mold gets abundant media attention, it's really difficult to say whether mold issues are actually more prevalent now than they were in the past. Based on the number of questions I get from contractors, builders, and homeowners alike, it appears to be more prevalent. Because the source of mold growth is always excess moisture, it is important to determine the source of the moisture problem and correct it. Faulty design and improper installation and handling of building materials are some of the more common reasons for chronic moisture problems, but many other potential sources of moisture could result in mold growth. The builder or homeowner often is not equipped with the knowledge to diagnose the cause of the problem. So, education is an important aspect of my job. When we hear about toxic black mold in the news, they are referring to a mold fungus called Stachybotrys ("stack-e-botris"). Although Stachybotrys does produce toxic compounds, occurrence of this fungus is not common and is usually associated with very wet conditions, such as flooding, on cellulose products like the paper face of drywall. A more common health problem related to mold growth is an allergic response to the spores of several types of mold that can grow in 24 to 48 hours whenever excess moisture occurs without rapid drying. Some of your research focuses on mold inhibitors, or preventing the problem before it gets started. Tell us about that. Although there is no substitute for proper building and maintenance practices, my interest in developing mold inhibitors for wood products is intended to provide an added layer of protection from the types of wetting events that occur during building product storage, distribution, and inevitable construction delays. New structures have abnormally high moisture content during the period of time when the concrete foundation is curing and wet blown-cellulose insulation, drywall tape, and paint are drying. A mold inhibitor incorporated into construction materials would provide the new homeowner with added reassurance that their home is protected from mold establishment during this time. A few years ago, you developed an early detection testing kit for mold. Tell us how it works. Has there been any effort to commercialize this technology? The early detection kit is actually for decay fungi, not mold, the difference being that decay fungi cause serious structural damage to wood. The test works by causing a color change to a test cassette if a particular enzyme that the decay fungus makes is present. Because the fungus produces this enzyme very early in the decay process, the test can be used to detect decay early and stop it before it has a chance to cause irreparable damage to the wood. It can also help define an area of damage to prevent unnecessary replacement of wood that might still be structurally sound. There has been a great deal of effort to develop a prototype and commercialize this product. Hundreds of samples of the prototype test were given away at trade shows and conferences. The prototype test cassette closely resembled an early pregnancy test, so although everyone wanted a free sample to try, they wanted it clearly labeled in case they had to explain what it was to family and colleagues. Despite two licensing attempts for the patent, it has not been commercialized; but hardly a week goes by that someone doesn't call the lab asking where they can purchase this test. This is the research project that I am most proud of, and nothing would be more rewarding than to see it available in the marketplace.
Moisture isn't the only home attacker that your unit studies. Termites are a scourge to many homeowners in the southern part of the country. Wisconsin isn't exactly known to be a termite hotbed, but recently some of your team were involved with helping a small community north of Madison use a new approach to combat an infestation. Can you tell us about the infestation, what technique your scientists used to attack the colony, and why the results look so promising? The infestation in Endeavor, Wisconsin, is unique because it occurred about 100 miles north of where you might expect termites to survive the Wisconsin winter. The termites are able to survive in the underground corridor of water mains and sewer pipes in that community. First, scientists defined the size of the colony by attracting the termites to bait stations containing food. Now they are using commercial termite treatments to eradicate the colony. The success of this effort is attributed to a community-wide eradication effort instead of the usual house-by-house eradication process, where only small pockets of termites are eliminated. Community leaders initially contacted FPL because municipal buildings were infested, and FPL partnered with Alternative Pest Solutions (APS) to develop a multi-year community-wide control program. APS provides free home inspections. If termites are found and the homeowner cannot afford treatment, the village has obtained a block grant to pay for the service. The residential ban on using wood treated with copper chromated arsenate (CCA) has caused the industry to look for more environmentally preferable forms of wood protection. Can you tell us about some of the more common options on the market, how effective they are for different uses, and if there are other promising options on the horizon? Since the withdrawal of CCA-treated wood for residential use at the end of 2003, copper-based preservatives such as copper quat (known as ACQ), copper azole, and micronized copper have taken over the residential treated-wood market. They effectively protect wood from deterioration, but there are special recommendations concerning accelerated corrosion of metal fasteners when these products are used for structurally critical applications; fasteners should be hot-dipped galvanized or stainless steel. A number of promising new preservatives are on the horizon being developed both at FPL and by the industry that do not rely on copper or other metals. The next generation of metal-free preservative treatments will undoubtedly be more environmentally friendly. One final question. When treated wood comes out of service, there is an environmental concern of how to dispose of it properly. Part of your unit's work is to look at environmentally sound ways to dispose of treated wood. What techniques have shown the most promise? A number of techniques have been developed to chemically and biologically remove chromated-copper arsenate (CCA) from treated wood with varying degrees of success. My approach was to partially extract the copper, chromium, and arsenic from ground or flaked wood with an acid, followed by treatment with a bacterium that was quite tolerant of the toxic components in the preservative. Yes, this bacterium even survives in the presence of arsenic! My process removed 80% to 100% of the CCA, and I was then able to fabricate the "cleaned" flakes or particles into other products, such as particleboard or flakeboard. More recently, improvements to the acid extraction have significantly reduced the amount of time needed to extract CCA. But unfortunately, these technologies are not economically feasible as long as treated wood can readily be disposed of in landfills. In the event that landfill restrictions change, several proven technologies will be available to convert this waste into useful secondary products. For more information on these and many other topics, check out FPL's Durability and Wood Protection website at www.fpl.fs.fed.us/rwu4723/index.html or FPL's main page at www.fpl.fs.fed.us.
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