Air Pollution

 Air Pollution

 

Definition:

 

The presence of gases, liquids and solids in the atmosphere in high enough levels that can harm different components of the environment including humans, living organisms and materials is called air pollution.

 

Types of Air Pollutants:

 

Air pollutants can be classified into two categories.

 

 (1) Primary Air Pollutants 

 

 (2) Secondary Air Pollutants

 

1- Primary Air Pollutants:

 

The harmful chemicals which are emitted directly into the air from natural and anthropogenic sources are called primary air pollutants.

 

Examples: Carbon monoxide (CO), Carbon dioxide (CO2), Nitric oxide or Nitrogen monoxide (NO), Nitrogen dioxide (NO2) and Sulfur dioxide (SO2).

 

2- Secondary Air Pollutants:

 

   Some primary air pollutants undergo reactions with one another and other air pollutants in the atmosphere to form new harmful chemicals. These pollutants are called secondary air pollutants.

 

Examples: Sulfur trioxide (SO3), Sulfuric acid (H2SO4), Nitric acid (HNO3) Ozone  (O3), Hydrogen peroxide  (H2O2), Peroxyacetyl  nitrates (PANs), Nitrate (NO3-), Sulfate (SO42−) salts.

 

Criteria air pollutants:

 

The term criteria air pollutants originated with the US 1970 Clean Air Act. That law required EPA to set standards (National Ambient Air Quality Standards, NAAQS) to protect human health and welfare from pollutants in ambient air. Before setting standards, the EPA had to identify the most serious pollutants. To do so it used specific criteria (characteristics of the pollutants, and their potential health and welfare effects).

 

The six pollutants that the EPA identified account for the large majority of air pollution, both in the United States and worldwide.

 

Criteria air pollutants:

 

1) Carbon monoxide(CO)

 

2) Sulfur dioxide (SO2)

 

3) Nitrogen oxides (NOx)

 

4) Ozone (O3)

 

5)  Particulates or particulate matter (PM10).

 

6)  Lead (Pb), the sixth, was included at a time when it was being emitted in dangerous amounts.

 

The US EPA now calls these pollutants, the six principal  pollutants or six common pollutants.

 

tates and worldwide.

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