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The Central Pollution Control Board (CPCB) has revealed that Delhi’s air, along with that of nine other Indian cities, contains traces of toxic heavy metals such as copper, chromium, zinc and molybdenum. The data submitted to the National Green Tribunal (NGT) shows that these metals account for between 0.1 and 2.1% of the total particulate matter (PM10) in the air. The cities included in the assessment are Delhi, Jaipur, Bhopal, Lucknow, Ahmedabad, Nagpur, Kolkata, Bengaluru, Visakhapatnam and Chennai.
In Delhi, samples were collected during June and July from sites at Pitampura, Siri Fort, Janakpuri and Shahdara. The average PM10 concentration during this period was about 130 micrograms per cubic metre, more than twice the national standard of 60 micrograms per cubic metre. The CPCB’s analysis found copper levels of 55.13 nanograms per cubic metre, chromium at 12.25 nanograms, molybdenum at 0.91 nanograms and zinc at 243.5 nanograms per cubic metre in the capital’s air.
CPCB Points to Regulatory Gaps
The CPCB told the tribunal that India currently lacks national air quality standards for several of these heavy metals, including zinc, chromium, copper and molybdenum. While some countries, such as Canada, have established limits for specific metals, India has yet to define safe thresholds for their presence in ambient air. The board explained that these metals are usually attached to particulate matter, meaning that efforts to reduce overall PM concentrations would also lower heavy metal levels.
The findings highlight the ongoing need for comprehensive air quality management that goes beyond tracking particulate matter by mass alone. Without regulatory benchmarks, it becomes difficult to assess the exact health risks or enforce corrective measures. The absence of such standards also leaves a gap in long-term monitoring, especially for metals that pose potential neurological, cardiovascular or respiratory health threats.
Tracing the Source and Scale of Pollution
The CPCB report indicates that metals bound to airborne particles originate from a mix of industrial emissions, vehicular exhaust, and resuspended dust. These metals, once inhaled, can accumulate in human tissues and cause chronic health problems. Previous research has already shown that exposure to delicate particulate matter containing metals such as chromium and copper can lead to respiratory inflammation and other health complications.
An earlier CPCB study cited in the report found high levels of heavy metals in PM2.5 samples from East Delhi before the COVID-19 lockdown, with the Heavy Metal Exposure Index highest in that region. The index later shifted to Ludhiana, Punjab, suggesting that industrial activity and vehicular density strongly influence regional variations. The latest findings add weight to concerns that rapid urbanisation and industrial emissions are contributing not only to air pollution but also to the growing toxic load in the air.
Linking to the National Clean Air Programme
The National Clean Air Programme (NCAP), launched by the Indian government, aims to cut PM10 levels by up to 40% by 2025–26 compared to 2017–18 levels. The CPCB said that, since heavy metals are mostly found attached to particulate matter, the ongoing efforts to curb PM levels could also help reduce their presence. However, the agency did not specify whether dedicated monitoring of heavy metals will become part of the NCAP framework.
Experts believe that managing air pollution in Indian cities will require a detailed understanding of pollutant composition, rather than just the overall particulate load. Identifying metal-specific sources could help policymakers design targeted interventions, especially in urban areas with high levels of industrial and vehicular activity. The findings presented to the NGT offer a clearer picture of the chemical complexity of India’s urban air and the urgent need for policy attention to heavy metal contamination.
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Banner image: Photo by Laurentiu Morariu on Unsplash
