Frontiers of Environmental Science & Engineering | 2021
Preventing masks from becoming the next plastic problem
Abstract
Face masks help prevent the spread of coronavirus and other diseases, and mass masking is recommended by almost all health groups and countries to control the COVID-19 pandemic (Brooks et al., 2020). Recent studies estimated an astounding 129 billion face masks being used globally every month (3 million / minute) and most are disposable face masks made from plastic microfibers (Prata et al., 2020). With increasing reports on inappropriate disposal of masks, it is urgent to recognize this potential environmental threat and prevent it from becoming the next plastic problem. Waste plastics are one of the most prevalent environmental pollutants today. Even before COVID, over 300 million tons of plastics are produced globally per year and most end up in nature as waste (Geyer et al., 2017). Plastic products can not be readily biodegraded but fragment into smaller plastic particles, namely microand nanoplastics that widespread in ecosystems (Alimi et al., 2018; Nguyen et al., 2019). Ingestion of microplastics is known to cause direct adverse effects and also expose organisms to toxic chemicals and pathogenic microorganisms (Vethaak and Leslie, 2016). The pandemic and use of masks: Similar to the “throwaway living” style for other plastic products, disposable masks have symbolized pandemics from 2003 SARS to COVID-19 (Syed et al., 2003; Elachola et al., 2020). Although there is no official report on how many masks are disposed of, studies estimated billions of masks are needed monthly. China as the largest mask producer increased its production by a factor of 10 in March 2020 (source: “The daily output of masks exceeding 100 million” on Xinhua Daily Telegraph, 3 March 2020). Globally, a recent study estimated a monthly use of 129 billion face masks (Prata et al., 2020). This puts disposable masks on a similar scale as plastic bottles, which is estimated to be 43 billion per month. However, different from plastic bottles, ~ 25% of which is recycled, there is no official guidance on mask recycle, making it more likely to be disposed of as solid waste (Fadare and Okoffo, 2020). Mask materials and environmental fates and impacts: The common disposable surgical masks are made of three layers. The outer layer is made up of nonabsorbent material (e.g., polyester) that protects against liquid splashes. The middle layer is non-woven fabrics (e. g., polypropylene and polystyrene) created using a meltblowing process, which prevents droplets and aerosols via an electrostatic effect. The inner layer is made of absorbent material like cotton to absorb vapor (Fig. 1). Different polymers are used in mask manufacturing, and fabric polypropylene is used the most. Polypropylene is one of the most commonly produced plastics and the high usage has led to a large waste accumulation in the environment (Andrady, 2011). Once in the environment, the mask is subjected to solar radiation and heat, but the degradation of polypropylene is retarded due to its high hydrophobicity, high molecular weight, lacking an active functional group, and continuous chain of repetitive methylene units. These recalcitrant properties lead to the persistence and accumulation in the environment. The in situ weathering can generate a large number of micro-sized polypropylene particles (< 5 mm) during a relatively short period (weeks) and further fragment into nanoplastics (< 1 mm) (Mattsson et al., 2018). When not properly collected and managed, masks can be transported from land into freshwater and marine environments by surface run-off, river flows, oceanic currents, wind, and animals (via entanglement or ingestion) (Fig. 1). The occurrence of waste masks has been increasingly reported in different environments and social media have shared of wildlife tangled in elastic straps of masks. The author also observes disposable surgical masks in Odense, Denmark (Fig. 2). Like other plastic debris, disposable masks may accumulate and release harmful chemical and biological substances, such as bisphenol A, heavy metals, as well as pathogenic micro-organisms. Moreover, the Received November 18, 2020; Revised January 26, 2021; Accepted January 27, 2021; Available online February 28, 2021