Assessing the PM2.5 impact of biomass combustion in megacity Dhaka, Bangladesh

Removal of airborne particulate matter by evergreen tree species in Dhaka, Bangladesh

Urban air quality stands as a pressing concern in cities globally, with airborne particulate matter (PM) emerging as a significant threat to human health. An investigation was carried out to examine the potential of four prevalent evergreen roadside tree species grown at different locations in Dhaka to capture PM using their leaves. The distribution of PM by mass and quantity in Dhaka are presented for the first time for Bangladesh and these results will also be applicable to countries with similar climates and tree species. Separate gravimetric analyses were carried out to quantify PM in three different size ranges (0.2-2.5 μm, 2.5-10 μm, and 10-100 μm) accumulated on surfaces and trapped within waxes by using the rinse and weigh method. The method is validated for the first time through SEM-EDX analysis, which confirmed that the increase in weight from chloroform-rinsed leaves was exclusively attributable to particle deposition on the filter. The chemical composition of the deposited PM2.5 was analyzed quantitatively by determining the concentration of twenty-five trace elements employing ICP-MS. SEM-EDX analysis revealed the significance of leaf microstructural traits in effectively capturing PM. Significant variations in the deposition of PM were found among different species for two PM categories (surface PM and wax-embedded PM) and three size fractions (large, coarse, and fine) (one-way ANOVA; p < 0.05). The quantity of wax retained on the foliage of trees documented in these locations also varied (p < 0.05). Among the species studied, Ficus benghalensis demonstrated a greater ability to retain PM. Mangifera indica was identified to be the most efficient collector of wax-related PM and appears to be the ideal species for traffic-heavy areas distinguished by high concentrations of organic compounds from vehicle emissions.

Global burden of lung cancer in women of childbearing age attributable to ambient particulate matter pollution: 1990-2021

BACKGROUND

This study aimed to evaluate the global burden of lung cancer due to ambient particulate matter (PM) pollution in women of childbearing age from 1990 to 2021.

METHODS

This was a secondary analysis utilizing data from the Global Burden of Disease (GBD) 2021, with a focus on the temporal trends of the lung cancer burden attributable to ambient PM2.5 among women of childbearing age.

RESULTS

In 2021, the global mortality and disability-adjusted life years (DALYs) number of lung cancer burden attributable to ambient PM2.5 among women of childbearing age were approximately 5205 and 247,211, respectively. The rate of lung cancer attributable to ambient PM2.5 among women of childbearing age increased between 1990 and 2021, with the age-standardized mortality rate (ASMR) increasing from 0.22 (95% uncertainty interval [UI]; 0.13 to 0.33) to 0.25 (95% UI; 0.14 to 0.37; average annual percent change [AAPC] = 0.40) and the age-standardized DALYs rate (ASDR) increasing from 10.39 (95% UI; 5.96 to 15.72) to 12.06 (95% UI; 6.83 to 17.51; AAPC = 0.41). The middle sociodemographic index (SDI) region, East Asia, and China had the heaviest burden, while the high SDI region showed the highest decrease. ASMR and ASDR exhibited an inverted U-shaped relationship with the SDI.

CONCLUSIONS

From 1990 to 2021, the lung cancer burden attributable to ambient PM2.5 among women of childbearing age exhibited an increasing trend. Furthermore, increasing attention should be paid to the middle SDI region, East Asia, and China, as ambient PM pollution remains a critical target for intervention.

Influence of agricultural activity in corn farming on airborne microplastic in surrounding elementary school

Microplastics (MPs) have been widely detected in agricultural soils, and agricultural activities have been identified as an important factor influencing the abundance of MPs in the air. However, no studies have investigated whether agricultural activities are contributors to airborne MPs in buildings near farms. We collected airborne MP samples using an active sampling method from an elementary school near corn farms during different cultivation stages to assess the impact of agricultural activities on MPs in the study school near farms. Our data showed that the predominant shapes, sizes, colors, and polymer compositions were fragments, 2-50 μm, black or grey, and polyethylene terephthalate, respectively, during all cultivation stages. The highest and lowest MP concentrations were recorded during the land preparation (56.8 ± 7.4 particles/m3, August 2022) and growth (2.5 ± 1.8 particles/m3, February 2022) stages, respectively. A multiple-path particle dosimetry model revealed that the deposition fractions of MPs in humans were highest in the head; the highest and lowest deposition rates and fluxes of MPs in the airway were found during the land preparation and growth stages, respectively. The concentration of MPs did not present a positive correlation with potassium or crustal elemental concentration; however, it did show a positive association with temperature value. Therefore, our data did not show that corn cultivation influences MP concentrations in the study school near corn farms; instead, temperature was an important influencing factor.

A quantitative assessment of natural and anthropogenic effects on the occurrence of high air pollution loading in Dhaka and neighboring cities and health consequences

Although existing studies mainly focused on the air quality status in Bangladesh, quantifying the natural and manmade effects, the frequency of high pollution levels, and the associated health risks remained beyond detailed investigation. Air quality and meteorological data from the Department of Environment for 2012-2019 were analyzed, attempting to answer those questions. Cluster analysis of PM2.5, PM10, and gaseous pollutants implied that Dhaka and neighboring cities, Narayangonj and Gazipur, are from similar sources compared to the other major cities in the country. Apart from the transboundary sources, land use types and climate parameters unevenly affected local pollution loadings across city domains. The particulate concentrations persistently remained above the national standard for almost half the year, with the peaks during the dry months. Even though nitrogen oxides remained high in all three cities, other gaseous pollutants, such as CO and O3, except SO2, showed elevated concentrations solely in Dhaka city. Concentrations of gaseous pollutants in Dhaka vary spatially, but no statistical differences could be discerned between the working days and holidays. Frequency analysis results and hazard quotients revealed the likelihood of adverse health outcomes in Narayangonj ensuing from particulate exposures surpasses the other cities for different age, gender, and occupation groups. Nonetheless, school-aged children and construction workers were most at risk from chronic exposure to gaseous pollutants mostly in Dhaka. One limitation of this study was that the routine air quality monitoring happens just from five sites, making the evidence-based study concerning health outcomes quite challenging.

Evaluation of air quality and health risks associated with trace elements in respirable particulates (PM2.5) from Islamabad, Pakistan

Fine atmospheric particulates are associated with numerous environmental and health issues as they can penetrate deeply in the respiratory tract thereby adversely affecting the human health. This study aimed to investigate the concentrations of trace elements in the respirable (PM2.5) fraction of the atmospheric particulates and to understand their pollution status and health risks. The samples were collected from Islamabad, and the metals were extracted using HNO3 and HCl based extraction method. Atomic absorption spectroscopy was employed to quantify the concentrations of selected trace elements. PM2.5 exhibited considerable variations in their minimum (4.737 µg/m3) and maximum (108.1 µg/m3) levels. The significant contributors among the selected elements bound to PM2.5 were Ca (1016 ng/m3), K (759.8 ng/m3), Mg (483.0 ng/m3), Fe (469.7 ng/m3), and Zn (341.1 ng/m3), while Ag (0.578 ng/m3) was found at the lowest levels with an overall descending order: Ca > K > Mg > Fe > Zn > Cu > Pb > Ni > Cd > Mn > Sr > Cr > Co > Li > Ag. Multivariate PCA and CA identified industrial activities, combustion processes and automobile emissions as the main anthropogenic contributors to particulate pollution. Enrichment factors and geoaccumulation indices were computed to assess the pollution status. The results also revealed that among the trace elements, Cd showed extremely high contamination, followed by Ag, Zn, and Pb, which showed moderate to high contamination in the atmospheric particulates. Carcinogenic health risks from Pb and Ni were found to be within the safe limit (1.0 × 10-6); however, Cr, Co, and Cd exposure was linked to significant cancer risks. The present elemental levels in PM2.5 were also compared with the reported levels from other regions around the world.

A study on optical properties, classification, and transport of aerosols during the smog period over South Asia using remote sensing

Over the past few years, South Asian region has experienced frequent and thick smog events because of rapid population growth and enhanced anthropogenic activities, particularly in the Indo-Gangetic Plain (IGP). Therefore, the present study investigates aerosol properties such as aerosol optical depth (AOD) (500 nm), Angstrom exponent (AE) (440-870 nm), single scattering albedo (SSA), fine-mode fraction (FMF), absorption aerosol optical depth (AAOD), and absorption aerosol exponent (AAE) over selected AERONET sites namely Bhola (2012-2021), Dhaka (2012-2021), Jaipur (2011-2021), Kanpur (2011-2021), Karachi (2011-2021), Lahore (2011-2021), and Pokhara (2011-2021) in the IGP during the smog period (October, November, and December). Additionally, different aerosol types were categorized using AERONET direct sun (AOD, AE) and inversion products (VSD, SSA, RI, FMF, and ASY). The monthly mean AOD, AE, and FMF varied from ⁓0.33 to 1.07, ⁓0.3 to 1.4, and 0.6-0.9 µm over all selected AERONET sites during the smog period. Moreover, the outcomes revealed the dominance of biomass-burning and urban/ industrial aerosols over Lahore, Karachi, Dhaka, and Bhola during the smog period. Contrary to this, dust and mixed aerosols were abundant over Jaipur and Karachi, respectively. Furthermore, HYSPLIT cluster analysis is used to trace the transmission paths and potential sources of aerosols over selected sites.

Fine particulate matter and its chemical constituents' levels: A troubling environmental and human health situation in Karachi, Pakistan

Like many urban centers in developing countries, the effect of air pollution in Karachi is understudied. The goal of this study was to determine the chemical characterization, temporal and seasonal variability, sources, and health impacts of fine particulate matter (PM_2.5) in Karachi, Pakistan. Daily samples of PM_2.5 were collected using a low-volume air sampler at two different sites (Makro and Karachi University) over the four seasons between October 2009 and August 2010. Samples were analyzed for black carbon (BC), trace metals, and water-soluble ions. Results showed that the annual average concentrations of PM_2.5 at Makro and Karachi University were 114 ± 115 and 71.7 ± 56.4 μg m^-3, respectively, about 22.8 and 14.3-fold higher than the World Health Organization annual guideline of 5 μg m^-3. BC concentrations were 3.39 ± 1.97 and 2.70 ± 2.06 μg m^-3, respectively. The concentrations of PM_2.5, BC, trace metals, and ions at the two sites showed clear seasonal trends, with higher concentrations in winter and lower concentrations in summer. The trace metals and ionic species with the highest concentrations were Pb, S, Zn, Ca, Si, Cl, Fe, and SO₄^2-. The air quality index in the fall and winter at both sites was about 68 %, which is "unhealthy" for the general population. Positive Matrix Factorization revealed the overall contribution to PM_2.5 at the Makro site came from three major sources - industrial emissions (13.3 %), vehicular emissions (59.1 %), and oil combustion (23.3 %). The estimates of expected number of deaths due to short-term exposure to PM_2.5 were high in the fall and winter at both sites, with an annual mean estimate of 3592 expected number of deaths at the Makro site. Attention should be paid to the reduction of inorganic pollutants from industrial facilities, vehicular traffic, and fossil fuel combustion, due to their extremely high contribution to PM_2.5 mass and health risks.

Contributions of various driving factors to air pollution events: Interpretability analysis from Machine learning perspective

The air quality in China has been improved substantially, however fine particulate matter (PM_2.5) still remain at a high level in many areas. PM_2.5 pollution is a complex process that is attributed to gaseous precursors, chemical, and meteorological factors. Quantifying the contribution of each variable to air pollution can facilitate the formulation of effective policies to precisely eliminate air pollution. In this study, we first used decision plot to map out the decision process of the Random Forest (RF) model for a single hourly data set and constructed a framework for analyzing the causes of air pollution using multiple interpretable methods. Permutation importance was used to qualitatively analyze the effect of each variable on PM_2.5 concentrations. The sensitivity of secondary inorganic aerosols (SIA): SO₄^2-, NO₃^- and NH₄⁺ to PM_2.5 was verified by Partial dependence plot (PDP). Shapley Additive Explanation (Shapley) was used to quantify the contribution of drivers behind the ten air pollution events. The RF model can accurately predict PM_2.5 concentrations, with determination coefficient (R²) of 0.94, root mean square error (RMSE) and mean absolute error (MAE) of 9.4 μg/m³ and 5.7 μg/m³, respectively. This study revealed that the order of sensitivity of SIA to PM_2.5 was NH₄⁺＞NO₃^-＞SO₄^2-. Fossil fuel and biomass combustion may be contributing factors to air pollution events in Zibo in 2021 autumn-winter. NH₄⁺ contributed 19.9-65.4 μg/m³ among ten air pollution events (APs). K, NO₃^-, EC and OC were the other main drivers, contributing 8.7 ± 2.7 μg/m³, 6.8 ± 7.5 μg/m³, 3.6 ± 5.8 μg/m³ and 2.5 ± 2.0 μg/m³, respectively. Lower temperature and higher humidity were vital factors that promoted the formation of NO₃^-. Our study may provide a methodological framework for precise air pollution management.

Characterizing variations in ambient PM2.5 concentrations at the U.S. Embassy in Dhaka, Bangladesh using observations and the CMAQ modeling system

We analyze hourly PM2.5 (particles with an aerodynamic diameter of ≤ 2.5 μm) concentrations measured at the U.S. Embassy in Dhaka over the 2016 - 2021 time period and find that concentrations are seasonally dependent with the highest occurring in winter and the lowest in monsoon seasons. Mean winter PM2.5 concentrations reached ~165-175 μg/m3 while monsoon concentrations remained ~30-35 μg/m3. Annual mean PM2.5 concentration reached ~5-6 times greater than the Bangladesh annual PM2.5 standard of 15 μg/m3. The number of days exceeding the daily PM2.5 standard of 65 μg/m3 in a year approached nearly 50%. Daily-mean PM2.5 concentrations remained elevated (>65 μg/m3) for more than 80 consecutive days. Night-time concentrations were greater than daytime concentrations. The comparison of results obtained from the Community Multiscale Air Quality (CMAQ) model simulations over the Northern Hemisphere using 108-km horizontal grids with observed data suggests that the model can reproduce the seasonal variation of observed data but underpredicts observed PM2.5 in winter months with a normalized mean bias of 13-32%. In the model, organic aerosol is the largest component of PM2.5, of which secondary organic aerosol plays a dominant role. Transboundary pollution has a large impact on the PM2.5 concentration in Dhaka, with an annual mean contribution of ~40 μg/m3.

Striking impacts of biomass burning on PM2.5 concentrations in Northeast China through the emission inventory improvement

Biomass burning exerts substantial influences on air quality and climate, which in turn to further aggravate air quality. The biomass burning emissions in particular of the agricultural burning may suffer large uncertainties which limits the understanding of their impact on air quality. Based on an improved emission inventory of the Visible Infrared Imaging Radiometer Suite (VIIRS) relative to commonly used Global Fire Emissions Database (GFED), we thoroughly evaluate the impact of biomass burning on air quality and climate during the episodes of November 2017 in Northeast China which is rich in agriculture burning. The results first indicate substantial underestimates in simulated PM_2.5 concentrations without the inclusion of biomass burning emission inventory, based on a regional air quality model Weather Research and Forecasting model and Community Multiscale Air Quality model (WRF-CMAQ). The addition of biomass burning emissions from GFED then reduces the bias to a certain extent, which is further reduced by replacing the agricultural fires data in GFED with VIIRS. Numerical sensitivity experiments show that based on the improved emission inventory, the contribution of biomass burning emissions to PM_2.5 concentrations in Northeast China reaches 32%, contrasting to 15% based on GFED, during the episode from November 1 to 7, 2017. Aerosol direct radiative effects from biomass burning are finally elucidated, which not only reduce downward surface shortwave radiation and planetary boundary layer height, but also affect the vertical distribution of air temperature, wind speed and relative humidity, favorable to the accumulation of PM_2.5. During November 1-7, 2017, the mean daily PM_2.5 enhancement due to aerosol radiative effects from VIIRS_G is 16 μg m^-3, a few times higher than that of 2.8 μg m^-3 from GFED. The study stresses the critical role of biomass burning, particularly of small fires easily missed in the traditional low-resolution satellite products, on air quality.

Seasonal changes and respiratory deposition flux of PM2.5 and PM10 bound metals in Dhaka, Bangladesh

Due to rapid urbanization and fast economic development, aerosol pollution is a serious environmental issue, especially in Bangladesh. Based on bioaccessibility and respiratory deposition doses (RDD), health risks of PM_2.5 and PM₁₀ bound 15 (fifteen) metals were investigated at fourteen urban sites (roadside, marketplace, industrial, and commercial areas). Sampling campaigns were conducted over four seasons (winter, summer, rainy, and autumn) from December 2020 to November 2021. A beta attenuation mass analyzer measured particulate matter concentrations in ambient air. The metals in PM fractions were analyzed by X-ray fluorescence spectroscopy and inductively coupled plasma mass spectrometry (ICP-MS). The airborne trace metals (Cd, As, Zn, Pb, Cr, Cu, Ni) with high enrichment factors indicate anthropogenic sources. The positive matrix factorization (PMF) categorized these elements as originating from automobile exhaust, industrial emissions, and solid waste/coal combustion, whereas the geologic elements came from earth crust/soil dust. During the winter, most of the air mass trajectories arrived from India across the land (82%) and Indo Gangetic Plain (IGP) region to the sampling sites, which may have aided in the transport of pollutants. The deposition flux of metals illustrated that compared to PM_2.5, PM₁₀ deposited a higher amount of metals in the upper airways (81.96%). In comparison, PM_2.5 accumulates more elevated amounts of metals in alveolar regions (11.77%), due to the ability of fine particles to penetrate deeper into the lower pulmonary region. Among age groups, an adult inhales a higher amount of metals than a child, on average 0.103 mg and 0.08 mg of metals per day via PM_2.5, respectively. Acute health impacts are caused by the deposited cancer-causing metals in alveolar tissue, which circulates through the bloodstream and affects several organs. Prolonged exposure to these carcinogenic metals poses significant health risks.

Long-Term Exposure to Source-Specific Fine Particles and Mortality─A Pooled Analysis of 14 European Cohorts within the ELAPSE Project

We assessed mortality risks associated with source-specific fine particles (PM2.5) in a pooled European cohort of 323,782 participants. Cox proportional hazard models were applied to estimate mortality hazard ratios (HRs) for source-specific PM2.5 identified through a source apportionment analysis. Exposure to 2010 annual average concentrations of source-specific PM2.5 components was assessed at baseline residential addresses. The source apportionment resulted in the identification of five sources: traffic, residual oil combustion, soil, biomass and agriculture, and industry. In single-source analysis, all identified sources were significantly positively associated with increased natural mortality risks. In multisource analysis, associations with all sources attenuated but remained statistically significant with traffic, oil, and biomass and agriculture. The highest association per interquartile increase was observed for the traffic component (HR: 1.06; 95% CI: 1.04 and 1.08 per 2.86 μg/m3 increase) across five identified sources. On a 1 μg/m3 basis, the residual oil-related PM2.5 had the strongest association (HR: 1.13; 95% CI: 1.05 and 1.22), which was substantially higher than that for generic PM2.5 mass, suggesting that past estimates using the generic PM2.5 exposure response function have underestimated the potential clean air health benefits of reducing fossil-fuel combustion. Source-specific associations with cause-specific mortality were in general consistent with findings of natural mortality.

Interprovincial Joint Prevention and Control of Open Straw Burning in Northeast China: Implications for Atmospheric Environment Management

Large-scale open burning of straw residues causes seasonal and severe atmospheric pollution in Northeast China. Previous studies focused on the causes or assessment of atmospheric pollution in a single city. However, studies conducted on the interaction range, degree and policy control of pollutant transport on a large scale are still to be performed. In this study, we propose combined control of straw burning by dividing region the straw burning in Northeast China in recent 20 years, determining the transport routes between main cities, and analyzing the interaction characteristics of straw burning under different scenarios. The fire point data suggest that the most intense straw burning years in Northeast China in the past 20 years occurred in the range from 2014 to 2017, mainly after the autumn harvest (October–November) and before spring cultivation (March–April). The burning areas were concentrated in the belt of Shenyang-Changchun-Harbin, the border of the three provinces and Eastern-Inner Mongolia, and the surrounding area of Hegang and Jiamusi City. The lower number of fire points before 2013 indicates that high-intensity burning has not always been the case, while the sharp decline after 2018 is mainly due to scientific control of straw burning and increased comprehensive utilization of straw. Compared with S2, the PM2.5 concentrations increased by 6.2% in S3 and 18.7% in S4, indicating that burning in three or four provinces at the same time will significantly increase air pollution and exert a regional transmission effect. Straw burning in Northeast China is divided into six main regions based on correlation analysis and satellite fire monitoring. Under typical S3, the case analysis results indicate that there is regional transmission interaction between different cities and provinces, focusing on multi-province border cities, and it is affected by Northwest long airflow, and Southeast and Northeast short airflow. These results provide scientific and technological support for implementing the joint prevention and control plan for straw incineration in Northeast China.

Household use of crop residues and fuelwood for cooking and newborn birth size in rural Bangladesh

OBJECTIVES

We aimed to investigate the association between type of cooking biomass fuels (crop residues vs fuelwood) and newborn birth outcomes in Bangladeshi children.

METHODS

In this birth cohort study, pregnant women who were 18 years or older with ultrasound confirmed singleton pregnancy of ≤16 weeks of gestation were enrolled from two Bangladesh clinics between January 2008 and June 2011. Exposure to cooking biomass fuels during pregnancy was assessed by an administered questionnaire. The newborn size metrics were measured at the time of delivery. We used multiple linear regression and logistic regression to assess the associations between the type of cooking biomass fuels and birth outcomes after adjusting for covariates.

RESULTS

A total of 1137 participants were using biomass fuels, including crop residues (30.3%) and fuelwood (69.7%), respectively, for cooking. After adjusting for covariates, the use of crop residues for cooking was associated with a 0.13 SD decrease in birth length (95% CI 0.25 to -0.01), a 0.14 SD decrease in head circumference (95% CI -0.27 to -0.02), and increased risk of low birth weight (LBW, OR 1.52, 95% CI 1.07 to 2.15) compared with the use of fuelwood.

CONCLUSION

The use of crop residues for cooking was associated with reduced birth size and increased risk for LBW in Bangladeshi children, implying that the use of crop residues during pregnancy may have a detrimental effect on fetal growth.

Ambient ozone over mid-Brahmaputra Valley, India: effects of local emissions and atmospheric transport on the photostationary state

This study presents the characteristics of ground level atmospheric ozone (O₃) over the rural mid-Brahmaputra Valley region of the northeastern India. Ozone and oxides of nitrogen (NO_x = NO + NO₂) concentration data were obtained from continuous measurement of O₃ and NO_x housed at the MAPAN-AQM station at Tezpur University. The meteorological parameters were obtained from the same station. The diel, monthly, and seasonal variations of O₃ were studied. The O₃-NO_x photostationary state (PS) was carefully examined and it was found that the net O₃ concertation deviated substantially from the PS during the winter season. The deviation could be attributed to local biomass burning, biogenic VOC emission from forest and agriculture, and long-range transport of peroxyacyl nitrate (PAN). The long-range transport has been ascertained by examining the ventilation coefficients (VC), which correlated with the steep growth of net O₃ concentrations in the morning hours. The HYSPLIT air mass back trajectories were used in concentration-weighted trajectory (CWT) analyses of O₃ to assess the long-range regional transport of O₃ precursors, which positively influenced local O₃ concentrations.

Concentrations, transport characteristics, and health risks of PM2.5-bound trace elements over a national park in central India

Fine particulate matter (PM_2.5) mass and its chemical constituents were measured over Van Vihar National Park (VVNP) in Bhopal, central India. Fine PM collected over two years onto Teflon filters using a Mini-Vol® sampler were analyzed for trace elements using an Energy Dispersive X-ray fluorescence (ED-XRF) spectrometer. The temporal behaviour, dry deposition fluxes and transport pathways of elements, in addition to their health risks were examined in this study. S, K, Si, Al, Ca, and Fe accounted for most of the PM_2.5-bound trace elements (~88% on average). Pronounced seasonality was observed for major elements (S, K, and Cl) and reconstructed soil (estimated as the sum of oxides of crustal elements, i.e., Si, Al, Ca, Fe, and Ti), with winter and post-monsoon season highs, potentially due to source strengths and favourable metrology during these seasons. The synoptic meteorology during these seasons favoured the fetch of particles from highly polluted regions such as the Indo-Gangetic Plain. The estimated average dry depositional flux of each element in this study was comparable to those measured/estimated for each of these species over other urban areas. The sum of the dry deposition flux for crustal elements (1301.9 ± 880.7 μg m^-2 d^-1) was in agreement with global dust cycle models. Air-parcel trajectory cluster analysis revealed that S, K, and Cl were influenced by biomass and coal burning in predominantly in central, and northwestern India, while reconstructed soil was influenced by air masses from the Arabian and Thar deserts. Finally, human exposure risk assessment to carcinogens (As, Cr, Cd, Pb and Ni) and non-carcinogens (Cu, Zn, Mn, V, Hg, Se and Al) revealed that no significant risk was posed by these elements. The assessment in this study was a screening for severe adverse effects, rather than a speciated health assessment. Thus, over the study region, monitoring, health risk assessment and mitigation measures, where needed, must be enhanced to ensure that trace elements induced health effects continue to be within safe levels.

Respiratory Emergency Department Visits Associations with Exposures to PM2.5 Mass, Constituents, and Sources in Dhaka, Bangladesh Air Pollution

RATIONALE

To date, there is no published local epidemiological evidence documenting the respiratory health effects of source specific air pollution in South Asia, where PM2.5 composition is different from past studies. Differences include more biomass and residue crop-burning emissions, which may have differing health implications.

OBJECTIVES

We assessed PM2.5 associations with respiratory emergency department (ED) visits in a biomass-burning dominated high pollution region, and evaluated their variability by pollution source and composition.

METHODS

Time-series regression modeling was applied to daily ED visits from January 2014 through December 2017. Air pollutant effect sizes were estimated after addressing long-term trends and seasonality, day-of-week, holidays, relative humidity, ambient temperature, and the effect modification by season, age, and sex.

RESULTS

PM2.5 yielded a significant association with increased respiratory ED visits [0.84% (95% CI: 0.33%, 1.35%)] per 10 μg/m3 increase. The PM2.5 health effect size varied with season, the highest being during monsoon season, when fossil-fuel combustion sources dominated exposures. Results from a source-specific health effect analysis was also consistent with fossil-fuel PM2.5 having a larger effect size per 10 μg/m3 than PM2.5 from other sources [fossil-fuel PM2.5: 2.79% (0.33% to 5.31%), biomass-burning PM2.5: 1.27% (0% to 2.54%), and other-PM2.5: 0.95% (0.06% to 1.85%)]. Age-specific associations varied, with children and older adults being disproportionately affected by the air pollution, especially by the combustion-related particles.

CONCLUSIONS

This study provided novel and important evidence that respiratory health in Dhaka is significantly affected by particle air pollution, with a greater health impact by fossil-fuel combustion derived PM2.5.

Effect of COVID-19 pandemic-induced lockdown (general holiday) on air quality of Dhaka City

A worldwide pandemic of COVID-19 has forced the Government of Bangladesh to implement a lockdown during April-May 2020 by restricting people's movement; shutdown of industries and motor vehicles; and closing markets, public places, and schools to contain the virus. This type of strict measures caused an outcome, the reduction of urban air pollution, around the world. The present study aims to investigate the reduction of the concentration of pollutants in the air of Dhaka City and the reduction of the Air Quality Index (AQI). Necessary time-series data of the concentration of PM_2.5, NO₂, SO₂, and CO have been collected from the archive of the Air Quality Monitoring Station of the US Embassy in Dhaka and Sentinel-5P. The time-series data have been analyzed by descriptive statistics, and AQI was calculated following an appropriate formula suggested by the Environmental Protection Agency (EPA) based on the criteria pollutants. The study found that the concentrations of PM_2.5, NO₂, SO₂, and CO during April-May 2020 have been reduced by 26, 30, 07, and 07%, respectively, compared with the preceding year's concentrations. Moreover, the AQI has also been reduced by about 35% on average during the lockdown period than the same times of the previous year. However, the magnitude of pollution reduction in Dhaka is lower than in other cities and countries globally, including Delhi, Sao Paulo, Wuhan, Spain, Italy, the USA. The main reasons may include, among others, the poor implementation of lockdown (especially in the first week of April and the second fortnight of May), pre-existing pollution, transboundary pollution, incineration of solid waste, etc. This study will help policymakers figure out how to regulate pollution sources and improve the air quality of Dhaka.

Cardiovascular morbidity and mortality associations with biomass- and fossil-fuel-combustion fine-particulate-matter exposures in Dhaka, Bangladesh

BACKGROUND

Fine-particulate-matter (i.e. with an aerodynamic diameter of ≤2.5 µm, PM2.5) air pollution is commonly treated as if it had 'equivalent toxicity', irrespective of the source and composition. We investigate the respective roles of fossil-fuel- and biomass-combustion particles in the PM2.5 relationship with cardiovascular morbidity and mortality using tracers of sources in Dhaka, Bangladesh. Results provide insight into the often observed levelling of the PM2.5 exposure-response curve at high-pollution levels.

METHODS

A time-series regression model, adjusted for potentially confounding influences, was applied to 340 758 cardiovascular disease (CVD) emergency-department visits (EDVs) during January 2014 to December 2017, 253 407 hospital admissions during September 2013 to December 2017 and 16 858 CVD deaths during January 2014 to October 2017.

RESULTS

Significant associations were confirmed between PM2.5-mass exposures and increased risk of cardiovascular EDV [0.27%, (0.07% to 0.47%)] at lag-0, hospitalizations [0.32% (0.08% to 0.55%)] at lag-0 and deaths [0.87%, (0.27% to 1.47%)] at lag-1 per 10-μg/m3 increase in PM2.5. However, the relationship of PM2.5 with morbidity and mortality effect slopes was less steep and non-significant at higher PM2.5 concentrations (during crop-burning-dominated exposures) and varied with PM2.5 source. Fossil-fuel-combustion PM2.5 had roughly a four times greater effect on CVD mortality and double the effect on CVD hospital admissions on a per-µg/m3 basis than did biomass-combustion PM2.5.

CONCLUSION

Biomass burning was responsible for most PM2.5 air pollution in Dhaka, but fossil-fuel-combustion PM2.5 dominated the CVD adverse health impacts. Such by-source variations in the health impacts of PM2.5 should be considered in conducting ambient particulate-matter risk assessments, as well as in prioritizing air-pollution-mitigation measures and clinical advice.

Geospatial analysis of COVID-19 lockdown effects on air quality in the South and Southeast Asian region

The COVID-19 pandemic, induced by the novel Coronavirus worldwide outbreak, is causing countries to introduce different types of lockdown measures to curb the contagion. The implementation of strict lockdown policies has had unprecedented impacts on air quality globally. This study is an attempt to assess the effects of COVID-19 induced lockdown measures on air quality in both regional, country, and city scales in the South and Southeast Asian region using open-source satellite-based data and software frameworks. We performed a systematic review of the national lockdown measures of 19 countries of the study area based on publicly available materials. We considered two temporal settings over a period of 66 days to assess and compare the effects of lockdown measures on air quality levels between standard business as usual and current situation COVID-19 lockdown. Results showed that compared to the same period of 2019, atmospheric NO2, SO2, PM2.5, and CO levels decreased by an average of 24.16%, 19.51%, 20.25%, and 6.88%, respectively during the lockdown, while O3 increased by a maximum of 4.52%. Among the 19 studied cities, Dhaka, Kathmandu, Jakarta, and Hanoi experienced the highest reduction of NO2 (40%-47%) during the lockdown period compared to the corresponding period of 2019. The methodological framework applied in this study can be used and extended to future research in the similar domain such as understanding long-term effects of COVID-19 mitigation measures on the atmospheric pollution at continental-scale or assessing the effects of the domestic emissions during the stay-at-home; a standard and effective COVID-19 lockdown measure applied in most of the countries.

Temporal variation characteristics and source apportionment of metal elements in PM2.5 in urban Beijing during 2018-2019

To explore high-resolution temporal variation characteristics of atmospheric metal elements concentration and more accurate pollution sources apportionment, online monitoring of metal elements in PM_2.5 with 1-h time resolution was conducted in Beijing from August 22, 2018 to August 21, 2019. Concentration of 18 elements varied between detection limit (ranging from 0.1 to 100 ng/m³) and nearly 25 μg/m³. Si, Fe, Ca, K and Al represented major elements and accounted for 93.47% of total concentration during the study period. Compared with previous studies, airborne metal pollution in Beijing has improved significantly which thanks to strict comprehensive control measures under the Clean Air Action Plan since 2013. Almost all elements present higher concentrations on weekdays than weekends, while concentrations of elements associated with dust sources during holidays are higher than those in working days after the morning peak, and there is almost no concentration difference in the evening peak period. Soil and dust, vehicle non-exhaust emissions, biomass, industrial processes and fuel combustion were apportioned as main sources of atmospheric metal pollution, accounting for 63.6%, 18.4%, 16.8%, 1.0% and 0.18%, respectively. Furthermore, main occurrence season of metal pollution is judged by characteristic radar chart of varied metal elements proposed for the first time in this study, for example, fuel combustion type pollution mainly occurs in winter and spring. Results of 72-h backward trajectory analysis of air masses showed that, except for local emissions, atmospheric metal pollution in Beijing is also affected by regional transport from Inner Mongolia, Hebei, the Bohai Sea and Heilongjiang.