Identification and characterization of microplastics in human nasal samples

Key points

• Human nasal cavity samples were collected, and presence of microplastics were evaluated.

• Microplastics were present, and major types were polyethylene, polyester, acrylic polymer, and polypropylene.

• Further research is needed regarding microplastics and its clinical impact on human nasal cavity.

1. INTRODUCTION

The literature exploring the effects of microplastics (MPs) on human health primarily focuses on the aquatic environment and the digestive system. ¹ Recently, MPs have been detected in atmospheric fallout, ² and MPs have also been obtained from human lung tissues. ³ It can be reasonably assumed that MPs in the air could be inhaled and may induce lesions in the respiratory system depending on individual susceptibility and particle properties. ¹

Still, studies that have reported the presence and characterization of MPs in the human nasal cavity are extremely rare. In this study, we aimed to determine the presence of MPs in the human nasal cavity, which serves as the first barrier encountered by external pathogens entering the human body. We collected human nasal samples and evaluated the presence of MPs and their characteristics, including size, shape, and polymeric matrix.

2. MATERIALS AND METHODS

All experimental protocols were approved by the institutional review board of Chung‐Ang University Hospital, and written informed consent was obtained from all enrolled participants (2020‐002‐405). We prospectively collected nasal hair (NH) samples from patients who had undergone septoplasty or endoscopic sinus surgery, and a total of 10 patients (from July 2020 to October 2020) were enrolled in this study. Samples were obtained in the operating room just before beginning the surgery. Samples were collected from five different sites: NH, middle turbinate (MT), inferior turbinate (IT), nasopharyngeal fluid (NF), and middle nasal cavity fluid (MNCF) (Table S1).

The microscopic analysis and chemical characterization of MPs were conducted using µ‐FTIR (Thermo Scientific Nicolet iN10 microscopy; MA, USA).

3. RESULTS

3.1. Abundance of MP in human nasal samples

A total of 390 MPs were detected from five different sites of 10 human nasal samples. The number of MPs found at each site was 86, 93, 51, 129, and 31 for NH, IT, MT, NF, and MNCF, respectively. The total MPs found in the procedural blank (six, n = 3) and laboratory blank (one, n = 3) were seven, indicating that the combined blank was 1.16 ± 0.98.

3.2. Characterization of MPs in human nasal samples

In total, the major plastic types identified were polyethylene (PE), polyester, acrylic polymer, polypropylene (PP), polystyrene (PS), PS copolymer, PE–PP copolymer, and polyurethane(PU). Other plastic types, including polysulfone, polyvinyl chloride (PVC), PE copolymer, poly(3‐hydroxybutyrate), and PVC copolymer, were less than 1% (Figure 1A). Most MPs found in the nasal samples were fragments (90.77%). Only 9.23% of MPs were fibers, composed of four types of plastics: polyester (15, 41.67%), PP (13, 36.11%), PE (5, 13.89%), and acrylic polymer (3, 8.33%) (Figure 1A).

FIGURE 1.

(A) Polymer types and shapes of the MPs found in all nasal samples. (B) Polymer‐type distribution of identified MPs in five different sites of nasal samples. The color of each polymer type is consistent in all circular diagrams.

In all the MPs found in nasal structures, the average size of MPs was 29.43 ± 15.49 µm in width and 57.14 ± 51.98 µm in length. More specifically, the average width of MPs at each nasal site was 33.26 ± 18.23, 29.27 ± 13.77, 30.13 ± 21.38, 26.57 ± 12.66, and 28.24 ± 13.89 µm for NH, IT, MT, NF, and MNCF, respectively. The average length of MPs was 44.24 ± 24.94, 67.74 ± 56.41, 58.88 ± 75.71, 54.47 ± 59.43, and 60.38 ± 43.42 µm for NH, IT, MT, NF, and MNCF, respectively (Figure 2).

FIGURE 2.

Dimensions and polymer types of MPs found in five different sites of nasal samples. The number of MPs in each site was as follows: n = 86 in NH, n = 93 in IT, n = 51 in MT, n = 129 in NF, and n = 31 in MNCF. The color of each polymer type is consistent in all circular diagrams.

In all MPs found in the nasal structure, four major plastic types were identified: PE, polyester, acrylic polymer, and PP. These accounted for 87.96 ± 2.23% of the total plastic types identified in the nasal samples. The percentage of these four plastic types varied by sampling site (Figure 1B).

4. DISCUSSION

In the present study, we found that MP particles were significantly identified in human nasal samples, including NH, IT, MT, NF, and MNCF. The identified MP particles were predominantly fragment shaped, with a mean length of 57.14 µm ± 51.98, and composed of PE, polyester, acrylic polymer, and PP polymer types. This study effectively pinpointed and limited the sampling sites anatomically and characterized the MPs at each site.

There have been two reports concerning MP particles in the human nasal cavity. Tuna et al. ⁴ evaluated the presence of MPs in nasal lavage fluids of allergic rhinitis patients and healthy volunteers and found that the MP density was higher in allergic rhinitis patients than in healthy volunteers. In another study, Tas et al. ⁵ collected and evaluated the level of MPs in nasal lavage fluids of patients with chronic rhinosinusitis and healthy controls. However, both studies only counted the number of MP particles and did not specify characteristics such as size, shape, or polymer type. In the current study, we identified the number of MP particles and evaluated the characteristics of them.

This study had several limitations. First, we did not evaluate the effects of nasal MPs in vivo. Second, we did not evaluate other particles such as nanoplastics. Alongside MPs, the presence and impact of nanoplastics in the upper airway should also be investigated. Third, our result is based on patients during surgery and may not be representative of the general population. Additionally, our study reflects the results of indoor MPs among the general population who did not wear masks and worked in an indoor environment, as sampling was completed before the COVID‐19 pandemic. A comparative study on the detection of MPs in the nasal cavity between individuals who wear masks and those who do not, as well as between outdoor workers and indoor workers, would be an interesting research avenue to explore.

CONFLICT OF INTEREST STATEMENT

The authors declare no conflict of interest.

Supporting information

Supporting Information

Min HJ, Kim KS, Kim H, Gong J, Jeong J. Identification and characterization of microplastics in human nasal samples. Int Forum Allergy Rhinol. 2024;14:1943–1946. 10.1002/alr.23427