Air pollution is contamination of the indoor or outdoor environment by any chemical, physical, or biological agent. It modifies the natural characteristics of the atmosphere.
PM 2.5 means particulate matter in the air – caused by motor exhaust or anything combustible – that is less than 2.5 micrometers.
Airborne particles are sometimes referred to as ‘particulate matter’ or ‘PM’. They include dust, dirt, soot, smoke, and liquid droplets. Various sources, both natural and human-related, directly emit some particles into the air
Natural sources include bushfires, dust storms, pollens, and sea spray.
Those related to human activity include motor vehicle emissions, industrial processes (eg electricity generation, incinerators, and stone crushing), unpaved roads, and wood heaters.
Particles can be classified based on their size, referred to as their ‘aerodynamic diameter’. ‘Coarse particles’ are those between 10 and 2.5 micrometres (µm) in diameter; ‘fine particles’ are smaller than 2.5 µm; and ‘ultrafine particles’ are smaller than 0.1 µm. Studies have linked exposure to particle pollution to several health problems including
respiratory illnesses (such as asthma and bronchitis) and cardiovascular disease.
INDIA’S STANDARD FOR LEVEL OF POLLUTION
India has set standards for what it thinks are appropriate warnings for a particular level of pollutant. Air Quality Index (AQI) helps in comparing pollution levels at a glance with a color code and a numerical value. In India, AQIs use the concentrations of pollutants like PM2.5 (fine, respirable particles), sulfur dioxide (SO2), nitrogen dioxide (NO2), and carbon monoxide (CO) to determine air quality.
There are six AQI categories, namely: Good, Satisfactory, Moderately polluted, Poor, Very poor and Severe.
The Index is centered around five chief pollutants – Particulate Matter with a diameter of less than 10 micro meters (PM10), Particulate Matter with a diameter of less than 2.5 micrometers (PM2.5), ozone (O3), Nitrogen Dioxide (NO2), and Carbon Monoxide (CO).
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