Air pollution can harm human health, the environment, and property. The main air pollutants are particulate matter, ground-level ozone, nitrogen dioxide, sulfur dioxide, and carbon monoxide. Short-term exposure to elevated levels can cause respiratory illness while long-term exposure is linked to increased risk of heart and lung disease. Air pollution also harms vegetation and infrastructure. International standards aim to limit human exposure and environmental damage.

1. Air Pollution
General

2. Definition
Air pollution may be defined as the presence
in the air (outdoor atmosphere) of one or
more contaminants or combinations
thereof in such quantities and of such
durations as may be or tend to be
injurious to human, animal or plant life,
or property, or which unreasonably
interferes with the comfortable
enjoyment of life or property or
conduct of business.

3. Air Pollutant
It is a substance or effect dwelling temporarily or
permanently in the air , which adversely alters the
environment by interfering with the health, the
comfort, or the food chain, or by interfering with the
property values of people.
A pollutant can be solid (large or sub-molecular), liquid
or gas .
It may originate from a natural or anthropogenic source
(or both).
It is estimated that anthropogenic sources have changed
the composition of global air by less than 0.01%.
However, it is widely accepted that even a small change
can have a significant adverse effect on the climate,
ecosystem and species on the planet.
Examples of these are acid rain, ozone in the lower
atmosphere, and photochemical smog.

4. Composition of
dry atmosphere, by volume
ppmv: parts per million by volume
Gas Volume
Nitrogen (N2) 780,840 ppmv (78.084%)
Oxygen (O2) 209,460 ppmv (20.946%)
Argon (Ar) 9,340 ppmv (0.9340%)
Carbon dioxide
375 ppmv
(CO2)
Neon (Ne) 18.18 ppmv
Helium (He) 5.24 ppmv
Methane (CH4) 1.745 ppmv
Krypton (Kr) 1.14 ppmv
Hydrogen (H2) 0.55 ppmv
Not included in above dry atmosphere:
Water vapor
typically 1%
(highly variable)
Mean Atmospheric Water Vapor.
Source for figures above: NASA. Carbon dioxide and methane updated (to 1998) by IPCC TAR table 6.1 [1]. The NASA total was 17 ppmv
over 100%, and CO2 was increased here by 15 ppmv. To normalize, N2 should be reduced by about 25 ppmv and O2 by about 7 ppmv.
Minor components of air not listed above include:
Gas Volume
nitrous
0.5 ppmv
oxide
xenon 0.09 ppmv
ozone 0.0 to 0.07 ppmv
nitrogen
0.02 ppmv
dioxide
iodine 0.01 ppmv
carbon
trace
monoxide

9. National Ambient Air Quality Standards
Pollutant Primary Stds. Averaging Times Secondary
Stds.
1
Carbon Monoxide 9 ppm (10 8-hour None
3
mg/m )
1
35 ppm 1-hour None
3
(40 mg/m )
3
Lead 1.5 µg/m Quarterly Average Same as
Primary
Nitrogen Dioxide 0.053 ppm Annual (Arithmetic Same as
3
(100 µg/m ) Mean) Primary
Particulate Matter 50 µg/m3 Annual2 (Arith. Same as
(PM10) Mean) Primary
3 1
150 ug/m 24-hour
3 3
Particulate Matter 15.0 µg/m Annual (Arith. Same as
(PM2.5) Mean) Primary
3 4
65 ug/m 24-hour
5
Ozone 0.08 ppm 8-hour Same as
Primary
Sulfur Oxides 0.03 ppm Annual (Arith. Mean) -------
1
0.14 ppm 24-hour -------
1
------- 3-hour 0.5 ppm
3
(1300 ug/m )
1
Not to be exceeded more than once per year.
2
To attain this standard, the 3-year average of the weighted annual mean PM10 concentration at
3
each monitor within an area must not exceed 50 ug/m .
3
To attain this standard, the 3-year average of the weighted annual mean PM2.5 concentrations
3
from single or multiple community-oriented monitors must not exceed 15.0 ug/m .
4
To attain this standard, the 3-year average of the 98th percentile of 24-hour concentrations at
3
each population-oriented monitor within an area must not exceed 65 ug/m .
5
To attain this standard, the 3-year average of the fourth-highest daily maximum 8-hour average
ozone concentrations measured at each monitor within an area over each year must not exceed
0.08 ppm.

10. Index PSI Cautionary
Value Descriptor
General Statements
Health
Effects
Up to 50 Good None for the None required.
general population.
50 to 100 Moderate Few or none for None required.
the general
population.
100 to Unhealthful Mild aggravation of Persons with
200 symptoms among existing heart or
susceptible people, respiratory
with irritation ailments should
symptoms in the reduce physical
healthy population. exertion and
outdoor activity.
General population
should reduce
vigorous outdoor
activity.
200 to Very Significant Elderly and
300 Unhealthful aggravation of persons with
symptoms and existing heart or
decreased exercise lung disease
tolerance in should stay
persons with heart indoors and reduce
or lung disease; physical activity.
widespread General population
symptoms in the should avoid
healthy population. vigorous outdoor
activity.
Over 300 Hazardous Early onset of Elderly and
certain diseases in persons with
addition to existing diseases
significant should stay
aggravation of indoors and avoid
symptoms and physical exertion.

14. Health Effects of Nitrogen
Oxides
• Short-term exposure at concentrations greater than
3 parts per million (ppm) can measurably decrease
lung function.
• Concentrations less than 3 ppm can irritate lungs.
• Concentrations as low as 0.1 ppm cause lung
irritation and measurable decreases in lung function
in asthmatics.
• Long-term lower level exposures can destroy lung
tissue, leading to emphysema.
• Children may also be especially sensitive to the
effects of nitrogen oxides.

15. Other Effects
• Seriously injure vegetation at certain
concentrations. Effects include:
– Bleaching or killing plant tissue.
– Causing leaves to fall.
– Reducing growth rate.
• Deteriorate fabrics and fade dyes.
• Corrode metals (due to nitrate salts
formed from nitrogen oxides).
• Reduce visibility.

16. Other Effects (Continued)
• Oxides of nitrogen, in the presence of
sunlight, can also react with
hydrocarbons, forming photochemical
oxidants or smog.
• Also, NOx is a precursor to acidic
precipitation, which may affect both
terrestrial and aquatic ecosystems.

17. Sulfur Dioxide
Ninety-five percent of pollution related sulfur
oxide emissions are in the form of sulfur
dioxide (SO2), a heavy, colorless gas with an
odor like a struck match.
This gas combines easily with water vapor,
forming aerosols of sulfurous acid (H2SO3), a
colorless, mildly corrosive liquid.
This liquid may then combine with oxygen in
the air, forming the even more irritating and
corrosive sulfuric acid (H2SO4).

18. Other sulfur-containing
compounds
• Hydrogen sulfide (H2S) gas - rotten eggs.
• Mercaptans - skunk spray or decayed
garbage. (Added in trace amounts to natural
gas, providing a leak-detecting warning
odor.)
Note: The amount of SO2 released from coal
fired power plants depends on the sulfur
content of coal, normally 0.7% to 2% by
weight. High sulfur coal sometimes contains
as much as 6% sulfur by weight. In India,
sulfur content is quite low.

19. Health Effects of Sulfur Oxides
• Sulfur dioxide not only has a bad odor, it can
irritate the respiratory system.
• Exposure to high concentrations for short
periods of time can constrict the bronchi and
increase mucous flow, making breathing
difficult.
• Children, the elderly, those with chronic lung
disease, and asthmatics are especially
susceptible to these effects.

20. Sulfur dioxide can also:
• Immediately irritate the lung and throat at
concentrations greater than 6 parts per
million (ppm) in many people.
• Impair the respiratory system's defenses
against foreign particles and bacteria, when
exposed to concentrations less than 6 ppm
for longer time periods.
• Apparently enhance the harmful effects of
ozone. (Combinations of the two gases at
concentrations occasionally found in the
ambient air appear to increase airway
resistance to breathing.)

21. • Sulfur dioxide tends to have more toxic effects when acidic
pollutants, liquid or solid aerosols, and particulates are also
present. (In the past, thousands of excess deaths occurred in
areas where SO2 concentrations exceeded 1 ppm for a few days
and other pollutants were also high.) Effects are more
pronounced among mouth breathers, e.g., people who are
exercising or who have head colds.
These effects include:
• Health problems, such as episodes of bronchitis requiring
hospitalization associated with lower-level acid concentrations.
• Self-reported respiratory conditions, such as chronic cough and
difficult breathing, associated with acid aerosol concentrations.
(Asthmatic individuals are especially susceptible to these effects.
The elderly and those with chronic respiratory conditions may
also be affected at lower concentrations than the general
population.)
• Increased respiratory tract infections, associated with longer
term, lower-level exposures to SO2 and acid aerosols.
• Subjective symptoms, such as headaches and nausea, in the
absence of pathological abnormalities, due to long-term
exposure.

22. Sulfur oxides Effects on Plants
• Sulfur dioxide easily injures many plant species and
varieties, both native and cultivated. Some of the
most sensitive plants include various commercially
valuable pines, legumes, red and black oaks, white
ash, alfalfa and blackberry. The effects include:
• Visible injury to the most sensitive plants at
exposures as low as 0.12 ppm for 8 hours.
• Visible injury to many other plant types of
intermediate sensitivity at exposures of 0.30 ppm for
8 hours.
• Positive benefits from low levels, in a very few
species growing on sulfur deficient soils.

23. Other Effects
• Increases in sulfur dioxide concentrations
accelerate the corrosion of metals, probably
through the formation of acids. (SO2 is a
major precursor to acidic deposition.) Sulfur
oxides may also damage stone and masonry,
paint, various fibers, paper, leather, and
electrical components.
• Increased SO2 also contributes to impaired
visibility. Particulate sulfate, much of which
is derived from sulfur dioxide emissions, is a
major component of the complex total
suspended particulate mixture.

24. Health Effects of Ozone
• Ozone acts as a powerful respiratory irritant
at the levels frequently found in most of the
nation's urban areas during summer months.
• Ozone exposure may lead to:
– Shortness of breath.
– Chest pain when inhaling deeply.
– Wheezing and coughing.
Long-term, repeated exposure to high levels
of ozone may lead to large reductions in
lung function, inflammation of the lung
lining, and increased respiratory
discomfort.