Anti-bacterial treatment of banknote paper30 апреля 2014 года
From time to time the public becomes worried about the question of whether banknotes can be carriers of possibly pathogenic microorganisms and bacteria arises and the issue is widely discussed in media. These assumptions are based on the microbiological studies have been carried out by experts in various countries, and over a couple of years at least a dozen studies on this issue have been published. However, it should be noted that producers of banknote substrates long ago carried out their own studies in this field and found ways of solving many problems. Preventing the spread of potentially pathogenic bacteria that can be present on banknotes is an important environmental aspect that substrate manufacturers need to address.
Studies on the presence of microorganisms in the banknotes
The first time the presence of bacteria on the surface of banknotes was identified was in 1972 by the American Medical Association. In 2001 according to the Institute of Biomedical Studies in Rio de Janeiro (Brazil) eight various types of microorganisms can commonly be found on the substrate of the paper and plastic banknotes. The presence of bacteria, fungi and other potentially dangerous contaminants on banknotes has also been revealed in studies by other laboratories.
It was not long before solutions to address this problem were proposed by banknote paper manufacturers.
French paper mill Arp Wiggins was among the pioneers. They introduced a paper substrate with antibacterial and anti-fungal properties with the brand name BioGuard.
Protection against viruses was subsequently developed for it.
Many countries systematically disinfect money. In a number of countries banknotes are treated with ozone and ultraviolet or undergo heat treatment.
Over the period 2004-2007, Russian banknote and paper manufacturer Goznak, in cooperation with the Research Institute of Epidemiology and Microbiology of the Russian Academy of Medical Sciences (Gamaley Research Institute), carried out an analysis of the surface microflora on worn, banknotes. The purpose of these studies was to determine general microbial impurity of banknotes, identify the microorganisms and determination of integrated level of potentially pathogenic microorganisms. 100% contamination of all test banknotes was established during this study. It was found that about 20% of them were potentially pathogenic. The following schematic representation shows the structure and composition of the microflora. In total 34 species of potentially pathogenic microorganisms were revealed and identified. All banknotes were inseminated by spores of mould fungi.
Solutions against microorganisms in banknote paper
The cellulose materials of which banknotes paper is made are a good nutrient medium for microorganisms to grow. Their average life span on a banknote is about 1 to 2 months. The latter is connected not only with endurance of bacteria, but also with the development of paper production technologies. Before 1998 banknote paper in Russia was made in an acid pH environment with the use of melamine formaldehyde pitch and formalin. Today banknote paper is made in a neutral pH environment. It is good not only for preservation of mechanical durability of paper, but it also is very attractive to microorganisms. They perfectly feel, live and breed in the neutral environment. Therefore in the context of improvement of banknotes’ durability besides strengthening of barrier properties of paper substrate it is necessary to be concerned about its antimicrobial properties. Various antiseptics are used to decrease in microbiological activity on paper. While solutions for antibacterial treatment of paper certain conditions have to be developed:
- not to complicate the technological process of paper production;
- avoid affecting maintenance staff of paper manufacturer;
- not to reduce productivity of equipment of paper-mills;
- not to have negative effect on mechanical and other characteristics of paper.
After the analysis of existing antimicrobial substances, special attention was paid to polymeric additives of new generation. After conducting studies polymeric guanidines solution was selected. It reacts effectively not only on different viruses, fungi and bacteria, but also some insects - moth, bug-wood borer. At the same time the material is safe for warm-blooded as the living organism and water basins contain enzymes decomposing it.
When using in paper composition it positively effects its mechanical characteristics. It can be added into pulp, and applied on the surface of finished paper web, without breaking technological process. It is cationic and is independently and strongly fixed in paper composition.
Substance consumption is economic -about 5 grams / litre.
The technology was protected by the Patent RU No. 2318942 dated 12.07.2006. Today the technology of bactericidal additives to paper is implemented at the Saint-Petersburg and Krasnokamsk Paper Mills of Goznak and it is used in paper production for banknotes of different denominations.
Determination of antimicrobial properties in the paper
A study to determinate antimicrobial properties in samples of the paper was carried out in the Research Institute of Microbiology and Epidemiology using traditional for microbiologists techniques.
Method 1. Reveals antimicrobial properties of samples of special paper. It consists in determination of zones’ size of microorganisms growth inhibition around the paper with biocidal properties.
Method 2. Determination of death-time of 99.9% of test microorganisms on paper samples. It consists in determination of death-time of microorganisms after they are applied on test and control samples of paper.
Method 3. Characterises susceptibility of materials to microbial pollution in the course of their use. There were mould fungi and other microorganisms in the paper that was not treated.
Method 4. Evaluation of virucidal (anti-virus) properties of special paper.
The results on defining the preparation of the samples for consumption as well as place of its dosing control were received using these techniques. For reproduction of these techniques in the environment of non-specialised laboratories additional work was conducted with the attempt to obtain the adapted technique of paper tests on biocidal properties using harmless to health performers of strains of bacteria and viruses.
Technological control of production demanded creation of an operational technique of control of microbiological contamination in a mode: “here and now”. For levelling difficulties arisen using traditional for microbiologists techniques during the work in non-specialised laboratory of the Research Institute of Goznak, the new technique was developed. It establishes method for conducting control of antimicrobial properties of paper in laboratory conditions.
As a result of carried out work -the effective method enabling to reduce significantly potential biological contamination of banknotes. Use of antimicrobial paper for several years has shown both efficiency of special additives and control techniques. Let us note that today there are no proven cases of distribution of infections through banknotes, however use of antimicrobial additives makes it possible to reduce even the theoretical possibility of infection.