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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 O 3 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 PM 10 , PM 2.5 and NO 2 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 O 3 of ~19% was observed for Delhi. A slight increase in O 3 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 O 3 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 O 3 . Results from ground-level observations in Delhi showed that concentrations of PM 10 , PM 2.5 and NO 2 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 O 3 , 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 O 3 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.

Environmental monitoring in middle- and low-income countries is hampered by many factors which include enactment and enforcement of legislations; deficiencies in environmental data reporting and documentation; inconsistent, incomplete and unverifiable data; a lack of access to data; and technical expertise. This paper describes the processes undertaken and the major challenges encountered in the construction of the first Niger Delta Emission Inventory (NDEI) for criteria air pollutants and CO 2 released from the anthropogenic activities in the region. This study focused on using publicly available government and research data. The NDEI has been designed to provide a Geographic Information System-based component of an air quality and carbon management framework. The NDEI infrastructure was designed and constructed at 1-, 10- and 20-km grid resolutions for point, line and area sources using industry standard processes and emission factors derived from activities similar to those in the Niger Delta. Due to inadequate, incomplete, potentially inaccurate and unavailable data, the infrastructure was populated with data based on a series of best possible assumptions for key emission sources. This produces outputs with variable levels of certainty, which also highlights the critical challenges in the estimation of emissions from a developing country. However, the infrastructure is functional and has the ability to produce spatially resolved emission estimates.

An assessment of the reliability of the Scanning Imaging Absorption Spectrometer for Atmospheric Cartography (SCIAMACHY) satellite sensor measurements to interpolate tropospheric concentrations of carbon monoxide considering the low-latitude climate of the Niger Delta region in Nigeria was conducted. Monthly SCIAMACHY carbon monoxide (CO) column measurements from January 2,003 to December 2005 were interpolated using ordinary kriging technique. The spatio-temporal variations observed in the reliability were based on proximity to the Atlantic Ocean, seasonal variations in the intensities of rainfall and relative humidity, the presence of dust particles from the Sahara desert, industrialization in Southwest Nigeria and biomass burning during the dry season in Northern Nigeria. Spatial reliabilities of 74 and 42 % are observed for the inland and coastal areas, respectively. Temporally, average reliability of 61 and 55 % occur during the dry and wet seasons, respectively. Reliability in the inland and coastal areas was 72 and 38 % during the wet season, and 75 and 46 % during the dry season, respectively. Based on the results, the WFM-DOAS SCIAMACHY CO data product used for this study is therefore relevant in the assessment of CO concentrations in developing countries within the low latitudes that could not afford monitoring infrastructure due to the required high costs. Although the SCIAMACHY sensor is no longer available, it provided cost-effective, reliable and accessible data that could support air quality assessment in developing countries.

The emission and dispersal of bioaerosols from open-air commercial composting facilities continues to be contentious. A meta-dataset enumerating cultivable microorganism emission and downwind concentrations is not yet available. A dataset derived from repeated and replicated field studies over a period of two years at two commercial composting facilities is presented. The data characterises patterns in Aspergillus fumigatus, actinomycetes, Gram-negative bacteria and endotoxin emission and downwind concentrations. For all bioaerosols, compost agitation activities had a significant impact on concentrations; levels were variable up to 600 m downwind from site. Bioaerosols declined rapidly from source and exhibited a secondary peak 100-150 m from site boundary. All bioaerosols were found downwind from site in elevated concentrations. Compared to those found 100 m upwind, levels were significantly higher at 180 m downwind for A. fumigatus; at 300-400 m for actinomycetes and Gram negative bacteria, and at 100 m for endotoxins. Periodically, elevated concentrations could be found for all bioaerosols at distances further downwind. The evidence provided by this data set provides operators and regulators of facilities with reliable data to inform the location, risk assessment and bioaerosol sampling strategies of commercial composting facilities., (Copyright © 2011 Elsevier GmbH. All rights reserved.)

Air quality is managed in Great Britain via an effects-based, risk management process designed to provide a dynamic solution to public health issues associated with elevated concentrations of seven specified air pollutants. This paper is concerned with an examination and evaluation of the process of Local Air Quality Management (LAQM) in Great Britain from the late 1980s to date as a risk management process. The statutory basis of LAQM process is provided by the Environment Act 1995. The Act provides a framework in which national and local actions are required to identify and remediate areas of poor air quality. Within this framework, the implementation of the process at national and local levels is considered, leading to an identification and assessment of risks in the formulation and implementation of air quality management policy and practice. Local Authorities began the process of Review and Assessment in 1999 and the first round of the process concluded in 2001. Following this, some 129 Local Authorities declared one or more Air Quality Management Areas (AQMAs). The Review and Assessment elements of the framework were subjected to an evaluation in 2001 and the essential elements of it were confirmed as fit for purpose. The evaluation led to a confirmation of the process of LAQM but also a simplification based on the experience of Round 1. Now, a two step process is required comprising of an Updating and Screening Assessment and, where a risk of exceeding an Air Quality Objective (AQO) is identified, a Detailed Assessment follows. The Government has identified a time scale for Review and Assessment through to 2010 and also introduced the requirement of a regular Progress Report in order that a Local Authority is able to address routine matters of air quality management. The risks inherent in epidemiological or scientific uncertainty are factored into the LAQM process at an early stage of the process and, by identifying the risks and subjecting them to regular review, the process provides a 'level playing field' across spatial and temporal scales. Whilst the process of LAQM described in this paper has been developed for Great Britain, the generic elements of the process are applicable to other countries challenged by air pollution problems which require both national and local action to resolve them.

Data for concentrations of PM(10) and gaseous pollutants from sites in the UK Automatic Urban and Rural Network have been examined during periods of elevated concentrations of PM(10). The ratios of concentrations of PM(10) to those of the other pollutants were used to determine the most probable source of the additional particles. The hypothesis is that because the concentrations of PM(10) were divided by those of the other pollutants, the ratio should decrease when PM(10) and the other pollutants have a common source. Conversely, the ratio should increase when the sources are different. During episodes where road traffic was the most probable source of the additional particles, the ratios of concentrations of PM(10) to carbon monoxide and oxides of nitrogen did decrease, but the comparable ratios for sulphur dioxide and ozone increased. In contrast, during episodes known to have been caused by construction activity, all these ratios increased. This is taken to show that the basic hypothesis is valid. For prolonged episodes, it was possible to use data averaged over the total duration of the episode for the purposes of source identification. For sporadic construction, or other short-duration episodes, it was necessary to use time series data. The data have also been used to calculate the differences between hourly average concentrations of pollutants measured during episodes and long-term hourly average concentrations. These have been used to model the additional PM(10) during air pollution episodes associated with construction activities and road traffic emissions. This confirms the lack of relationship between PM(10) and other pollutants during construction works. During episodes arising from road traffic emissions, there was good agreement between measured and modelled additional concentrations of PM(10) when an appropriate factor, F, related to the contribution of road traffic emissions to PM(10) at different site types was applied. The values used were 0.2 (Suburban), 0.3 (Urban Background/Urban Centre), and 0.5 (Roadside), representing 20%, 30%, and 50% contributions from road traffic, respectively.

In 1997, the UK government instigated the practice of Local Air Quality Management (LAQM) in the UK. This process is based on local authorities undertaking Review and Assessments of air quality within their areas. The first round of Review and Assessments have now been completed and represents the most extensive and coordinated analysis of air pollution ever undertaken in the UK, and probably in Europe. This paper takes a broad look at the outcomes of this process so far and identifies some of the key areas where lessons have/can be learnt both about patterns of air pollution in the UK and about the framework for investigating these that has been implemented under the LAQM regime. The process has led to a much higher number of local authorities finding problems with air pollution than initially expected. It has also challenged many assumptions about the significance of various pollutants and their sources.

Over the past 4 years, local government in the UK has undertaken a process of scientific review and assessment of air quality, which has culminated in a suite of designated air quality management areas (AQMAs) in over 120 of the 403 local authorities in England (including London), Scotland and Wales. Methods to identify specific pollution hot-spots have involved the use of advanced and complex air-quality dispersion modelling and monitoring techniques, and the UK government has provided guidance on both the general and technical methods for undertaking local air quality review and assessments. Approaches to implementing UK air quality policy, through the local air quality management (LAQM) process (Air Quality Strategy 2000) has not been uniform across the UK, as an inevitable consequence of non-prescriptive guidelines. This has led to a variety of outcomes with respect to how different tools and techniques have been applied, the interpretation of scientific uncertainty and the application of caution. A technique to appraise the scientific approaches undertaken by local government and to survey local government officers involved in the LAQM process have been devised, and a conceptual model proposed to identify the main influences in the process of determining AQMAs. Modelling tools used and the consideration of modelling uncertainty, error and model inputs have played a significant role in AQMA decision-making in the majority of local authorities declaring AQMAs in the UK.

Estimates of emissions of SO2, NOx, HCl and NH3 have been made for a densely populated region of the UK, the North-West of England, using data on power generation, incinerator plant capacity, fuel usage and animal and human population statistics. The spatial distributions of SO2 and NOx emissions are quite different, reflecting their different source strengths. The emissions from motor vehicles make up 52% of the NOx emissions from the North-West of England, whilst those from fossil-fuel-fired power stations make up 20%. The emissions of fossil-fuel-fired power stations make up 58% of SO2 emissions from the North-West. A large fossil-fuel-fired power station is the largest known point source for emissions of SO2, NOx and HCl. The largest contribution to NH3 emissions in the North-West is from cattle. Humans may contribute some NH3 to overall emissions but there is considerable uncertainty as to how much is emitted and what fraction of this is deposited within buildings. The uncertainties in the methodologies used are high-lighted and, where possible, recommendations are made as to how future emissions estimates might be improved. Potential reductions in emissions of SO2, NOx and HCl are discussed under basic scenarios of planned power station closures in the area and the compliance of the electricity generation industry with the European Community Directive on Large Combustion Plants.