موضوع
عن تلوث الهواء بالانجليزي قصير
موضوع عن تلوث الهواء بالانجليزي قصير
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Air
pollution ... not just in the air
Be in a
traffic jam, forced to breathe the exhaust of hundreds of vehicles, we observe
the black smoke spewed by factory chimneys or the horizon disappears hidden by
the smog of a hot day summer, the air pollution jumps our eyes ... and lungs.
But it can be much more insidious.
Air
pollution knows no boundaries. She travels briskly beyond countries, continents
and seas. Pollutants such as fine particles can travel thousands of
kilometers1. Thus, up to 50% of the human activity mercury deposited each year
in North America would come from other continents, in particular coal-fired
plants from China and India2. The airborne deposit is now the primary source of
mercury in Canada's lakes, soil and vegetation3.
Of course,
pollution can reach us by the air we breathe, but also by the contact on our
skin. Polluted air can contaminate everything with which it comes in contact:
fruits and vegetables as well as water and soil and, indirectly, food products
(plants, animals, fish) that will have fed on it.
Finally, it
should be known that pollutants in the air in minute quantities can be
concentrated as they move up the food chain. For example, if there is mercury
in the air, it can settle on water and be absorbed by small fish. As larger
fish eat smaller fish, the concentration of mercury increases as this
persistent pollutant accumulates in living organisms. Finally, when eating fish
contaminated with mercury, we may actually be victims of air pollution!
ABC of air
pollutants
top
Air
pollutants that are harmful to health are in the form of gases and respirable
particles.
Four gases
are the main contributors to pollution4,5:
ozone (O3)
nitrogen
dioxide (NO2)
sulfur
dioxide (SO2)
carbon
monoxide (CO)
Added to
these are other chemical pollutants such as heavy metals and volatile organic
compounds (VOCs) that include harmful products such as benzene and polycyclic
aromatic hydrocarbons (PAHs).
Respirable
particles (also called fine or ultrafine particles) refer to a heterogeneous
mixture of solid and liquid particles suspended in the air. They are classified
in two categories according to their size rather than their composition. The
smaller they are, the more they can be toxic because they penetrate deeper into
the respiratory system and can even reach the cardiovascular system. They are
commonly called PM, the abbreviation of the English term particulate matter.
PM10 (less
than 10 micrometers in diameter). Note that a human hair is 50 to 150
micrometers in diameter.
PM2.5 (less
than 2.5 micrometers) the most toxic.
According to
the experts, it is relatively difficult to know which pollutant in particular
may be responsible for a specific health problem6. Most of the time,
pollutants, regardless of their origin, are in the form of a cocktail composed
of many elements that act synergistically. Thus, epidemiological studies often
focus on the different adverse effects of "combined" pollution. The
intensity of this pollution is generally estimated by evaluating the
concentration of one or two of the main pollutants, which then serve as
markers, rather than systematically measuring each element.
Pollutants:
where are they?
top
Surface
Ozone or Ozone Layer?
Surface
ozone is a toxic pollutant. It should not be confused with the famous ozone
layer that protects us from the sun's rays. Ground-level ozone is formed when
nitrogen oxides and volatile organic compounds from vehicles and industries are
transformed by solar radiation and heat. Ozone, with respirable particles, is
one of the main components of smog that has a harmful effect on health.
The vast
majority of pollutants, gases or particulates come from the use of fossil fuels
(oil, natural gas and coal), which alone account for about 80% of global energy
needs. These fuels are mainly used for transportation, industry, heating and in
thermal power generation plants. Most of them are concentrated in urban
areas7,8. It should also be noted that in several large cities, wood burning is
a very important source of air pollution.
