Fog And Air Pollution: What's The Connection?

Fog and smog may look similar, but they are formed in different ways and have distinct effects on human health and the environment. Fog is a natural phenomenon that occurs when water vapour in the air condenses, resulting in water droplets that reduce visibility. Smog, on the other hand, is a form of air pollution caused by chemical toxins dispersed into the atmosphere, primarily from vehicle emissions, industrial fumes, and agricultural burning. This toxic mixture of smoke and fog fills the lungs with carcinogens and can cause severe respiratory problems, eye irritation, and even premature death. While fog can cause breathing difficulties, smog poses a more serious health risk and is a significant concern in highly industrialised cities worldwide.

Smog is a blend of smoke and fog

While fog is a natural occurrence, smog is primarily a human-made phenomenon, commonly found in large cities with high levels of industrial and vehicular emissions. The smoke and fog combine with harmful gases, soot, and dust particles to form a toxic mixture. This toxic mixture is what differentiates smog from fog, as fog is simply water vapour in the air that condenses into tiny droplets that stay suspended in the air, reducing visibility.

Photochemical smog, also known as "Los Angeles smog," occurs in urban areas with a high number of automobiles and does not require the presence of smoke or fog. It is caused by nitrogen oxides and hydrocarbon vapours emitted by vehicles and other sources, which react with sunlight to form toxic ozone. This type of smog can cause a range of health issues, including eye irritation, coughing, respiratory distress, and plant damage.

Another type of smog is sulfurous smog, also called "London smog," which results from a high concentration of sulfur oxides in the air due to the use of sulfur-bearing fossil fuels, particularly coal. In the mid-20th century, London was notorious for its coal-caused smogs, nicknamed "pea-soupers."

Smog can have severe health effects, including respiratory problems, eye irritation, coughing, and congestion. It fills the lungs with carcinogens, which can lead to cancer and other severe health issues. The particulate matter in smog can also cause road accidents due to reduced visibility.

To protect oneself from the harmful effects of smog, it is recommended to wear effective air masks when going outdoors and to seek medical guidance if symptoms persist or worsen. Maintaining a healthy diet and monitoring indoor air quality are also important measures to mitigate the impact of smog.

Smog is a sign of air pollution

Smog is a combination of smoke and fog, hence the name, and is a type of intense air pollution. It is composed of nitrogen oxides, sulfur oxide, ozone, smoke, and other particulates. While fog can cause breathing problems, smog is worse as it fills the lungs with cancer-causing carcinogens that are hard to flush out. Smog is often categorized as either summer or winter smog. Summer smog is primarily associated with the photochemical formation of ozone, while winter smog is worse during periods of warmer, sunnier weather when the upper air is warm enough to inhibit vertical circulation.

Smog is derived from coal and vehicular combustion emissions, industrial emissions, forest and agricultural fires, and photochemical reactions of these emissions. The major culprits from transportation sources are carbon monoxide, nitrogen oxides, and volatile organic compounds, including hydrocarbons. Transportation emissions also include sulfur dioxides and particulate matter but in much smaller quantities than the pollutants mentioned previously. The nitrogen oxides and volatile organic compounds can undergo a series of chemical reactions with sunlight, heat, ammonia, moisture, and other compounds to form the noxious vapors, ground-level ozone, and particles that comprise smog.

Photochemical smog, as found in cities like Los Angeles, is a type of air pollution derived from vehicular emissions from internal combustion engines and industrial fumes. These pollutants react in the atmosphere with sunlight to form secondary pollutants that also combine with the primary emissions to form photochemical smog. In certain other cities, such as Delhi, the severity of smog is often aggravated by stubble burning in neighboring agricultural areas. The atmospheric pollution levels of Los Angeles, Beijing, Delhi, Lahore, Mexico City, and Tehran are often increased by an inversion that traps pollution close to the ground.

The effects of air pollution are detrimental to human health and the planet as a whole. According to the World Health Organization (WHO), indoor and outdoor air pollution is responsible for nearly seven million deaths globally each year. In 2021, carbon dioxide accounted for roughly 79% of the country's total greenhouse gas emissions, and methane made up more than 11%. Delhi, the most polluted city in the world, has seen an increase in lung-related ailments, especially asthma and lung cancer, among children and women.

Smog and fog have different formations

Smog and fog are two different meteorological phenomena with distinct compositions and formation processes. While fog is a natural occurrence, smog is a form of intense air pollution.

Fog is a cloud that forms near the Earth's surface when water vapour in the air condenses, resulting in water droplets that stay suspended in the air, creating a whitish layer that reduces visibility. This process is similar to the formation of clouds at higher altitudes. Fog is a natural phenomenon that typically occurs during winters and is characterized by reduced visibility, typically less than 1 kilometre.

On the other hand, smog is a combination of smoke, fog, and particulate matter. It is primarily caused by human activities such as vehicular emissions, industrial processes, and the burning of fossil fuels like coal. These activities release pollutants such as nitrogen oxides (NOx), sulfur oxides (SOx), volatile organic compounds (VOCs), carbon monoxide (CO), and particulate matter. These pollutants undergo chemical reactions in the atmosphere, forming secondary pollutants that contribute to the formation of smog.

The formation of smog can be influenced by meteorological conditions. During winter, the increased usage of coal and fossil fuels for heating, combined with atmospheric inversions that trap pollutants close to the ground, leads to the formation of winter smog. In contrast, summer smog, also known as photochemical smog, is more common in urban areas with a high number of automobiles. It occurs when nitrogen oxides and volatile organic compounds react with sunlight, heat, and other compounds, forming noxious vapours, ground-level ozone, and particulate matter that comprise smog.

While fog does not cause any health issues, smog can have serious health implications. The toxic gases and particles in smog can cause eye irritation, coughing, respiratory problems, and even lead to long-term health issues such as lung infections, asthma, and bronchitis. Smog fills the lungs with carcinogens, which are difficult to flush out, making it more dangerous than fog.

Smog is more dangerous to health

Fog and smog are formed through different processes and have distinct effects on human health. While fog can cause breathing problems, smog is significantly more harmful to human health. Smog is a combination of smoke and fog, and it fills the lungs with carcinogens, which are difficult to flush out. Smog is formed when industrial emissions from power plants, factories, cars, and other sources react with heat and sunlight in the atmosphere. The major pollutants from transportation sources are carbon monoxide, nitrogen oxides, and volatile organic compounds, including hydrocarbons, which are the main component of petroleum fuels such as gasoline and diesel fuel.

Smog can cause severe eye irritation, coughing, congestion, and other respiratory issues. It can also irritate the airways, increasing the risk of serious heart and lung diseases, especially in children. The severity of smog is often higher in cities like Delhi, where it is aggravated by stubble burning in neighboring agricultural areas.

The term "smog" was first used in a publication from 1880, but it was popularized by Henry Antoine Des Voeux in his 1905 paper, "Fog and Smoke," presented at a meeting of the Public Health Congress. Des Voeux's work highlighted the deadly effects of smog, which was causing fatalities in Birmingham, England, at the time.

The Environmental Defense Fund (EDF) has been advocating for stricter air quality standards to protect public health. In 2015, the EPA lowered the nation's air quality standard for smog pollution from 75 parts per billion (ppb) to 70 ppb, recognizing the strong evidence of the harmful health effects of ozone.

Smog and fog have different colours

Smog and fog are formed differently and have different colours. While fog is a naturally occurring event, witnessed commonly during winters, smog is a mixture of smoke and fog. The smoke in smog is generated by the improper handling and combustion of coal and fossil fuels, vehicle emissions, and other human activities.

The presence of smoke in smog gives it a distinct colour, which sets it apart from fog. Fog is often described as having a whitish or whiter colour, while smog appears in tones of grey. This difference in colour can be used as a visual cue to distinguish between the two.

The colour of smog can vary depending on its composition and the light conditions in which it is observed. For example, the bluish haze observed over the Po River Valley in northern Italy during the cold season is attributed to the solid or liquid residue left behind when fog droplets evaporate. This bluish hue is more prominent during the day and may appear as a patch of white fog during the night or early morning.

In addition to the colour differences, smog and fog also differ in their impact on human health. While fog may cause some breathing problems, particularly in individuals with pre-existing health conditions, smog poses more severe health risks. The high levels of hazardous gases and cancer-causing carcinogens in smog can lead to eye irritation, coughing, respiratory issues, and serious long-term health consequences.

Furthermore, smog and fog have distinct effects on visibility. Both phenomena can reduce visibility, but smog typically results in a denser haze that can significantly impair visibility to less than 500 meters, increasing the risk of road accidents.

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