Deleterious effect plastic-based biocides on back-ventilated granite facades B. Prieto, P. Sanmartín * , 1 , C. Silva, D. Vázquez-Nion, B. Silva Departamento Edafología y Química Agrícola, Facultad Farmacia, Universidad de Santiago de Compostela, Santiago de Compostela, 15782 A Coruña, Spain article info Article history: Received 31 January 2013 Received in revised form 3 June 2013 Accepted 3 June 2013 Available online xxx Keywords: Back-ventilated facade Algae and cyanobacteria Biocide Bioreceptivity Colour measurements Fouling tests abstract In Galicia (northwest Spain), the mild humid climate causes the walls of many buildings to be perma- nently damp, which leads to the appearance of phototrophic colonization (“greening”) on the walls. Prolonged, deeply penetrating damp can be halted by the application of plastic-based products. Venti- lated facades are separated from the structural wall, which enables the protective products to be applied to the back of the facade. This is an important advantage since it allows the use of coloured paints, which would be unacceptable for use on the exterior face of a building, and other plastic-based compounds that are degraded by solar radiation. The main aim of this laboratory-based study was to evaluate the use- fulness of several plastic-based products (viz. white plastic paint, Sikaflex Ò , Tegosivin Ò , and Tegovakon Ò ) for inhibiting biological colonization on the exterior faces of buildings when applied to the back of the stone cladding. The results of the study demonstrated an unexpected effect: the application of plastic- based products to the back of specimens simulating ventilated granite facades does not inhibit biolog- ical colonization, but increases the tertiary bioreceptivity of granitic rocks. Ó 2013 Elsevier Ltd. All rights reserved. 1. Introduction Cleaning is an important aspect of the maintenance and reha- bilitation of stone buildings and structures. Colonizing microor- ganisms contribute substantially to the fouling of buildings, which causes aesthetic as well as physical and chemical damage to the building materials (Seaward, 1979; Grant, 1982). In Galicia (NW Spain), the climate is oceanic, and the atmospheric humidity is high because of the high rainfall and the mild temperatures that occur throughout the year. This leads to many building surfaces being permanently damp, which favours biological colonization, the development of biofilms and thus the formation of greenish patches, in a phenomenon commonly referred to as “greening” (Fig. 1). Previous studies (Gaylarde et al., 2004; Barberousse et al., 2006a,b) have shown that green microalgae and cyanobacteria are the main constituents of “greening” on building facades. The growth and development of these microorganisms, and the sub- sequent recruitment of other microorganisms, cause aesthetic damage to buildings and favour deterioration of the underlying material (Ortega-Calvo et al., 1991; Tiano, 1993; Saiz-Jimenez, 1994; Tomaselli et al., 2000; Crispim et al., 2003; Sterflinger, 2010). In order to arrest the impact of green biofilms, water availability, which is the main environmental factor that limits growth of mi- croorganisms (Bellinzoni et al., 2003), and the bioreceptivity of the material, i.e., its aptitude to be colonized by living organisms (Guillite, 1995), must be decreased. Different chemical products that act as water repellents and decrease the bioreceptivity of building facades are widely available nowadays. However, these products require preliminary testing in the laboratory with isolated strains of microorganisms, to determine their compatibility and effectiveness on the materials in question (e.g., Krumbein, 1993; Young et al., 1995; Urzì and De Leo, 2007; De Muynck et al., 2009; Fonseca et al., 2010). This information is essential for researching new methods capable of preventing the process of biodeterioration in buildings. The use of some commercially available plastic-based products in outdoor environments is increasingly discouraged because of the potential ecotoxicity of such products and the fact that they do not promote long term protection, mainly because they are washed off the surfaces of buildings by rain and therefore need to be repeatedly applied (Russell and Chopra, 1996; Fonseca et al., 2010). However, the * Corresponding author. Departamento de Edafología y Química Agrícola, Facul- tad de Farmacia, Campus Vida, Universidad de Santiago de Compostela, Santiago de Compostela, 15782 A CORUÑA, Spain. Tel.: þ34 881 814920; fax: þ34 881 815106. E-mail address: patricia.sanmartin@usc.es (P. Sanmartín). URL: http://www.usc.es 1 Current address: Laboratory of Applied Microbiology, Harvard School of Engi- neering and Applied Sciences (SEAS), Harvard, 29 Oxford Street. Cambridge, MA 02138, USA. Contents lists available at SciVerse ScienceDirect International Biodeterioration & Biodegradation journal homepage: www.elsevier.com/locate/ibiod 0964-8305/$ e see front matter Ó 2013 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.ibiod.2013.06.018 International Biodeterioration & Biodegradation xxx (2013) 1e6 Please cite this article in press as: Prieto, B., et al., Deleterious effect plastic-based biocides on back-ventilated granite facades, International Biodeterioration & Biodegradation (2013), http://dx.doi.org/10.1016/j.ibiod.2013.06.018