Mitigation pathways towards national ambient air quality standards in India

Tracking air pollution and CO2 emissions in 13,189 urban areas worldwide using large geospatial datasets

Air pollution and climate change are urgent global concerns, with urban areas contributing heavily to both air pollutants and greenhouse gas emissions. Here we calculate fine particulate matter, nitrogen dioxide, and ozone concentrations and fossil-fuel carbon dioxide emissions per capita in 13,189 urban areas worldwide from 2005 to 2019 and analyze correlations between trends for these pollutants, leveraging recently-developed global datasets. Globally, we found significant increases in ozone (+6%) and small, non-significant changes in fine particulate matter (+0%), nitrogen dioxide (-1%), and fossil-fuel carbon dioxide emissions (+4%). Also, over 50% of urban areas showed positive correlations for all pollutant pairs, though results varied by global region. High-income countries with strong mitigation policies experienced decreases in all pollutants, while regions with rapid economic growth had overall increases. This study shows the impacts of urban environmental initiatives in different regions and provides insights for reducing air pollution and carbon dioxide emissions simultaneously.

Pathways for India to Reduce Ambient Air Pollution Health Burden and Achieve the Sustainable Development Goal (SDG-3.4)

Sustainable Development Goal 3.4 (SDG-3.4) aims to reduce non-communicable disease (NCD) mortality by one-third by 2030, compared to 2015 levels. First, we examined whether the National Clean Air Program (NCAP) is sufficient to allow India to achieve this target. Subsequently, we integrated GAINS-simulated sector-specific PM2.5 concentrations across three pathways─business-as-usual (BAU), advanced control technology (ACT), and sustainable development scenario (SDS)─with the Global Burden of Disease framework to assess potential health benefits for 2030 at a subnational scale and evaluate the feasibility of accomplishing SDG-3.4. In 2015, ambient PM2.5 attributable premature deaths were 0.72 million (95& UIs: 0.53-0.89), and an aggregated 0.12 million (0.08-0.16) deaths could be prevented if the NCAP target is met by 2026. However, states could reduce 3.6-10.8% of targeted NCD mortality by 2030 with a lagged 40% reduction in PM2.5 levels relative to the baseline. PM2.5-attributable deaths would change to 0.79 million (0.57-1.1), 0.76 million (0.6-1.1), and 0.63 million (0.48-0.81) in 2030 under the BAU, ACT, and SDS pathways, respectively. Implementing stringent emission controls through policy and technological interventions, primarily focusing on household and energy sectors, would reduce NCD mortality by 5-13% across subregions. Simultaneously controlling other risk factors would accelerate India's journey toward achieving SDG-3.4.

Synergies of air pollution control policies: A review

Air pollution control necessitates the implementation of multiple policy instruments in a coordinated manner. However, the enforcement of different policy combinations may generate complementary or offsetting synergistic effects, thereby influencing policy effectiveness. Nevertheless, the direction of synergy and the mechanisms of action among heterogeneous policies is undefined in existing academic research. This study systematically reviewed 773 articles from 1998 to 2023 and, for the first time, integrated four primary domains of air pollution control policies: policy synergy and integration, collaborative governance for pollution and carbon mitigation, joint control of multiple pollutants, and cross-regional cooperative governance. This study revealed the directions and mechanisms of air policy synergy and provided empirical evidence for cross-regional comparisons in global environmental governance, with the ultimate goal of enhancing the effectiveness of air pollution control policies. Specifically, the mechanisms underlying policy synergy suggest that the cumulative impact of policies leads to the synergistic effects of multiple policies being superior to the effects of implementing a single policy. Furthermore, due to market price signals or the characteristics of specific technologies, the concurrent application of multiple policies may occasionally yield negative synergistic outcomes. Despite these advancements, gaps remain particularly in broadening the scope of policy integration, refining the assessment of synergistic effects, developing control strategies, and enhancing stakeholder engagement. Further research is necessary to address these gaps and enhance air policy effectiveness.

Identifying Key Sources for Air Pollution and CO2 Emission Co-control in China

China is confronting the dual challenges of air pollution and climate change, mandating the co-control of air pollutants and CO2 emissions from their shared sources. Here we identify key sources for co-control that prioritize the mitigation of PM2.5-related health burdens, given the homogeneous impacts of CO2 emissions from various sources. By applying an integrated analysis framework that consists of a detailed emission inventory, a chemical transport model, a multisource fused dataset, and epidemiological concentration-response functions, we systematically evaluate the contribution of emissions from 390 sources (30 provinces and 13 socioeconomic sectors) to PM2.5-related health impacts and CO2 emissions, as well as the marginal health benefits of CO2 abatement across China. The estimated source-specific contributions exhibit substantial disparities, with the marginal benefits varying by 3 orders of magnitude. The rural residential, transportation, metal, and power and heating sectors emerge as pivotal sources for co-control, with regard to their relatively large marginal benefits or the sectoral total benefits. In addition, populous and heavily industrialized provinces such as Shandong and Henan are identified as the key regions for co-control. Our study highlights the significance of incorporating health benefits into formulating air pollution and carbon co-control strategies for improving the overall social welfare.

Black carbon emissions inventory and scenario analysis for Pakistan

Black carbon (BC) emissions, resulting from the incomplete combustion of carbonaceous fuels, have been extensively linked to adverse impacts on air quality, climate change, and public health. Nevertheless, there is currently a lack of a comprehensive analysis that integrates activity-based BC emissions inventory and scenario analysis at the national/regional, sectoral, and sub-sectoral levels in Pakistan. This study aims to fill this gap by conducting a comprehensive evaluation of Pakistan's BC emissions inventory for 2021 along projecting emissions until 2050 under the reference emission scenario (RES) and the accelerated reduction scenario (ARS) using the GAINS modeling framework to assess the potential impact of mitigation measures. This study takes a unique approach by considering commonly overlooked sources of BC emissions, such as kerosene lighting, brick kilns, diesel generator sets, and natural gas flaring, which are not typically included in conventional analyses. National BC emissions in 2021 were estimated at 181 kt, with residential combustion being the major contributor, accounting for more than half (108 kt) of the total emissions. The transport, industry, waste, agriculture, power plants, and fuel conversion sectors contributed 26.1 kt, 20.1 kt, 10.7 kt, 8.9 kt, 6.0 kt, and 0.9 kt, respectively. We anticipate that the total BC emissions in Pakistan will reach 201 kt under the RES and 41 kt under the ARS scenario by the year 2050. The ARS achieves substantial BC reductions by the adoption of cleaner fuels, improved biomass stoves, end-of-pipe emission control technologies with higher removal efficiencies, and implementing a ban on the open burning of waste and crop residues. This study underscores the considerable potential for reducing BC emissions across various sectors in Pakistan over the next three decades.

Impact of Glasgow Climate Pact and Updated Nationally Determined Contribution on Mercury Mitigation Abiding by the Minamata Convention in India

India is one of the largest emitters of atmospheric anthropogenic mercury (Hg) and the third-largest emitter of greenhouse gases in the world. In the past decade, India has been committed to the Minamata Convention (2017) in addition to the Paris Climate Change Agreement (2015) and the Glasgow Pact (2021). More than 70% to 80% of India's mercury and carbon dioxide emissions occur because of anthropogenic activities from coal usage. This study explores nine policy scenarios, the nationally determined contribution (NDC) scenario, and two deep decarbonization pathways (DDP) with and without mercury control technologies in the energy and carbon-intensive sectors using a bottom-up, techno-economic model, AIM/Enduse India. It is estimated that NDC scenarios reduce mercury emissions by 4%-10% by 2070; while coal intensive (DDP-CCS) pathways and focus on renewables (DDP-R) reduce emissions by 10%-54% and 15%-59%, respectively. Increase in the renewables share (power sector) can result in a significant reduction in the costs of additional pollution-abating technologies in the DDP-R scenario when compared with the coal intensive DDP-CCS scenario. However, the industry sector, especially iron and steel and metal production, will require stringent policies to encourage installation of pollution-abating technologies to mitigate mercury emissions under all the scenarios.

Landscape assessment of the cities in the state of Maharashtra: first step towards air quality management (AQM) and strategic implementation of mitigation plans

OBJECTIVE OF THE STUDY

This study aims to understand the need for landscape assessment of the 18 non-attainment cities in the state of Maharashtra, to understand and rank the cities according to the need and necessity for strategic implementation of air quality management. This air quality management is a National Clean Air Programme initiative to curb the air pollution level in all the highly polluted Indian cities by 20-30% till 2024.

METHODOLOGY

The ranking and selection of the cities consisted of a two-phase approach including (a) desk research and (b) field interventions and stakeholders' consultations. The first phase included (a_i) review of 18 non-attainment cities in Maharashtra, (a_ii) identification of suitable indicators to inform prioritisation during the ranking process, (a_iii) data collection and analysis of the indicators and (a_iv) the ranking of the 18 non-attainment cities in Maharashtra. The second phase, i.e. field interventions included (b_i) Mapping of stakeholders and field visits, (b_ii) the consultations with the stakeholders, (b_iii) information and data collection and (b_iv) ranking and selection of cities. On analysing the score obtained from both the approaches a ranking of all the cities is done accordingly.

RESULTS AND DISCUSSION

The screening of cities from the first phase gave a possible list of 8 cities-Aurangabad, Kolhapur, Mumbai, Nagpur, Nashik, Navi Mumbai, Pune, Solapur. Further, the second round of analysis involving field interventions and stakeholder consultations was done within the 8 cities to find out the most suitable list of two to 5 cities. The second research analysis gave Aurangabad, Kolhapur, Mumbai, Navi Mumbai and Pune. A more granular stakeholder consultation resulted in the selection of cities like Navi Mumbai and Pune as the cities where implementation of new strategies seemed feasible.

INTERVENTION AND ACTIVITIES

New strategic interventions like (a) strengthen the clean air ecosystem/institutions, (b) air quality monitoring and health impact assessment, and (c) skill development to ensure the long-term sustainability of initiatives planned for the cities.

Investigating the Impression of National Clean Air Programme in Enhancement of Air Quality Characteristics for Non-attainment Cities of Uttarakhand

Developmental activities have become sweet poison nowadays. Such activities degrade local air quality status, which can severely impact human health and their surrounding environment. The present study examines Uttarakhand’s air quality characteristics in non-attainment cities (Dehradun, Rishikesh, and Kashipur) to understand its cleansing processes. Under National Air Quality Monitoring Programme (NAMP), concentration of air pollutants (such as PM, SOx and NOx) was regularly monitored between 2015 and 2019 to evaluate the air quality status in the state. The NAMP highlights the higher concentration of PM10 in Dehradun, Rishikesh, and Kashipur, and hence it is imperative to reduce the concentration of PM10 under the permissible limit. State has 30.2% urbanisation rate, and annual urban growth rate of 4.0% much higher than the rural growth rate (1.2%) of the state, which results in 3 times higher amount of PM10 to the permissible limit. Moreover, 1.5–2-time higher amount of PM10 were recorded in Rishikesh, and Kashipur. In making sustainable future, various sector-specific strategies and sustainable approaches under National Clean Air Programme (NCAP) were launched to combat this critical situation. While comparing with the present air quality status, Dehradun experienced 12% reduction in PM10; whereas for Rishikesh and Kashipur, only 4.1% and 0.866% reduction were observed. The effective implementation of sector-specific action points will be the key factor in improvement of air quality of the Uttarakhand state.

Can the Indian national ambient air quality standard protect against the hazardous constituents of PM2.5?

Globally, exposure to ambient fine particulate matter (PM_2.5) pollution claims ∼9 million lives, yearly, and a quarter of this deaths occurs in India. Regulation of PM_2.5 pollution in India is based on compliance with its National Ambient Air Quality Standard (NAAQS) of 40 μg/m³, which is eight times the revised global air quality guideline (AQG) of 5 μg/m³. But, whether the NAAQS provides adequate protection against the hazardous components in PM_2.5 is still not clear. Here, we examined the risk to health associated with exposure to PM_2.5-bound polychlorinated biphenyls (PCB), heavy metals and polycyclic aromatic hydrocarbons (PAHs) in an Indian district averaging below the NAAQS. The annual average concentrations of PM_2.5 mass, Σ₂₈PCB and Σ₁₃PAHs were 34 ± 17 μg/m³, 21 ± 12 ng/m³ and 458 ± 246 ng/m³, respectively. Concentrations of As, Cr, Mn and Ni in PM_2.5 surpassed the screening levels for residential air. Substantial level of risks to health were associated with exposure to dioxin-like PCBs (Σ₁₂dlPCB), PAHs, As, Cr and Ni. The hazard index or lifetime cancer risk were 240, or 9 cases per 1000 population, respectively. The estimated risks to health through exposure to hazardous components, except Ni, were greatest in rural areas, having a lower average PM_2.5 concentration, than urban or peri-urban areas, suggesting higher toxicity potential of rural combustion sources. The large disparity between the estimated risk values and the acceptable risk level suggests that it would take a more stringent standard, such as the global AQG, to protect vulnerable populations in India from hazardous components in PM_2.5.

Exposure to Long-Term Air Pollution and Incidence of Peripheral Arterial Disease in the General Population: A Korean National Population-Based Retrospective Cohort Study

This study aimed to evaluate the causal relationship between long-term outdoor air pollutants and incidence of peripheral arterial disease (PAD) using the Korean National Health Insurance Service-National Sample Cohort (NHIS-NSC) database. We included 292,091 subjects from the general population who had previously not been diagnosed with PAD by the NHIS-NSC between 2008 and 2014. Hourly air pollutant data (particulate and gaseous) and climate data were collected. Correlation analysis of the collected data confirmed the relationship between air pollution and PAD incidence. For 1,836,965.4 person-years, incident cases of PAD were observed in 5243 subjects (285.4/100,000 person-years). In the Cox proportional hazard analysis, exposure to long-term average concentration of sulfur dioxide (SO2) [hazard ratio (HR), 1.686; (95% confidence interval (CI), 1.108–2.565) for .01ppm] and nitrogen dioxide (NO2) [HR, 1.200; (95% CI, 1.077–1.336) for .01 ppm] significantly increased the risk of PAD occurrence after the adjustment for several variables. This study demonstrated that SO2 and NO2 exposure are independent predictors of PAD.

Unprecedented reduction in air pollution and corresponding short-term premature mortality associated with COVID-19 lockdown in Delhi, India

Countries around the world introduced strict restrictions on movement and activities known as 'lockdowns' to restrict the spread of the novel coronavirus disease (COVID-19) from the end of 2019. A sudden improvement in air quality was observed globally as a result of these lockdowns. To provide insight into the changes in air pollution levels in response to the COVID-19 restrictions we have compared surface air quality data in Delhi during four phases of lockdown and the first phase of the restriction easing period (25 March to 30 June 2020) with data from a baseline period (2018-2019). Simultaneously, short-term exposure of PM_2.5 and O₃ attributed premature mortality were calculated to understand the health benefit of the change in air quality. Ground-level observations in Delhi showed that concentrations of PM₁₀, PM_2.5 and NO₂ dropped substantially in 2020 during the overall study period compared with the same period in previous years, with average reductions of ~49%, ~39%, and ~39%, respectively. An overall lower reduction in O₃ of ~19% was observed for Delhi. A slight increase in O₃ was found in Delhi's industrial and traffic regions. The highest peak of the diurnal variation decreased substantially for all the pollutants at every phase. The decrease in PM_2.5 and O₃ concentrations in 2020, prevented 904 total premature deaths, a 60% improvement when compared to the figures for 2018-2019. The restrictions on human activities during the lockdown have reduced anthropogenic emissions and subsequently improved air quality and human health in one of the most polluted cities in the world.Implications: I am submitting herewith the manuscript entitled "Unprecedented Reduction in Air Pollution and Corresponding Short-term Premature Mortality Associated with COVID-19 Forced Confinement in Delhi, India" for potential publishing in your journal.The novelty of this research lies in: (1) we utilized ground-level air quality data in Delhi during four phases of lockdown and the first phase of unlocking period (25^th March to 30^th June) for 2020 as well as data from the baseline period (2018-2019) to provide an early insight into the changes in air pollution levels in response to the COVID-19 pandemic, (2) Chatarize the change of diurnal variation of the pollutants and (3) we assess the health risk due to PM_2.5 and O₃. Results from ground-level observations in Delhi showed that concentrations of PM₁₀, PM_2.5 and NO₂ substantially dropped in 2020 during the overall study period compared to the similar period in previous years, with an average reduction of ~49%, ~39%, and ~39%, respectively. In the case of O₃, the overall reduction was observed as ~19% in Delhi, while a slight increase was found in industrial and traffic regions. And consequently, the highest peak of the diurnal variation decreased substantially for all the pollutants. The health impact assessment of the changes in air quality indicated that 904 short-term premature deaths (~60%) were prevented due to the decline in PM_2.5 and O₃ concentrations in the study period. The restrictions on human activities during the lockdown have reduced the anthropogenic emissions and subsequently improved air quality and human health in one of the most polluted cities in the world.

Development of Methodology and Assessment of Ecological Safety of the EAEU and CIS Regions in the Context of Sustainable Development

The trends of sustainable development and green agenda transform the production processes, leading industries, and regional markets, and reveal objective contradictions in ensuring the ecological safety of certain territories. This study aims to develop a methodology and assess ecological safety at aggregated system levels, taking into account natural and socioeconomic factors as well as the factor of human capital development with specification of the place of ecological safety in the concept of sustainable development. The objects of empirical research are the EAEU and CIS countries for the period 2010–2019, as well as 85 Russian regions. The scientific research toolkit is based on the methods of structural-logical, economical-statistical, and comparative analyses, and expert judgments. The concepts of sustainable development and human capital and the theory of the national school of ecological safety are analyzed using the systematic approach. The mixed methodological approach showed the interconnection of four approaches of assessing ecological safety (technogenic, environmental, institutional, resource-based). The authors developed a method for assessing ecological safety taking into account the contribution of human capital. The assessment results are typologized and grouped according to the dynamic trend. For the majority of the considered countries, changes in the level of ecological safety correlate with changes in socioeconomic indicators. The same trend is observed when considering the Russian regional formations. The contribution of human capital was recorded to a lesser extent. For several regions, the increased number of objects polluting the environment is accompanied by a decreased volume of polluting emissions into the atmosphere.

Impact of lockdown associated with COVID19 on air quality and emissions from transportation sector: case study in selected Indian metropolitan cities

This study examines the impact of air quality in selected Indian metropolitan cities during the COVID19 pandemic lockdown period. Concentrations of air quality parameters such as PM_2.5, NO₂, SO₂, and CO during the transition to lockdown and the actual lockdown period were compared with business as usual periods (a period prior to COVID19 lockdown and a corresponding period in 2019) to estimate the reduction in emission in four major IT hubs in India namely Bengaluru, Chennai, Hyderabad and Pune. A 40-45% reduction in PM_2.5 concentration was observed, in these cities, during the lockdown compared to the corresponding period in 2019 and a 20-45% reduction was observed compared to business as usual period in 2020. A vehicle kilometer traveled (VKT)-related questionnaire survey-based study in Hyderabad revealed that, with 48% of population utilizing work-from-home during the transition to lockdown period, vehicular PM_2.5 emission in Hyderabad reduced by 54% compared to usual traffic emissions prior to COVID19 lockdown. Furthermore, it was estimated that emission of up to 3243, 777, 113, and 54 tons/year of CO, NOx, PM_2.5, and SO₂, respectively, could be avoided in Hyderabad alone, if work-from-home is implemented on a 2 days/week basis. The experience from this study can be used to develop policies favoring reduced use of private vehicles or implementation of work-from-home to combat air pollution and reduce carbon emissions.

Evolution of Urban Transportation Policies in India: A Review and Analysis

India’s rising population and vehicular ownership have led to problems such as traffic congestion, pollution, and road accidents. The transportation sector is a crucial player in the country’s economy, but at the same time, it is also a significant contributor to climate change. Since climate change is a global threat, most transportation policies eventually lead to solving the climate change problem to achieve sustainable transportation. Despite commitments from various countries, the carbon emissions are still to come down and require the implementation of ambitious policies. Globally, countries are increasingly putting more effort towards sustainable transportation through various policy initiatives, and so does India. Given the growing transport-related externalities, the policy stance of India towards urban transportation is also gradually shifting to a systems approach from supply-oriented to demand-oriented policies. This paper highlights the significant transportation problems faced in India and how the Government of India’s transportation sector policy interventions for cities have evolved since its independence. The challenges and gaps in the existing policies are discussed, and possible ways to frame the policies are presented. This study finds that most government policy initiatives are still to see the intended level of success. This is majorly due to lack of monitoring, complex institutional capacities and urban governance, irregular zoning of land and inefficient comprehensive development and mobility plans.

Impact of lockdown associated with COVID19 on air quality and emissions from transportation sector: case study in selected Indian metropolitan cities

This study examines the impact of air quality in selected Indian metropolitan cities during the COVID19 pandemic lockdown period. Concentrations of air quality parameters such as PM_2.5, NO₂, SO₂, and CO during the transition to lockdown and the actual lockdown period were compared with business as usual periods (a period prior to COVID19 lockdown and a corresponding period in 2019) to estimate the reduction in emission in four major IT hubs in India namely Bengaluru, Chennai, Hyderabad and Pune. A 40-45% reduction in PM_2.5 concentration was observed, in these cities, during the lockdown compared to the corresponding period in 2019 and a 20-45% reduction was observed compared to business as usual period in 2020. A vehicle kilometer traveled (VKT)-related questionnaire survey-based study in Hyderabad revealed that, with 48% of population utilizing work-from-home during the transition to lockdown period, vehicular PM_2.5 emission in Hyderabad reduced by 54% compared to usual traffic emissions prior to COVID19 lockdown. Furthermore, it was estimated that emission of up to 3243, 777, 113, and 54 tons/year of CO, NOx, PM_2.5, and SO₂, respectively, could be avoided in Hyderabad alone, if work-from-home is implemented on a 2 days/week basis. The experience from this study can be used to develop policies favoring reduced use of private vehicles or implementation of work-from-home to combat air pollution and reduce carbon emissions.

Avoiding high ozone pollution in Delhi, India

Quantify the influence of aerosol light extinction on surface ozone photochemistry, highlight controlling VOC for improving air quality in Delhi.

Exceedances and trends of particulate matter (PM2.5) in five Indian megacities

Fine particulate matter (PM_2.5) is the leading environmental risk factor that requires regular monitoring and analysis for effective air quality management. This work presents the variability, trend, and exceedance analysis of PM_2.5 measured at US Embassy and Consulate in five Indian megacities (Chennai, Kolkata, Hyderabad, Mumbai, and New Delhi) for six years (2014-2019). Among all cities, Delhi is found to be the most polluted city followed by Kolkata, Mumbai, Hyderabad, and Chennai. The trend analysis for six years for five megacities suggests a statistically significant decreasing trend ranging from 1.5 to 4.19 μg/m³ (2%-8%) per year. Distinct diurnal, seasonal, and monthly variations are observed in the five cities due to the different site locations and local meteorology. All cities show the highest and lowest concentrations in the winter and monsoon months respectively except for Chennai which observed the lowest levels in April. All the cities consistently show morning peaks (~08: 00-10:00 h) and the lowest level in late afternoon hours (~15:00-16:00 h). We found that the PM_2.5 levels in the cities exceed WHO standards and Indian NAAQS for 50% and 33% of days in a year except for Chennai. Delhi is found to have more than 200 days of exceedances in a year and experiences an average 15 number of episodes per year when the level exceeds the Indian NAAQS. The trends in the exceedance with a varying threshold (20-380 μg/m³) suggest that not only is the annual mean PM_2.5 decreasing in Delhi but also the number of exceedances is decreasing. This decrease can be attributed to the recent policies and regulations implemented in Delhi and other cities for the abatement of air pollution. However, stricter compliance of the National Clean Air Program (NCAP) policies can further accelerate the reduction of the pollution levels.

Impact of Shutdown due to COVID-19 Pandemic on Aerosol Characteristics in Kanpur, India

BACKGROUND

Since March 2020, the number of confirmed COVID-19 positive cases have steadily risen in India. Various preventive measures have been taken to contain the spread of COVID-19. With restrictions on human activities, anthropogenic emissions driving air pollution levels have seen a reduction since March 23, 2020, when the government imposed the first nationwide shutdown. The landlocked Indo-Gangetic Plain (IGP) has many densely-populated cities, witnessing high levels of particulate matter due to both nature-driven and anthropogenic elements. Kanpur is an urban metropolis in the IGP with high aerosol loading, and this paper explores the impact of restricted anthropogenic activities on aerosol characteristics in Kanpur.

OBJECTIVES

This study aims to investigate the change in aerosol optical depth level and its related parameters during the shutdown phases in Kanpur city compared to the same time periods in 2017-2019.

METHODS

Aerosol optical properties such as aerosol optical depth (AOD) at 500 nm, Angstrom exponent (AE), fine mode fraction (FMF) of AOD at 500 nm and single scattering albedo (SSA) at 440 nm were obtained from the Aerosol Robotic Network (AERONET) station operating in Kanpur from the 1st March to the 30th April for 2017-2020.

RESULTS

A significant decrease in aerosol loading was observed during the shutdown period compared to the pre-and partial shutdown periods in 2020 as well as during the same time periods of 2017-2019. Mean AOD, FMF and SSA were 0.37, 0.43 and 0.89, respectively, during the shutdown period in 2020. A 20-35% reduction in mean AOD levels was observed during the shutdown period in 2020 as compared to the same period in 2017-2019.

CONCLUSIONS

The shutdown led to an improvement in air quality due to decreases in anthropogenic emissions. As fine particles, typically from urban and industrial emissions, dominate episodic air pollution events, this study can be further utilized by the scientific community and regulators to strengthen the emergency response action plan to check high pollution episodes in Kanpur city until cleaner technologies are in place.

COMPETING INTERESTS

The authors declare no completing financial interests.

A Distinctive Symmetric Analyzation of Improving Air Quality Using Multi-Criteria Decision Making Method under Uncertainty Conditions

This world has a wide range of technologies and possibilities that are available to control air pollution. Still, finding the best solution to control the contamination of the air without having any impact on humans is a complicated task. This proposal helps to improve the air quality using the multi-criteria decision making method. The decision to improve air quality is a challenging problem with today’s technology and environmental development level. The multi-criteria decision making method is quite often faced with conditions of uncertainty, which can be tackled by employing fuzzy set theory. In this paper, based on an objective weighting method (CCSD), we explore the improved fuzzy MULTIMOORA approach. We use the classical Interval-Valued Triangular Fuzzy Numbers (IVTFNs), viz. the symmetric lower and upper triangular numbers, as the basis. The triangular fuzzy number is identified by the triplets; the lowest, the most promising, and the highest possible values, symmetric with respect to the most promising value. When the lower and upper membership functions are equated to one, we get the normalized interval-valued triangular fuzzy numbers, which consist of symmetric intervals. We evaluate five alternatives among the four criteria using an improved MULTIMOORA method and select the best method for improving air quality in Tamil Nadu, India. Finally, a numerical example is illustrated to show the efficiency of the proposed method.

Diurnal and temporal changes in air pollution during COVID-19 strict lockdown over different regions of India

Lockdown measures to contain COVID-19 pandemic has resulted in a considerable change in air pollution worldwide. We estimate the temporal and diurnal changes of the six criteria air pollutants, including particulate matter (PM2.5 and PM10) and gaseous pollutants (NO2, O3, CO, and SO2) during lockdown (25th March - 3rd May 2020) across regions of India using the observations from 134 real-time monitoring sites of Central Pollution Control Board (CPCB). Significant reduction in PM2.5, PM10, NO2, and CO has been found in all the regions during the lockdown. SO2 showed mixed behavior, with a slight increase at some sites but a comparatively significant decrease at other locations. O3 also showed a mixed variation with a mild increase in IGP and a decrease in the South. The absolute decrease in PM2.5, PM10, and NO2 was observed during peak morning traffic hours (08-10 Hrs) and late evening (20-24 Hrs), but the percentage reduction is almost constant throughout the day. A significant decrease in day-time O3 has been found over Indo Gangetic plain (IGP) and central India, whereas night-time O3 has increased over IGP due to less O3 loss. The most significant reduction (∼40-60%) was found in PM2.5 and PM10. The highest decrease in PM was found for the north-west and IGP followed by South and central regions. A considerable reduction (∼30-70%) in NO2 was found except for a few sites in the central region. A similar pattern was observed for CO having a ∼20-40% reduction. The reduction observed for PM2.5, PM10, NO2, and enhancement in O3 was proportional to the population density. Delhi's air quality has improved with a significant reduction in primary pollutants, however, an increase in O3 was observed. The changes reported during the lockdown are combined effect of changes in the emissions, meteorology, and atmospheric chemistry that requires detailed investigations.

The Critical Role of Policy Enforcement in Achieving Health, Air Quality, and Climate Benefits from India's Clean Electricity Transition

The coal-dominated electricity system poses major challenges for India to tackle air pollution and climate change. Although the government has issued a series of clean air policies and low-carbon energy targets, a key barrier remains enforcement. Here, we quantify the importance of policy implementation in India's electricity sector using an integrated assessment method based on emissions scenarios, air quality simulations, and health impact assessments. We find that limited enforcement of air pollution control policies leads to worse future air quality and health damages (e.g., 14 200 to 59 000 more PM_2.5-related deaths in 2040) than when energy policies are not fully enforced (5900 to 8700 more PM_2.5-related deaths in 2040), since coal power plants with end-of-pipe controls already emit little air pollution. However, substantially more carbon dioxide will be emitted if low-carbon and clean coal policies are not successfully implemented (e.g., 400 to 800 million tons more CO₂ in 2040). Thus, our results underscore the important role of effectively implementing existing air pollution and energy policy to simultaneously achieve air pollution, health, and carbon mitigation goals in India.

Identification of Key Factors to Reduce Transport-Related Air Pollutants and CO2 Emissions in Asia

Asian countries are major contributors to global air pollution and greenhouse gas emissions, with transportation demand and emissions expected to increase. However, few studies have been performed to evaluate policies that could reduce transport-related emissions in the region. This study explores transport-related CO2 and air pollutant emissions in major Asian nations along with the impacts of transport, climate, and emission control policies using the Asia-Pacific Integrated Model (AIM)/Transport model. Our results show that by 2050, CO2 emissions in developing countries will be 1.4–4.7-fold greater than the levels in 2005, while most air pollutant emissions will show large reductions (mean annual reduction rates of 0.2% to 6.1%). Notably, implementation of transport, emission control, and carbon pricing policies would reduce CO2 emissions by up to 33% and other air pollutants by 43% to 72%, depending on the emission species. An emission control policy represents the strongest approach for short-term and mid-term reduction of air pollutants. A carbon pricing policy would lead to a direct reduction in CO2 emissions; more importantly, air pollutant emissions would also be effectively reduced. Shifting to public transportation in developing countries can also greatly influence emissions reductions. An increase in traffic speed shows relatively small effects, but can be meaningful in Japan.