This study aimed to quantify the efficiency of deep bag and electrostatic filters, and assess the influence of ventilation systems using these filters on indoor fine (<2.5 μm) and ultrafine particle ...concentrations in commercial office buildings. Measurements and modelling were conducted for different indoor and outdoor particle source scenarios at three office buildings in Brisbane, Australia. Overall, the in-situ efficiency, measured for particles in size ranges 6–3000 nm, of the deep bag filters ranged from 26.3 to 46.9% for the three buildings, while the in-situ efficiency of the electrostatic filter in one building was 60.2%. The highest PN and PM2.5 concentrations in one of the office buildings (up to 131% and 31% higher than the other two buildings, respectively) were due to the proximity of the building's HVAC air intakes to a nearby bus-only roadway, as well as its higher outdoor ventilation rate. The lowest PN and PM2.5 concentrations (up to 57% and 24% lower than the other two buildings, respectively) were measured in a building that utilised both outdoor and mixing air filters in its HVAC system. Indoor PN concentrations were strongly influenced by outdoor levels and were significantly higher during rush-hours (up to 41%) and nucleation events (up to 57%), compared to working-hours, for all three buildings. This is the first time that the influence of new particle formation on indoor particle concentrations has been identified and quantified. A dynamic model for indoor PN concentration, which performed adequately in this study also revealed that using mixing/outdoor air filters can significantly reduce indoor particle concentration in buildings where indoor air was strongly influenced by outdoor particle levels. This work provides a scientific basis for the selection and location of appropriate filters and outdoor air intakes, during the design of new, or upgrade of existing, building HVAC systems. The results also serve to provide a better understanding of indoor particle dynamics and behaviours under different ventilation and particle source scenarios, and highlight effective methods to reduce exposure to particles in commercial office buildings.
•Investigated the efficiency of different filters in commercial ventilation systems.•Mixing/outdoor air filters significantly reduced indoor particle concentration.•Results provide a better understanding of indoor particle dynamics and behaviour.•Reveals the impact of different ventilation and particle source scenarios.
It is known that ultrafine particles (UFP, particles smaller than 0.1 μm) can penetrate deep into the lungs and potentially have adverse health effects. However, epidemiological data on the health ...effects of UFP is limited. Therefore, our objective was to test the hypothesis that exposure to UFPs is associated with respiratory health status and systemic inflammation among children aged 8 to 11 years.
We conducted a cross-sectional study among 655 children (43.3% male) attending 25 primary (elementary) schools in the Brisbane Metropolitan Area, Australia. Ultrafine particle number concentration (PNC) was measured at each school and modelled at homes using Land Use Regression to derive exposure estimates. Health outcomes were respiratory symptoms and diagnoses, measured by parent-completed questionnaire, spirometric lung function, exhaled nitric oxide (FeNO), and serum C reactive protein (CRP). Exposure-response models, adjusted for potential personal and environmental confounders measured at the individual, home and school level, were fitted using Bayesian methods.
PNC was not independently associated with respiratory symptoms, asthma diagnosis or spirometric lung function. However, PNC was positively associated with an increase in CRP (1.188-fold change per 1000 UFP cm−3 day/day (95% credible interval 1.077 to 1.299)) and an increase in FeNO among atopic participants (1.054 fold change per 1000 UFP cm−3 day/day (95% CrI 1.005 to 1.106)).
UFPs do not affect respiratory health outcomes in children but do have systemic effects, detected here in the form of a positive association with a biomarker for systemic inflammation. This is consistent with the known propensity of UFPs to penetrate deep into the lung and circulatory system.
•Epidemiological evidence on ultrafine particles (UFP) and human health is limited.•Only a handful of studies investigating the health impact of UFP in children.•We conducted a cross-sectional study among 655 children from 25 primary schools.•UFP do not affect respiratory health in children but do have systematic effects.•We showed a positive association with a biomarker for systemic inflammation.
While the effects of ambient air pollution on health have been studied extensively in many developed countries, few studies have been conducted in Vietnam, where the population is exposed to high ...levels of airborne particulate matter. The aim of our study was to examine the short-term effects of PM10, PM2.5, and PM1 on respiratory admissions among young children in Hanoi. Data on daily admissions from the Vietnam National Hospital of Paediatrics and daily records of PM10, PM2.5, PM1 and other confounding factors as NO2, SO2, CO, O3 and temperature were collected from September 2010 to September 2011. A time-stratified case-crossover design with individual lag model was applied to evaluate the associations between particulate air pollution and respiratory admissions. Significant effects on daily hospital admissions for respiratory disease were found for PM10, PM2.5 and PM1. An increase in 10μg/m3 of PM10, PM2.5 or PM1 was associated with an increase in risk of admission of 1.4%, 2.2% or 2.5% on the same day of exposure, respectively. No significant difference between the effects on males and females was found in the study. The study demonstrated that infants and young children in Hanoi are at increased risk of respiratory admissions due to the high level of airborne particles in the city's ambient air.
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•First study on human health impact of air pollution in the north of Vietnam•Elevated levels of PM10, PM2.5 or PM1 were associated with respiratory admissions.•The smaller PM could have stronger impact on children respiratory admission.•Urgent intervention measures are needed to control air pollution in Vietnam.
Abstract
The number of respiratory particles emitted during different respiratory activities is one of the main parameters affecting the airborne transmission of respiratory pathogens. Information on ...respiratory particle emission rates is mostly available for adults (few studies have investigated adolescents and children) and generally involves a limited number of subjects. In the present paper we attempted to reduce this knowledge gap by conducting an extensive experimental campaign to measure the emission of respiratory particles of more than 400 children aged 6 to 12 years while they pronounced a phonetically balanced word list at two different voice intensity levels (“speaking” and “loudly speaking”). Respiratory particle concentrations, particle distributions, and exhaled air flow rates were measured to estimate the respiratory particle emission rate. Sound pressure levels were also simultaneously measured. We found out that median respiratory particle emission rates for speaking and loudly speaking were 26 particles s
−1
(range 7.1–93 particles s
−1
) and 41 particles s
−1
(range 10–146 particles s
−1
), respectively. Children sex was significant for emission rates, with higher emission rates for males during both speaking and loudly speaking. No effect of age on the emission rates was identified. Concerning particle size distributions, for both respiratory activities, a main mode at approximately 0.6 µm and a second minor mode at < 2 µm were observed, and no differences were found between males and females. This information provides important input parameters in predictive models adopted to estimate the transmission risk of airborne pathogens in indoor spaces.
Living in greener areas has many health benefits, but evidence concerning the effects on blood pressure remains mixed. We sought to assess associations between community greenness and both blood ...pressure and hypertension in Chinese urban dwellers, and whether the associations were mediated by air pollution, body mass index, and physical activity.
We analyzed data from 24,845 adults participating in the 33 Communities Chinese Health Study, which was conducted in Northeastern China during 2009. We measured each participant's blood pressure according to a standardized protocol. We assessed community greenness using two satellite-derived vegetation indexes – the Normalized Difference Vegetation Index (NDVI) and the Soil Adjusted Vegetation Index (SAVI). Particulate matter ≤2.5 μm and nitrogen dioxide were used as proxies of ambient air pollution. We applied generalized linear mixed models to investigate the association between greenness and blood pressure. We also performed mediation analyses.
Living in greener areas was associated with lower blood pressure and hypertension prevalence; an interquartile range increase in both NDVI500-m and SAVI500-m were significantly associated with reductions in systolic blood pressure of 0.82 mm Hg (95% CI: −1.13, −0.51) and 0.89 mm Hg (95% CI: −1.21, −0.57), respectively. The same increases in greenness were also significantly associated with a 5% (95% CI: 1%, 8%) and 5% (95% CI: 1%, 9%) lower odds of having hypertension, respectively. These associations remained consistent in sensitivity analyses. The associations were stronger among women than men. Air pollutants and body mass index partly mediated the associations, but there was no evidence of mediation effects for physical activity.
Our findings indicate beneficial associations between community greenness and blood pressure in Chinese adults, especially for women. Air pollution and body mass index only partly mediated the associations.
•Evidence on greenness and blood pressure is scarce in China.•We conducted a cross-sectional study in 24,845 Chinese urban dwellers.•Associations of greenness with blood pressure metrics were examined.•Greenness levels were beneficially associated with blood pressure.•Air pollution and BMI partly mediated the greenness-blood pressure association.
Air ionizers are increasingly being used to clean indoor environments of particle pollution. We tested the efficiency of a small negative ion generator (Aironic AH-202) in removing ultrafine ...particles from indoor environments. A high-flow air filter fitted with a HEPA filter was used to compare the removal efficiencies. We estimated the percentage of particles removed when the ionizer was operated within a closed chamber of volume 1 m3, in a closed unventilated room of volume 20 m3 and in three force-ventilated rooms of volume 32, 45 and 132 m3. The closed chamber studies were conducted with ambient particles and with smoke at particle number concentrations of 5 × 103 and 7 × 104 cm−3, respectively. In both cases, 70% of the particles were removed by the ionizer in 15 min. In general, the particle removal efficiency of both the ionizer and the air filter decreased as the room size increased. Both devices were also more effective in unventilated rooms than in ventilated rooms. The most important finding in this study was that, while the air filter was more effective than the ionizer in the two small rooms, the ionizer was clearly more effective than the air filter in the three largest rooms. We conclude that air ionizers are more suited than high-flow air filters in removing ultrafine particles from rooms larger than about 25 m3. The investigation also showed that small ions produced by the ionizer, placed in one room, were carried through the air conditioning system into other rooms, effectively removing particles from the air in these rooms in the process.
•Efficiency of an air ionizer in airborne particle removal was investigated.•Studies were conducted in both ventilated and unventilated rooms.•Efficiency was determined as a function of room size.•Transport of ions between rooms through the ventilation system was investigated.•Efficiencies were compared against a high-flow particle filter.
Can mitigating only particle mass, as the existing air quality measures do, ultimately lead to reduction in ultrafine particles (UFP)? The aim of this study was to provide a broader urban perspective ...on the relationship between UFP, measured in terms of particle number concentration (PNC) and PM2.5 (mass concentration of particles with aerodynamic diameter < 2.5 μm) and factors that influence their concentrations. Hourly average PNC and PM2.5 were acquired from 10 cities located in North America, Europe, Asia, and Australia over a 12-month period. A pairwise comparison of the mean difference and the Kolmogorov-Smirnov test with the application of bootstrapping were performed for each city. Diurnal and seasonal trends were obtained using a generalized additive model (GAM). The particle number to mass concentration ratios and the Pearson's correlation coefficient were calculated to elucidate the nature of the relationship between these two metrics.
Results show that the annual mean concentrations ranged from 8.0 × 103 to 19.5 × 103 particles·cm−3 and from 7.0 to 65.8 μg·m−3 for PNC and PM2.5, respectively, with the data distributions generally skewed to the right, and with a wider spread for PNC. PNC showed a more distinct diurnal trend compared with PM2.5, attributed to the high contributions of UFP from vehicular emissions to PNC. The variation in both PNC and PM2.5 due to seasonality is linked to the cities' geographical location and features. Clustering the cities based on annual median concentrations of both PNC and PM2.5 demonstrated that a high PNC level does not lead to a high PM2.5, and vice versa. The particle number-to-mass ratio (in units of 109 particles·μg−1) ranged from 0.14 to 2.2, >1 for roadside sites and <1 for urban background sites with lower values for more polluted cities. The Pearson's r ranged from 0.09 to 0.64 for the log-transformed data, indicating generally poor linear correlation between PNC and PM2.5. Therefore, PNC and PM2.5 measurements are not representative of each other; and regulating PM2.5 does little to reduce PNC. This highlights the need to establish regulatory approaches and control measures to address the impacts of elevated UFP concentrations, especially in urban areas, considering their potential health risks.
Urbanisation and industrialisation led to the increase of ambient particulate matter (PM) concentration. While subsequent regulations may have resulted in the decrease of some PM matrices, the ...simultaneous changes in climate affecting local meteorological conditions could also have played a role. To gain an insight into this complex matter, this study investigated the long-term trends of two important matrices, the particle mass (PM2.5) and particle number concentrations (PNC), and the factors that influenced the trends. Mann-Kendall test, Sen’s slope estimator, the generalised additive model, seasonal decomposition of time series by LOESS (locally estimated scatterplot smoothing) and the Buishand range test were applied. Both PM2.5 and PNC showed significant negative monotonic trends (0.03–0.6 μg m−3. yr−1 and 0.40–3.8 × 103 particles. cm−3. yr−1, respectively) except Brisbane (+0.1 μg m−3. yr−1 and +53 particles. cm−3. yr−1, respectively). For the period covered in this study, temperature increased (0.03–0.07 °C.yr−1) in all cities except London; precipitation decreased (0.02–1.4 mm. yr−1) except in Helsinki; and wind speed was reduced in Brisbane and Rochester but increased in Helsinki, London and Augsburg. At the change-points, temperature increase in cold cities influenced PNC while shifts in precipitation and wind speed affected PM2.5. Based on the LOESS trend, extreme events such as dust storms and wildfires resulting from changing climates caused a positive step-change in concentrations, particularly for PM2.5. In contrast, among the mitigation measures, controlling sulphur in fuels caused a negative step-change, especially for PNC. Policies regarding traffic and fleet management (e.g. low emission zones) that were implemented only in certain areas or in a progressive uptake (e.g. Euro emission standards), resulted to gradual reductions in concentrations. Therefore, as this study has clearly shown that PM2.5 and PNC were influenced differently by the impacts of the changing climate and by the mitigation measures, both metrics must be considered in urban air quality management.
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•Both PM2.5 and PNC had a monotonic downward trend in all cities except Brisbane.•Extreme events due to changing climates caused positive step-changes to PM2.5.•Negative step-changes in PNC were observed upon regulation of sulphur in fuels.•Gradual reduction of PM2.5 and PNC was achieved by traffic and fleet management.
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