1. Introduction

2. Materials and Methods

2.4. Calculations and Exceedance Analysis

Due to the only basic arithmetic calculations in our study, the software Libre Office Calc [47] was used. If not realised in the included publications, we additionally performed a comparative analysis of the content and release of the toxic substances from the face masks with reference to (most appropriate) threshold limits. Such limits e.g., for the ambient air, are given by national or international institutions and organisations. For example, data from the United States Environmental Protection Agency (USEPA) [48], data from the WHO [49], as well as from the German Federal Environment Agency [50] and the European Union (EU) target limits [51] were taken into consideration. Similarly, textile content threshold values from international, high quality and standard organisations like the Oeko-Tex [52] were used. The calculated and extracted exceedance results were considered in the discussion section and were presented in separate tables. Text and tables were generated with Libre Office software [53].

For the purpose of data comparison the results of the included studies have been standardized and converted to values per mask, if not primarily reported. For those calculations data from the primary studies were gathered. If the necessary parameters were not exhaustively specified in the primary studies (e.g., mask surface or weight), we used valid values stated in previous scientific publications. Average mask weight was estimated from studies that give the specific mask weight within the scope of their measurements (average weight of the mask without rubber bands and nose clip, and if applicable also without valve) [54]. Thus, the disposable/textile/community mask was set at 2.5 g [55,56], the surgical mask was set at 3 g, the FFP2/KN95 at 4 g and the FFP3 mask at 5 g [54]. The average mask surface area was set at approximately 230 cm² (0.023 m²) [57], while we assuming the surface area of a standard N95 respirator to be 175 cm² (0.0175 m²) [58]. However, this assumption is not the worst case scenario, since some authors state larger surface areas in their primary evaluations [59]. For breathing calculations, we referred to the values from the USEPA calculating a breathing volume of 10 m³/12 h [60]. However, taking into account the high variability in breathing patterns, we assumed an adult at rest to breathe approximately 12–18 respirations per minute (mean 15), exchanging 0.5 litres - corresponding to approximately 0.5 m³/h, thus we rounded up for a simple calculation as 1 m³/2 h being in the normal range [61]. The exact calculation methods are mentioned continuously throughout our paper (e.g., by descriptions in the discussion, or as footnotes in the tables).

Figure 1. Flow diagram of the scoping review according to PRISMA. The selection was strictly based on the inclusion and exclusion criteria and the applied quality assessment (see methods section, inclusion and exclusion criteria).

Figure 1. Flow diagram of the scoping review according to PRISMA. The selection was strictly based on the inclusion and exclusion criteria and the applied quality assessment (see methods section, inclusion and exclusion criteria).

3. Results

4. Discussion

4.1. Microfibers, Micro- and Nanoplastics (MPs and NPs)

4.1.1. MP and NP from Masks - Origin

Synthetic macromolecules with repeating units (plastic polymers) are the primary component of all types of face masks [13]. This fact is responsible for the mask being a significant source of plastic fiber and particle release [12,32,59,64,65,66,67,68,69,70]. Therefore, the mass consumption of face masks has generated a huge additional source of microplastics (MPs < 5 mm) or even nanoplastics (NPs < 1 μm) pollution [78,79,80,81,82]. Mask manufacturing materials consist of specific polymers with polypropylene (PP) being the most widely used [83], although polyethylene (PE), polyamide (PA), polystyrene (PS), and polyethylene terephthalate (PET), or polyester (PES) also are commonly used in synthetic textiles [23,32,59]. Especially, the nanofibers created from microfibers and fragments of melt-blown filters of facemasks (middle layers) contribute to the dust release and inhalation risk of MPs and NPs while wearing a mask [13]. When producing these non-woven fabrics, high-speed hot air is applied to blow the thermoplastic polymer to a conveyor collector [84]. NPs and MPs are generated during the production process of these fine fibers, giving face masks the potential to act as a primary source of MPs [68]. While the surgical mask usually consists of three layers with one melt-blown fiber layer [80], the FFP2/N95 mask has 5 layers, thereof two melt-blown fiber layers [59].

4.1.2. MP and NP from Masks - Release and Intake

Exposure to plastic particles has increased continuously in the modern world [85], but the obligations to wear masks around the world during the SARS-CoV-2 pandemic 2020–2023 [1] has increased this exposure even further [86]. Recent environmental studies have reported that plastic-based personal protective equipment (PPE) releases substantial amounts of NPs and MPs, to the environment [28,80,87]. The NPs and MPs released from face masks were detected even in marine organisms showing their broad distribution [13,64]. Once released, these MPs and NPs (MPs, <5 mm, NPs, <1 μm) originating from masks pose a delayed indirect environmental health risk to humans regarding oral uptake and inhalation [88].

But, according to the study results at hand, there exists also a significant direct immediate inhalation risk for the user, from the mask breathing zone into the airways [12,32,59,64,65,66,67,68,69,70], as already assumed by other papers [13,26,88,89]. The fact that MPs were also detected in the nasal mucus shortly after mask wearing [31,32] gives evidence that MPs can be directly inhaled while wearing a mask. This additional inhalation risk was also laboratory proven by breathing simulations with diverse mask types (N95, surgical and other) by Li et al. [12]. However, this study was not conducted in super-clean laboratory (no contamination control measures were applied) thus it is not clear whether the control air in the blank measurements (no mask) does not correspond to the air already contaminated by mask handling. Therefore, the control values (without mask) in this study should be interpreted with caution, as they probably provide additional evidence for the release of plastics from masks.

Interestingly, the release of MPs and NPs is predominantly higher for the N95 type when compared to the surgical mask [32,59,65,66,67,78]. This fact could be due to more layers including two melt-blown and thus higher overall plastic content and weight of the N95 mask. According to the literature, reusing a mask increases even the risk of microplastic release: regardless of whether a mask is new or used, the risk of inhaling spherical-type MPs and NPs released from the facemask remains significant [12,78]. Problematic is that mechanical stress, e.g., a beard under the mask or pulling the mask out of the pocket may contribute to mask’s physical abrasion of microplastics [13].

In the evaluated literature we found a possible maximal release of MPs up to 5390 particles per mask within 24 h [59] and a maximum mass loss of 0.831 mg/N95 mask (particles and fibers) during 24 h [67]. Depending on the filters and analytic methods used, the release experiments describe different sizes of the mask debris. For released fibers we found a size range of 25 µm to 2.5 mm [66,69,70] and an amount of 3152 fibers per surgical mask [69]. For released particles we found a size range of 89 nm [77] to 500 µm [70], among many other dimensions [12,32,59,64,65,67,68]. Noteworthy, a study with precise analysis on silicon wafers and using scanning electronic microscopy (SEM) for exploration describes most of the particles involved smaller than 1 µm [32].

Surgical and N95 masks have been designed to be worn for very specific purposes such as in hospital surroundings and for a short period of time [90]. If they are crumpled up in people’s pockets where the friction and damp environment promotes significant fiber abrasion and worn for longer periods of time, a high microplastic release is possible, as shown by included papers [12,64,67].

However, it is interesting to compare the plastic release of masks while wearing them for a period of time, e.g., 2 hours with average breathing of 1 m³ to known MP concentrations in ambient air given as n/m³. For example, the mask-independent average concentration of airborne MPs in the United States of America (USA) is being described in 2019 as high as 5.6 n/m³ (outdoor) and 12.6 n/m³ (indoor) and >59% were MPs with the size of <50 μm. [91] In Shanghai, China, the airborne MP concentration was maximum 4.18 and on average 1.42 ± 1.42 with a size range of 23–5000 μm [92]. An analytic study in Paris 2017 evaluated the indoor air concentrations of 0.4–59.4 n/m³ with 33.3% containing polymers. Outdoor fiber concentration was 0.3–1.5 n/m³ with presence of numerous inhalable MPs below 50 µm [93].

In contrast to MPs, to date, there is no information regarding the amount or concentration of airborne NPs [94].

According to the data in our extraction tables (Table 2) and assuming a case scenario with wearing a mask appropriately for 4 hours while breathing on average a total of 2 m³ air, the mentioned average concentration of airborne MP values (USA, China, France) would be highly exceeded during mask use and breathing through [32]. Under a worst case assumption, that the mask MP release during 4 hours would be as high as in the analytical experiments by Ma et al. [32], the subject wearing a mask 4 hours would inhale up to 2200 n/m³, exceeding the environmental airborne MP content of outdoor air in the USA by a factor of approximately 400 and in China and Paris even by a factor of approximately 1500. Regarding the MP concentrations in indoor air in Paris, the mask would be responsible for a 37-fold increase of the microplastic particles. Moreover, the mask release of microplastic would be shifted to extremely higher concentrations of smaller MP particles (and even NPs) than known in the environment [32,65,68].

Cox et al. have estimated that the intake of MPs by humans via food and inhalation ranges between 203 and 312 particles per day [95]. Our results indicate that wearing masks may substantially increase that daily inhalation of MPs by a factor of 10 to 22 (Table 2) under assumptions of release with wearing time between 1 h and 4 h [32,69]. But in other worst case release scenarios (wearing time for >4 h the daily inhalation of MPs would even increase by a higher factor (Table 2) [12,59].

Interestingly, the estimated daily intake (EDI) values of MPs via street dust ingestion ranges from 0.6 to 4.0 for children and from 0.3 to 2.0 particles per day for adults in Tehran, Iran [96]. Nevertheless, in some heavily polluted areas, such as Asaluyeh County, Iran, higher EDI values of MPs for children and adults were 0.7–103.3 and 0.3–51.7 particles/d, respectively [78,97].

Consequently, our results indicate that wearing masks may increase such values of inhalation of MPs by a high factor. With possible maximal mask MP release during breathing of 3090 particles/mask in only 2 h [12] and a maximal possible MP leaching of 5390 particles/mask in 24 h [59] (Table 2) the estimated daily intakes mentioned above (even those in heavily polluted regions) might be highly exceeded while wearing a mask by a factor of 30 or more, assuming a worst case scenario [12,69] (Table 2, Figure 3).

4.1.3. Limits for MPs (Nps)

A regulatory standard for MP and NP release from medical masks is not established so far. In contrast, efforts by major public health and environmental organizations around the world to reduce the dangers posed by particulate matter are intensifying [98].

MPs are categorized according to their diameter into particles > 10 μm, particles < 10 μm (PM₁₀), particles < 2.5 μm (PM_2.5), and ultra-fine particles < 0.1 μm [99]. The large particles > 10 μm are assumed to collide with the upper airways upon respiration, whereas PM₁₀ can enter the bronchioles, and PM_2.5 and ultra-fine particles can penetrate the alveoli [85,99,100]. The shape of MPs influence their toxicity by modifying interactions with cells and tissues (shape-specific toxicity) [100,101]. Moreover, the surface charge of micro-particles can affect their toxicity (particles potential, electrostatic interactions of MPs with cells and tissues including adhesion) [100,102,103].

MP adsorption of molecules, leaching of softeners and microorganisms can additionally modify their toxicity. The MPs may act as a carrier of adsorbed toxins or pathogenic bacteria and fungi [90] enlarging their potential to impact human health [100,104].

Concerning microplastic particles, being a relatively new and modern environmental harm, only few official limits exist [105]. For example, the updated WHO Air Quality Guidelines (AQG) state that annual average concentrations of PM_2.5 should not exceed 5 µg/m³, while 24-hour average exposures should not exceed 15 µg/m³ more than 3 to 4 days per year [106].

According to our data (Table 2) those thresholds appear to be exceeded while wearing a mask in a worst case scenario. A release of 34.63 µg MP per hour per mask (N95) may be possible [67]. Considering that only a few reliable studies with adequate fine particle filtering (e.g., silicon waver) and analytical methods (e.g., SEM) exist on mask-released particles [32], only these can be used to estimate the exact size of the released smaller particles. In fact, Ma et al. detected very small particles being predominantly <1 µm - equivalent to at least PM_2.5 [32,99]. Thus, we can assume for the worst case scenario, that wearing face masks, particularly N95 masks, may lead to highly exceeding the WHO PM_2.5 guidelines for 24-hour average exposure of 15 µg/m³ (Table 3A). Also the annual average concentrations of 5 µg/m³ PM_2.5 could have been exceeded, e.g., during mask wearing enforced by law during 2020–2023 with regular and/or daily use of masks in many countries [1]. None of the existing medical mask standards, including the ASTM standards (F1862, F2100, F2101, F2299) and NIOSH regulation (42 CFR 84), which are adopted by the FDA in regulating medical face masks and surgical respirators in the U.S. (FDA, 2020a), regulate respirable debris such as micro(nano)plastics that may be present in these products. ISO standards (ISO 22609, 16900), EU standards (EN 140, 143, 149, 14683) and Chinese standards (GB 19083, 2626; GB/T 32610, 38880; YY 0469; YY/T 0969) on masks and respirators give no information pertinent to the particular type of microplastic related hazard. However, according to our data those appeared necessary for many in their daily life and work, particularly during the pandemic. Thus, questions must be raised over this apparent regulatory gap concerning the long-term use safety of face masks [89].

Table 3A. Exemplary limit threshold exceedance for microplastics, MP (PM_2.5) in worst case scenario while wearing a mask.

Table 3A. Exemplary limit threshold exceedance for microplastics, MP (PM_2.5) in worst case scenario while wearing a mask.

Publication	Mask type	Outcome	Result *	AQG WHO [106] threshold value **	Factor of exceedance
Liang 2022 [67] (Ma 2022 [32])	N95	MP (PM2.5) release	41.55 µg/m3 (72 min use)	5 µg/m3 (PM2.5) annual average	8.31
Liang 2022 [67] (Ma 2022 [32])	surgical	MP (PM2.5) release	33.9 µg/m3 (72 min use)	5 µg/m3 (PM2.5) annual average	6.78
Liang 2022 [67] (Ma 2022 [32])	N95	MP (PM2.5) release	41.55 µg/m3 (72 min use)	15 µg/m3 (PM2.5) 3 to 4 days (24 h) per year	2.77
Liang 2022 [67] (Ma 2022 [32])	surgical	MP (PM2.5) release	33.9 µg/m3 (72 min use)	15 µg/m3 (PM2.5) 3 to 4 days (24 h) per year	2.26

Legend: MP = Microplastic, PM_2.5 = Particulate matter (≤2.5 µm), WHO = World Health Organisation. Footnotes: * calculated from 831 µg/24 h (N95) and 678 µm/24 h (surgical) [67]. Particles are assumed to be predominantly less or equal to 2.5 µm [32]. Breathing air is estimated to be 10 m³ in 12 h according to USEPA [60]. Particle release in the first 24 hours is estimated to be linear (34.63 µg/h and 28.25 µg/h for N95 and surgical mask, respectively) [67]. ** for further details see discussion section, limits for MP/NP.

4.1.4. MP and NP Risks

The toxicology of fibers and particles is becoming more and more important as the modern world contains ever more artificial objects [107,108]. Noteworthy is the fact that plastic particles released in the course of medical treatment and application of implants have been known since decades to be responsible for undesirable reactions in diverse tissues [109,110,111,112,113].

But above all, the breathing of microplastics has become more and more a health risk concern [114]. MPs found in nasal mucus following mask use [31,32] and complaints of throat irritation or discomfort in the respiratory tract by children, the elderly adult, or other sensitive individuals after using face masks are alerting signs of respectable amounts of respirable debris inhaled from masks and respirators [115,116]. There is very recent evidence of MPs isolated in lower airway of European citizens examined in 2021, a time with rigid mask mandates and a year after they had been introduced during the pandemic [117]. The involved subjects came from regions, where face mask mandates were enforced by law and widely followed [1]. Another scientist team could show resembling results in a similar investigation period with microplastic particles in all parts of the lungs containing predominantly polypropylene and polyethylene [118], which are the most common components of the face mask [59]. Thus, a correlation of mask wearing and the recently detected high amounts of MP in human lungs appears conclusive [13,31,32].

Generally, it can be concluded that face masks contribute to direct microplastic inhalation risk [13] and therefore expose the mask user immediately to health risks [114,119,120,121].

Special consideration must be given to the fact that due to increased breathing resistance wearing a mask can cause substantial damage to nasal airflow [26,122]. Due to the presence of the mask, people have a natural tendency to breathe through the open mouth which means less breathing resistance bypassing the nasal airflow [26,27]. Usually under natural nose breathing [123] particles impact further up the respiratory airways depositing in a size-dependent manner from the nasal passages to the larger bronchioles. The nose effectively filters foreign particles that enter the nasal cavity dependent on particle size and air flow rate with filtration efficiency decreasing with smaller particle size. Therefore, usually only smaller particles (<1–3 μm) diffuse deep into the lung tissue, depositing in the alveoli by a number of mechanisms including diffusion, sedimentation, and electrostatic effects. This relationship (particle size-depth of diffusion and deposition) is constant across humans [123,124]. Most humans incline to revert to oral breathing during mask wearing [26,27]. This significantly increases the amount and size of particles that may be directly inhaled into the bronchi and lungs due to bypassing the filtration of the nasal cavity [125]. In a human study using a radiolabelled aerosol, scientists found a huge increase in deposition in the lungs (+37%) when breathing through the mouth compared to the nose (75% vs. 38%) for particle diameters averaging 4.4 µm (range 3.8–5.1 µm) [126].

Thus, taking into account the nearly zero distance to the airways and the predominant mouth breathing, the particle release from masks and their appearance in the mask breathing zone, appear to be worse (predominant mouth breathing) than similar particle presence in normal air in the no mask condition (predominant nose breathing). This seems comparable to the difference between active and passive cigarette smoking, with higher risk for active smokers due to frequent inhalation of particles directly at nearly zero distance through mouth breathing [127].

In this respect, the use of room air limit values in the evaluation of (predominantly oral) respiration from the mask breathing zone (with the particles released there) does not seem entirely appropriate for comparison. Noteworthy is, that inhaled ultra-fine particles can penetrate the alveoli where they can enter the bloodstream [100]. In addition, scientific reports exist on microplastics in human blood with evidence of origin from masks used worldwide [128,129].

MPs exposure can cause toxicity through oxidative stress, inflammatory lesions and there is a potentiality of metabolic disturbances, neurotoxicity, and increased cancer risk in humans [105].

According to the WHO, air pollution (including MPs and NPs) is the second highest risk factor for noncommunicable diseases [130].

For the long term exposure, there is clear evidence that both PM_2.5 and PM₁₀ were associated with increased mortality from all causes: cardiovascular disease, respiratory disease and lung cancer. And the associations even remained below the former 2005 WHO guideline exposure level of 10 µg/m³ for PM_2.5 [131,132].

Moreover, even the short-term exposure to particulate matter with aerodynamic diameters less or equal than 10 and 2.5 µm (PM₁₀, PM_2.5) are positively associated with increased cardiovascular, respiratory, and cerebrovascular mortality [133].

The toxic effects of micro- and nanoplastics comprise inflammation with disruption of immune function (increased IL1-q, IL-1ß, IL-6, IL-8, IL-10) oxidative stress and apoptosis (increased ROS, ER stress), as well as disturbance of metabolic homeostasis (altered channel function of K⁺-channels, blocking of vesicle transport, dysbiosis, intestinal barrier function disturbance, absorption disturbance, impairment of energy metabolism), neurotoxicity (AChE activation), reproductive toxicity and DNA-damage (DNA breaks) [94,134,135].

The COVID-19 pandemic has increased face mask pollution, and the release of nanofibers from face masks has been reported to inhibit even reproduction and growth [136]. NP and MP exposure also damages the seminiferous tubules, causing apoptosis in spermatogenic cells and lowering sperm motility and concentration, increasing the frequency of sperm abnormalities [137].

But there exists even more harm due to inhaled mask debris: Face mask microfibers and particles may serve as an important vehicle for harmful contaminants [10,65,104]. The plastics usually contain chemicals from raw monomers and various types of additives to improve their properties. MP particles have been demonstrated to be very important carriers for the transformation and accumulation of the toxic PAHs (see referring section) [104]. In addition, plastics also absorb chemicals from their surroundings [94,104,138] including heavy metals [65] as well as microorganisms [134]. Moreover, a microorganism growth on and in masks is scientifically proven [90,139].

All these mechanisms can potentiate the adverse effects of MP and NP released from masks.

Finally, a significant role of MPs and NPs in exacerbating the COVID-19 pandemic has been discussed, as plastic particles that loaded the virus into the air increased the half-life of the virus and facilitated the transmission of the virus to humans through the Trojan horse effect: Increased transmission and, consequently, more cases of COVID-19 will lead to rising production and use of surgical masks, an acknowledged source of MPs and NPs [13]. The findings of Fögen 2022 [140] using data from the USA which show that mask use correlates with an increased mortality and case fatality rate of COVID-19 could be due to these processes. This phenomenon could also explain the elevated face mask related mortality found by Spira [141] in the EU. Possibly the respiratory overload with NPs and MPs due to N95 masks [12,32,59,64,65,66,67,68,69,70] could be responsible to the measured nasal blockage, postnasal discharge as well as to impairment in mucociliary clearance function while using a medical mask [142]. Thus, an impaired self-cleaning of the mucous membranes may favour infections and be responsible for the opposite effect - more rather than fewer respiratory infections - under face mask use at the population level [140,141]. Correspondingly, higher respiratory infection rates have been observed in Germany [143] and USA [144], where mask mandates for long periods were enforced by law [1]. Additionally, COVID-19 rates have been able to expand swiftly especially during Omicron [145] even in societies where mask use was assiduously followed - as in Korea, Taiwan, Hong Kong and Singapore [146].

Noteworthy is also the problem regarding nanoparticles: Females are particularly more vulnerable to NP toxicity, and this may affect reproductivity and fetal development [147]. Additionally, various types of NPs have negative impacts on male germ cells [147]. Moreover, NPs as an environmental hazard are able to cause allergic asthma, pleural, interstitial lung disease and even sarcoma [148,149].

4.9. Consequences for Science and Supervisory Authorities

Currently, the quality control of face masks is only focused on their physical and biological properties, that is, the filtration efficiency, e.g., ASTM F2101 and EN 14683 [57,185] BS EN 14683:2019 [24] and microbial populations, e.g., ISO 11737-1 [24] but does not address the levels of hazardous chemicals contained in them. This fact needs to be reconsidered, as our scoping review revealed the repeated detection of several hazardous ingredients in face masks and also their calculated emissions and contents of concern with exceeding institutional limit thresholds of WHO, EPA, European Union (EU) and German Federal Environmental Agency (see Tables 3A–3C). In addition, the masks have higher content of certain substances than the health maintaining Oeko-Tex Standard 100 label allows. Thus, health concerns for some masks and individual mask wearing conditions cannot be excluded (skin contact, inhalation at nearly zero distance, oral intake). In this regard, mask wearing may exert a higher risk of exposure than many environmental sources. Thus, a special, customized risk assessment for individual toxins in masks appears necessary. The evidence we have found for toxins in masks is more than troubling, especially given the worldwide use by diverse even susceptible portions of the population (e.g., children, pregnant women, adolescents).

Researchers have shown with their calculations that the special mask situation also requires a different evaluation without simple recourse to room air or product standards [24,56,77].

Fifteen of the 24 face mask studies included (63%) indicated high or excessive concentrations of inanimate toxins (institutional and organizational limits) (Tables 3A–3C). Thereof, five studies on MP an NP showed highly elevated levels [12,32,59,67,69] with possible exceedances for both surgical and N95 masks (Table 3A). Six papers indicated levels that are above institutional and organisational limits for organic compounds (Table 3B) including TVOC, VOCs, phthalates, acrolein, DEHP and PFAs in all types of masks (textile, surgical and N95 masks) [9,24,25,55,56,68,72].

As can be seen from Table 3C four studies revealed exceedances for trace elements and heavy metals including Pb, Cd, Co, Cu, Sb and TiO₂ in textile, surgical and N95 masks [68,70,76,77].

Table 3B. Exemplary limit threshold exceedance of organic compounds in a worst case scenario while wearing a mask).

Table 3B. Exemplary limit threshold exceedance of organic compounds in a worst case scenario while wearing a mask).

Publication	Mask type	Outcome	Result *	Threshold value Institution/Organisation **	Factor of exceedance
Kerkeling 2021 [72]	N95	TVOC release	403 mg/m3 (17 min)	0.3 mg/m3 target guideline European Community [157,161,162,164] German Federal Environment Agency [158,159,160,164,165]	1343
Kerkeling 2021 [72]	N95	TVOC release	403 mg/m3 (17 min)	0.5 mg/m3 Oeko-Tex [154]	806
Xie 2022 [55]	textile	DEHP content	36.7 µg/g	0.01% of weight Oeko-Tex [154]	367
Xie 2021 [56]	textile	SVOC carcinogenic risk (CR)	2.27 × 10−4	≤1 × 10−6 US EPA [186,187]	227
Xie 2022 [55]	textile	Phthalates content	37.7 µg/g	0.025% of weight Oeko-Tex [154]	150.8
Muensterman 2022 [9]	textile (coated)	PFAS content	2900 µg/m2	250 µg/kg Oeko-Tex [154]	107
Kerkeling 2021 [72]	N95	Xylene release	12 mg/m3 (17 min)	10 mg/kg Oeko-Tex [154]	70.8
Xie 2022 [55]	N95	DEHP content	6.3 µg/g	0.01% of weight Oeko-Tex [154]	63
Muensterman 2022 [9]	textile (coated)	FTOH content	1200 µg/m2	250 µg/kg Oeko-Tex [154]	44.2
Xie 2022 [55]	textile (for children)	Phthalate carcinogenic risk (CR)	4.26 × 10−5	≤1 × 10−6 US EPA [186,187]	42.6
Kerkeling 2021 [72]	N95	TVOC release	403 mg/m3 (17 min)	10 mg/m3 AgBB, German Federal Environment Agency [164,165]	40
Muensterman 2022 [9]	textile	PFAS content	910 µg/m2	250 µg/kg Oeko-Tex [154]	33.5
Zuri 2022 [59]	N95	phthalates content/release	8.16 µg/g	0.025% of weight Oeko-Tex [154]	32
Zuri 2022 [59]	surgical	phthalates content/release	7.56 µg/g	0.025% of weight Oeko-Tex [154]	30
Jin 2021 [24]	surgical	Acrolein release	0.5 μg/m3 (30 min)	0.02 μg/m3 US EPA [166,167]	25
Xie 2021 [56]	N95 (for children)	SVOC carcinogenic risk (CR)	2.5 × 10−5	≤1 × 10−6 US EPA [186,187]	25
Kerkeling 2021 [72]	N95	Xylene release	12 mg/m3 (17 min)	500 µg/m3 AgBB, German Federal Environment Agency [158,159,160,164,165]	24
Xie 2021 [56]	N95	SVOC carcinogenic risk (CR)	1.59 × 10−5	≤1 × 10−6 US EPA [186,187]	15.9
Xie 2022 [55]	textile	Phthalate carcinogenic risk (CR)	1.45 × 10−5	≤1 × 10−6 US EPA [186,187]	14.5
Chang 2022 [25]	surgical	TVOC release	>1 mg/m3 (1 h)	0.3 mg/m3 target guideline European Community, [157,161,162,164] German Federal Environment Agency [158,159,160,164,165]	>3
Chang 2022 [25]	surgical	TVOC release	>1 mg/m3 (1 h)	0.5 mg/m3 Oeko-Tex [154]	>2
Muensterman 2022 [9]	surgical	PFAS content	46 µg/m2	250 µg/kg Oeko-Tex [154]	1.4
Muensterman 2022 [9]	textile	FTOH intake estimation 10 h mask use	7.04 µg/kg-bw/day	5 µg/kg-bw/day Danish Ministry of Environment [184]	1.4
Xie 2021 [56]	N95	Naphthalene content	2.43 µg/g	2 mg/kg Oeko-Tex [154]	1.2

Legend: AgBB = Ausschuss zur gesundheitlichen Bewertung von Bauprodukten (Committee for the Health Evaluation of Building Products, Federal Environment Agency Germany), DEHP = di(2-ethylhexyl) phthalate, FTOH = 6:2 fluorotelomer alcohol, kg-bw = kilogram per bodyweight, PFAS = Poly- and perfluoroalkyl substances, SVOC = semi volatile organic compounds, TVOC = Total Volatile Organic Compounds, US EPA = United States Environmental Protection Agency, VOC = Volatile Organic Compounds. Footnotes: * If necessary, the units had to be converted, with the surface area of the N95 respirator being 175 cm² (0.0175 m²) [58] and the surface area of the surgical/textile mask being 230 cm² (0.023 m²) [57]. If not given in the studies the average weight was set at 2.5g for cloth masks [55,56], 3g for surgical masks and 4g for N95 mask [54]. Breathing air was estimated to be 10 m³ in 12 h according to USEPA [60]. Please note: VOCs release in the first hours is known to decrease exponentially [25]. ** for further details see discussion section, limits for VOCs, PFAS, phthalates.

Table 3C. Exemplary limit threshold exceedance of anorganic toxins and compounds in a worst case scenario while wearing a mask.

Table 3C. Exemplary limit threshold exceedance of anorganic toxins and compounds in a worst case scenario while wearing a mask.

Publication	Mask type	Outcome	Result *	Threshold value Institution/Organisation **	Factor of exceedance
Verleysen 2022 [77]	textile, reusable	TiO2 exposure Adverse effect level (AELmask) two mask per day, 8h	4394 μg	3.6 µg ANSES, France [188,189,190]	1220
Bussan 2022 [76]	surgical	Pb content	13.3 µg/g	0.2 mg/kg Oeko-Tex [154]	66.5
Bussan 2022 [76]	surgical	Cu content	410 µg/g	50 mg/kg Oeko-Tex [154]	8.2
Sullivan 2021 [70]	textile	Pb content	0.68 µg/g	0.2 mg/kg Oeko-Tex [154]	3.4
Bussan 2022 [76]	N95	Sb content	90.18 µg/g	30 mg/kg Oeko-Tex [154]	3
Z. Liu 2022 [68]	surgical	Cd content	0.22 µg/g	0.1 mg/kg Oeko-Tex [154]	2.2
Sullivan 2021 [70]	textile	Cd content	0.19 µg/g	0.1 mg/kg Oeko-Tex [154]	1.9
Z. Liu 2022 [68]	surgical	Co content	1.33 µg/g	1 mg/kg Oeko-Tex [154]	1.33
Sullivan 2021 [70]	textile	Sb content	39.3 µg/g	30 mg/kg Oeko-Tex [154]	1.3
Z. Liu 2022 [68]	surgical	Pb content	0.22 µg/g	0.2 mg/kg Oeko-Tex [154]	1.1

Legend: Cd = Cadmiun, Co = Cobalt, Cu = Copper, Pb = Plumbum (Lead), Sb = Stibium (Antimon), TiO₂ = Titandioxide. Footnotes: * If not given in the studies the average weight was set at 2.5g for cloth masks [55,56], 3g for surgical masks and 4g for N95 mask [54]. ** for further details see discussion section, limits for trace elements and heavy metals.

Figure 4 summarises the toxic substances and classes that may be responsible for limit value exceedances with resulting potential life-shortening effects.

Moreover, there are possible chemical reactions of all the reported chemicals with each other and with the exhaled compounds resulting from human metabolism [191] in the mask breathing zone (mask dead space), e.g., oxidation. For this reason, the mask breathing zone could act as a “chemical reactor” at the entrance of the airways. This phenomenon could lead to further toxic compounds with a new kind of threat to human health. One has to consider that the mask dead space does not only have a higher temperature, but is more humid [26,63], which facilitates many chemical reactions. It should not go unmentioned, that there is an additional possibility of amplifying toxic effects, resulting from the mixture of toxins.

Mask use may additionally - even if not exceeding threshold values - increase the burden of the airways and lungs and organs with chemical compounds, heavy metals, micro-and nanoplastics. And there could be a cumulative effect concerning indoor use of masks (which was recommended by the WHO during the pandemic) [192], because indoor air exposition to several toxic compounds (e.g., VOCs, MPs and NPs) is per se higher than outdoors [72]. Some of the substances are ultrafine (e.g., TiO₂, NPs) and require another risk and toxicological evaluation [32,77,147,148]. Interestingly, face masks have no toxicological regulations so far.

Despite a broad narrative during the SARS-CoV-2 pandemic supporting the efficacy of face masks against virus transmission [62,63] there is only weak evidence for the effectiveness against respiratory viral infections even from the highest evidence-based institutions [193]. Regarding our results of multiple toxic substances released by face masks that can be ingested and inhaled (Table 1, Table 2 and Table 3), the introduction of mask mandates by law for the general population in many countries during the SARS-CoV-2-pandemic 2020-2023 appears questionable from an empirical and scientific perspective.

Considering the weak antiviral effectiveness [62,63] and the lack of medium or strong empirical evidence for face mask effectiveness in preventing respiratory virus infections [26,62,63], wearing face mask frequently during the SARS-CoV-2 pandemic - according to our results - may have led to negative health and possible life shortening effects. From environmental science a lot of chronic subthreshold toxic effects have been evaluated and described and have been named “silent killer effects” [63,194,195,196,197,198,199]. As the mask wearing may be linked to toxin exposure and an unprecedented use worldwide occurred, a toxic influence related to the general population could contribute to a similar effect [26,63,194,195,196,197,198,199,200]. Thus, without a thorough risk-benefit analysis enforced mask obligations by law as happened in the SARS-CoV-2-pandemic, acting against the evidence of science (regarding mask effectiveness and mask hazardous substance content standardization), should not be repeated in the future.

5. Limitations

6. Conclusions

References

1. Face Covering Policies during the COVID-19 Pandemic. Available online: https://ourworldindata.org/grapher/face-covering-policies-covid (accessed on 29 December 2022).
2. WHO Recommendations on Mask Use by Health Workers, in Light of the Omicron Variant of Concern: WHO Interim Guidelines, 22 December 2021. Available online: https://www.who.int/publications-detail-redirect/WHO-2019-nCoV-IPC_Masks-Health_Workers-Omicron_variant-2021.1 (accessed on 16 March 2023).
3. Verordnung Zum Schutz Vor Neuinfizierungen Mit Dem Coronavirus SARS-CoV-2 (Coronaschutzverordnung–CoronaSchVO) Volume 24. January 2023.
4. Knobloch, J.K.; Franke, G.; Knobloch, M.J.; Knobling, B.; Kampf, G. Overview of Tight Fit and Infection Prevention Benefits of Respirators (Filtering Face Pieces, FFP). Journal of Hospital Infection 2023, 134, 89–96. [Google Scholar] [CrossRef] [PubMed]
5. Helios führt allgemeine Maskenpflicht ein. Available online: https://www.helios-gesundheit.de/unternehmen/aktuelles/pressemitteilungen/detail/news/helios-fuehrt-allgemeine-maskenpflicht-ein/ (accessed on 16 March 2023).
6. Helios führt Maskenscanner in allen Kliniken ein. Available online: https://www.helios-gesundheit.de/unternehmen/aktuelles/pressemitteilungen/detail/news/helios-fuehrt-maskenscanner-in-allen-kliniken-ein/ (accessed on 16 March 2023).
7. Ladhani, S.N. Face Masking for Children—Time to Reconsider. Journal of Infection 2022, 85, 623–624. [Google Scholar] [CrossRef] [PubMed]
8. Thomson, S. Mask Mandates for Children during the COVID-19 Pandemic: An International Human Rights Perspective. Scand J Public Health 2022, 50, 683–685. [Google Scholar] [CrossRef] [PubMed]
9. Muensterman, D.J.; Cahuas, L.; Titaley, I.A.; Schmokel, C.; De la Cruz, F.B.; Barlaz, M.A.; Carignan, C.C.; Peaslee, G.F.; Field, J.A. Per- and Polyfluoroalkyl Substances (PFAS) in Facemasks: Potential Source of Human Exposure to PFAS with Implications for Disposal to Landfills. Environ. Sci. Technol. Lett. 2022, 9, 320–326. [Google Scholar] [CrossRef] [PubMed]
10. Kutralam-Muniasamy, G.; Pérez-Guevara, F.; Shruti, V.C. A Critical Synthesis of Current Peer-Reviewed Literature on the Environmental and Human Health Impacts of COVID-19 PPE Litter: New Findings and next Steps. Journal of Hazardous Materials 2022, 422, 126945. [Google Scholar] [CrossRef] [PubMed]
11. Liu, Y.; Wang, Z.; Wang, W.; Xing, J.; Zhang, Q.; Ma, Q.; Lv, Q. Non-Targeted Analysis of Unknown Volatile Chemicals in Medical Masks. Environment International 2022, 161, 107122. [Google Scholar] [CrossRef] [PubMed]
12. Li, L.; Zhao, X.; Li, Z.; Song, K. COVID-19: Performance Study of Microplastic Inhalation Risk Posed by Wearing Masks. J Hazard Mater 2021, 411, 124955. [Google Scholar] [CrossRef]
13. Khan, A.; Jia, Z. Recent Insights into Uptake, Toxicity, and Molecular Targets of Microplastics and Nanoplastics Relevant to Human Health Impacts. iScience 2023, 26. [Google Scholar] [CrossRef]
14. Chen, Y.; Chen, Q.; Zhang, Q.; Zuo, C.; Shi, H. An Overview of Chemical Additives on (Micro)Plastic Fibers: Occurrence, Release, and Health Risks. Reviews Env.Contamination (formerly:Residue Reviews) 2022, 260, 22. [Google Scholar] [CrossRef]
15. Ganesapillai, M.; Mondal, B.; Sarkar, I.; Sinha, A.; Ray, S.S.; Kwon, Y.-N.; Nakamura, K.; Govardhan, K. The Face behind the Covid-19 Mask—A Comprehensive Review. Environ Technol Innov 2022, 28, 102837. [Google Scholar] [CrossRef]
16. Aerts, O.; Dendooven, E.; Foubert, K.; Stappers, S.; Ulicki, M.; Lambert, J. Surgical Mask Dermatitis Caused by Formaldehyde (Releasers) during the COVID-19 Pandemic. Contact Dermatitis 2020, 83, 172–173. [Google Scholar] [CrossRef] [PubMed]
17. Raval, H.; Sangani, H. Certain Face Masks Contain Toxic Chemicals, Inhalation of Which Has the Potential to Affect the Upper Respiratory System. J. Trop. Dis 2021, 9. [Google Scholar]
18. Li, M.; Hou, Z.; Meng, R.; Hao, S.; Wang, B. Unraveling the Potential Human Health Risks from Used Disposable Face Mask-Derived Micro/Nanoplastics during the COVID-19 Pandemic Scenario: A Critical Review. Environment International 2022, 170, 107644. [Google Scholar] [CrossRef] [PubMed]
19. Shen, M.; Zeng, Z.; Song, B.; Yi, H.; Hu, T.; Zhang, Y.; Zeng, G.; Xiao, R. Neglected Microplastics Pollution in Global COVID-19: Disposable Surgical Masks. Sci Total Environ 2021, 790, 148130. [Google Scholar] [CrossRef] [PubMed]
20. Morgana, S.; Casentini, B.; Amalfitano, S. Uncovering the Release of Micro/Nanoplastics from Disposable Face Masks at Times of COVID-19. Journal of Hazardous Materials 2021, 419, 126507. [Google Scholar] [CrossRef] [PubMed]
21. Oliveira, A.M.; Patrício Silva, A.L.; Soares, A.M.V.M.; Barceló, D.; Duarte, A.C.; Rocha-Santos, T. Current Knowledge on the Presence, Biodegradation, and Toxicity of Discarded Face Masks in the Environment. Journal of Environmental Chemical Engineering 2023, 11, 109308. [Google Scholar] [CrossRef] [PubMed]
22. Masud, R.I.; Suman, K.H.; Tasnim, S.; Begum, M.S.; Sikder, M.H.; Uddin, M.J.; Haque, M.N. A Review on Enhanced Microplastics Derived from Biomedical Waste during the COVID-19 Pandemic with Its Toxicity, Health Risks, and Biomarkers. Environmental Research 2023, 216, 114434. [Google Scholar] [CrossRef] [PubMed]
23. Potluri, P.; Needham, P. 6—Technical Textiles for Protection. In Textiles for Protection; Woodhead Publishing Series in Textiles; Scott, R.A., Ed.; Woodhead Publishing, 2005; pp. 151–175. ISBN 978-1-85573-921-5. [Google Scholar]
24. Jin, L.; Griffith, S.M.; Sun, Z.; Yu, J.Z.; Chan, W. On the Flip Side of Mask Wearing: Increased Exposure to Volatile Organic Compounds and a Risk-Reducing Solution. Environ. Sci. Technol. 2021, 55, 14095–14104. [Google Scholar] [CrossRef]
25. Chang, Y.; Huang, R.-J.; Cheng, K.; Lin, C.; Ling, Q.; Haque, M.M.; Ovadnevaite, J.; O’Dowd, C. Highly Time-Resolved and Nontargeted Characterization of Volatile Organic Compound Emissions from Face Masks. Environ. Sci. Technol. Lett. 2022, 9, 1007–1013. [Google Scholar] [CrossRef]
26. Kisielinski, K.; Giboni, P.; Prescher, A.; Klosterhalfen, B.; Graessel, D.; Funken, S.; Kempski, O.; Hirsch, O. Is a Mask That Covers the Mouth and Nose Free from Undesirable Side Effects in Everyday Use and Free of Potential Hazards? International Journal of Environmental Research and Public Health 2021, 18, 4344. [Google Scholar] [CrossRef]
27. Wyszyńska, M.; Czelakowska, A.; Rosak, P.; Białożyt-Bujak, E.; Gruca, O.; Rosak-Szyrocka, J.; Kasperski, J.; Skucha-Nowak, M. Changes in the Oral Cavity Mucosal Surface under the Influence of Wearing Protective Face Masks—Nitric Oxide Concentration Analysis—Preliminary Report. Coatings 2022, 12, 1164. [Google Scholar] [CrossRef]
28. De-la-Torre, G.E.; Pizarro-Ortega, C.I.; Dioses-Salinas, D.C.; Ammendolia, J.; Okoffo, E.D. Investigating the Current Status of COVID-19 Related Plastics and Their Potential Impact on Human Health. Current Opinion in Toxicology 2021, 27, 47–53. [Google Scholar] [CrossRef] [PubMed]
29. Faustman, E.M.; Silbernagel, S.M.; Fenske, R.A.; Burbacher, T.M.; Ponce, R.A. Mechanisms Underlying Children’s Susceptibility to Environmental Toxicants. Environ Health Perspect 2000, 108 (Suppl 1), 13–21. [Google Scholar] [CrossRef] [PubMed]
30. Estevan, C.; Vilanova, E.; Sogorb, M.A. Case Study: Risk Associated to Wearing Silver or Graphene Nanoparticle-Coated Facemasks for Protection against COVID-19. Arch Toxicol 2022, 96, 105–119. [Google Scholar] [CrossRef] [PubMed]
31. Klimek, L.; Huppertz, T.; Alali, A.; Spielhaupter, M.; Hörmann, K.; Matthias, C.; Hagemann, J. A New Form of Irritant Rhinitis to Filtering Facepiece Particle (FFP) Masks (FFP2/N95/KN95 Respirators) during COVID-19 Pandemic. World Allergy Organ J 2020, 13, 100474. [Google Scholar] [CrossRef] [PubMed]
32. Ma, J.; Chen, F.; Xu, H.; Jiang, H.; Liu, J.; Li, P.; Chen, C.C.; Pan, K. Face Masks as a Source of Nanoplastics and Microplastics in the Environment: Quantification, Characterization, and Potential for Bioaccumulation. Environmental Pollution 2021, 288, 117748. [Google Scholar] [CrossRef] [PubMed]
33. Habich, I. Nanosilber in Alltagsmasken: BfR Warnt Vor Ungeklärten Risiken. Available online: https://www.deutsche-apotheker-zeitung.de/news/artikel/2020/08/04/nanosilber-in-alltagsmasken-bfr-warnt-vor-ungeklaerten-risiken (accessed on 17 March 2023).
34. Masken-Rückruf bei Müller: potenziell krebserregendes Anilin nachgewiesen. Available online: https://www.oekotest.de/gesundheit-medikamente/Masken-Rueckruf-bei-Mueller-potenziell-krebserregendes-Anilin-nachgewiesen-_11623_1.html (accessed on 17 March 2023).
35. BfArM: Dringende Sicherheitsinformation—Rückrufbetreffend ViralProtect 7—Monatsmaske Der Farbe Schwarz Grösse M Und L Charge T100406. Available online: https://www.bfarm.de/SharedDocs/Kundeninfos/DE/02/2020/21532-20_kundeninfo_de.pdf?__blob=publicationFile&v=1.
36. Corona-Maske im Rückruf: Hochgiftiger Stoff entdeckt—es besteht Lebensgefahr! Available online: https://www.hna.de/verbraucher/corona-coronavirus-maske-rueckruf-covid-19-mueller-mundschutz-gefahr-gesundheit-kassel-zr-90129285.html (accessed on 17 March 2023).
37. Azoulay, D.; Thomas, J.; Napierska, D.; Ruffinengo, E. Sale and Distribution of Toxic Nanographene Masks on the European Market.
38. Maynard, A. How Safe Are Graphene-Based Face Masks? Edge of Innovation 2021.
39. Information de sécurité—Action de sécurité de Santé publique—ANSM. Available online: https://ansm.sante.fr/informations-de-securite/action-de-securite-de-sante-publique-france-masques-ffp2-particle-filtering-half-mask-labellises-biomass-graphene-shandong-shengquan-new-materials (accessed on 17 March 2023).
40. Government of Canada. Graphene Face Masks—Recalls, Advisories and Safety Alerts—Canada. Available online: https://recalls-rappels.canada.ca/en/alert-recall/graphene-face-masks (accessed on 17 March 2023).
41. La AEMPS informa de los resultados de la investigación efectuada sobre las mascarillas quirúrgicas tipo IIR con grafeno, fabricadas por Shandong Shenquan New Materials Co., Ltd., China. Available online: https://www.aemps.gob.es/informa/la-aemps-informa-de-los-resultados-de-la-investigacion-efectuada-sobre-las-mascarillas-quirurgicas-tipo-iir-con-grafeno-fabricadas-por-shandong-shenquan-new-materials-co-ltd-china/ (accessed on 17 March 2023).
42. Mast, J.; Blaude, M.-N.; Siciliani, L.; Cheyns, K.; Waegeneers, N.; Loco, J.V.; Vleminckx, C.; Verleysen, E. Identification, physicochemical characterisation and preliminary risk analysis of titanum dioxide particles in face masks. Intermediate report TiO₂-Mask COVID-19 project September 2021. Available online: https://www.sciensano.be/en/biblio/identification-physicochemical-characterisation-and-preliminary-risk-analysis-titanium-dioxide-0 (accessed on 17 March 2023).
43. Palmieri, V.; De Maio, F.; De Spirito, M.; Papi, M. Face Masks and Nanotechnology: Keep the Blue Side Up. Nano Today 2021, 37, 101077. [Google Scholar] [CrossRef]
44. Mast, J.; Van Miert, E.; Siciliani, L.; Cheyns, K.; Blaude, M.-N.; Wouters, C.; Waegeneers, N.; Bernsen, R.; Vleminckx, C.; Van Loco, J.; et al. Application of Silver-Based Biocides in Face Masks Intended for General Use Requires Regulatory Control. Sci Total Environ 2023, 870, 161889. [Google Scholar] [CrossRef]
45. PubMed. Available online: https://pubmed.ncbi.nlm.nih.gov/ (accessed on 17 March 2023).
46. Huang, X.; Lin, J.; Demner-Fushman, D. Evaluation of PICO as a Knowledge Representation for Clinical Questions. AMIA Annu Symp Proc 2006, 359–363. [Google Scholar]
47. Calc|LibreOffice—Free Office Suite—Based on OpenOffice—Compatible with Microsoft. Available online: https://www.libreoffice.org/discover/calc (accessed on 17 March 2023).
48. U.S. Environmental Protection Agency. Air Topics. Available online: https://www.epa.gov/environmental-topics/air-topics (accessed on 17 March 2023).
49. What Are the WHO Air Quality Guidelines? Available online: https://www.who.int/news-room/feature-stories/detail/what-are-the-who-air-quality-guidelines (accessed on 17 March 2023).
50. Luft. Available online: https://www.umweltbundesamt.de/themen/luft (accessed on 17 March 2023).
51. Air Quality. Available online: https://environment.ec.europa.eu/topics/air/air-quality_en (accessed on 17 March 2023).
52. Oeko-Tex®. Oeko-Tex Service GmbH, Genferstrasse 23, 8002 Zürich, Switzerland. Available online: https://www.oeko-tex.com/en/our-standards/oeko-tex-standard-100 (accessed on 17 March 2023).
53. LibreOffice—Free Office Suite—Based on OpenOffice—Compatible with Microsoft. Available online: https://www.libreoffice.org/ (accessed on 17 March 2023).
54. Fernández-Arribas, J.; Moreno, T.; Bartrolí, R.; Eljarrat, E. COVID-19 Face Masks: A New Source of Human and Environmental Exposure to Organophosphate Esters. Environment International 2021, 154, 106654. [Google Scholar] [CrossRef] [PubMed]
55. Xie, H.; Han, W.; Xie, Q.; Xu, T.; Zhu, M.; Chen, J. Face Mask—A Potential Source of Phthalate Exposure for Human. Journal of Hazardous Materials 2022, 422, 126848. [Google Scholar] [CrossRef] [PubMed]
56. Xie, H.; Du, J.; Han, W.; Tang, J.; Li, X.; Chen, J. Occurrence and Health Risks of Semi-Volatile Organic Compounds in Face Masks. Science Bulletin 2021, 66, 1601–1603. [Google Scholar] [CrossRef] [PubMed]
57. Rengasamy, S.; Miller, A.; Eimer, B.C.; Shaffer, R.E. Filtration Performance of FDA-Cleared Surgical Masks. J Int Soc Respir Prot 2009, 26, 54–70. [Google Scholar] [PubMed]
58. Roberge, R.J.; Bayer, E.; Powell, J.B.; Coca, A.; Roberge, M.R.; Benson, S.M. Effect of Exhaled Moisture on Breathing Resistance of N95 Filtering Facepiece Respirators. Ann Occup Hyg 2010, 54, 671–677. [Google Scholar] [CrossRef] [PubMed]
59. Zuri, G.; Oró-Nolla, B.; Torres-Agulló, A.; Karanasiau, A.; Lacorte, S. Migration of Microplastics and Phthalates from Face Masks to Water. Molecules 2022, 27, 6859. [Google Scholar] [CrossRef]
60. U.S. Environmental Protection Agency. Risk Assessment Guidance for Superfund (RAGS) Vol 1: Human Health Evaluation Manual, Part A, Interim Final, Office of Emergency and Remedial Response. EPA/540/1-89-002; U.S. Environmental Protection Agency: Washington D.C., 1989. [Google Scholar]
61. Benchetrit, G. Breathing Pattern in Humans: Diversity and Individuality. Respir Physiol 2000, 122, 123–129. [Google Scholar] [CrossRef]
62. Kisielinski, K.; Wagner, S.; Hirsch, O.; Klosterhalfen, B.; Prescher, A. Possible Toxicity of Chronic Carbon Dioxide Exposure Associated with Face Mask Use, Particularly in Pregnant Women, Children and Adolescents—A Scoping Review. Heliyon 2023. [Google Scholar] [CrossRef]
63. Kisielinski, K.; Hirsch, O.; Wagner, S.; Wojtasik, B.; Funken, S.; Klosterhalfen, B.; Kanti Manna, S.; Prescher, A.; Sukul, P.; Sönnichsen, A. Physio-Metabolic and Clinical Consequences of Wearing Face Masks—Systematic Review with Meta-Analysis and Comprehensive Evaluation. Frontiers in Public Health 2023, 11. [Google Scholar] [CrossRef]
64. Chen, X.; Chen, X.; Liu, Q.; Zhao, Q.; Xiong, X.; Wu, C. Used Disposable Face Masks Are Significant Sources of Microplastics to Environment. Environmental Pollution 2021, 285, 117485. [Google Scholar] [CrossRef] [PubMed]
65. Delgado-Gallardo, J.; Sullivan, G.L.; Tokaryk, M.; Russell, J.E.; Davies, G.R.; Johns, K.V.; Hunter, A.P.; Watson, T.M.; Sarp, S. Disposable FFP2 and Type IIR Medical-Grade Face Masks: An Exhaustive Analysis into the Leaching of Micro- and Nanoparticles and Chemical Pollutants Linked to the COVID-19 Pandemic. ACS EST Water 2022, 2, 527–538. [Google Scholar] [CrossRef] [PubMed]
66. Dissanayake, J.; Torres-Quiroz, C.; Mahato, J.; Park, J. Facemasks: A Looming Microplastic Crisis. International Journal of Environmental Research and Public Health 2021, 18, 7068. [Google Scholar] [CrossRef] [PubMed]
67. Liang, H.; Ji, Y.; Ge, W.; Wu, J.; Song, N.; Yin, Z.; Chai, C. Release Kinetics of Microplastics from Disposable Face Masks into the Aqueous Environment. Science of The Total Environment 2022, 816, 151650. [Google Scholar] [CrossRef] [PubMed]
68. Liu, Z.; Wang, J.; Yang, X.; Huang, Q.; Zhu, K.; Sun, Y.; Van Hulle, S.; Jia, H. Generation of Environmental Persistent Free Radicals (EPFRs) Enhances Ecotoxicological Effects of the Disposable Face Mask Waste with the COVID-19 Pandemic. Environmental Pollution 2022, 301, 119019. [Google Scholar] [CrossRef] [PubMed]
69. Meier, P.; Zabara, M.; Hirsch, C.; Gogos, A.; Tscherrig, D.; Richner, G.; Nowack, B.; Wick, P. Evaluation of Fiber and Debris Release from Protective COVID-19 Mask Textiles and in Vitro Acute Cytotoxicity Effects. Environment International 2022, 167, 107364. [Google Scholar] [CrossRef] [PubMed]
70. Sullivan, G.L.; Delgado-Gallardo, J.; Watson, T.M.; Sarp, S. An Investigation into the Leaching of Micro and Nano Particles and Chemical Pollutants from Disposable Face Masks—Linked to the COVID-19 Pandemic. Water Research 2021, 196, 117033. [Google Scholar] [CrossRef]
71. Hui Li, A.S.; Sathishkumar, P.; Selahuddeen, M.L.; Asyraf Wan Mahmood, W.M.; Zainal Abidin, M.H.; Wahab, R.A.; Mohamed Huri, M.A.; Abdullah, F. Adverse Environmental Effects of Disposable Face Masks Due to the Excess Usage. Environmental Pollution 2022, 308, 119674. [Google Scholar] [CrossRef]
72. Kerkeling, S.; Sandten, C.; Schupp, T.; Kreyenschmidt, M. VOC Emissions from Particle Filtering Half Masks—Methods, Risks and Need for Further Action. EXCLI Journal 2021, 20, 995–1008. [Google Scholar] [CrossRef]
73. Min, K.; Weng, X.; Long, P.; Ma, M.; Chen, B.; Yao, S. Rapid In-Situ Analysis of Phthalates in Face Masks by Desorption Corona Beam Ionization Tandem Mass Spectrometry. Talanta 2021, 231, 122359. [Google Scholar] [CrossRef]
74. Wang, X.; Okoffo, E.D.; Banks, A.P.; Li, Y.; Thomas, K.V.; Rauert, C.; Aylward, L.L.; Mueller, J.F. Phthalate Esters in Face Masks and Associated Inhalation Exposure Risk. Journal of Hazardous Materials 2022, 423, 127001. [Google Scholar] [CrossRef] [PubMed]
75. Vimalkumar, K.; Zhu, H.; Kannan, K. Widespread Occurrence of Phthalate and Non-Phthalate Plasticizers in Single-Use Facemasks Collected in the United States. Environment International 2022, 158, 106967. [Google Scholar] [CrossRef] [PubMed]
76. Bussan, D.D.; Snaychuk, L.; Bartzas, G.; Douvris, C. Quantification of Trace Elements in Surgical and KN95 Face Masks Widely Used during the SARS-COVID-19 Pandemic. Science of The Total Environment 2022, 814, 151924. [Google Scholar] [CrossRef] [PubMed]
77. Verleysen, E.; Ledecq, M.; Siciliani, L.; Cheyns, K.; Vleminckx, C.; Blaude, M.-N.; De Vos, S.; Brassinne, F.; Van Steen, F.; Nkenda, R.; et al. Titanium Dioxide Particles Frequently Present in Face Masks Intended for General Use Require Regulatory Control. Sci Rep 2022, 12, 2529. [Google Scholar] [CrossRef] [PubMed]
78. Huang, D.; Tao, J.; Cheng, M.; Deng, R.; Chen, S.; Yin, L.; Li, R. Microplastics and Nanoplastics in the Environment: Macroscopic Transport and Effects on Creatures. Journal of Hazardous Materials 2021, 407, 124399. [Google Scholar] [CrossRef] [PubMed]
79. Aragaw, T.A. Surgical Face Masks as a Potential Source for Microplastic Pollution in the COVID-19 Scenario. Marine Pollution Bulletin 2020, 159, 111517. [Google Scholar] [CrossRef] [PubMed]
80. Fadare, O.O.; Okoffo, E.D. Covid-19 Face Masks: A Potential Source of Microplastic Fibers in the Environment. Sci Total Environ 2020, 737, 140279. [Google Scholar] [CrossRef]
81. Hasan, N.A.; Heal, R.D.; Bashar, A.; Haque, M.M. Face Masks: Protecting the Wearer but Neglecting the Aquatic Environment?—A Perspective from Bangladesh. Environmental Challenges 2021, 4, 100126. [Google Scholar] [CrossRef]
82. Parashar, N.; Hait, S. Plastics in the Time of COVID-19 Pandemic: Protector or Polluter? Science of The Total Environment 2021, 759, 144274. [Google Scholar] [CrossRef]
83. Xu, E.G.; Ren, Z.J. Preventing Masks from Becoming the next Plastic Problem. Front Environ Sci Eng 2021, 15, 125. [Google Scholar] [CrossRef]
84. Hutten, I.M. CHAPTER 5—Processes for Nonwoven Filter Media. In Handbook of Nonwoven Filter Media; Hutten, I.M., Ed.; Butterworth-Heinemann: Oxford, 2007; pp. 195–244. ISBN 978-1-85617-441-1. [Google Scholar]
85. Prata, J.C.; Silva, A.L.P.; da Costa, J.P.; Mouneyrac, C.; Walker, T.R.; Duarte, A.C.; Rocha-Santos, T. Solutions and Integrated Strategies for the Control and Mitigation of Plastic and Microplastic Pollution. International Journal of Environmental Research and Public Health 2019, 16, 2411. [Google Scholar] [CrossRef] [PubMed]
86. Tesfaldet, Y.T.; Ndeh, N.T. Public Face Masks Wearing during the COVID-19 Pandemic: A Comprehensive Analysis Is Needed for Potential Implications. Journal of Hazardous Materials Advances 2022, 7, 100125. [Google Scholar] [CrossRef] [PubMed]
87. Patel, A.; D’Alessandro, M.M.; Ireland, K.J.; Burel, W.G.; Wencil, E.B.; Rasmussen, S.A. Personal Protective Equipment Supply Chain: Lessons Learned from Recent Public Health Emergency Responses. Health Security 2017, 15, 244–252. [Google Scholar] [CrossRef] [PubMed]
88. Du, H.; Huang, S.; Wang, J. Environmental Risks of Polymer Materials from Disposable Face Masks Linked to the COVID-19 Pandemic. Science of The Total Environment 2022, 815, 152980. [Google Scholar] [CrossRef] [PubMed]
89. Han, J.; He, S. Need for Assessing the Inhalation of Micro(Nano)Plastic Debris Shed from Masks, Respirators, and Home-Made Face Coverings during the COVID-19 Pandemic. Environmental Pollution 2021, 268, 115728. [Google Scholar] [CrossRef] [PubMed]
90. Buzzin, A.; Domènech-Gil, G.; Fraschetti, E.; Giovine, E.; Puglisi, D.; Caputo, D. Assessing the Consequences of Prolonged Usage of Disposable Face Masks. Sci Rep 2022, 12, 16796. [Google Scholar] [CrossRef] [PubMed]
91. Gaston, E.; Woo, M.; Steele, C.; Sukumaran, S.; Anderson, S. Microplastics Differ Between Indoor and Outdoor Air Masses: Insights from Multiple Microscopy Methodologies. Appl Spectrosc 2020, 74, 1079–1098. [Google Scholar] [CrossRef]
92. Liu, K.; Wang, X.; Fang, T.; Xu, P.; Zhu, L.; Li, D. Source and Potential Risk Assessment of Suspended Atmospheric Microplastics in Shanghai. Science of The Total Environment 2019, 675, 462–471. [Google Scholar] [CrossRef]
93. Dris, R.; Gasperi, J.; Mirande, C.; Mandin, C.; Guerrouache, M.; Langlois, V.; Tassin, B. A First Overview of Textile Fibers, Including Microplastics, in Indoor and Outdoor Environments. Environmental Pollution 2017, 221, 453–458. [Google Scholar] [CrossRef]
94. Yee, M.S.-L.; Hii, L.-W.; Looi, C.K.; Lim, W.-M.; Wong, S.-F.; Kok, Y.-Y.; Tan, B.-K.; Wong, C.-Y.; Leong, C.-O. Impact of Microplastics and Nanoplastics on Human Health. Nanomaterials 2021, 11, 496. [Google Scholar] [CrossRef]
95. Cox, K.D.; Covernton, G.A.; Davies, H.L.; Dower, J.F.; Juanes, F.; Dudas, S.E. Human Consumption of Microplastics. Environ. Sci. Technol. 2019, 53, 7068–7074. [Google Scholar] [CrossRef] [PubMed]
96. Dehghani, S.; Moore, F.; Akhbarizadeh, R. Microplastic Pollution in Deposited Urban Dust, Tehran Metropolis, Iran. Environ Sci Pollut Res 2017, 24, 20360–20371. [Google Scholar] [CrossRef]
97. Abbasi, S.; Jaafarzadeh, N.; Zahedi, A.; Ravanbakhsh, M.; Abbaszadeh, S.; Turner, A. Microplastics in the Atmosphere of Ahvaz City, Iran. Journal of Environmental Sciences 2023, 126, 95–102. [Google Scholar] [CrossRef] [PubMed]
98. U.S. Environmental Protection Agency. Setting and Reviewing Standards to Control Particulate Matter (PM) Pollution. Available online: https://www.epa.gov/pm-pollution/setting-and-reviewing-standards-control-particulate-matter-pm-pollution (accessed on 18 March 2023).
99. Kelly, F.J.; Fussell, J.C. Size, Source and Chemical Composition as Determinants of Toxicity Attributable to Ambient Particulate Matter. Atmospheric Environment 2012, 60, 504–526. [Google Scholar] [CrossRef]
100. Wieland, S.; Balmes, A.; Bender, J.; Kitzinger, J.; Meyer, F.; Ramsperger, A.F.; Roeder, F.; Tengelmann, C.; Wimmer, B.H.; Laforsch, C.; et al. From Properties to Toxicity: Comparing Microplastics to Other Airborne Microparticles. Journal of Hazardous Materials 2022, 428, 128151. [Google Scholar] [CrossRef] [PubMed]
101. Allegri, M.; Bianchi, M.G.; Chiu, M.; Varet, J.; Costa, A.L.; Ortelli, S.; Blosi, M.; Bussolati, O.; Poland, C.A.; Bergamaschi, E. Shape-Related Toxicity of Titanium Dioxide Nanofibres. PLOS ONE 2016, 11, e0151365. [Google Scholar] [CrossRef] [PubMed]
102. Peltonen, L.; Hirvonen, J. Physicochemical Characterization of Nano- and Microparticles. Current Nanoscience 2008, 4, 101–107. [Google Scholar] [CrossRef]
103. Silva, T.; Pokhrel, L.R.; Dubey, B.; Tolaymat, T.M.; Maier, K.J.; Liu, X. Particle Size, Surface Charge and Concentration Dependent Ecotoxicity of Three Organo-Coated Silver Nanoparticles: Comparison between General Linear Model-Predicted and Observed Toxicity. Science of The Total Environment 2014, 468–469, 968–976. [Google Scholar] [CrossRef]
104. Sun, K.; Song, Y.; He, F.; Jing, M.; Tang, J.; Liu, R. A Review of Human and Animals Exposure to Polycyclic Aromatic Hydrocarbons: Health Risk and Adverse Effects, Photo-Induced Toxicity and Regulating Effect of Microplastics. Science of The Total Environment 2021, 773, 145403. [Google Scholar] [CrossRef]
105. Rahman, A.; Sarkar, A.; Yadav, O.P.; Achari, G.; Slobodnik, J. Potential Human Health Risks Due to Environmental Exposure to Nano- and Microplastics and Knowledge Gaps: A Scoping Review. Science of The Total Environment 2021, 757, 143872. [Google Scholar] [CrossRef]
106. World Health Organization (WHO). WHO Global Air Quality Guidelines. Particulate Matter (PM_2.5 and PM₁₀), Ozone, Nitrogen Dioxide, Sulfur Dioxide and Carbon Monoxide 2021.
107. Donaldson, K.; Seaton, A. A Short History of the Toxicology of Inhaled Particles. Part Fibre Toxicol 2012, 9, 13. [Google Scholar] [CrossRef] [PubMed]
108. Riediker, M.; Zink, D.; Kreyling, W.; Oberdörster, G.; Elder, A.; Graham, U.; Lynch, I.; Duschl, A.; Ichihara, G.; Ichihara, S.; et al. Particle Toxicology and Health—Where Are We? Part Fibre Toxicol 2019, 16, 19. [Google Scholar] [CrossRef] [PubMed]
109. Kisielinski, K.; Mumme, T.; Reinartz, P.; Buell, U. FDG-PET Detects Foreign-Body Reactions to Polyethylene Wear Debris in Non-Infected Knee Endoprostheses. Nuklearmedizin 2004, 43, N3–N6. [Google Scholar]
110. Kisielinski, K.; Cremerius, U.; Büll, U.; Hermanns, B.; Wirtz, D.C.; Niethard, F.U. [First experiences with fluorodeoxyglucose-positron-emission tomography (FDG-PET) in the evaluation of painful total knee and hip joint replacements]. Z Orthop Ihre Grenzgeb 2003, 141, 153–159. [Google Scholar] [CrossRef]
111. Kisielinski, K.; Cremerius, U.; Reinartz, P.; Niethard, F.U. Fluordeoxyglucose Positron Emission Tomography Detection of Inflammatory Reactions Due to Polyethylene Wear in Total Hip Arthroplasty. The Journal of Arthroplasty 2003, 18, 528–532. [Google Scholar] [CrossRef]
112. Klosterhalfen, B.; Junge, K.; Klinge, U. The Lightweight and Large Porous Mesh Concept for Hernia Repair. Expert Rev Med Devices 2005, 2, 103–117. [Google Scholar] [CrossRef]
113. Klinge, U.; Klosterhalfen, B. Mesh Implants for Hernia Repair: An Update. Expert Review of Medical Devices 2018, 15, 735–746. [Google Scholar] [CrossRef]
114. Gasperi, J.; Wright, S.L.; Dris, R.; Collard, F.; Mandin, C.; Guerrouache, M.; Langlois, V.; Kelly, F.J.; Tassin, B. Microplastics in Air: Are We Breathing It In? Current Opinion in Environmental Science & Health 2018, 1, 1–5. [Google Scholar] [CrossRef]
115. Howie, R.M.; Addison, J.; Cherrie, J.; Robertson, A.; Dodgson, J. Fibre release from filtering facepiece respiators. The Annals of Occupational Hygiene 1986, 30, 131–133. [Google Scholar] [CrossRef]
116. Prata, J.C. Airborne Microplastics: Consequences to Human Health? Environmental Pollution 2018, 234, 115–126. [Google Scholar] [CrossRef]
117. Baeza-Martínez, C.; Olmos, S.; González-Pleiter, M.; López-Castellanos, J.; García-Pachón, E.; Masiá-Canuto, M.; Hernández-Blasco, L.; Bayo, J. First Evidence of Microplastics Isolated in European Citizens’ Lower Airway. Journal of Hazardous Materials 2022, 438, 129439. [Google Scholar] [CrossRef] [PubMed]
118. Jenner, L.C.; Rotchell, J.M.; Bennett, R.T.; Cowen, M.; Tentzeris, V.; Sadofsky, L.R. Detection of Microplastics in Human Lung Tissue Using ΜFTIR Spectroscopy. Science of The Total Environment 2022, 831, 154907. [Google Scholar] [CrossRef] [PubMed]
119. Almeida, A.S.R.; de Souza, C.B. The Impact of Microplastic on Human Health. Current Biotechnology 2021, 10, 158–167. [Google Scholar] [CrossRef]
120. Kutralam-Muniasamy, G.; Shruti, V.C.; Pérez-Guevara, F.; Roy, P.D. Microplastic Diagnostics in Humans: “The 3Ps” Progress, Problems, and Prospects. Science of The Total Environment 2023, 856, 159164. [Google Scholar] [CrossRef] [PubMed]
121. Prata, J.C.; da Costa, J.P.; Lopes, I.; Duarte, A.C.; Rocha-Santos, T. Environmental Exposure to Microplastics: An Overview on Possible Human Health Effects. Science of The Total Environment 2020, 702, 134455. [Google Scholar] [CrossRef] [PubMed]
122. Lee, H.P.; Wang, D.Y. Objective Assessment of Increase in Breathing Resistance of N95 Respirators on Human Subjects. Ann Occup Hyg 2011, 55, 917–921. [Google Scholar] [CrossRef]
123. Thomas, R.J. Particle Size and Pathogenicity in the Respiratory Tract. Virulence 2013, 4, 847–858. [Google Scholar] [CrossRef]
124. Heyder, J.; Gebhart, J.; Rudolf, G.; Schiller, C.F.; Stahlhofen, W. Deposition of Particles in the Human Respiratory Tract in the Size Range 0.005–15 Μm. Journal of Aerosol Science 1986, 17, 811–825. [Google Scholar] [CrossRef]
125. Human Respiratory Tract Model for Radiological Protection. A Report of a Task Group of the International Commission on Radiological Protection. Ann ICRP 1994, 24, 1–482. [Google Scholar]
126. Everard, M.L.; Hardy, J.G.; Milner, A.D. Comparison of Nebulised Aerosol Deposition in the Lungs of Healthy Adults Following Oral and Nasal Inhalation. Thorax 1993, 48, 1045–1046. [Google Scholar] [CrossRef]
127. Barnoya, J.; Glantz, S.A. Cardiovascular Effects of Secondhand Smoke. Circulation 2005, 111, 2684–2698. [Google Scholar] [CrossRef]
128. Leslie, H.A.; van Velzen, M.J.M.; Brandsma, S.H.; Vethaak, A.D.; Garcia-Vallejo, J.J.; Lamoree, M.H. Discovery and Quantification of Plastic Particle Pollution in Human Blood. Environment International 2022, 163, 107199. [Google Scholar] [CrossRef]
129. Kannan, K.; Vimalkumar, K. A Review of Human Exposure to Microplastics and Insights Into Microplastics as Obesogens. Frontiers in Endocrinology 2021, 12. [Google Scholar] [CrossRef]
130. World Health Organization. Regional Office for Europe. Noncommunicable Diseases and Air Pollution: WHO European High-Level Conference on Noncommunicable Diseases: Time to Deliver—Meeting NCD Targets to Achieve Sustainable Development Goals in Europe: 9–10 April 2019, Ashgabat, Turkmenistan; World Health Organization. Regional Office for Europe, 2019. [Google Scholar]
131. WHO Air Quality Guidelines Global Update 2005 Report on a Working Group Meeting, Bonn, Germany, 2005.
132. Chen, J.; Hoek, G. Long-Term Exposure to PM and All-Cause and Cause-Specific Mortality: A Systematic Review and Meta-Analysis. Environ Int 2020, 143, 105974. [Google Scholar] [CrossRef] [PubMed]
133. Orellano, P.; Reynoso, J.; Quaranta, N.; Bardach, A.; Ciapponi, A. Short-Term Exposure to Particulate Matter (PM₁₀ and PM_2.5), Nitrogen Dioxide (NO₂), and Ozone (O₃) and All-Cause and Cause-Specific Mortality: Systematic Review and Meta-Analysis. Environment International 2020, 142, 105876. [Google Scholar] [CrossRef] [PubMed]
134. Sangkham, S.; Faikhaw, O.; Munkong, N.; Sakunkoo, P.; Arunlertaree, C.; Chavali, M.; Mousazadeh, M.; Tiwari, A. A Review on Microplastics and Nanoplastics in the Environment: Their Occurrence, Exposure Routes, Toxic Studies, and Potential Effects on Human Health. Marine Pollution Bulletin 2022, 181, 113832. [Google Scholar] [CrossRef] [PubMed]
135. Lai, H.; Liu, X.; Qu, M. Nanoplastics and Human Health: Hazard Identification and Biointerface. Nanomaterials 2022, 12, 1298. [Google Scholar] [CrossRef]
136. Kwak, J.I.; An, Y.-J. Post COVID-19 Pandemic: Biofragmentation and Soil Ecotoxicological Effects of Microplastics Derived from Face Masks. Journal of Hazardous Materials 2021, 416, 126169. [Google Scholar] [CrossRef]
137. Li, S.; Wang, Q.; Yu, H.; Yang, L.; Sun, Y.; Xu, N.; Wang, N.; Lei, Z.; Hou, J.; Jin, Y.; et al. Polystyrene Microplastics Induce Blood–Testis Barrier Disruption Regulated by the MAPK-Nrf2 Signaling Pathway in Rats. Environ Sci Pollut Res 2021, 28, 47921–47931. [Google Scholar] [CrossRef]
138. Campanale, C.; Massarelli, C.; Savino, I.; Locaputo, V.; Uricchio, V.F. A Detailed Review Study on Potential Effects of Microplastics and Additives of Concern on Human Health. International Journal of Environmental Research and Public Health 2020, 17, 1212. [Google Scholar] [CrossRef]
139. Kisielinski, K.; Wojtasik, B.; Kisielinski, K.; Wojtasik, B. Suitability of Rose Bengal Sodium Salt Staining for Visualisation of Face Mask Contamination by Living Organisms. AIMSES 2022, 9, 218–231. [Google Scholar] [CrossRef]
140. Fögen, Z. The Foegen Effect: A Mechanism by Which Facemasks Contribute to the COVID-19 Case Fatality Rate. Medicine (Baltimore) 2022, 101, e28924. [Google Scholar] [CrossRef] [PubMed]
141. Spira, B. Correlation Between Mask Compliance and COVID-19 Outcomes in Europe. Cureus 2022, 14, e24268. [Google Scholar] [CrossRef] [PubMed]
142. Cengiz, C.; Can, İ.H. The Effect of N95 and Surgical Masks on Mucociliary Clearance Function and Sinonasal Complaints. Eur Arch Otorhinolaryngol 2022, 279, 759–764. [Google Scholar] [CrossRef] [PubMed]
143. Tenenbaum, T.; Doenhardt, M.; Diffloth, N.; Berner, R.; Armann, J.P. High Burden of RSV Hospitalizations in Germany 2021–2022. Infection 2022, 50, 1587–1590. [Google Scholar] [CrossRef] [PubMed]
144. Ma, K.C. Increase in Acute Respiratory Illnesses Among Children and Adolescents Associated with Rhinoviruses and Enteroviruses, Including Enterovirus D68—United States, July–September 2022. MMWR Morb Mortal Wkly Rep 2022, 71. [Google Scholar] [CrossRef] [PubMed]
145. New COVID-19 Cases Worldwide. Available online: https://coronavirus.jhu.edu/data/new-cases (accessed on 1 February 2023).
146. Fearnley, L.; Wu, X. Beyond Asian ‘Mask Culture’: Understanding the Ethics of Face Masks during the Covid-19 Pandemic in Singapore. Critical Public Health 2022, 0, 1–12. [Google Scholar] [CrossRef]
147. Brohi, R.D.; Wang, L.; Talpur, H.S.; Wu, D.; Khan, F.A.; Bhattarai, D.; Rehman, Z.-U.; Farmanullah, F.; Huo, L.-J. Toxicity of Nanoparticles on the Reproductive System in Animal Models: A Review. Frontiers in Pharmacology 2017, 8. [Google Scholar] [CrossRef]
148. Bonner, J.C. Nanoparticles as a Potential Cause of Pleural and Interstitial Lung Disease. Proc Am Thorac Soc 2010, 7, 138–141. [Google Scholar] [CrossRef]
149. Hansen, T.; Clermont, G.; Alves, A.; Eloy, R.; Brochhausen, C.; Boutrand, J.P.; Gatti, A.M.; James Kirkpatrick, C. Biological Tolerance of Different Materials in Bulk and Nanoparticulate Form in a Rat Model: Sarcoma Development by Nanoparticles. Journal of The Royal Society Interface 2006, 3, 767–775. [Google Scholar] [CrossRef]
150. Rowan, D.D. Volatile Metabolites. Metabolites 2011, 1, 41–63. [Google Scholar] [CrossRef] [PubMed]
151. Shrubsole, C.; Dimitroulopoulou, S.; Foxall, K.; Gadeberg, B.; Doutsi, A. IAQ Guidelines for Selected Volatile Organic Compounds (VOCs) in the UK. Building and Environment 2019, 165, 106382. [Google Scholar] [CrossRef]
152. U.S. Environmental Protection Agency. Consumer Products: National Volatile Organic Compound Emission Standards. Available online: https://www.epa.gov/stationary-sources-air-pollution/consumer-products-national-volatile-organic-compound-emission (accessed on 18 March 2023).
153. Salthammer, T. TVOC—Revisited. Environment International 2022, 167, 107440. [Google Scholar] [CrossRef] [PubMed]
154. Oeko-Tex^® Standard 100 2023.
155. World Health Organization. Occupational and Environmental Health Team. In Guidelines for air quality; World Health Organization, 2000. [Google Scholar]
156. World Health Organization. Regional Office for Europe. WHO Guidelines for Indoor Air Quality: Selected Pollutants; World Health Organization. Regional Office for Europe, 2010; ISBN 978-92-890-0213-4. [Google Scholar]
157. Tsai, W.-T. An Overview of Health Hazards of Volatile Organic Compounds Regulated as Indoor Air Pollutants. Reviews on Environmental Health 2019, 34, 81–89. [Google Scholar] [CrossRef] [PubMed]
158. Fromme, H.; Debiak, M.; Sagunski, H.; Röhl, C.; Kraft, M.; Kolossa-Gehring, M. The German Approach to Regulate Indoor Air Contaminants. International Journal of Hygiene and Environmental Health 2019, 222, 347–354. [Google Scholar] [CrossRef] [PubMed]
159. Seifert, B. Richtwerte für die Innenraumluft. In Bundesgesundheitsblatt Gesundheitsforschung Gesundheitsschutz; Springer: Berlin, Heidelberg, 1999; pp. 270–278. ISBN 978-3-662-38283-7. [Google Scholar]
160. Mølhave, L.; Clausen, G.; Berglund, B.; De Ceaurriz, J.; Kettrup, A.; Lindvall, T.; Maroni, M.; Pickering, A.C.; Risse, U.; Rothweiler, H.; et al. Total Volatile Organic Compounds (TVOC) in Indoor Air Quality Investigations*. Indoor Air 1997, 7, 225–240. [Google Scholar] [CrossRef]
161. Tedd Nathanson, Federal-Provincial Advisory Committee on Environmental and Occupational Health (Canada). Indoor Air Quality in Office Buildings: A Technical Guide: A Report of the Federal-Provincial Advisory Committee on Environmental and Occupational Health. H46-2/93-166Erev-PDF—Government of Canada Publications—Canada. 2002. [Google Scholar]
162. Tuomi, T.; Vainiotalo, S. The Guideline and Target Values for Total Volatile Organic Compound Concentrations in Industrial Indoor Environments in Finland. Indoor and Built Environment 2016, 25, 424–434. [Google Scholar] [CrossRef]
163. Jantunen, M.; Jaakkola, J.J.K.; Krzyzanowski, M. Assessment of Exposure to Indoor Air Pollutants; World Health Organization. Regional Office for Europe, 1997; ISBN 978-92-890-1342-0. [Google Scholar]
164. Umweltbundesamt Beurteilung von Innenraumluftkontaminationen mittels Referenz- und Richtwerten. Bundesgesundheitsbl 2007, 50, 990–1005. [CrossRef]
165. Umweltbundesamt Ausschuss zur gesundheitlichen Bewertung von Bauprodukten. Available online: https://www.umweltbundesamt.de/themen/gesundheit/kommissionen-arbeitsgruppen/ausschuss-zur-gesundheitlichen-bewertung-von (accessed on 19 March 2023).
166. US EPA National Center for Environmental Assessment. R.T.P.N. IRIS Toxicological Review of Acrolein (2003 Final). Available online: https://cfpub.epa.gov/ncea/iris_drafts/recordisplay.cfm?deid=51977 (accessed on 19 March 2023).
167. US EPA National Center for Environmental Assessment. Acrolein; CASRN 107-02-8 2003.
168. Bayati, M.; Vu, D.C.; Vo, P.H.; Rogers, E.; Park, J.; Ho, T.L.; Davis, A.N.; Gulseven, Z.; Carlo, G.; Palermo, F.; et al. Health Risk Assessment of Volatile Organic Compounds at Daycare Facilities. Indoor Air 2021, 31, 977–988. [Google Scholar] [CrossRef] [PubMed]
169. Yang, Y.; Chen, P.; Ma, S.; Lu, S.; Yu, Y.; An, T. A Critical Review of Human Internal Exposure and the Health Risks of Organophosphate Ester Flame Retardants and Their Metabolites. Critical Reviews in Environmental Science and Technology 2022, 52, 1528–1560. [Google Scholar] [CrossRef]
170. US EPA. Regional Screening Levels (RSLs)—Generic Tables. Available online: https://www.epa.gov/risk/regional-screening-levels-rsls-generic-tables (accessed on 19 March 2023).
171. Regulation (EC) No 1272/2008 of the European Parliament and of the Council of 16 December 2008 on Classification, Labelling and Packaging of Substances and Mixtures, Amending and Repealing Directives 67/548/EEC and 1999/45/EC, and Amending Regulation (EC) No 1907/2006 (Text with EEA Relevance); 2008; Volume 353.
172. He, C.; Lin, C.-Y.; Mueller, J.F. Chapter Ten—Organophosphate Flame Retardants in the Environment: Source, Occurrence, and Human Exposure. In Comprehensive Analytical Chemistry; Emerging Halogenated Flame Retardants in the Environment; Oh, J.-E., Ed.; Elsevier, 2020; Volume 88, pp. 341–365. [Google Scholar]
173. Huang, Y.; Law, J.C.-F.; Lam, T.-K.; Leung, K.S.-Y. Risks of Organic UV Filters: A Review of Environmental and Human Health Concern Studies. Science of The Total Environment 2021, 755, 142486. [Google Scholar] [CrossRef] [PubMed]
174. Jesus, A.; Sousa, E.; Cruz, M.T.; Cidade, H.; Lobo, J.M.S.; Almeida, I.F. UV Filters: Challenges and Prospects. Pharmaceuticals 2022, 15, 263. [Google Scholar] [CrossRef]
175. Commission Regulation (EU) No. 126/2013 Amending Annex XVII to Regulation (EC) No. 1907/2006 of the European Parliament and of the Council on the Registration, Evaluation, Authorisation and Restriction of Chemicals (REACH).|FAOLEX. Available online: https://www.fao.org/faolex/results/details/en/c/LEX-FAOC120590/ (accessed on 19 March 2023).
176. Wang, Y.; Qian, H. Phthalates and Their Impacts on Human Health. Healthcare 2021, 9, 603. [Google Scholar] [CrossRef] [PubMed]
177. Polycyclic Aromatic Hydrocarbons (PAHs): What Are the Standards and Regulations for PAHs Exposure?|Environmental Medicine|ATSDR. Available online: https://www.atsdr.cdc.gov/csem/polycyclic-aromatic-hydrocarbons/standards_and_regulations_for_exposure.html (accessed on 19 March 2023).
178. Directive 2004/37/EC of the European Parliament and of the Council of 29 April 2004 on the Protection of Workers from the Risks Related to Exposure to Carcinogens or Mutagens at Work (Sixth Individual Directive within the Meaning of Article 16(1) of Council Directive 89/391/EEC) (Codified Version) (Text with EEA Relevance); 2014.
179. Bukowska, B.; Mokra, K.; Michałowicz, J. Benzo[a]Pyrene—Environmental Occurrence, Human Exposure, and Mechanisms of Toxicity. International Journal of Molecular Sciences 2022, 23, 6348. [Google Scholar] [CrossRef] [PubMed]
180. Sunderland, E.M.; Hu, X.C.; Dassuncao, C.; Tokranov, A.K.; Wagner, C.C.; Allen, J.G. A Review of the Pathways of Human Exposure to Poly- and Perfluoroalkyl Substances (PFASs) and Present Understanding of Health Effects. J Expo Sci Environ Epidemiol 2019, 29, 131–147. [Google Scholar] [CrossRef]
181. US EPA. Questions and Answers: Drinking Water Health Advisories for PFOA, PFOS, GenX Chemicals and PFBS. Available online: https://www.epa.gov/sdwa/questions-and-answers-drinking-water-health-advisories-pfoa-pfos-genx-chemicals-and-pfbs (accessed on 19 March 2023).
182. Per- and Polyfluoroalkyl Substances (PFASs)—ECHA. Available online: https://echa.europa.eu/hot-topics/perfluoroalkyl-chemicals-pfas (accessed on 19 March 2023).
183. Directive (EU) 2020/2184 of the European Parliament and of the Council of 16 December 2020 on the Quality of Water Intended for Human Consumption (Recast) (Text with EEA Relevance); 2020; Volume 435.
184. Jensen, A.A.; Warming, M. Short-Chain Polyfluoroalkyl Substances (PFAS). A Literature Review of Information on Human Health Effects and Environmental Fate and Effect Aspects of Short-Chain PFAS; Danish Environmental Protection Agency, 2015. [Google Scholar]
185. Forouzandeh, P.; O’Dowd, K.; Pillai, S.C. Face Masks and Respirators in the Fight against the COVID-19 Pandemic: An Overview of the Standards and Testing Methods. Saf Sci 2021, 133, 104995. [Google Scholar] [CrossRef]
186. Calculating Hazard Quotients and Cancer Risk Estimates. Available online: https://www.atsdr.cdc.gov/pha-guidance/conducting_scientific_evaluations/epcs_and_exposure_calculations/hazardquotients_cancerrisk.html (accessed on 19 March 2023).
187. US EPA. Guidelines for Carcinogen Risk Assessment 2005.
188. ANSES Dioxyde de titane sous forme nanoparticulaire: recommandation de valeurs limites d’exposition professionnelle. Available online: https://www.anses.fr/fr/content/dioxyde-de-titane-sous-forme-nanoparticulaire-recommandation-de-valeurs-limites-d%E2%80%99exposition (accessed on 19 March 2023).
189. ANSES Valeurs Limites d’exposition En Milieu Professionnel Le Dioxyde de Titane Sous Forme Nanométrique (TiO₂-NP, P25). Rapport d’expertise Collective, Décembre 2020—Expertise Scientifique. Saisine N° 2019-SA-0109—LEP TiO₂-NP 2019.
190. Bermudez, E.; Mangum, J.B.; Wong, B.A.; Asgharian, B.; Hext, P.M.; Warheit, D.B.; Everitt, J.I. Pulmonary Responses of Mice, Rats, and Hamsters to Subchronic Inhalation of Ultrafine Titanium Dioxide Particles. Toxicol Sci 2004, 77, 347–357. [Google Scholar] [CrossRef] [PubMed]
191. Zannoni, N.; Lakey, P.S.J.; Won, Y.; Shiraiwa, M.; Rim, D.; Weschler, C.J.; Wang, N.; Ernle, L.; Li, M.; Bekö, G.; et al. The Human Oxidation Field. Science 2022, 377, 1071–1077. [Google Scholar] [CrossRef]
192. World Health Organization. Mask Use in the Context of COVID-19: Interim Guidance, 1 December 2020. 2020. [Google Scholar]
193. Jefferson, T.; Dooley, L.; Ferroni, E.; Al-Ansary, L.A.; Driel, M.L.; van Bawazeer, G.A.; Jones, M.A.; Hoffmann, T.C.; Clark, J.; Beller, E.M.; et al. Physical Interventions to Interrupt or Reduce the Spread of Respiratory Viruses. Cochrane Database of Systematic Reviews 2023. [Google Scholar] [CrossRef]
194. Huckelba, A.L.; Van Lange, P.A.M. The Silent Killer: Consequences of Climate Change and How to Survive Past the Year 2050. Sustainability 2020, 12, 3757. [Google Scholar] [CrossRef]
195. Zaynab, M.; Fatima, M.; Sharif, Y.; Sughra, K.; Sajid, M.; Khan, K.A.; Sneharani, A.H.; Li, S. Health and Environmental Effects of Silent Killers Organochlorine Pesticides and Polychlorinated Biphenyl. Journal of King Saud University - Science 2021, 33, 101511. [Google Scholar] [CrossRef]
196. Nawrot, T.S.; Staessen, J.A. Low-Level Environmental Exposure to Lead Unmasked as Silent Killer. Circulation 2006, 114, 1347–1349. [Google Scholar] [CrossRef] [PubMed]
197. Alasfar, R.H.; Isaifan, R.J. Aluminum Environmental Pollution: The Silent Killer. Environ Sci Pollut Res 2021, 28, 44587–44597. [Google Scholar] [CrossRef]
198. Shaldon, S.; Vienken, J. Beyond The Current Paradigm: Recent Advances in The Understanding of Sodium Handling - Guest Editors: Stanley Shaldon and Joerg Vienken: Salt, the Neglected Silent Killer. Seminars in Dialysis 2009, 22, 264–266. [Google Scholar] [CrossRef]
199. Houston, T.P. The Silent Killer: Environmental Tobacco Smoke. J Fam Pract 1991, 32, 457–458. [Google Scholar]
200. Redlich, C.A.; Sparer, J.; Cullen, M.R. Sick-Building Syndrome. Lancet 1997, 349, 1013–1016. [Google Scholar] [CrossRef] [PubMed]
201. Directorate-General for Health and Consumers (European Commission) Now known as Making Risk Assessment More Relevant for Risk Management. Publications Office of the European Union: LU, 2013; ISBN 978-92-79-31205-2.
202. World Health Organization (WHO). WHO—Advice on the Use of Masks in the Context of COVID-19: Interim Guidance, 5 June 2020. 2020. [Google Scholar]
203. Mitteilungen der Ad-hoc-Arbeitsgruppe Innenraumrichtwerte der Innenraumlufthygiene-Kommission des Umweltbundesamtes und der Obersten Landesgesundheitsbehörden [Health evaluation of fine particulate matter in indoor air]. Bundesgesundheitsblatt Gesundheitsforschung Gesundheitsschutz 2008, 51, 1370–1378. [CrossRef]
204. Directive 2008/50/EC of the European Parliament and of the Council of 21 May 2008 on Ambient Air Quality and Cleaner Air for Europe; 2008; Volume 152.
205. Delanghe, L.; Cauwenberghs, E.; Spacova, I.; De Boeck, I.; Van Beeck, W.; Pepermans, K.; Claes, I.; Vandenheuvel, D.; Verhoeven, V.; Lebeer, S. Cotton and Surgical Face Masks in Community Settings: Bacterial Contamination and Face Mask Hygiene. Front Med (Lausanne) 2021, 8, 732047. [Google Scholar] [CrossRef] [PubMed]
206. Sachdev, R.; Garg, K.; Singh, G.; Mehrotra, V. Is Safeguard Compromised? Surgical Mouth Mask Harboring Hazardous Microorganisms in Dental Practice. J Family Med Prim Care 2020, 9, 759–763. [Google Scholar] [CrossRef]
207. Luksamijarulkul, P.; Aiempradit, N.; Vatanasomboon, P. Microbial Contamination on Used Surgical Masks among Hospital Personnel and Microbial Air Quality in Their Working Wards: A Hospital in Bangkok. Oman Med J 2014, 29, 346–350. [Google Scholar] [CrossRef]
208. Park, A.-M.; Khadka, S.; Sato, F.; Omura, S.; Fujita, M.; Hashiwaki, K.; Tsunoda, I. Bacterial and Fungal Isolation from Face Masks under the COVID-19 Pandemic. Sci Rep 2022, 12, 11361. [Google Scholar] [CrossRef]
209. Zhiqing, L.; Yongyun, C.; Wenxiang, C.; Mengning, Y.; Yuanqing, M.; Zhenan, Z.; Haishan, W.; Jie, Z.; Kerong, D.; Huiwu, L.; et al. Surgical Masks as Source of Bacterial Contamination during Operative Procedures. J Orthop Translat 2018, 14, 57–62. [Google Scholar] [CrossRef]
210. Jefferson, T.; Mar, C.B.D.; Dooley, L.; Ferroni, E.; Al-Ansary, L.A.; Bawazeer, G.A.; Driel, M.L.; van Jones, M.A.; Thorning, S.; Beller, E.M.; et al. Physical Interventions to Interrupt or Reduce the Spread of Respiratory Viruses. Cochrane Databaseof Systematic Reviews 2020. [Google Scholar] [CrossRef]