Understanding Spatial Variability of Air Quality in Sydney: Part 2—A Roadside Case Study

Chronic maternal exposure to low-dose PM2.5 impacts cognitive outcomes in a sex-dependent manner

There is no safe level of air pollution for human health. Traffic-related particulate matter (PM2.5) is a major in-utero toxin, mechanisms of action of which are not fully understood. BALB/c dams were exposed to an Australian level of traffic PM2.5 (5 µg/mouse/day, intranasal, 6 weeks before mating, during gestation and lactation). Male offspring had reduced memory in adulthood, whereas memory was normal in female littermates, similar to human responses. Maternal PM2.5 exposure resulted in oxidative stress and abnormal mitochondria in male, but not female, brains. RNA-sequencing analysis showed unique sex-related changes in newborn brains. Two X-chromosome-linked histone lysine demethylases, Kdm6a and Kdm5c, demonstrated higher expression in female compared to male littermates, in addition to upregulated genes with known functions to support mitochondrial function, synapse growth and maturation, cognitive function, and neuroprotection. No significant changes in Kdm6a and Kdm5c were found in male littermates, nor other genes, albeit significantly impaired memory function after birth. In primary foetal cortical neurons, PM2.5 exposure suppressed neuron and synaptic numbers and induced oxidative stress, which was prevented by upregulation of Kdm6a or Kdm5c. Therefore, timely epigenetic adaptation by histone demethylation to open DNA for translation before birth may be the key to protecting females against prenatal PM2.5 exposure-induced neurological disorders, which fail to occur in males associated with their poor cognitive outcomes.

Simulating the impact of particulate matter exposure on health-related behaviour: A comparative study of stochastic modelling and personal monitoring data

Epidemiological and exposure studies concerning particulate matter (PM) often rely on data from sparse governmental stations. While low-cost personal monitors have some drawbacks, recent developments have shown that they can provide fairly accurate and fit-for-purpose data. Comparing a stochastic, i.e., agent-based model (ABM), with environmental, biometric and activity data, collected with personal monitors, could provide insight into how the two approaches assess PM exposure and dose. An ABM was constructed, simulating a PM exposure/dose assessment of 100 agents. Their actions were governed by inherent probabilities of performing an activity, based on population data. Each activity was associated with an intensity level, and a PM pollution level. The ABM results were compared with real-world results. Both approaches had comparable results, showing similar trends and a mean dose. Discrepancies were seen in the activities with the highest mean dose values. A stochastic model, based on population data, does not capture well some specifics of a local population. Combined, personal sensors could provide input for calibration, and an ABM approach can help offset a low number of participants. Implementing a function of agents influencing others transport choice, increased the importance of cycling/walking in the overall dose estimate. Activists, agents with an increased transport influence, did not play an important role at low PM levels. As concentrations rose, higher shares of activists (and their influence) caused the dose to increase. Simulating a person's PM exposure/dose in different scenarios and activities in a virtual environment provides researchers and policymakers with a valuable tool.

Effects of green infrastructure on the dispersion of PM2.5 and human exposure on urban roads

Urban green infrastructure (GI) has been widely demonstrated to effectively improve air quality in the built environment. However, due to the lack of comparative studies of the effects of different GI forms on PM_2.5 dispersion, optimal GI designs suitable for different urban road types currently remain unclear. In this study, we adopted different roadside GI types in Hangzhou city as case studies and used the ENVI-met model to compare the effects of the different GI forms on PM_2.5 dispersion and human exposure to PM_2.5. The results indicated that 1) In open roads, the concave-shaped GI type could effectively reduce PM_2.5 aggregation and human exposure on motorways, and the all-tree GI type performed the best in terms of sidewalk PM_2.5 purification. 2) In street canyons, green roof and green screen were highly conducive to PM_2.5 concentration reduction under commuter exposure compared with traditional green solutions. 3) There were trade-offs in the GI-PM_2.5 interaction. GI types which can reduce pedestrian exposure tend to increase exposure in motorways. The same GI type deployed along the two different road types could yield completely opposite dispersion effects. Novel GI types had better environmental performance and relatively high economic cost. All decision-making should be based on the trade-offs between the advantages and disadvantages of GI. Our study also highlights the importance of comprehensive consideration of GI and road types and local wind conditions in future urban road planning and GI applications.

Modeling of the effects of porous and solid barriers along the road from traffic emissions in idealized urban street canyons

In this paper, numerical modeling of concentration propagation using various types of barriers and trees with porosity properties in an idealized urban canyon to protect nearby houses was considered. To solve this problem, a modification of the Reynolds-averaged Navier-Stokes equations is used to take into account the porous medium. To validate the mathematical model and the numerical algorithm, a test problem was solved without taking into account various barriers with a source of pollution. After validation, the main problem was solved, describing the emission process of pollutants between houses using different types of grass barriers and trees with different porosity properties. The numerical simulation data were compared with the calculated values using various types of grass barriers and trees. Taking into account the optimal properties of porous trees in combination with barriers, it was found that height of the barrier itself has a minor role in the spread of pollutants.

Comparison of exposure to traffic-related pollutants on different commuting routes to a primary school in Jinan, China

Traffic-related pollutants seriously affect human health, and the commute time to and from school is the time when students are exposed greatest to traffic pollution sources. Field measurements were conducted with hand-held instruments while walking along two selected commuting routes in winter and spring. The measured data were then compared with background monitoring data, and the respiratory deposition dose (RDD) was calculated to assess the exposure risk. Particulate matter intake from 2018 to 2020 was calculated. In winter, the average concentrations of PM_2.5 and PM₁₀ were higher in the afternoon than in the morning. The highest concentration was 2.94 times greater than the background value. The low-concentration distribution area of the low-traffic route that is off the main road (route B) was more significant than that of the high-traffic route that is near the main road (route A). Moreover, the RDD of route B was consistently lower than that of route A, while the average annual amount of PM_2.5 inhalation on route B in 3 years was 16.3% lower than that on route A. Overall, route B is more suitable than route A for students to commute on foot. Based on the findings, a walking route located within a community is a good choice.

Screening of Plant Species Response and Performance for Green Belt Development: Implications for Semi-Urban Ecosystem Restoration

Screened plant species with potential for green belt development can act as eco-sustainable tools for restoring the polluted ecosystem. Eight plant species from two study locations in Ado-Odo, Ota, Ogun State, Nigeria, were examined to identify their air pollution response and performance by deploying two air pollution indices, namely air pollution tolerance index (APTI) and anticipated performance index (API). APTI results identified all screened plants as sensitive species suitable as bio-indicators of air pollution, with Ficus auriculata (2.42) common to the non-industrial location being the most sensitive. API scores categorized Ficus auriculata (56.25%) as a moderate performer, while Syzygium malaccense (75%) and Mangifera indica (75%) were identified as very good performers, suitable for green belt development. The relationship between each biochemical parameter with APTI was investigated using regression analysis and two-way analysis of variance. The model result showed a significant relationship between each biochemical parameter with APTI, and relative water content had the highest influence on APTI (R2 = 0.99436). Both indices (APTI and API) are suitable for screening and recommending native plant species for cultivation in the polluted environment, thus promoting ecological restoration. Hence, Syzygium malaccense, Mangifera indica and Ficus auriculata, respectively, were recommended for green belts design. Further intensive screening to identify tolerant species and best to excellent performer’s trees suitable for restoring the ecosystem is advised.

School neighbourhood and compliance with WHO-recommended annual NO2 guideline: A case study of Greater London

Despite several national and local policies towards cleaner air in England, many schools in London breach the WHO-recommended concentrations of air pollutants such as NO₂ and PM_2.5. This is while, previous studies highlight significant adverse health effects of air pollutants on children's health. In this paper we adopted a Bayesian spatial hierarchical model to investigate factors that affect the odds of schools exceeding the WHO-recommended concentration of NO₂ (i.e., 40 μg/m³ annual mean) in Greater London (UK). We considered a host of variables including schools' characteristics as well as their neighbourhoods' attributes from household, socioeconomic, transport-related, land use, built and natural environment characteristics perspectives. The results indicated that transport-related factors including the number of traffic lights and bus stops in the immediate vicinity of schools, and borough-level bus fuel consumption are determinant factors that increase the likelihood of non-compliance with the WHO guideline. In contrast, distance from roads, river transport, and underground stations, vehicle speed (an indicator of traffic congestion), the proportion of borough-level green space, and the area of green space at schools reduce the likelihood of exceeding the WHO recommended concentration of NO₂. We repeated our analysis under a hypothetical scenario in which the recommended concentration of NO₂ is 35 μg/m³ - instead of 40 μg/m³. Our results underscore the importance of adopting clean fuel technologies on buses, installing green barriers, and reducing motorised traffic around schools in reducing exposure to NO₂ concentrations in proximity to schools. Also, our findings highlight the presence of environmental inequalities in the Greater London area. This study would be useful for local authority decision making with the aim of improving air quality for school-aged children in urban settings.

Identification of air pollution hotspots in urban areas - An innovative approach using monitored concentrations data

Critical assessment of spatio-temporal variations in pollution levels is a crucial step for identifying and prioritizing air pollution hotspots (APH) in urban areas. There is no universally accepted methodology for defining and delineating air pollution hotspot which can be source-specific, pollutant-specific and time-specific. The present research article is an attempt to develop a protocol for identifying APH for any pollutant within a city where-in three criteria-based innovative methodology has been derived. The three criteria are frequency of exceedance (% of days), scale of exceedance and consistency in exceedance (consecutive number of days) to the specified standards that need to be met continuously for at least three years. The suggested methodology has been applied on a three-year database (2018-2021) of 37 continuous ambient air quality stations to identify PM_2.5 specific APH. The analysis indicates 11 APH in April, 9 in May, 2 in June and almost the entire city during the October-February months. Given prioritization of implementation of control actions, the identified APH during summer has been further physically examined to map source activity types and their suitability for ambient air quality monitoring stations as per the guidelines. The APH can be the priority areas for the implementation of control actions by urban local bodies. The management of air pollution at these priority areas would be more effective instead of city-scale management practice, which is difficult to implement and monitor.

A review of strategies for mitigating roadside air pollution in urban street canyons

Urban street canyons formed by high-rise buildings restrict the dispersion of vehicle emissions, which pose severe health risks to the public by aggravating roadside air quality. However, this issue is often overlooked in city planning. This paper reviews the mechanisms controlling vehicle emission dispersion in urban street canyons and the strategies for managing roadside air pollution. Studies have shown that air pollution hotspots are not all attributed to heavy traffic and proper urban design can mitigate air pollution. The key factors include traffic conditions, canyon geometry, weather conditions and chemical reactions. Two categories of mitigation strategies are identified, namely traffic interventions and city planning. Popular traffic interventions for street canyons include low emission zones and congestion charges which can moderately improve roadside air quality. In comparison, city planning in terms of building geometry can significantly promote pollutant dispersion in street canyons. General design guidelines, such as lower canyon aspect ratio, alignment between streets and prevailing winds, non-uniform building heights and ground-level building porosity, may be encompassed in new development. Concurrently, in-street barriers are widely applicable to rectify the poor roadside air quality in existing street canyons. They are broadly classified into porous (e.g. trees and hedges) and solid (e.g. kerbside parked cars, noise fences and viaducts) barriers that utilize their aerodynamic advantages to ease roadside air pollution. Post-evaluations are needed to review these strategies by real-world field experiments and more detailed modelling in the practical perspective.

Differential inflammatory and toxic effects in-vitro of wood smoke and traffic-related particulate matter from Sydney, Australia

BACKGROUND

It is well known that PM_2.5 generated by traffic or burning wood is pro-inflammatory and induces various adverse health outcomes in humans. In Sydney, New South Wales, Australia, the main anthropogenic contributors to particulate matter (PM) air pollution are wood combustion heaters, on-road vehicles, and coal-fired power stations. However, the relative toxicity of these local sources has not to date been investigated.

METHOD

PM_2.5 was collected on filters from the same sampling site in Liverpool, one suburb of Sydney. According to the positive matrix factorisation and collection season, filters were representative of either day with high traffic-related air pollution (TRAP), wood smoke, or both TRAP and woodsmoke (mixed air pollution). The elemental composition of the PM was assessed by accelerator-based ion beam analysis techniques (i.e. PIXE & PIGE) and size by Dynamic Light Scattering. Toxicity and inflammation were assessed in-vitro in human bronchial epithelial cells by measuring interleukin-6 (IL-6), interleukin-8 (IL-8) release, and MTT.

RESULTS

Mixed air pollution (TRAP/wood smoke) PM had more nanometer (nm) sized PM than the other two groups. Using an in-vitro model of the lungs, the mixed air pollution PM was the most toxic, whereas the PM from woodsmoke induced greater IL-6 release than TRAP PM. There was no difference in the induction of IL-8 between the three sources of PM.

CONCLUSION

Marked differences occur in the cellular response to PM from different sources, with differences in both toxicity and inflammation.

Green infrastructure for air quality improvement in street canyons

Street canyons are generally highly polluted urban environments due to high traffic emissions and impeded dispersion. Green infrastructure (GI) is one potential passive control system for air pollution in street canyons, yet optimum GI design is currently unclear. This review consolidates findings from previous research on GI in street canyons and assesses the suitability of different GI forms in terms of local air quality improvement. Studies on the effects of various GI options (trees, hedges, green walls, green screens and green roofs) are critically evaluated, findings are synthesised, and possible recommendations are summarised. In addition, various measurement methods used for quantifying the effectiveness of street greening for air pollution reduction are analysed. Finally, we explore the findings of studies that have compared plant species for pollution mitigation. We conclude that the influences of different GI options on air quality in street canyons depend on street canyon geometry, meteorological conditions and vegetation characteristics. Green walls, green screens and green roofs are potentially viable GI options in existing street canyons, where there is typically a lack of available planting space. Particle deposition to leaves is usually quantified by leaf washing experiments or by microscopy imaging techniques, the latter of which indicates size distribution and is more accurate. The pollutant reduction capacity of a plant species largely depends on its macromorphology in relation to the physical environment. Certain micromorphological leaf traits also positively correlate with deposition, including grooves, ridges, trichomes, stomatal density and epicuticular wax amount. The complexity of street canyon environments and the limited number of previous studies on novel forms of GI in street canyons mean that offering specific recommendations is currently unfeasible. This review highlights a need for further research, particularly on green walls and green screens, to substantiate their efficacy and investigate technical considerations.

Traffic exhaust to wildfires: PM2.5 measurements with fixed and portable, low-cost LoRaWAN-connected sensors

Air pollution with PM2.5 (particulate matter smaller than 2.5 micro-metres in diameter) is a major health hazard in many cities worldwide, but since measuring instruments have traditionally been expensive, monitoring sites are rare and generally show only background concentrations. With the advent of low-cost, wirelessly connected sensors, air quality measurements are increasingly being made in places where many people spend time and pollution is much worse: on streets near traffic. In the interests of enabling members of the public to measure the air that they breathe, we took an open-source approach to designing a device for measuring PM2.5. Parts are relatively cheap, but of good quality and can be easily found in electronics or hardware stores, or on-line. Software is open source and the free LoRaWAN-based "The Things Network" the platform. A number of low-cost sensors we tested had problems, but those selected performed well when co-located with reference-quality instruments. A network of the devices was deployed in an urban centre, yielding valuable data for an extended time. Concentrations of PM2.5 at street level were often ten times worse than at air quality stations. The devices and network offer the opportunity for measurements in locations that concern the public.

A Clean Air Plan for Sydney: An Overview of the Special Issue on Air Quality in New South Wales

This paper presents a summary of the key findings of the special issue of Atmosphere on Air Quality in New South Wales and discusses the implications of the work for policy makers and individuals. This special edition presents new air quality research in Australia undertaken by (or in association with) the Clean Air and Urban Landscapes hub, which is funded by the National Environmental Science Program on behalf of the Australian Government’s Department of the Environment and Energy. Air pollution in Australian cities is generally low, with typical concentrations of key pollutants at much lower levels than experienced in comparable cities in many other parts of the world. Australian cities do experience occasional exceedances in ozone and PM2.5 (above air pollution guidelines), as well as extreme pollution events, often as a result of bushfires, dust storms, or heatwaves. Even in the absence of extreme events, natural emissions play a significant role in influencing the Australian urban environment, due to the remoteness from large regional anthropogenic emission sources. By studying air quality in Australia, we can gain a greater understanding of the underlying atmospheric chemistry and health risks in less polluted atmospheric environments, and the health benefits of continued reduction in air pollution. These conditions may be representative of future air quality scenarios for parts of the Northern Hemisphere, as legislation and cleaner technologies reduce anthropogenic air pollution in European, American, and Asian cities. However, in many instances, current legislation regarding emissions in Australia is significantly more lax than in other developed countries, making Australia vulnerable to worsening air pollution in association with future population growth. The need to avoid complacency is highlighted by recent epidemiological research, reporting associations between air pollution and adverse health outcomes even at air pollutant concentrations that are lower than Australia’s national air quality standards. Improving air quality is expected to improve health outcomes at any pollution level, with specific benefits projected for reductions in long-term exposure to average PM2.5 concentrations.

Air Quality Impacts of Smoke from Hazard Reduction Burns and Domestic Wood Heating in Western Sydney

Air quality was measured in Auburn, a western suburb of Sydney, Australia, for approximately eighteen months during 2016 and 2017. A long open-path infrared spectrometer sampled path-averaged concentrations of several gaseous species, while other pollutants such as PM 2.5 and PM 10 were sampled by a mobile air quality station. The measurement site was impacted by a number of indoor wood-heating smoke events during cold winter nights as well as some major smoke events from hazard reduction burning in the spring of 2017. In this paper we compare the atmospheric composition during these different smoke pollution events and assess the relative overall impact on air quality from domestic wood-heaters and prescribed forest fires during the campaign. No significant differences in the composition of smoke from these two sources were identified in this study. Despite the hazard reduction burning events causing worse peak pollution levels, we find that the overall exposure to air toxins was greater from domestic wood-heaters due to their higher frequency and total duration. Our results suggest that policy-makers should place a greater focus on reducing wood-smoke pollution in Sydney and on communicating the issue to the public.