**3.2 Spraying of chemical disinfectants and UV irradiation of surfaces in indoor spaces**

In indoor areas, routine application of disinfectants by spraying or fogging (i.e., fumigation or misting) is usually not recommended for COVID-19 control because this strategy may not remove all the contaminants outside the spray zones (i.e., not contacted by the spray/fog) [71]. Moreover, fogging using formaldehyde, chlorine-based agents, and quaternary ammonium compounds may also result in risks to the eyes and irritation of the respiratory mucosa or skin [72, 73]. However, some countries have allowed the no-touch methods for applying specific chemical disinfectants, such as vaporized hydrogen peroxide (HPV) in vacated spaces in healthcare settings [74]. In one such experiment, HPV was demonstrated to inactivate >4 log10 of feline calicivirus, transmissible gastroenteritis virus, human adenovirus-1, etc. at lower percentages of active compound (1400 ppm) and lower potential toxicity on living cells [75]. Hydrogen peroxide and 2-phenyl phenol are usually employed for surface disinfection and food sanitation and act as valid alternatives to sodium hypochlorite.

Ultraviolet light irradiation devices have also been modified for use in healthcare settings. Exposure to sunlight or UV light drastically limits coronavirus survival, as is the case for many microorganisms [76]. The efficacy of UV irradiation devices is dependent on several factors, such as irradiation dose, lamp placement, the distance between surface and UV device, wavelength, exposure time, and duration of use, etc. [10] along with fluence of UVC (J/m<sup>2</sup> , mJ/cm2 , etc.) which may take into account all other factors [77]. On the basis of review of the UVC inactivation literature, a consensus efficacy of 0.5 to 2 log10 inactivation of SARS-CoV-2 per mJ/cm<sup>2</sup> has been demonstrated. These results indicate that SARS-CoV-2 is quite susceptible to UVC inactivation [24].

In another experiment, more than 3 log10 inactivation of SARS-CoV-2 was detected with a UVC dose of 3.7 mJ/cm2 on samples contaminated with comparable virus density to that found in COVID-19 patients. However, the complete inactivation of SARS-CoV-2 was observed with 16.9 mJ/cm2 of UVC [78]. The UV irradiation devices developed for disinfection in health care settings usually are used during terminal surface sanitization i.e., sanitization of rooms after discharge of patient and in rooms unoccupied by the staff and patients. In one of the studies, deep ultraviolet light-emitting diode (DUV-LED) was used for inactivation of SARS-CoV-2 from a COVID-19 patient [79]. Such a study shows the importance of development of DUV-LED based devices to prevent virus contamination of the air and surfaces. However, when using the no-touch disinfection methods, such as fumigation or UV treatment, prior manual cleaning of surfaces is also essential [80]. However, during surface cleaning care should be taken to prevent the re-aerosolization of virus from the surface material, which could represent a potential source of infection. Moreover, for optimal effectiveness, these no-touch approaches should not be considered as replacements for surface cleaning. Rather, after

#### *Environmental Persistence of SARS-CoV-2 and Disinfection of Work Surfaces in View… DOI: http://dx.doi.org/10.5772/intechopen.104520*

surface disinfection using appropriate virucidal agents, the no-touch approaches can be used to reach surfaces not reached by the surface cleaning methods.

Outdoor application of disinfectants, such as spraying or fumigation on streets and other public places, may not advisable since most of the action of many classes of disinfectant agents are adversely impacted the presence of organic dirt and debris on surfaces. The body surface spraying of individuals with chemical disinfectants in a cabinet, tunnel, or chamber is also not advisable [81]. The research data do not provide evidence of the reduced ability of an infected person, so treated, to spread the virus. Moreover, direct spraying of individuals with a chemical disinfectant, such as a chlorine-releasing agent, may result in irritation in the eye or skin, and may cause nausea, and vomiting, etc. [82, 83].

Healthcare and sanitation personnel involved in disinfection should be provided training in the use of personal protective equipment (PPE) especially in areas where COVID-19 patients are present [84]. Depending upon the disinfectant to be used, healthcare workers involved in the disinfection process should be equipped with a PPE kit including impermeable aprons, face masks, face shields, rubber gloves, and closed shoes [85]. Also, depending upon the disinfectant used, cleaning solutions should be prepared and used in ventilated areas and the mixing of two or more disinfectant solutions should be avoided, because the resultant mixture may be harmful to human health and to surfaces.

### **3.3 Disinfection in healthcare settings**

For environmental cleaning and disinfection of clinical premises, specific international and local authority guidelines should be followed. Surfaces and items with high-touch possibilities, such as door handles, light switches, tables, bed rails, intravenous pumps, etc., should be given proper attention during disinfection. Healthcare workers may act as resource persons for disinfection and cleaning of hospital premises. They should be made aware of cleaning schedules and the risks associated with touching surfaces and equipment during patient care [86]. After a thorough cleaning of environmental surfaces with detergent, 70% alcohol, ≥0.5% hydrogen peroxide, or 0.1% (1000 ppm) to 0.5% (5000 ppm) of chlorine-releasing disinfectants, including sodium hypochlorite, sodium chlorite or chlorine dioxide, can be used for overall disinfection of hospital settings against SARS-CoV-2 [87]. During preparation and application of disinfectants, the use instructions and material safety data sheets supplied by the microbicide manufacturers should be strictly followed to avoid any impacts to humans and to equipment surfaces.

#### **3.4 Disinfection in non-healthcare settings**

The risk of fomite (indirect) transmission of SARS-CoV-2 may apply as well to settings outside of hospitals and other healthcare settings. To avoid the risk of any such transmission, it is important to reduce the possibility of contamination in possible high-touch surfaces in offices, homes, schools, gyms, etc. High-touch surfaces in these non-healthcare settings may be thoroughly cleaned with detergent to remove organic dirt and debris before chemical disinfection using sodium hypochlorite (0.1% or 1000 ppm) or alcohol (70–90%) [10].

## **4. Nanotechnology-based formulations for SARS-CoV-2 control**

Although most of the chemical disinfectants are effective against SARS-CoV-2, they are often associated with several drawbacks, such as requirements for higher

concentrations for proper virucidal effect, reduced efficacy in the presence of organic substances, and possible risks associated with the environment and public health [88]. The nosocomial transmission through inappropriate PPE may contribute to infection and death of healthcare workers. To prevent nosocomial transmission, PPE can be treated with copper nanoparticles or copper oxides and salts [89]. Nanoparticle-coated non-woven tissues or cloths using metal-grafted graphene oxide (GO) have been found effective against surrogate viruses, including SARS-CoV, MERS-CoV, and Ebola virus [90]. The coating of silver nanoparticles on face masks made up of woven and nonwoven textiles showed efficacy of 99.99% against surrogate viruses for SARS-CoV-2 [91].

Several metallic nanomaterials, such as titanium dioxide, silver, copper, etc. have been proposed as alternatives to chemical-based disinfectants, due to their characteristic antiviral activities, and effectiveness at a much lower concentrations [92]**.** Nanomaterials act as a virucidal agents via promoting the surface oxidation by toxic ions, leading to inhibition of viral dissemination by inhibiting the binding or penetration of viral particles. The virus penetration to host cells is inhibited by the generation of reactive oxygen species, and photodynamic and photothermal capabilities which destroy the viral membranes [88].

Facial masks coated with silver nanocluster/silica composite showed viricidal effects against SARS-CoV-2 [93]. Similarly, titanium dioxide and silver ionbased nano-formulations can be used for surface disinfection [88]. The cellulose nanofiber-based breathable and disposable filter cartridge may filter particles, including viruses, even those less than 100 nanometers in size [94]. Because of their unique chemical and physical properties, along with a high surface area to volume ratio, some of the nanomaterials such as graphene nanomaterial can be used to adsorb and remove SARS-CoV-2 from surfaces [95]. Graphene-based nanomaterial has been used to make a reusable mask that may trap viruses and inactivate them with the help of an electrical charge [96]. Graphene in association with copper, silver, and titanium nanoparticles, may enhance the antiviral activity and durability of PPE material [90]. Similarly, quaternary ammonium salts, peptides, or polymerbased nanoparticles may promote the oxidation of viral envelopes and inhibit their replication [97]. However, nanomaterials should be used with caution to avoid any possible health hazards. The adverse effects of metallic nanomaterials on the environment and human health can be minimized by utilizing biodegradable nanomaterials, including polymeric lipid-based nanomaterials [98]. However, to the best of available literature, it is difficult to suggest the complete reliance on disinfectant efficacy of nanoparticle-coated PPE, especially against SARS-CoV-2. Hence, traditional chemical-based disinfectants are still primarily in use. However, nano-based formulations represent a promising field of research and will assist in control of current and similar viral outbreaks in the future [99].
