second Intermediate School

1. Air pollution

2. Air pollution is the introduction into the
atmosphere of chemicals, particulate
matter, or biological materials that cause
discomfort, disease, or death to humans,
damage other living organisms such as
food crops, or damage the natural
environment or built environment .
A substance in the air that can cause harm to humans and the environment is 
known as an air pollutant. Pollutants can be in the form of solid particles, liquid
droplets, or gases. In addition, they may be natural or man-made
Pollutants can be classified as primary or secondary. Usually, primary pollutants 
are directly emitted from a process, such as ash from a volcanic eruption, the
carbon monoxide gas from a motor vehicle exhaust or sulfur dioxide released from
factories. Secondary pollutants are not emitted directly. Rather, they form in the air
when primary pollutants react or interact. An important example of a secondary
pollutant is ground level ozone — one of the many secondary pollutants that make
up photochemical smog. Some pollutants may be both primary and secondary: that
is, they are both emitted directly and formed from other primary pollutants.

3. When people think about air pollution, they
usually think about smog, acid rain, CFC's,
and other forms of outdoor air pollution. But
did you know that air pollution also can exist
inside homes and other buildings? It can,
and every year, the health of many people is
affected by chemical substances present in
the air within buildings .
Air pollution occurs when the air contains gases, dust, fumes or odour in
harmful amounts. That is, amounts which could be harmful to the health or
comfort of humans and animals or which could cause damage to plants and
materials .
The substances that cause air pollution are called pollutants. Pollutants that
are pumped into our atmosphere and directly pollute the air are called
primary pollutants. Primary pollutant examples include carbon monoxide from
car exhausts and sulfur dioxide from the combustion of coal .

4. Further pollution can arise if primary pollutants in the atmosphere undergo chemical
reactions. The resulting compounds are called secondary pollutants. Photochemical
smog is an example of this.
In the days before the proliferation of large cities and industry, nature's own systems
kept the air fairly clean. Wind mixed and dispersed the gases, rain washed the dust
and other easily dissolved substances to the ground and plants absorbed carbon
dioxide and replaced it with oxygen.
With increasing urbanisation and industrialisation, humans started to release more
wastes into the atmosphere than nature could cope with.
Since then, more pollution has been added to the air by industrial, commercial and
domestic sources. As these sources are usually found in major cities, the gases that
are produced are usually concentrated in the air around them. The adverse effects of
air pollution were graphically illustrated in London in 1952 when, in just a few days, an
estimated 4000 people died from effects of fine particle pollution.
Air pollutants mainly occur as a result of gaseous discharges from industry and motor
vehicles. There are also natural sources such as wind-blown dust and smoke from
fires.

5. Al-bandari
Lujain
Atheer
Reema
School: Second Intermediate School
Yanbu Albahar