大气细颗粒物中微塑料的特征和个体暴露评估

Individual exposure assessment of microplastics in airborne particle matter

关键词:  微塑料  个体暴露  热解  质谱

Key words:  microplastics  individual exposure  pyrolysis  mass spectrometry

摘要:

微塑料可以附着在大气细颗粒物（PM_2.5 ）上，因此，吸入PM_2.5中的微塑料会对呼吸系统造成潜在危害，然而，尚未量化通过PM_2.5吸入的微塑料量。文章以北京市为主要研究区域，于2023年9月—2024年4月开展系统采样，共采集并分析有效PM_2.5样品40份。研究使用个体暴露采样器模拟人类通过PM_2.5吸入微塑料的过程；采用热裂解-气相色谱-质谱联用技术对PM_2.5中的5种主要类型的微塑料进行识别和量化。研究发现，环境空气PM_2.5中5种微塑料的总浓度约为3.6—976 μg/m³ ，相比之下，低密度聚乙烯的整体含量较高，可达 505 μg/m³ ；通过吸入PM_2.5，个体对微塑料的暴露量约为每天52—14054 μg；天气条件和人类活动会显著影响微塑料的浓度和分布；在中等至重度污染条件下，PM_2.5中含有高达400—600 μg/m³ 的5种类型的微塑料；在人类活动频繁、人口密度高的场所，微塑料浓度甚至高达976 μg/m³ ，个体暴露水平达到每天14054 μg。

Abstract:

Background, aim, and scope Microplastics are plastic particles with a diameter of less than 5 mm. Microplastics are emerging contaminants resulting from human activities, which have attracted significant attention from both the scientific community and the general public. Microplastics have been listed as one of the four major emerging pollutants in China. Microplastics have been detected in various matrices, including air, soil, lake water, rivers, and even in food and drinking water, posing potential health risks to humans. Atmospheric environment serves as both a significant source and sink for microplastics, with fine particle matters (PM_2.5) acting as a crucial carrier for microplastics in the atmosphere. The inhalation of microplastics contained within PM_2.5 presents potential hazards to the respiratory system. However, researchers have yet to quantify the amount of microplastics inhaled through PM_2.5. In this study, personal exposure samplers were employed to simulate the process of human inhalation of microplastics via PM_2.5. The factors influencing the concentration of microplastics in the atmosphere under varying environmental conditions were analyzed. The primary aims of this study were to determine the levels and profiles of microplastics in atmospheric PM_2.5 and evaluate the human exposure to these pollutants through air inhalation. Materials and methods In this study, conducted in Beijing, China, an individual exposure particulate matter sampler was used to simulate human breathing and continuously collect microplastics in ambient air under daily working and living environments. The sampling period was from September 2023 to April 2024, and a total of 40 valid PM_2.5 samples were collected and analyzed. For sample testing, thermal decomposition pretreatment was first performed on the collected PM_2.5 samples, followed by gas chromatography-mass spectrometry to accurately identify and quantify five primary types of microplastics in PM_2.5. Results The total concentration of the five types of microplastics in atmospheric PM_2.5 ranged from approximately 3.6 μg/m³ to 976 μg/m³ , including a high content (up to 505 μg/m³ ) of low-density polyethylene (PE). The individual exposure to microplastics via inhalation of PM_2.5 ranged from 52 μg/m³ to 14054 μg/d. Both weather conditions and human activities can clearly affect the concentrations and distribution of microplastics. Under moderate to severe pollution conditions, PM_2.5 was found to contain high concentrations (400—600 μg/m³ ) of five types of microplastics. In areas with intense human activities and high population density, the microplastics concentrations soared to 976 μg/m³ , with individual exposure levels reaching 14054 μg/d. Discussion The study on five common types of microplastics in ambient air reveals that the concentration of atmospheric microplastics is influenced by multiple factors due to the inherent instability of the atmospheric environment. Notably, the concentration of PE in PM2.5 is generally higher than that of other microplastics. In three-quarters of the samples, the concentration of PE exceeds that of the other four types of microplastics by one to two orders of magnitude. Meteorological conditions such as wind, haze, and sandstorms are primary factors affecting ambient air quality and play a significant role in determining the concentration and distribution of microplastics. Additionally, population density and human activities are crucial factors influencing the concentration of microplastics in air. Conclusions Our study reveals a significant correlation between elevated atmospheric PM_2.5 concentrations (under severe pollution conditions such as sandstorms) and increased microplastic levels. Notably, even during periods of relatively low pollution (characterized by clear skies and strong winds), microplastic concentrations also exhibit a substantial rise. Furthermore, due to the increased usage of plastic products, microplastic concentrations tend to rise significantly with higher population densities. In this research, we employed personal exposure samplers to simulate the human inhalation of microplastics contained within PM_2.5. By analyzing microplastic concentrations across various venues, we were able to assess the potential human exposure to microplastics. Recommendations and perspectives In future research, it is imperative to identify the sources of microplastics by investigating the factors influencing their concentration. This approach will enable the development of targeted strategies to minimize human exposure to inhalable microplastics and mitigate the potential for severe health risks associated with microplastic pollution.