A groundbreaking study from the Indian Institute of Technology Delhi (IIT Delhi) has quantified the profound health crisis linked to sulfur dioxide (SO2) emissions from coal-fired power plants (CFPPs) across India. Researchers at the institute's Centre for Atmospheric Sciences have demonstrated that fully mitigating these emissions could prevent over 124,000 premature deaths each year, primarily by slashing levels of fine particulate matter known as PM2.5. This research not only underscores the urgent need for emission controls but also highlights IIT Delhi's pivotal role in advancing environmental science through innovative modeling and satellite data analysis.

The study, published in the prestigious npj Clean Air journal—a Nature portfolio publication—marks one of the first comprehensive national assessments linking specific CFPP-SO2 sources to widespread air pollution and mortality. Led by Subhadeep Ghosh and corresponding author Sagnik Dey, alongside collaborators Sajeev Philip and Debajit Sarkar from IIT Delhi, and international experts from Environment and Climate Change Canada, it employs state-of-the-art techniques to map pollution hotspots and project health benefits. As India grapples with rising coal dependency for energy security, this work from a premier engineering institution calls for evidence-based policy shifts to protect public health.

SO2 from Coal Plants: The Invisible Killer Transforming into PM2.5

Sulfur dioxide, a colorless gas released during coal combustion, doesn't just irritate the lungs— it undergoes chemical reactions in the atmosphere to form sulfate aerosols, a key component of PM2.5. These tiny particles, smaller than 2.5 micrometers, penetrate deep into the respiratory system and bloodstream, triggering cardiovascular diseases, respiratory illnesses, and even premature death. In India, where coal powers about 70 percent of electricity generation, CFPPs are prolific SO2 emitters, contributing significantly to the nation's air quality woes.

Unlike direct pollutants, SO2's secondary impacts amplify over time and distance, affecting regions far from plants. The IIT Delhi team notes that Indian coal's variable sulfur content exacerbates this, with emissions rising 30 percent in 2023 alone to over 5 million kilotons annually. Without controls like flue gas desulfurization (FGD) systems—which capture up to 95 percent of SO2—these emissions continue to form hazardous PM2.5, disproportionately burdening densely populated areas.

Innovative Methodology: Satellite Data Meets Advanced Chemical Modeling

What sets this IIT Delhi research apart is its rigorous methodology. The team developed a novel satellite-derived catalog of CFPP-SO2 emissions using data from Ozone Monitoring Instrument (OMI), Ozone Mapping and Profiler Suite (OMPS), and TROPOspheric Monitoring Instrument (TROPOMI) sensors. Detecting plumes above 8-40 kilotons per year, they excluded smaller sources for precision.

These emissions fed into the GEOS-Chem chemical transport model at high resolution (0.25° x 0.3125°), simulating 2021 meteorology. Paired runs—with and without CFPP-SO2—isolated contributions to PM2.5 and SO2. Validation against ground monitors (OpenAQ PM2.5 correlation R=0.68; Central Pollution Control Board SO2 R=0.38 in hotspots) ensured accuracy. Population exposure was weighted using National Family Health Survey-5 (NFHS-5) demographics, applying Global Burden of Disease (GBD) risk ratios for adults over 25. This fusion of space-based observations and computational chemistry exemplifies IIT Delhi's prowess in interdisciplinary environmental research.

Staggering Findings: 124,564 Preventable Deaths Annually

The numbers are stark: complete SO2 mitigation from CFPPs could reduce national PM2.5 exposure by 0.3 to 12 micrograms per cubic meter yearly, averting 124,564 premature deaths (95% uncertainty interval: 103,388–145,740). Of these, 14,777 stem from cardiovascular disease and 8,476 from respiratory causes. CFPP-SO2 accounts for 5.82 percent of total PM2.5-related mortality, rising to 11.86 percent for cardiovascular and 6.8 percent for respiratory outcomes.

State-wise, Maharashtra tops with 18,663 avoidable all-cause deaths, followed by Tamil Nadu (18,417) and Karnataka (11,817). Central and eastern states like Chhattisgarh and Odisha see the largest air quality gains, with PM2.5 drops exceeding 8 µg/m³. For deeper insights, explore the full study here.

Seasonal analysis reveals winter peaks due to stagnant meteorology, amplifying plant contributions. This granular data empowers states to target interventions effectively.

Pollution Hotspots: Mapping the Crisis Across India

Spatial patterns reveal a south-to-north gradient: southern and central peninsular regions benefit most, with PM2.5 reductions up to 12 µg/m³ near clusters in Chhattisgarh and Odisha. The Indo-Gangetic Plain (IGP) and northeast show smaller gains (<2 µg/m³), but population density amplifies absolute impacts.

Urban-rural divides persist, with cities within 50 km of plants facing 10 times higher SO2. Maharashtra's industrial belt and Tamil Nadu's coastal plants exemplify high-emission zones. IIT Delhi's maps highlight 10-30 percent CFPP contributions to local PM2.5 in these areas, urging phased FGD rollouts. Coverage of the study's maps in media like Indian Express has sparked national discourse.

Environmental Equity: Protecting India's Most Vulnerable

Beyond aggregates, the study reveals disparities favoring equity. Poorer and middle-class groups gain 4.19-4.22 µg/m³ urban PM2.5 reductions versus 3.85-4.07 for the rich. Other Backward Classes (OBC), Scheduled Castes (SC), and Scheduled Tribes (ST) benefit more (4.09-4.22 µg/m³) than General caste (3.74-3.99). Males see slight urban edges over females.

Rural deprived subgroups stand to avoid hundreds of deaths annually per category. NFHS-5 integration underscores how pollution exacerbates caste and wealth divides, positioning SO2 controls as a social justice tool. IIT Delhi's demographic modeling sets a benchmark for inclusive environmental research in India.

The Compelling Economic Argument for Immediate Action

Installing FGD systems—wet limestone scrubbers capturing 87-95 percent SO2—isn't just feasible; it's profitable. Prior estimates suggest a 2015 full rollout could yield $6 billion net benefits via value of statistical life (VSL) savings. Health costs from PM2.5 alone hit INR 10,000 crore yearly; mitigation offsets tariff hikes.

China's FGD success reduced SO2 80 percent post-2014, proving scalability. For India, with 87 GW planned coal capacity, delays compound risks. Experts like Manoj Kumar from CREA affirm: health gains eclipse expenses, especially amid expanding capacity.

Policy Context: Navigating Relaxed Norms and Calls for Reversal

India's 2015 norms mandated FGDs, but 2025 exemptions spared 79 percent of units, citing low-sulfur coal and tall stacks. Emissions surged 30 percent in 2023. Critics, including The Wire's analysis here, decry this as life-endangering, urging reversal.

Debajit Sarkar emphasizes state-specific policies: “Winter contributions peak; hotspots need priority.” IIT Delhi bridges academia-policy gaps, influencing NCAP and enforcement.

IIT Delhi's Centre for Atmospheric Sciences: Leading the Charge

Housed in IIT Delhi—one of India's top engineering institutes—the Centre for Atmospheric Sciences (CAS) pioneers aerosol-climate interactions, air quality forecasting, and health linkages. Faculty like Sagnik Dey, with dual IIT-Kanpur PhD and Harvard postdoc, drive global-impact research. Collaborations with NASA, NASA, and Canadian agencies amplify reach.

CAS alumni pursue PhDs at MIT, ETH Zurich, or join ISRO, CPCB. This study exemplifies IITs' shift to societal challenges, blending engineering with public health.

Implications for Research and Innovation in Indian Higher Education

IIT Delhi's work inspires peers like IIT Bombay's heatwave models and IISc Bengaluru's emissions inventories. NEP 2020 boosts interdisciplinary centers; funding via DST-SERB, MoEFCC sustains. Satellite tech democratizes data, enabling undergrad projects on local pollution.

Challenges: Brain drain, funding gaps. Yet, successes position IITs as policy influencers, fostering startups in clean tech.

Career Opportunities in Atmospheric and Environmental Research

For aspiring researchers, IIT Delhi's MSc/PhD in Atmospheric Sciences offer hands-on satellite analysis, modeling. Roles at CPCB, TERI, or international orgs abound; salaries INR 8-15 lakh starting. Skills in Python, GEOS-Chem, remote sensing are gold. Programs like fully funded PhDs abound.

Industry: FGD firms, renewables. Global demand surges post-COP.

Photo by Zoshua Colah on Unsplash

Looking Ahead: A Cleaner Future Through Science and Action

IIT Delhi's study galvanizes action: enforce norms, expand FGDs, monitor via satellites. Universities must scale equity-focused research. For India—balancing energy and health—this blueprint promises lives saved, air reclaimed. As Sagnik Dey notes, precise quantification enables targeted wins.