AIR_how do we know that it is polluted
Time to learn about the AQI, and why it matters to your and all your people's lives.
It would have been enough if all we had to worry about was these PM particles. But as we have found, there are many more pollutants. There is ozone. There is sulfur dioxide. There is nitrogen dioxide. There is carbon monoxide. To take all these into account, almost all governments have an index called the Air Quality Index (AQI), which gives us an overall idea of how bad/good the air is, and where. To make sure it is understood better, every condition (say, ‘moderate’, or, ‘poor’) has a related color code. In fact, India has its own color coded AQI, courtesy the CPCB (Central Pollution Control Board). It has been designed to measure lead and ammonia levels too, along with the above parameters. All this information, based on individual importance of each parameter, is compiled, and presto! You have the AQI!
As of 2014, according to the CPCB’s own report, 573 stations were manually operated (which involves a lag of reporting the pollutants, and less pollutants itself being measured), while only around 40 were automatic monitoring stations (real time, and more pollutant levels checked ) [The CPCB Report, available here]
First, we have the website showing the National AQI levels, courtesy the CPCB. Have a look.
Funnily enough, the numbers don’t match with those reported by AQICN. The AQICN uses all locally available information to report on air quality around the globe. Our Air Report numbers came from there.
Notwithstanding that, our air quality standards are apparently more strict than those of the USA [AQICN]
Why the difference, you may wonder?
Keep in mind that temperature, pressure, humidity and wind influence the air quality. For example, on Diwali, the wind speed was low, and the particulate matter was also unable to disperse. That played a big role in worsening the conditions. Also, there is a difference in reporting standards:
Closer examination reveals that data on ozone pollution furnished by Central Pollution Control Board gives the annual average of ozone concentration, while the National Ambient Air Quality Standards prescribes a 100 µg/m3 norm for 8-hour average concentration.
While air pollution data is being sourced from a number of sources, there is still some uncertainty:
In a research paper titled, A global catalogue of large SO2 sources and emissions derived from the Ozone Monitoring Instrument, Vitali E. Fioletov (from the Air Quality Research Division, Environment Canada) and his coauthors acknowledge the total degree of uncertainty for the data at 55% to 67%.