Smog is a type of air pollution formed when emissions from burning fossil fuels like coal and oil react with oxygen and sunlight. It causes reduced visibility and health issues. There are two main types: London smog forms from coal burning and contains sulfuric acid, while photochemical smog forms in cities from vehicle and factory emissions reacting with sunlight to produce ozone. Smog causes eye and respiratory irritation and health problems, damages crops and buildings, and reduces visibility. To reduce smog, efforts should be made to conserve energy, use public transportation, and reduce emissions from vehicles and industry.

1. SMOG
- BY NANDITA CHAKRABORTY

2. ● What is Smog?
 ’Smog’ is the combination of smoke & fog. [Smog = Smoke + Fog]
 Smog is a form of air pollution caused by tiny particles in the air.
 The term smog was first coined in 1905 in a paper by Dr. Henry Antoine Des Voeux to
describe combination of smoke and fog.
 It is hazy mixture of heavily polluted air that can form in cities due to the emissions
of sulfur dioxide and aerosols from the burning of fossil fuels (primarily coal and oil).
 It is generally formed in winter under calm, stable, and moist conditions.
 The term is now applied to all forms of severe air pollution, particularly in urban
areas, that restrict visibility and people suffer from breathing problems.

3. ● The factors responsible for formations of smog
are :
1. Inversion of temperature
2. Mixing of the polluted gases emitted from industries & motor vehicles with foggy air

4. London
Smog
or
Sulphurous
Smog
: Types of Smog :
Photochemical
SMOG

5. ● London Smog
or Sulphurous Smog :
 Classic smog forms in areas with high water vapor and high levels of sulfur
emissions, usually from burning coal.
 Sulfur particles dissolve into water droplets to form sulfuric acid in the atmosphere,
while coal soot darkens the skies.
 This type of smog is most commonly associated with London and is referred as
“London smog” or Sulphurous smog and causes dark brownish colour of
atmosphere. It is also referred as classical / industrial smog .
 The main constituent of London-type smog is soot and it also contain large
quantities of fly ash, sulfur dioxide, sodium chloride, and calcium sulfate particles.

6. ● London Smog
or Sulphurous Smog reactions:
 If concentrations are high, sulfur dioxide can react with atmospheric hydroxide to produce sulfuric
acid, that will precipitate as acid rain.
 SO2+OH . → HOSO2
 HOSO2+O2 → HO2+SO3
 SO3+H2O → H2SO4
 C + O2 → CO2
 2C + O2 → 2CO
 S + O2 → SO2
 2SO2 + O2 → 2SO3
 SO3 + H2O → H2SO4
 2NH3 + H2SO4 → (NH4)2SO4

7. ● Photochemical smog :
 It is the haze created when sunlight reacts with primary pollutants like nitrogen oxides
and volatile organic compounds that can be found in fossil fuel emissions from
automobiles, factories, and power plants.
 These reactions create secondary pollutants and are characterized by high
concentrations of a large variety of pollutants, such as nitrogen oxides, O3, CO,
hydrocarbons, aldehydes (and other materials that are eye irritants), and sometimes
sulfuric acid as well.
 Photochemical smog is a problem in large cities around the world and is best
exemplified by cities like Los Angeles, Mexico city etc.
 This type of smog was first observed in Loa Angeles in 1950 and hence, is named ‘Los
Angeles Smog’.

8. ● Photochemical smog REACTIONS:
► N2 + O2 → 2NO During Combustion in the Troposphere
► 2NO + O2 → 2NO2 ( Nitrogen Dioxide )
► 3NO2 + H2O → 2HNO3 + NO ( Nitric acid + Nitric Oxide )
► NO2 + UV Radiation → NO + O
► O2 + O → O3 ( Photochemical Ozone )
► Hydrocarbons + O2 + NO → PANs ( Peroxyacyl Nitrates )
► O & O3 + Hydrocarbons → Aldehydes

9. ● EFFECT OF SMOG:
 The major constituents of smog, with the exception of CO2, are powerful poisons. •
Smog reduce visibility and create an unattractive haze on the horizon .
 Photochemical smog causes irritation of the eyes, nose, throat, and chest.
 Smog can make breathing more difficult by chocking lungs. This can be especially
troubling for people with asthma.
 Smog pollution has been known to damage crops (blighting plants), as well as to
cause health problems in pets and farm animals.
 Smog has also been known to cause corrosive damage to buildings and vehicles.

10. ● EFFECT OF SMOG ON
OUR EYES :
 Watery eyes
 Burning sensation or discomfort
 Sore eyes
 Redness
 Swelling
 Itching sensation
 Dry eyes: characterized by dryness, gritty
feeling, foreign body in the eye
 Eye allergy: characterized by itching, redness,
discharge, eyelid swelling, blurring of vision
and increased risk of infection
 Eye irritation is not caused by O3, but by
PANs and trace free radical HCs
● REMEDIES :
 The golden rule, of course, would be to avoid
exposure to harmful pollutants. On days when
the pollution levels are such that there is a
public health warning, please stay indoors,
especially in the early hours of the morning
when the pollution levels are at their peak.
 Wash your hands often and try not to touch
your eyes
 Stay hydrated as it will aid in adequate tear
formation.
 Wear sunglasses when outdoors.
 Do not rub your eyes.
 In case the irritation persists, you must visit
your ophthalmologist for an evaluation.

11. ● SMOG REMEDIES :
 Conserve energy - at home, at work, everywhere.
 Look for the ENERGY STAR label when buying home or office equipment.
 Carpool, use public transportation, bike, or walk whenever possible.
 Consider purchasing portable gasoline containers labeled “spill- proof,” where
available.
 Be sure your tires are properly inflated.
 Use environmentally safe paints and cleaning products whenever possible.
 Mulch or compost leaves and yard waste.
 Avoid burning leaves, trash, and other materials.

12. - THANK YOU -
Year : 1st Year (2nd Semester)
Course : B.Optometry