Air pollution from fine dust (PM2.5) poses severe risks to urban environments and human health in many cities, particularly in roadside areas. Urban green spaces can help reduce this pollution, but there is still limited research on the best way to design plant layouts for maximum dust removal. This study evaluated the performance of a specially designed urban garden in Bangkok, Thailand, for PM2.5 removal. A three-layer planting design, featuring species with high PM2.5 removal capacity from a screening of 73 plant species, was implemented beside a major traffic road. Measurements conducted during high-pollution periods showed an average removal efficiency of 14.89%, increasing up to 35% under high PM2.5 conditions. The garden improved microclimatic conditions, reducing air temperature by 1-2°C and increasing relative humidity by approximately 9.9%. Environmental parameters such as wind speed and direction significantly affected removal efficiency. Wind speeds between 1-3 m/s optimized dust capture, reaching efficiency levels of 15-18%, while speeds above 3.6 m/s resulted in a drop in efficiency. The annual PM2.5 dry deposition rate was calculated at 1.33 g/m2 ·y. These results demonstrate that strategic planting design and species selection can enhance nature-based solutions for urban air quality improvement.Implications: This study demonstrated that a newly designed urban green space can significantly reduce roadside PM2.5, especially during high-pollution periods. Using a multi-layer planting structure and species with high PM2.5 removal capacity, the garden achieved up to 35% reduction and accumulated substantial annual particulate matter. Seasonal wind patterns were also key determinants of removal efficiency. These results provide practical guidance for municipalities and urban planners seeking cost-effective, nature-based solutions for air quality improvement. Integrating targeted green infrastructure into urban design can enhance public health protection and strengthen long-term air pollution management.
Renewable diesel (RD) and sustainable aviation fuel (SAF) are lower-carbon alternatives to conventional petroleum fuels that have begun to enter the U.S. market at commercial scale, largely driven by policy. The most widely deployed forms of RD and SAF are hydrotreated lipids, produced by similar processes, using vegetable or waste oil as the feedstock. Both RD and SAF typically result in lower air pollutant emissions than their petroleum equivalents, especially particulate matter and sulfur oxides (SOx), however the quantity and location of these reductions are different. The dependence of both RD and SAF on the same pool of feedstock and production capacity means that in the near term, increased SAF production may come at the expense of RD. This study investigates the possible air quality effects of such a shift, with a focus on potential impacts in disadvantaged communities. We develop two emissions scenarios in California, for which diesel and aviation emissions are scaled to reflect policies that favor SAF or RD. The air quality associated with each emissions scenario is then simulated using a chemical transport model. Health impacts from the air quality exposure fields are estimated for three major urban areas and exposure disparities are calculated based on historical socioeconomic data. The results of this show minimal air quality and public health changes between the high SAF and high RD scenarios for the California cities analyzed in the present study because California's current diesel emission regulations limit the potential air quality benefit from RD. This suggests that air quality considerations should not be a dominant motivation when evaluating policy-driven shifts in the relative prevalence of RD and SAF in California. Other regions using less advanced diesel engine technology may see more significant air quality tradeoffs between SAF and RD.Implications: Hydrotreated alternative fuels like renewable diesel (RD) and sustainable aviation fuel (SAF) are entering the market at large scale, drawing from a limited global pool of feedstock (vegetable oil and non-fossil waste oils) and using similar production processes. Policymakers have explored expanding SAF consumption; likely near-term approaches to this would result in a commensurate reduction in RD. This paper evaluates whether this trade-off would cause significant impacts on air quality if it were to occur in California, where a SAF-focused policy change was considered in 2024. We find no significant regional air quality impact from such a shift.
A sensor‑based microsystem for monitoring air quality related to wildfire emissions has been developed for deployment in a distributed network in a remote community. The sensor microsystem is equipped with particulate matter (PM2.5), carbon monoxide, carbon dioxide, ozone, and total volatile organic compound (tVOC) sensors. Root-mean-squared error for PM2.5 of less than 5 ug/m3 has been estimated. An onboard microcontroller-based control system synchronizes sensor data acquisition and communications. The microsystem is designed for operations in forest locations surrounding a remote community where cellular or Wi-Fi signals are not available. Radio communication protocol in mesh networking has been developed and tested in the range of 1-5 km in urban areas with structural barriers and outdoor terrains with vegetation. The air monitoring microsystem is designed for standalone operation with solar power, with a panel size of 50 × 37 cm that can be mounted on treetop configurations. The microcontroller-based architecture is designed for smart monitoring of air quality for optimization of energy usage toward sustainable operations throughout spring to fall, and potentially through winter seasons. System architecture has been developed to integrate several air monitoring microsystems in a network deployment to provide real-time information on potential wildfire status within several tens of thousands of hectares of forest area surrounding a remote community.Implications: This manuscript reports an innovative technology that can be deployed in forest locations surrounding remote communities in the typical northwestern prairie region in Alberta, Canada. These sensor systems will provide real-time data for air quality and wildfire events based on sensor data acquisition from forestlands. The distributed low-cost sensor network will address large gaps in provincial and federal air quality monitoring networks and can potentially be integrated with national data warehouses. These systems will inform policy on public health risk mitigation, emissions monitoring, land use policy, forest management, and climate change policies.
This study examines how supply-chain circularity (SCC) translates into firm performance in Nigeria's synthetic-hair industry by testing a mediated pathway from SCC to resource-utilization efficiency (RUE) and onward to operational efficiency (OE). Motivated by the need to move beyond advocacy toward mechanism-focused evidence in developing-country contexts, we implemented a quantitative design comprising a structured questionnaire administered to industry personnel in Lagos (managers, supervisors, and production staff; N = 138) and a complementary public-perception survey of consumers (N = 382). Using Partial Least Squares Structural Equation Modeling (PLS-SEM) for the firm-side data and descriptive analysis for the consumer data, the results indicate that SCC does not exert a significant direct effect on OE; instead, SCC significantly enhances RUE, which in turn strongly improves OE, thereby validating a mediated SCC→RUE→OE mechanism consistent with the Natural Resource-Based View. Moreover, consumer evidence suggests that sustainability is salient, yet purchase decisions hinge on credible quality assurances, price fairness, hygiene and trust, alongside openness to disposal guidance. Collectively, these findings position resource-utilization efficiency as the transmission channel through which circular capabilities convert environmental intent into operational advantage. They also underscore that such operational gains are most likely to be realized in the market when firms pair efficiency improvements with visible quality signals and clear end-of-life instructions.Implications: The study shows that circular practices improve operations indirectly by improving resource-use efficiency, not through a direct operational effect (SCC → RUE → OE). Managers should therefore focus on strengthening resource-efficiency routines, translate those gains into market value through visible quality assurance and disciplined pricing, provide clear end-of-life guidance, and rely on supportive policies that incentivize waste reduction and better input management.
In recent years, environmental policies aimed at reducing the use of plastic bags have received considerable attention. However, few studies have investigated whether these policies can effectively reduce vinyl waste generation over time. This study investigated the relationship between the number of retail stores selling reusable waste bags (RWB), their sales volume, and the amount of vinyl waste produced, using time-series cross-sectional (TSCS) data from 25 local governments in Seoul, South Korea, from 2010 to 2023. Data were subjected to a panel-corrected standard error (PCSE) regression analysis. The findings of this study revealed that higher sales of RWBs resulted in increased vinyl waste generation, whereas the number of retail stores selling RWBs did not significantly impact vinyl waste generation. Overall, within the scope of this study, the implementation of RWBs did not fulfill the policy objective of reducing vinyl waste. Implications for future research and practice are also discussed. Implications: The integration of reusable waste bags (RWBs) within South Korea's volume-based waste fee (VWF) system provides valuable insights for global strategies aimed at reducing vinyl and single-use plastic bag waste. This longitudinal analysis (2010-2023) across 25 Seoul local governments reveals a counterintuitive result: higher RWB sales volumes were positively associated with increased vinyl waste generation. Contrary to theoretical expectations and policy intent, the RWB policy did not achieve net reduction in vinyl waste and appears to have functioned more as a mandatory retail purchase than as a driver of genuine waste minimization. These findings offer a cautionary case for jurisdictions pursuing similar approaches.
The present study investigates the potential of widely used supplementary cementitious materials (SCMs) such as fly ash (FA) and ground granulated blast furnace slag (GGBS) to improve the rheological and environmental performance of low-carbon cementitious pastes. Three binders consisting of 100% OPC, 25% FA, and 70% GGBS were tested at water-to-binder ratios of 0.4 and 0.45. The dynamic shear rheometer was employed to analyze shear-thickening behavior of various cementitious suspensions. Subsequently, the environmental life cycle assessment (LCA) was conducted within a "cradle-to-gate" framework, evaluating six environmental impact categories and proposing a novel approach to converting these impacts into a single environmental cost (USD). The results revealed that OPC suspensions exhibit the earliest and most pronounced shear-thickening onset, while 70% GGBS suspensions reduce global warming potential but increase acidification impact. In contrast, 25% FA suspensions minimize acidification impact. Moreover, the rheological behavior is significantly influenced by solid volume fraction (SVF) and particle morphology; 70% GGBS pastes demonstrate the highest yield stress (140 Pa) and plastic viscosity (1.61 Pa. s) at a w/b ratio of 0.4, attributed to their angular particle shape. The environmental cost of suspensions (100% OPC) is estimated at $13.92/m3, with OPC being the primary contributor. The findings highlight the potential of SCMs to enhance performance and reduce environmental impacts, supporting greater use of FA and GGBS for sustainable, low-carbon infrastructure development. Future research should focus on optimizing the combined use and dosage of FA and GGBS in low-carbon cementitious pastes to achieve a more effective balance among rheological performance, environmental sustainability, and economic viability. Equally important is the need to extend the assessment framework beyond the present scope by incorporating long-term performance and durability assessment, broader system boundaries, and more rigorous environmental cost evaluation should be incorporated to enable the development of robust and sustainable cementitious systems.Implications: India has set an ambitious goal of achieving carbon neutrality by 2070. In the coming years, a substantial increase in building construction is anticipated to accommodate the country's growing population. However, this expansion threatens to hinder progress toward national sustainable development goals (SDGs) and commitments to the Paris Climate Agreement. Indian thermal power plants and steel plants produce substantial amounts of fly ash and slag, which are solid waste byproducts. To mitigate the environmental impact and reduce cement consumption, it is essential to utilize these materials in construction. By incorporating fly ash and slag as cement replacement materials, we can significantly decrease the carbon footprint of the construction industry, contributing to both sustainability and resource efficiency. The paper uniquely integrates the rheological properties of cementitious suspensions with a comprehensive environmental assessment, offering a dual perspective on performance and sustainability. A novel methodology has been proposed to consolidate environmental impacts into a single environmental cost, expressed in US dollars, providing a practical decision-making tool.
The Clean Air Act Amendments of 1977 included protections for visibility in Class I areas, such as national parks and wilderness areas. Visibility degradation (haze) is determined from speciated aerosol mass concentrations measured by the Interagency Monitoring of Protected Visual Environments (IMPROVE) network. Mass concentrations are converted into reconstructed light extinction values using an algorithm that considers the mass extinction efficiencies (MSEs) and water uptake of different major aerosol species. This algorithm is evaluated against measured light scattering (bsp) using nephelometers that are co-located at several IMPROVE sites. Evaluating the performance of the algorithm is critical because of its use in tracking visibility trends for the U.S. Environmental Protection Agency's (EPA's) Regional Haze Rule (RHR). Previous evaluations (2001-2016) demonstrated that the current IMPROVE reconstructed light extinction equation (Second IMPROVE Equation) suggested in the RHR guidance results in spatial and temporal biases in visibility trends, leading to greater uncertainty in reaching national visibility goals. Extending the evaluation through 2024 suggests that using the current algorithm continues to introduce biases in visibility trends, primarily due to the parameterized dependence of MSEs on mass concentrations in the equation. We recommend a revised algorithm (Third IMPROVE Equation) that removes this MSE-mass dependence and updates aerosol composition assumptions to be consistent with the most recent science. The equation is more appropriate for representing long-term trends in regulatory visibility metrics across the IMPROVE network.Implications: IMPROVE data are central to the EPA's Regional Haze Rule (RHR) for tracking visibility trends in Class I areas. The current light-extinction equation (Second IMPROVE Equation) improved fits with early 2000s measurement data but introduced long-term biases. We present a revised equation, based on the First IMPROVE Equation, that improves consistency with measured light scattering and long-term trends. Implementing the revision would minimally affect RHR tracking metrics. This work provides timely input to ongoing EPA evaluations of RHR metrics and implementation guidance.
This study simultaneously measured in-cabin and ambient air quality in a passenger car under real-world driving conditions to evaluate the influence of different ventilation modes (recirculation, fresh air, and open windows) on the cabin concentrations of volatile organic compounds (VOCs) and particulate matter (PM). A single passenger car was tested in order to control for confounding factors related to vehicle design. Ventilation efficiencies were quantitatively assessed using air changes per hour (ACH), estimated using the carbon dioxide (CO2) mass balance method. Results showed that the recirculation mode effectively suppressed the infiltration of ambient fine particles (PM2.5), with I/O ratios ranging from 0.10 to 0.13. However, due to inadequate ventilation (ACH ≈3.2-3.5 h- 1), cabin CO2 concentration surpassed 4000 ppm. In contrast, the fresh air mode significantly increased ACH to 55-66 h-1, keeping CO2 concentrations below 1000 ppm. However, both fresh air and open-window modes led to a pronounced increase in cabin concentrations of PM and VOCs. Of the detected VOCs, acetone, ethanol, and formaldehyde had I/O ratios >1, suggesting in-cabin sources, whereas benzene, ethylbenzene, xylenes, and MTBE had I/O <1, indicating the presence of their dominant sources outside the vehicle cabin. These findings indicate a trade-off between reducing exposure to ambient pollutants and maintaining adequate ventilation, highlighting the need for optimized cabin ventilation strategies that balance ventilation, occupant comfort, and cabin air quality.Implications: When ventilation systems are inadequately designed or operated, vehicle cabins may become highly polluted microenvironments, exposing occupants to elevated levels of air pollutants due to the infiltration of roadside air contaminated by vehicle exhaust, emissions from in-cabin sources, and the confined nature of the cabin space. The observed trade-off between minimizing exposure to pollutants and ensuring sufficient ventilation highlights the need for optimized cabin ventilation strategies that balance air exchange, occupant comfort, and in-cabin air quality.
In recent decades, ethylene oxide (EtO) has been a widely used industrial sterilant and chemical intermediate that has faced increasing scrutiny related to its carcinogenic potential. This study evaluated residential and occupational exposure to EtO in a valley surrounding two point-source emissions in close proximity (~11 m apart). Air samples were collected in residential and industrial areas. Eight locations, ranging from 100 to 1,700 m from the center of the point-sources in varying directions, had average concentrations between 0.290 and 3.212 µg/m3 (0.16 to 1.8 ppb) with peak levels reaching 26.4 µg/m3 (15 ppb). Exposure scenarios were developed based on daily activity patterns, long-term residency, and estimates derived from historical emissions data. Under the most conservative assumptions, including 40 years of occupational exposure during the periods of highest recorded emissions around the facility, the maximum estimated cumulative lifetime exposure was 591 ppm-days. When compared with epidemiology studies of EtO-exposed workers from similar facilities (studies used by the Environmental Protection Agency (EPA) and International Agency for Research on Cancer (IARC) in their cancer risk assessments), the highest cumulative exposures observed (13,500+ ppm-days) were at least 23-fold higher than our maximum estimated lifetime exposure value (591 ppm-days). Importantly, these high-exposure groups showed no statistically significant cancer incidence, particularly for breast and lymphohematopoietic cancers. When compared to regulatory values and health-based benchmarks adjusted to cumulative exposures, estimated exposures were substantially below levels associated with increased cancer incidence in epidemiological cohorts for the community surrounding the sterilization facility, even to the most susceptible populations.Implications: This study presents a site-specific, data-driven framework for evaluating long-term human health risks from ethylene oxide (EtO) emissions using ambient monitoring, historical emissions, and conservative EPA-aligned assumptions. Even at one of the highest-emitting U.S. sterilization facilities, estimated exposures were well below levels associated with increased cancer risk. The findings challenge proximity-based risk assumptions and support more proportionate, risk-based air quality policies. The approach offers regulators a transparent, scientifically grounded method for EtO risk characterization under the Clean Air Act, TSCA, and state air toxics programs.
The overexploitation of natural resources and increasing dependence on these sources have caused an increase in solid waste generation, aggravating environmental impacts and contributing significantly to climate change through enhanced greenhouse gas (GHG) emissions. This scenario highlights the urgent need for circular economy strategies focused on reducing carbon emissions and mitigating environmental impacts. Continuous monitoring is crucial to evaluate current conditions and guide effective measures in the transition toward a sustainable waste management model. This study quantifies the total potential methane (CH4) emissions and analyzes the variation in CH4 production over time within a solid waste treatment and disposal facility. Emissions were estimated using three methodologies: the standard Intergovernmental Panel on Climate Change (IPCC) approach, the LandGEM® model (V3.02) provided by the U.S. Environmental Protection Agency (EPA), and the triangular gas production model. The results indicate peak emissions of approximately 72,82 and 2,30E-3 Gg for the IPCC and triangular models, respectively, while the LandGEM® model predicted a substantially higher peak of 8,31 Gg, suggesting emissions could persist for up to 124 years post-closure. In this study, the results are not directly comparable, as the estimates are strongly dependent on the assumptions and parameters adopted, reinforcing the inherent limitations of the available models when applied to realities different from those for which they were originally developed. Therefore, they should be interpreted as extreme envelopes of behavior intended to support the planning of strategies aimed at mitigating environmental impacts.Implications: The results presented in this study contribute significantly to the improvement of environmental management strategies in urban solid waste management complexes. The estimation of greenhouse gas (GHG) emissions allows the identification of critical points of methane and carbon dioxide release, supporting the adoption of more efficient control and mitigation technologies. In addition, the data obtained can be used by public managers and policymakers to develop action plans aimed at reducing emissions in the waste sector, aligning with the climate commitments assumed by Brazil under the Paris Agreement and promoting the transition to more sustainable circular economy practices.
Although incineration is a prevalent method for medical waste treatment in developing countries like Tanzania, the environmental safety of the resulting ash is often overlooked. This study aimed to present a detailed characterization of bottom ash from a medical waste incinerator at Kaloleni Hospital, Arusha, to assess its chemical composition, leaching potential, and environmental risk. Herein, source-segregated medical waste from three streams, including infectious waste (red bags), laboratory/pharmaceutical waste (yellow bags), and general waste (black bags), was analyzed. The findings revealed the distinct particle-size distributions, with the infectious waste (red bag) ash exhibited the highest fineness modulus (9.29) and the largest average particle size (2.35 mm), indicating greater potential for soil penetration and dust generation. Concentrations of heavy metals in the ash exceeded USEPA permissible limits for soil, including titanium (Ti) (3600-9884 mg/kg), iron (Fe) (3683-7789 mg/kg), zinc (Zn) (4020-7449 mg/kg), copper (Cu) (304-616 mg/kg), and mercury (Hg) (0.93-1.23 mg/kg). Notably, mercury predominated in infectious waste (red bag) ash, which was associated with thermometers. Leachate concentrations of critical metals such as lead (Pb) (1093 mg/L) and chromium (Cr) (601.1 mg/L) exceeded U.S. EPA regulatory limits by more than 200 and 120 times, respectively. Calcium sulfate (CaSO4), silicon dioxide (SiO2), and sodium chloride (NaCl) were the main crystalline phases. These findings demonstrate that the bottom ash poses a substantial risk of heavy metal leaching and environmental contamination. This underscores the urgent need for regulated disposal and pre-treatment of such ash at this hospital. This study recommends extending this investigation to other hospitals to fully assess and mitigate the regional risk to public and environmental health.Implications: This study demonstrates that bottom ash from a typical medical waste incinerator in a low-resource setting poses a severe environmental threat. High concentrations of heavy metals (Pb, Cr, Hg, Zn) exceed regulatory limits, with leaching tests confirming alarming mobility, particularly for Pb and Cr. Particle size analysis indicates risks of atmospheric dispersion of fine particles and soil infiltration of coarser fragments. The established link between color-coded waste segregation and ash hazards provides critical insights. These findings necessitate integrated strategies, including optimized incinerator operation, mandatory pre-treatment (e.g., stabilization) of bottom ash, and context-specific regulatory frameworks to mitigate risks to air quality, soil, groundwater, and public health.
Air pollution is widely recognized as a major public health concern, and emerging evidence suggests an association with dementia. Establishing a causal relationship, however, is difficult. Economic cycles affect both dementia prevalence and pollution levels: during economic booms, financial resources for treatment rise, but so do air pollution and work-related stress. In South Korea, air quality has generally improved, even as Alzheimer's cases have increased with population aging, indicating a time-series relationship that biases regression results. Air pollution and vascular dementia also temporarily declined during COVID-19, reflecting omitted variable bias. To address these endogeneity concerns, we use wind speed and direction as instruments for air pollution in South Korea. Our estimates show that higher concentrations of PM10, PM2.5, and NO2 significantly increase dementia cases, with instrumental variable results substantially larger than ordinary least squares, underscoring the importance of correcting for bias. These findings carry important policy implications. Because air pollution is a negative externality, its health consequences-including dementia-extend beyond individual responsibility and represent broader social costs. Reducing pollution could therefore not only improve health outcomes but also ease the considerable economic burden of dementia care. As air pollution disproportionately affects vulnerable groups-individuals with dementia who are unable to sustain employment or income-targeted social support is also essential to address their combined medical and financial challenges.Implications: We underscore the importance of addressing endogeneity issues when evaluating the relationship between air pollution and dementia. Conventional approaches may produce biased estimates due to spurious time-series-correlations and omitted variables. By using wind speed and direction as instruments, we identify LATE-based causal effects of air pollution on the number of dementia patients. Our findings suggest important policy implications: reducing air pollution can lower the substantial social and economic costs associated with dementia. Improved administrative data linking clinical records with environmental exposures would support effective monitoring and policy evaluation. Furthermore, international cooperation is needed to address transboundary nature of air pollution.
Citizen behavior change can serve as an important contributor to improving air quality, when the change is related to traffic emission considered as a major source of air pollution. This study aimed to examine the shift of traffic counts attributed by the Emergency Fine Dust Reduction Measures (EFDRM) in Seoul, South Korea, where one of the major components is text alert service to promote public engagement. Specifically, we investigated the changes in traffic counts before and during EFDRM as well as between different hours and days of the week, which could affect people's travel mode choices. We obtained hourly traffic counts, fine particle concentrations, and meteorological conditions in Seoul for 2016-2019. Using the difference-in-difference design and generalized additive model, we estimated the differences in traffic counts between the days with and without the EFDRM and between pre- and post-implementation periods after adjusting for fine particle air pollution, meteorology, and temporal trends. In addition, we compared these differences by rush and non-rush hours and by weekdays and weekends/holidays to examine the changes in travel behavior. The traffic counts on EFDRM days were significantly lower than on non-EFDRM days after the implementation, whereas no systematic reduction was observed before the implementation. This decrease was found on weekends/holidays and during weekday non-rush hours, but not during weekday rush hours, indicating the impact of the feasibility on behavioral changes in addition to perception. Our findings suggest that short-term air quality interventions can achieve the goal when accompanied with public communication targeting the alternative travel option.Implications: This study provides new evidence that short-term emergency actions can effectively reduce traffic through citizen behavioral changes. The findings highlight that the involvement of public communication and feasible alternative travel options to short-term actions can play an important role in the success of interventions. The reduction in traffic counts, particularly during non-rush hours and weekends, suggests that voluntary behavioral responses can contribute to improving air quality without imposing large regulatory costs. These results offer practical guidance for policymakers to design public engagement-based air quality measures.
Wildfire events have driven a seasonal decline in air quality in recent years. The EPA's National Ambient Air Quality Standards are set to provide public health and welfare protection, but when a standard exceedance is outside the control of an air agency, such as in the case of many wildfires, an exceptional event demonstration can be developed to exclude data from attainment calculations. To evaluate and document probable exceptional events, we created a nationwide screening methodology to identify enhancements of PM2.5 and ozone concentrations due to wildfire emissions. The screening methodology combines widely used wildfire data and tools, including NOAA's Hazard Mapping System data, PM2.5 and ozone monitor data, modeled smoke PM2.5 results, and generalized additive modeling results. This screening identified regional wildfire trends in the data, including the year-round influence of smoke in the southeastern part of the U.S. due to agricultural burning and the significant impact of the 2021 and 2023 Canadian wildfire seasons on the northeastern U.S. Case studies on high- and low-frequency wildfire-impacted areas confirmed the efficacy of the screening method. Results suggest that more than one-third of the days from the 2020-2022 and 2021-2023 design value periods were characterized by an ozone or PM2.5 smoke event somewhere in the country. Our results provide evidence of the scale to which wildfire smoke contributes to air pollution; this screening methodology can be used to identify probable wildfire exceptional smoke events.Implications: Wildfire events have driven a seasonal decline in air quality in recent years. The EPA's National Ambient Air Quality Standards are set to provide public health and welfare protection, but when a standard exceedance is outside the control of an air agency, such as in the case of many wildfires, an exceptional event demonstration can be developed to exclude data from attainment calculations. We created a nationwide screening methodology to identify enhancements of PM2.5 and ozone concentrations due to wildfire emissions. Our screening methodology can be used to identify probable wildfire exceptional smoke events.
Compared to high-grade reference monitors, low-cost sensors are small in size with minimal power consumption. This has partly led to their proliferation, especially within low- and middle-income countries-amidst accuracy and precision concerns. The dynamic nature of air pollution, coming from multiple sources and fluctuating over time and space, further complicates accuracy issues. This then makes air pollution of a given area unique based on context. To address this challenge, this paper lays out a stepwise approach that makes air quality measurement interpretation more accessible, thereby increasing community action in air quality awareness. Using an urban network of 11 low-cost PM2.5 sensors (LCS) and a Beta Attenuation Monitor (BAM) located across diverse land use types in Kampala, Uganda. Hourly and daily average PM2.5 concentrations from both LCS and a BAM were compared against each other over a 13-month period from January 2022 to January 2023. Monitoring sites were classified into emission zones based on surrounding emission sources, guided by the AIRQO land-use descriptors for sensor locations. Site classification of either low or high-emission reflected local emission intensity rather than residential status alone. Low-emission sites were primarily low-density, upscale residential areas characterized by greater green space, paved roads, and limited nearby traffic or commercial activity. High-emission locations had substantial nearby emission sources, including commercial centers, business hubs, proximity to highways or major roads, and high-density residential areas with mixed land use. Sensors followed a similar pattern with the BAM for both the hourly and 24-hr measurements at lower concentrations, but dispersed at the higher values. A stronger linear relationship from the 24 hr data across all sites exists. Slopes are lower in urban areas (~0.60-1.05) compared to peri-urban areas (~1.10-1.23). Findings suggest the need for a transparent framework that makes air quality data more accessible for community action.Implications: This work shows the promise of low-cost sensors in air quality measurements, especially within resource-constrained communities, where a stronger linear relationship from the 24 hr data across all sites exists when compared to the BAM. It also demonstrates the importance of considering the different land use in air quality measurement interpretation, which strengthens the need to make air quality readings more accessible and digestible to the general public. Clearly conveying air quality information can empower communities and decision-makers on pollution control innovation.
Traffic-related volatile organic compounds (VOCs) represent an important exposure pathway for urban commuters in megacities such as Bangkok, Thailand. This study quantified personal exposure to benzene, toluene, ethylbenzene, and xylene isomers (BTEX) and evaluated associated inhalation health risks across five major transportation modes: air-conditioned bus (A/C bus), non-air-conditioned bus (non-A/C bus), taxi, the Bangkok Mass Transit System (BTS), and the Metropolitan Rapid Transit (MRT). Personal air monitoring was conducted during wet and dry seasons to capture seasonal variability in exposure. BTEX concentrations differed significantly by transport mode and season. Non-A/C buses consistently exhibited the highest concentrations, followed by A/C buses and taxis, while the lowest levels were observed in rail-based systems (BTS and MRT). Across all modes and seasons, concentrations ranged from 6.1-41.4 µg/m3 for benzene, 19.1-128.6 µg/m3 for toluene, 1.9-23.7 µg/m3 for ethylbenzene, 10.3-50.3 µg/m3 for m,p-xylenes, and 2.3-8.8 µg/m3 for o-xylene, with consistently higher levels during the dry season. Non-carcinogenic risk assessment indicated hazard index values below unity for all transport modes, with the highest value observed in non-A/C buses during the dry season (HI = 7.94 × 10-2). In contrast, benzene-related incremental lifetime cancer risks frequently exceeded the U.S. EPA lower benchmark (1.0 × 10-6) but remained below the upper tolerable limit (1.0 × 10-4), with the highest risk estimated for non-A/C bus commuters (9.80 × 10-6). These results demonstrate that transportation mode and seasonality are key determinants of commuter BTEX exposure and highlight the need for targeted mitigation strategies focusing on ventilation design, emission control, and cleaner public transport systems.Implications: This study provides policy-relevant evidence for urban air quality management and exposure reduction in traffic-congested megacities. Significant variation in BTEX exposure across transport modes indicates that microenvironmental conditions, including ventilation, cabin enclosure, and proximity to traffic emissions, strongly influence commuter exposure. Road-based modes, particularly non-A/C buses, exhibited the highest exposures and risk estimates. Although risks remained within regulatory thresholds, benzene-related cancer risks highlight routine commuting as a meaningful long-term exposure pathway. Targeted controls such as improved vehicle ventilation and sealing, VOC filtration, stricter emission standards, reduced idling, and expansion of mass rapid transit can effectively reduce commuter exposures and support evidence-based transportation and air quality policies.
Wildland fire smoke can severely degrade downwind air quality and impact responding firefighters and the public. Accurate and timely monitoring of particulate matter (PM) and gaseous pollutants around wildland fires are needed to support management activities like protecting responders and the public from the health and safety hazards of wildland fire smoke. This study systematically evaluates the performance of commercially available, non-regulatory PM and gas instruments/sensors under controlled wildland fire smoke conditions. We assessed accuracy, precision, and linearity by comparing instrument/sensor outputs to reference-grade samplers/instruments across a wide range of smoke concentrations. Results indicate that most non-regulatory PM instruments/sensors, particularly those utilizing optical particle sensing technology, often exhibit a high positive raw PM2.5 measurement bias. However, applying smoke-specific calibration models substantially improved accuracy, with several models achieving post-calibration accuracy greater than 85%. Carbon monoxide (CO) and carbon dioxide (CO2) gas instruments/sensors generally performed well after calibration, while the performance of electrochemical nitrogen dioxide (NO2) and sulfur dioxide (SO2) sensors was relatively poor. Non-regulatory PM2.5 instrument/sensor response was primarily influenced by aerosol optical properties, particle size distribution, and effective density. We found that smoke-specific calibration and data quality assurance are key for reliable non-regulatory measurements during wildland fire events, especially for incident responder force protection and nearby communities. Integrating calibrated non-regulatory measurement data with regulatory networks can improve smoke exposure assessment and public health messaging. While non-regulatory instruments/sensors cannot fully replace reference instruments, their proper selection and calibration can provide valuable, actionable data for air quality management during wildfires.Implications: The results presented in this paper provide federal, state, local, and tribal air monitoring and public health agencies with performance information on numerous commercially available non-regulatory instruments/sensors to address air quality monitoring data collection and interpretation challenges presented by wildland fire smoke. The presented accuracy, precision, and linearity performance metrics provide knowledge for the selection of new air quality monitors and insight on the deployment/use of existing monitors during wildland fire events to improve management oversight for professional practitioners/responders, and for communication of health messaging to the public.
The management of absorbent hygiene products (AHPs) is a critical aspect that requires comprehensive attention by various stakeholders including local government authorities. While existing literature has systematically and comprehensively identified the challenges of AHP waste in residential areas, little attention has been given to understanding its associated management problems at the level of institutional and policy frameworks. This paper, using methods inspired by the tradition of qualitative research, explores challenges that hamper the sustainable management of AHP from the institutional and policy contexts, focusing on Polokwane Local Municipality. This study shows that the lack of financial resources, including deficiencies in institutional coordination, legislation and physical infrastructure, presents major challenges for the sustainable management of AHP in Polokwane Municipality and South Africa as a whole. These challenges have been analyzed within the broader framework of the sustainable development goals (SDGs), particularly Goals 3, 6, 12, 13, 14, and 15.Implications:The findings of the study underscore the need to categorize AHP waste as a waste stream and develop a targeted policy intended to influence sustainable AHP waste management. The development of action plans integrating SDGs could aid effective and sustainable practices. Prioritizing of waste management budget allocation in the South African parliament can contribute toward development of waste facilities. Intensive awareness programs and the addition of waste management curriculum in foundation educational programs could influence sustainable behaviours. Compliance monitoring coupled with penalties will address indifferent behaviours. Prioritizing environmental-pollution-related cases in court can set a precedent to mold sustainable practices.
Sewer covers present an interface for biogenic methane (CH4) gas produced in the wastewater collection and transportation system to escape to the atmosphere. However, the contribution of these emissions to municipal CH4 footprints is not well understood. In this study, direct methane emission measurements were made at 118 sewer covers in Calgary, Alberta, Canada to quantify and characterize the emissions from the city's wastewater collection network. Emission rates ranged from 0.00 to 0.241 g CH4 h-1. The annual cumulative wastewater collection emissions are estimated to be 3.92 t CH4 (3.38 to 4.47 t CH4, 95% confidence interval). This is 1.40% of all wastewater treatment-related emissions in Calgary, based on a gridded inventory and 0.005% of Calgary's total CH4 footprint, according to a city-scale satellite estimate. Sewer covers measured near locations in the wastewater network that are known to be more favorable environments for CH4 production (n = 27) were found more likely to emit CH4 and had statistically higher emission rates compared to the sewer covers that were not (n = 91). Overall, this study indicates that wastewater collection emissions are small for Calgary relative to other biogenic and thermogenic sources in the city; however, this result might not be indicative of the municipal emission patterns from other cities.Implications: This research is one of only a handful of urban case studies that has quantified CH4 emissions from sewer covers using a direct measurement method. The findings of this study indicate that sampling strategy and upscale modelling of sewer cover emissions depend on knowledge of city-specific wastewater infrastructure, which is useful for guiding future work in this limited field.
The greater New York City area has failed to attain the National Ambient Air Quality Standard for ozone for more than 30 yr. Ozone is produced in the atmosphere by photochemical reactions involving volatile organic compounds (VOCs) and nitrogen oxides (NOx). Analyses suggest that summertime ozone production in the urban core of the nonattainment area is often limited by VOCs or is in the transition regime between NOx and VOC limitation. VOC monitoring at hourly time resolution was conducted for more than 1 yr on Staten Island, NY, to gain insights into VOC emission sources upwind of the New York City area. These data were analyzed using a suite of source apportionment tools. A petroleum refinery was identified as a major propylene source, while a spatial zone with numerous hydrocarbon storage tank farms and terminal operations was identified as a major source for several additional VOCs previously deemed influential in ozone production in the New York City urban core. VOC source regions along Newark Bay were also identified. This work demonstrates the use of highly time-resolved VOC data and source apportionment tools to support air quality management.Implications: This study developed a refined understanding of volatile organic compounds (VOCs) emission sources through hourly VOC monitoring on Staten Island, NY, and demonstrated the value of highly time-resolved VOC data to support air quality management. The study's results collectively suggest that targeted VOC control strategies within and immediately upwind of the dense NOx emissions area within the New York City urban core can help reduce ozone in the New York City urban region as a complement to regional NOx control strategies addressing high ozone formed farther downwind of the city.
