Air pollution has become one of the most pressing problems India is reeling under. In 2018, a World Health Organization (WHO) study found that fourteen of the twenty world’s most polluted cities belonged to India. The poor air quality that citizens are forced to breath, especially in heavily polluted cities, has a detrimental impact on their health and well-being. We have recently observed increasing cases of declaration of public health emergencies, flight cancellations, school closures and the subsequent political acrimony. Almost two million mortalities and a heavy loss in agriculture were attributed to poor air quality in India in 2017. The 2018 World Bank report, estimated that the damage cost of outdoor air pollution in India was about 2-4% of the total GDP. Factors such as vehicular emissions; crop burning; generation of dust, particularly from construction sites; depleting tree covers; and poor waste management, all have contributed towards the declining air quality. Many of these are critically harmful for human health, as well as the larger ecosystem we live in.
While quantification of all the air pollutants has not yet been feasible on a global scale, eminent international institutions like the WHO have tried to quantify and monitor air pollution by considering a certain set of air pollution indicators. The two main types of standards concerned with air pollution control are air quality and emission standards.
Air quality standards are legal limits placed on levels of air pollutants in the ambient air during a given period of time. They characterise the allowable level of a pollutant or class of pollutants in the atmosphere and thus define the amount of exposure permitted to the population and ecological systems. Emission standards establish permitted emission levels for specific groups of emitters and require that all members of these groups emit no more than these permitted emission levels. They are used to control the emissions from industrial or community sources and can be further classified into: mobile and stationary sources standards.
Emissions from various sources interact with meteorological conditions and get dispersed in the atmosphere. Therefore, they can be used, with appropriate mathematical models, to determine the degree of overall control necessary to meet ambient air quality standards.
Since air pollution is caused by multiple sources, has trans-boundary or regional effects, and is impacted by physical-chemical processes in the atmosphere, detailed scientific studies like source apportionment studies are required for its understanding. These studies are required for identification of major sources of air pollution and their contribution to the ambient air pollution of a region, in order to arrive at sector specific strategies for control. By understanding the source contributions, appropriate control measures targeting those sources can be designed.
For instance, the Indo-Gangetic plains, known to be one of the most fertile lands in the world, has emerged as a hot spot of air pollution, especially for Ozone. Elevated ozone concentration at the surface level has found to have negative impacts on crop productivity. This is crucial for the Indian region as the country’s economy and food security depend strongly on its agricultural productivity. The tropospheric chemistry over this region is constantly intensifying as a result of rapid increase in the regional anthropogenic emissions. Together with this, the intense tropical solar radiation and the ample availability of water vapour result in elevated surface ozone levels, imposing a threat to the food security in this region. Such impacts are expected to be further enhanced with feedback from climate warming on ozone formation in the future.
This knowledge, along with a source apportionment study of the emissions can help us design strategies to combat the rising risk of ozone pollution in a scientific and hence effective manner.
The Government of India has started to take steps to ameliorate air pollution with a target of 20-30% reduction in pollution levels across 102 non-attainment cities [an area considered to have air quality worse than the National Ambient Air Quality Standards] across the country by 2024. The National Clean Air Programme (NCAP) has been rolled out as a scheme that will arm the States and the Centre with a framework to achieve these targets over the next five years, with base year as 2019. However, challenges remain – there is little clarity on mechanisms for funding the activities of the Programme, and lack of a suitable legal framework that may dilute its effectiveness. Further, the absence of sector wise and city level targets are missing. The lack of suitable deterrents in the event of non-achievement targets beyond the scope of the National Green Tribunal’s actions also hampers the Programme. Moreover, the Programme does not necessarily see the correlations of air pollution with other kinds of potential issues like climate change – aerosols are known to have possible impacts in short term climate on specific regions. This could have given the Programme stronger grounds for implementation, seeing how it could help with the climate change mitigation efforts.
The problem of air pollution has become complex over the years due to increase in the number and intensity of the sources e.g., vehicular exhaust, industries, road re-suspension, construction activities etc. Detailed scientific studies are required for identification of major sources of air pollution and their contribution to the ambient air quality of a region. These assessments have proven to be very effective in devising appropriate strategies and policies for improvement of air quality.
As per a study conducted by TERI in 2018, Industries and Residential sectors are the prominent ones which contribute significantly to PM2.5 concentrations, followed by transport, power and open burning. Transport sector has higher contributions at the urban centres, while open agricultural burning is more prominent in specific seasons (late October- early November). The study also suggested sector specific interventions e.g. introduction and enforcement of new SO2/NOx emission standard, fuel switch, higher penetration of electric vehicles, increased LPG penetration etc. which can reduce air pollutant concentrations at regional scale in India.
Based on the interventions future scenario analysis has also been carried out. In this regard, possible future growth scenarios have been prepared for different years, which take into account the growth trajectories in various sectors and also the policies and interventions, which have already been notified for control of air pollution. Strategies that could provide significant air quality benefits have also been identified, with the aim to reduce the ambient air pollution. What is needed now is a synergy between various sources and industries, in order to effectively implement these suggestions and strategies. The air quality management plan should be prepared to achieve these targets in a timely fashion through reviews of interim targets on a regular basis.
