Whenever we talk of air
pollution, suspended particulate matter or PM as it is commonly referred to, is
generally taken as representative of the level of pollution. In all there are
eight air quality parameters, which are taken into consideration when the Air
Quality Index (AQI) is calculated: Suspended particulate matter (PM2.5 and
PM10), sulfur dioxide (SO2), ozone (O3), nitrogen oxides (NO2), carbon monoxide
(CO), ammonia (NH3) and lead (Pb).
Particulate matter consists of
a complex mixture of solid and liquid particles of organic and inorganic
substances suspended in the air. It is mainly made up of sulfates, nitrates,
ammonia, sodium chloride, black carbon, mineral dust and water and allergens
(fragments of pollen or mold spores).
When outdoor levels of
particulate matter are high, their levels also increase indoors.
Depending on the size, there
are three types of particulate matter: PM 10, PM 2.5 PM and PM 0.1.
·
PM 10 are particles with a diameter of 10 microns or less (coarse particles).
Sources include crushing or grinding operations and dust stirred up by vehicles
on roads.
·
PM 2.5 are particles with a diameter of 2.5 microns or less (fine particles).
·
PM 0.1 are particles with a diameter of 0.1 microns or less (ultra-fine
particles).
The sources of fine and
ultra-fine particles include motor vehicles, power plants, biomass burning,
agricultural burning, and industrial emissions. They remain suspended in
the air for longer periods of time than coarse particles and hence, are more
likely to be inhaled.
The size of the particles has
a direct association with their effect on health. PM 10 particles can penetrate
and remain deep inside the lungs, while PM 2.5 and PM 0.1 can penetrate the
lung barrier and enter the blood system. They have more health damaging effects
as they can affect all organs of the body. Fine particles (PM2.5) are the main
cause of reduced visibility (haze).
As per international
recommendations, both PM 10 and PM2.5 should be less than 40. For India, the
PM10 levels should be less than 100 and PM 2.5 levels should be less than 60.
The larger PM 10 particles can
irritate the eyes, nose and throat. PM10 mainly affects the respiratory system
and may precipitate an acute asthma attack and acute exacerbation of chronic
bronchitis or may cause other respiratory problems such as cough, wheeze.
The fine and ultra-fine
particles also affect the heart so they may trigger an acute cardiovascular
event such as heart attack or stroke or atrial fibrillation as they increase
the resting blood pressure due to sympathetic overactivity and cause
endothelial dysfunction and thickening of the blood.
PM 2.5 and PM 0.1 particles
also have a greater association with increased mortality due to heart disease.
Dr KK Aggarwal
Padma
Shri Awardee
President Elect Confederation of Medical
Associations in Asia and Oceania
(CMAAO)
Group
Editor-in-Chief IJCP Publications
President
Heart Care Foundation of India
Immediate Past National President IMA
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