Generation of waste personal protective equipment (PPE) related to COVID-19 using quantitative forecasting technique

Abstract

With the prolonged COVID-19 pandemic worldwide, lifestyles have totally changed and the characteristics of waste generation have also changed accordingly. Among the various wastes related to COVID-19, waste personal protective equipment (PPE), which was used to prevent infection of COVID-19, can be an indirect route for the infection of COVID-19. Hence, it requires proper management with estimating waste PPE generation. In this study, the estimation of generation amount of waste PPE in consideration of lifestyle and medical practice is proposed by quantitative forecasting technique. In the quantitative forecasting technique, the generation source of waste PPE consisted of household and test/treatment of COVID-19. For case study in Korea, the amount of waste PPE generated from household is evaluated by applying the quantitative forecasting technique reflecting the population and measures in lifestyle due to COVID-19. Also, the estimated amount of waste PPE generation from test and treatment of COVID-19 was evaluated to have a meaningful reliability compared with other observed values. This quantitative forecasting technique can estimate the amount of waste PPE generation related to COVID-19 and develop safe management measures for waste PPE in many other countries by modifying country-specific lifestyles and medical practices.

Introduction

At the early stages of the spread of COVID-19 in the world, gathering people have been restricted through telecommuting, on-line classes at school, and restriction for domestic and international travel [1, 2]. These measures have been somewhat relaxed due to the introduction of vaccines and treatments for COVID-19 [3]. However, the COVID-19 pandemic is persisted by introducing COVID-19 mutates and its impact on infection outbreaks is significantly increased. Since COVID-19 is a virus that causes respiratory symptoms, the direct route of infection can be a droplet caused by coughing and sneezing [4, 5]. Accordingly, measures such as mandatory wearing of face masks have been taken around the world to prevent the spread of COVID-19 [6]. Face masks have become a daily necessity in today's life. In addition, isolation facilities are being operated to control the infection of COVID-19 from test and patient treatment sites to surrounding areas, and high-quality PPEs are being used to protect medical personnel [7]. In particular, COVID-19 on the surface of PPEs can provide an indirect route of infection [4, 5]. There is a possibility that COVID-19 exists on the surface of waste PPE generated from daily life, test and treatment of COVID-19. PPEs such as face mask, eye protection, coverall and others are composed of various polymers such as polycarbonate, polypropylene, polystyrene, and others [8–10].

Many researchers have studied the surface stability of COVID-19. They found that surface stability of COVID-19 on the material of PPE was evaluated as 3–4 days in plastic [11, 12], 2–4 days in polypropylene [13, 14], and 2 days in polystyrene [15]. Kampf et al. reported that COVID-19 virus can remain on surfaces such as metal and glass for up to 9 days [16]. In particular, Chin et al. evaluated the surface stability of COVID-19 as 4 days for the inner layer of face mask and 7 days for the outer layer of face mask [11]. Since the survival time of COVID-19 virus varied up to 9 days from previous studies, it was found that COVID-19 virus could remain in face mask for several days.

Therefore, waste PPE can become a route of indirect infection of COVID-19 to the general public, waste collectors, and waste treatment facility workers. There is a lack of proper management services for waste PPE in developing countries, and medical facilities worldwide does not safely manage as a medical waste [17–19]. In addition, many international organizations are concerned about the rapid increase in various wastes caused by the COVID-19 pandemic and the adverse effects on the environment such as plastic pollution and marine pollution [17, 20, 21]. WHO announced recommendations such as reduction of waste PPE through rational use of PPE including minimization of unnecessary use of PPE, minimization of use of packaging of PPE, and others for the management of health care waste related to COVID-19 [22]. Mol and Caldas suggested that improper domestic solid waste management could increase the spread of coronavirus [23]. Rhee emphasized that waste PPE should be disposed of separately from other wastes and incinerated or landfilled to prevent indirect infection of COVID-19 by waste PPE [24].

The COVID-19 pandemic has brought a new normal era and the characteristics of waste generation have also changed in a totally changed situation. The characteristics of waste generation can be considered by amount, volume, type, and source of waste and the characteristics of waste can be very important to manage waste properly and to decide proper methods. Hence, a methodology for estimating the generation amount of waste PPE is required to build a safe management plan or proper measures for waste PPE considering different waste characteristics from municipal solid waste and providing a path of indirect infection.

Benson et al. estimated the amount of waste single-use face mask using population, arbitrary percent of facemask acceptance rate, the average daily face masks per capita, and several assumptions [25]. Lee et al. estimated the amount of single-use face mask discarded in Korea considering the population, mask use cycle, and others [26]. These studies are only limited to waste PPE generated from households, but waste PPE from medical practices related to COVID-19 was not considered. WHO suggested a method for calculating the volume of medical waste related to COVID-19, which was based on the container volume of medical waste, and provided assumptions for waste density, and others [24]. Although the comprehensive volume of medical waste was estimated through the method proposed by the WHO, there did not indicate the characteristics of generation amount of waste PPE according to medical practice in response to COVID-19. Since the comprehensive volume of medical waste can be referenced for short-term measures, in addition, it may lead to insufficient construction of a medical waste management infrastructure. Therefore, it is necessary to prepare countermeasures against COVID-19 and other infectious diseases by developing elaborated estimation models for the compressive volume of medical waste that reflect rapidly changed medical practices due to COVID-19.

In this study, the estimation model for the generation or amount of waste PPE is proposed by a quantitative forecasting technique. In the estimation model for generation amount of waste PPE, sources of waste PPE are considered from several points such as household, test and treatment of COVID-19. To estimate the generation amount of waste PPE, the weight of face mask used in household and PPEs used in medical practice related to COVID-19 were measured. In addition, face masks used in household and PPEs used in test and treatment of COVID-19 were considered in the estimation model. Finally, the suitability of this estimation model was evaluated by calculating the generation amount of waste PPE applying this estimation model as a case study in Korea.

Development of the estimation model

Characterization of PPE

To prevent the spread of COVID-19, it is mandatory to wear the face mask in daily life, and a guideline for wearing the face mask has been prepared [27]. In the guideline, the grades of the face mask worn in daily life such as KF-AD, KF-80, and KF-94 are recommended. These face masks are classified according to their filtration efficiency. The filtration efficiency of KF-AD and KF-80 for aerosol size of 0.6 μm is about 75% and 80% or more, respectively [28, 29]. KF-94 should have a filtration efficiency of 94% or more for aerosol size of 0.4 μm [28].

In daily life, the face masks for general use without the grade of filtration efficiency are also found, and the face mask for general use can be also shown in Fig. 1a. A Level D PPE set is used in the test and treatment of COVID-19, which consists of 5 PPEs: eye protection, face mask (KF-94 or N95), medical gloves, coverall, and shoe cover (see Fig. 1b). Since there may be a risk of infection by PPEs generated from test and treatment of COVID-19, it should be considered to collect the PPEs separately and to estimate the generation amount of PPE waste additionally. However, the weight of PPE set of Level D can be different from manufacturers because the material and structure of PPE of level D can vary in manufacturing and producing processes.

Fig. 1.

Type of PPE

The measurement of weight of PPE in this study, face masks used in daily life were collected from people without infecting COVID-19. Since there is a risk of infection in PPE generated from test and treatment of COVID-19, new PPE sets of Level D from 3 major manufacturers were analyzed and characterized.

Design procedures for the estimation model of generation amount of waste PPE

To design the estimation model of generation amount of waste PPE related to COVID-19, a four-step procedure was performed as shown in Fig. 2. First, it was a very close relationship between the generation amount of waste PPE and the change of daily life by the countermeasures of COVID-19 through screening test and treatment for COVID-19. In some previous studies, the amount of discarded single-use mask was predicted considering the population, mask use cycle, and others [25, 26]. In this study, the sources of waste PPEs were considered by dividing into two groups such as household, and test and treatment of COVID-19. Specially, the generation amount of waste PPE from test and treatment of COVID-19 can be expressed by a special estimation model reflecting the characteristics of the medical process. Second, the characteristics in the use of PPE in daily life and in screening tests and treatment according to the response to COVID-19 were reviewed to analyze the parameters for the estimation model. The necessary parameters in the estimation model of the generation amount of waste PPE related to COVID-19 were different from those in the previous studies. Details of the derived estimation model of the generation amount of waste PPE related to COVID-19 are described in Sects. “Design procedures for the estimation model of generation amount of waste PPE” and “Parameters in estimation model of generation amount of waste PPE”. Third, to calculate the generation amount of waste PPE using the estimation model, relevant statistical data and waste PPE characterization were considered with matching the parameters. Fourth, the amount of waste PPE generated can be calculated by the estimation model. Specially, the reliability of calculated amount of waste PPE from test and treatment of COVID-19 is verified by comparing the result with the national waste statistics observed in Korea and others.

Fig. 2.

Design and procedure of estimation model of the generation amount of waste PPE

Estimation model of the generation amount of waste PPE

The estimation model for calculating the generation amount of waste PPE was proposed by a quantitative forecasting technique requiring population and statistical data related to COVID-19. In general, a quantitative forecasting technique is a mathematical process to estimate the quantity and the quality for a target item based on objective data, and can be used to make informed decisions about waste management strategies or processes.

The sources of generation of the waste PPE can be considered by 2 divisions such as household, and test and treatment of COVID-19. Hence, the total generation amount of waste PPE can be composed as shown in Eq. (1).

$$\mathrm{Waste}\mathrm{PPE}\left(\mathrm{total}\right)=\mathrm{Waste}\mathrm{PPE}\left(\mathrm{household}\right)+\mathrm{Waste}\mathrm{PPE}(\mathrm{test}\mathrm{and}\mathrm{treatment})$$ 1

where Waste PPE (total) is the generation total amount of waste PPE (ton/month), Waste PPE (household) is the generation amount of waste PPE from households (ton/month), and Waste PPE (test and treatment) is the generation amount of waste PPE from test and treatment (ton/month).

Waste PPE (household) can be calculated by Eq. (2).

$$\mathrm{Waste}\mathrm{PPE}\left(\mathrm{house}\mathrm{hold}\right)=\frac{P\times \mathrm{MF}\times \mathrm{MC}\times \mathrm{WM}\times D}{1,000,000}$$ 2

where P is the population (capita), and MF is the fraction of the face mask wearer among population. MC is the face mask use cycle (ea/capita/day), WM is the weight of face mask (g/ea), and D is the number of days per month (day/month).

Waste PPE (test and treatment) can be expressed by the sum of Waste PPE (test) and Waste PPE (treatment) as shown in Eq. (3). Waste PPE (test) and Waste PPE (treatment) can be calculated through Eqs. (4) and (5), respectively.

$$\mathrm{Waste}\mathrm{PPE}\left(\mathrm{test}\mathrm{and}\mathrm{treatment}\right)=\mathrm{Waste}\mathrm{PPE}\left(\mathrm{test}\right)+\mathrm{Waste}\mathrm{PPE}(\mathrm{treatment})$$ 3

$$\mathrm{Waste}\mathrm{PPE}\left(\mathrm{test}\right)=\frac{{\sum }_{i=1}^n{\mathrm{PT}}_i\times M\times {\mathrm{PU}}_{\mathrm{test}}\times \mathrm{PW}}{1,000,000}$$ 4

$$\mathrm{Waste}\mathrm{PPE}\left(\mathrm{treatment}\right)=\frac{{\sum }_{i=1}^n(C_i-R_i)\times \mathrm{Th}\times {\mathrm{PU}}_{\mathrm{th}}\times \mathrm{PW}}{1,000,000}$$ 5

In Eqs. (4) and (5), i is the date, n means the day in each month. PW is the weight of 1 set of PPE (g/set of PPE). And in Eq. (4), PT is the number of people tested for COVID-19 daily. M is the number of medical personnel required for one COVID-19 test (medical personnel/people tested). PU_test is a PPE set required for one medical personnel participating in the COVID-19 test (set PPE/medical personnel).

In Eq. (5), C is the daily cumulative number of confirmed case, and R is the daily cumulative number of released case from quarantine. Th is the number of quarantined patients receiving COVID-19 therapy per day (therapy/patient), and PU_th is a PPE set required for one COVID-19 therapy (set PPE/therapy).

Results and discussion

Characteristics of PPE

Table 1 shows the results of the weight range of the face mask from household and a Level D PPE set used for test and treatment of COVID-19. The weight of the face mask collected from household ranged from 3.15 to 6.23 g, and the weight of the face mask increased in the order of general masks, KF-AD, KF-80, and KF-94. The total weight of the Level D PPE set used for testing and treatment of COVID-19 was measured in the range of 284.22–427.52 g. The weight of the components of the Level D PPE set decreased in the order of coverall, eye protection, shoe cover, medical gloves, and face mask.

Table 1.

Weight of PPE by type

Generation source	Type of PPE	Unit	Weight (mean)
Household	Face mask	g/ea	3.15 ~ 6.23 (4.64)
Test and treatment of COVID-19	Eye protection	g/ea	53.13 ~ 67.47 (60.23)
	Face mask (N95 or KF-94)	g/ea	5.82 ~ 6.74 (6.36)
	Medical gloves	g/ea	26.76 ~ 36.95 (30.92)
	Coverall	g/ea	119.85 ~ 280.31 (203.19)
	Shoe cover	g/ea	40.83 ~ 64.32 (54.55)
	Total	g/set	284.22 ~ 427.52 (355.26)

Parameters in estimation model of generation amount of waste PPE

The parameters required for the estimation model for calculating the amount of generated waste PPE can be decided by reviewing several studies and the characteristics of PPE. To estimate the reliability of the estimation model as shown in Eqs. (2), (4), and (5), the case of Korea (Republic of) was performed.

The population in Korea can be obtained from the database of the Ministry of Interior and Safety [30]. The statistical data on COVID-19 such as confirmed cases, released cases from quarantine, and people tested announced daily were used by Ministry of Health and Welfare (MOHW) in Korea [31].

The parameters in the estimation model for calculating the generation amount of waste PPE can be shown in Table 2. In Eq. 2, MC was derived from the result of survey related to the usage of the face mask in Korea, and the surveys were conducted by Consumer Korea and Anti-Corruption and Civil Rights Commission for 1000 and 1215 persons, respectively. Comprehensive results of these survey showed that 1.90% of people used 2 masks or more for 1 day, 27.40% of people used 1 mask for 1 day, 32.96% of people used 1 mask for 2 days, 21.22% of people used 1 mask for 3 days, and 16.52% of people used 1 mask for 4 days or more [32, 33]. From the results of these surveys, the average value of using one mask for 2.24 days can be obtained, and MC can be determined as 0.45 ea/day.

Table 2.

Parameters for estimation model of the generation amount of waste PPE

Generation source	Parameter	Value (Range)	References
Household (related Eq. 2)	Mask use cycle [MC]	0.45 (0.33–2.00)	[30, 31]
	Fraction of mask wearers [MF]	1.00	[25]
	Weight of face mask [WM]	4.64	Determined by this study
Test of COVID-19 (related Eqs. 4 and 5)	Scale of medical personnel [M]	1.06 (0.63–2.00)	[32, 33]
	PPE usage per medical personnel [PUtest]	1.00	[34, 35]
	Weight of 1 set of Level D PPE [PW]	355.26	Determined by this study
Treatment of COVID-19 (related Eq. 5)	Daily number of therapy of patient [Th]	8.00 (7.00–9.00)	[36]
	PPE usage per No. of therapy [PUth]	1.00	[34, 35]
	Weight of 1 set of Level D PPE [PW]	355.26	Determined by this study

MF was selected to be the value of 1.00 because it was mandatory to wear the face mask in daily life during the period from 2020 to 2021 [27]. In addition, WM was used by the average weight of the face mask, and was decided to be a value of 4.64 g/ea from Table 1. In Eq. 4, M was reviewed by the past experience in screening test for respiratory diseases and case study of the screening test for COVID-19 in Korea. And M was decided to be ranged from 0.62 to 2.00 medical personnel/people tested [34, 35]. Hence, M was determined to be the average value of 1.06 medical personnel/people tested finally. PU_test representing PPE used by medical personnel in COVID-19 test was assumed to be 1.00 set PPE/medical personnel, because it is to be replaced when PPE is contaminated or damaged according to the guidelines of KDCA [36, 37].

In Eq. 5, Th was obtained from a case study of treatment behavior in a hospital or community treatment center where a COVID-19 patient is isolated in Korea. Isolated COVID-19 patients received 7–9 times of COVID-19 therapy a day [38], and the average value of 8.00 therapy/patient was used in this study. In addition, the value of PU_th is decided to be 1.00 set PPE/therapy because PU should be replaced at every therapy of COVID-19 patients according to the guidelines of KDCA [34, 35]. For PW used as the same parameter in Eqs. (4) and (5), a value of 355.26 g/set was used from Table 1.

Amount of waste PPE generated from household

The monthly generation amount of waste PPE from household can be estimated by Eq. (2) using the parameters in Table 2 as shown in Fig. 3. The generation amount of waste PPE from household ranged from about 3000 to 3300 tons except in January 2020. The monthly amount of waste PPE in January 2020 is relatively small because the first confirmed case of COVID-19 in Korea was discovered on January 19, 2020 [39].

Fig. 3.

Estimated amount of waste PPE from households

Benson et al. considered the population, arbitrary percent of facemask acceptance rate, and the average daily face masks per capita for the evaluation of face mask generation, and they found that about 1008 million face masks per month were disposed in Korea [25]. Lee et al. calculated the amount of single-use face mask disposed in Korea considering the mask use cycle and population, and they predicted that about 130 face masks per person per year would be disposed [26]. It can be estimated that about 561 million of single-use masks per month are disposed in Korea when it is converted into a monthly usage by considering the population of 51 million.

However, the number of face masks generated per month was calculated to be about 694 million using the estimation model in this study. The difference in the number of face masks generated per month came from the assumption of the average daily face masks per capita in the study of Benson et al. and Lee et al. [25, 26]. Using the number of face masks generated per month in this study, the estimated amount of waste PPE from household can be converted to be about 3218 tons per month. Therefore, it may be a reasonable level in terms of the estimated amount of waste PPE from household as shown in Fig. 3.

Amount of waste PPE generated from test and treatment of COVID-19

The isolated medical waste in Korea was defined by all waste generated in the process of treating patients quarantined by an infectious disease [40]. Waste generated from test and treatment of COVID-19 is classified as an isolated medical waste in Korea, and the isolated medical waste related to COVID-19 was managed by a strict control procedure unlike the management of the isolated medical waste in normal circumstances. According to the waste statistics system in Korea, however, the isolated medical waste is not further subdivided for special infectious diseases and the isolated medical waste related to COVID-19 is involved into the isolated medical waste. In particular, the amount of isolated medical waste related to COVID-19 in 2020 was separately counted by the Ministry of Environment (MoE) in Korea [41]. Hence, the amount of isolated medical waste related to COVID-19 in 2020 can be expressed by a mixture of waste PPE and waste materials generated during the test and treatment of COVID-19 without considering waste materials caused by other infectious diseases. MoE in Korea reported the observed amount of isolated medical waste related to COVID-19 which was a value for waste PPE and waste materials caused by test and treatment of COVID-19. Based on the observed amount of isolated medical waste related to COVID-19, it can examine the reliability of the estimated amount of waste PPE calculated by Eq. (3).

To evaluate the reliability of the estimation model, the method using a coefficient of determination that can be measured by the difference between the observed value and the estimated value with slope of 1.0 generally has been used. The coefficient of determination is a scale between 0.0 and 1.0, and the closer to 1.0, the more reliable the result [42].

The amount of waste PPE generated from test and treatment of COVID-19 was estimated by Eqs. 3–5, and the observed amount of isolated medical waste related to COVID-19 in Korea can be compared with the estimated amount of isolated medical waste related to COVID-19 to represent the coefficient of determinations as shown in Fig. 4.

Fig. 4.

Relationship between the estimated and observed amount

In Fig. 4, the coefficient of determination was evaluated to be 0.8971. Therefore, it can be found that there was a meaningful relationship between the estimated amount and the observed amount with ensuring high reliability.

In this study, the estimation model for generation amount of waste PPE from test and treatment of COVID-19 is focused on waste PPE in the isolated medical waste related to COVID-19. Since the direct measurement is limited due to the possibility of transmission of infection in the actual field, there is a difference between the observed amount of isolated medical waste related to COVID-19 and the estimated amount of waste PPE from test and treatment of COVID-19 due to substances other than waste PPE. In Fig. 4, the intercept from relationship between the estimated amount and observed amount can be explained by the difference between waste PPE and other materials in the isolated medical waste related to COVID-19.

Figure 5 shows the amount of waste PPE generated monthly from test and treatment of COVID-19 estimated from 2020 to 2021. In 2020, the estimated generation amounts of waste PPE from test and treatment of COVID-19 in both March and December appeared relatively high to be about 650 tons and about 1,500 tons, respectively. Since the spread of COVID-19 in Korea increased during March, the government operated a strong social distancing system from March to reduce the infection of COVID-19 [43]. From April to November 2020, hence, the spread of COVID-19 was relatively reduced so that the generation amount of waste PPE from test and treatment of COVID-19 was also decreased from about 210 to 470 tons, respectively. From January to July in 2021, the generation amount of waste PPE from test and treatment of COVID-19 was increased from about 1090 to 1800 tons. During this period, confirmed cases of COVID-19 remained at about 400–640 per day, and the spread of COVID-19 was similar to the case in December 2020 [39, 44]. From August 2021, the number of confirmed cases of COVID-19 was increased to reach nearly 2000 per day, and about 6000 confirmed cases were reported per day in December [44, 45]. Accordingly, waste PPE generation from test and treatment of COVID-19 showed a tendency to increase dramatically from about 2800 tons in August to about 14,500 tons in December in 2021.

Fig. 5.

Estimation of the generation amount of waste PPE related to COVID-19 test and treatment

Amount of total waste PPE generated in case of Korea

The Korean government has announced that waste PPE used in household should be discharged by a waste bag in the Volume-based Waste Fee (VBWF) system. Waste PPE discharged by a waste bag in VBWF system should be incinerated or landfilled without recycling. Even though the main material of waste PPE is plastic, waste PPE is classified to be a waste textile in Korea. In the national statistics of waste generation in Korea, therefore, waste PPE discharged in a waste bag was counted as a waste textile. The waste textile discharged by the waste bag in VBWF system was increased from 333,647 tons in 2019 to 375,790 tons in 2020 [46]. The increased amount of waste textile generated from household after starting COVID-19 pandemic is 42,114 tons because the waste PPE related to COVID-19 from household was discharged by the waste bag. As shown in Table 3, the estimated amount of waste PPE generation in 2020 is 42,087 tons and 37,331 tons of waste PPE were generated from household. The increased amount of waste plastics before and after COVID-19 by VBWF system was different by about 11% from the estimated amount of waste PPE generation from household in 2020. Also, the estimated amount of waste PPE generation in 2021 is 79,396 tons and 39,047 tons of waste PPE were generated from household. The difference between the estimated amount of waste PPE generation from household and the increased amount of waste textile after COVID-19 is only about 7% in 2021. Therefore, the estimation model for generation amount of waste PPE from household in this study can be evaluated to have a meaningful reliability.

Table 3.

Cumulative generation amount of estimated waste PPE from 2020 to 2021 in Korea

Generation source	Unit	2020	2021	Total
Household	Ton	37,331.51	39,047.57	76,379.08
	%	88.70	49.18	62.87
Test and treatment of COVID-19
Test	Ton	1,522.75	14,131.82	15,654.57
	%	3.62	17.80	12.89
Treatment	Ton	3,232.93	26,216.89	29,449.82
	%	7.68	33.02	24.24
Sub-total	Ton	4,755.68	40,348.70	45,104.39
	%	11.30	50.82	37.13
Total	Ton	42,087.20	79,396.27	121,483.47
	%	100.00	100.00	100.00

It was estimated that more than 121 thousand tons of waste PPEs was generated for 2 years as shown in Table 3. The generated portion of waste PPE from household was about 63%, and that from the test and treatment of COVID-19 was about 37%. Among the waste PPE generated from the test and treatment, the waste PPE generated from the test was about 12.8% and that from treatment of COVID-19 was about 24.2%. Hence, the major source of waste PPE generation can be decided to be households and waste PPE generation from households should be controlled by the system of environmental sound management.

Korea is implementing a policy to reduce waste disposal, and is carrying out separating procedures to recover valuable resources from plastic bags mixed with various wastes. Plastic bags discharged from households are brought into the domestic waste separating facility, and manual separation is performed by workers. The manual separating process potentially increases the risk of infection to the workers. To prevent the infection of COVID-19 from waste PPE in household as a generation source, therefore, it is necessary to collect separately through the waste collection system. Also, waste PPE should not flow into the environmental media such as road, rivers, and ocean. In addition, the separately collected waste PPE should be incinerated, and it should be landfilled after disinfection if incineration is not available [24].

Recently, recycling methods for waste PPE generation from households, which have a relatively low probability of infection of COVID-19, have been proposed [47, 48]. Recycling of PPE requires manual separation process to recover the PPE from waste bags, which is a mixture of various wastes. Since complete destruction of COVID-19 virus remaining on the surface of face mask in the recycling processes of waste PPE may be difficult in reality, it may be possible to infect COVID-19 for workers in the recycling facilities indirectly.

The estimation model for generation amount of waste PPE proposed by this study was evaluated to have a relatively high reliability. Therefore, this estimation model can be shared to develop waste PPE management measures related to COVID-19 with the experience of determining parameters in the daily life and medical system in response to the ongoing COVID-19 situation in many countries. In addition, it will be used as a valuable experience in managing the occurrence and spread of unknown infectious diseases and related wastes in the future.

Conclusion

The estimation model of amount of waste PPE generated related to COVID-19 was proposed by a quantitative forecasting technique to apply to a case study of COVID-19 in Korea. The estimation model of generation amount of waste PPE related to COVID-19 was applied to two sources of generation such as household, and test and treatment of COVID-19 in medical practices.

In the estimation model of generation amount of waste PPE from household, parameters such as population, mask use cycle, and weight of face mask were considered. The estimation model of waste PPE generation from test and treatment of COVID-19 consists of parameters derived from confirmed cases, released cases from quarantine, and medical practices in response to COVID-19 including the number of therapies.

In Korea, generation amount of waste PPE from household was estimated to be 37,000 tons in 2020 and 39,000 tons in 2021, respectively. It shows a difference of about 7 ~ 11% in the increased amount of waste textile from household between the estimation result and the real generation data due to the spread of COVID-19.

The amount of waste PPE from test and treatment of COVID-19 was estimated to be about 4700 tons in 2020 and about 40,000 tons in 2021, respectively. In particular, the estimated amount through the estimation model for waste PPE generation from test and treatment of COVID-19 has a high coefficient of determination compared with the observed amount.

As a result of using this estimation model, it was estimated that about 121 thousand tons of waste PPE were generated in Korea for 2 years after the spread of COVID-19 in 2020. Waste PPE generated from household accounted for about 63%, and that generated from test and treatment accounted for about 37%. Since waste PPE may indirectly cause infection of COVID-19 to workers in waste collection or treatment facilities, waste PPE related to COVID-19 or other infectious diseases should be separately collected and treated eventually by incineration or landfill after sterilizing.