“Fog and smog should not be confused and are easily separated by colour” Chuck Jones

Hafiz Arslan
Nov 7 · 4 min read

It is a type of intense air pollution, formed by the condensing of smoke in the air. Tiny water molecules in the air condenses and attains the terminal velocity (The downward force of gravity equals the restraining force of drag plus the buoyancy. The net force on the object is zero, and the result is that the velocity of the object remains constant) are known as fog, it happens in the winter season and the time when relative humidity is high. Whereas when this all mixed with the smoke molecules in the air and water molecules on condensing that smoky fog is called Smog.

How did smog get its name?
This term was first used in London in early 1900s to describe the combination of smoke and fog by the Dr Henry Antoine des Voeux in his paper, “Fog and Smoke,” which he presented at a meeting of the Public Health Congress in July 1905. The main reason described by him was the combination of smoke and Sulphur dioxide, which resulted from the heavy use of coal-burning for maintaining the room temperature at homes and businesses as well as in the industries.

What causes smog?
It is produced by a set of complex photochemical reactions involving volatile organic compounds, Nitrogen oxide, and sunlight forming ozone at the ground level (ozone in the atmosphere plays a significant role in the reflection of harmful ultraviolet rays but at the ground level when people are forcefully inhaling it, this becomes itself harmful). Smog forming pollutants come from various sources like automobile exhaust, power plants, industrial units, paints, hairsprays, charcoal starter fluid, chemical solvents and even plastic popcorns packaging.

In typical urban areas, at least half of the smog precursors come from cars, buses, trucks, and boats. Major smog occurrences often are linked to heavy motor vehicle traffic, high temperatures, sunshine, and calm winds. Weather and geography affect the location and severity of smog. Because temperature regulates the length of time it takes for smog to form, smog can occur more quickly and be more severe on a hot, sunny day.

When temperature inversions occur (that is, when warm air stays near the ground instead of rising) and the wind is calm, smog may remain trapped over a city for days. As traffic and other sources add more pollutants to the air, the smog gets worse.

Ironically, smog is often more severe farther away from the sources of pollution, because the chemical reactions that cause smog to take place in the atmosphere while pollutants are drifting on the wind.

Where Does Smog Occur?
Severe smog and ground-level ozone problems exist in almost all the major cities around the world. To varying degrees, the majority of U.S. cities with populations of 500,000 or more have experienced problems with smog and ground-level ozone.

According to some studies, more than half of all U.S. residents live in areas where the smog is so bad that pollution levels routinely exceed safety standards set by the U.S. Environmental Protection Agency (EPA).

What are the effects of Smog?
As it is made up of a combination of air pollutants that can compromise human health, harm the environment, and even cause property damage. Smog can cause or aggravate health problems such as asthma, emphysema, chronic bronchitis and other respiratory problems as well as eye irritation and reduced resistance to colds and lung infections. The ozone in the smog also inhibits plant growth and can cause widespread damage to crops and forests.

Who is at the most risk of Smog?
Anyone who engages in strenuous outdoor activity — from jogging to manual labour — may suffer smog-related health effects. Physical activity causes people to breathe faster and more deeply, exposing their lungs to more ozone and other pollutants. Four groups of people are particularly sensitive to ozone and other air pollutants in smog:

  • Children: Active children run the highest risks from exposure to smog, as children spend a lot of time playing outside. As a group, children are also more prone to asthma the most common chronic disease for children and other respiratory ailments than adults.
  • Adults who are active outdoors: Healthy adults of any age who exercise or work outdoors are considered at higher risk from smog.
  • People with respiratory diseases: People with asthma or other chronic respiratory diseases are more sensitive and vulnerable to the effects of ozone. Typically, they will experience adverse effects sooner and at lower levels of exposure than those who are less sensitive.
  • People with unusual susceptibility to ozone: Some otherwise healthy people are simply more sensitive to the pollutants in smog than other people and may experience more adverse health effects from exposure.

Elderly people are often warned to stay indoors on heavy smog days. Elderly people are probably not at increased risk of adverse health effects from the smog because of their age. Like any other adults, however, elderly people will be at higher risk from exposure to smog if they already suffer from respiratory diseases, are active outdoors, or are unusually susceptible to ozone.

Technologies for the control of air pollution
We can overcome the problem of smog by; identifying and fixing the pollutants emission limits on all of their sources, also we can find out the modification for the industrial process and selecting the control systems for problems. We have to develop and install the Equipment’s or methods used for the gasses and vapours are wet scrubber which is used for adsorption, absorption, chemical oxidations, bio filtrations, scrubber, and chemical reactions of ozone by ultraviolet light. We can also change the fossil fuels engine to alternative fuels, for example, Electric and LPG.

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