## 4 Findings and Discussion
### Management of Waste  
In healthcare contexts, PPE waste has been included in the medical waste category; therefore, it is expected to be properly disposed of through incinerations followed by the landfill of residual ash or the use of disinfection techniques, such as microwave or chemical disinfectants, all of which are widely used to protect public health [3; 50]. However, the extensive use of PPE has overwhelmed the available waste management infrastructures, for example incinerators, which have operated beyond their capacity. For example, the increase in medical waste in Wuhan (China) forced the use of mobile incinerators, whereas in the case of The United Kingdom, municipal waste incinerators were given permission to process medical waste [51]. In the case of PPE used by the population, guidelines during the pandemic recommended that waste generated by home-quarantined patients should be stored in dedicated containers after the application of a disinfectant spray [50]. However, currently, PPE used at home is disposed of with municipal waste, which means it is being disposed of by the public in an incorrect manner. Some studies have reported the poor waste management practices and a lack of environmental awareness among the population during the pandemic, concluding that the density of the use of disposable face masks varies from one region to others, increasing in the tourist season and touristic regions [1; 4; 16; 17], as well as in coastal areas [7]. Thus, face masks have been found on the beaches of Lima, Peru, the Chilean coast [18], Soko island in Japan, and on the Kenyan coast [19] and the Persian Gulf [52] areas, among others. PPE density varies by different regions of the world, from \(1.13\;\times\;10^{-5}\) PPE/m\({}^{2}\) along the Moroccan shoreline to \(6.29\;\times\;10^{-3}\) PPE/m\({}^{2}\) in the case of the Peruvian coast, increasing in the summer, or between \(0\) and \(8.22\;\times\;10^{-3}\) to \(5.6\;\times\;10^{-2}\) in the case of Canadian and Kenyan streets, respectively [16]. Consequently, we found that studies on PPE waste disposal in landfills or their improper disposal in the environment [53] evidenced that around 75% of PPE waste plastic ended up in landfills, public places, urban environments, and natural environments, such as beaches and ocean beds [3; 51]. One of the pillars of the circular economy is the hierarchy in waste management defined by the Waste Framework Directive to prevent and reduce the negative impact caused by the generation and management of waste and to improve resource use efficiency. To ensure that, new challenges for municipal solid waste management and disposal have arisen, including the separate collection of used face masks at the source [20; 54; 55] to avoid infection and cross-contamination [56]; however, some options described below have been explored according to the cited directive hierarchy:  
* Although single-use masks have a higher effectiveness in preventing the transmission of bacteria and viruses, studies have shown that reusable masks could have adequate performance after a decontamination process [13]. This solution has a lower environmental and economic impact, preventing waste production. As such, some possibilities have been explored to re-use disposable masks in order to prevent excessive waste generation during the pandemic. For example, a study showed that dry heat at \(70\;^{\circ}\mathrm{C}\) for 1, 2, and 3 h could successfully inactivate the H1N1 indicator virus in N95 respirators and surgical face masks without changing their shape, components, or filtering efficiency of bacterial aerosol [27]. N95 respirators have been decontaminated using vaporized hydrogen peroxide (VHP) or ultraviolet (254 nm wavelength; UVC) radiation, maintaining their integrity [26].