An Integrated Study of Air Pollutant Sources in the Delhi National Capital Region (NCR)

Lead Research Organisation: University of Birmingham
Department Name: Sch of Geography, Earth & Env Sciences


Delhi was rated the most polluted city in the world for ambient air pollution by the WHO in 2014. Some 46 million people live in and around Delhi - 18m in the city, and the remainder in the surrounding National Capital Region (NCR). Annual mean levels of particulate matter (PM), the most important air pollutant for health in Delhi, exceeded WHO guidelines by a factor of 15 during 2014, and are responsible for very substantial chronic and acute health impacts, with attendant economic costs. Development of effective strategies for improvement in air quality requires quantitative understanding of the sources, formation processes, regional budgets and chemical and physical nature of airborne particulate matter; however, such knowledge is not yet available.

ASAP-Delhi addresses this requirement: The project will provide a quantitative assessment of the sources, characteristics, abundance and formation processes for PM in Delhi and the surrounding NCR. The project is designed to address key science questions (below), with a philosophy of obtaining insights into pollutant sources and budgets from high quality direct observation - i.e. based upon measurement of the species actually present in the air at ground level within Delhi, without dependence upon other data. The project represents a focussed collaboration between leading researchers from the UK (Birmingham, Surrey) and India (IITD, NPL), who have a track record of successful joint collaboration and publications from previous funded air quality projects in Delhi.

ASAP-Delhi will (i) perform the most detailed physical and chemical characterisation of PM present in Delhi, and in the surrounding National Capital Region (NCR) to date; (ii) produce source profiles (chemical signatures) for the principal PM sources in Delhi; (iii) identify and quantify the contributions of different sources to the PM burden in Delhi (and the NCR) - for both PM mass concentration and particle number [with differing implications for health], by application of multiple, independent, established and novel receptor modelling approaches, such as chemical mass balance, radiocarbon, and number size distribution based source apportionment; (iv) estimate the impact of NCR emissions upon air quality in Delhi (key to effective regional air quality policy) and (v) evaluate a series of new hypotheses for the formation of PM during pollution episodes, essential for accurate model predictions of future PM levels.

We will address these objectives through a series of field observations, combining online measurements with state-of-the-science offline analyses, in Delhi (urban background locations - year round sampling combined with two "intensives"), the surrounding NCR (seasonal measurements at five sites) and a rural background location (150 km upwind). Our measurement strategy combines (i) established methodologies - to deliver a high quality, systematic, coherent measurement dataset, with a novel spatial distribution - and (ii) new state-of-the-science tools and analytical approaches. This provides a balance between international quality observations (in support of ASAP-Delhi and other programme components) and novel metrics, whilst also recognising the realities of fieldwork in such environments. ASAP-Delhi will draw upon results of other projects in the APHH India programme, and will provide the key observational insights in support of air quality model development, evaluation of human health impacts, and development of mitigation policies in the wider programme.

In addressing public health, policy and development issues, and providing a platform to enhance air pollution research in India, ASAP-Delhi addresses the ODA support categories of (i) people and (ii) research programmes, in addition to providing a step-change in understanding of the sources of PM in Delhi (the key insight required by policymakers).

Planned Impact

The key impact from ASAP-Delhi will be to deliver a step-change in understanding of the sources and processes forming of air pollutants in Delhi, providing science insight for policymakers to use in developing air pollution control measures. In conjunction with other projects within the Indian Megacity programme, this will lead to improved health and wellbeing for millions of people in Delhi - the ultimate beneficiaries.

We have identified three tiers of non-academic beneficiaries from the project, alongside the scientific / research community:

Tier 1: Stakeholders who will be direct beneficiaries of this project, with sustained engagement, e.g. the DPCC (Delhi Pollution Control Committee).

Tier 2: Wider stakeholders who have clear interests in the outcome of this project and the wider programme, and who may be directly engaged in the work, e.g. governmental departments such as the Central Road Research Institute (CRRI) and CPCB (Central Pollution Control Board).

Tier 3: Stakeholders who have a broader interest in the findings of the overall programme; for example, the media, WHO, the World Bank, private sector businesses in directly affected areas, and the general public.

Research Community: The project findings will be of direct relevance to researchers working in on air pollution issues - sources, processes and impacts - in Delhi and related environments.

They will benefit in the following ways:

Tier 1: The PM source apportionment results are essential for developing air pollution control strategies and will therefore provide direct insight for policy makers including the DPCC. In addition, the source apportionment and air pollutant process understanding will also indirectly benefit policy makers by constraining and improving predictive air quality models, which are the basis for developing long-term and short-term air pollution control strategies.

Tier 2: Air pollution control requires actions from other governmental departments such as those responsible for transportation. The results from ASAP-Delhi will provide direct assessment of the relative importance of different sectors to air pollution loading in Delhi and surrounding areas. This will help these stakeholders to identify potential policy actions to control air pollution in the most effective manner.

Tier 3: Delhi is the most polluted city in the world for ambient air quality (WHO, 2014). Thus, it serves as a natural laboratory to study air pollution on human health. Our results will benefit health effect studies within the programme by providing detailed physical and chemical characteristics of PM in Delhi. This will be of interest to Tier 3 stakeholders such as WHO which is keen to more accurately and precisely quantify air pollution impacts on human health. Environmental agencies elsewhere will benefit from this work via the overall programme in providing improved understanding of air pollution impacts on human health.

Ultimate beneficiaries - the general population of Delhi will benefit eventually from the contributions of ASAP-Delhi, and the overall programme, to identification of optimal air quality control strategies, leading to improved well being and health.

Steps to maximise impact with these beneficiaries are outlined in the ASAP-Delhi Pathways to Impact document, which will be delivered collaboratively with other projects in the overall APHH-India Programme.


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Description ASAP-Delhi will provide authoritative assessment of the sources, formation process, burden and characteristics of air pollutants in Delhi, and the influence of the surrounding NCR (National Capital Region), with a focus upon particulate matter as the pollutant with the greatest impact upon health, and a philosophy of deriving pollutant source, budget and behaviour insights from direct atmospheric observations. ASAP-Delhi is a self-contained component of the NERC-MRC-MoES-DBT programme Atmospheric Pollution and Human Health in an Indian Megacity, within which complementary observational / modelling / health / policy projects will be delivered.

At the time of writing (March 2022), the project field observations have been completed, and laboratory and data analyses are underway, alongside integration with other projects within the APHH-Delhi programme. Progress with this work has been significantly disrupted by Covid, due to lab and campus closures in the UK and India for a number of months. A final decision from NERC / UKRI regarding no-cost extension to match commitments from MoES on the Indian side is awaited.
Exploitation Route Future stakeholder engagement, with key policymakers such as CPCB, DPCC and National Task Force to inform air pollution mitigation measures.
Sectors Environment

Title Research data supporting " Interpretation of Wide Range Particulate Matter Size Distributions in Delhi" 
Type Of Material Database/Collection of data 
Year Produced 2021 
Provided To Others? Yes  
Description ASAP-Delhi: IITD 
Organisation Indian Institute of Technology Delhi
Country India 
Sector Academic/University 
PI Contribution Expertise in air pollutant source identification / source apportionment
Collaborator Contribution Access to measurement sites/expertise in Indian air pollution climatology, causes, variations.
Impact Project currently ongoing
Start Year 2016
Description ASAP-Delhi: NPL 
Organisation National Physical Laboratory, New Delhi, India
Country India 
Sector Academic/University 
PI Contribution Expertise in air pollutant source apportionment
Collaborator Contribution Access to measurement sites and analytical facilities; insight into meteorological conditions affecting air pollution episodes
Impact Project currently ongoing
Start Year 2016
Description APHH India - First Stakeholder Workshop 
Form Of Engagement Activity A formal working group, expert panel or dialogue
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact First 1-day stakeholder meeting for the APHH-India project, held in Delhi, May 2018. Attended by ca 40 external sector organisation representatives / stakeholders, to promote and help shape the APHH-India research projects.
Year(s) Of Engagement Activity 2018
Description APHH Programme Website 
Form Of Engagement Activity Engagement focused website, blog or social media channel
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact APHH-India programme-wide website
Year(s) Of Engagement Activity 2018
Description Media interviews following the Birmingham Clean Air Zone Implementation 
Form Of Engagement Activity A press release, press conference or response to a media enquiry/interview
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Media (as a channel to the public)
Results and Impact Clean Air Zone Launch - Communications Evaluation
On 1 June 2021, Birmingham City Council announced the launch of the city's Clean Air Zone. Working with professional services and academic colleagues, we used this as an opportunity to promote the world-leading clean air research, taking place across the University of Birmingham.
Communications Activity Total reach - 3,601,092

We contacted (and were contacted by) regional and national media outlets to provide expert comment on the introduction of the Clean Air Zone. Outputs include;
Date Outlet Media item Academic Reach
1 June 2021 5 News Birmingham launches 'clean air zone', but defers payments for the first 2 weeks
Professor Zongbo Shi 1,000,000
1 June 2021 ITV Central News Clean Air Zone Launch Professors William Bloss and Zongbo Shi 655,000
1 June 2021 Sky News Clean Air Zone Launch Professor Zongbo Shi 324,000
Year(s) Of Engagement Activity 2021