Impact of ultrafine particles and total particle number concentration on five cause-specific hospital admission endpoints in three German cities

Short-term exposure to ultrafine particles and respiratory infection hospital admissions in children in Copenhagen, Denmark

INTRODUCTION

Short-term exposure to ultrafine particles (UFP; <100 nm) may trigger respiratory hospitalizations, potentially even more so among children than adults, but available evidence is limited. We examined the association between short-term UFP exposure and respiratory infection hospital admissions in children in Copenhagen, Denmark.

METHODS

Daily concentrations of UFP were monitored at an urban background station during 2002-2018. Hospital admissions for lower and upper respiratory infections (LRTIs/URTIs), pneumonia, bronchitis, and influenza in children (0-18 years) were obtained from the Danish National Patient Register. Associations between UFP concentrations up to one week prior to admission and hospital admissions were examined using case-crossover design. Relative risks (RR) with 95 % confidence intervals (CI) were estimated per interquartile range (IQR) increase in UFP for the total population, and by sex, age (0-4/5-14/15-18 years) and socio-economic status (income, mother's education).

RESULTS

We observed 109,585 hospital admissions for respiratory infections. We found positive associations of UFP with total respiratory infections, URTIs, and pneumonia with RRs of 1.04 (95 % CI: 1.01, 1.06), 1.04 (1.01, 1.08), and 1.06 (1.01, 1.12), respectively, per IQR increase in three-day mean UFP (lag 0-2), that were robust to PM2.5 and NO2 adjustment. Associations were stronger in boys and children younger than 15 years, with no differences between socio-economic groups.

CONCLUSION

Short-term exposure to UFP triggered hospital admissions for respiratory infections, especially URTIs and pneumonia, in children in Copenhagen independently from PM2.5 and NO2. Our findings emphasize the need for policies and regulations aimed at improving urban air quality to protect children's health.

Short-term exposure to ultrafine particles and asthma hospital admissions in children in Copenhagen, Denmark

BACKGROUND

Ultrafine particles (UFP; <0.1 µm in diameter) are not regulated or commonly monitored but may be harmful to human health, particularly for children. In this study, we aimed to examine the association between short-term exposure to UFP and asthma hospital admissions in children.

METHODS

Daily UFP concentrations (2002-2018) were monitored at an urban background station in Copenhagen, Denmark. Asthma hospital admissions, demographic and socioeconomic information of children (0-18 years) were obtained from registries. A case-crossover design was applied to estimate the association between hospital admissions and up to 6-day UFP exposure windows for all children, and stratified by age, sex, family income, mother's education, prior asthma or prior respiratory infection.

RESULTS

We observed 15 903 asthma hospital admissions in total. An IQR increase in UFP was significantly associated with asthma hospital admissions, strongest at 2-day exposure windows (risk ratio (RR): 1.17 (95% CI: 1.09, 1.25)). These associations remained unchanged when adjusting for particulate matter <2.5 µm in diameter (PM2.5) or nitrogen dioxide (NO2), for which we also detected significant positive associations. Associations with UFP were stronger for school-aged children (5-14 years: RR: 1.26 (95% CI: 1.15, 1.38)) than for children younger than 5 years (1.01 (95% CI: 0.93, 1.10)).

CONCLUSIONS

In this large study in a low-exposure setting, we find that short-term exposure to UFP can trigger asthma hospital admissions in children, independently of associations with PM2.5 or NO2. This study adds evidence calling for the regulation and improvement of UFP exposure assessment to protect children's health in urban areas.

Unveiling the Impact of Wildfires on Nanoparticle Characteristics and Exposure Disparities through Mobile and Fixed-Site Monitoring in Toronto, Canada

This study investigates the impacts of wildfires on nanoparticle characteristics and exposure disparities in Toronto, integrating data from a large-scale mobile monitoring campaign and fixed-site measurements during the unprecedented 2023 wildfire season. Our results reveal changes in particle characteristics during wildfire days, with particle number concentrations decreasing by 60% and particle diameter increasing by 30% compared to nonwildfire days. Moreover, the median lung deposited surface area (LDSA) levels rose by 31% during wildfire events. We employed gradient boosting models to estimate near-road LDSA levels on both wildfire and nonwildfire days. The LDSA ratio (wildfire/nonwildfire) exceeded 2.0 in certain areas along highways and in downtown Toronto. Furthermore, our findings show that marginalized communities faced greater LDSA increases than less marginalized ones. Under wildfire conditions, the LDSA ratio difference between the most and least marginalized groups was 16% for recent immigrants and visible minorities and 7% for seniors and children, both statistically significant. This study delivers critical insights into the spatiotemporal variations of nanoparticle characteristics during wildfire and nonwildfire periods, demonstrating the substantial health risks posed by increased LDSA levels and the inequitable distribution of these risks among Toronto's diverse population.

Atmospheric new particle formation identifier using longitudinal global particle number size distribution data

Atmospheric new particle formation (NPF) is a naturally occurring phenomenon, during which high concentrations of sub-10 nm particles are created through gas to particle conversion. The NPF is observed in multiple environments around the world. Although it has observable influence onto annual total and ultrafine particle number concentrations (PNC and UFP, respectively), only limited epidemiological studies have investigated whether these particles are associated with adverse health effects. One plausible reason for this limitation may be related to the absence of NPF identifiers available in UFP and PNC data sets. Until recently, the regional NPF events were usually identified manually from particle number size distribution contour plots. Identification of NPF across multi-annual and multiple station data sets remained a tedious task. In this work, we introduce a regional NPF identifier, created using an automated, machine learning based algorithm. The regional NPF event tag was created for 65 measurement sites globally, covering the period from 1996 to 2023. The discussed data set can be used in future studies related to regional NPF.

PM2.5-induced ferroptosis by Nrf2/Hmox1 signaling pathway led to inflammation in microglia

Particulate matter (PM) has been a dominant contributor to air contamination, which will enter the central nervous system (CNS), causing neurotoxicity. However, the biological mechanism is poorly identified. In this study, C57BL/6J mice were applied to evaluate the neurotoxicity of collected fine particulate matter (PM2.5), via oropharyngeal aspiration at two ambient equivalent concentrations. The Y-maze results showed that PM2.5 exposure in mice would lead to the damage in hippocampal-dependent working memory. In addition, cell neuroinflammation, microglial activation were detected in hippocampus of PM2.5-exposure mice. To confirm the underlying mechanism, the microarray assay was conducted to screen the differentially expressed genes (DEGs) in microglia after PM2.5 exposure, and the results indicated the enrichment of DEGs in ferroptosis pathways. Furthermore, Heme oxygenase-1 (Hmox1) was found to be one of the most remarkably upregulated genes after PM2.5 exposure for 24 h. And PM2.5 exposure induced ferroptosis with iron accumulation through heme degradation by Nrf2-mediated Hmox1 upregulation, which could be eliminated by Nrf2-inhibition. Meanwhile, Hmox1 antagonist zinc protoporphyrin IX (ZnPP) could protect BV2 cells from ferroptosis. The results taken together indicated that PM2.5 resulted in the ferroptosis by causing iron overload through Nrf2/Hmox1 signaling pathway, which could account for the inflammation in microglia.

Los Angeles Basin's air quality transformation: a long-term investigation on the impacts of PM regulations on the trends of ultrafine particles and co-pollutants

This study investigates the long-term trends of ambient ultrafine particles (UFPs) and associated airborne pollutants in the Los Angeles Basin from 2007 to 2022, focusing on the indirect effects of regulations on UFP levels. The particle number concentration (PNC) of UFPs was compiled from previous studies in the area, and associated co-pollutant data, including nitrogen oxides (NOx), carbon monoxide (CO), elemental carbon (EC), organic carbon (OC), and ozone (O3), were obtained from the chemical speciation network (CSN) database. Over the study period, a general decrease was noted in the PNC of UFPs, NOx, EC, and OC, except for CO, the concentration trends of which did not exhibit a consistent pattern. UFPs, NOx, EC, and OC were positively correlated, while O3 had a negative correlation, especially with NOx. Our analysis discerned two distinct subperiods in pollutant trends: 2007-2015 and 2016-2022. For example, there was an overall decrease in the PNC of UFPs at an annual rate of -850.09 particles/cm3/year. This rate was more pronounced during the first sub-period (2007-2015) at -1814.9 particles/cm3/year and then slowed to -227.21 particles/cm3/year in the second sub-period (2016-2023). The first sub-period (2007-2015) significantly influenced pollutant level changes, exhibiting more pronounced and statistically significant changes than the second sub-period (2016-2022). Since 2016, almost all primary pollutants have stabilized, indicating a reduced impact of current regulations, and emphasizing the need for stricter standards. In addition, the study included an analysis of Vehicle Miles Traveled (VMT) trends from 2007 to 2022 within the Los Angeles Basin. Despite the general increase in VMT, current regulations and cleaner technologies seem to have successfully mitigated the potential increase in increase in PNC. Overall, while a decline in UFPs and co-pollutant levels was observed, the apparent stabilization of these levels underscores the need for more stringent regulatory measures and advanced emission standards.