Wintertime fine aerosol particles composition and its evolution in two megacities of southern and northern China

Study on fine aerosols composition can help understand the particles formation and is crucial for improving the accuracy of model simulations. Based on field data measured by a Q-ACSM (Quadrupole-Aerosol Chemical Speciation Monitor), we have comprehensively compared the characteristics, evolution, and potential formation mechanisms of the components in NR-PM2.5 during wintertime at two megacities (Beijing and Guangzhou) of southern and northern China. We show that as PM pollution intensifies, the mass fraction of the primary aerosols (e.g., COA, HOA) in PM2.5 in Guangzhou increased, along with a slight decline in proportion of both the secondary organic (SOA) and inorganic (SIA) aerosols; In contrast, in Beijing, the proportion of the SIA ramped up from 28 % to 53 % with the pollution evolution; and the fraction of SOA in total OA also increased due to a substantial increment in the proportion of MO-OOA (from 29 % to 48 %), suggesting a significance of the secondary processes in worsening aerosols pollution in Beijing. Our further analysis demonstrates a leading role of aqueous pathway in the secondary formation of aerosols at the Beijing site, presenting an exponential rising of SIA and SOA with the relative humidity (RH) increase. Compared to Beijing, however, we find that the photochemical oxidation other than aqueous process in Guangzhou plays a more critical role in those secondary aerosols formation. Combined with the Hysplit trajectory model, we identify the high humid conditions in Guangzhou are typically affected by clean marine air masses, explaining the slower response of secondary components to the RH changes. Moreover, the particles in Guangzhou were observed less hygroscopic that is adverse to the aerosol aqueous chemistry. The results provide basis for the precise control of PM pollution in different regions across China and would be helpful in improving model simulations.

Spatio-temporal dynamics and human-land synergistic relationship of urban expansion in Chinese megacities

Megacities play important roles in countries' politics, economy, culture, etc. Exploring the law of urban expansion of megacities has important reference for sustainable urbanization. Here, the spatiotemporal dynamics of urban expansion were quantified analyzed in 21 Chinese megacities from 2000 to 2020 with quantitative measurement indicators and explored the human-land synergistic relationship used the decoupling model. Results are as follows: (1) China's megacities experienced significant expansion, and urban expansion characterized as rapid initially but slowed down thereafter. (2) Urban expansion in megacities was characterized as having significant spatial differences, and rapidly expanding megacity centers moved from eastern to midwestern China. (3) Urban spatial expansion of megacities was mainly an enclave type in 2000-2010 and marginal type in 2010-2020. (4) The main type of human-land synergistic relationship in megacities were weak decoupling, there is a significant increase in expansive coupling and expansive negative decoupling in 2010-2020; (5) Lastly, human-land synergy relationship in most megacities was uncoordinated based on the per capita urban land area and decoupling type. The findings of this study can deepen the understanding of the characteristics and quality of urbanization evolution, and provides reference for high-quality development planning and decision-making in megacities.

Low-carbon energy policies benefit climate change mitigation and air pollutant reduction in megacities: An empirical examination of Shenzhen, China

The low-carbon transformation of energy system has great significance for megacities to mitigate climate change, which brings co-benefits to improve urban air quality. Taking China's megacity, Shenzhen, as an example, this study examines the potential of wide-ranging energy policies in urban GHG emission reduction and the associated synergistic effect on decreasing major air pollutant emissions. Based on the low emissions analysis platform (LEAP) model, the major results show that an effective implementation of newly emerging energy policies could help cap GHG emissions of Shenzhen in 2025 and nearly halve them by 2035, which would contribute substantially to reducing urban air pollutant emissions. At the sectoral level, the synergistic effect of emission reduction would be the strongest in the transportation sector, followed by the electricity and manufacturing sectors, while it is not significant in the building sector. Moreover, all policies on energy efficiency improvement and demand management that reduce fossil energy consumption show synergistic effects on decreasing air pollutants, while policies on energy structural optimization show differentiated impacts across SO₂, NOx, VOCs, and PM_2.5. Urban managers should prioritize energy policies with strong synergistic effects and specifically promote the wide application of rooftop PV system and deep electrification of road transportation.

Frequency distribution of pollutant concentrations over Indian megacities impacted by the COVID-19 lockdown

The megacities experience poor air quality frequently due to stronger anthropogenic emissions. India had one of the longest lockdowns in 2020 to curb the spread of COVID-19, leading to reductions in the emissions from anthropogenic activities. In this article, the frequency distributions of different pollutants have been analysed over two densely populated megacities: Delhi (28.70° N; 77.10° E) and Kolkata (22.57° N; 88.36° E). In Delhi, the percentage of days with PM_2.5 levels exceeding the National Ambient Air Quality Standards (NAAQS) between 25 March and 17 June dropped from 98% in 2019 to 61% in 2020. The lockdown phase 1 brought down the PM₁₀ (particulate matter having an aerodynamic diameter ≤ 10 μm) levels below the daily NAAQS limit over Delhi and Kolkata. However, PM₁₀ exceeded the limit of 100 μgm^-3 during phases 2-5 of lockdown over Delhi due to lower temperature, weaker winds, increased relative humidity and commencement of limited traffic movement. The PM_2.5 levels exhibit a regressive trend in the highest range from the year 2019 to 2020 in Delhi. The daily mean value for PM_2.5 concentrations dropped from 85-90 μgm^-3 to 40-45 μgm^-3 bin, whereas the PM₁₀ levels witnessed a reduction from 160-180 μgm^-3 to 100-120 μgm^-3 bin due to the lockdown. Kolkata also experienced a shift in the peak of PM₁₀ distribution from 80-100 μgm^-3 in 2019 to 20-40 μgm^-3 during the lockdown. The PM_2.5 levels in peak frequency distribution were recorded in the 35-40 μgm^-3 bin in 2019 which dropped to 15-20 μgm^-3 in 2020. In line with particulate matter, other primary gaseous pollutants (NO_x, CO, SO₂, NH₃) also showed decline. However, changes in O₃ showed mixed trends with enhancements in some of the phases and reductions in other phases. In contrast to daily mean O₃, 8-h maximum O₃ showed a reduction over Delhi during lockdown phases except for phase 3. Interestingly, the time of daily maximum was observed to be delayed by ~ 2 h over Delhi (from 1300 to 1500 h) and ~ 1 h over Kolkata (from 1300 to 1400 h) almost coinciding with the time of maximum temperature, highlighting the role of meteorology versus precursors. Emission reductions weakened the chemical sink of O₃ leading to enhancement (120%; 11 ppbv) in night-time O₃ over Delhi during phases 1-3.

Assessment of the effect of the judicial prohibition on firecracker celebration at the Diwali festival on air quality in Delhi, India

Diwali (the festival of lights and crackers) is celebrated grandly, resulting in a significant drop in the city's air quality. To study the impact of the judicial prohibition in Delhi to improve air quality, a comprehensive and comparative analysis was conducted over two consecutive years, namely 2015-2016 (when no significant regulations on the sale or usage of firecrackers were imposed) and 2017-2018 (when radically different regulations were implemented). Data on PM₁₀, PM_2.5, NO_x, and CO were analysed, and their trends and levels with various regulations in place were compared. In 2017, the concentrations of PM₁₀, PM_2.5, NO_x, and CO were reduced by 50%, 50%, 71%, and 64%, respectively, compared to 2016. However, in 2018, there was an increase of 32% in PM₁₀ and PM_2.5 concentrations, as well as a 25% increase in CO concentrations, with the exception of NOx, which decreased to 25% on Diwali day. The data was also examined in conjunction with the entire timeline of the various court rulings and regulations imposed in Delhi. The questionnaire survey study revealed that, despite the legislation in place, ambient air quality continued to deteriorate, necessitating a deeper dive into the policy's structure and implementation to fine-tune its feasibility and applications. Air pollution-related health effects were recognized by 82% of participants. Despite this, only 13% of people were observed without a mask, and only 12% of people were aware of green crackers as of 2018. To combat this deteriorating situation, the national capital must enact radical and well-thought-out legislation and regulations governing firecrackers, as well as raise public awareness amongst its citizens.

The dynamics of cardiovascular and respiratory deaths attributed to long-term PM2.5 exposures in global megacities

Exposure to ambient fine particulate matter (PM_2.5) air pollution is a significant driver of premature deaths. We estimate the number of cardiovascular and respiratory (CR) premature deaths attributed to long-term exposure to PM_2.5 in 33 global megacities based on long-term remotely sensed observations from 2000 to 2019. Our analysis uses high-resolution (0.01 degree) PM_2.5 concentration data and cause-specific integrated exposure-response (IER) functions developed for the Global Burden of Disease Project. From 2000 to 2019, PM_2.5-related CR death rates per 1000 people increased in 6 of 33 megacities, decreased in 9, and remained constant in 18 megacities. The increase in PM_2.5-related CR mortality in 11 megacities located in South and East Asia during the period 2000-2019 can be attributed to the increases in PM_2.5 concentrations. All 33 megacities could avoid 30,248 (9 %), 62,989 (20 %), 128,457 (40 %), 198,462 (62 %) and all of the estimated 322,515 CR deaths attributed to PM_2.5 pollution in 2019 if they were to attain the World Health Organization's four interim PM_2.5 targets (IT-1, IT-2, IT-3, and IT-4) and the new air quality guideline (AQG), respectively. Major improvements in air quality are needed to reduce the number of CR deaths attributed to PM_2.5 in South and East Asia, in addition to ny reductions that would likely follow shifts in the population structures of these megacities moving forward.

Key Social Determinants to Narrow the Gap between Health-adjusted Life Expectancy and Life Expectancy in Megacities

OBJECTIVE

Improvement in the quality of life is reflected in the narrowing of the gap between health-adjusted life expectancy (HALE) and life expectancy (LE). The effect of megacity expansion on narrowing the gap is rarely reported. This study aimed to disclose this potential relationship.

METHODS

Annual life tables were constructed from identified death records and population counts from multiple administrative sources in Guangzhou, China, from 2010 to 2020. Joinpoint regression was used to evaluate the temporal trend. Generalized principal component analysis and multilevel models were applied to examine the county-level association between the gap and social determinants.

RESULTS

Although LE and HALE in megacities are increasing steadily, their gap is widening. Socio-economic and health services are guaranteed to narrow this gap. Increasing personal wealth, a growing number of newborns and healthy immigrants, high urbanization, and healthy aging have helped in narrowing this gap.

CONCLUSION

In megacities, parallel LE and HALE growth should be highly considered to narrow their gap. Multiple social determinants need to be integrated as a whole to formulate public health plans.

Particle characterization and quantification of organic and inorganic compounds from Chinese and Iranian aerosol filter samples using scanning laser desorption/ionization mass spectrometry

Besides their influence on climate and cloud formation, many organic and inorganic substances in aerosol particles pose a risk to human health. Namely, polycyclic aromatic hydrocarbons (PAH) and heavy metals are suspected to be carcinogenic or acutely toxic. The detection and quantification of such compounds is difficult if only small amounts of particulate matter (PM) are available. In addition, filter samples are often complex and time-consuming to prepare for chromatographic measurements and elemental analysis. Here, we present a method based on high-resolution atmospheric pressure laser desorption ionization mass spectrometry imaging (AP-LDI-MSI) and statistical analysis which allows the analysis and characterization of very small sample quantities (< 30 µg) without any sample preparation. The power and simplicity of the method is demonstrated by two filter samples from heavily polluted mega cities. The samples were collected in Tehran (Iran) and Hangzhou (China) in February 2018. In the course of the measurement, more than 3200 sum formulae were assigned, which allowed a statistical evaluation of colocalized substances within the particles on the filter samples. This resulted in a classification of the different particle types on the filters. Finally, both megacities could be distinguished based on characteristic compounds. In the samples from Tehran, the number of sulphur-containing organic compounds was up to 6 times as high as the samples from Hangzhou, possibly due to the increasing efforts of the Chinese government to reduce sulphur emissions in recent years. Additionally, quantification of 13 PAH species was carried out via standard addition. Especially, the samples from Tehran showed elevated concentrations of PAHs, which in the case of higher-molecular-weight species (> m/z 228) were mostly more than twice as high as in Hangzhou. Both cities showed high levels of heavy metals and potentially harmful organic compounds, although their share of total particulate matter was significantly higher in the samples from Tehran. The pre-treatment of the samples was reduced to a minimum with this method, and only small amounts of particles were required to obtain a comprehensive picture for a specific filter sample. The described method provides faster and better control of air pollution in heavily polluted megacities.

Stated benefits of teleworking in Mexico City: a discrete choice experiment on office workers

Commuting is expensive in megacities of emerging economies. By decreasing work-related trips, teleworking may reduce congestion and commuting time. Taking Mexico City's office workers' as case study, this paper reports findings from a discrete choice experiment (DCE) exploring willingness to see a cut in monthly paycheck in exchange for teleworking two days a week from a shared office. This DCE explores preferences for bike parking spaces at shared office's facilities, and walking commuting time to shared office. This design allows estimation of willingness to pay (WTP) for teleworking across commuting time scenarios. Monthly WTP for teleworking 2 days a week starts at (2019) USD 76.68-if commuting time is zero. As 1 h of commuting time is valued at USD 61.97 on a monthly basis, WTP for teleworking 30 min away from home is USD 45.69. Wealthier respondents report higher value for commuting time and WTP for teleworking. Monthly value of bike parking infrastructure is USD 14.70-reaching USD 30.98 for commuters that walk or (motor-)bike less than 50 min. We illustrate how these stated benefits can inform cost-benefit analysis of transportation, housing, and labor policies that enable teleworking and/or reduce commuting times in Mexico City.

Polyethylene scaffold net and synthetic grass fragmentation: a source of microplastics in the atmosphere?

Microplastics (MPs) implications in the atmosphere are of current global concern. Currently, there is a growing interest regarding source appointment, fate, level of toxicity, and exposure intensity of ambient air MPs. Recent data suggest that polyethylene (PE) dominates ambient MPs in China's megacities. Albeit understanding of PE sources is limited and restricted to typical sources polluting terrestrial and marine environments. However, the air is a distinct environmental component and may have some separate pollution sources as well as the relative contribution of different sources could also contrast in different environments. Urbanization and fast construction activity resulting from increased economic growth in these places might be a potential source of ambient PE. Recently, the use of scaffold netting on construction sites and synthetic grass as land covering sheets has been on the rise. Generally, these PE items are often inferior and composed of recycled material, making them more prone to degradation. Also, because these items were continually exposed to open air, there is a considerable risk of fragmentation and atmospheric mixing. Therefore, unchecked and excessive usage of these materials can be risky. Here, PE's physical and chemical characteristics, transport and health risks in urban air are discussed here.

Are leading urban centers predisposed to global risks- A analysis of the global south from COVID-19 perspective

COVID-19 initially spread among prominent global cities and soon to the urban centers of countries across the globe. While cities are the hotbeds of activities, they also seem highly exposed to global risks including the pandemic. Using the case of COVID-19 and the World Risk Index framework, this paper examines if the leading cities from the global south are inherently vulnerable and exposed to global risks and can they exacerbate the overall risk of their respective nations. Compared against their respective national averages, most of the 20 cities from 10 countries analyzed in this paper, have higher exposure, lower adaptive capacity, higher coping capacity and varied susceptibility. As this relative understanding is based on respective national averages which are often lower than the global standards, even high performance on certain indicators may still result in elevated predisposition. This paper concludes that the leading urban centers from the global south are highly likely to be predisposed to global risks due to their inherent vulnerability and exposure, and many of the drivers of this predisposition are related to the process of urbanization itself. This predisposition can enhance the overall exposure and vulnerability of the nation in which they are located.

Energy, environmental, resource recovery, and economic dimensions of municipal solid waste management paths in Mexico city

Growing municipal solid waste (MSW) generation is a source of environmental, economic, and social concerns, especially in developing world megacities where poor MSW practices prevail. Mexico City (CDMX), one of the world's largest megacities, daily produces ∼ 13,073 Mg of MSW whose management poses a tremendous challenge to local authorities and calls for additional research to conceive sound MSW strategies. This study evaluates the fossil energy use, GHG emissions, resource recovery, and economic cost dimensions of current and five alternative MSW paths in CDMX to compare their performance and identify more sustainable MSW practices for the megacity. Impacts and benefits from the MSW paths were modeled using 2018 MSW generation data, information supplied by local authorities, and literature values. Current MSW path consumes ∼ 387 MJ_fossil, generates ∼ 501 kg-CO₂e, and costs ∼ 57 USD₂₀₁₈ per Mg of MSW managed while it only valorizes < 33% of total MSW mostly via informal truck-picking. The alternative MSW paths considerably reduce GHG emissions (∼129-360 kg-CO₂e/Mg) and enhance MSW valorization (∼47-88%) though, they entail higher fossil energy consumption (447-582 MJ_fossil/Mg) and, in general, higher cost expenditures (43-208 USD₂₀₁₈/Mg). Heavy reliance on landfilling, large GHG emissions, and low MSW valorization make current MSW path in CDMX unsustainable. Incineration-based MSW paths perform better in most aspects evaluated but their high costs seem prohibitive. Results suggest MSW paths featuring open windrow composting, mechanical-biological pre-treatment, material recovery facilities, and refuse-derived fuel production may be more appropriate to improve the sustainability of CDMX MSW management.

Impact of the COVID-19 pandemic: Insights from vacation rentals in twelve mega cities

Coronavirus disease 2019 (COVID-19) is a challenging global problem. COVID-19 has caused shocks to various urban systems, and the tourism industry is no exception. We analyzed the impact on vacation rentals by conducting diachronic data mining on nearly 10 GB of rental data (calendar, listings, and reviews) in twelve highly internationalized megacities distributed across Asia, Europe, America, and Oceania based on the data set from the Inside Airbnb website. All twelve cities were adversely affected. The specific time of the impact is related to the pandemic's outbreak and enforced lockdowns policies. Affected by the epidemic, reservation rates decreased, tourists preferred renting in suburbs instead of city centers, the proportion of foreign tourists in all destinations dropped sharply, tourist sentiment scores fluctuated dramatically especially among foreigners, and people focused less on tourism related activities. This study reveals the changing illustrations of vacation rentals in highly internationalized megacities under the pandemic's influence. It offers a methodological assessment framework to monitor the hospitality sector over time and aims to serve as a reference for preparedness in similar cities worldwide.

Air pollution and hospitalization in megacities: empirical evidence from Pakistan

Air pollution has become a threat to human health in urban settlements, ultimately leading to negative impacts on overall economic system as well. Already developed nations and still developing countries both are at the risk of air pollution globally. In this scenario, this work aims to investigate the associations of asthma (AS) and acute upper respiratory infection (ARI) patients with satellite-based aerosol optical depth (AOD) and meteorological factors, i.e., relative humidity (RH), temperature (TEMP), and wind speed (WS). We applied second-generation unit root tests to provide empirical evidence. Two sets of unit root tests confirmed mix order of integration, and the other Westerlund co-integration test further showed strong linkages between estimated variables. Fully modified ordinary least square (FMOLS) and dynamic ordinary least square (DOLS) tests were applied, only to explore that TEMP and WS lower the number of AS and ARI patients, but RH and AOD increase the number of patients. Therefore, in accordance with these findings, our study provides some important policy instruments to improve the health status in megacities of Pakistan.

Effects of COVID-19 pandemic on the air quality of three megacities in India

COVID-19 pandemic compelled many countries in the world to go for a nationwide lockdown to prevent the spread of the coronavirus. India started the lockdown on 24 March 2020. We analyzed the air quality of three megacities of India, namely Mumbai, Delhi, and Kolkata, during the lockdown phase and compared it with the pre-lockdown and post-lockdown scenarios. We considered seven major air pollutants: PM_2.5, PM₁₀, NO₂, NH₃, SO₂, CO, and O₃. We analyzed the data acquired from 56 automatic air-monitoring stations (AAMS) under the Central Pollution Control Board (CPCB) spread across the megacities. The air pollution level in the eastern part of Mumbai and the western part of Delhi and Kolkata usually remains high. Delhi was the worst polluted megacity, followed by Kolkata and Mumbai. The stop of vehicular movements and industrial lockdown across the nation has substantial effects on the environment, especially in the atmosphere near the Earth's surface. Our analysis showed significant improvements in air quality during the period of lockdown (25 March to 14 April 2020) compared to the pre-lockdown phase (3 March to 23 March 2020) and the same time window of the previous year (25 March to 14 April 2019). The post-lockdown (15 April to 5 May) phase exhibited mixed results. We mapped the spatial pattern of these pollutants and the air quality index (AQI). According to CPCB, PM_2.5, PM₁₀, and CO are the major air pollutants in India that reduced by 47%, 41%, and 27% in Mumbai; 52%, 39%, and 13% in Delhi; and 49%, 37%, and 21% in Kolkata, respectively, in the lockdown phase. PM_2.5, PM₁₀, and NO₂ exhibited significant correlations across the three megacities. This study shows that occasional short-term lockdowns can effectively refresh the air in these megacities.

Comparing tweet sentiments in megacities using machine learning techniques: In the midst of COVID-19

COVID-19 was announced by the World Health Organization as a pandemic on March 11, 2020. Not only has COVID-19 struck the economy and public health, but it also has deep influences on people's feelings. Twitter, as an active social media, is a great database where we can investigate people's sentiments during this pandemic. By conducting sentiment analysis on Tweets using advanced machine learning techniques, this study aims to investigate how public sentiments respond to the pandemic from March 2 to May 21, 2020 in New York City, Los Angeles, London, and another six global mega-cities. Results showed that across cities, negative and positive Tweet sentiment clustered around mid-March and early May, respectively. Furthermore, positive sentiments of Tweets from New York City and London were positively correlated with stricter quarantine measures, although this correlation was not significant in Los Angeles. Meanwhile, Tweet sentiments of all three cities did not exhibit a strong correlation with new cases and hospitalization. Last but not least, we provide a qualitative analysis of the reasons behind differences in correlations shown above, along with a discussion of the polarizing effect of public policies on Tweet sentiments. Thus, the results of this study imply that Tweet sentiment is more sensitive to quarantine orders than reported statistics of COVID-19, especially in populous megacities where public transportation is heavily relied upon, which calls for prompt and effective quarantine measures during contagious disease outbreaks.

Improving Decision-Making for Population Health in Nonhealth Sectors in Urban Environments: the Example of the Transportation Sector in Three Megacities-the 3-D Commission

Noncommunicable diseases (NCDs) represent a significant global public health burden. As more countries experience both epidemiologic transition and increasing urbanization, it is clear that we need approaches to mitigate the growing burden of NCDs. Large and growing urban environments play an important role in shaping risk factors that influence NCDs, pointing to the ineluctable need to engage sectors beyond the health sector in these settings if we are to improve health. By way of one example, the transportation sector plays a critical role in building and sustaining health outcomes in urban environments in general and in megacities in particular. We conducted a qualitative comparative case study design. We compared Bus Rapid Transit (BRT) policies in 3 megacities-Lagos (Africa), Bogotá (South America), and Beijing (Asia). We examined the extent to which data on the social determinants of health, equity considerations, and multisectoral approaches were incorporated into local politics and the decision-making processes surrounding BRT. We found that all three megacities paid inadequate attention to health in their agenda-setting, despite having considerable healthy transportation policies in principle. BRT system policies have the opportunity to improve lifestyle choices for NCDs through a focus on safe, affordable, and effective forms of transportation. There are opportunities to improve decision-making for health by involving more available data for health, building on existing infrastructures, building stronger political leadership and commitments, and establishing formal frameworks to improve multisectoral collaborations within megacities. Future research will benefit from addressing the political and bureaucratic processes of using health data when designing public transportation services, the political and social obstacles involved, and the cross-national lessons that can be learned from other megacities.

Impact of COVID-19 lockdown on ambient air quality in megacities of India and implication for air pollution control strategies

The impact of restrictions during various phases of COVID-19 lockdown on daily mean PM_2.5 concentration in five Indian megacities (New Delhi, Chennai, Kolkata, Mumbai, and Hyderabad) was studied. The impact was studied for pre-lockdown (1st Mar-24th Mar 2020), lockdown (25th Mar-31st May 2020), and unlocking (1st Jun-31st Aug 2020) phases. The lockdown period comprises 4 lockdown phases with distinct measures, whereas the unlocking period had 3 phases. PM_2.5 concentration reduced significantly in all megacities and met the national standards during the lockdown period. The maximum reduction in PM_2.5 level was observed in Kolkata (62%), followed by Mumbai (49%), Chennai (34%), and New Delhi (26%) during the lockdown period. Comparatively, Hyderabad exhibited a smaller reduction in PM_2.5 concentration, i.e., 10%. The average PM_2.5 levels during the lockdown in the peak hour (i.e., 07:00-11:00 h) in New Delhi, Chennai, Kolkata, Mumbai, and Hyderabad decreased by 21.3%, 48.5%, 63.4%, 56.4%, and 23.8%, respectively, compared to those before lockdown period. During the unlocking period, except for Chennai, all megacities showed a reduction in average PM_2.5 levels compared to concentrations in the lockdown period, but these reductions were mainly linked with monsoon rains in India. The current study provided an opportunity to study air pollution in the absence of major anthropogenic activities and during limited activities in monsoon season having an ecological design. The study reports a new baseline of PM_2.5, except for monsoon, and explores this knowledge to plan future air pollution reduction strategies. The study also discusses how this new learning of knowledge could strengthen air pollution control policies for better air quality and sustainability.Graphical abstract.

Short-term impacts of air pollutants in three megacities of India during COVID-19 lockdown

Lockdown was imposed by the Indian government in the month of March 2020 as an early precaution to the COVID-19 pandemic which obstructed the socio-economic growth globally. The main aim of this study was to analyse the impact of lockdown (imposed in March and continued in April 2020) on the existing air quality in three megacities of India (Delhi, Mumbai and Kolkata) by assessing the trends of PM10 and NO2 concentrations. A comparison of the percentage reduction in concentrations of lockdown period with respect to same period in year 2019 and pre-lockdown period (February 14-March 24) was made. It was observed from the study that an overall decrease of pollutant concentrations was in the ranges of 30-60% and 52-80% of PM10 and NO2, respectively, in the three cities during lockdown in comparison with previous year and pre-lockdown period. The overall decrease in concentrations of pollutants at urban sites was greater than the background sites. Highest decline in concentrations of PM10 were observed in Kolkata city, followed by Mumbai and Delhi, while decline in NO2 was highest in Mumbai. Results also highlighted that capital city Delhi had the worst air quality amongst three cities, with particulate matter (PM10) being the dominant pollutant. Although COVID-19 has significantly affected the human life considering the mortality and morbidity, lockdowns imposed to control the pandemic had significantly improved the air quality in the selected study locations, although for the short amount of period.

Disparity in ozone trends under COVID-19 lockdown in a closely located coastal and hillocky metropolis of India

The outbreak of COVID-19, a global health challenge faced by countries worldwide, led to a lockdown in India, thereby bringing down the emissions of various air pollutants. Here, we discuss the behaviour of surface ozone (O₃) concentrations and its precursors, oxides of nitrogen (NO_x), carbon monoxide (CO), and volatile organic compounds (VOC) at two Indian megacities namely Mumbai and Pune, closely located yet vastly differing in meteorology due to their locations. Although levels of CO, NO₂, and VOC declined sharply after the lockdown in both cities, with NO₂ showing the highest reduction, ozone concentration in Pune remained unaffected, whereas Mumbai exhibited a mixed trend, touching even a maximum in between the lockdown. On a diurnal scale, the magnitude of O₃ levels during the lockdown period is higher at almost all hours in Mumbai, and in Pune, it is almost identical except during night hours when it is marginally higher in the lockdown period as compared to the normal period. On a whole, the pollution levels were brought down significantly which can be used as a benchmark in the future for the implementation of policies related to air quality management and emission control in Indian megacities by the policymakers. These results also can pave a way for the scientific community for local air quality modelling.

One decade of VOCs measurements in São Paulo megacity: Composition, variability, and emission evaluation in a biofuel usage context

In South America, the observations of atmospheric pollutants are deficient, and few cities have implemented air quality monitoring programs. In addition, Volatile Organic Compounds (VOCs) observations are still missing, and little is known about their contributions to the atmospheric composition and impacts in a large ethanol usage context like Brazil. Here, we present a wide range of VOCs that have been measured for ten years in São Paulo Megacity (SPM) in different campaigns at traffic, urban and background sites. When compared with other cities worldwide, the average VOCs ambient concentrations in SPM were higher by factors of 2 to 10. However, the ambient VOCs distribution among these cities is homogeneous even for ethanol, aldehydes and alkenes species. Emission ratios (ER) were established related to carbon monoxide and acetylene, which did not depict strong seasonal and interannual variability in SPM. When compared with previous studies, ERs showed an enrichment from road-tunnel to background, suggesting the presence of other sources than traffic. A good agreement in ER was found with Los Angeles and Paris; but limited consistencies with Middle East and Asia cities. Our ethanol measurements show that contrasted ER can be obtained depending on the emission process involved, with a strong impact of evaporation on ethanol concentrations. The multiyear acetaldehyde analysis displayed that ER could be a valuable metric to assess the long-term changes in emissions sources. Finally, VOCs emissions were calculated from ER and compared with those estimated by the global emission inventory (Edgar). The total VOC emissions estimated by the global inventory agree very well with those from our observations up to 75%. Nevertheless, the VOCs speciation is misrepresented in the inventory, mainly for oxygenated and heavier alkanes compounds. These inconsistencies will also have an impact on the quantification of secondary atmospheric pollutants formation associated to road transport emissions.

Unequable spatial accessibility to hospitals in developing megacities: New evidence from Beijing

The increasing inequality in spatial accessibility to hospitals in developing countries has been attracting attention from researchers and politicians. The situation seems to be worse in growing megacities where more than 10 million people live and rapid urban sprawl has caused serious problems with the supply of health and public transport services. The recent global COVID-19 pandemic calls for particular attention to be afforded to the matter of equal access to basic medical facilities and services for people across different neighborhoods. Although some studies have already been undertaken into the subject of health-focused inequality in the cities of developing countries, the spatial inequity in hospital accessibility has rarely been discussed to date. In this paper, I aim to provide new evidence by considering Beijing as a case study. With the results of my analysis, I show that low-income neighborhoods have experienced lower levels of accessibility not only to high-tier hospitals (secondary and tertiary hospitals) but also to primary healthcare services (primary hospital and neighborhood clinics). The rate at which high-income neighborhoods access secondary and tertiary hospitals is approximately 4 times and 1.5 times as high as that of low-income neighborhoods. Low-income face nearly twice the travel time of those from high-income neighborhoods to reach the nearest primary hospital or neighborhood clinics. Suburban neighborhoods have less access to medical services than neighborhoods that are located in the central urban areas. It seems that the rapid urban sprawl has been worsening spatial inequality in the context of access to medical services in the growing megacity of Beijing. Equal access to healthcare services should be prioritized in future policy discussions, especially in relation to the urban growth management of megacities in developing countries in order to ensure that fair and inclusive urbanization processes are undertaken. Equal access to healthcare services would also be widely beneficial in the context of managing the COVID-19 pandemic.

The changing PM2.5 dynamics of global megacities based on long-term remotely sensed observations

Satellite observations show that the rapid urbanization and emergence of megacities with 10 million or more residents have raised PM2.5 concentrations across the globe during the past few decades. This study examines PM2.5 dynamics for the 33 cities included on the UN list of megacities published in 2018. These megacities were classified into densely (>1500 residents per km²), moderately (300-1500 residents per km²) and sparsely (<300 residents per km²) populated areas to examine the effect of human population density on PM2.5 concentrations in these areas during the period 1998-2016. We found that: (1) the higher population density areas experienced higher PM2.5 concentrations; and (2) the megacities with high PM2.5 concentrations in these areas had higher concentrations than those in the moderately and sparsely populated areas of other megacities as well. The numbers of residents experiencing poor air quality is substantial: approximately 452 and 163 million experienced average annual PM2.5 levels exceeding 10 and 35 μg/m³, respectively in 2016. We also examined PM2.5 trends during the past 18 years and predict that high PM2.5 levels will likely continue in many of these megacities in the future without substantial changes in their economies and/or pollution abatement practices. There will be more megacities in the highest PM2.5 pollution class and the number of megacities in the lowest PM2.5 pollution class will likely not change. Finally, we analyzed how the PM2.5 pollution burden varies geographically and ranked the 33 megacities in terms of PM2.5 pollution in 2016. The most polluted regions are China, India, and South Asia and the least polluted regions are Europe and Japan. None of the 33 megacities currently fall in the WHO's PM2.5 attainment class (<10 μg/m³) while 9 megacities fall into the PM2.5 non-attainment class (>35 μg/m³). In 2016, the least polluted megacity was New York and most polluted megacity was Delhi whose average annual PM2.5 concentration of 110 μg/m³ is nearly three times the WHO's non-attainment threshold.

Spatial-temporal variability of metal pollution across an industrial district, evidencing the environmental inequality in São Paulo

Although air pollution decreased in some cities that shifted from an industrial to a service-based economy, and vehicular emission regulation became more restrictive, it is still a major risk factor for mortality worldwide. In central São Paulo, Brazil, air quality monitoring stations and tree-ring analyses revealed a decreasing trend in the concentrations of particulate matter and metals. Such trends, however, may not be observed in industrial districts located in the urban periphery, where the usual mobile sources may be combined with local stationary sources. To evaluate environmental pollution in an industrial district in southeastern São Paulo, we assessed its spatial variability, by measuring magnetic properties and concentrations of Al, Ba, Ca, Cl, Cu, Fe, K, Mg, Mn, P, S, Sr, Zn in the bark of 62 trees, and its temporal trends, by measuring Cd, Cu, Ni, Pb, V, Zn in tree rings of three trees. Source apportionment analysis based on tree barks revealed two clusters with high concentrations of metals, one related to vehicular and industrial emissions (Al, Ba, Cu, Fe, Zn) in the east side of the industrial cluster, and the other related to soil resuspension (Cu, Zn, Mn) in its west side. These patterns are also supported by the magnetic properties of bark associated with iron oxides and titanium-iron alloy concentrations. Dendrochemical analyses revealed that only the concentrations of Pb consistently decreased over the last four decades. The concentrations of Cd, Cu, Ni, V, and Zn did not significantly decrease over time, in contrast with their negative trends previously reported in central São Paulo. This combined biomonitoring approach revealed spatial clusters of metal concentration in the vicinity of this industrial cluster and showed that the local population has not benefited from the decreasing polluting metal concentrations in the last decades.

Ecosystem Services and Economic Assessment of Land Uses in Urban and Periurban Areas

This work quantified ecosystem services (ES) and the geographic gross product (GGP) at municipal level in the Metropolitan Region of Buenos Aires (MRBA), Argentina. The ES offer and GGP were evaluated for each land use (extensive agriculture EA, intensive agriculture IA, urban and periurban agriculture UPA, green areas GA, urban use URB), expressed as a percentage (%), at the municipality level. Municipalities with a greater URB percentage (<70) presented an elevated ES offer from GA. In periurban municipalities EA contributed to ES offer more than other vegetated land uses (IA, GA, and UPA). Urban municipalities presented 20% more GGP than periurban municipalities. The GGP was negatively associated with total ES offer (-0.34) and ES offer from EA (-0.46). The identification and quantification of ES and GGP is relevant for achieving an adequate landscape planning and a sustainable environmental and economic use of urban systems.

Stream loss in an urbanized and agricultural watershed in China

Stream losses are extensively observed due to human activities in the world, and the patterns of stream loss vary in different land use types. However, relationship between stream loss pattern and land use covers is poorly understood. We select the lower Taihu watershed (LTWS) within Yangtze River Delta (YRD), which is dominated by agricultural and urban covers and a typical case of most urbanized watersheds in China. In this study, we measured the stream loss of LTWS from 1960s to 2010s and investigated its relation to different land use covers and impervious area percentage (IAP) in order to figure out the main factor of stream loss in this area. The results show that urban area has tripled with fractional contribution from 10.3% to 33.18% in the form of conversion from agriculture to urban area during 1990-2015. 12.5% of all the streams are lost and 1st-order streams contribute most (91.8%) to the total stream loss. Urban cover contribute most (76%) to total streams loss compared to other land use types. We find that 1st-order streams have highest stream loss intensity, which is mainly caused by urban expansion, but preferred protections are given to highest-order streams. The linear model of correlation of pixel-level streams loss and IAP shows that the streams loss is statistically significant positive with IAP of cells (R² = 0.91). Tradeoffs between city expansion and river network make small channels sacrifice for the urbanization. Urgent measures including legislation must be taken to protect small streams during urbanization nowadays and in future.

Associations between neighborhood-level violence and individual mental disorders: Results from the World Mental Health surveys in five Latin American cities

Rapidly urbanizing areas of Latin America experience elevated but unevenly distributed levels of violence. Extensive research suggests that individual exposure to violence is associated with higher odds of both internalizing (anxiety and mood) and externalizing (substance and intermittent explosive) mental disorders. Less research, however, has focused on how neighborhood-level violence, as an indicator of broader neighborhood contexts, might relate to the mental health of residents, independently of an individual's personal exposure. We used multilevel analyses to examine associations of neighborhood-level violence with individual-level past-year mental disorders, controlling for individual-level violence exposure. We used data from 7,251 adults nested in 83 neighborhoods within five large Latin American cities as part of the WHO World Mental Health Surveys. Accounting for individual-level violence exposure, living in neighborhoods with more violence was associated with significantly elevated odds of individual-level internalizing disorders, but not externalizing disorders. Caution should be exercised when making causal inferences regarding the effects of neighborhood-level violence in the absence of experimental interventions. Nevertheless, neighborhood context, including violence, should be considered in the study of mental disorders. These findings are particularly relevant for rapidly urbanizing areas with high levels of violence, such as Latin America.

Urban land expansion in China's six megacities from 1978 to 2015

Megacities pose both challenges and opportunities for the transition towards sustainability, and understanding the evolution of urbanization in megacities has profound implications for human societies in an increasingly urbanized world. Here, we mapped and quantified spatiotemporal dynamics of urban expansion in China's six megacities (i.e., Beijing, Chongqing, Guangzhou, Shanghai, Shenzhen and Tianjin) from 1978 to 2015, integrating remote sensing and GIS technology combined with landscape metrics and urban growth type analysis. The results show that six Chinese megacities have all undergone extensive physical expansion over the past four decades, and the magnitude of urban expansion is ranked in the order of Shenzhen, Guangzhou, Chongqing, Shanghai, Tianjin and Beijing, with annual growth rates of 11.02%, 8.07%, 5.80%, 5.37%, 4.56% and 3.46%, respectively. The megacities with smaller initial urban areas were associated with higher urban expansion rates. Differences in the direction, extent and location of expansion for each megacity related largely to the topography, policies and urban master planning. Temporal dynamics of urban growth and landscape metrics suggested that the urbanization processes of Beijing, Shanghai, Shenzhen and Tianjin were basically consistent with urban growth theory, while those of Chongqing and Guangzhou did not match the theory well. Temporal coevolution of the urban area with urban population implied efficiency of urban land use in Shenzhen and Beijing, which are the first special economic zone and the capital of China, respectively. The efficiency of wealth creation in the urbanized area base was observed for all Chinese megacities, signifying the effectiveness of urban expansion as a vehicle to promote economic growth. We face the challenge of managing trade-offs between the benefits and costs of urban agglomeration.

Understanding urban expansion combining macro patterns and micro dynamics in three Southeast Asian megacities

Rapid urbanization accelerates urban expansion, especially in populous areas, such as Southeast Asia. The urban forms and changes at the macro level and the dynamics at the patch level are interrelated. Considering its spatiotemporal interdependences and global-local interactions, we propose a framework to quantify urban expansion by combining macro patterns and micro dynamics. Taking three Southeast Asian megacities, Bangkok, Ho Chi Minh City (HCMC), and Manila, as examples, we calculate the urban land densities in concentric rings (macro pattern) and the proximity expansion index (PEI) of new urban patches (micro dynamic) to compare the urban form changes and expansion patterns based on Landsat imagery in 1990, 2000, and 2014. The results show that the urban form changes have close relationships with the local urban patch dynamics. The macro- and micro-level results in Bangkok and Ho Chi Minh City are interrelated and consistent and the explainable inconsistent results in Manila further reveal the necessity of combination of two scopes. The three megacities developed in different manners, thereby resulting in diverse urban forms and changes. Other methods and technologies combining macro and micro perspectives are encouraged to better understand urban expansion.

Statistical exploration of dataset examining key indicators influencing housing and urban infrastructure investments in megacities

Lagos, by the UN standards, has attained the megacity status, with the attendant challenges of living up to that titanic position; regrettably it struggles with its present stock of housing and infrastructural facilities to match its new status. Based on a survey of construction professionals’ perception residing within the state, a questionnaire instrument was used to gather the dataset. The statistical exploration contains dataset on the state of housing and urban infrastructural deficit, key indicators spurring the investment by government to upturn the deficit and improvement mechanisms to tackle the infrastructural dearth. Descriptive statistics and inferential statistics were used to present the dataset. The dataset when analyzed can be useful for policy makers, local and international governments, world funding bodies, researchers and infrastructural investors.

Chemical composition and source apportionment of PM10 at an urban background site in a high-altitude Latin American megacity (Bogota, Colombia)

Bogota registers frequent episodes of poor air quality from high PM₁₀ concentrations. It is one of the main Latin American megacities, located at 2600 m in the tropical Andes, but there is insufficient data on PM₁₀ source contribution. A characterization of the chemical composition and the source apportionment of PM₁₀ at an urban background site in Bogota was carried out in this study. Daily samples were collected from June 2015 to May 2016 (a total of 311 samples). Organic carbon (OC), elemental carbon (EC), water soluble compounds (SO₄^2-, Cl^-, NO₃^-, NH₄⁺), major elements (Al, Fe, Mg, Ca, Na, K, P) and trace metals (V, Cd, Pb, Sr, Ba, among others) were analyzed. The results were interpreted in terms of their variability during the rainy season (RS) and the dry season (DS). The data obtained revealed that the carbonaceous fraction (∼51%) and mineral dust (23%) were the main PM₁₀ components, followed by others (15%), Secondary Inorganic Compounds (SIC) (11%) and sea salt (0.4%). The average concentrations of soil, SIC and OC were higher during RS than DS. However, peak values were observed during the DS due to photochemical activity and forest fires. Although trace metals represented <1% of PM₁₀, high concentrations of toxic elements such as Pb and Sb on RS, and Cu on DS, were obtained. By using a PMF model, six factors were identified (∼96% PM₁₀) including fugitive dust, road dust, metal processing, secondary PM, vehicles exhaust and industrial emissions. Traffic (exhaust emissions + road dust) was the major PM₁₀ source, accounting for ∼50% of the PM₁₀. The results provided novel data about PM₁₀ chemical composition, its sources and its seasonal variability during the year, which can help the local government to define control strategies for the main emission sources during the most critical periods.

Global, Regional, and Megacity Trends in the Highest Temperature of the Year: Diagnostics and Evidence for Accelerating Trends

Trends in short-lived high-temperature extremes record a different dimension of change than the extensively studied annual and seasonal mean daily temperatures. They also have important socioeconomic, environmental, and human health implications. Here, we present analysis of the highest temperature of the year for approximately 9000 stations globally, focusing on quantifying spatially explicit exceedance probabilities during the recent 50- and 30-year periods. A global increase of 0.19°C per decade during the past 50 years (through 2015) accelerated to 0.25°C per decade during the last 30 years, a faster increase than in the mean annual temperature. Strong positive 30-year trends are detected in large regions of Eurasia and Australia with rates higher than 0.60°C per decade. In cities with more than 5 million inhabitants, where most heat-related fatalities occur, the average change is 0.33°C per decade, while some east Asia cities, Paris, Moscow, and Houston have experienced changes higher than 0.60°C per decade.

Metabolic heat production by human and animal populations in cities

Anthropogenic heating from building energy use, vehicle fuel consumption, and human metabolism is a key term in the urban energy budget equation. Heating from human metabolism, however, is often excluded from urban energy budgets because it is widely observed to be negligible. Few reports for low-latitude cities are available to support this observation, and no reports exist on the contribution of domestic animals to urban heat budgets. To provide a more comprehensive view of metabolic heating in cities, we quantified all terms of the anthropogenic heat budget at metropolitan scale for the world's 26 largest cities, using a top-down statistical approach. Results show that metabolic heat release from human populations in mid-latitude cities (e.g. London, Tokyo, New York) accounts for 4-8% of annual anthropogenic heating, compared to 10-45% in high-density tropical cities (e.g. Cairo, Dhaka, Kolkata). Heat release from animal populations amounts to <1% of anthropogenic heating in all cities. Heat flux density from human and animal metabolism combined is highest in Mumbai-the world's most densely populated megacity-at 6.5 W m^-2, surpassing heat production by electricity use in buildings (5.8 W m^-2) and fuel combustion in vehicles (3.9 W m^-2). These findings, along with recent output from global climate models, suggest that in the world's largest and most crowded cities, heat emissions from human metabolism alone can force measurable change in mean annual temperature at regional scale.

Trends of PM2.5 concentrations in China: A long term approach

The fast economic growth of China along the last two decades has created a strong impact on the environment. The occurrence of heavy haze pollution days is the most visible effect. Although many researchers have studied such problem, a high number of spatio-temporal limitations in the recent studies were identified. From our best knowledge the long trends of PM_2.5 concentrations were not fully investigated in China, in particular the year-to-year trends and the seasonal and daily cycles. Therefore, in this work the PM_2.5 concentrations collected from automatic monitors from five urban sites located in megacities with different climatic zones in China were analysed: Beijing (40°N), Chengdu (31°N), Guangzhou (23°N), Shanghai (31°N) and Shenyang (43°N). For an inter-comparison a meta-analysis was carried out. An evaluation conducted since 1999 demonstrates that PM_2.5 concentrations have been reduced until 2008, period which match with the occurrence of the Olympic Games. However, a seasonal analysis highlight that such decrease occurs mostly during warmer seasons than cold seasons. During winter PM_2.5 concentrations are typically 1.3 to 2.7 higher than in summer. The average daily cycle shows that the lowest and highest PM_2.5 concentrations often occurs in the afternoon and evening hours respectively. Such daily variations are mostly driven by the daily variation of the boundary layer depth and emissions. Although the PM_2.5 levels have showing signs of improvement, even during the warming season the values are still too high in comparison with the annual environmental standards of China (35 μg m^-3). Moreover, during cold seasons the north regions have values twice higher than this limit. Thus, to fulfil these standards the governmental mitigation measures need to be strongly reinforced in order to optimize the daily living energy consumption, primarily in the north regions of China and during the winter periods.

Effects of landscape composition and pattern on land surface temperature: An urban heat island study in the megacities of Southeast Asia

Due to its adverse impacts on urban ecological environment and the overall livability of cities, the urban heat island (UHI) phenomenon has become a major research focus in various interrelated fields, including urban climatology, urban ecology, urban planning, and urban geography. This study sought to examine the relationship between land surface temperature (LST) and the abundance and spatial pattern of impervious surface and green space in the metropolitan areas of Bangkok (Thailand), Jakarta (Indonesia), and Manila (Philippines). Landsat-8 OLI/TIRS data and various geospatial approaches, including urban-rural gradient, multiresolution grid-based, and spatial metrics-based techniques, were used to facilitate the analysis. We found a significant strong correlation between mean LST and the density of impervious surface (positive) and green space (negative) along the urban-rural gradients of the three cities, depicting a typical UHI profile. The correlation of impervious surface density with mean LST tends to increase in larger grids, whereas the correlation of green space density with mean LST tends to increase in smaller grids, indicating a stronger influence of impervious surface and green space on the variability of LST in larger and smaller areas, respectively. The size, shape complexity, and aggregation of the patches of impervious surface and green space also had significant relationships with mean LST, though aggregation had the most consistent strong correlation. On average, the mean LST of impervious surface is about 3°C higher than that of green space, highlighting the important role of green spaces in mitigating UHI effects, an important urban ecosystem service. We recommend that the density and spatial pattern of urban impervious surfaces and green spaces be considered in landscape and urban planning so that urban areas and cities can have healthier and more comfortable living urban environments.

Accumulation patterns of lipophilic organic contaminants in surface sediments and in economic important mussel and fish species from Jakarta Bay, Indonesia

Non-target screening analyses were conducted in order to identify a wide range of organic contaminants in sediment and animal tissue samples from Jakarta Bay. High concentrations of di-iso-propylnaphthalenes (DIPNs), linear alkylbenzenes (LABs) and polycyclic aromatic hydrocarbons (PAHs) were detected in all samples, whereas phenylmethoxynaphthalene (PMN), DDT and DDT metabolites (DDX) were detected at lower concentrations. In order to evaluate the uptake and accumulation by economic important mussel (Perna viridis) and fish species, contaminant patterns of DIPNs, LABs and PAHs in different compartments were compared. Different patterns of these contaminant groups were found in sediment and animal tissue samples, suggesting compound-specific accumulation and metabolism processes. Significantly higher concentrations of these three contaminant groups in mussel tissue as compared to fish tissue from Jakarta Bay were found. Because P. viridis is an important aquaculture species in Asia, this result is relevant for food safety.

First comprehensive screening of lipophilic organic contaminants in surface waters of the megacity Jakarta, Indonesia

Jakarta is an Indonesian coastal megacity with over 10 million inhabitants. The rivers flowing through the city receive enormous amounts of untreated wastewaters and discharge their pollutant loads into Jakarta Bay. We utilized a screening approach to identify those site-specific compounds that represent the major contamination of the cities' water resources, and detected a total number of 71 organic contaminants in Jakarta river water samples. Especially contaminants originating from municipal wastewater discharges were detected in high concentrations, including flame retardants, personal care products and pharmaceutical drugs. A flame retardant, a synthetic fragrance and caffeine were used as marker compounds to trace the riverine transport of municipal wastewaters into Jakarta Bay. These markers are also appropriate to trace municipal wastewater discharges to other tropical coastal ecosystems. This application is in particular useful to evaluate wastewater inputs from land-based sources to habitats which are sensitive to changing water quality, like coral reefs.

How Can Urban Policies Improve Air Quality and Help Mitigate Global Climate Change: a Systematic Mapping Review

Tackling climate change at the global level is central to a growing field of scientific research on topics such as environmental health, disease burden, and its resulting economic impacts. At the local level, cities constitute an important hub of atmospheric pollution due to the large amount of pollutants that they emit. As the world population shifts to urban centers, cities will increasingly concentrate more exposed populations. Yet, there is still significant progress to be made in understanding the contribution of urban pollutants other than CO2, such as vehicle emissions, to global climate change. It is therefore particularly important to study how local governments are managing urban air pollution. This paper presents an overview of local air pollution control policies and programs that aim to reduce air pollution levels in megacities. It also presents evidence measuring their efficacy. The paper argues that local air pollution policies are not only beneficial for cities but are also important for mitigating and adapting to global climate change. The results systematize several policy approaches used around the world and suggest the need for more in-depth cross-city studies with the potential to highlight best practices both locally and globally. Finally, it calls for the inclusion of a more human rights-based approach as a mean of guaranteeing of clean air for all and reducing factors that exacerbate climate change.

Environmental Impacts of China's Urbanization from 2000 to 2010 and Management Implications

Rapid urbanization in China during the first decade of the twenty first century has brought about profound environmental changes at citywide and regional scales. In this paper, we present a comprehensive set of indicators and put forward a new evaluation method for measuring environmental impacts of urbanization from 2000 to 2010. We compared these impacts among 286 cities in mainland China and found that the overall quantity of pollutant discharge decreased as cities became more economically developed during the years 2000-2010. However, larger and denser cities, and wealthier cities in the eastern part of China tended to have larger quantities of pollutant discharge, resource consumption, and changes in land use (i.e., expansion of the built environment). The discharge increase occurred despite these cities having increased their investment in pollution control and construction of municipal environmental infrastructure. The negative impact from the intensity of pollutant discharge (i.e., discharge per unit of economic output) was generally less in more developed cities, although this was not always the case. Some cities, such as resource-based cities and old industrial cities, had both larger quantities of pollutant discharge and greater pollution intensity compared to other types of cities, indicating that environmental impacts did not necessarily decrease with increasing urbanization. The results of this study provide a promising basis for decision-making to reduce the impacts for different types of cities in the decades to come.

Investigating dimensionality and measurement bias of DSM-5 alcohol use disorder in a representative sample of the largest metropolitan area in South America

BACKGROUND

Given the recent launch of a new diagnostic classification (DSM-5) for alcohol use disorders (AUD), we aimed to investigate its dimensionality and possible measurement bias in a non-U.S.

METHODS

The current analyses were restricted to 948 subjects who endorsed drinking at least one drink per week in the past year from a sample of 5037 individuals. Data came from São Paulo Megacity Project (which is part of World Mental Health Surveys) collected between 2005 and 2007. First, exploratory factor analysis (EFA) was carried out to test for the best dimensional structure for DSM-5-AUD criteria. Then, item response theory (IRT) was used to investigate the severity and discrimination properties of each criterion of DSM-5-AUD. Finally, differential criterion functioning (DCF) were investigated by socio-demographics (income, gender, age, employment status, marital status and education). All analyses were performed in Mplus software taking into account complex survey design features.

RESULTS

The best EFA model was a one-dimensional model. IRT results showed that the criteria "Time Spent" and "Given Up" have the highest discrimination and severity properties, while the criterion "Larger/Longer" had the lowest value of severity, but an average value of discrimination. Only female gender had DCF both at criterion- and factor-level, rendering measurement bias.

CONCLUSION

This study reinforces the existence of a DSM-5-AUD continuum in the largest metropolitan area of South America, including subgroups that had previously higher rates of alcohol use (lower educational/income levels). Lower DSM-5-AUD scores were found in women.