The drying test method for the surface of an object in a realistic pollution environment

's drying test of surfaces in real-world polluted environments
- Corning Vice President and Program Director Joydeep Lahiri
Summary
The spread of deadly viruses and drug-resistant bacteria is a major health threat to humans today. The pandemic of the new coronavirus SARS-CoV-2 is a warning that uncontrollable highly contagious viruses can have a dramatic impact on our lives. Although human-to-human transmission of the virus is the main mode of transmission, both the Chinese Centers for Disease Control and Prevention and the U.S. Centers for Disease Control and Prevention have warned that exposure to surfaces carrying live viruses could also

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While hand washing and proper cleaning with disinfectants are still necessary to prevent germs, the reality is that surface contamination is persistent and the cleaning effect is not sustainable. Self-sterilizing surface materials and coatings containing antimicrobial components continue to reduce viruses and bacteria as a complementary solution to routine disinfection measures.
, however, different self-sterilizing solutions contain different active ingredients, and their labeling statements follow different testing standards. Recently, the U.S. Environmental Protection Agency announced that it allows antimicrobial declarations on surfaces with long-term effects, but that they must be based on drying testing standards that simulate a realistic polluted environment, which needs to be performed at low temperatures (23±4 degrees C) and take no more than 2 hours to test. "Wet tests" are still used as a benchmark in many regions of the world, such as JIS Z-2801, which is performed at high temperatures (37±4 degrees C) and has a 24-hour test time on the surface in wet conditions. Studies have shown that some common antimicrobial components, such as silver, can achieve effective antiviral and antibacterial levels at high humidity and high temperatures. However, the common sources of pollution in daily life do not meet these conditions. The materials that perform well under dry test conditions are very limited, mainly copper. In order to provide additional protection for self-sterilizing surfaces, we advocate the widespread adoption of drying testing standards similar to those required by the U.S. Environmental Protection Agency for products sold in the United States.
of deadly viruses and drug-resistant bacteria is a major health threat to humanity today. The pandemic of the new coronavirus SARS-CoV-2 is a warning that uncontrollable highly contagious viruses can have a dramatic impact on our lives. At a time when the world is struggling to maintain normalcy and try to prevent a new outbreak, we must develop appropriate programmes to prevent the spread of the outbreak in public and private spaces. Unfortunately, however, even when wearing a mask and maintaining a social distance, the virus is still highly susceptible to transmission. Although human-to-human transmission of the virus is the main mode of transmission, both the Chinese Centers for Disease Control and Prevention and the U.S. Centers for Disease Control and Prevention have warned that exposure to surfaces with live viruses could also cause transmission.
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, depending on the composition of the surface under contact, the new coronavirus SARS-CoV-2 can survive for hours to days on surfaces such as desktops and doorknobs.
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, how do we disinfect and control surfaces that people come into frequent contact with in the workplace and in public places?
before the outbreak, self-sterilizing surfaces and antimicrobial coatings were niche products. Today, businesses are actively looking for solutions that create a healthy environment for their customers and employees. Urban complexes such as homes and offices, which house millions of people, urgently need to do more to reduce germs in crowded areas. Schools, hospitals, kindergartens and nursing homes also need to take more precautions to prevent the spread of germs. There are still some people who are reluctant to step out of their homes to resume their daily lives, and the large-scale use of self-sterilizing surfaces can help improve the situation. An environment in which an object's surface can continuously kill bacteria and viruses on its own can reduce fear and stress and reassure people who return to work and frequent public places.
the large-scale popularity of antimicrobial coatings is based on the establishment of a universal and standardized testing standard. Products with antimicrobial properties claim to inhibit microbial growth, but these claims are limited by their testing standards. The most commonly used test standard for antimicrobial surfaces is the "wet test method" (JIS Z-2801). The test is designed to assess the effectiveness of surface coatings on objects that inhibit the growth of microorganisms. A large amount of liquid bacterial culture is used during the test to keep the surface under test moist throughout the experiment. Wet testing is required at high temperatures ± 37 degrees Celsius and high humidity greater than 80%. Under this test standard, the active ingredient on the test surface has a full 24 hours to kill the microorganisms under test.
3 。 While wet testing does prove the effectiveness of antimicrobial products, the test data represent only the established test environment, and these parameters do not fully simulate the environment in which we live and the true state of the antimicrobial surface. In fact, studies have shown that certain antimicrobial agents, such as silver-based antimicrobials, are highly active only at high temperatures and humidity.
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imagine that in an office that requires shared office supplies, a shared computer, and frequent access to doorknobs, the environmental conditions are quite different from those set by the wet test. In the workplace, humidity and temperature are usually low and the environment is dry, and due to the high frequency of use, the surface of the object is likely to be contaminated with microorganisms more than once every 24 hours.
to raise standards for self-sterilizing surfaces, we need to adopt a more accurate test standard widely. The U.S. Environmental Protection Agency has created a "dry test" that can more realistically simulate everyday environmental and real-world pollution. The test was conducted ± 23 to 4 degrees C (room temperature) and 40-50% ambient humidity. Products that pass the drying test must completely kill the surface microorganisms in 2 hours or less. In October 2020, the U.S. Environmental Protection Agency announced its latest guidelines: establish a rapid review system to help surface disinfectant products gain faster access to performance statements for new coronavirus SARS-CoV-2, while the U.S. Environmental Protection Agency has expanded the category of antimicrobial products to cover solid surfaces and coatings as complementary long-acting antimicrobial products.
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Although the testing standards for wet testing do not represent real living environments, many common surface antimicrobials are still being tested and validated with this standard. Current wet tests include surface antimicrobial efficacy tests (ISO 22196
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, JISZ 2801
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and GB/T 21866
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) and surface antiviral efficacy tests (ISO 21702
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).
is one of the most commonly used antimicrobial agents, and its efficacy in completely killing microorganisms on the surface of objects depends on the test environment of such wet testing methods. Under high humidity and high temperature conditions, and when the silver ions reach a sufficient quantity, the silver-based antimicrobial agent can meet the >99.9% killing standard shown by other antimicrobial products.
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when the use of silver-based antimicrobial products closer to the real-world drying test method, its antimicrobial efficacy often fails. However, copper, another well-known antimicrobial metal, has been shown to pass drying tests.
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although the chemical mechanism behind this phenomenon is still controversial, several experiments have shown that copper is a more effective antimicrobial agent for self-disinfecting surfaces. In drying tests conducted by researchers such as Harold T Michels, they compared three different types of surfaces: uncoated stainless steel surfaces, stainless steel surfaces coated with silver-based antimicrobial agents, and a variety of copper-containing surfaces.
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analysis showed that over a period of about 75 minutes, a variety of MRSA superbugs on copper-containing surfaces were completely killed, while the surface coated with silver-based antimicrobial agents remained large numbers of bacteria after 6 hours.
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to promote the development of the self-sterilizing surface market, it is necessary to adopt a
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drying test method similar to that of the U.S. Environmental Protection Agency. Compared with the traditional wet test method, this method is more practical, can better simulate the real environment, help to screen for self-sterilizing surfaces such as copper more effective materials. Looking ahead, the demand for antimicrobial products will increase significantly. Widespread adoption of testing standards closer to the real world will help break down niche product barriers and expand the scope of application of antimicrobial technology, so as to better address the urgent needs for the benefit of the global community.
reference
1. N van Doremalen, et al. Aerosol and surface stability of HCoV-19 (SARS-CoV-2) compared to SARS-CoV-1. New England Journal of Medicine (2020).
3.
Japan Standards Association. Japan Industry Standards JIS Z 2801. Antibacterial processing products - antibacterial test methods and antibacterial effects (2000)
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Michels, H T et al. "Effects of temperature and humidity on the efficacy of methicillin-resistant Staphylococcus aureus challenged antimicrobial materials containing silver and copper." Letters in Applied Microbiology vol. 49,2 (2009)
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The U.S. Environmental Protection Agency. Protocol for the Evaluation of Bactericidal Activity of Hard, Non-porous Copper-Containing Surface Products (2016)
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International Organization for Standardization. ISO 22196 - 2011 Plastics and other holeless surface antibacterial assays
8.
China's National Standardization Management Committee. GB/T 21866 - 2008 Antibacterial coating (paint film) antibacterial assay and antibacterial effect
9.
International Organization for Standardization. ISO 21702 - 2019 Plastics and other holeless surface antibacterial