The science of smog - Kim Preshoff

Summary

In July 1943, Los Angeles experienced a mysterious smog event, causing panic among residents. Chemist Arie Haagen-Smit identified the cause as a reaction between volatile organic compounds (VOCs) and nitrogen oxides under sunlight, leading to photochemical smog. This type of smog, exacerbated by weather and geography, particularly affects cities like LA and Beijing. Smog poses serious health risks and environmental damage. The Great Smog of London in 1952 prompted the Clean Air Act, reducing smog. Regulations on emissions have since helped, but smog remains a global challenge, especially in developing cities and coal-dependent countries.

Takeaways

• 🌁 The term 'smog' originated in the early 20th century to describe the industrial haze affecting cities like London, Glasgow, and Edinburgh.
• 🔍 The Los Angeles smog of 1943 was unique, being yellowish with a chemical odor, and was later attributed to volatile organic compounds (VOCs) and nitrogen oxides.
• 🌞 Photochemical smog is formed when VOCs and nitrogen oxides react with sunlight, leading to the creation of pollutants like PANs and ground-level ozone.
• 🏙️ The formation of smog is influenced by both human activities and local weather and geography, with cities surrounded by mountains or in basins being particularly vulnerable.
• ☀️ Sunlight plays a crucial role in the formation of photochemical smog by providing the energy needed to break down molecules that contribute to smog.
• 🌡️ Temperature inversion can trap polluted air near the surface, exacerbating smog conditions in certain areas.
• 🤧 Smog has significant health impacts, irritating eyes, nose, and throat, and increasing the risk of respiratory infections and conditions like asthma and emphysema.
• 🌾 Secondary pollutants in photochemical smog can also damage crops, affecting agricultural yields and making plants more susceptible to pests.
• 🚫 The Great Smog of London in 1952 led to the implementation of the Clean Air Act of 1956, which significantly reduced smog by banning coal burning in certain areas.
• 🛑 Regulations on vehicle emissions and gas content in the US have helped to reduce the levels of volatile compounds and smog.
• 🌍 Smog remains a global issue, particularly in countries that rely on coal for energy and in rapidly developing cities affected by vehicle emissions.

Q & A

What unusual event occurred in Los Angeles on July 26, 1943?

On July 26, 1943, Los Angeles was covered by a thick gas that caused eye irritation and blocked out the Sun, leading to panic among residents who initially thought their city was under a chemical warfare attack.

What is the origin of the term 'smog'?

The term 'smog' is a portmanteau of 'smoke' and 'fog' and was coined at the beginning of the 20th century to describe the thick gray haze that covered industrial cities such as London, Glasgow, and Edinburgh.

What are the two main components that Arie Haagen-Smit identified as the cause of the Los Angeles smog?

Arie Haagen-Smit identified volatile organic compounds (VOCs) and nitrogen oxides as the two main components causing the Los Angeles smog.

What are VOCs and what are their sources?

Volatile Organic Compounds (VOCs) are compounds that easily become vapors and may contain elements such as carbon, oxygen, hydrogen, chlorine, and sulfur. They are naturally produced by plants and animals, but also come from manmade sources like solvents, paints, glues, and petroleum.

How are nitrogen oxides related to the formation of smog?

Nitrogen oxides are released from the incomplete combustion of gas in motor vehicles and react with VOCs in the presence of sunlight to produce secondary pollutants that contribute to the formation of photochemical smog.

What are PANs and tropospheric ozone, and what effects do they have on health?

PANs (Peroxyacetyl Nitrates) and tropospheric or ground-level ozone are secondary pollutants produced by the reaction of VOCs and nitrogen oxide with sunlight. They cause eye irritation, damage lung tissue, and are key components of photochemical smog.

Why do some cities experience more smog than others?

Smog is influenced by a combination of manmade pollution, local weather, and geography. Factors such as high humidity, calm winds, and dry, warm, sunny weather, as well as geographical features like mountains or basins, can make some cities more susceptible to smog.

What is a temperature inversion, and how does it contribute to smog?

A temperature inversion is a phenomenon where a layer of warm air traps cooler, pollution-filled air near the Earth's surface, preventing it from rising and dissipating. This can exacerbate smog conditions by keeping pollutants concentrated at ground level.

What are the health risks associated with smog exposure?

Smog exposure can irritate the eyes, nose, and throat, exacerbate conditions like asthma and emphysema, increase the risk of respiratory infections, and has been linked to low birth weight and potential birth defects in pregnant women.

How did the Great Smog of London in 1952 impact policy changes?

The Great Smog of London in 1952 led to the implementation of the Clean Air Act of 1956, which banned the burning of coal in certain areas of the city, resulting in a significant reduction in smog.

What measures have been taken globally to combat smog?

Governments have implemented various measures such as regulating vehicle emissions, controlling gas content, and in some cases, temporarily banning cars from driving. A shift towards mass transit and away from fossil fuels is also being considered to reduce smog levels.

Outlines

00:00

🌁 The Mystery of LA's Yellow Smog

On July 26, 1943, Los Angeles was enveloped in a yellowish smog with a chemical odor, causing panic among residents who feared a chemical attack. This type of smog, later known as photochemical smog, was different from the industrial smog of cities like London, which was caused by coal burning. Arie Haagen-Smit identified the main components of this smog as volatile organic compounds (VOCs) and nitrogen oxides, which react with sunlight to produce pollutants like PANs and ground-level ozone. These pollutants are harmful to human health, causing eye irritation and lung damage. The formation of smog is influenced by a combination of manmade pollution and local weather conditions, with cities like LA and Beijing being particularly vulnerable due to their geographical features and weather patterns.

Keywords

💡Smog

Smog is a type of air pollution characterized by a thick, hazy mixture of smoke and fog. It is a central theme of the video, illustrating the historical and environmental challenges of urban areas. In the script, smog is described as having caused panic in Los Angeles in 1943, and it is also used to discuss the broader issue of air quality in cities around the world.

💡Arie Haagen-Smit

Arie Haagen-Smit was a chemist who is credited with identifying the main components of the smog that affected Los Angeles in the 1940s. His research is a key part of the video's narrative, as it helped to understand and address the causes of smog, specifically the role of volatile organic compounds (VOCs) and nitrogen oxides.

💡Volatile Organic Compounds (VOCs)

VOCs are a group of carbon-containing chemicals that easily evaporate at room temperature. In the context of the video, VOCs are one of the primary contributors to the formation of photochemical smog. They are emitted from various sources, including solvents, paints, and petroleum, and their presence in the atmosphere is highlighted as a significant environmental concern.

💡Nitrogen Oxides

Nitrogen oxides are a family of gases that include nitrogen dioxide and nitric oxide. The script explains that these gases are released from the incomplete combustion of gas in motor vehicles and are a key component in the formation of photochemical smog, giving it a yellowish color and contributing to its harmful effects on health and the environment.

💡Photochemical Smog

Photochemical smog is a specific type of smog that forms when sunlight reacts with pollutants like VOCs and nitrogen oxides in the atmosphere. The video emphasizes its harmful effects, such as eye irritation and lung damage, and discusses how it is particularly problematic in urban areas with certain weather conditions and geographical features.

💡PANs (Peroxyacetyl Nitrates)

PANs are secondary pollutants that form as a result of the reaction between VOCs and nitrogen oxides in the presence of sunlight. The script mentions PANs as part of the photochemical smog composition, contributing to its harmful effects on human health and the environment.

💡Tropospheric Ozone

Tropospheric ozone, also known as ground-level ozone, is a harmful air pollutant that forms from the reaction of sunlight with VOCs and nitrogen oxides. The video script describes it as a key ingredient in photochemical smog and highlights its role in causing respiratory problems and other health issues.

💡Temperature Inversion

Temperature inversion is a meteorological phenomenon where a layer of warm air traps cooler air, preventing pollutants from rising and dispersing. The script explains how this phenomenon contributes to the persistence of smog in certain cities, particularly those surrounded by mountains or located in basins.

💡Clean Air Act of 1956

The Clean Air Act of 1956 was a significant piece of legislation in the United Kingdom aimed at reducing air pollution, particularly from coal burning. The video script uses this act as an example of successful policy measures to combat smog and improve air quality, following the devastating Great Smog of London in 1952.

💡Vehicle Emissions

Vehicle emissions refer to the gases and particles released by motor vehicles, which contribute to air pollution. The script discusses how regulations on vehicle emissions have been implemented to reduce the levels of VOCs and other pollutants, thereby addressing the issue of smog in urban areas.

💡Mass Transit

Mass transit is a collective term for transportation services that are designed to move large numbers of people, such as buses, trains, and subways. The video suggests that a shift towards mass transit, as opposed to individual car usage, could be a solution to reducing air pollution and smog, especially in densely populated urban areas.

Highlights

On July 26, 1943, Los Angeles experienced a smog event that caused panic among residents, who believed they were under chemical attack.

The term 'smog', a combination of smoke and fog, was coined in the early 20th century to describe the haze covering industrial cities like London and Glasgow.

Industrial smog was formed by the combination of smoke from coal-burning stoves and factories with atmospheric moisture.

The Los Angeles smog of 1943 was different, being yellowish with a chemical odor, and was not caused by coal burning.

Arie Haagen-Smit identified the main causes of the Los Angeles smog as volatile organic compounds (VOCs) and nitrogen oxides.

VOCs are compounds that easily vaporize and can come from both natural and manmade sources, such as solvents and paints.

Nitrogen oxide is released from the incomplete combustion of gas in motor vehicles, giving smog a yellowish color.

VOCs and nitrogen oxide react with sunlight to produce secondary pollutants like PANs and ground-level ozone, which are key components of photochemical smog.

Photochemical smog causes eye irritation, lung tissue damage, and exacerbates respiratory conditions like asthma and emphysema.

Factors like local weather, geography, and calm winds contribute to the formation and persistence of smog in urban areas.

Cities surrounded by mountains or located in basins, like Los Angeles and Beijing, are particularly vulnerable to smog due to limited dispersal.

Temperature inversion, where a warmer layer of air traps pollution near the surface, contributes to smog persistence.

Smog has significant health impacts, especially on vulnerable populations like young children, older people, and pregnant women.

Secondary pollutants in photochemical smog can damage crops, decrease yield, and increase susceptibility to insects.

The Great Smog of London in 1952 led to the Clean Air Act of 1956, which significantly reduced smog by banning coal burning in certain areas.

Regulations on vehicle emissions and gas content in the US have helped reduce air pollution and smog levels.

Smog remains a major global issue, especially in countries that rely on coal for energy and in rapidly developing cities affected by vehicle emissions.

Governments have implemented various measures to tackle smog, including temporary car driving bans.

A shift to mass transit and away from fossil fuels may help alleviate smog issues as urban populations continue to grow.

Transcripts

On July 26, 1943,

Los Angeles was blanketed by a thick gas that stung people's eyes

and blocked out the Sun.

Panicked residents believed their city had been attacked using chemical warfare.

But the cloud wasn't an act of war.

It was smog.

A portmanteau of smoke and fog,

the word "smog" was coined at the beginning of the 20th century

to describe the thick gray haze that covered cities

such as London,

Glasgow,

and Edinburgh.

This industrial smog was known to form

when smoke from coal-burning home stoves and factories

combined with moisture in the air.

But the smog behind the LA panic was different.

It was yellowish with a chemical odor.

Since the city didn't burn much coal, its cause would remain a mystery

until a chemist named Arie Haagen-Smit identified two culprits:

volatile organic compounds, or VOCs,

and nitrogen oxides.

VOCs are compounds that easily become vapors

and may contain elements, such as carbon,

oxygen,

hydrogen,

chlorine,

and sulfur.

Some are naturally produced by plants and animals,

but others come from manmade sources,

like solvents,

paints,

glues,

and petroleum.

Meanwhile, the incomplete combustion of gas in motor vehicles

releases nitrogen oxide.

That's what gives this type of smog its yellowish color.

VOCs and nitrogen oxide react with sunlight

to produce secondary pollutants called PANs and tropospheric,

or ground-level, ozone.

PANs and ozone cause eye irritation and damage lung tissue.

Both are key ingredients in photochemical smog,

which is what had been plaguing LA.

So why does smog affect some cities but not others?

Both industrial and photochemical smog combine manmade pollution

with local weather and geography.

London's high humidity made it a prime location for industrial smog.

Photochemical smog is strongest in urban areas with calm winds

and dry, warm, sunny weather.

The ultraviolet radiation from sunlight provides the energy necessary

to breakdown molecules that contribute to smog formation.

Cities surrounded by mountains, like LA,

or lying in a basin, like Beijing,

are also especially vulnerable to smog since there's nowhere for it to dissipate.

That's also partially due to a phenomenon known as temperature inversion,

where instead of warm air continuously rising upward,

a pollution-filled layer of air remains trapped near the Earth's surface

by a slightly warmer layer above.

Smog isn't just an aesthetic eyesore.

Both forms of smog irritate the eyes,

nose,

and throat,

exacerbate conditions like asthma and emphysema,

and increase the risk of respiratory infections like bronchitis.

Smog can be especially harmful to young children and older people

and exposure in pregnant women has been linked to low birth weight

and potential birth defects.

Secondary pollutants found in photochemical smog

can damage and weaken crops and decrease yield,

making them more susceptible to insects.

Yet for decades, smog was seen as the inevitable price of civilization.

Londoners had become accustomed to the notorious pea soup fog

swirling over their streets until 1952,

when the Great Smog of London shut down all transportation in the city for days

and caused more than 4,000 respiratory deaths.

As a result, the Clean Air Act of 1956

banned burning coal in certain areas of the city,

leading to a massive reduction in smog.

Similarly, regulations on vehicle emissions and gas content in the US

reduced the volatile compounds in the air and smog levels along with them.

Smog remains a major problem around the world.

Countries like China and Poland that depend on coal for energy

experience high levels of industrial smog.

Photochemical smog and airborne particles from vehicle emissions

affect many rapidly developing cities,

from Mexico City and Santiago

to New Delhi and Tehran.

Governments have tried many methods to tackle it,

such as banning cars from driving for days at a time.

As more than half of the world's population crowds into cities,

considering a shift to mass transit and away from fossil fuels

may allow us to breathe easier.