On the face of it, it’s good news. India’s infamous air pollution has shown a significant decline across almost all states, according to a new three-year government-backed report known as SAANS – the Satellite-Based Monitoring of Ambient PM2.5 At National Scale for Air Quality Management. 

But there appears to be little decline during the winter months when pollution levels are at their worst, one of the report’s authors told Health Policy Watch – and the government has yet to release the full report with all the data covering three years from 2019-2022.

However, the summary report shows that PM 2.5 levels (fine particles) across rural and urban regions have plateaued over the last six years and are demonstrating a consistent decline. In addition, it is the first time rural air pollution is being systematically mapped.

The report made headlines because it showed a particularly huge drop in the most polluted states (see Table 2). The authors elected to monitor PM 2.5, as this category of microscopic pollutant can penetrate deep into the lungs and even enter the circulatory system, affecting other organs and systems. In 2017, about 670,000 deaths were attributed to this pollutant alone; in 2019, 1.67 million deaths – or over 3 deaths a minute – were linked to air pollution. 

Delhi has consistently remained the most polluted state, with an average PM 2.5 level of almost 104 micrograms/cubic metre, 20 times the safe limit guideline by the World Health Organization (WHO), for the last six years. 

Table 1: PM 2.5 in urban areas. The top 4 most polluted states have remained the same for the last six years. 

Uttar Pradesh (UP), the most populated state, saw a fall in PM 2.5 of close to 40% in 2022 over 2017. In Delhi and Haryana, the decline was about 20%. This data was released in a summary and the full report will be released once cleared by top pollution control officials. 

However, a closer look reveals the falls are more modest when PM 2.5 levels in 2022 are compared to the average of the previous five years, that is 2017 to 2021. 

In Bihar, the fall is just 0.3% compared to 17% reported over the year. In Delhi and Haryana, the fall is about 10% rather than 20%. However, the fall remains substantial in UP at about 26%. 

Table 2: Changes in PM 2.5 levels in India’s four most polluted states. 

The more pressing question is whether pollution has fallen substantially during the peak pollution months of October to January when pollution has been thick enough to close schools and cancel flights, thick enough to be tasted. PM 2.5 levels have hit 250-300 micrograms and more, that is, 50-60 times the WHO’s safe limit. 

One of the report’s authors, Professor Sagnik Dey of the Centre for Atmospheric Sciences at the Indian Institute of Technology Delhi, told Health Policy Watch that the October to January situation “has not changed much.” 

In fact, the annual decline is mostly because of the improvement in the summertime when there are better conditions for the dispersion of polluted air – stronger winds and a higher mixed layer height.

A telling map of daily pollution over 20 years used in the report shows just how bad these months are in India.

Better and more effective reporting

But the data in the report is significant in other ways. It is perhaps the first time the government has supported such extensive satellite-based monitoring of air quality. 

The authors say the technology has improved and there is a high correlation between this data and that from the official network of ground sensors, which is more accurate but also expensive.

Crucially, the new satellite-based data fills in a major gap in air quality monitoring in rural areas. There is negligible rural coverage by ground-based sensors. 

Interestingly, the satellite data shows that there is little difference in concentration levels between urban and rural areas and the declines are also similar. The sources of ambient pollution of course may differ – vehicular and industrial pollution are high in urban areas whereas household sources were found to be the largest contributor to ambient PM2.5 in rural India. 

Gas cylinder roll-out eases rural pollution

However, Dey suggests that rural air quality most likely improved from better penetration of liquified petroleum gas (LPG) under the government’s Ujjwala scheme to provide free gas cylinders, particularly to the rural poor. 

High PM 2.5 in rural areas is significantly attributable to the wide use of solid fuel for cooking, heating and even lighting, according to the report’s press release.

The report has also mapped air sheds, which offers an important understanding of how pollution spreads across a region regardless of political boundaries. 

This supports an argument for the central government to adopt a still more proactive and wider role to cut air pollution, as it may be easier for one centre to navigate across different airsheds rather than many states. But for effective action, that is to reduce or eliminate sources of pollution, satellite data will not be enough. A large network of ground-based sensors will not only be more accurate but reflect the nuances as well as the sources of pollution. 

The government has upped its target for cutting air pollution to 40% by 2026. At first glance, it may seem it’s on target. But the fine print of the SAANS report (‘breath’ in Hindi) does not suggest that. 

Image Credits: Wikipedia, Source http://www.saans.co.in/home.html.