Introduction

Air Pollution: An air pollutant is any substance in the air that can cause harm to humans or the environment.

Pollutants may be natural or man-made and may take the form of solid particles, liquid droplets or gases.

The common industrial air pollutants:

• Ozone O₃

• Particulate Matter

• Carbone Monoxide

• Nitrogen Dioxides NO_X

• Sulfur Dioxide So₂

• Lead

Ozone O3

Ozone is a gas that occurs both in the Earth’s upper atmosphere and at ground level.

Ozone can be “good” or “bad” for your health and the environment, depending on its location in the atmosphere.

Good Ozone

The troposphere generally extends to a level about 6 miles up, where it meets the second layer, the stratosphere.

The stratosphere layer contains an ozone or “good” ozone layer extends upward from about 6 to 30 miles and protects life on Earth from the sun’s harmful ultraviolet (UV) rays.

Depletion of Good ozone layer

• Ozone depleting substances {ODS} such as (CFC’S, hallons, methyl bromide, methyl chlroform,,,etc).

• Ozone depleting substance degrade slowly as it released at air till reach to stratosphere by uv rays converts to chlorine and bromine which is responsible for degrade the ozone layer

• Scientists estimate that one chlorine atom can destroy 100,000 “good” ozone molecules.

Effect of depletion good ozone layer on human health and environment

Ozone depletion can cause increased amounts of UV radiation to reach the Earth which can lead to more cases of skin cancer, cataracts, and impaired immune systems and damage sensitive crops, such as soybeans, and reduce crop yields.

What is being done About the Depletion of “Good” Ozone?

The international community adopted a treaty called the Montreal Protocol to phase out the production and use of ozone-depleting substances in 1987.

Warning labels for all products containing CFCs  cause depleting ozone layer indicate its using is prohibited.

Releases into the air of refrigerants used in car and home air conditioning units and appliances are also prohibited.

Some substitutes to ozone-depleting products have been produced and others are being developed.

If the United States and other countries stop producing ozone-depleting substances, natural ozone production should return the ozone layer to normal levels by about 2050.

Bad Ozone

Ozone occurs in two layers of the atmosphere. The layer closest to the Earth’s surface is the troposphere.

Here, ground-level or “bad” ozone formed by the chemical reactions between oxides of nitrogen (NOX) and volatile organic compounds (VOC) in the presence of sunlight to form ground-level or “bad” ozone which is :

• An air pollutant and harmful to breathe: Breathing ozone can trigger a variety of health problems including chest pain, coughing, throat irritation, and congestion. It can worsen bronchitis, emphysema, and asthma and also can reduce lung function and inflame the linings of the lung.

• It damages crops, trees and other vegetation and increased susceptibility to diseases, pests and other stresses such as harsh weather.

• It is a main ingredient of urban smog.

Air Pollution by Particulate matter

Particulate matter is the term for particles found in the air, including dust, dirt, soot, smoke, and liquid droplets.

Some particles are directly emitted into the air, they come from a variety of sources such as cars, trucks, buses, factories, construction sites, tilled fields, unpaved roads, stone crushing, and burning of wood.

Air Pollution by Carbon Monoxide

Physical properties: odorless, colorless.

It results from incomplete burning of fuel.

Sources:

• Fuel Combustion 6%
• Miscellaneous 12%
• Industrial Process 4%
• Non-road Vehicles & Engines 22%
• On-road Vehicles 56%

Air Pollution by Nitrogen Oxides

NOx is highly reactive gases.

Many of the nitrogen oxides are colorless and odorless.

The common pollutant, nitrogen dioxide (NO2) along with particles in the air can often be seen as a reddish-brown layer over many urban areas.

Nitrogen oxides are formed when fuel is burned at high temperatures, as in a combustion process.

Sources:

• Utilities 27%
• Motor vehicles 49%
• Industrial residential 19%

Sulfur Dioxide

So₂ belongs to the family of sulfur oxide gases (SO_X).

These gases dissolve easily in water.

Sulfur is prevalent in all raw materials, including crude oil, coal, and ore that contains common metals like aluminum, copper, zinc, lead, and iron.

SO_X gases are formed when fuel containing sulfur such as coal and oil is burned.

So₂ dissolves in water vapor to form acid, and interacts with other gases and particles in the air to form sulfates and other products that can be harmful to people and their environment.

Sources:

• Electric Utilities  over than 65% (burn coal)
• large ships, and some non road diesel equipment currently burn high sulfur fuel and release SO2 emissions to the air in large quantities.

Lead

It is a metal found naturally in the environment.

Due to the phase out of leaded gasoline, metals processing is the major source of lead emissions to the air today.

The highest levels of lead in air are generally found near lead smelters.

Sources:

• Motor vehicles (such as cars and trucks) .
• Other stationary sources are waste incinerators, utilities, and lead-acid battery manufacturers.

What Is the AQI?

The AQI is an index for reporting daily air quality, It tells you how polluted your air is, and what associated health effects.

The AQI focuses on health effects you may experience within a few hours or days after breathing polluted air.

EPA calculates the AQI for five major air pollutants ground-level ozone, particulate matter, carbon monoxide, sulfur dioxide, and nitrogen dioxide.

For each of these pollutants, EPA has established national air quality standards to protect public health.

Value of the AQI runs from 0 to 500,The higher the AQI value, the greater the level of air pollution and the greater the health effect.

For example:

AQI values below 100 are satisfactory. When AQI values are above 100, air quality is considered to be unhealthy while an AQI value over 300 represents hazardous air quality.