Μm Particulate Matter Research Articles

Quantifying the impact of urban trees on air quality in Geneva, Switzerland

Atmospheric pollution threatens human health worldwide, with tropospheric ozone (O3) and particulate matter (PM) among the most harmful pollutants. Urban trees can reduce the concentration of air pollutants through dry deposition on their canopies and stomatal uptake. At the same time, urban trees can deteriorate air quality by emitting aerosol- and O3 precursors in the form of biogenic volatile organic compounds (BVOCs). O3 and PM removal, and BVOC emissions vary depending on the tree species. Therefore, the diversity and spatial distribution of urban trees significantly influence their impact on local air quality. This study employs a dual approach to assess and map the impact of urban trees on air quality in Geneva, Switzerland. Firstly, we use the i-Tree Eco model combined with a tree inventory (237,191 trees) to quantify BVOC emissions and PM10 (PM < 10 µm) and O3 removal at the genus level. Secondly, we develop a species-level parameterization using 51 common urban tree species to estimate the same variables and ozone-forming potential (OFP). Results show that the tree density is heterogeneous in the study area, leading to neighborhoods with greater biomass and, therefore, stronger influence by trees on local air quality. According to i-Tree Eco, urban trees in Geneva emitted 50 t of BVOCs, while removing 14 t of PM10 and 52 t of O3 in 2014. With the species-level parametrization, we estimate that urban trees removed about 66 ± 55 t of PM10 and 150 ± 96 t of O3 in 2014. However, they could also emit about 130 ± 52 t of BVOCs annually, which, under favorable conditions, can form 1153 ± 519 t of O3. Depending on the method, urban trees removed between 4 and 19 % of the anthropogenic PM10 emissions. The annual removal rates are comparable to findings in other European cities. The disparities between the two approaches are due to different parameterizations. This study could help urban planners to select adequate species for future planting programs in Geneva and more generally. It showed that the impact of urban trees on air quality is spatially heterogeneous but significant, and tightly linked to the species composition.

Relationships between water quality of a long-distance inter-basin water diversion project and air pollution emissions along the canal: Distributions, lag effects, and nonlinear responses

Understanding and quantifying the influences and contributions of air pollution emissions on water quality variations is critically important for surface water quality protection and management. To address this, we created a five-year daily data matrix of six water quality indicators—permanganate index (CODMn), NH3-N, pH, turbidity, conductivity, and dissolved organic matter (DOM)—and six air pollution indicators—O3, CO, NO2, SO2, 2.5 μm particulate matter (PM2.5), and inhalable particles (PM10)—using data from seven national monitoring stations along the world's longest water-diversion project, the Middle Route of the South-to-North Water Diversion Project in China (MR-SNWD). Multivariate techniques (Mann–Kendall, Spearman's correlation, lag correlation, and Generalized Additive Models [GAMs]) were applied to examine the nonlinear relationships and lag effects of air pollution on water quality. Air pollution and water quality exhibited marked spatial heterogeneity along the MR-SNWD, with all water quality parameters meeting Class I or II national standards and the air pollution indicators exceeding those thresholds. Except for CODMn and DOM, the other water quality and air pollution indicators exhibited significant seasonal differences. Air pollution exhibited significant lag effects on water quality at the northern stations, with NO2, SO2, PM2.5, and PM10 being highly correlated with changes in pH, with an average lag of 17 d. Based on the GAMs, lag effects enhanced the significant nonlinear relationships between air pollution and water quality, increasing the average deviance explained for CODMn, NH3-N, and pH by 93%, 24%, and 41%, respectively. These findings provide a scientific basis for protecting water quality along the long-distance inter-basin water-diversion project under anthropogenic air pollution.

Estimation of historical daily PM2.5 concentrations for three Chinese megacities: Insight into the socioeconomic factors affecting PM2.5

Studying historical changes in the 2.5 μm particulate matter concentration (PM2.5) can clarify the relationship between air pollution and socioeconomic development. Daily PM2.5 levels and meteorological data (2012–2022) for three large cities (Beijing, Shanghai, and Xi'an) at different development stages in different regions of China were used to construct a random forest (RF) model for estimating historical PM2.5 data for the period 1973–2011, a time period in which few measurements were made. The eigenvalue for visibility was the largest in the RF model; visibility explained 0.76–0.87 of the variance in PM2.5 for the three cities. The daily estimated PM2.5 was validated, with an R2 of 0.654–0.780 and average absolute error of 11.52–31.73 μg m−3 in the model. PM2.5 concentrations predicted by the RF model for 2004–2011 were highly correlated with gravimetric measurements (R = 0.585, p < 0.01). We extensively validated the results of RF using manual weighing PM2.5 data, online monitoring concentration of PM10, and aerosol optical depth (AOD), demonstrating the accuracy of the model. Over the study period, the PM2.5 level first increased and then decreased in the three cities; however, the year at which the trend changed differed. We further explored the effects of urbanization and economic growth on PM2.5 levels by investigating the correlations between socioeconomic indicators and PM2.5. The magnitude of the permanent population of Beijing and gross regional production growth in Shanghai were both significantly positively correlated with the PM2.5 level. Increasing the size of urban green areas can reduce PM2.5; this effect was strongest for the southern city of Shanghai, may due to their different climates and green tree species. Energy consumption and emissions from primary industries were strongly positively correlated with the urban PM2.5 level. An in-depth understanding of the factors affecting PM2.5 concentrations could help policymakers improve air quality management strategies, especially for densely populated megacities.

Hybrid Cellulose‐Based Systems for Triboelectrification in Aerosol Filtration, Ammonia Abatement and Respiration Monitoring

AbstractThe dissipation of charges by aging or under the effect of humid conditions considerably impedes a broader utilization of electrostatic fields in aerosol filtration. This study introduces a respiration‐driven air filter (RAF) that continuously generates triboelectric charges within a pair of tribolayers, which facilitates a sustained filtration performance. Such system is integrated in a multilayer unit that is inserted in personal protective equipment (RAFM) to efficiently capture, sense, and degrade airborne pollutants with no need for external power sources. The triboelectric nanogenerator‐based RAF continuously replenishes static charges and maintains an electrostatic field through breathing by the effect of contact‐electrification between two cellulose‐based tribolayers: a cellulose/metal organic framework cryogel (electron donor) and a cellulose–based electrospun membrane (electron acceptor). Notably, the triboelectric field of the RAF's tribolayer pair substantially enhances both the filtration efficiency (up to 93.8% for 0.3 µm particulate matter) and sensing/catalytic degradation (ammonia; degradation &gt;20%). When integrated in a circuit module, the RAFM effectively monitors respiration dynamics, acting as a breathing indicator/regulator. Overall, this study adds to the promise of tribogeneration through cellulose‐based materials and its application in exposure‐risk operations.

Electrospun‐SiO2‐Nanofiber‐Reinforced Cellulose Aerogel Loaded with ZIF‐67 for Air Filtration and Formaldehyde Adsorption

AbstractIndoor air pollution, which is detrimental to the human respiratory, nervous, and cardiovascular systems, is of increasing concern because considerable time is spent indoors. Thus, there is an urgent need to develop improved methods for controlling indoor air pollution. In this study, electrospinning and freeze‐drying methods are used to prepare a cellulose–silica nanofiber (C‐SNF) aerogel loaded with zeolitic imidazolate framework‐67 (ZIF‐67) for use in indoor air purification systems. The C‐SNF aerogel doped with 0.75 wt.% SiO2 nanofiber (SNF) exhibits a maximum compressive stress of 8.7 MPa, which is higher than that (6.4 MPa) of a pure cellulose aerogel. The compressive modulus of the aerogel exceeds 85% of its original value after 100 compression cycles. The C‐SNF aerogel exhibits a filtration efficiency of 99.91% against 0.3 µm salt particles at 32 L min−1, which is higher than that of the pure cellulose aerogel (51.25%). Moreover, a stable removal efficiency of 99.92% toward 2.5 µm particulate matter (PM2.5) is observed after ten cycles. Notably, the addition of ZIF‐67 to C‐SNF (ZIF‐67@C‐SNF) aerogel by in situ growth method resulted in a porosity of 92.3% and formaldehyde removal of 93.75%. The ZIF‐67@C‐SNF aerogel can be used in various applications including indoor‐air and adsorptive‐filtration masks.

Preparation and filtration performance of antibacterial PVDF/SiO2/Ag composite nanofiber membrane

Electrospinning nanofiber membrane has many advantages, such as high specific surface area, small pore size, high porosity, and good fibre uniformity, which makes it show excellent application potential in air filtration and personal protection. This study used an electrospinning method to create a PVDF/SiO2/Ag composite nanofiber membrane with superhydrophobic and antibacterial properties. It was deposited on the surface of PET fibre to create an air filter material with a sandwich structure, and its surface morphology, antibacterial properties, surface wettability, and filtration efficiency were studied. The results demonstrated that the adding of nanosilver significantly improved the antibacterial performance of the composite nanofiber membrane. In addition, the hydrophobic performance of the nanofiber membrane was significantly improved as the concentration of hydrophobic nano-SiO2 was increased. As a result, the PVDF/SiO2/Ag composite nanofiber membrane had a filtration efficiency of 99.94% for 0.3 μm particulate matter and a drag pressure drop of 112.3 Pa. Furthermore, the filtration efficiency of air microorganisms was greater than 99.99%, indicating a promising application in air filtration.

Particulate matter in school buildings: Influence of influx control of outdoor PM particles and building renovation in summer

The hazardous effects of air pollution on the human body are of grave concern, particularly the rising levels of 2.5 μm-particulate matter. Children are more susceptible to the lethal effects of particulate matter (PM) than adults. In this study, a case study of architectural renovation (ARCH-R) and facility renovation (FAC-R) was conducted in a school by focusing on the exit and entrance gates. In addition, the PM influx rate was evaluated. To evaluate the influx rate of PM, opening/closing recognition equipment and particle sensors were utilized. Following the renovation, the result was evaluated. During the daytime, the air curtain led to a reduction in the influx rate of PM of approximately 8% when the door was open. During the nighttime, it was confirmed that the fine dust influx rate was reduced through reinforcement of the door. However, regarding using these two measures in combination, it was confirmed that the concentration of PM increased in the corridor when the air curtain was operated while the door was closed. It was confirmed that both ARCH-R and FAC-R are necessary for controlling the influx of fine dust from the outdoor air. Appropriate operating guidelines should be provided for school operators.

Auto repair workers exposed to PM2.5 particulate matter in Barranquilla, Colombia: Telomere length and hematological parameters.

Exposure to 2.5µm particulate matter (PM2.5) in automotive repair shops is associated with risks to health. We evaluated the effects of occupational exposure to PM2.5 among auto repair-shop workers. Blood and urine samples were collected from 110 volunteers from Barranquilla, Colombia: 55 active workers and 55 controls. PM2.5 concentrations were assessed at each of the sampling sites and chemical content was analyzed by SEM-EDS electron microscopy. The biological samples obtained were peripheral blood (hematological profiling, DNA extraction) and urine (malondialdehyde concentration). Telomere length was assessed by qPCR and polymorphisms in the glutathione transferase genes GSTT1 and GSTM1 by PCR-RFLP, with confirmation by allelic exclusion. White blood cell (WBC), lymphocyte (LYM%) and platelet (PLT) counts and the malondialdehyde concentration were higher (4.10±0.93) in the exposed group compared to the control group (1.56±0.96). TL was shorter (5071±891) in the exposed individuals compared to the control group (6271±805). White blood cell (WBC) and platelet counts were positively associated with exposure. Age and TBARS were correlated with TL in exposed individuals. The GSTT1 gene alleles were not in Hardy-Weinberg (H-W) equilibrium. The GSTM1 gene alleles were in H-W equilibrium and allelic exclusion analysis confirmed the presence of heterozygous GSTM1 genotypes. SEM-EDS analysis showed the presence of potentially toxic elements, including Mg, Al, Fe, Mn, Rh, Zn, and Cu. Auto repair shop workers showed effects that may be associated with exposure to mixtures of pollutants present in PM2.5. The GSTM1 and GSTT1 genes had independent modulatory effects.

A new approach based on the augmented particle sink effect to remove indoor airborne particulate matter: Experimental study

Traditional indoor air cleaning technologies are mostly equipped with fans and auxiliary components in addition to the core purification unit, and consequently use more energy in the building environment. To energy-efficiently improve indoor air quality, this paper presents a new approach to remove indoor airborne particulate matter. The approach couples the negative pressure effect over the point sink zone by considering the electrohydrodynamic flow generated in a high-voltage gas discharge process to augment the particle sink effect. This facilitates indoor airborne particulate matter to be collected and removed more quickly. We evaluated the influencing factors on the particulate matter removal proportion by laboratory scale experiments: the applied voltage, interelectrode distance, and porosity and shape of the collecting electrode, and compared the particulate matter control performance and energy efficiency of this approach with those of the existing studies. Results showed that the 30 %–40 % porosity of the collecting electrode and stronger electric field intensity had a clearer removal proportion of particulate matter. Moreover, the energy efficiency for 1–2.5 μm particulate matter of this approach (12.7 (m3/h)/W) was 2.3–7.9 times higher than that of the commercially available conventional air cleaners (1.6–5.6 (m3/h)/W). Compared to conventional particle sink purification technique, this approach could save at least 50 % of the sink running time to achieve a better particulate matter removal effect, and shorten approximately 50 % of the 1–2.5 μm particulate matter reverse mass transfer time. This study provides an important reference basis for improving indoor air quality and the creation of a more sustainable society.

Filter evaluation and selection for heating, ventilation, and air conditioning systems during and beyond the COVID-19 pandemic.

Particle size removal efficiencies for 0.1–1.0 μm (PSE0.1−1.0) and 0.3–1.0 μm (PSE0.3−1.0) diameter of Minimum Efficiency Reporting Value (MERV) filters, an electrostatic enhanced air filter (EEAF), and their two‐stage filtration systems were evaluated. Considering the most penetrating particle size was 0.1–0.4 μm particulate matter (PM), the PSE0.1−1.0 as an evaluation parameter deserves more attention during the COVID‐19 pandemic, compared to the PSE0.3−1.0. The MERV 13 filters were recommended for a single‐stage filtration system because of their superior quality factor (QF) compared to MERV 6, MERV 8, MERV 11 filters, and the EEAF. Combined MERV 8 + MERV 11 filters have the highest QF compared to MERV 6 + MERV 11 filters and EEAF + MERV 11 filters; regarding 50% of PSE0.1−1.0 as the filtration requirements of two‐stage filtration systems, the MERV 8 + MERV 11 filtration system can achieve this value at 1.0 m/s air velocity, while PSE0.1−1.0 values were lower than 50% at 1.5 m/s and 2.0 m/s. EEAF obtained a better PSE0.3−1.0 in the full‐recirculated test rig than in the single‐pass mode owing to active ionization effects when EEAF was charged by alternating current.

Measurements of Tire and Roadway Dust Particulates in Chelyabinsk

Harmful emissions from tire wear and roadway wear are released into the air during the operation of vehicles. Particulate road dust contains carcinogenic substances. The amount and dispersion of particulate matter in road dust was determined with a portable laser particle counter. On asphalt roads, 75% of the harmful emissions were 0.3 µm particulate matter. On dirt roads, 95% of emissions were from particles less than 1 µm. The amount of large fractions of harmful emissions did not exceed 1.5%, regardless of traffic intensity. 30 m from the roadway, the concentration of harmful substances reduced by five- to sevenfold. By 2030, the number of vehicles in Chelyabinsk will increase by 25%. This will increase the amount of harmful emissions from tire and roadway wear by 20 tons per year.

Evaluation of cytokines in exhaled breath condensate in an occupationally exposed population to pneumotoxic pollutants.

The quarrying is considered a precarious occupation with high toxicity, is an informal economic activity that employs low technology, limited protection, and poses a risk to workers and their families. In quarrying, silica dust is generated and there is also occupational exposure to significant mixtures of pneumotoxic pollutants, including mineral dust (crystalline silica, carbon or cement, polycyclic aromatic hydrocarbons (PAHs), solvents, and others, which are aggravated by the lack of use of protective equipment, causing irreversible damage to the worker's respiratory health. Thus, the objective of this work focused on the evaluation of the respiratory health of artisan stonemasons in San Luis Potosí, Mexico through the study of exhaled breath condensate (EBC) (pH, pro-inflammatory cytokines) as well as the study of the exposure to pollutants present in the work area (PAHs, toluene, and 2.5µm particulate matter) through biomarkers of exposure (hippuric acid and hydroxylated metabolites of PAHs). The results show the presence of crystalline SiO2 in 100% of the samples analyzed; the PM2.5 concentrations were 5 to 10 times the permitted levels. Regarding exposure to PAHs, all the stonemasons presented urine concentrations of at least 5 of the OH-PAHs evaluated; 9-OH-FLU occurred at higher concentrations of 171.2 (122.7-279.4) µg L-1; hippuric acid, which was present in 100% of the workers evaluated in concentrations of 283.4 (27.72-1119) mg L-1, 100% of which were above the values established for occupational scenarios. The pH values obtained for the EBC samples were presented at an average of 7.07 (6.33-7.66). Pro-inflammatory cytokines were present in 86.1% of the study population. The cytokine that was found in higher concentrations was IL-2, with a mean of 178.01pgmL-1 and 3124.01pgmL-1 for the pH < 7 and pH > 7 groups, respectively. Some correlations between the cytokines and the exposure biomarkers were presented. Stonemasons are highly exposed to pneumotoxic pollutants and markers of inflammation at the pulmonary level; in addition, a high risk of developing silicosis. Quarrying should be addressed as a carcinogenic activity, which would imply the design of monitoring and control strategies for these pollutants that our country currently lacks, particularly in precarious occupations. It is necessary to develop strategies to protect the health of precarious workers.

Airflow Synergistic Needleless Electrospinning of Instant Noodle‐like Curly Nanofibrous Membranes for High‐Efficiency Air Filtration

Particulate matter (PM) pollution has become a serious environmental concern. Nanofibrous filters are widely reported to remove PM from polluted air. Herein, efficient and lightweight PM air filters are presented using airflow synergistic needleless electrospinning composed of auxiliary fields such as an airflow field and a secondary inductive electric field. Compared to needleless electrospinning with other spinnerets, it significantly improves productivity, fiber diameter, and porosity of fibrous air filters. The instant noodle-like nanofiber structure can also be controlled by adjusting the airflow velocity. These air filters exhibit high (2.5 μm particulate matter) PM2.5 removal efficiency (99.9%) and high (0.3 μm particulate matter) PM0.3 removal efficiency (99.1%), low pressure drop (56Pa for PM2.5 and 78Pa for PM0.3 ), and large dust holding capacitance (the maximum value is 168gm-2 for PM2.5 , while 102gm-2 for PM0.3 ). Meanwhile, the proposed PM filters are also tested suitable and stable to other polluted air filtrations such as cigarette smoke and sawdust. The large-scale synthesis of such an attractive nanofiber structure presents the great potential of high-performance filtration/separation materials.

Assessment of Indoor Air Quality in Residential Buildings of New England through Actual Data

Several studies on indoor air quality (IAQ) and sick building syndromes have been completed over the last decade, especially in cold countries. Efforts to make homes airtight to improve energy efficiency have created buildings with low ventilation rates, resulting in the build-up of indoor pollutants to harmful levels that would be otherwise unacceptable outdoors. This paper analyzed the infiltration rates, indoor temperatures, and variations in CO2, 2.5 μm particulate matter (PM2.5), and total volatile organic compound (TVOC) concentrations over the fall of 2021 in several homes in New England, USA. A relationship between outdoor and indoor conditions and ventilation strategies has been set using the results from blower door tests and actual indoor air quality data. Although all case studies lacked mechanical ventilation devices, such as those required by ASHRAE Standard 62.2, natural ventilation and air leakage have been enough to keep VOCs and PM2.5 concentration levels at acceptable values most of the studied time. However, results revealed that 25% of a specific timeframe, the occupants have been exposed to concentration levels of CO2 above 1000 parts per million (ppm), which are considered potentially hazardous conditions.

Pollution of the Atmosphere of Chelyabinsk by Transport Emissions of Non-Exhaust Origin

The aim of the study was to assess the harmful emissions of non-exhaust origin in Chelyabinsk. On asphalt roads 75% of the harmful emissions were 0.3 µm particulate matter. Removing 30 m from the roadway reduced the concentration of harmful substances by 5-7 times. By 2030, the number of vehicles in Chelyabinsk will increase by 25%. This will increase the amount of harmful emissions from tire and roadway wear by 20 tons per year.

Association Between Bedroom Particulate Matter Filtration and Changes in Airway Pathophysiology in Children With Asthma

To identify the measurable physiologic changes in the small airways of children with asthma, when employing a 2.5 µm particulate matter (PM2.5) filtration device in their bedrooms.The population enrolled includes children with mild or moderate asthma who live in a suburb of Shanghai, China, during a low-ozone season. A total of 43 children (5–13 years old; 60% boys) are included in the analysis.Patients are randomly assigned into either arm of a double-blind crossover study design with 3 consecutive 14 day periods of true filtration-washout-sham filtration or the reverse order. Impulse oscillometry, spirometry, and fractional exhaled nitric oxide (FeNO) were measured before and after each intervention, and peak flow was measured twice per day at home.PM2.5 concentrations were moderately high (28.6-69.8 μ g/m3) among the enrollees. A decrease in PM2.5 concentration by 63.4% was noted in true filtration bedrooms, when compared with sham filtration. True filtration was associated with improved airway mechanics, as measured by impulse oscillometry (a 22% to 43% decrease in resonant frequency, small airway resistance, and total airway resistance and 73% increase in airway reactance), FeNO, (27.6% decrease) and peak flow measurement (1.6% increase). These airway parameters were significantly associated with bedroom particulate matter reduction. Statistical significance was only noted in children without eosinophilic airway inflammation at the baseline (an absolute eosinophil count of 450 cells per μL and FeNO >35 parts per billion). No large airway parameters (forced expiratory volume in 1 second, forced vital capacity, and forced expiratory volume in 1 second to forced vital capacity) differed after 14 days of true filtration.PM2.5 filtration in the bedroom may improve airway mechanics and inflammation in pediatric patients with asthma who do not have eosinophilic inflammation.With this study, the authors expand on previous work by the same group that revealed 1 night of HEPA air filtration improved airway mechanics in healthy adults. The results after 2 weeks indicate a promising intervention for children with noneosinophilic asthma. The authors carefully controlled for a number of confounders, including intercurrent illness, asthma exacerbations, seasonal variation, ozone levels, inhaled corticosteroid use, and secondhand smoke exposure. In future studies, researchers should address patients in different environmental conditions with a larger sample size, for a longer intervention period, before formal recommendations can be made.

How do landscape elements affect public health in subtropical high-density city: The pathway through the neighborhood physical environmental factors

Purposes of this study are to explore associations between neighborhood landscape elements and public health in a subtropical high-density urban context, elucidate mediating effects of physical environmental factors, and propose corresponding neighborhood renewal strategies.Nine sampling sites were selected in Guangzhou, China, and public health data were collected from 438 participating residents using the MOS item short from health survey (SF-36 scale). Landscape elements of the neighborhoods, including greenness, blue spaces, walking trail systems, public squares, garden architecture, and dedicated sports spaces were mapped by unmanned aerial vehicle surveys. Seven physical environmental factors were measured: the heat stress index (HSI), relative humidity (RH), average wind speed (AWS), negative oxygen ions (NOI), <2.5 μM particulate matter (PM2.5), illumination (I), and noise (N). General linear models were used to explore differences between neighborhoods in landscape elements. Relationships between public health and both landscape elements and physical environmental factors, as well as the mediating pathways involved, were explored by correlation analysis and Mediation analyses.In subtropical high-density neighborhood, I, RH, HSI, NOI, and PM2.5 were significantly correlated with public health in the neighborhoods, as were greenness, blue spaces, walking trail systems, and public squares. Multiple mediation analysis showed that greenness, blue spaces and public squares significantly affected public health, with mediation by I, HSI and NOI. Landscape elements have close associations with public health, mainly mediated by effects on light, thermal, and atmospheric environments. These closely related landscape elements and physical environments need careful attention in neighborhood renewal efforts.

Long- and short-term air pollution exposure shortens telomere length in a population of hypersusceptible subjects

BACKGROUND AND AIM: Reduction in telomere length (TL) has been documented in subjects affected by age-related diseases (e.g., cancer, cardiovascular diseases) and has been associated to oxidative stress and systemic inflammation, claimed also as potential mechanisms underlying health effects of air pollution exposure, especially particulate matter (PM). We aim to determine the effects of both short- and long-term exposure to PM ≤10µm (PM10) on TL in a well-characterized population (SPHERE project). METHODS: About 1,800 subjects with overweight/obesity were recruited in Milan (Italy) in 2010-2015, completed a questionnaire and donated a 15 mL blood sample. TL was measured (as T/S ratio) by real-time PCR. Each subject was assigned air pollution and meteorological daily data based on his/her residential address. Multivariate mixed-effects linear models with a random intercept on PCR plate were applied. RESULTS:We observed a -2.8% change in TL [95% confidence interval (CI): -5.3; -0.8) per 10 µg/m3 increase in PM10 at the day of blood sampling (lag0). A similar pattern was apparent up to 12 days before recruitment (lag12), with the highest reduction observed at lag6 (-4.3, 95%CI: -6.9; -1.7). When considering moving averages of exposure levels in days preceding recruitment, we observed percent changes in TL ranging from -2.1 (lag0-1) to -8.5 (lag0-12). Long-term PM10 exposure was associated to a -14.9% TL reduction (95%CI: -29.4; -0.5) per 10 µg/m3 increase in annual average PM10 levels. The association between short-term exposure and TL remained practically unchanged when we additionally adjusted for long-term exposure (-6.2%, 95%CI: -11.2; -1.3 at lag0-14). CONCLUSIONS:Our results consistently show that both long- and short-term air pollution exposure shortens TL in a population of hypersusceptible subjects, thus shedding light on the potential mechanisms responsible for the excess of age-related diseases that is known to be associated with air pollution exposure. KEYWORDS: air pollution, particulate matter (PM), telomere length (TL), overweight, obesity, hypersusceptible

Using Bayesian time-stratified case-crossover models to examine associations between air pollution and “asthma seasons” in a low air pollution environment

BACKGROUND AND AIM: Many areas of the United States have air pollution levels typically below Environmental Protection Agency (EPA) regulatory limits. However, despite evidence suggesting temporally-misaligned intra-annual periods of relative asthma burden, “asthma seasons”, most studies of the health effects of air pollution use meteorological (e.g., warm/cool) or astronomical (e.g., solstice/equinox) definitions of seasons. We introduce asthma seasons to elucidate whether air pollutants were associated with seasonal differences in asthma emergency department (ED) visits in a low air pollution environment. METHODS: Within a Bayesian time-stratified case-crossover framework, we quantified associations between highly resolved estimates of six criteria air pollutants and asthma ED visits among 66,092 children ages 5-19 living in South Carolina (SC) census tracts over 2005-2014. Asthma seasons were defined by a late, short, and medium burden (16.5 visits/day) Winter, an early and short Spring with medium-high burden (18.9 visits/day), an early and low burden (9.4 visits/day) Summer, and an early and long Fall with high burden (23.5 visits/day). RESULTS:Coarse particulates (particulate matter 10μm and 2.5μm: PM10-2.5) and nitrogen oxides (NOx) may contribute to asthma ED visits across years, but were particularly implicated in the highest burden Fall. Allergenic antigens of respirable size from Fall-blooming plants (e.g., ragweed) should be further investigated as a potentially salient seasonal PM10-2.5 component. Fine particulate matter (2.5μm: PM2.5) was only associated in the lowest-burden Summer. Relatively cool and dry conditions in the Summer often following thunderstorms were associated with increased odds. Few significant associations in the medium-burden Winter and Spring suggest other drivers (e.g., viruses in Winter) for each, respectively. CONCLUSIONS:Even in a low pollution area, there were acute health effects associated with criteria air pollution, but mainly in the Summer and Fall asthma seasons. Future research should explicitly investigate local asthma seasons as well as the seasonal components of PM and other mixtures. KEYWORDS: asthma, allergies, air pollution, particulate matter, respiratory outcomes, environmental epidemiology

Thermal Extraction of Polycyclic Aromatic Hydrocarbons from Atmospheric 2.5 μm Particulate Matter Collected on a Filter Paper Using a High-Temperature Headspace Method.

Recently, owing to the performance improvement of the headspace (HS)-sampling devices and its consumables, HS vial samples can be analyzed at temperatures up to 300°C. Some studies have attempted to analyze polycyclic aromatic hydrocarbons (PAHs) in atmospheric 2.5 μm particulate matter (PM 2.5) collected on a filter paper by gas chromatography/mass spectrometry (GC/MS) coupled with thermal desorption device. However, no studies have reported the use of an HS-sampling device to quantify PAHs in PM 2.5 filter paper. In this study, we found that the quantification of PAH analysis using HS-GC/MS can be improved by the following steps, so that the accuracy becomes almost the same as that of a solvent-extraction method: 1) replacement of the air in the HS vial with nitrogen, 2) limiting the solvent to toluene, 3) using the hydrolyzed polyimide-covered septum, and 4) optimization of the heating temperature and heating time of the HS vial. As a result, we succeeded in protecting PAHs in an HS vial at a high temperature and in creating an analysis method with a high recovery rate and high repeatability; the limit of quantitation of each PAH in this method was 5.4 pg m-3 in the case of a volume of 10080 m3 of air being collected on the filter paper.