Indoor air biocontaminants—like fungi, bacteria, dust mites, viruses, and protozoa—can grow and persist on a variety of building materials and indoor surfaces. Once the biocontaminants become airborne, exposure can cause or worsen allergic or infectious conditions. It can also cause headache, nausea, dizziness, and other symptoms.
One such biocontaminant is black mold (genus Stachybotrys), which can grow on common building materials such as fiberboard and gypsum that has sustained water damage or been exposed to excessive humidity. As the link between black mold and health symptoms becomes clearer, the scientific and health communities must develop a deeper understanding of this organism and approaches to inhibiting its growth.
To prevent the growth and spread of black mold and other molds, manufacturers have incorporated antimicrobial agents into their building products. At the same time, consumers’ desire for sustainable building products has influenced manufacturers to incorporate green, or eco-friendly elements, into their building materials.
For example, several readily available gypsum products—a material commonly used in walls and ceilings—that incorporate recycled components claim to reduce mold growth indoors. However, there is no nationally accepted testing and verification program to guide consumers and building professionals on how to select or specify the best gypsum products for their needs.
In 2010 as part of our work under the U.S. Environmental Protection Agency’s Scientific Technical Research Engineering and Modeling Support (STREAMS) program, we designed and performed research studies to help address this gap. These studies sought to
- Identify an accurate and repeatable testing method for validating antimicrobial resistance
- Determine which building materials were the least likely to allow biocontaminant growth using the testing method identified
- Characterize black mold using quantitative polymerase chain reaction (qPCR) and next-generation sequencing
- Determine the biological effects on humans induced as a result of exposure to black mold grown on green building materials.
Developing a Test Method to Assess Microbial Resistance in Gypsum
Our microbiologists identified and evaluated five current standard methods identified by the American Society for Testing and Materials (ASTM) for testing the microbial resistance of gypsum products. We also developed and tested our own method. Only the RTI method both provided quantitative results and allowed adequate flexibility—by not specifying the test organisms to be used—to meet the client’s research need.
Using our unique method, we were able to characterize fungal contaminants on gypsum wallboard materials. We utilized a method known as reverse transcription Polymerase Chain Reaction to target the gene that regulates production of toxic substances produced by the fungus. By monitoring the regulation of this gene, we were able to determine whether the fungi produce toxins with the potential to significantly impact indoor air quality and thus occupant health.
Better Information Leading to Better Building Materials
Because negative health effects have been traced to black mold, genomic sequence data about the fungus have significant potential to inform additional research into toxin and allergen production or fungal metabolism.
Using our high-throughput sequencing technology, the genome of one strain of black mold was sequenced using next-generation sequencing technologies.
Additionally, we assessed the toxicity of black mold growth on eco-friendly wallboard material using cell culture methods to measure cell death, inflammation, adaptive immune activation, and other biological effects. Results from this study showed differences in macrophage response across fungal species and wallboard material used for growth. In general, our studies indicated that the materials did inhibit fungal growth as evidenced by adverse macrophage responses such as cytotoxicity and high levels of inflammation.
Ultimately, results from these studies contribute to a greater understanding of how to prevent fungal growth in building materials, helping developers and manufacturers and leading to safer, healthier buildings.