Spatial distribution and risk assessment of polychlorinated biphenyl compounds from open incineration of used medical disposable face masks

Abstract

The handling of used medical face mask waste is of great environmental concern, particularly in the developing African countries. A common technique for disposing of these materials is through open burning; however, this approach raises issues of air pollution. Hence, this study determined the concentration of polychlorinated biphenyl compounds (PCBs) from the open burning of different disposable medical facemask materials. A health risk assessment was conducted to evaluate the potential health risks associated with human inhalation of emissions from the open burning of these materials, using various health risk indicators. The concentration distribution around the open incineration site was also modeled. Waste facemasks were combusted in the open reactor, and the emissions were sampled for PCBs using a filter-sorbent system. PCB analysis was done using GC-MS. Incremental Life Cancer Risk (ILCR), Inhalation Risk Assessment (IRA), and Hazard Quotient (HQ) were calculated to assess health risk. The results showed the Ʃ PCBs from different face mask materials range from 253.21 to 733.81 µg/m³, WHO-recommended surgical facemasks, and N95 Facemasks emit the highest concentration of PCBs. Daily inhalation exposure values for children range from 0.0037 to 0.012 µg TEQ kg^− 1 day^− 1 while IRA for adults ranges from 0.0016 to 0.0056 µg TEQ kg^− 1 day^− 1. Most of the ILCR values obtained are higher than the WHO stipulated permissible limits, which indicate possible cancer risk from inhalation of the emission. Also, HQ values obtained are greater than 1, indicating associated noncarcinogenic risks. The dispersion model of Dioxin-like PCBs from the burning source of the facemask depicts the presence of considerable PCB concentrations within a 3 km perimeter of the burning site after one year. The study concluded that proper disposal methods should be implemented for the management of medical face masks, especially in developing countries in Africa.

Introduction

The advent of coronavirus disease has sparked a global public health emergency and has increased the usage of medical facemasks^1–3. The main function of a medical facemask is to block droplets that may contain bacteria or viruses from being inhaled or exhaled and to protect both the wearer and others from contracting the infection⁴. Apart from COVID-19 diseases, medical facemasks are used to control viral diseases such as influenza (flu), tuberculosis, severe acute respiratory syndrome (SARS), middle east respiratory syndrome (MERS), common cold, and other viral infections. There was a surge in the production and usage of facemasks during the COVID-19 pandemic, approximately 129 billion facemasks were worn each month during period⁵.

The WHO-approved facemasks are surgical, N95, and face shields that are made from polymers, such as polypropylene, polyethylene, polyurethane, and polystyrene⁶. Governments of some developing countries encouraged the use of masks made from local materials in their countries. Materials such as cotton, linen, spandex, and other materials were used for facemasks to supplement the WHO-approved facemasks, which were already in high demand. However, the usage of these masks is associated with environmental issues in these developing countries, because of poor waste management. The indiscriminate dumping of used facemasks has led to land pollution, water pollution, the bioaccumulation of microplastics in the food chain, and obstruction of waterways and drainage^7–11. The most common method of waste disposal in the African continent is open burning^3,12,13. Studies has shown thar open burning of facemasks emits different types of pollutants, such as criteria air pollutants, persistent organic pollutants, and bottom ash residues^3,12–20.

A pollutant that is of concern is Polychlorinated Biphenyl (PCBs) which is a persistent organic pollutant compound with a distinguished large molecular weight. They are made up of two benzene rings with one or more chlorine atoms^21,22. PCBs are harmful to humans as they impair fertility and growth, degenerate the immune system, and trigger carcinogenic processes. These compounds have detrimental effects on growth and reproduction, and weaken immune systems²². Studies have has also shown that PCBs can affect the nervous system’s central and peripheral components, upsetting the complex equilibrium of the nervous system^23–25.

Previous studies on burning of medical facemasks include characterization of particulate matter and other pollutants from incinerated wastes containing medical waste mask, and results showed presence of facemasks in the combustion of waste increases the emission of toxic compounds²⁰. Another study on the characterization of polycyclic aromatic hydrocarbons compounds from open burning of different facemasks revealed that WHO-recommended face masks emit the highest concentration of PAHs from open burning³. However, there is no study available on the emission of PCBs or other persistent organic pollutants from the combustion of facemasks. Hence, this study is focused on determination of levels PCBs from open burning of different facemasks, which consist of WHO approved and locally manufactured facemasks. Also, the study is also intended to model the concentration distribution of dioxin-like PCBs around open burning area and health risk associated with human exposure to emission of PCBs from open burning of medical facemask was also investigated.

Chemical and material

Alumina gel (200–400) mesh, (Zico-Tech), Dichloromethane (Sigma–Aldrich), n-Hexane (Sigma–Aldrich) Silica (200–400 mesh, Zico-Tech). Gas chromatograph (Agilent Model 7890 A) and mass selective detector (Varian 3800/4000 GC–MS) (Agilent Technologies, Pato Alto, CA) Rotary evaporator (Infitex Co. Ltd). PCB internal standard (Qualikems chemical), ¹³C₁₂-PCB surrogate standard (Qualikems chemical).

Materials and methods

Different medical face mask materials, such as N95, Surgical, Cotton, Scarf, and Plastic face shields, were obtained from Afe Babalola University Multi-System Hospital waste dump site. Other types of face masks obtained were Linen, Spandex, and Organza. The samples were collected in September 2024. Each of the samples was sealed in aluminum foil and transported to the laboratory.

Emission sampling

The sampling was done using an improved European standard stationary source emission and determination of concentration method (EN-48-SS), which consists of sampling train of a vacuum pump, a sample probe, a filter paper, and a packed column containing absorbent material. 50 g of each facemask material was burned in an open reactor (35 cm in diameter and 25 cm in height). The emission samples were collected into the sampling train with Polyurethane Foam (PUF) of dimension 4 cm in diameter and 5 cm thick as an adsorbent. After sampling, the filter paper and PUF were wrapped in aluminum foil and taken to the laboratory for analysis²⁶.

Sample processing analysis

Dichloromethane (DCM) was used in a Soxhlet extractor for 12 h in order to recover PCBs from the samples. 20 ng of ¹³C₁₂-PCB surrogate standard was added to the PUFs before they were extracted. The extract underwent a clean-up process utilizing open column chromatography with silica and alumina. The extracts were concentrated to 5 ml using a rotary evaporator with a mild nitrogen stream. Analysis of PCB was done using GC-MS. (30 m length × 0.25 mm i.d. × 0.25 μm film thickness). Helium gas (99.9%) with a linear velocity of 1.5 ml/min was used as the mobile phase. The column temperature was originally set at 85 °C for a 3-minute hold, then increased to 200 °C at 35 °C per minute, and finally from 200 to 300 °C at a rate of 5 °C per minute with a 5-minute hold duration. The temperatures for the injector, quadrupole, and mass detector were 250, 150, and 230 °C, respectively²⁷. The mass acquisition range was 40–550 m/z, and the acquisition mode was selected-ion monitoring (SIM). The chromatographic peaks were identified by comparing mass spectra obtained with the spectra in the library (NIST 20). The electron ionization (EI) mode was used, and quantification of PCBs was done using the internal standard method.

Quality assurance/ quality control (QA/QC)

Field and procedural blanks, matrices, and surrogate recovery techniques were used to check the validity of the method. The samples were collected in duplicate, and they were handled alongside laboratory blanks. The recoveries of the¹³C₁₂-labelled PCBs ranged from 81 to 96%. Additionally, no blank correction was used, and the PCB amounts found in the blank sample were below the detection limit. To guarantee the integrity of the collected data, the following metrics were computed: recovery (%), relative standard deviation (RSD, %), limit of detection (LOD), and limit of quantification (LOQ). The LOD and LOQ values were established by calculating the signal-to-noise baseline (S/N) ratio value for each compound’s reference peaks and comparing them to the lowest calibration standard concentration, which resulted in S/N = 3 and S/N = 10, respectively. LODs and LOQs ranged from 0.053 to 0.218 µg/m³ from 0.061 to 0.2545 µg/m³, respectively.

Health risks implications

Toxicity Equivalence (eq. (1)), Inhalation Risk Assessment (eq. (2)), Incremental Lifetime Cancer Risk (eq. (3)), and Hazard Quotient (eq. (4)) are calculated to determine the health risk. Table 1 shows the parameters for the health risk analysis.

Table 1.

Parameter for health risk analysis.

	Adult	Children
Inhalation rate (IR)	20 m3/day12,30	9.6 m3/day12,30
Alveolar fraction (fr)	0.7512	0.7512
Exposure Time ( tf)	112	112
Body weight BW	70kg37	15 kg37
Exposure Duration (ED)	5 years3	5 years3
Exposure frequency (EF)	12 days	12 days3
Inhalation unit risk (IUR)	5.7×10-6 µg m[− 331,32	5.7×10-6µg m[− 331,32
Average exposure time (AT)	25,55037	25,55037
Reference dose (RfC)	3.3×10-331,32	3.3×10[–331,32

RfD = RfC (inhalation reference concentration (mg/m³ )) × Assumed inhalation rate (m³ /day) × 1/BW (kg) .

1

Where is the individual concentrations of PCBs, TEF is toxicity equivalence factors^28,29

2

.

IR is the Inhalation rate, is the air concentration of PCBs in terms of toxicity equivalence (ng TEQ/m³),f_r is the alveolar fraction retained in the lungs, and is the time of exposure. is the body weight³⁰.

3

4

C is the PCB concentration (µg m^{− 3}). ED is exposure duration, EF is exposure frequency in days yr ^{− 1}. IUR is the inhalation unit risk. AT is the average exposure time and RfD is the reference dose of PCB^31,32.

Statistical analysis

Data obtained were analyzed using Excel 2016 and Origin pro-10.1. Dispersion model of PCBs emission from the source was done using the Environmental Protection Agency Regulatory Model (ISCST3 AERMOD) software. The software was used to model the expected PCBs distribution around the vicinity of a burning site. Data inputted into the software are PCB concentration, wind direction, emission temperature, and emission height. Source point emission was chosen using a uniform Cartesian grid^3,33. Dispersion outputs were done for one, eight, twenty-four hours and one year.

Result and discussion

Table 2 shows different PCBs congeners observed from open burning of different face masks. PCB-28 congener was the most abundant, with a range of 0–333.64 µg/m³, with the Linen type of face mask having the highest concentration. Other PCBs congeners with high concentrations were PCB-153 with a range of 0–163.01 µg/m³ and PCB − 118 with a range of 63.6–91.07 µg/m³. The Ʃ PCBs obtained for different face mask ranges from 253.21 to 733. 81 µg/m³ (Fig. 1), the surgical face mask recommended by WHO emitted the highest concentration of PCBs when combusted, while the Towel material emitted the lowest concentration of PCBs. Other high emitters of PCBs observed from the materials incinerated were WHO-recommended N95 face masks and locally produced Linen face mask with concentrations of 691.38 µg/m³ and 719.58 µg/m³, respectively. The result also showed that towel and cotton face masks emitted the lowest concentration of PCBs when openly incinerated, with concentrations of 253.21 µg/m³ and 374.66 µg/m³, respectively. The concentrations of PCBs obtain in this study is in the range of similar study on emission of PAHs³. The ranges of PCBs concentration obtained is also in the concentration range of heavy metals and total suspended particles from emission of the waste containing disposable facemask²⁰.

Table 2.

PCBs concentrations from open burning of different face mask materials (µg/m³).

	Surgical	Cotton	Towel	Scarf	Plastic (face sheld)	Polyprolene(N95)	Linen	Spadex	Organiza
PCB 2	14.240	15.230	0.000	13.498	12.721	11.484	13.251	27.385	26.996
PCB 44	85.936	85.724	10.177	84.982	87.350	86.961	86.890	0.000	0.000
PCB 153	163.039	92.862	7.279	91.943	94.770	93.781	93.569	23.110	0.000
PCB 101	0.000	0.000	0.000	0.000	6.007	28.198	7.314	88.693	88.693
PCB 118	64.700	65.088	91.873	63.604	70.848	71.908	70.954	87.845	87.420
PCB 18	38.339	62.650	0.000	58.269	38.057	48.198	59.329	89.435	89.011
PCB 28	247.845	0.000	0.000	119.788	68.233	296.643	333.286	166.184	201.767
PCB 180	70.777	33.993	26.643	29.505	31.519	30.919	31.519	67.102	29.929
PCB 138	6.961	0.000	22.968	0.000	0.000	0.000	0.000	48.516	31.060
PCB 105	41.979	19.117	34.488	19.576	59.859	23.286	23.463	0.000	0.000
PCB 114	0.000	0.000	42.898	0.000	0.000	0.000	0.000	0.000	0.000
PCB 204	0.000	0.000	16.890	0.000	0.000	0.000	0.000	0.000	0.000

Fig. 1.

PCB summation in different facemask.

Dioxin-like PCBs activate the aryl hydrocarbon receptor and cause gene multiplication, leading to biological consequences^34,35. Studies have also shown that non-dioxin-like PCBs as equally dangerous as they modulate the effects of dioxin-like PCBs²⁸. Compounds of dl-PCBs observed in all the samples are PCB-105, PCB-114, and PCBs-118. Figure 2 shows the distribution of dioxin-like PCBs emitted from different facemasks. PCBs-118 was the most abundant with the range of 63.6–91.07 µg/m³, while PCB-105 was the lowest, with a range of 0–42.90 µg/m³. Figure 2 shows the summation of dl-PCBs in all the samples. Surgical, N95, and towel types of face masks were the high emitters of dl-PCBs in all the samples, with concentrations of 106.68, 130.71, and 169.26 µg/m³. Figure 3 also shows the comparison of the concentration of dioxin-like and non-dioxin-like PCBs observed in the study. The total emission of PCBs from each facemask material openly incinerated contain at least 13% of dl PCBs. The homolog pattern of PCBs is shown in Fig. 4. The tri-chlorinated congeners were the most abundant, ranging from 20% to 55% in each of the facemask except towel material. Oct chlorinated congeners of PCBs had lowest concentrations among all the congeners.

Fig. 2.

Summation of DL PCBs from Facemask open burning.

Fig. 3.

Comparison of dioxin-like and non dioxin-like PCBs from open burning of facemask.

Fig. 4.

The homolog pattern of PCBs from open burning of facemask.

Health implication

Toxicity equivalent quotient and inhalation exposure

Table 3 shows the Toxicity Equivalent (TEQ) and Inhalation Risk Assessment (IRA) of PCBs from open burning emission of different face masks. The toxicity equivalence of PCB 115 ranged from 0 to 0.018 µg WHO-TEQ /m³., with plastic face shield having the highest TEQ. The towel facemask was the only material having toxicity from PCB 114 with a concentration range of 0.013–0.018 µg WHO-TEQ /m³, PCB 118 TEQ ranged from 0.0019 to 0.0028 µg WHO-TEQ /m³ for surgical and towel facemasks respectively. The total toxicity equivalence was calculated for all the materials, the result showed towel and plastic face shield face masks had the highest TTEQ with concentrations of 0.026 and 0.020 µg WHO-TEQ /m³, respectively. While cotton facemask had the lowest TTEQ with a concentration of 0.008 µg WHO-TEQ /m³. This finding showed towels and plastic face masks produced the highest toxicity of PCBs when combusted. The calculated daily inhalation exposure values for children ranged from 0.0037 to 0.012 µg TEQ kg^− 1 day^− 1 while IRA for adults ranged from 0.0016 to 0.0056 µg TEQ kg^− 1 day^− 1 for cotton and towel face masks, respectively. The results also confirmed towels and plastic face shield face masks had the highest inhalation risk. The values of IRA obtained are several folds higher than the daily tolerable daily intake stipulated by WHO of 1000 fg TEQ kg^− 1 day^− 136. The implies there is a great Inhalation risk associated with human exposure to these pollutants in the ambient air.

Table 3.

Toxicity equivalent, inhalation risk assessment for open burning of different face mask (µg WHO-TEQ /m³).

	Surgical	Cotton	Towel	Scarf	Plastic (face sheld)	Polyprolene (N95)	Linen	Spadex	Organiza
PCB 105	0.013	0.0057	0.010	0.0058	0.018	0.0070	0.0070	0	0
PCB 114	0	0	0.013	0	0	0	0	0	0
PCB 118	0.0019	0.0019	0.0028	0.0019	0.0021	0.0022	0.0021	0.0026	0.0027
TTEQ	0.0149	0.0076	0.025	0.0078	0.02	0.0091	0.0091	0.0026	0.0026
IRA (children)	0.0070	0.0037	0.012	0.0037	0.0096	0.0043	0.0044	0.0013	0.0013
IRA(Adult)	0.0031	0.0016	0.0056	0.0017	0.0043	0.0020	0.0020	0.00056	0.00056

Incremental life cancer risk and hazard quotient

Human cancer risk is typically evaluated using the ILCR model. The model illustrates how likely it is for a person exposed to pollution to get cancer during their lifetime. The values of ILCR obtained in the study are shown in Table 3. The ILCR value for adults has the range of - with a mean value of while the value for the children was in the range of - with mean ILCR value of . An ILCR value greater than 10^{− 4} indicates high potential health hazards, according to the majority of regulatory agencies. The safety level of ILCR is 10^{− 6} or less, ILCR readings between 10^{− 6} and 10^{− 4} indicate a possible danger^3,32. However, majority of ILCR values obtained in this present study are slightly above 10^{− 6} indicating potential risk.

The hazard quotient (HQ) is used to express the non-carcinogenic risk associated with human exposure to a pollutant. HQ value greater than 1 indicate an associated non-carcinogenic risk. The calculated HQ at various sampling is also shown in Table 4. In this study, HQ values for all the face masks were all greater than 1, which implies human exposure to emission from burning of this face mask could lead to the development of chronic non-cancer organ dysfunction.

Table 4.

Incremental life cancer risk and hazard quotient for open burning of different face mask.

	Surgical	Cotton	Towel	Scarf	Plastic (face sheld)	Polyprolene (N95)	Linen	Spadex	Organiza
ILCR AD
ILCRCH
HQ	30.8	15.8	10.6	20.1	19.6	28.9	30.1	25.0	23.2
HQ	31.5	16.08	10.8	20.6	20.1	29.6	30.8	25.6	23.8

Spatial distribution

Figures 5 and 6 depict the spatial distribution of open burning of dl PCBs, PCB 105 and 118 for the open combustion of 50 g of face mask. Changing in coloration from red to purple implies a decreasing concentration pattern. It was observed that 1 h open burning of facemask emitted highest concentration of PCB which is transported to the northwestern to the burning site, this is linked to the predominant wind direction at the site. Also, PCB concentration range of 0.008 to 0.01 µg/m³ was observed within 3 km perimeter of the site (Figs. 5a and 6a). Figures 5b and 6b show the 8 h Isopleth Ground Level of PCBs, the gradual decrease in the concentration of the pollutants around the perimeter of the site was observed, lowest concentration of the pollutants was seen at the southern area of the burning site which is as a result of air transportation and dilution of the wind³. This same trend was observed in the 24-hour ground level Isopleth (Figs. 5c and 6c), where the Northwestern region began to experience the effect of the burning. Figures 5d and 6d show the annual Isopleth Ground Level of PCBs, the concentration of PCBs with a range of 0.001 to 0.02 µg/m³ was observed 500 m northern to the burning site, this could be linked to the persistent nature of the pollutants.

Fig. 5.

Spatial distribution of open burning of PCB105 (a) 1 h Isopleth Ground Level (b) 8 h Isopleth Ground Level (c) 24 h Isopleth Ground Level (d) Annual Isopleth Ground Level.

Fig. 6.

Spatial distribution of open burning of PCB 118 (a) 1 h Isopleth Ground Level (b) 8 h Isopleth Ground Level (c) 24 h Isopleth Ground Level (d) Annual Isopleth Ground Level.

Conclusion

The study determined the concentration of PCBs from different disposable medical facemasks and the risk associated with inhalation of these pollutants was examined using some health indicators. Different facemask materials were combusted in open air and sampled for PCBs. The results showed the Ʃ PCBs from different face mask materials range from 253.21 to 733.81 µg/m³, WHO recommended surgical facemask emits the highest concentration of PCBs, other high emitters are WHO-recommended N95 face mask and linen face mask with the concentration of 691.38 µg/m³ and 719.58 µg/m³. Results also show Surgical, N95, and towel face masks are the highest emitters of dl-PCBs in all the samples. The ILCR values for both adults and children are higher than WHO stipulated permissible limits of , which indicates possible cancer risk. Also, HQ values obtained are greater than 1 indicating associated noncarcinogenic risks. The dispersion model of dl PCBs from the burning source of facemask revealed considerable PCB concentrations within a 3 km perimeter of the burning site. The study suggested proper waste management should be put in place in disposing medical facemasks, especially in the developing countries of Africa.

Author contributions

“O.A.A, A.J.A and O.I. wrote the main manuscript text and A.S.A, R.A.T prepared figures, I.E.A, J.S.A. proof read the manuscript. All authors reviewed the manuscript.”

Funding

This study was funded by Princess Nourah bint Abdulrahman University Researchers Supporting Project number (PNURSP2026R13), Princess Nourah bint Abdulrahman University, Riyadh, Saudi Arabia.

Data availability

All data generated or analyzed during this study are included in this published article **.**.

Declarations

Competing interests

The authors declare no competing interests.