Heavy metals in PM 2.5 samples from Delhi classrooms: Greenpeace

A report released Thursday showed the samples collected for around 24 hours from inside the classrooms had “alarming levels” of heavy metal presence on days when PM 2.5 concentrations were higher than the prescribed levels.

Monitors were installed inside the classrooms to assess levels of PM 2.5, and when indoor air quality was about five times above the Indian safety limits, an average of around 293 micrograms per cubic metre, the samples were tested for chemical composition. Greenpeace India said these samples had high levels of chemicals like Arsenic, Cadmium, Lead and Nickel which have been associated with several health hazards including cancer. “Eleven samples of airborne particulates that had been collected on cellulose acetate filters using an active personal particulate monitor were sent to the Greenpeace Research Laboratories from Greenpeace India on November 16, 2015,” states the report.

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Scientists at DPCC, however, claimed the results of this study could not be correlated to WHO standards of heavy metals in PM 2.5, as the levels defined by WHO and the Indian government were based on annual averages. “The standards as prescribed for some of these metals are based on annual average data. That has been compared to spot monitoring at a specific time or day only. This can give a skewed picture of exposure levels if you are comparing them to annual average standards,” said a senior scientist.