BIOCIDES Under Pressure
Biocides are indeed facing a difficult situation. On the one hand, they are needed more than ever because waterborne coating systems offer microorganisms everything they could wish for. If they are not controlled, they can cause considerable damage in the can, in the coatings production process or in the coated product after application. However, under the new European Biocidal Products Directive (BPD), the use of biocides is strictly regulated. Several speakers at the ECC "Novel Biocide Technology" in Berlin addressed the implications of the BPD. John Duddridge, Rohm and Haas, a renowned expert on this topic, delivered the opening presentation at the conference. Duddridge explained the definitions, procedures and relevant time frames of the BPD and other relevant directives, and also discussed the data requirements necessary for the product notification.
The BPD evaluates biocidal products based on risk assessments rather than hazard assessments. Hazard corresponds to toxicology data in terms of effect/dose, but risk includes both hazard and exposure, i.e., an analysis of the time-dependent concentrations of the substances in the environment. To collect corresponding data is time-consuming and expensive - Duddridge calculated that the registration of a new biocidal substance under the BPD will cost the applicant approximately 5-8 million Euros. In the United States and other industrialized countries, similar regulations exist, with similar costs. Thus, the BPD is not a competitive disadvantage.
A True DilemmaStill, the directive and its implications make the development of biocide systems very difficult, and the industry is facing a true dilemma. New active substances cause high costs. An obvious solution would be to find new uses and to maximize the effects of known, notified products. Meanwhile, biocide blends are offered by all major producers, and efforts are being made to develop them further. The buzzword here is "synergy" - the efficacy of a blend of several actives can be higher than the sum effects of the single substances. But unfortunately this can also be a problem.
Synergistic effects may also occur in the toxicology and ecotoxicology of the blends. In that case, they would be more toxic than the sum of their ingredients. The authorities are well aware of this problem, and in such cases extended studies are imposed to prove that synergistic toxicology effects are excluded, again causing high costs. In his presentation, Blaise Henry, Dow Chemical, made sure that the audience remembered this point - his half-joking solution: "Don't use the word 'synergy', use 'potentiation' instead."
New Uses For Old SubstancesDespite the cost dilemma, the compulsion towards innovative biocide systems remains. The first day of the ECC "Novel Biocide Technology" mainly addressed new ideas for the use of old active biocides. David Roper, BASF Biocides, presented BIT/Bronopol blends as well as a new KHDO-variant (potassium N-cyclohexyldiazeniumdioxide), which predominantly excel as strong fungicides. Scott Betts, Thor Specialties, reported on MIT/BIT combinations (isothiazolones), which show a much lower tendency for bacterial tolerance compared to CIT, based on their different mechanism of action. Blaise Henry discussed studies on DBNPA, a "quick-kill" biocide that has been known for a long time, but which has not been used in coatings formulations yet. He pointed out that it can be used as an effective disinfectant, which is also environmentally friendly, because it decomposes rapidly after unfolding its effects. Kornelia Treskonova, ISP International Specialty Products, concentrated on novel combinations of formaldehyde releasers (IPBC/CTL), also featuring an improved efficacy. Addressing a similar topic, Holger Zitt, Bode Chemie, featured new blends of isothiazolones (CMI, MI) with formaldehyde releasers (TMAD), showing both good efficacy and a very low smell, which is not typical for formaldehyde-release biocides and also makes them VOC-compliant.
Bacterial Resistance to Biocides is UnlikelyAlex Cornish, Avecia Biocides, reported on studies that closely examined cases of alleged resistance of micro organisms against common biocides (BIT, MIT, CMIT and combinations thereof) - another hot topic, which is often transferred to biocides from the public debate on the use of antibiotics. Will the use of biocides (particularly upon prolonged under-dosage) bring about more dangerous, mutant bacteria, which possibly will also be resistant to antibiotics? This might of course be a severe health problem, but it would also force the development of new active substances. But Cornish was able to show that such resistances of bacteria against biocides is far less likely than against antibiotics, because biocides generally attack a multitude of targets within the bacterial cell, and because their mechanism of action usually "brutally" affects the cell's physiology. Mutations leading to resistance are thus hardly imaginable, and more important, the studies demonstrate that upon critical examination almost all spoilage incidents could be attributed to other causes than mutagenic bacterial tolerances.
Cell Analysis in Real-TimePatrick Schwarzentruber, Omya, addressed the analytical problem: Using standard incubator/plate-counting methods, the analysis of cell concentrations in liquid systems is very time-consuming. Test results often require 23 days. Schwarzentruber presented a technique that simultaneously measures the electrical impedance and fluorescence of the liquid, while passing a thin tube. Using appropriate coloring of the bacteria allows us to count and to analyze the cells within seconds. In addition, the coloring also allows monitoring the physiological status of the cells (active/inactive/dead). Pigmented coating systems can also be analyzed, in this case the solid content has to be separated off by centrifugation first.
Antimicrobial PolymersThe second day of the conference focused on new biocidal substances. The first three lectures presented polymeric active substances, which have the advantage of being fixed within the coating matrix and of not being consumed in use. Kim Lewis, Northeastern University Boston, featured a polymer system based on poly(4-vinyl-N-alkylpyridinium bromide) and polyethylenimine. The polymers are fixed on the surface, and the active group penetrates the target cells and kills them while still being chained to the surface via the polymer. The result is an actively sterilizing surface. Detlef Thalmann, Degussa, discussed a slightly different concept. Polymers with aminofunctional groups on their surface are incorporated in the coating and show a permanent, effective antimicrobial activity without releasing any agents in the environment. Andreas Holl?nder, Fraunhofer Institute for Applied Polymer Research, IAP, had a similar solution, and described the antimicrobial efficacy of polyammonium compounds that are chemically coupled to various polymers (plastics), forming a mere nanometer-thin layer. These coatings are highly efficient, require only very little material and are chemically stable. Due to their extremely low thickness, however, they are of course somewhat prone to damage by scratching.
Reloadable Biocidal Coatings
A different concept was put forward by Jeff Williams, Vanson Halosource - n-Halamine-based coatings act biocidal through active halogens. The halogen concentration released by the coatings is such that it effectively kills off bacteria, but is not odorous. Hydantoinyl-compounds are polymerized into a polyurethane matrix. The coating can then be loaded with chlorine simply by rinsing with a sodium hypochlorite solution. The coatings excel with a very high and long-term efficacy, which can just as easily be regenerated by another loading step.
Powders and Inorganic BiocidesHarry Brodie and Steven Green, Biocote, demonstrated the possibility to formulate biocidal powder coatings. They managed to incorporate both organic and inorganic biocides in their formulation, which survive the challenging conditions during powder coating production and still unfold a high biocidal efficacy.
Two presentations dealt with purely inorganic biocides: J”rg Hocken, Sachtleben Chemie, focused on the use of nanoparticles of TiO2 and ZnS. These particles are photocatalytically active. Upon irradiation, hydroxyl radicals are formed in the case of TiO2, and traces of dissolved zinc in the case of ZnS; both with a high biocidal efficacy. The nanoparticles can be used to generate easy-to-clean surfaces at the same time, effectively preventing the formation of biofilm, which generally, once formed, is extremely difficult to remove and often presents a real nuisance, particularly within production vessels.
Christian Goebbert, ItN Nanovation, reported on silver-coated TiO2 nanoparticles, which are incorporated and fixed in the coating matrix and again show a high antimicrobial efficacy over years.
However highly innovative the new polymeric and inorganic biocides may be, they too fall within the scope of the European Biocidal Products Directive and thus cannot avoid the regulative costs either.
ConclusionDespite many innovations, it will become more difficult for both producers and users of biocides to find the perfect system, and more importantly, at the same time. The chairman of the first conference day, Jeff Williams perhaps asked the crucial question, "Has anyone ever calculated the cost of NOT using biocides?"
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World Biocides Demand To Increase 5.6% Annually Through 2006World demand for biocides is projected to increase 5.6 percent per year to $5.9 billion in 2006. North America and Western Europe will remain the largest regional markets, accounting for about two-thirds of overall demand. Due mainly to continued double-digit growth in China, the Asia/Pacific region is expected to register the fastest growth through this decade, and will be the second largest regional market by decade's end. Latin America is also expected to register above-average growth, but will still account for less than five percent of world demand. These and other trends are presented in World Biocides, a new study from The Freedonia Group, Inc., a Cleveland-based industrial market research firm.
Regulatory considerations will continue to have a profound effect on the biocides industry, most notably in the United States, Canada and Western Europe. The United States Environmental Protection Agency's (EPA) product-registration process is costly and time-consuming. The Canadian process is comparable to that in the United States. In fact, Health Canada collaborates with the U.S. EPA on many biocides-related matters. In the European Union, a decade-long reshaping of the biocides market is underway, following the implementation of its Biocidal Products Directive in the year 2000. A large share, perhaps well over one-half, of currently approved active ingredients are not expected to survive the reconsideration process. In other parts of the world, the stringency of environmental regulations varies widely, but the general trend of increasingly rigid environmental standards is expected to continue, although not uniformly so.
The paper and coatings markets for biocides are expected to register the strongest growth among the major end-use applications. A number of factors in the pulp and paper market will help to boost biocides demand. Production of both pulp and paper is expected to register accelerating growth following a somewhat sluggish period, especially in North America, which is a major pulp and paper producing region.
Additionally, recycled fibers, the use of which generally requires greater biocide usage, will continue to increase their share of the paper fiber market, albeit somewhat less dramatically than in the past decade or so. Similarly, demand for biocides used in paints and coatings will increase as a result of faster growth in global coatings production. Also, there will be a continuation of the trend toward greater use of waterborne coatings formulations, which are usually more susceptible to microbial attack. This transformation within the coatings market is essentially complete in the U.S. and Western Europe, but is still well underway in many other parts of the world.
World Biocides (published 02/2003, 356 pages) is available from The Freedonia Group, Inc., 767 Beta Drive, Cleveland, OH 44143-2326. For further details, contact Corinne Gangloff at 440/684.9600, fax 440/646.0484 or e-mail firstname.lastname@example.org.