India largest emitter of SO2, contributing more than 15% of global anthropogenic SO2 emissions


Excerpts from the report “Global SO2 emission hotspot database: Ranking the world’s worst sources of SO2 pollution” written by Sunil Dahiya and Lauri Myllyvirta, and published by Greenpeace Environment Trust:

Annually, 4.2 million people die prematurely from ambient, outdoor air pollution alongside another 3.2 million due to indoor and household air pollution (2016) according to the World Health Organization (WHO). The same WHO report states that 91% of the world’s population lives in areas exceeding the WHO air quality guidelines. In contrast to improvements of household air quality since the 1990s, ambient air pollution stemming from increasing fossil fuel combustion remains a big problem throughout the world.

The World Bank recently estimated that “In 2013 exposure to ambient and household air pollution cost the world’s economy some $5.11 trillion in welfare losses. In terms of magnitude, welfare losses in South Asia and East Asia and the Pacific were the equivalent of 7.4 percent and 7.5 percent of the regional gross domestic product (GDP), respectively”.

Welfare losses due to air pollution continue to increase, mounting concern for countries across the world. Emissions of sulfur dioxide (SO2) are a significant contributor to air pollution. SO2 is released while burning materials that contain sulfur, which is found in all types of coal and oil across the world in varying proportions.

The health impact of SO2 derives both from direct exposure to SO2 and exposure to fine particulate matter5 (PM2.5) produced when SO2 reacts with other air pollutants to form sulfate particles. PM2. is the air pollutant with the largest public health impact because it is a cocktail of all different kinds of pollution ranging from heavy metals to secondary gaseous pollutants such as sulphates and nitrates.

These pollutants are so small that they can penetrate deeper into our organs and cells harming every organ in our body, causing everything from dementia and fertility problems to reduced intelligence as well as heart and lung disease. The greatest source of SO2 in the atmosphere is the burning of fossil fuels in power plants and other industrial facilities.

Smaller sources of SO2 emissions include industrial processes such as extracting metal from ore; natural sources such as volcanoes; and locomotives, ships and other vehicles and heavy equipment that burn fuel with a high sulfur content. It is estimated that SO2 commonly makes up >10% of the fine particles in China and India, often much more during heavy pollution episodes.

To tackle this problem adequately, it is important to understand both its extent and its causes. Where are pollution hotspots, what are their contributing sources, the history of their buildup and how do their emissions disperse over regions across the globe?


The NASA OMI satellite has been monitoring air quality from space since 2004 with high consistency. Its worldwide observation coverage enables us to identify pollution hotspots which are not listed in emission inventories. Furthermore, by comparing upwind and downwind SO2 levels, NASA has quantified emissions of large point sources and validated their results against in situ measurements in the U.S. and the European Union (EU).

We use their MEaSUREs SO2 source emission catalogue to identify countries, administrative domains and the point sources with the largest anthropogenic SO2 emissions. We refined this data set, by breaking down the sources of a hotspot’s emissions into several categories ie., coal, oil & gas and smelters (modified from NASA original classification). We also added details of smaller industries as well as the largest emission source in the region.

This way, we better represent the contributions of individual emitters within a cluster, rather than just that of the biggest. The names for hotspots were adapted from NASA database by us to represent the region as hotspots instead of just the biggest polluter in the region.

Data and Analysis

NASA OMI satellite data captured more than 500 major point sources of SO2 emissions across the globe including natural sources such as volcanoes. Excluding all natural sources from our analysis and only investigating anthropogenic sources of SO2, we found a close correlation of high SO2 emission levels within regions that have high fossil fuel consumption i.e., geographies with high coal burning, oil refining and combustion as well as smelters.

Sixty percent of the total emissions detected by the satellite are anthropogenic. Regions with high capacity of coal combustion for power generation and industries, smelters, oil and gas refining/combustion contributed 31%, 10% and 19% respectively. In many cases, the total emissions for a region cannot be attributed to an exact source because emissions from large sources may obscure those of other smaller nearby contributors. Therefore, in cases where multiple industries are present in the cluster, we take the largest sources as representing all other sources.

The Norilsk smelter site in Russia continues to be the largest anthropogenic SO2 emission hotspot in the world, followed by the Kriel area in Mpumalanga province of South Africa and Zagroz in Iran. Other places with high coal consumption or oil and gas refining and combustion such as Rabigh in Saudi Arabia and Singrauli in India have been catching up with the top three hotspots in the last decade and have increased their pollution dramatically.

This is mainly caused by expanding capacity of coal combustion and oil refining/consumption and in part due to slow implementation and uptake of stringent emission standards. Some countries, such as China, have enforced more stringent emission regulation for coal combustion and other industrial processes, leading to a decrease of SO2 emissions.

green1Geographical Regions

India: India is the largest emitter of SO2 in the world, contributing more than 15% of global anthropogenic SO2 emissions from NASA detected hotspots. The primary reason for India’s high emission output is the expansion of coalbased electricity generation over the past decade. The vast majority of plants in India lack flue-gas desulfurization technology to reduce their air pollution. Singrauli, Neyveli, Talcher, Jharsuguda, Korba, Kutch, Chennai, Ramagundam, Chandrapur and Koradi thermal power plants or clusters are the major emission hotspots in the country.

In India, there has been an increase of SO2 emissions at already existing hotspots as well as the emergence of new sites generating emissions across the country. In a first step to combat the pollution levels, the Ministry of Environment, Forest and Climate Change introduced, for the first time SO2 emission limits for coal-fired power plants in December 2015, but the deadline for the installation of flue-gas desulfurization (FGD) in power plants has been shifted from 2017 to 2022.

Russia: The Norilsk smelters in Russia are responsible for more than 50% of the total emissions tracked by NASA in the whole of Russia. At most other locations, there has been a small decrease of emissions over the past 15 years. Karabash, Orenburg, Kirovgrad, Ufa and Krasnouralsk are the other major SO2 hotspots in Russia, hosting smelters, gas refinery and coal combustion facilities for power and industries.

China: Having the largest coal-fired power generation capacity in the world, China was the biggest emitter for SO2 until about a decade ago. Since it started installing FGD systems across the electricity generation sector, air quality has substantially improved, while China still remains the third largest emitter in the world.

Mexico: Oil fields in the Gulf of Mexico are among the biggest hotspots in the world. Their emissions increased until 2016 before dropping for two consecutive years in 2017 and 2018. The other major SO2 emission hotspots in the country are at the Reforma refinery region, the Petacalco power plants region, and the refinery and power plant region around Tula, contributing to air pollution in nearby areas including in Mexico City.

South Africa: The Mpumalanga province in South Africa is not only the largest SO2 pollution hotspot in Africa but in 2017 and 2018, the cluster of mega power plants in Nkangala, including Duvha (3600 MW), Kendal (4000 MW) and Kriel (3000MW) coal power stations in Mpumalanga region ranked second in the world for anthropogenic SO2 emissions. There are 12 coalfired power stations in the province, located just 100-200 km from South Africa’s largest populated area, the Gauteng City region, posing a massive health concern. Power generation from these plants makes the Mpumalanga region the largest hotspot of SO2 emissions from power generation in the world.

Saudi Arabia: Saudi Arabia is the largest emitter of SO2 in the Middle East and North Africa (MENA) region. Within 120 km of the Makkah province, one of the most populated provinces in the country, there are large clusters of SO2 emission sources including Rabigh, Shaiba and Jeddah. Oil power plants and oil refineries in these locations emitted 59% of SO2 among Saudi Arabia’s total emissions in 2018. Other major sources are power plants and refineries in Jubail, Yanbu, Al Hofuf, Riyad, Uthmaniyah, Buraydah.

Europe: In Europe, three countries stand out for their SO2 emissions – Ukraine, Serbia and Bulgaria. All three are in the list of largest 20 SO2 emitters in the world. Without exception coal based power plants are the main source of high SO2 emissions in all three countries. Bulgaria is the only EU country on the list. In 2017 the EU adopted stricter SO2 emission limits for coal-fired power plants but Bulgaria is opposing these new rules and continues to permit operational power plants to emit more than the law allows and is also seeking exemptions from the rules, instead of taking steps to phase out coal.

Australia: The largest SO2 pollution hotspots in Australia are in Mount Isa, Queensland, a complex of mining operations with lead & copper smelters and in the Latrobe Valley, Victoria, a group of coal-fired power plants located 100-150 kilometres away from Australia’s second largest metropolitan centre, Melbourne. Despite globally significant emissions of SO2, there are currently no national or statewide limits on power station emissions of SO2 in any Australian jurisdiction, placing Australia’s system of pollution regulation behind countries including China, U.S. and the EU.

Major Polluting Sectors

Coal Combustion: More than 51% of total anthropogenic SO2 emissions are emitted in regions of high coal consumption for power generation and industries. Coal combustion for power generation is the major emission source in these regions, with smaller contributions from oil refineries/consumption, smelters and others. The NASA MEaSUREs data, highlights that coal-based power plants are the major emission sector in India, China, Indonesia, Thailand, Mexico, South Africa, Bulgaria and Australia.

In recent years many states and regions including China, India, South Africa and Indonesia have imposed or enhanced their emission standards for SO2 and started deploying desulfurization technology. However, regulations and their enforcement differ between countries and in most places the emission standards are still far too weak to improve air quality effectively. This difference in emission regulation and varying efficiencies of SO2 pollution control results in varying emissions from the same capacity of power plants across different regions.

Oil and Gas Refining/Power Generation: Oil refining and gas industries/power generation in Mexico, Saudi Arabia, Iran, United Arab Emirates (UAE), Russia, Uzbekistan and Venezuela pump large quantities of SO2 emissions into the atmosphere. Hotspots detected by the NASA OMI instrument show the regions where oil refining and gas facilities are present. The OMI instrument captured more than 40 regions with oil and gas refining clusters.

Mexico hosts some of the highest SO2 hotspots resulting from oil refining and gas processing clusters, including, Cantrell, Reforma and Salina Cruz. Other significant emission hotspots resulting from oil refining/combustion were found in MENA region.

Smelters: Metal smelters across the world are usually located in clusters around metal mines where raw metal ore can be extracted. The operation of these smelters, especially those without proper pollution control devices emits SO2 into the atmosphere and can be detected by the NASA OMI instrument. Smelters are the principal contributor to SO2 in many of the biggest detected hotspots. Emission levels for these hotspots are shown in Figure 6. Norilsk in Russia remains the biggest emitting region worldwide, followed by Sarcheshmeh in Iran, Ilo in Peru, Nicaro in Cuba, Almalyk in Uzbekistan and Karabash in Russia.

Way Forward

The burning of fossil fuels such as coal, oil and gas is the largest source of anthropogenic emissions of SO2 resulting in poor air quality and premature deaths across the world. By identifying SO2 emission hotspots in this briefing, we show the scale of air pollution across regions and where dramatic change needs to be implemented for human wellbeing.

Air pollution and the climate emergency share the same solutions. Emission hotspot regions across the world owe it to citizens to stop investing in fossil fuels and shift to safer, more sustainable sources of energy while reducing the impact of existing polluting facilities by adopting stricter emission standards.

Click HERE for full report

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