Size resolved aerosol respiratory doses in a Mediterranean urban area: From PM10 to ultrafine particles

Chemically Resolved Respiratory Deposition of Ultrafine Particles Characterized by Number Concentration in the Urban Atmosphere

Ultrafine particles (UFPs) dominate the atmospheric particles in number concentration, impacting human health and climate change. However, existing studies primarily rely on mass-based approaches, leading to a restricted understanding of the number-based and chemically resolved health effects of atmospheric UFPs. In this study, we utilized a high-mass-resolution single-particle aerosol mass spectrometer to investigate the online chemical composition and number size distribution of ultrafine, fine, and coarse particles during the summertime in urban Shenzhen, China. Human respiratory deposition dose assessments of particles with varying chemical compositions were further conducted by a respiratory deposition model. The results showed that during our observation, particles containing elemental carbon (EC) were the dominant components in UFPs (0.05-0.1 μm). Compared to fine and coarse particles, UFPs can deposit more deeply into the respiratory tract with a daily dose of ∼2.08 ± 0.67 billion particles. Among the deposited UFPs, EC-cluster particles constituted ∼85.7% in number fraction, accounting for a daily number dose of ∼1.78 billion particles, which poses a greater impact on human health. Simultaneously, we found discrepancies in the chemically resolved particle depositions among number-, surface area-, and mass-based approaches, emphasizing the importance of an appropriate metric for particle health-risk evaluation.

Intrauterine and early postnatal exposures to submicron particulate matter and childhood allergic rhinitis: A multicity cross-sectional study in China

BACKGROUND

Airborne particulate matter pollution has been linked to occurrence of childhood allergic rhinitis (AR). However, the relationships between exposure to particulate matter with an aerodynamic diameter ≤1 μm (PM1) during early life (in utero and first year of life) and the onset of childhood AR remain largely unknown. This study aims to investigate potential associations of in utero and first-year exposures to size-segregated PMs, including PM1, PM1-2.5, PM2.5, PM2.5-10, and PM10, with childhood AR.

METHODS

We investigated 29286 preschool children aged 3-6 years in 7 Chinese major cities during 2019-2020 as the Phase II of the China Children, Families, Health Study. Machine learning-based space-time models were utilized to estimate early-life residential exposure to PM1, PM2.5, and PM10 at 1 × 1-km resolutions. The concentrations of PM1-2.5 and PM2.5-10 were calculated by subtracting PM1 from PM2.5 and PM2.5 from PM10, respectively. Multiple mixed-effects logistic models were used to assess the odds ratios (ORs) and 95% confidence intervals (CIs) of childhood AR associated with per 10-μg/m3 increase in exposure to particulate air pollution during in utero period and the first year of life.

RESULTS

Among the 29286 children surveyed (mean ± standard deviation, 4.9 ± 0.9 years), 3652 (12.5%) were reported to be diagnosed with AR. Average PM1 concentrations during in utero period and the first year since birth were 36.3 ± 8.6 μg/m3 and 33.1 ± 6.9 μg/m3, respectively. Exposure to PM1 and PM2.5 during pregnancy and the first year of life was associated with an increased risk of AR in children, and the OR estimates were higher for each 10-μg/m3 increase in PM1 than for PM2.5 (e.g., 1.132 [95% CI: 1.022-1.254] vs. 1.079 [95% CI: 1.014-1.149] in pregnancy; 1.151 [95% CI: 1.014-1.306] vs. 1.095 [95% CI: 1.008-1.189] in the first year of life). No associations were observed between AR and both pre- and post-natal exposure to PM1-2.5, indicating that PM1 rather than PM1-2.5 contributed to the association between PM2.5 and childhood AR. In trimester-stratified analysis, childhood AR was only found to be associated with exposure to PM1 (OR = 1.077, 95% CI: 1.027-1.128), PM2.5 (OR = 1.048, 95% CI: 1.018-1.078), and PM10 (OR = 1.032, 95% CI: 1.007-1.058) during the third trimester of pregnancy. Subgroup analysis suggested stronger PM-AR associations among younger (<5 years old) and winter-born children.

CONCLUSIONS

Prenatal and postnatal exposures to ambient PM1 and PM2.5 were associated with an increased risk of childhood AR, and PM2.5-related hazards could be predominantly attributed to PM1. These findings highlighted public health significance of formulating air quality guideline for ambient PM1 in mitigating children's AR burden caused by particulate air pollution.

Adverse effects of exposure to fine particles and ultrafine particles in the environment on different organs of organisms

Particulate pollution is a global risk factor that seriously threatens human health. Fine particles (FPs) and ultrafine particles (UFPs) have small particle diameters and large specific surface areas, which can easily adsorb metals, microorganisms and other pollutants. FPs and UFPs can enter the human body in multiple ways and can be easily and quickly absorbed by the cells, tissues and organs. In the body, the particles can induce oxidative stress, inflammatory response and apoptosis, furthermore causing great adverse effects. Epidemiological studies mainly take the population as the research object to study the distribution of diseases and health conditions in a specific population and to focus on the identification of influencing factors. However, the mechanism by which a substance harms the health of organisms is mainly demonstrated through toxicological studies. Combining epidemiological studies with toxicological studies will provide a more systematic and comprehensive understanding of the impact of PM on the health of organisms. In this review, the sources, compositions, and morphologies of FPs and UFPs are briefly introduced in the first part. The effects and action mechanisms of exposure to FPs and UFPs on the heart, lungs, brain, liver, spleen, kidneys, pancreas, gastrointestinal tract, joints and reproductive system are systematically summarized. In addition, challenges are further pointed out at the end of the paper. This work provides useful theoretical guidance and a strong experimental foundation for investigating and preventing the adverse effects of FPs and UFPs on human health.

Influence of leaf morphological characteristics on the dynamic changes of particulate matter retention and grain size distributions

ABSTRACTPlant leaves can retain atmospheric particulate matter (PM) and thus alleviate air pollution. Herein, four plant species (Cerasus. serrulata, H. syriacus, H. tuberosus, and E. japonicus) from the central part of Shanxi Province, China, were investigated to analyse the dynamic changes in their PM retention capacity and grain size over five periods. The relationship between leaf morphological characteristics (leaf size and leaf surface microstructure) and dynamic changes were discussed in PM retention, revealing the influence of leaf morphological characteristics on the amount of PM retention and its composition. The results showed that amount and grain sizes of the retained PM differed significantly among the various studied species; however, the trends in PM retention of different species in the time series were the same. The grain size distributions of PM from the four species displayed a bimodal distribution, in which the main peak distribution range was 5-60 μm and the secondary peak distribution range was 0.4-1 μm. Leaves of smaller sizes and those with rough surfaces had a high PM retention capacity. Leaves with deep grooves are conductive to retaining PM2.5 and PM2.5-10, while leaves with hair are conductive to retaining PM>10. Therefore, the morphological characteristics of leaves should be considered when selecting the use of plant species to alleviate air pollution.Highlights Dynamics of PM retention capacity and grain size distributions of four plant species were analysed.Grain size distributions of PM retained on leaves had a bimodal distribution.Small leaves with grooves or hair are conductive to PM retention.Grooves are conductive to fine PM retention while hairs are conductive to coarse PM retention.

Oxidative stress and inflammation induced by air pollution-derived PM2.5 persist in the lungs of mice after cessation of their sub-chronic exposure

More than 7 million early deaths/year are attributable to air pollution. Current health concerns are especially focused on air pollution-derived particulate matter (PM). Although oxidative stress-induced airway inflammation is one of the main adverse outcome pathways triggered by air pollution-derived PM, the persistence of both these underlying mechanisms, even after exposure cessation, remained poorly studied. In this study, A/JOlaHsd mice were also exposed acutely (24 h) or sub-chronically (4 weeks), with or without a recovery period (12 weeks), to two urban PM2.5 samples collected during contrasting seasons (i.e., autumn/winter, AW or spring/summer, SS). The distinct intrinsic oxidative potentials (OPs) of AW and SS PM2.5, as evaluated in acellular conditions, were closely related to their respective physicochemical characteristics and their respective ability to really generate ROS over-production in the mouse lungs. Despite the early activation of the nuclear factor erythroid 2-related factor 2 (Nrf2) cell signaling pathway by AW and, in a lesser degree, SS PM2.5, in the murine lungs after acute and sub-chronic exposures, the critical redox homeostasis was not restored, even after the exposure cessation. Accordingly, an inflammatory response was reported through the activation of the nuclear factor-kappa B (NF-κB) cell signaling pathway activation, the secretion of cytokines, and the recruitment of inflammatory cells, in the murine lungs after the acute and sub-chronic exposures to AW and, in a lesser extent, to SS PM2.5, which persisted after the recovery period. Taken together, these original results provided, for the first time, new relevant insights that air pollution-derived PM2.5, with relatively high intrinsic OPs, induced oxidative stress and inflammation, which persisted admittedly at a lower level in the lungs after the exposure cessation, thereby contributing to the occurrence of molecular and cellular adverse events leading to the development and/or exacerbation of future chronic inflammatory lung diseases and even cancers.

PM2.5 and its respiratory tract depositions on blood pressure, anxiety, depression and health risk assessment: A mechanistic study based on urinary metabolome

Effects of fine particulate matter (PM2.5) and regional respiratory tract depositions on blood pressure (BP), anxiety, depression, health risk and the underlying mechanisms need further investigations. A repeated-measures panel investigation among 40 healthy young adults in Hefei, China was performed to explore the acute impacts of PM2.5 exposure and its deposition doses in 3 regions of respiratory tract over diverse lag times on BP, anxiety, depression, health risk, and the potential mechanisms. We collected PM2.5 concentrations, its deposition doses, BP, the Self-Rating Anxiety Scale (SAS) score and the Self-Rating Depression Scale (SDS) score. An untargeted metabolomics approach was used to detect significant urine metabolites, and the health risk assessment model was used to evaluate the non-carcinogenic risks associated with PM2.5. We applied linear mixed-effects models to assess the relationships of PM2.5 with the aforementioned health indicators We further evaluate the non-carcinogenic risks associated with PM2.5. We found deposited PM2.5 dose in the head accounted for a large proportion. PM2.5 and its three depositions exposures at a specific lag day was significantly related to increased BP levels and higher SAS and SDS scores. Metabolomics analysis showed significant alterations in urinary metabolites (i.e., glucoses, lipids and amino acids) after PM2.5 exposure, simultaneously accompanied by activation of the cAMP signaling pathway. Health risk assessment presented that the risk values for the residents in Hefei were greater than the lower limits of non-cancer risk guidelines. This real-world investigation suggested that acute PM2.5 and its depositions exposures may increase health risks by elevating BP, inducing anxiety and depression, and altering urinary metabolomic profile via activating the cAMP signaling pathway. And the further health risk assessment indicated that there are potential non-carcinogenic risks of PM2.5 via the inhalation route in this area.

Assessing the cytotoxicity of aerosolized carbon black and benzo[a]pyrene with controlled physical and chemical properties on human lung epithelial cells

Atmospheric particulate matter (PM) is a complex mixture of hazardous particles containing hundreds of inorganic and organic species. Organic components, such as carbon black (CB) and benzo[a]pyrene (BaP), are known to exhibit diverse genotoxic and carcinogenic effects. The toxicity of CB and polycyclic aromatic hydrocarbons has been well studied, however the combined toxicity is much less understood. A spray-drying system was used to control the size and chemical composition of PMs. PMs were prepared by loading BaP on three different sized CBs (0.1 μm, 2.5 μm, and 10 μm) to obtain BaP-unloaded CB (CB0.1, CB2.5, and CB10) and BaP-loaded CB (CB0.1-BaP, CB2.5-BaP, and CB10-BaP). We analyzed cell viability, levels of oxidative stress, and pro-inflammatory cytokines using human lung cells (A549 epithelial cells). Cell viability decreased when exposed to all PMs (PM0.1, PM2.5, and PM10), regardless of the presence of BaP. The increase in PM size due to BaP-adsorption to CB resulted in insufficient toxic effects on human lung cells compared to CB alone. Smaller CBs reduced cell viability, leading to reactive oxygen species formation, which can cause damage to cellular structures deliver more harmful substances. Additionally, small CBs were predominant in inducing the expression of pro-inflammatory cytokines in A549 epithelial cells. These results indicate that the size of CB is a key factor that immediately affects the inflammation of lung cells, compared to the presence of BaP.

Estimating the mortality attributable to indoor exposure to particulate matter of outdoor origin in mainland China

Previous estimations on the premature deaths attributable to indoor ambient particulate matter (PM) with aerodynamic diameter < 2.5 μm (PM_2.5) of outdoor origin only considered the indoor PM_2.5 concentration, which always neglected the impact from the distribution of particle size and the PM deposition in human airways. To tackle this issue, we first calculated the premature deaths due to PM_2.5 was approximately 1,163,864 persons in mainland China in 2018 by using the global disease burden approach. Then, we specified the infiltration factor of PM with aerodynamic diameter < 1 μm (PM₁) and PM_2.5 to estimate the indoor PM pollution. Results showed that average concentrations of indoor PM₁ and PM_2.5 of outdoor origin were 14.1 ± 3.9 μg/m³ and 17.4 ± 5.4 μg/m³, respectively. The indoor PM₁/PM_2.5 ratio of outdoor origin was estimated to be 0.83 ± 0.18, which was 36 % higher than the ambient PM₁/PM_2.5 ratio (0.61 ± 0.13). Furthermore, we calculated the premature deaths from the indoor exposure of outdoor origin was approximately 734,696, accounting for approximately 63.1 % of total deaths. Our results are 12 % higher than previous estimations neglecting the impact from the distribution disparities of PM between indoor and outdoor. Regarding the cause-specific diseases, indoor PM_2.5 exposure of outdoor origin accounted for 293,379 deaths to ischemic heart disease, followed by 158,238 deaths to chronic obstructive pulmonary disease, 134,390 deaths to stroke, 84,346 cases to lung cancer, 52,628 deaths to lower respiratory tract infection, and 11,715 deaths to type 2 diabetes. In addition, we for the first time estimated the indoor PM₁ of outdoor origin has led to approximately 537,717 premature deaths in mainland China. Our results have well demonstrated the health impact may be approximately 10 % higher when considering the effects from infiltration and respiratory tract uptake and physical activity levels, comparing to the treatment that only used outdoor PM concentration.

Association of ambient PM1 with hospital admission and recurrence of stroke in China

BACKGROUND

Particulate matter (PM) pollution is a well-known risk factor of stroke. However, little is known about the association between PM₁ (aerodynamic diameter ≤ 1.0 μm) and stroke. We estimated the associations of short-term exposure to PM₁ with hospital admission and recurrence of stoke in China.

METHODS

Stroke data were derived from the Chinese Stroke Center Alliance (CASA) program conducted in 1458 hospitals in 292 Chinese cities from 2015 to 2019. Daily air pollution and meteorological data were collected in the cities where studied hospitals were located. Daily PM₁ concentration was estimated by a generalized additive model (GAM) using PM_2.5 and meteorological variables. A time-stratified case-crossover design was applied to estimate the associations of short-term exposure to PM₁ with hospital admission of stroke. A GAM model was used to estimate the association between average PM₁ exposure during hospitalization and the recurrence of stroke.

RESULTS

A total of 989,591 stroke cases were included in the study. Each 10 μg/m³ increase in PM₁ (lag06-day) was associated with a 0.53% (95%CI, 0.39%, 0.67%) increment in hospital admission for stroke. The adverse effects of PM₁ on ischemic stroke was stronger than on intracerebral hemorrhage. We found the associations were significant in Northeast (0.94%, 95%CI, 0.51%, 1.38%), North (0.47%, 95%CI, 0.20%, 0.75%), Central (0.57%, 95%CI, 0.30%, 0.85%), and East China (0.63%, 95%CI, 0.27%, 0.99%). Of all stroke cases, 62,988 (6.4%) had recurrent stoke attack during their hospitalization. Each 10 μg/m³ increase in PM₁ was associated with a 1.64% (95%CI, 1.28%, 2.01%) increment in recurrence of stroke during hospitalization.

CONCLUSIONS

Short-term exposure to PM₁ may increase the risk of incidence and recurrence of stroke in China, and the effects varied across different types of stroke and regions. Geographically targeted strategies and measures are needed to control air pollution for reducing the burden of stroke from PM₁.

PM Dimensional Characterization in an Urban Mediterranean Area: Case Studies on the Separation between Fine and Coarse Atmospheric Aerosol

Fine particulate matter (PM) is object of particular attention due to its health effects. It is currently regulated by adopting PM2.5 as an indicator to control anthropogenic combustion emissions. Therefore, it is crucial to collect aerosol samples representative of such sources, without including PM from natural sources. Thus, a clean separation between coarse and fine mode aerosol should be set. With this purpose, aerosol size mass distribution was taken in the aerodynamic diameter range from 0.5 to 10 µm. In comparison with a base scenario, characterized by local pollution sources, three case studies were considered, involving desert dust advection, sea salt advection and forest fire aerosol from a remote area. In the base scenario, PM2.5 represented a suitable fine-mode indicator, whereas it was considerably affected by coarse PM in case of desert dust and sea salt aerosol advection. Such interference was considerably reduced by setting the fine/coarse separation at 1.0 µm. Such separation underrepresented fine PM from forest fire long-range transport, nonetheless in the case studies considered, PM1 represented the best indicator of fine aerosol since less affected by coarse natural sources. The data presented clearly support the results from other studies associating the health effects of PM2.5 to PM1, rather than to PM1–2.5. Overall, there is a need to reconsider PM2.5 as an indicator of fine atmospheric aerosol.

The effectiveness of urban trees in reducing airborne particulate matter by dry deposition in Tehran, Iran

Deposition of atmospheric pollution as particulate matter (PM) has become a serious issue in many urban areas. This study measured and estimated the amount of atmospheric PM deposition onto oriental plane (Platanus orientalis L.) trees located in Tehran Megapolis, Iran. PM deposited on the leaves of urban trees during spring and summer was estimated using leaf wash measurements. In addition to direct measurements, the dry deposition velocity and the yearly whole-tree PM deposition were estimated using both field measurements and a theoretical model of deposition flux. We estimated air quality improvement as a result of the trees at respiratory height (1.5 m), tree height (10 m), and boundary layer height (1719 m). Foliar PM deposition during spring and summer was estimated to average 0.05 g/leaf and 41.39 g/tree using direct measurements. The annual PM deposited on the leaves, trunk, and branches of an average urban tree was calculated to be 78.60 g/tree. Trees were estimated to improve air quality at 1.5 m, 10 m, and 1719 m from ground level by 25.8%, 5.8%, and 0.1%, respectively. Hence, oriental plane trees substantially reduce PM at respiratory height.

Personal deposited dose and its influencing factors at several Greek sites: an analysis in respect to seasonal and diurnal variations

The deposited dose in the human respiratory tract and its influencing factors were investigated for 8 urban/suburban locations within Greek cities. A dosimetry model (ExDoM2) was implemented assuming a 24-h exposure scenario to ambient PM₁₀ whereby regional deposition rates were obtained. Simulations were performed considering three cases (Sahara dust, cold, and warm periods) with seasonal and diurnal variations examining the relative sources and other influencing factors in each case. Health risk indexes such as the relative risk and attributable fraction were also estimated. Overall, higher daily deposited dose was obtained for all urban compared with suburban locations (p < 0.05) and for cold compared with the warm periods (252-820 μg for cold period and 300-686 μg for warm period) for all locations. This finding was associated with increased deposition rate on cold period during evening/night hours, as a result of significant heating emissions. Besides that, most of the urban locations showed relative comparable deposition rates during the day, compared with the daily mean, for the two periods (cold and warm), indicating that urban-associated sources such as exhaust emissions and road dust resuspension contribute similarly to the deposited dose irrespectively of the season. Finally, the highest deposited dose was obtained during Sahara dust events ranged from 1881 to 4648 μg.

Molecular characterization of size-segregated organic aerosols in the urban boundary layer in wintertime Beijing by FT-ICR MS

Organic aerosols, complicated mixtures of organic compounds, are important constituents of atmospheric particulate matter. However, little is known about the size distributions and vertical profiles of these constituents at a molecular level in the urban boundary layer. Here, we characterized the molecular compositions of size-segregated samples collected simultaneously at two heights (8 m and 260 m above ground level) in urban Beijing during the winter of 2018. The CHO, CHNO, CHOS, and CHNOS subgroups in water-soluble organic carbon were characterized using a 15-T ultrahigh-resolution Fourier transform-ion cyclotron resonance (FT-ICR) mass spectrometer. We found that both their numbers and magnitudes increased with a decrease in the particle size, especially for high molecular weight (HMW) compounds, except CHNOS. The number of CHNOS species also increased in the coarse mode, presumably because the alkalinity could inhibit their hydrolysis in the coarse mode. The compounds in small particles with higher O/C ratios and carbon oxidation state were possibly more aged, while the coarse particles with more lipid- and peptide-like compounds should originate from fresh emissions. Moreover, as the oxidation state increases in small particles, functionalization is enhanced for sulfur-containing compounds with fracturing of the benzene ring, while CHO and CHNO are potentially dominated by demethylation with ring-retaining products. It is worth noting that common compounds with the same molecular characteristics accounted for more than 86% of the total compounds between 260 m and ground level (8 m), demonstrating that the aerosols were well mixed in the urban boundary layer. Nonetheless, the relative content of the compounds was higher at ground level due to the impact of primary emissions, which increased with the particle size. In addition, the compounds in submicron particles were more oxidized at 260 m, while the opposite was observed in the coarse mode.

Mortality Risk Associated with Short-Term Exposure to Particulate Matter in China: Estimating Error and Implication

Most previous studies used a specific size of particulate matter (PM_x) for dosimetry estimation when determining particulate matter (PM)-associated risk, which precluded the impact of other sizes of PM. Here, we used a multiple-path particle dosimetry model to determine the deposition of PM in human airways and further estimated the associated mortality risk in 205 cities in China. Results showed that the fractions of PM₁, PM_1-2.5, and coarse PM (PM_2.5-10) deposited in the tracheobronchial (TB) and pulmonary airways were estimated in ranges of 11.06-12.83, 19.9-26.37, and 5.35-9.81%, respectively. Each 10 μg/m³ increase in deposited PM was significantly associated with a nationwide increment of 1.12% (95% confidence interval, CI, 0.77-1.49%) for total nonaccidental mortality. Short-term exposure to PM during 2014-2017 resulted in a nationwide mortality of 98 826 cases/year, with contributions from PM₁, PM_1-2.5, coarse PM of 37.7, 43.1, and 19.2%, respectively. Our study demonstrated that the estimated mortality counts may be associated with the coefficient of variation of dosimetry estimations. In addition, we revealed the caution should be exercised when interpreting PM_x-associated risk and further reinforced the importance of size distribution in relevant research.

Variations in Reactive Oxygen Species Generation by Urban Airborne Particulate Matter in Lung Epithelial Cells-Impact of Inorganic Fraction

Air pollution is associated with numerous negative effects on human health. The toxicity of organic components of air pollution is well-recognized, while the impact of their inorganic counterparts in the overall toxicity is still a matter of various discussions. The influence of airborne particulate matter (PM) and their inorganic components on biological function of human alveolar-like epithelial cells (A549) was investigated in vitro. A novel treatment protocol based on covering culture plates with PM allowed increasing the studied pollutant concentrations and prolonging their incubation time without cell exposure on physical suffocation and mechanical disturbance. PM decreased the viability of A549 cells and disrupted their mitochondrial membrane potential and calcium homeostasis. For the first time, the difference in the reactive oxygen species (ROS) profiles generated by organic and inorganic counterparts of PM was shown. Singlet oxygen generation was observed only after treatment of cells with inorganic fraction of PM, while hydrogen peroxide, hydroxyl radical, and superoxide anion radical were induced after exposure of A549 cells to both PM and their inorganic fraction.

Submicron and Ultrafine Particles in Downtown Rome: How the Different Euro Engines Have Influenced Their Behavior for Two Decades

Today, submicron particles are recognized as the new target in environmental sciences and human health issues as well. Their level in urban air is strongly affected by anthropogenic sources, i.e., domestic heating and autovehicular traffic, but the availability of large datasets represents a limit in the knowledge both of the behavior and of the relative levels. This paper would like to highlight the role of these two anthropogenic sources in a big city such as Rome in the particle formation/removal processes in the range 18–750 nm using a Scanning Mobility Particle Analyser (SMPS). The investigation starts from data collected in the previous decade (2010) and analyzes the role played by different Euro (0–6) engines on the particle levels as well as the responsibility of different biomass burning in this issue. Furthermore, a chemometric approach (Cluster Analysis, CA, and Principal Component Analysis, PCA) has allowed the identification of three different clusters, strongly dependent on the accumulation and nucleation modes of the Ultrafine Particles. On the other hand, the PCA demonstrated a scatter distribution in December larger than that in October, justified by the different sources present in these periods.

Ultrafine Particle Features Associated with Pro-Inflammatory and Oxidative Responses: Implications for Health Studies

Suspected detrimental health effects associated with ultrafine particles (UFPs) are impressive. However, epidemiological evidence is still limited. This is potentially due to challenges related to UFP exposure assessment and the lack of consensus on a standard methodology for UFPs. It is imperative to focus future health studies on those UFP metrics more likely to represent health effects. This is the purpose of this paper, where we extend the results obtained during the CARE (“Carbonaceous Aerosol in Rome and Environs”) experiment started in 2017 in Rome. The major purpose is to investigate features of airborne UFPs associated with pro-inflammatory and oxidative responses. Aerosol chemical, microphysical, and optical properties were measured, together with the oxidative potential, at temporal scales relevant for UFPs (minutes to hours). The biological responses were obtained using both in-vivo and in-vitro tests carried out directly under environmental conditions. Findings indicate that caution should be taken when assessing health-relevant exposure to UFPs through the conventional metrics like total particle number concentration and PM2.5 and Black Carbon (BC) mass concentration. Conversely, we recommend adding to these, a UFP source apportionment analysis and indicators for both ultrafine black carbon and the size of particles providing most of the total surface area to available toxic molecules.