Abstract
Abstract. Environmentally persistent free radicals (EPFRs) are a new type of substance with potential health risks. EPFRs are widely present in atmospheric particulates, but there is a limited understanding of the size-resolved health risks of these radicals. This study reports the exposure risks and source of EPFRs in atmospheric particulate matter (PM) of different particle sizes (<10 µm) in Linfen, a typical coal-burning city in China. The type of EPFRs in fine particles (< 2.1 µm) is different from that in coarse particles (2.1–10 µm) in both winter and summer. However, the EPFR concentration is higher in coarse particles than in fine particles in summer, and the opposite trend is found in winter. In both seasons, combustion sources are the main sources of EPFRs, with coal combustion as the major contributor in winter, while other fuels are the major source in summer. Dust contributes part of the EPFRs, and it is mainly present in coarse particles in winter and the opposite in summer. The upper respiratory tract was found to be the area with the highest risk of exposure to EPFRs of the studied aerosols, with an exposure equivalent to that of approximately 21 cigarettes per person per day. Alveolar exposure to EPFRs is equivalent to 8 cigarettes per person per day, with combustion sources contributing the most to EPFRs in the alveoli. This study helps us to better understand the potential health risks of atmospheric PM with different particle sizes.
Highlights
Free radicals are atoms or groups containing unpaired electrons, such as hydroxyl radicals and superoxide radicals, and they usually have strong chemical reactivity and short lifetimes (Pryor et al, 1986; Finkelstein, 1982)
environmentally persistent free radicals (EPFRs) were detected in the particles of each tested size, but their EPFR concentration levels were different
This study systematically reported the particle size distribution of EPFRs in atmospheric particulate matter (PM) in Linfen, which is one of the most polluted cities in China and is located in a typical coal-burning area
Summary
Free radicals are atoms or groups containing unpaired electrons, such as hydroxyl radicals and superoxide radicals, and they usually have strong chemical reactivity and short lifetimes (Pryor et al, 1986; Finkelstein, 1982). A number of studies have investigated the occurrences, sources and formation process of EPFRs in atmospheric particulates in different regions. The study by Chen et al (2018a) suggests that EPFRs in atmospheric particulates are mainly derived from graphite oxide-like substances produced during combustion. Different particle sizes of atmospheric PM pose different health risks to humans, depending on the deposition efficiency of the particles and the chemical composition and concentrations of hazardous substances they contain (Strak et al, 2012; Valavanidis et al, 2008). The effects of particle size and season on the source, formation process and health risk of EPFRs were revealed. This study is of great significance for understanding the source and formation process of EPFRs in atmospheric particulates as well as for health risk assessments
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