3.3.6. Biocides in the environment
Biocides may be used for a variety of applications, including water treatment, wastewater treatment or industrial use. These applications are addressed by the Biocidal Products Directive 98/8/EC, but in the absence of reporting requirements, the quantities used for these different purposes remain unknown.
Many wastewater treatment plants, especially those in coastal regions, include a final step of disinfection with chlorine. However, this practice is being questioned more and more frequently because of the toxicity of by-products for the marine fauna and the elimination of non pathogenic bacterial indicators of faecal contamination, whilst more resistantviruses and protozoa survive and may cause outbreaks for swimmers or sea-food consumers.
Cooling towers are a new place for intensive use of disinfectants since the discovery of their role in the dissemination of contaminated aerosols (Legionella sp and legionellosis). Many disinfectants are now used in order to avoid contamination of the cooling fluid; their fate is aerosolization or elimination in the wastewater.
The use of biocides as antifouling agents in building materials, on antimicrobial surfaces, and in fuels and plastic materials is also gaining in importance, but the quantities used are unknown. It is important to note that an increasing number of uses are linked with nano-size particles of disinfectants (e.g. protection of the concrete facades against lichens andmoulds) progressively released in the environment.
The development of antimicrobial surfaces using antimicrobial coating or impregnated surfaces is of great interest. Although there is an increasing number of companies developing such surfaces for a variety of industrial applications, most of these applications are aimed at the protection of the surfaces against environmental spoilage, especially against fungal micro-organisms. The use of biocides within these surfaces is for preservation of the product or the surfaces proper (e.g. caulk; wall paper, paint).
However, some surfaces will release a low concentration of a biocide and as such might contribute to a localised selective pressure. At present, surfaces that release biocides and the effect of localised selective pressure on the environmental microbial flora and on inhabitants exposed to biocide aerosols stemming from biocide impregnated surfaces has not been investigated. It is thus difficult at this stage to discern the impact of such surfaces in emerging resistance to biocides or antibiotics