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.