Smog is dirty air.
It looks like thick fog. It can come from cars and smoke. This air can make us sick. We must keep our air clean.
Do you like fresh air?
Smog is a type of dirty air.
It looks like a thick, hazy fog. The name comes from the words smoke and fog.
Smog can come from many things. Cars and trucks make it when they drive. Burning coal for heat also makes it.
In the summer, the sun helps make smog. The sunlight hits the air and changes it. This is a special kind of summer smog.
In the winter, it can be very cold. People burn more coal to stay warm. This adds more smoke to the air.
Sometimes, the air gets trapped near the ground. This makes the smog stay in one place. It is important to study our air.
Smog is a type of intense air pollution. The name comes from two words: smoke and fog.
It can look like a thick, hazy cloud.
Smog is made of different parts. Some are primary pollutants. These come straight from a source. For example, coal fires give off sulfur dioxide. Others are secondary pollutants. These form when primary parts have chemical reactions in the air. One example is ozone.
There are two main types of smog. Summer smog happens when it is warm. Sunlight hits gases from cars and factories. This creates photochemical smog.
This type of smog is common in sunny cities.
Winter smog is different. In cold months, people burn more coal to heat buildings. This adds smoke to the air. Often, an inversion happens in winter. An inversion is when warm air traps cold air near the ground. This keeps the pollution from moving away.
Smog can also come from nature. Volcanoes release sulfur dioxide and smoke. This is sometimes called vog. Plants can also release gases that help make smog.
Smog is a type of very intense air pollution. The name is a mix of two words: smoke and fog.
This pollution creates a thick, hazy cloud in the sky. It can be very dark or even look like pea soup. This type of haze is made of many different things. It includes nitrogen oxides, sulfur oxide, and ozone. It also contains smoke and other tiny particles. Smog can be dangerous to people. It can cause severe sickness or even lead to death.
Smog works through two different types of pollution. First, there are primary pollutants. These come directly from a source. For example, burning coal releases sulfur dioxide. Next, there are secondary pollutants. These form when primary pollutants have chemical reactions in the air. One important secondary pollutant is ozone.
In some places, an inversion helps the smog grow. An inversion is when warm air traps cold air near the ground. This stops the pollution from moving away. This keeps the bad air close to where people live.
There are two main ways smog forms depending on the season. Summer smog is often called photochemical smog. This happens when sunlight hits gases from cars and factories. The sunlight causes a chemical reaction. This reaction creates ground-level ozone and other particles.
Winter smog is different. In the winter, it is colder. People burn more coal and fossil fuels to heat their homes. These emissions stay near the ground during winter inversions. This creates a thick layer of smoke and fog.
People have been studying this for a long time. The word "smog" appeared in print as early as 1880. A man named Henry Antoine Des Voeux wrote about it in 1905. He said the word was a way to describe smoky fog in cities. In the 1940s, a chemist named Arie Haagen-Smit studied smog in Los Angeles. He used special tools to collect chemicals from the air. He discovered that sunlight and car exhaust were the main ingredients for ozone.
He worked with Arnold Beckman to build tools for monitoring air quality.
Smog can come from many places we see every day. Cars, trucks, and buses release gases from their engines. Large factories also release fumes into the sky. In some places, like Delhi, farmers burn crops to clear fields. This makes the smog even worse.
Even nature can play a part in making smog. Volcanoes can release sulfur dioxide and smoke. This natural smog is sometimes called "vog." Even plants can release gases that react in the air.
Smog is a type of intense air pollution that creates a visible haze in the atmosphere. The term is a portmanteau, which means it combines the words "smoke" and "fog."
This mixture includes various substances like nitrogen oxides, sulfur oxide, ozone, and tiny particles. Smog is a serious environmental issue because it can be toxic to humans. Exposure can lead to severe sickness, shortened life spans, or premature death.
To understand smog, we must distinguish between primary and secondary pollutants. Primary pollutants are emitted directly from a specific source. For example, burning coal releases sulfur dioxide directly into the air. Secondary pollutants are not emitted directly from a source. Instead, they form when primary pollutants undergo chemical reactions in the atmosphere. Ozone is a major secondary pollutant that forms through these complex interactions.
Scientists categorize smog into two main types: summer smog and winter smog. Summer smog is often called photochemical smog. This type is driven by sunlight and warmer temperatures. It is common in cities with sunny, dry climates and many motor vehicles.
Winter smog occurs during colder months. During winter, people use more coal and fossil fuels to heat buildings. This type of smog is often worsened by atmospheric inversions. An inversion happens when warm air traps cold air near the ground. This prevents pollutants from dispersing, keeping them trapped where people breathe.
Photochemical smog formation is a specific, sunlight-driven chemical process. It begins when nitrogen dioxide (NO2) absorbs solar radiation. This causes the molecule to split into nitric oxide (NO) and a free oxygen atom. That oxygen atom then combines with molecular oxygen (O2) to create ozone (O3).
Volatile organic compounds (VOCs), which come from cars and industry, also play a role. These compounds react with nitric oxide, which prevents the ozone from being destroyed. This allows ozone concentrations to build up throughout the day. Other harmful substances like peroxyacetyl nitrates (PANs) and aldehydes also form during these reactions.
Many human activities contribute to the creation of these pollutants. Transportation is a major source, as cars, trucks, and buses emit carbon monoxide, nitrogen oxides, and hydrocarbons. Industrial fumes and coal combustion also release significant amounts of gases. In some regions, such as Delhi, agricultural practices like stubble burning add to the severity.
Even natural events can cause smog-like conditions. Erupting volcanoes release sulfur dioxide and particulate matter. This natural version is often called "vog" to distinguish it from man-made smog. Additionally, plants release hydrocarbons like isoprene that can react in the atmosphere to increase ozone.
Our understanding of smog has evolved through scientific discovery. The word "smog" appeared in print as early as 1880. However, Henry Antoine Des Voeux is often credited with coining the term in a 1905 paper. In the 1940s, a flavor chemist named Arie Haagen-Smit began studying the air in Los Angeles. He adapted his equipment to collect chemicals and identified ozone as a key component.
He discovered that sunlight reacting with automotive exhaust and hydrocarbons was the cause. He worked with Arnold Beckman, who developed tools like air quality monitoring vans to detect these pollutants.
Smog affects many different parts of the world in various ways. Large cities like Los Angeles, Beijing, Delhi, and Mexico City often face high pollution levels.
In some cases, the smog is so thick that it forces cities to close roads, schools, or airports. For example, in 2013, the Chinese city of Harbin faced such closures due to smoke. Because smog travels with the wind, it can move from busy cities into sparsely populated areas. It is a global challenge that connects industrial activity, weather patterns, and human health.
Where will your curiosity go next?
🖼️ Images & Media (17)
+ 5 more
More to explore
✨ What else?
Related topics you might enjoy
🪜 Step back
Simpler topics to build understanding
What is Nepedia?
A free, ad-free encyclopedia for children. Every article is written at five reading levels, so the same page works for a five-year-old and a fifteen-year-old — use the level switcher above to see this one change. No account needed to read.