Beyond Delhi: The growing nitrogen dioxide crisis in Indian cities

When we think of air pollution in India, we often picture Delhi under a thick layer of smog. But new findings by Greenpeace India challenge this narrow focus. However, their report, on nitrogen dioxide pollution shatters this geographic fixation, directing attention to seven of India’s major cities—Bengaluru, Chennai, Hyderabad, Jaipur, Kolkata, Mumbai, and Pune—where dangerously high nitrogen dioxide (NO₂) levels are posing severe and escalating public health threats.

Nitrogen dioxide is a near-invisible toxic gas released primarily through the burning of fossil fuels—chiefly from vehicles, power plants, and industrial facilities. Compared to particulate matter, nitrogen dioxide has seldom been considered in conversations around pollution in India. The report titled “Beyond North India – Tackling NO₂ pollution and health risks in seven major Indian cities” draws from national air quality monitoring data, European satellite observations, and global emissions inventories and paints a sobering picture.

Why nitrogen dioxide deserves attention    

Exposure to nitrogen dioxide is linked to a litany of health issues, including asthma, reduced lung function, cardiovascular diseases, and premature death. Children are particularly vulnerable: over 21,000 disability-adjusted life years (DALYs) in India were lost due to nitrogen dioxide exposure in 2021 alone. The World Health Organization (WHO) recommends an annual average exposure limit of just 10 µg/m³, but most Indian cities operate under national standards four times higher—40 µg/m³—last updated in 2009. This regulatory lag has left cities and citizens exposed to preventable harm.

The seven-city scan: A tale of worsening air

Greenpeace India’s analysis of 81 monitoring stations across seven cities found that 89% exceeded the WHO’s annual nitrogen dioxide guideline in 2023. Despite the critical risk posed by roadside pollution, only 12 stations were near major roads. Pune recorded the highest annual average at 37 µg/m³, with Jaipur close behind. Both cities breached daily WHO limits for most of the year. Mumbai, with 24 monitors, saw 22 exceed guidelines, with Mazgaon logging breaches on over 70% of days. Satellite data shows worsening citywide pollution trends in Kolkata, Hyderabad, Chennai, and Bengaluru, regardless of localised improvements.

Public health impacts: Children at risk    

The health toll of nitrogen dioxide is alarming, with thousands of paediatric asthma cases linked to exposure—3,970 in Mumbai, 3,210 in Kolkata, and over 2,400 in Hyderabad and Jaipur. These numbers translate to long-term respiratory health risks for children. Worryingly, schools located near high-pollution monitors highlight the exposure of young students to toxic air, underscoring an urgent need for targeted interventions in school zones.

Transportation: The principal villain

Road transport ranks among the top three sources of nitrogen dioxide emissions in all cities studied. In Jaipur and Hyderabad, it accounts for 25% of total emissions. Bengaluru and Chennai are also heavily affected by vehicular pollution. While India’s Bharat Stage emission standards aim to curb pollution, unintended side effects of emission control technologies have sometimes worsened NOx emissions. This situation highlights the need for a more integrated mobility strategy that reduces dependency on fossil-fuelled vehicles.

Monitoring gaps and weak regulation      

India’s current nitrogen dioxide standards—unchanged since 2009—are significantly weaker than WHO guidelines, leaving many urban populations unprotected. Moreover, the limited presence of roadside monitors leaves critical gaps in pollution data. Cities like Kolkata have no designated roadside stations, impeding effective exposure assessment and air quality planning.

A satellite’s view from above

TROPOMI satellite data confirms a worsening nitrogen dioxide trend in all seven cities over the past five years, corroborating ground-level observations. Despite the rollout of BS-IV and BS-VI norms, cities like Jaipur, Mumbai, and Pune show statistically significant increases in nitrogen dioxide levels, indicating that policy and technology alone are insufficient without systemic urban planning reforms.

Policy pathways forward: Clearing the air with decisive action

To confront the escalating nitrogen dioxide crisis, a reactive approach will no longer suffice. India must adopt a proactive, science-led, and health-centred air quality governance strategy. Greenpeace India lays out a set of targeted policy recommendations, which, if implemented urgently and in coordination across sectors, can reverse the rising nitrogen dioxide trends in urban India. Here’s how each can be strengthened:

• Strengthen national standards to match WHO guidelines: India’s outdated nitrogen dioxide limits—four times higher than WHO recommendations—leave vulnerable populations unprotected. CPCB should collaborate with ICMR to revise National Ambient Air Quality Standards (NAAQS) using current health research, adopting WHO’s phased targets to balance ambition and feasibility. India’s current nitrogen dioxide limits—40 µg/m³ annually and 80 µg/m³ for 24-hour averages—are nearly four times more lenient than WHO’s health-based guidelines. These outdated norms fail to protect vulnerable populations, especially children, the elderly, and those with pre-existing respiratory conditions.

• Improve monitoring, especially at roadside hotspots: Only 12 of 81 monitors are near major roads, creating blind spots in areas with the highest exposure. The government must expand roadside monitoring, deploy mobile sensors in underserved zones, and ensure real-time public access to pollution data.

• Invest in public and non-motorised transport: Private vehicle growth, coupled with stagnant public transit, fuels nitrogen dioxide emissions. India must invest in clean buses, cycling, and pedestrian infrastructure, and adopt policies like congestion pricing to shift travel habits toward sustainable modes.

• Adopt regional air-shed management plans: Pollution spreads across cities and regions, requiring coordinated strategies. Regional air-shed authorities should harmonise emission data, transport policies, and energy plans across urban clusters like Mumbai-Pune.

• Embed health in pollution policy: Air pollution is a public health crisis. Health ministries must co-lead air quality programs, track pollution-related illnesses, mandate health impact assessments for infrastructure projects, and integrate alerts into health schemes like Ayushman Bharat.

• Enforce emission standards with real-world testing: Despite progressive Bharat Stage norms, implementation gaps persist. On-road emission testing, higher penalties, and swift rollout of BS-VII aligned with Euro 7 standards are essential, along with promoting green fuels like bio-CNG and hydrogen.

• Empower cities and communities: Urban local bodies need funding and training to manage air quality. Support should include fiscal devolution, capacity-building for staff, and citizen science initiatives enabling residents—especially youth—to track and act on pollution locally.

• Mainstream green urban design: Cities should integrate pollution-absorbing features—green belts, urban forests, vegetative walls—into planning. Zoning must protect sensitive sites like schools from high-pollution areas and align with Smart Cities and AMRUT initiatives.

Citation: Greenpeace India. (2024, December 4). Beyond North India – Tackling No. 2 pollution and health risks in seven major Indian cities. https://www.greenpeace.org/static/planet4-india-stateless/2024/12/ec05b58e-24-12-05-a4-gpi-beyond-north-india-report-e3.3.pdf