Environmentally persistent free radicals in PM2.5: a review

Abstract

Environmentally persistent free radicals (EPFRs) are a new class of pollutants that are long-lived in fine particles (PM 2.5), i.e., their 1/e lifetime ranges from days to months (or even infinite). They are capable of producing harmful reactive oxygen species such as hydroxyl radicals. The redox cycling of EPFRs is considered as an important pathway for PM 2.5 to induce oxidative stress inside the humans, causing adverse health effects such as respiratory and cardiovascular diseases. Consequently, research regarding their toxicity, formation and environmental occurrences in PM 2.5 has attracted increasing attentions globally during the past two decades. However, literature data in this field remain quite limited and discrete. Hence, an extensive review is urgently needed to summarize the current understanding of this topic. In this work, we systematically reviewed the analytical methods and environmental occurrences, e.g., types, concentrations, and decay behaviors, as well as possible sources of EPFRs in PM 2.5. The types of pretreatment methods, g-values of common EPFRs and categories of decay processes were discussed in detail. Moreover, great efforts were made to revisit the original data of the published works of EPFRs in airborne particulate matter and provided additional useful information for comparison where possible, e.g., their mean and standard deviation of g-values, line widths (∆H p-p), and concentrations. Finally, possible research opportunities were highlighted to further advance our knowledge of this emerging issue.

Environmentally persistent free radicals in indoor particulate matter, dust, and on surfaces

“…C n H m O p • , • C n H m O p ), 29,35,36 but, the molecular identities of the oxidized organics linked to ambient EPFR are largely unknown, with the exception of quinones, semi-quinones and organic peroxides. 20,37,38 Radical transport via EPFR and EPFR-converted reactive oxygen/nitrogen species (ROS/RNS) has been shown to be important for in-lung chemistry and climate-related cloud chemistry. 21,[29][30][31][32][39][40][41] While their importance as reservoirs of relatively stable, oxidation-initiating compounds may translate to indoor environments via airborne PM, on surfaces, and in dust, where they can accumulate over time, the abundance of EPFR indoors is largely unknown.…”

Electrospun Nanofiber Membranes for Air Filtration: A Review

“…PM is a trace air pollutant, which has been clearly recognized as a serious risk factor for premature death [ 31 ]. PM2.5 refers to the particles floating in the air whose diameter is less than 2.5 μm, which are small in size, strong in penetration, and easily carry various toxic substances that can cause cell death or organ dysfunction, which is extremely harmful [ 4 , 32 , 33 , 34 ]. PM2.5 enters the bronchi directly through the nasal cavity and then connects to the lungs, causing bronchitis, lung cancer, asthma, etc.…”

“…However, rapid economic development will inevitably bring about environmental damage, the continuous acceleration of industrialization has led to more and more particulate matter (PM) in the air, and the living environment of mankind is deteriorating. According to scientific research, air pollution can lead to many diseases, such as cardiovascular disease [ 3 ], malignant tumors, dry eyes, osteoporosis, fractures, conjunctivitis, infectious allergic diseases [ 4 ], inflammatory bowel disease, increased coagulation in blood vessels, a decreased glomerular filtration rate, and other physical diseases [ 5 ]. The serious harm caused by air pollution to the human body has also made air pollution control an urgent problem that needs to be solved.…”

Effect of long-term low concentrations of TiO2 nanoparticles on dewaterability of activated sludge and the relevant mechanism: the role of nanoparticle aging

“…This seems to be different from previous reports that both surface water bodies and piping sewage aging experiments could increase the Egs of anatase nanoparticle and decrease the energy band of rutile nanoparticle (Li et al, 2020b, c). This might be attributed to the differences in aging water quality and incubation time, for example, organic substances such as humic acid in the water can photosensitize the nanoparticles (Leads and Weinstein, 2019), while the presence of salt crystals reduced the photocatalytic e ciency of TiO 2 NP by the "sheltering phenomenon of deposited salt" (Xu et al, 2019). Moreover, compared to previous studies, here, the delay of the aging time could change the composition and thickness of deposited or wrapped on the surface of the nanoparticles, to an extent, the surface microstructure and photoactivity of the nanoparticles are the result of the comprehensive regulation of the above aging behaviors (Halle et al, 2020).…”