Personal Protective Equipment as a Potential Source of Phthalate Exposure during the COVID-19 Pandemic

Abstract

Personal protective equipment (PPE)—especially face masks, face shields, and gloves—was used to minimize the spread of COVID-19. PPE is primarily made of plastic materials with various plastic additives, such as phthalate plasticizers. Phthalates are linked with various adverse health effects. Therefore, this study investigated the amounts of six commonly used phthalates (DBP, BBP, DEHP, DnOP, DINP, and DIDP) in different types of PPE samples collected during the pandemic. Gas chromatography–mass spectrometry (GC–MS) was used to detect six selected phthalates and other organic chemicals in PPE samples. The quality of data was ensured using certified reference materials, internal standards, procedural blanks, and replicate analyses. The total phthalate content found in face shields and face masks was in the range of 0.29 µg/g to 942.60 µg/g, with DBP, DEHP, and DINP detected most frequently. A health risk assessment concluded that the determined levels were not expected to pose adverse health effects on the wearer. However, the findings of this study suggest that chronic daily intakes of phthalates from two vinyl glove samples with phthalate content exceeding 11% and 14% (w/w) of the glove’s weight may potentially increase the risk of cancer in humans. In addition to the target phthalates, flame retardants and other plasticizers (e.g., organophosphates and dioctyl isophthalate) were tentatively identified in various PPE samples.

1. Introduction

The coronavirus disease, COVID-19, was declared a pandemic by the World Health Organization (WHO) in March 2020 [1]. This deadly infectious disease is caused by severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) [2]. More than 627 million confirmed cases and more than 6.5 million deaths were reported globally by 30 October 2022 [3]. This pandemic has significantly changed human lifestyle worldwide. Many public health strategies have been used internationally to minimize the spread of COVID-19 and, consequently, to save lives. Of them, the most essential strategies were staying at home (lockdown), avoiding gatherings and close-crowded areas, practicing social distancing, restricting travel, disinfecting surfaces, and using personal protective equipment (PPE)—especially face masks, face shields, gloves, and hand sanitizers [4,5,6]. These requirements led to a sudden global increase in the production and consumption of PPE. Driven by a surge in the use of PPE by the general public, the global demand for PPE such as face masks, face shields, gloves, gowns, and cleaning equipment was estimated to peak at 340 to 420 billion units in 2021 [7]. The demand is expected to remain significant for the foreseeable future, particularly, as new variants of the virus or new viruses emerge [8]. Exposure to pollutants related to PPE (e.g., microplastics, plastic additives, and viruses) may occur through direct and indirect pathways. Direct exposure occurs through the inhalation of PPE microfibers and additives during PPE use, while indirect pathways include exposure to released microplastics and additives over extended durations, as the PPE undergoes different processes [9].

Most PPE used during the COVID-19 pandemic, including disposable procedure masks, N95 masks, reusable cloth masks, and face shields, is produced from plastic polymers such as polypropylene, polystyrene, polycarbonate, polyethylene, or polyester [10].

Air-filtering masks are used to protect wearers by preventing the transmission of respiratory infections caused by inhaling airborne pathogens during the pandemic and by preventing the risks of inhaling particulate matter from polluted air [11]. Two main types of air-filtering masks commonly used during the COVID-19 pandemic were procedure (or surgical) masks and N95 respirators. A procedure (or surgical) mask is designed to block large drops, sprays, or spatter containing pathogens from entering the respiratory system through the mouth and nose. However, N95 respirators can provide a more effective shield against airborne diseases by protecting against >95% of the particles [12].

Face shields were also among the types of PPE recommended for use during the COVID-19 pandemic. Face shields are manufactured in various forms, but all of them provide a transparent, impact- and moisture-resistant plastic barrier that covers the face [13,14]. Most face shields include three main components: a visor, frame, and suspension system. These parts are commonly made of polymers such as polycarbonate, propionate, acetate, polyvinyl chloride, and polyethylene terephthalate glycol [15]. Face shields are used to protect the facial area and associated mucous membranes (eyes, nose, and mouth) from splashes, spraying, and spattering of body fluids [15].

Disposable glove use was recommended by many health authorities around the world during the early stages of the COVID-19 pandemic, particularly for frontline workers [16]. Disposable gloves were also required for food handling to maintain food safety according to regulatory food hygiene requirements during the pandemic and to protect food industry workers from potential exposures [17,18]. Usually, disposable plastic gloves are made of polyethylene, latex (natural rubber), vinyl, or nitrile plastics [18,19]. Due to the COVID-19 pandemic, the global production of disposable gloves was estimated to reach 420 billion pieces in 2021 [18].

Mostly, PPE is manufactured from plastic materials, so various additives—including plasticizers, flame retardants, antioxidants, and stabilizers—are incorporated into PPE during manufacturing [18,20]. Phthalates are a group of common plasticizers widely used in the plastic industry. The content of phthalates in some plastic products can reach up to 50% by weight. Phthalate plasticizers are mixed with plastic materials during formulation, but these compounds do not form chemical bonds with the other materials. Therefore, they can easily be released to the adjacent environment and contribute to elevating the level of exposure to humans [18,21].

Phthalate plasticizers are known for their disruption effects to the endocrine system. A number of phthalate compounds have officially been classified by various authorities, e.g., the European Union, as endocrine disruptors [22]. Chronic exposure to these compounds is associated with adverse effects on the endocrine system, in addition to negative long-term impacts on the success of pregnancy, child growth and development, and reproductive systems in both young children and adolescents [23]. Some studies have also linked exposure to phthalates with obesity problems (metabolic syndrome), cancer, and increased tumor activity [24]. For example, di(2-ethylhexyl) phthalate (DEHP) has been classified as “possibly carcinogenic to humans” [25]. Currently, many countries are restricting or regulating the use of phthalates because of their adverse health and environmental effects [23].

Phthalates are ubiquitous compounds and are considered among those classified as everywhere chemicals. Exposure to phthalates can occur mainly via ingestion, inhalation, dermal contact, and parenteral administration [26]. COVID-19 pandemic prevention strategies are thought to increase individuals’ exposures to toxic chemicals such as phthalates. Individuals spent more time indoors, which could have led to an increased exposure to phthalates. In addition, the prolonged use of PPE such as face masks, face shields, and gloves may increase the levels of exposure to the leachable, semivolatile compounds such as phthalates found in these products. Therefore, the aim of this study is to investigate the occurrence and quantify the concentrations of six commonly used phthalates (DBP, BBP, DEHP, DnOP, DINP, and DIDP) in samples from different types of PPE (face masks, face shields, and disposable gloves) collected during the early stage of the COVID-19 pandemic. In addition, the samples were qualitatively evaluated to identify the presence of any other harmful organic chemicals that may have been used during the manufacturing process.

2. Materials and Methods

2.1. Materials and Reagents

The organic solvents used in this study were all HPLC grade and purchased from Sigma-Aldrich, Honeywell, or Fisher Chemical. A standard stock solution of the six phthalate analytes (DBP, BBP, DEHP, DnOP, DINP, and DIDP) in isooctane at a concentration of 1000 µg/mL was obtained from SPEX CertiPrep (Metuchen, NJ, USA) and used in all GC–MS analyses. Calibration curves were generated using standard solutions in the range of 0.20–6.0 µg/mL prepared by dilution from the stock solution. Benzyl benzoate was obtained from Aldrich and used as an internal standard. A certified reference material (CRM) of polyvinyl chloride (PVC) containing the six phthalate analytes (CRM-PVC001) was purchased from SPEX CertiPrep (Metuchen, USA) and used for quality assurance.

2.2. Sample Collection and Preparation

In total, 51 samples of various types of PPE were collected from local shops, pharmacies, and online sources in Saudi Arabia from August to September 2020. A total of 33 face masks and 2 face shields were obtained from different countries of origin, including China, the USA, India, Bangladesh, Saudi Arabia, and Jordan. The face mask samples included 19 disposable procedure masks, 10 reusable cloth masks, 1 N95 mask, 2 KN95 disposable masks, and 1 reusable sponge mask. Some of the collected face masks were designed for children, but the majority were designed for adults. Glove samples included 16 brands from different countries of origin, including Malaysia, China, and Thailand. All glove samples were disposable and made from different plastic materials, namely, latex, nitrile, polyethylene, or polyvinyl chloride.

All the collected PPE samples were kept in their original packaging at room temperature until analysis. Phthalates were extracted from the samples as previously described [21] with slight modifications. In brief, PPE samples were cut into small pieces of approximately 2 mm × 2 mm in size using clean metallic scissors, and the cut pieces were thoroughly mixed. A sample of 0.5 ± 0.01 g was weighed and placed in a 40 mL sealable glass vial. The phthalates in each sample were extracted by 10 mL of dichloromethane (DCM) in an ultrasonic bath for 30 minutes at room temperature; then, the sample was kept in DCM overnight. Soluble polymers were precipitated by adding 10 mL of cyclohexane to the extract. Approximately 3 mL of the DCM/cyclohexane solution was filtered using a 0.2 µm PTFE syringe filter. An aliquot of the filtered solution was mixed with the internal standard in a GC vial and used for the GC–MS analysis.

2.3. The GC–MS Instrument and Procedure

The GC–MS instrument used for the analysis of the phthalates in the PPE extracts was from Shimadzu Corporation (Kyoto, Japan), model QP2010 Ultra. The NIST 11 Mass Spectral Library was used for the tentative identification of unknown compounds in the extracts. The GC–MS operating procedure and conditions followed the method previously described [21]. The fast automated scan/SIM technique mode, which acquires scan and SIM data simultaneously for each injection, was used during the MS analysis to provide quantitative data for the six targeted phthalate analytes, in addition to qualitative data for the identification of other unknown compounds in the samples. Representative GC–MS chromatograms are shown in Figures S1–S3.

2.4. Quality Assurance and Quality Control

Only glass containers and tools were used during the sample preparation, and they were cleaned well and rinsed with acetone and DCM before use. The use of laboratory gloves was avoided during sample preparation to prevent any possible contamination. All solvents used in this study were checked for contamination of phthalates before use.

To ensure the quality of measurements, certified reference materials, internal standards, procedural blanks, and replicate analyses were used. Procedural blanks were analyzed with each batch to assess any contamination or interference that could have been introduced during any part of the measurement procedure. Most laboratory procedural blanks showed no contamination with any of the target analytes. Only a few blanks contained trace levels of phthalate analytes, mostly DBP and DEHP, which were just above the detection limit. In this case, the levels detected in the blanks were subtracted from the concentrations in the samples analyzed in the same batch. Calibration curves were linear in the range from 0.2 to 6.0 µg/mL, with correlation coefficients > 0.99. The limit of detection (LOD) and limit of quantification (LOQ) were estimated using the standard deviation (SD) of 21 replicate injections of the lowest calibrator (0.2 µg/mL). The LOD was determined as 3 × SD, and the LOQ was determined as 10 × SD [27,28]. The LOD values for the six analytes were in the range of 0.4–2.1 ng/mL, while the LOQ values ranged from 1.2 to 7.0 ng/mL. These LOQ values corresponded to 0.06 to 0.32 µg/g of sample.

A CRM (CRM-PVC001) was used for recovery evaluation of the analytical method and for quality assurance with each batch of samples analyzed. Five replicate analyses of the CRM were used to evaluate the recovery. The recovered values were compared with the certified values to obtain the recovery percentage. The recovery values of the six target phthalates were in the range of 52.0% ± 3.7% to 97.1% ± 5.1%. PPE samples were analyzed in triplicates, along with three CRM replicates for each batch.

2.5. Health Risk Assessment

The health risk of exposure to the phthalate group of interest in the PPE samples in adults was assessed. The chronic daily intake (CDI) through inhalation and dermal pathways for face masks, inhalation pathways for face shields, and dermal pathways for gloves were considered. The CDI through inhalation and dermal pathways was calculated using Equations (1) and (2), respectively [29]:

$${\mathrm{C}\mathrm{D}\mathrm{I}}_{\mathrm{i}\mathrm{n}\mathrm{h}\mathrm{a}\mathrm{l}\mathrm{a}\mathrm{t}\mathrm{i}\mathrm{o}\mathrm{n}}=\frac{{\mathrm{C}}_{\mathrm{i}}\times \mathrm{I}\mathrm{n}\mathrm{h}\mathrm{R}\times \mathrm{E}\mathrm{x}\mathrm{F}\mathrm{r}\times \mathrm{E}\mathrm{D}}{\mathrm{P}\mathrm{E}\mathrm{F}\times \mathrm{B}\mathrm{W}\times \mathrm{A}\mathrm{T}}$$

(1)

$${\mathrm{C}\mathrm{D}\mathrm{I}}_{\mathrm{D}\mathrm{e}\mathrm{r}\mathrm{m}\mathrm{a}\mathrm{l}}=\left(\frac{{\mathrm{C}}_{\mathrm{i}}\times \mathrm{S}\mathrm{A}\times \mathrm{A}\mathrm{F}\times \mathrm{D}\mathrm{A}\mathrm{F}\times \mathrm{E}\mathrm{x}\mathrm{F}\mathrm{r}\times \mathrm{E}\mathrm{D}}{\mathrm{B}\mathrm{W}\times \mathrm{A}\mathrm{T}}\right)\times \mathrm{C}\mathrm{F}$$

(2)

where C_i is the mean concentration (µg/g) of a phthalate compound in a PPE sample, InhR is the inhalation rate (20 mg/cm²), ExFr is the exposure frequency (350 days), ED is the exposure duration (24 years), PEF is the particle emission factor (1.36 × 10⁹ m³/kg), BW is the body weight (70 kg), AT is the averaging time (365 × 24 days), SA is the surface area of the skin that comes in contact with a PPE sample (445.5 and 840 cm²/event for face masks and gloves, respectively), AF is the skin adherence factor (0.07 mg/cm), DAF is the dermal absorption factor (0.001, unitless), and CF is the conversion factor (1 × 10⁻⁶ kg/mg). The levels of these parameters were recommended by the USEPA [29] and the United States Department of Energy [30]. Then, the hazard quotient (HQ) for noncarcinogenic risk was determined using Equation (3):

$$\mathrm{H}\mathrm{Q}=\frac{\mathrm{C}\mathrm{D}\mathrm{I}}{\mathrm{R}\mathrm{f}\mathrm{D}}$$

(3)

where RfD is the reference dose that characterizes the health risk of noncarcinogenic adverse effects due to exposure to a phthalate compound. The RfD values of DBP, BBP, DEHP, DnOP, and DINP are 100, 200, 20, 40, and 37, respectively [31,32,33,34,35]. Notably, no RfD value for DIDP was found in the literature.

For the noncarcinogenic risk assessment, the hazard index (HI) was determined using Equation (4):

$$\mathrm{H}\mathrm{I}=\sum \mathrm{H}\mathrm{Q}={\mathrm{H}\mathrm{Q}}_{\mathrm{i}\mathrm{n}\mathrm{h}\mathrm{a}\mathrm{l}\mathrm{a}\mathrm{t}\mathrm{i}\mathrm{o}\mathrm{n}}+{\mathrm{H}\mathrm{Q}}_{\mathrm{D}\mathrm{e}\mathrm{r}\mathrm{m}\mathrm{a}\mathrm{l}}$$

(4)

The carcinogenic risk (CR) factor was calculated using Equation (5):

$$\mathrm{C}\mathrm{R}=({\mathrm{C}\mathrm{D}\mathrm{I}}_{\mathrm{I}\mathrm{n}\mathrm{h}\mathrm{a}\mathrm{l}\mathrm{a}\mathrm{t}\mathrm{i}\mathrm{o}\mathrm{n}}+{\mathrm{C}\mathrm{D}\mathrm{I}}_{\mathrm{D}\mathrm{e}\mathrm{r}\mathrm{m}\mathrm{a}\mathrm{l}})\times \mathrm{C}\mathrm{S}\mathrm{F}$$

(5)

where CSF is the cancer slope factor of an individual phthalate compound. The CSF values of DBP, BBP, DEHP, DnOP, and DINP are 0.142, 0.0019, 0.014, 0.036, and 0.06, respectively [31,32,33,34,35,36]. Notably, no CSF value for DIDP was found in the literature.

3. Results

3.1. Phthalate Concentrations in Face Masks and Face Shields

The levels of the six target phthalates (DBP, BBP, DEHP, DnOP, DINP, and DIDP) in the face masks and face shields tested in this study are shown in

Table 1. Levels of the target phthalates (DBP, BBP, DEHP, DnOP, DINP, and DIDP) in face masks and face shields along with product descriptions.

Sample Code	Product Data: Description/Country of Origin/Materials	Phthalate Content (µg/g; Mean (SD); n = 3)						Total Phthalate Content * (µg/g)	Other Plasticizers/ Additives **
		DBP	BBP	DEHP	DnOP	DINP	DIDP
FS1	Face shield/China/NA	0.17 (0.02)	<LOQ ***	0.12 (0.01)	<LOQ	<LOQ	<LOQ	0.29	Monoprop-2-ynyl phthalate
FS2	Face shield/China/NA	0.40 (0.13)	<LOQ	0.14 (0.05)	<LOQ	<LOQ	<LOQ	0.54	Monoprop-2-ynyl phthalate
MS1	Kid’s disposable medical procedure mask/Saudi Arabia/NA	0.94 (0.67)	<LOQ	0.39 (0.29)	<LOQ	<LOQ	<LOQ	1.33	-
MS2	Kid’s disposable non-medical procedure mask/China/Non-woven fabric; melt-blown fabric	1.00 (0.23)	<LOQ	1.55 (0.48)	<LOQ	8.14 (2.49)	<LOQ	10.69	Monoprop-2-ynyl phthalate
MS3	Kid’s disposable non-medical procedure mask/Saudi Arabia/NA	1.27 (0.12)	<LOQ	1.54 (0.21)	<LOQ	2.25 (0.37)	<LOQ	5.06	Monoprop-2-ynyl phthalate
MS4	Kid’s reusable cloth mask/China/Cotton	0.20 (0.04)	<LOQ	0.28 (0.06)	<LOQ	503 (109)	<LOQ	503.48	Monoprop-2-ynyl phthalate
MS5	Kid’s reusable cloth mask/China/NA	1.21 (0.10)	<LOQ	0.93 (0.05)	<LOQ	<LOQ	<LOQ	2.14	Monoprop-2-ynyl phthalate
MS6	Disposable non-medical procedure mask/China/Non-woven fabric; melt spray filter fabric	0.62 (0.09)	<LOQ	3.76 (1.92)	<LOQ	<LOQ	<LOQ	4.38	-
MS7	Disposable non-medical procedure mask/China/Non-woven fabric; melt-blown fabric	0.71 (0.19)	<LOQ	3.13 (1.24)	<LOQ	<LOQ	<LOQ	3.84	-
MS8	Disposable non-medical procedure mask/China/Non-woven fabric; melt-blown fabric	0.79 (0.04)	<LOQ	1.01 (0.19)	<LOQ	<LOQ	<LOQ	1.80	-
MS9	Disposable non-medical procedure mask/China/Non-woven fabric; melt-blown fabric	4.31 (0.10)	<LOQ	4.95 (0.15)	<LOQ	<LOQ	<LOQ	9.26	-
MS10	Disposable non-medical procedure mask/China/Non-woven fabric; melt-blown fabric	0.96 (0.17)	<LOQ	0.88 (0.14)	<LOQ	<LOQ	<LOQ	1.84	-
MS11	Disposable non-medical procedure mask/China/Non-woven fabric; melt-blown cloth	0.62 (0.05)	<LOQ	1.87 (0.16)	<LOQ	<LOQ	<LOQ	2.49	-
MS12	Disposable non-medical procedure mask/China/Non-woven fabric; melt-blown fabric	0.50 (0.24)	<LOQ	0.52 (0.41)	<LOQ	<LOQ	<LOQ	1.02	-
MS13	Disposable non-medical procedure mask/China/NA	0.67 (0.15)	<LOQ	0.50 (0.33)	<LOQ	<LOQ	<LOQ	1.17	-
MS14	Disposable non-medical procedure mask/China/NA	3.34 (0.52)	<LOQ	1.33 (0.14)	<LOQ	<LOQ	<LOQ	4.67	-
MS15	Disposable non-medical procedure mask/China/NA	0.98 (0.23)	<LOQ	2.51 (0.07)	<LOQ	<LOQ	<LOQ	3.49	-
MS16	Disposable non-medical procedure mask/China/NA	0.20 (0.12)	<LOQ	0.88 (0.33)	<LOQ	<LOQ	<LOQ	1.08	-
MS17	Disposable non-medical procedure mask/China/NA	1.72 (0.32)	<LOQ	1.26 (0.07)	<LOQ	<LOQ	<LOQ	2.98	-
MS18	Disposable non-medical procedure mask/China/NA	0.56 (0.13)	<LOQ	0.97 (0.04)	<LOQ	<LOQ	<LOQ	1.53	-
MS19	Disposable non-medical procedure mask/China/NA	2.48 (0.11)	1.15 (0.05)	1.06 (0.03)	<LOQ	<LOQ	<LOQ	4.69	-
MS20	Disposable non-medical procedure mask/China/NA	7.32 (0.60)	<LOQ	1.68 (0.22)	<LOQ	<LOQ	<LOQ	9.00	-
MS21	Disposable non-medical procedure mask/India/NA	5.75 (1.18)	2.08 (0.14)	3.04 (0.69)	<LOQ	<LOQ	<LOQ	10.87	-
MS22	KN95 disposable non-medical mask with valve/China/Non-woven; melt-blown; hot air cotton	2.55 (0.54)	0.64 (0.02)	263 (85.8)	<LOQ	<LOQ	<LOQ	266.19	-
MS23	KN95 disposable non-medical mask/China/Non-woven; melt-blown; hot air cotton	1.26 (0.40)	<LOQ	4.92 (1.22)	<LOQ	<LOQ	<LOQ	6.18	-
MS24	N95 disposable mask/USA/NA	2.87 (0.33)	<LOQ	0.59 (0.02)	<LOQ	<LOQ	<LOQ	3.46	-
MS25	Reusable cloth mask/Bangladesh/Polyester	5.70 (0.61)	<LOQ	2.32 (0.04)	<LOQ	<LOQ	<LOQ	8.02	Palmitic acid, Oleic acid, Stearic acid
MS26	Reusable cloth mask/Jordan/NA	0.87 (0.26)	<LOQ	91.3 (111)	<LOQ	<LOQ	<LOQ	92.17	Triphenyl phosphate, Cresyl diphenyl phosphate, Phenyl di(p-tolyl) phosphate, Monoprop-2-ynyl phthalate
MS27	Reusable cloth mask/China/Fine fiber sponge	0.36 (0.14)	<LOQ	0.24 (0.19)	<LOQ	<LOQ	<LOQ	0.60	Bis(2-butoxyethyl) adipate
MS28	Reusable cloth mask/China/NA	0.64 (0.25)	<LOQ	0.94 (0.51)	<LOQ	<LOQ	<LOQ	1.58	Monoprop-2-ynyl phthalate
MS29	Reusable cloth mask/India/NA	0.67 (0.25)	<LOQ	3.07 (2.29)	<LOQ	<LOQ	<LOQ	3.74	Monoprop-2-ynyl phthalate
MS30	Reusable cloth mask/NA/NA	0.60 (0.04)	<LOQ	1.05 (0.15)	<LOQ	<LOQ	<LOQ	1.65	Monoprop-2-ynyl phthalate
MS31	Reusable cloth mask/NA/NA	4.60 (0.83)	<LOQ	938 (826)	<LOQ	<LOQ	<LOQ	942.60	Monoprop-2-ynyl phthalate
MS32	Reusable cloth mask/Saudi Arabia/NA	0.71 (0.08)	<LOQ	2.48 (0.13)	<LOQ	<LOQ	<LOQ	3.19	Monoprop-2-ynyl phthalate
MS33	Reusable sponge mask/China/Polyurethane sponge; polypropylene	1.29 (0.14)	<LOQ	7.29 (0.45)	<LOQ	<LOQ	<LOQ	8.58	Decyl decanoate, Bis(2-butoxyethyl) adipate

* Total phthalate content is the sum of the concentrations of the six target analytes in a sample. ** Compounds with large peaks in the chromatogram, identified qualitatively by comparing their MS spectra to those in NIST library. *** <LOQ: concentration level was lower than the limit of quantification or the analyte was not detected.

, along with product descriptions. Phthalate concentration and distribution in the different types of face masks and in face shields are shown in Figure 1.

The results in Table 1 and Figure 1 show that all 33 tested face masks and the 2 face shields contained one or more of the six target phthalates at levels above the LOQ. DBP and DEHP were found in all face mask and face shield samples. BPB and DINP were present in only three face mask samples. DnOP and DIDP were not detected in any of the face masks or face shields tested.

The levels of DBP and DEHP ranged from 0.17 µg/g ± 0.02 µg/g to 7.32 µg/g ± 0.60 µg/g and from 0.12 µg/g ± 0.01 µg/g to 938 µg/g ± 826 µg/g, respectively. The BBP and DINP levels ranged from 0.64 µg/g ± 0.02 µg/g to 2.08 µg/g ± 0.14 µg/g and from 2.25 µg/g ± 0.37 µg/g to 503 µg/g ± 109 µg/g, respectively.

Total phthalate contents, i.e., the sum of the concentrations of the six target analytes in a sample, ranged from 0.29 µg/g to 942.60 µg/g in the tested face masks and face shields. The two face shields contained lower levels of phthalates than the face masks, with total phthalate contents ranging from 0.29 µg/g to 0.54 µg/g. In general, disposable masks contained lower phthalate content in the range of 1.02–10.87 µg/g than reusable cloth masks, which showed the highest levels, reaching 942.60 µg/g. The KN95 mask with a plastic exhalation valve was the only disposable mask that had a total phthalate content higher than the range found in the disposable masks. DBP, BBP, and DEHP were present in this mask at the levels of 2.55 µg/g ± 0.54 µg/g, 0.64 µg/g ± 0.02 µg/g, and 263 µg/g ± 85.8 µg/g, respectively. These higher levels seem to result from the manufacturing materials used in the plastic exhalation valve because another KN95 sample from the same manufacturer with no valve was tested, and it showed a lower phthalate content (1.26 µg/g ± 0.40 µg/g, <LOQ, and 4.92 µg/g ± 1.22 µg/g for DBP, BBP, and DEHP, respectively).

3.2. Phthalate Concentrations in Disposable Plastic Gloves

The levels of the target phthalates in the glove samples, along with product descriptions, are presented in

Table 2. Levels of the target phthalates (DBP, BBP, DEHP, DnOP, DINP, and DIDP) in disposable plastic gloves along with product descriptions.

Sample Code	Product Data: Description/Country of Origin	Phthalate Content (µg/g; Mean (SD); n = 3)						Total Phthalate Content * (µg/g)	Other Plasticizers/Additives **
		DBP	BBP	DEHP	DnOP	DINP	DIDP
GS1	Disposable latex gloves/China	<LOQ ***	<LOQ	<LOQ	<LOQ	<LOQ	<LOQ	<LOQ	-
GS2	Disposable latex gloves/Malaysia	1.38 (0.16)	<LOQ	0.45 (0.09)	<LOQ	<LOQ	<LOQ	1.83	Linoleic acid; Mix of hydrocarbons
GS3	Disposable latex gloves/Malaysia	2.52 (0.22)	<LOQ	2.60 (0.10)	<LOQ	<LOQ	<LOQ	5.12	Linoleic acid; Mix of hydrocarbons
GS4	Disposable nitrile gloves/Malaysia	0.09 (0.03)	<LOQ	0.84 (0.06)	<LOQ	<LOQ	<LOQ	0.93	Mix of hydrocarbons
GS5	Disposable nitrile gloves/Thailand	0.17 (0.03)	<LOQ	0.29 (0.20)	<LOQ	<LOQ	<LOQ	0.46	Mix of hydrocarbons
GS6	Disposable nitrile gloves/Malaysia	0.90 (0.18)	<LOQ	0.78 (0.08)	<LOQ	<LOQ	<LOQ	1.68	-
GS7	Disposable polyethylene gloves/China	0.85 (0.05)	<LOQ	0.74 (0.14)	<LOQ	<LOQ	<LOQ	1.59	Mix of hydrocarbons
GS8	Disposable polyethylene gloves/China	0.92 (0.14)	<LOQ	1.04 (0.16)	<LOQ	<LOQ	<LOQ	1.96	Palmitic acid; Stearic acid; Mix of hydrocarbons
GS9	Disposable vinyl gloves/China	0.26 (0.05)	<LOQ	7.81 (0.54)	<LOQ	<LOQ	<LOQ	8.07	DOIP; Tributyl citrate
GS10	Disposable vinyl gloves/China	0.80 (0.22)	<LOQ	0.86 (0.21)	<LOQ	<LOQ	<LOQ	1.66	DOIP
GS11	Disposable vinyl gloves/China	0.47 (0.19)	<LOQ	1.72 (1.34)	<LOQ	<LOQ	<LOQ	2.19	DOIP
GS12	Disposable vinyl gloves/China	1.48 (0.39)	<LOQ	2.45 (0.11)	<LOQ	<LOQ	<LOQ	3.93	DOIP
GS13	Disposable vinyl gloves/China	1.25 (0.22)	<LOQ	3.04 (0.14)	<LOQ	<LOQ	<LOQ	4.29	DOIP
GS14	Disposable vinyl gloves/China	0.35 (0.19)	<LOQ	2.38 (0.21)	<LOQ	<LOQ	<LOQ	2.73	DOIP
GS15	Disposable vinyl gloves/China	2.01 (0.48)	<LOQ	3.86 (1.90)	<LOQ	111,749 (15,179)	<LOQ	111,754	DOIP; Tributyl citrate
GS16	Disposable vinyl gloves/China	4.83 (0.21)	<LOQ	179 (9.1)	<LOQ	141,531 (12,434)	<LOQ	141,714	-

* Total phthalate content is the sum of the concentrations of the six target analytes in a sample. ** Compounds with large peaks in the chromatogram, identified qualitatively by comparing their MS spectra to those in NIST library. *** <LOQ: concentration level was lower than the limit of quantification.

. The concentration and distribution of the six phthalate analytes in the different types of disposable glove samples are shown in Figure 2.

The results in Table 2 and Figure 2 show that only one glove sample had no quantifiable amounts of the target phthalates, while the other 15 samples contained amounts above the LOQ. In all the 16 samples, the analytes BBP, DnOP, and DIDP were not present in quantifiable amounts. In contrast, DBP and DEHP were present in all 15 samples at levels ranging from 0.09 µg/g ± 0.03 µg/g to 4.83 µg/g ± 0.21 µg/g and from 0.29 µg/g ± 0.20 µg/g to 179 µg/g ± 9.1 µg/g, respectively. Large concentrations of DINP were found in two PVC samples (GS15 and GS16), with levels of 111,749 µg/g ± 15,179 µg/g and 141,531 µg/g ± 12,434 µg/g, corresponding with 11.18% (w/w) and 14.15% (w/w), respectively. These two samples also showed the highest levels of DBP and DEHP among the tested samples. The total phthalate contents in the analyzed plastic gloves ranged from <LOQ to as high as 141,714 µg/g (14.17% w/w).

3.3. Identification of Other Plasticizers and Plastic Additives in PPE

The PPE samples tested in this study were analyzed qualitatively to identify any plasticizers other than the six target phthalates, in addition to other plastic additives that may pose a health risk to users. The last columns in Table 1 and Table 2 include the identified plastic additives found in the analyzed face masks, face shields, and gloves.

The major additives identified in face masks and face shields were plasticizers or flame retardants. A phthalate compound tentatively identified as monoprop-2-ynyl phthalate (CAS# 6139-61-3) was found in 36% of the face mask and face shield samples. No description was found in the literature about its function in plastic products. However, it is possibly used as an alternative to commonly regulated phthalate plasticizers.

Notably, all the analyzed disposable procedure masks were free from any major additives other than the detected target phthalates, except for two children’s disposable procedure masks that contained monoprop-2-ynyl phthalate. In contrast, all the cloth masks contained various types of plasticizers and other additives, such as flame retardants. The list of the detected additives includes monoprop-2-ynyl phthalate, palmitic acid, oleic acid, stearic acid, bis(2-butoxyethyl) adipate, and several others, as mentioned in Table 1. In total, three organophosphates, namely, triphenyl phosphate, cresyl diphenyl phosphate, and phenyl di(p-tolyl) phosphate, were detected in a reusable cloth face mask.

The last column in Table 2 shows the major additives identified in the analyzed disposable gloves. No phthalate plasticizers other than the target analytes were detected in them. However, phthalate alternatives were identified in most (81%) of the analyzed glove samples. The most frequently found alternative was dioctyl isophthalate (DOIP), which was found in all the vinyl gloves. Another non-phthalate plasticizer found in two vinyl glove samples, in addition to DOIP, was tributyl citrate (TBC). The major compounds identified in latex, nitrile, and polyethylene glove samples were mixtures of long-chain hydrocarbons and fatty acids such as palmitic acid, stearic acid, and linoleic acid.

3.4. Health Risk Assessment

The CDI and HQ of inhalation and dermal pathways of exposure to phthalate compounds from the face mask samples are shown in Tables S1–S4. The HIs of inhalation and dermal pathways of exposure to phthalate compounds from face mask samples are shown in Table S5. The HIs for DBP and DEHP ranged from 1.26 × 10⁻¹² to 4.60 × 10⁻¹¹ and from 7.54 × 10⁻¹² to 2.95 × 10⁻⁸, respectively. The maximum HIs of the quantifiable BBP and DINP are 1.31 × 10⁻¹⁰ and 5.36 × 10⁻⁹, respectively.

For the face shield samples, Tables S6 and S7 show that the maximum CDI and HQ of DBP are 8.058 × 10⁻¹¹ and 8.05 × 10⁻¹³, respectively, while the maximum CDI and HQ of DEHP are 2.82 × 10⁻¹¹ and 1.41 × 10⁻¹², respectively.

For the glove samples, Tables S8 and S9 show that the maximum CDIs of DBP, DEHP, and DINP are 3.89 × 10⁻⁹, 1.4 × 10⁻⁷, and 1.14 × 10⁻⁴, respectively, while the HQs of DBP, DEHP, and DINP are 3.89 × 10⁻¹¹, 7.21 × 10⁻⁹, and 1.93 × 10⁻⁶, respectively.

The CR factors of inhalation and dermal pathways of exposure to phthalate compounds from face mask samples are shown in Table S10. The maximum factors followed the descending order DINP > DBP > BBP > DEHP. In addition, Tables S11 and S12 show the CR factors of inhalation and dermal pathways of exposure to phthalate compounds from the face shield and glove samples.

4. Discussion

4.1. Phthalate Concentrations in Face Masks and Face Shields

All of the tested face masks and face shields in this study contained quantifiable levels of at least two of the six target phthalates. Reusable cloth masks showed a high total phthalate contents compared with disposable masks. Total phthalate contents were in the range of 0.60–942.60 µg/g. In total, three samples showed a high total phthalate content at the levels of 92.17 µg/g, 503.48 µg/g, and 942.60 µg/g. One of these masks was commercialized for children’s use; this mask contained a high level of phthalates, with a total content of 503.48 µg/g, and DINP was the main plasticizer in this mask at a level of 503 µg/g ± 109 µg/g. The other two masks were reusable masks for adults and contained DEHP as the main phthalate at the levels of 91.3 µg/g ± 111 µg/g and 938 µg/g ± 826 µg/g.

Cloth masks with the highest levels of phthalates contained thick plastisol prints on the outer layer of the mask as decoration or with the brand’s logo. The plastisol prints appeared to be the main source of the high phthalate content measured in these samples, particularly when noting the high SDs of the replicate measurements. Phthalates are a common constituent or contaminant of plastisol prints and represent a potential concern for textile manufacturers and retailers [37,38]. DBP, DEHP, and DINP were the major phthalates detected in plastisol-printed fabric sections from five T-shirts analyzed for phthalate content [38]. These three phthalates were also found in the reusable cloth masks with plastisol prints in this study. Although the plastisol prints were on the outer layer of the mask, it is likely that they still contributed to the increasing exposure to phthalates, as phthalate compounds are semivolatile and not firmly bound to the plastic polymers. Phthalate compounds can easily leach out and migrate to the other layers of the face mask, reaching the inhalation path of the wearer. In addition to being derived from the plastisol prints, phthalates could also be present in the fabric itself. Tang et al. [39] reported the prevalence of phthalates in preschool children’s clothing. Total phthalate contents in the range of 2.92–223 µg/g were found, with DEHP and DBP being among the most abundant phthalates. Infant cotton clothing was also reported to contain phthalates, with a total content in the range of 2.29–51.9 µg/g and with DEHP being the dominant phthalate [40].

A few recent studies [20,31,41,42] have reported the levels and profiles of phthalates in disposable face masks comparable to those found in this study. DBP and DEHP were the most frequently detected phthalates in face masks, with concentrations ranging from <LOD to 4.78 µg/g and from 0.037 µg/g to 36.7 µg/g, respectively [20,31]. The main source of the reported phthalates was concluded to be the raw materials used to manufacture the disposable face masks. However, other potential sources were also reported, such as contamination during the production process [31] and packaging [42].

The similarity in the results between the above studies might be related to the fact that the raw material composition and manufacturing process of face masks are similar around the world [31]. However, during the COVID-19 pandemic, there was a surge in the demand worldwide for commercial face masks, leading to a global shortage of face masks and associated raw materials. As a result, low-quality commercial masks appeared in the market, in addition to homemade masks produced from household materials such as cotton fabrics, clothing, and silk [43,44].

Notably, in addition to the six phthalates quantified in the face masks and face shields in this study, several other compounds were detected, including other phthalate plasticizers, flame retardants, and plastic additives, as discussed below.

4.2. Phthalate Concentrations in Disposable Plastic Gloves

The glove samples analyzed in this study included 16 brands from different countries of origin, including Malaysia, China, and Thailand. All glove samples were disposable and made of different plastic materials, namely, latex (three brands), nitrile (three brands), polyethylene two brands), and polyvinyl chloride (eight brands). In general, PVC gloves contained higher total phthalate contents (1.66–141,714 µg/g) than the other types of gloves, i.e., latex (<LOQ–5.12 µg/g), nitrile (0.93–1.68 µg/g), and polyethylene (1.59–1.96 µg/g). This finding was not surprising because phthalates are common plasticizers for PVC polymers [19]. High percentages of phthalates were present in PVC plastic products, including gloves that may contain levels higher than 30% of the glove’s weight [18,21,45,46,47]. In disposable plastic gloves, extremely variable contents of plasticizers were reported depending on the glove manufacturing materials. Plasticizers were found to be predominant in vinyl gloves at high levels ranging from 30% to 44% (w/w), while gloves made from other materials, such as latex, nitrile, and neoprene, contained a much lower total plasticizer content of less than 0.2% (w/w) [46].

High-molecular-weight phthalates, such as DEHP and DINP, are common additives in PVC polymers. DEHP and DINP were reported to comprise up to 4.10% (w/w) and 35.8% (w/w) of disposable vinyl gloves, respectively [46]. These levels are higher than the levels found in PVC gloves analyzed in this study, which reached a maximum of about 14% (w/w). However, this might be due to the use of phthalate-alternative plasticizers such as DOIP, which was identified in most PVC gloves. High-molecular-weight phthalates can migrate from plasticized PVC gloves to the surrounding environment, therefore, increasing human dermal exposure to these phthalates through direct skin contact [46]. In addition, when gloves plasticized with phthalates are used during food production, shipment, and storage, they can increase the exposure levels to phthalates through diet intake [32]. Furthermore, the massive amounts of disposable plastic gloves released into the environment during the COVID-19 pandemic can adversely affect humans and wildlife through the direct ingestion of plastic materials and through the ingestion of organic pollutants, such as phthalates, released into the environment [18].

Although most of the analyzed glove samples in this study contained relatively low levels of the target phthalates, other plasticizers, including a phthalate, were present at relatively high concentrations, as discussed below.

4.3. Identification of Other Plasticizers and Plastic Additives in PPE

The major plastic additives found in the PPE analyzed in this study were identified to explore any possible health risk. Only the major compounds with large peaks in the chromatogram were selected for tentative identification because most of the main additives are added to plastic products in the percentage range (% w/w) [48].

Notably, cloth masks contained various types of plasticizers and other additives, while disposable procedure masks were free from any major additives other than the detected target phthalates. Most of the identified additives were used as alternative plasticizers to regulated phthalates [49,50]. In total, three organophosphates were also detected in a reusable cloth face mask. This group of additives is widely used as plasticizers and flame retardants in various products [51,52,53,54]. A recent study reported a number of organophosphate compounds detected in face masks at levels reaching up to 27.7 μg/mask [54]. Organophosphates are emerging pollutants raising increasing concern due to their reported toxic effects, such as endocrine- and reproductive-function disruption [54]. However, the toxicological data on most alternative plasticizers are limited; therefore, it is challenging to draw solid conclusions regarding their safety [55,56].

Disposable plastic gloves contained no phthalate plasticizers other than the six target analytes. However, 81% of the analyzed glove samples were found to contain phthalate alternatives such as DOIP, which was found in all the vinyl gloves. DOIP belongs to the class of isophthalate ester plasticizers, which are considered to be among the next generation of phthalate alternatives [57]. Usually, non-phthalate plasticizers are declared by manufacturers to be safer alternatives to phthalates and to have no substance-related toxicity. However, increasing evidence is showing that many non-phthalate plasticizers exhibit various toxic effects on humans and could pose a substantial health concern [57]. In addition to DOIP, TBC is another non-phthalate plasticizer that was identified in two vinyl glove samples. TBC has been reported to be a safer alternative to phthalates and biocompatible plasticizers [58,59]. It has numerous applications in the polymer industry, particularly for the synthesis of PVC polymers used for food contact materials [59].

Fatty acids and hydrocarbons are used in plastic formulations as secondary plasticizers, in addition to performing other roles, such as lubrication [60]. These additives were identified in latex, nitrile, and polyethylene glove samples analyzed in this study. Moreover, fatty acids and their derivatives are receiving increasing attention as natural-based plasticizers because of their low toxicity and low migration [61].

4.4. Health Risk Assessment

Chronic exposure to phthalate compounds is associated with various adverse health effects on humans [23,24]. It has been reported that an HI less than unity indicates no adverse health effects, whereas an HI greater than unity indicates possible adverse health effects [29]. Accordingly, exposure to phthalates through inhalation and dermal pathways from the use of the examined face mask samples is not expected to have adverse health effects on humans. A similar conclusion was drawn by Wang et al. (2022) for single-use face masks. They concluded that although face masks were considered a source of human exposure to phthalates, the inhalation risk associated with this source was low. However, the authors warned that because of the unprecedented use of face masks worldwide due to the COVID-19 pandemic, wearers were still exposed to this source of phthalates for extended time periods, which could increase the adverse health risk to humans, particularly frontline workers.

Similar to the exposure from face mask samples, exposure to phthalates through the inhalation pathway from the use of the examined face shield samples is not expected to have adverse health effects on humans. Furthermore, it is also supposed that the use of gloves does not expose consumers to adverse health effects through the dermal pathway. On the other hand, the maximum acceptable limit of CR is 1 × 10⁻⁶. Therefore, all values are lower than 1 × 10⁻⁶, indicating that face masks do not expose consumers to possible cancer risk from phthalate compounds, with the exception of two glove samples that can expose consumers to possible cancer risk.

4.5. Environmental Impact

PPE, such as face masks, face shields, and protective gloves, is mainly made of synthetic polymers. In many cases, the massive production and consumption of disposable and reusable PPE during the COVID-19 pandemic have been associated with their improper final disposal. Plastic waste from disposable face masks alone was estimated to be more than four million tons on a daily basis during the COVID-19 pandemic [62]. This volume of waste certainly causes great challenges for conventional solid waste management worldwide and can lead to adverse effects on the environment and human health. Numerous recent studies have reported the improper disposal of large amounts of PPE into rivers, coastal habitats, and cities all over the globe [63,64,65,66,67]. Unfortunately, PPE pollution is now ubiquitous due to the unprecedented consumption of plastic PPE during the global COVID-19 pandemic and is associated with poor waste management and environmental awareness [68]. The environmental impacts of PPE pollution include entanglement of wildlife; increased environmental pollution in the form of microplastics; and the release of a spectrum of chemical constituents, such as phthalate plasticizers and flame retardants, into the environment [63,69,70]. The levels of global environmental exposure to chemical pollutants resulting from discarded PPE materials in landfills and their degradation products was estimated to reach tons of chemicals per year [63]. Phthalate plasticizer content was found at a level of up to 14% (w/w) in some of PPE in this study. Therefore, large amounts of these hazardous chemicals were expected to be released into the environment during the COVID-19 pandemic. Elevated concentrations of phthalates (up to 8201 µg L⁻¹) have been found in landfill leachates because of the increased industrial and household waste disposal, and these pollutants can reach aquatic environments such as surface water and groundwater aquifers [71].

The impact of PPE pollution on the environment was reviewed in a number of recent articles [72,73,74,75], and the authors made some recommendations and suggested some strategies for its control and for the protection of our environment and ourselves. These strategies include the proper disposal of PPE waste, raising public awareness regarding the negative impacts of PPE pollution, promoting reusable PPE, identifying and removing PPE associated with plastic and microplastic pollution, and developing new PPE products using biodegradable and sustainable materials.

5. Conclusions

The COVID-19 pandemic caused a surge in the global demand for PPE, which is mostly manufactured from plastic materials. Phthalate plasticizers are the industry-preferred materials for plastic formulations. However, this group of plasticizers is linked with various adverse health effects in humans. Therefore, this study investigated the presence and levels of six of the most commonly used and regulated phthalates in various PPE samples collected during the pandemic. The levels of these phthalates found in face shields and face masks were in the range of 0.29 µg/g to 942.60 µg/g. The health risk assessment concluded that these levels were not expected to pose adverse health effects to the wearer. However, because of the high use of face masks and face shields worldwide during COVID-19, wearers were exposed to this source of phthalates for extended periods, which could have increased their health risk, particularly for frontline workers. Two vinyl glove samples were found to have a total phthalate content exceeding 11% and 14% (w/w) of the glove’s weight. These levels could expose consumers to possible cancer risk. In addition to the possible health risks, the massive amounts of PPE disposed of in the environment during the COVID-19 pandemic can cause the release of large amounts of phthalates into the environment and represent a serious environmental challenge. Therefore, careful management plans for the disposal of PPE should be implemented to control these adverse environmental impacts.