Abstract
In CORROSION’S June 2020 editorial,1 we explored the COVID-192 pandemic and the antimicrobial function of copper and silver enabled by corrosion Since that editorial was written, we have gone from 2 1 million confirmed infections and over 143,000 related deaths worldwide3 to 114,582,356 cases and 2,541,808 deaths as of March 1, 2021, according to the John Hopkins University COVID-19 Dashboard 3 A cause of this large increase is the high rate of the spread of SARS-CoV-2 (the virus that causes the coronavirus disease COVID-19), which is 40-fold greater than that of SARS-CoV-1 4 Recently, a more highly contagious mutation has been reported which makes this virus (referred to as the COVID-19 virus throughout this editorial) even more transmittable 5 This makes the COVID-19 virus even more difficult to control4 than SARS-CoV-1 Surgical masks are often made of three different fiber layers to prevent the entry of viruses: the outside layer is designed to stop liquids from traveling inwards towards the face, mouth, and nose without encountering an obstacle;an interlayer acts as a barrier against viruses and bacteria;and an inner layer absorbs moisture exhaled by the wearer 7,8 Different materials can be synthesized to act as protective coatings where the fabric can be designed to control pore size relative to airborne aerosol and particulate dimensions,4 as well as function in other ways such as by electrostatic attraction of aerosol particles (a) Possible pathways for transmission of the COVID-19 virus involving human atomization of viruses during the coughing or sneezing of an infected person Elemental copper and silver10 possess intrinsic antimicrobial properties that are enabled by corrosion which releases free metal cations 25,32,34 The free ions are distinct from copper ion sequestering in the oxide layer formed over the surface of the alloy or dissolved but chelated (to form a compound usually with an organic species in the environment, whereupon the organic is bonded to the copper ion) with some molecular species in solution 25,32,34-37 Inactivation time (>99 9% reduction) of Escherichia coli (HCB1) and Legionella pneumophila bacteria in various soluble [Cu2+] concentrations Because the corrosion thermodynamics, kinetics, and the stability of the oxidized products formed can all differ with the molecular identity of the product, inoculum, saliva,40 and perspiration “solution chemistry,”32 these considerations need to be evaluated carefully to fully understand the efficacy of both Cu as a surface disinfectant and Cu compounds as disinfecting agents impregnated in PPE
Highlights
A cause of this large increase is the high rate of the spread of SARS-CoV-2, which is 40-fold greater than that of SARSCoV-1.4 Recently, a more highly contagious mutation has been reported which makes this virus even more transmittable.[5]
While Part 11 of this editorial series focused on copper and, to a lesser extent, silver corrosion when utilized as a hightouch surfaces in humid air and perspiration, Part 2 explores incorporating copper oxidation products as antiviral agents into “protective gear,” such as face masks, air filters, fabrics, and clothing
In order to contribute to the public dialogue regarding the important role of protective gear, we seek to present some of the “science behind it” or “how it works” of the antiviral properties of copper and its compounds
Summary
Copper’s antimicrobial properties[19,20] have been used by ancient civilizations for water purification, skin ailments, and wound healing.[20,21] Over time, additional uses for copper were discovered. Materials containing impregnated oxidized copper oxide or other compounds possess antimicrobial properties[16,17] including antiviral properties.[16,29,41] The concept relies on copper ions which are stored and released from either natural or (2) Virus and bacteria survival as a function of time when exposed a biocidal agent or anti-biocidal material capable of inactivation are often expressed as log10(Nt/No), where N is the unit representing the “concentration” of virus particles or bacteria express as the number of colonies, particles, or units of virus/mL; Nt is the concentration at a given point in exposure time t; while No is the initial concentration. In the case of metal oxides or soluble halide-based compounds, the copper ion concentration in the arriving droplet deposited near the particle is likely below its equilibrium solubility at first (the “X” in Figure 3 indicates the initial solution chemistry of simulated human perspiration containing no copper ions initially). The valence state of copper (Cu+ vs. Cu2+) affects solubility and is largely determine by the oxidizing power of the solution (represented here by the different electrode potentials, 0 VSHE and 1 VSHE)
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