air pollution

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Dense smog and orange haze blanket the skyline of Mexico City at sunset, with buildings in the Polanco neighborhood partially obscured by air pollution.

Aerial view of a retail mall and residential apartments in Gurgaon, India, with thick smog obscuring the skyline due to severe air pollution.

A London police officer wearing a protective mask stands in a street shrouded in thick smog, with vehicles and figures barely visible in the background, during the Great Smog of 1952.

New York City skyline tinted orange from wildfire smoke.

Diagram explaining air quality index (AQI) levels with a color-coded bar from green (good) to maroon (hazardous), describing health risks as air quality moves from healthy to unhealthy.

The video thumbnail image shows a person's hand holding small fragments of colorful plastic.

Automobile emissions

Two pie charts compare sources of sulfur dioxide and nitrogen oxides emissions contributing to acid rain. The first chart shows electric utilities produce 66% of SO2, other sources 29%, and vehicles 5%. The second chart shows vehicles produce 58% of NOx, other sources 24%, and electric utilities 18%.

Thick brown layer of smog obscures the Los Angeles skyline, with city buildings and neighborhoods visible beneath a blue sky.

Bhopal, India: pesticide plant

At a Glance

Dense smog and orange haze blanket the skyline of Mexico City at sunset, with buildings in the Polanco neighborhood partially obscured by air pollution.

air pollution summary

air pollution: Media

environmental science

Videos

New York City skyline tinted orange from wildfire smoke.

How Is Air Quality Measured?

Even something as simple as breathing can get complicated.

Video: Encyclopædia Britannica, Inc.

The video thumbnail image shows a person's hand holding small fragments of colorful plastic.

What are microplastics?

What lies beneath? Plastic, probably.

Video: Encyclopædia Britannica, Inc.

Major types of pollution explained

Major types of pollution explained

Learn more about the major kinds of pollution in this infographic explainer.

Video: Encyclopædia Britannica, Inc.

Learn how pollution from industrial emissions and car exhaust is trapped against mountains to cause smog

Learn how pollution from industrial emissions and car exhaust is trapped against mountains to cause smog

Smog formation and entrapment over Los Angeles.

Video: Encyclopædia Britannica, Inc.

Visit Germany's Black Forest to study the effects of industrial emissions, urban smog, and acid rain

Visit Germany's Black Forest to study the effects of industrial emissions, urban smog, and acid rain

Testing rainwater and air for acidity at a research station in the Black Forest,...

Video: Encyclopædia Britannica, Inc.

Images

Dense smog and orange haze blanket the skyline of Mexico City at sunset, with buildings in the Polanco neighborhood partially obscured by air pollution.

Air pollution in Mexico City

Pollution darkening the skies over Mexico City.

© fitopardo.com—Moment/Getty Images

Aerial view of a retail mall and residential apartments in Gurgaon, India, with thick smog obscuring the skyline due to severe air pollution.

Air pollution in Gurugram in 2019

Smog settling in a residential area of Gurugram, Haryana, India.

© Pranay Chandra Singh/Shutterstock.com

A London police officer wearing a protective mask stands in a street shrouded in thick smog, with vehicles and figures barely visible in the background, during the Great Smog of 1952.

Great Smog of London

A police officer wearing a mask during the Great Smog of London, December 1952.

© Keystone—Hulton Archive/Getty Images

Diagram explaining air quality index (AQI) levels with a color-coded bar from green (good) to maroon (hazardous), describing health risks as air quality moves from healthy to unhealthy.

Air Quality Index (AQI) values and their explanation.

The AQI is a tool that describes health risks in breathable air as air quality moves...

Encyclopædia Britannica, Inc.

Automobile emissions

Automobile emissions

Air pollution from vehicle tailpipes. A number of criteria pollutants, including...

© Sergiy Serdyuk/stock.adobe.com

Two pie charts compare sources of sulfur dioxide and nitrogen oxides emissions contributing to acid rain. The first chart shows electric utilities produce 66% of SO2, other sources 29%, and vehicles 5%. The second chart shows vehicles produce 58% of NOx, other sources 24%, and electric utilities 18%.

SO₂ and NO_x emissions in the U.S.

SO₂ and NO_x emissions in the U.S., 2008.

Encyclopædia Britannica, Inc.

Thick brown layer of smog obscures the Los Angeles skyline, with city buildings and neighborhoods visible beneath a blue sky.

Los Angeles smog

A pall of photochemical smog over Los Angeles in November 2016. Photochemical smog,...

© Daniel Stein—iStock/Getty Images

Bhopal, India: pesticide plant

Bhopal, India: pesticide plant

A portion of the remains of the Union Carbide pesticide plant, Bhopal, Madhya Pradesh,...

© Daniel Berehulak—Getty Images

Air pollution

Air pollution

Point source air pollution from factory smokestacks.

© Gina Sanders/stock.adobe.com

Diagram illustrating the greenhouse effect, showing sunlight reaching Earth, some visible light absorbed by the surface, some reflected, and infrared radiation absorbed and reradiated by the atmosphere.

Greenhouse effect on Earth

The greenhouse effect on Earth. Some incoming sunlight is reflected by Earth's atmosphere...

Encyclopædia Britannica, Inc.

Ozone depletion

Ozone depletion

Antarctic ozone hole, September 17, 2001.

NASA/Goddard Space Flight Center

Flue gas desulfurization (FGD) limestone wet scrubber

Flue gas desulfurization (FGD) limestone wet scrubber

Wet scrubber using a limestone slurry to remove sulfur dioxide from flue gas.

Encyclopædia Britannica, Inc.

Diagram showing how radon gas can enter a home through cracks in the floor, slab joints, hollow-block walls, drains, and around water supply pipes.

Indoor air pollution: radon

Radon is a colorless and odorless radioactive gas that can enter homes in a number...

Encyclopædia Britannica, Inc.

Thick smoke billows from an industrial smokestack, spreading across the sky and blending with clouds.

air pollution

Air pollution emitting from an industrial smokestack. The pollutants released into...

© Photos.com/Getty Images Plus

Figure 10: Air pollution injury to vegetation.

Figure 10: Air pollution injury to vegetation.

ARS/USDA

Interactives

World map shaded to show annual carbon dioxide emissions by country in 2022, with China, the United States, and India highlighted as top emitters in dark red. A bar chart below lists the top ten emitting countries by million metric tons.

Carbon dioxide emissions

Map of annual carbon dioxide emissions by country in 2014.

Encyclopædia Britannica, Inc.

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