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Clemson University Department of Biological Sciences and Tile Council of North America Product Performance Testing Laboratory evaluated whether ceramic tile and Plastic Based Material (PBM1) flooring support mold growth when exposed to fungal spores.

Mold grows in moisture-rich environments and requires only minimal sources of nutrition to support growth. It has long been identified to cause damage to buildings and construction materials and its presence in buildings has been connected to many major health concerns with various studies and reviews published on this matter.2

The method used to evaluate mold growth was ASTM G21-96 (2015).3 This test method is robust and is performed with minimal salts media and no nutrients. The test fungi have to utilize any carbon sources present in test specimens to support their growth. As the test setup provides no nutrients for the mold to grow, any growth is attributed to nutrients in the test specimen that support mold growth.

Testing was conducted on 25 PBM products that manufacturers4 advertise or claim to be waterproof, water resistant, or depict being used in areas where flooring gets wet.5 For 22 out of 25 products (88%), the manufacturers also disclaimed damage from mold or excessive moisture in the product warranties.6 The results of this study, including a total of three repetitions of all testing, show that 100% of the PBM products tested supported mold growth. The growth of fungi was observed on all surfaces on some PBM products and only on certain surfaces (top, bottom, or sides) on others. Such mold growth can release spores, mycotoxins, microbiological volatile organic compounds (MVOC’s) and other environmental toxicants to contaminate indoor air through a variety of mechanisms as detailed in Section 3.2. The ceramic tile tested did not support mold growth.

Given the possibility of material degradation and potentially serious health consequences from mold growth as detailed in Section 3.2, and the likelihood of damp and favorable conditions for mold growth as detailed in Section 3.3, a dry use-only caution, and/or warning regarding potential for mold growth, should be considered for products that perform similarly to those tested for this report. This is especially relevant given the exclusion for mold damage in many of the products’ warranties.