What is Particulate Matter?
Particle pollution, also
called particulate matter or PM, consists of solid
and liquid particles made up of ash, metals, soot,
diesel exhaust, and chemicals. We divide particles
into two major groups based on size.
PM10: The coarse particles are between 2.5
and 10 micrometers (from about 25 to 100 times
thinner than a human hair). These particles are
called PM10 (we say "P M ten", which stands for
Particulate Matter up to 10 micrometers in size).
These particles cause less severe health effects
mostly in the upper respiratory tract. These consist
of smoke, dirt and dust from factories, farming and
roads as well as mold, spores and pollen. They are
made from crushing and grinding rocks and soil then
blown by wind.
PM2.5. The small particles are smaller than
2.5 micrometers (more than 100 times thinner than a
human hair). These particles are called PM2.5 (we
say "P M two point five", as in Particulate Matter
up to 2.5 micrometers in size). These consist of
toxic organic compounds and heavy metals. They are
made from automobile exhaust, burning garbage and
landfill, smelting and processing of metals.
Both PM2.5 and PM10 are measured in micro
Which of PM2.5 and PM10 is more
The smaller particles or PM2.5 are
lighter and go deeper into the lungs and cause
greater damage longer term. They also stay in
the air longer and travel farther. PM10 (big)
particles can stay in the air for minutes or hours
while PM2.5 (small) particles can stay in the air
for days or weeks. And travel? PM10 particles can
travel as little as a hundred yards or as much as 30
miles. PM2.5 particles go even farther; many
hundreds of miles.
As a result, even though we measure both PM2.5 and
PM10, we lay much greater stress on PM2.5 which is
the more harmful among the two.
If my monitor says that PM2.5 is 100. What does
that mean for my health?
The Indian Government has come up
with a definition of health impact for various
levels of PM2.5, PM10 and other pollutants such as
NO2, CO, SO2 etc. based on significant available
health research, as well as what is relevant to
Indian conditions in the form of Air Quality Index.
An Air Quality Index or AQI is an overall
scheme that transforms values of individual
pollutants such as PM2.5, PM10, SO2, CO etc. into a
single number or set of numbers that can then be
used to communicate the current levels of air
quality and their corresponding health impact
consistently across the entire country. The Indian
AQI system classifies pollution levels into
Good(0-50) to Severe(401-500) categories with health
impact varying from minimal to severe.
The break points of different pollutants for example
(0-30) is Good for PM2.5, (31-60) is Satisfactory
have been defined based on the effect of of these
pollutants on health. These breakpoints are then
mapped to the corresponding AQI ranges of (0-50) for
Good and (51-100) for Satisfactory. So a
PM2.5(ug/m3) level of 31 will be represented by
PM2.5 AQI of 51 which corresponds to Satisfactory.
It is important to note whether PM2.5 or PM10 data
on online websites is represented as AQI or ug/m3.
If the PM2.5 value is 100, then if it is represented
as AQI then it will fall in the 'Satisfactory'
category but if it is represented as ug/m3 then it
will fall under the 'Poor' category.
The table below provides the Indian AQI categories
and ranges corresponding to different values of
PM2.5 and PM10 and their resulting health impact for
your easy reference. Note this will differ if you
look at US AQI or Chinese AQI.
| AQI Category
| Health Impact
Minor Breathing discomfort to sensitive
Moderately polluted (101-200)
Breathing discomfort to asthma patents,
elderly and children.
Breathing discomfort to all
|Very poor (301-400)
||Respiratory illness on
|Health impact even on
light physical work. Serious impact on
people with heart/lung disease.