Testing Antimicrobial Paint Efficacy on Gypsum Wallboard Contaminated with Stachybotrys chartarum

Abstract

The goal of this research was to reduce occupant exposure to indoor mold through the efficacy testing of antimicrobial paints. An accepted method for handling Stachybotrys chartarum-contaminated gypsum wallboard (GWB) is removal and replacement. This practice is also recommended for water-damaged or mold-contaminated GWB but is not always followed completely. The efficacy of antimicrobial paints to eliminate or control mold regrowth on surfaces can be tested easily on nonporous surfaces. The testing of antimicrobial efficacy on porous surfaces found in the indoor environment, such as gypsum wallboard, can be more complicated and prone to incorrect conclusions regarding residual organisms. The mold S. chartarum has been studied for toxin production and its occurrence in water-damaged buildings. Research to control its growth using seven different antimicrobial paints and two commonly used paints on contaminated, common gypsum wallboard was performed in laboratory testing at high relative humidity. The results indicate differences in antimicrobial efficacy for the period of testing, and that proper cleaning and resurfacing of GWB with an antimicrobial paint can be an option in those unique circumstances when removal may not be possible.

Antimicrobial treatment and efficacy

“…low-velocity air fl ow against gypsum wallboard with room wall simulators (Foarde et al, 1997a(Foarde et al, , 1997b(Foarde et al, , 1997cMenetrez and Foarde, 2002;Menetrez et al, 2004Menetrez et al, , 2007Menetrez et al, , 2008aShechmeister, 1991;VanOsdell et al, 1996). The DMTC allows for a variety of microbiological research to be performed involving biological growth on building materials, evaluation of emission and deposition of bioaerosols, the impact of HVAC mechanical system components on biological contaminants, and in-duct tests of air cleaners.…”

“…The results indicate differences in antimicrobial efficacy for the period of testing (ASTM 6329-98, 2003;Menetrez et al, 2007Menetrez et al, , 2008aMenetrez and Foarde, 2002;VanOsdell et al, 1996). An encapsulant or coating is a covering that is applied (spray paint as in Fig.…”

“…The most effective coatings were Coatings I and III while Coating II was ineffective. Although all three antimicrobials are registered with the EPA, they were not equally effective, nor should they be expected to perform equally in fi eld use (Menetrez et al, 2004(Menetrez et al, , 2007(Menetrez et al, , 2008aMenetrez and Foarde, 2002).…”

“…Additionally, the series of experiments described in Menetrez and Foarde (2002), are adequate tests for viable mold (ASTM 6329-98, 2003;Menetrez et al, 2004Menetrez et al, , 2007Menetrez et al, , 2008aMenetrez and Foarde, 2002;VanOsdell et al, 1996). However, in addition to viable mold antimicrobial effi cacy, additional testing may be needed for viable bacteria (bacteria cells and spores), nonviable mold (mycotoxins) and bacteria (endotoxins), as well as viruses and some forms of allergens (e.g., dust mites), to determine whether the manufacturers' claims apply (Foarde et al, 1997a(Foarde et al, , 1997b(Foarde et al, , 1997cMenetrez and Foarde, 2002;Menetrez et al, 2007Menetrez et al, , 2008a. The results demonstrated a signifi cant variation in the antimicrobial effi cacy of encapsulants.…”

“…Research to control S. chartarum growth using seven separate antimicrobial paints and two commonly used paints on contaminated gypsum wallboard has been performed in laboratory testing. The nine paint products and manufacturers tested are listed in Tables 13.7 and 13.8 along with the product active ingredients (Menetrez et al, 2008a).…”