Zinc, copper, chromium — What Delhi is breathing, even in residential areas

Samples collected from Shahdara, Pitampura, Janakpuri, and Sirifort confirm the presence of these metals across both residential and mixed-use areas, indicating widespread contamination across the Capital.

The CPCB’s submission clarifies that these metals are “bound to particulate matter (PM₁₀)” and that their “percentage fraction in PM₁₀ was found to range between 0.1 and 2.1 per cent.”

The agency added that “reduction in PM concentrations should in turn lower the levels of these parameters in ambient air”.

Among the 10 cities monitored include Jaipur, Bhopal, Lucknow, Ahmedabad, Delhi, Nagpur, Kolkata, Bengaluru, Visakhapatnam, and Chennai. Out of these, Ahmedabad showed the highest mean zinc concentration at 1,774.3 ng/m³, followed by Bhopal (547.5 ng/m³), Nagpur (411.4 ng/m³), and Lucknow (264.3 ng/m³).

Delhi ranked fifth with an average zinc concentration of 243.5 ng/m³, while Kolkata, Bengaluru, and Chennai recorded significantly lower levels. Visakhapatnam’s zinc data were discarded due to measurement ambiguity reported by the Andhra Pradesh Pollution Control Board.

For Delhi, the mean PM₁₀ concentration was 130.06 micrograms per cubic metre, nearly double the National Ambient Air Quality Standard (60 µg/m³).

The readings from the four Delhi sites showed consistent contamination: at Shahdara, copper reached 132 ng/m³; at Pitampura, zinc peaked at 342 ng/m³; and at Janakpuri and Sirifort, both copper and chromium were continuously detected even in residential zones.

The CPCB, in its affidavit, stated: “Ambient air quality monitoring with respect to particulate matter (PM₁₀) and metals under consideration, namely Zinc, Chromium, Copper, and Molybdenum, was undertaken to assess the current levels of these parameters in the ambient air.”

Delhi showed the second highest levels of Copper, after Bengaluru which was at 63.77 ng/m³. The Capital was also found with the third highest Chromium in the air, at 12.25 ng/m³ it was only lower than Bhopal’s at 114.57ng/m³ and Chennai 15.43 ng/m³. Similarly, it also had the third highest values for Molybdenum after Chennai at 1.55 ng/m³ and Ahmedabad at 0.94 ng/m³.