Pathanamthitta is the second least polluted town in India in terms of air pollution, next to Tezpur in Assam, according to the figures of the Central Pollution Control Board for 2018.
Alexander George, District Environmental Engineer, said the Ambient Air Monitoring System installed in Pathanamthitta town showed a very moderate presence of particulate matter (PM) of 35 to 40 microgram per cubic metre.
Particulate matter
The particulate matter is the sum of all solid and liquid particles suspended in the air, many of which are hazardous. This complex mixture contains, for instance, dust, pollen, soot, smoke, and liquid droplets.
In Pathanamthitta, the PCB had measured the Suspended Particulate Matter (SPM) called PM10, meaning particulate matter with diameter less than 10 micrometre (also called micron). One micron is 1/1000000 of a metre.
PM10 is the weight of particles in micrograms whose size is less than 10 micro metre. Particles in that range easily find their way into the respiratory system.
Instrument
Mr. George said an instrument named High Volume Sampler was used for measuring the concentration of particulate matter. It was operated round the clock.
“The instrument sucks in a known volume of air which is made to pass through a pre-weighed filter paper. After eight hours the filter paper is removed and weighed. In 24 hours, three filter papers are is used.
The difference between the final and the initial weight of the filter paper divided by the volume of air pumped gives the PM10 value in microgram per cubic metre,” he said.
The measurement is taken for 10 days every month in towns and all State pollution control boards submit the yearly average to the Central Pollution Control Board, which publishes the final list.
Mr. George said the permissible limits for PM10 is 100 micro gram per cubic metre. The average PM10 value in Pathanamthitta is 35-40 microgram per cubic metre and at Thiruvalla, 45 microgram per cubic metre.
As per the PCB findings, Pathanamthitta is comparatively cleaner since it has fewer industrial activities. The vehicular flow too is comparatively less.
Source
The source of particulate matter generation in Pathanamthitta includes automobile exhaust, open burning of waste, agricultural and mining activities, the PCB engineer said.
The values also depended on the weather condition. It may drop considerably during rainy season and shoot up during the winter season.
