Introduction
A groundbreaking study by the Bose Institute, Kolkata, has revealed that the toxicity of PM2.5 pollutants — measured by their oxidative stress potential — increases steeply beyond a specific threshold, irrespective of concentration. This finding goes beyond conventional Air Quality Index (AQI) frameworks, which assess air pollution solely on concentration levels. It demands a paradigm shift in urban air quality governance and regulatory standards in India.
Governance Challenges
- Concentration-centric Regulations: India’s current ambient air quality standards, governed by the National Ambient Air Quality Standards (NAAQS) under the Air (Prevention and Control of Pollution) Act, 1981, focus on annual and 24-hour mean concentrations (e.g., 60 µg/m³ daily for PM2.5). This fails to account for toxicological variability in pollutant composition across cities.
- Lack of Chemical Composition Monitoring: AQI, as managed by the Central Pollution Control Board (CPCB), is based on six pollutants but does not include oxidative potential or chemical source apportionment in its real-time updates. Most monitoring stations are ill-equipped to detect the varying toxicity of emissions from sources like biomass burning, industrial pollutants, or vehicular emissions.
- Institutional Fragmentation: Air quality governance is divided among multiple agencies — CPCB, State Pollution Control Boards, urban local bodies — without a unified, data-driven toxicity evaluation protocol. This fragmentation limits coordination, especially in megacities like Kolkata, Delhi, or Mumbai.
- Inadequate Emergency Response Frameworks: Unlike the Graded Response Action Plan (GRAP) in Delhi, most Indian cities lack city-specific emergency protocols based on pollution spikes. Even GRAP does not consider toxicity thresholds as triggers for action.
Policy Implications
- Toxicity-Based Standards and Thresholds: The study identifies a toxicity threshold of ~70 µg/m³ in Kolkata, beyond which oxidative stress on the human body increases sharply. This necessitates evolving toxicity-weighted AQI indices and city-specific toxicological baselines, enabling more accurate public health risk assessments.
- Targeted Pollution Source Control: Toxicity is found to be higher from sources like biomass or solid waste burning, compared to vehicular emissions. This demands localized pollution control policies, focusing on chemical-specific emission curbs — e.g., banning open garbage burning or promoting clean biomass technologies.
- Health-Centric Air Governance: Existing standards must align with health outcomes rather than uniform concentration levels. Public health warnings, hospital preparedness, and urban planning must integrate toxicity thresholds to prevent respiratory or cardiovascular crises during toxic spikes.
- Environmental Justice Dimensions: Vulnerable populations — urban poor, informal workers, children, and the elderly — face greater exposure and lower resilience to oxidative stress. Ignoring toxicity in AQI overlooks this inequality. Toxicity-sensitive planning can enable more equitable environmental health policies.
- Technological and Institutional Investments: India needs to scale up real-time chemical speciation and oxidative potential monitoring. Investing in high-resolution sensors, urban toxicology labs, and integrating toxicity mapping into Smart Cities and AMRUT schemes can institutionalize data-led governance.
Conclusion
The findings of this new study underscore the urgent need to evolve from a concentration-based AQI regime to a toxicity-informed, health-prioritized air quality framework. This shift is essential for protecting public health, ensuring environmental justice, and enabling targeted interventions tailored to the diverse pollution profiles of Indian cities. Regulatory modernization, public awareness, and scientific capacity-building must converge to achieve breathable urban air in India’s growth trajectory.
