Carpets are both sinks and sources for exposure to chemicals, allergens, and microbes and consequently influence health, including asthma, allergies, and infectious diseases. Asthmatics, children, and the immune-compromised are particularly vulnerable to health risks resulting from exposure to carpet contaminants. To address this risk, a commercial upright vacuum cleaner with an ultraviolet germicidal lamp (λ=253.7 nm, UVC) has been developed for residential and commercial uses. However, its effectiveness in reducing microbial load on real-world carpets has not been previously demonstrated.
Accordingly, the purpose of the current study was to evaluate the effectiveness of a UVC-equipped vacuum in reducing the carpet surface-bound microbial load. This was accomplished by comparing the carpet microbial surface load from pre- to post-treatment of 9 ft2 in-use carpet sections under three treatment scenarios: 1) UVC alone (UV), 2) the beater-bar plus vacuum (BB+Vac), or 3) a combination of all three (COMB). Each treatment was two minutes in duration. Microbial surface loads were measured by pressing contact plates containing Sabourauds Dextrose agar onto the carpet surface. In-use carpets from three locations were tested in place. The treatment effect was evaluated at two levels. First, we considered the mean reduction in CFU from pre- to post-treatment for each 9 ft2 carpet grid (n = 4 for each treatment). The second level considered each 1 ft2 section using a paired analysis (n = 40 to 49 for each treatment). A total of 125 pre/post-sample pairs were collected across the three treatments. Results showed that all three treatments were associated with a reduction in carpet microbial load (p < 0.0001). The COMB yielded the largest reduction of 13 CFU/plate (87% reduction) and was approximately the sum of the individual effects of either UVC (6.6 CFU/plate, 60% reduction, p = 0.009) or BB+Vac (7.3 CFU/plate, 78% reduction, p < 0.0001). We therefore conclude that a UVC-equipped vacuum approximately doubles the unit’s effectiveness in reducing surface-bound microbial load, thereby holding promise as a means for decreasing indoor infectious disease risk.
Eric A. Lutz†, Smita Sharma†, Bruce Casto†, Glen Needham‡, and Timothy J. Buckley*†
Division of Environmental Health Sciences, College of Public Health, The Ohio State University, Columbus, Ohio 43210, United States, and Department of Entomology, College of Biological, Mathematics, and Physical Sciences, College of Food, Agricultural and Environmental Sciences, The Ohio State University, Columbus, Ohio 43210, United States
Environ. Sci. Technol.
Publication Date (Web): October 29, 2010
Copyright © 2010 American Chemical Society
* Corresponding author phone: (614)293-7161; e-mail: [email protected],
† Division of Environmental Health Sciences, College of Public Health
‡ Department of Entomology, College of Biological, Mathematics, and Physical Sciences, College of Food, Agricultural and Environmental Sciences.