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“Lack of calibration of pollution-measuring instruments has been hampering efforts of the country’s pollution watchdog to come out with accurate data on air pollution. When Delhi experimented with car rationing (odd-even) schemes to tackle the problem of air pollution, people wondered why the different agencies showed different figures for emission level of pollutants in the capital. It had intrigued even policy-makers. But scientists at the National Physical Laboratory (NPL) of the CSIR knew that the answers to many such questions lay with pollution measuring instruments which were not calibrated to standardised form.

There was, in fact, no standardisation of such pollution-measuring instruments in India and therefore there was no calibration as per the standard norms considering different functional parameters of such equipment. As a result, even the national air quality index, being released everyday by theCentral Pollution Control Board (CPCB), does not give an absolutely correct picture of the level of pollution in different cities.

NPL has now asked the country’s central pollution watchdog -CPCB -and the pollution control boards of all states to calibrate their instruments with the standard fixed by it.The NPL director, Dinesh K Aswal, told TOI that the laboratory has recently developed and patented its own PM2.5 sampler – a first of its kind in India to provide accurate and traceable measurement facility – and asked the pollution control boards to go for calibrations. “Once all the pollution measuring instruments are calibrated to the standard fixed by the NPL, we would be able to get an accurate picture of the level of pollution. We have first developed it for PM2.5. Samplers for other pollutants will also be developed and patented in due course”, said Aswal on Wednesday.

The NPL has called the meeting of the CPCB and the State Pollution Control Boards (SPCBs) for sensitisation and training of their officials next month. Thereafter, all the pollution measuring instruments, used by these pollution watchdogs, will be calibrated as per the laboratory’s standard which is recognised by the world body. Once the process is formalised, all pollution measuring instruments used by different private agencies will also be required to be calibrated as per the NPL’s standard..” Times of India. Read it on

Air quality index doesn’t give you correct picture