Today the problem of air pollution has become
so important that there is a need for timely
information about changes in the air pollution
level in the cities.
We need a method to make people understand
the quality of air as the technical method is not
understandable by all. This is where the API
comes in picture.
An Air pollution Index can be defined as a scheme that transforms the
(weighted) values of individual air pollution related parameters into single
number or set of numbers.
This gives us an equation which transforms the parameter values by means of
a numerical manipulation into amore simple and precise form as shown in
Use of Air Pollution Indices
● It helps in informing the public about air pollution levels in a particular area.
● It helps in comparing air pollution levels in different cities
● It may be used for development of a system for avoidance or management of a severe episode of air
Short-term indices Long-term indices
Types of Indices
Informs the public about daily
changes in the air pollution level.
Commonly used by the local and
state air pollution agencies.
Evaluate changes in air quality
over periods of several years or
Helpful in assessing the
effectiveness of enforcement
Air Pollution Parameters
Generally the parameters used for calculating the air pollution index are
suspended particulate matter (SPM), sulphur dioxide (SO2), carbon monoxide
(CO), nitrogen dioxide (NO2), photochemical oxidant (principally ozone O3)
'Visibility' can also be taken into consideration while determining the air
Criteria for a Standardized Index
1. Easily understood by the public
2. Include major pollutants
3. Calculated in a simple manner
4. Rest on a reasonable scientific basis
5. Consistent with perceived air pollution levels
6. Spatially meaningful
7. Exhibit day-to-day variation
8. Relate to ambient air quality standards and goals
9. Relate to episode criteria
10. Can be forecast a day in advance (if possible)
Determination of Index
We try to relate the existing pollution levels of various pollutants to their
ambient air quality standards, with the standard being assumed as the
reference base line for each pollutant and then converting the concentration
of pollutants into a percentage of the standard. The Air Pollution Index is then
obtained by adding the percentages for the several pollutants considered.
The average of the sum of the ratios of three major pollutant concentrations
to their respective air quality standards is obtained. The average is then
multiplied by 100 to get the index.
Air pollution index is calculated from five sub-indices. Each sub-index is
obtained by assigning sub-index values for particular ranges of pollutant
In the fourth method, known as the maximum type, only one pollutant index
(the highest one) among the several pollutants is reported.
In the fifth method, only two common pollutants i.e., particulate matter and
sulphur dioxide are taken into account while calculating the air pollution index.
In the sixth method, only one major pollutant, e.g., ozone concentration is
taken as the basis for reporting the Air Pollution Index.
Air pollution indices are very useful as they indicate day-to-day changes in air
quality. Also they provide an indication of the Nation's progress towards
cleaner and it facilitates comparison of air pollution problems in different
CREDITS: This presentation template was created by Slidesgo,
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1. Air pollution by M N Rao and H V N Rao
2. Internet sources