Are London fogs high in calories?

London fog, also known as pea soup fog, is a type of dense fog that is a mix of both fog and industrial pollution that used to commonly affect London, England before clean air legislation improved air quality. This thick smog would hang over London for days, sometimes even weeks during the winter months. But how many calories does inhaling this fog contain? Are London fogs actually high in calories?

What are London Fogs?

London fogs are dense, smoggy fogs that were caused by a combination of natural fog and excessive coal burning from homes and industries. This smoggy fog gave London the nickname “The Big Smoke.” The cold, stagnant air over London trapped the pollution and fog close to the ground, creating a thick, yellow-brown, acrid smog that reduced visibility to just a few feet. This toxic smog caused issues for traffic, health problems like bronchitis, and even fatalities from asphyxiation or lung issues. London fogs first became problematic in the early 1800s during the Industrial Revolution. At their worst during the lethal Great Smog of 1952, visibility was so poor that London transit shut down, and it’s estimated that 12,000 people died from exposure effects.

What Causes London Fog?

There are two key components that created the dense London fogs of yesteryear:

  • Natural fog formation from weather conditions
  • Large amounts of pollution, primarily from coal burning

Cooler fall and winter months in London frequently see fog formation due to moisture condensing in colder air. While regular fog would reduce visibility, it typically wouldn’t linger for extended periods of time or mix with pollution to become the even denser pea soup fogs London was known for.

The key ingredient was massive amounts of pollution, primarily from coal burning. In Victorian era London, coal was heavily used to heat homes and power industries. Coal burning releases smoke filled with soot, ash, sulfur dioxide, and other particles and gases. With millions of Londoners burning coal daily, especially in the cooler months, large quantities of coal smoke polluted the air.

When natural fog formed in the cooler air, it trapped all this pollution close to the ground, creating a dense toxic mix that reduced visibility to dangerous levels. So it’s the combination of naturally occurring fog and large quantities of man-made pollution that created the noxious smog mix known as London fog.

When Did London Fogs Occur?

London fogs were at their worst during the 19th and early 20th century. Some key facts about when London fogs occurred:

  • Early 1800s – London fog problems start as coal use increases in the growing city
  • 1873 – The term “pea souper” is first used to describe London fog conditions
  • 1880-1883 – Multiple severe fogs; visibility under 10 feet for up to 9 days straight
  • 1892 – One of the worst fogs covers London for a week, killing hundreds
  • 1912 – Over a thousand Londoners die in a week-long fog
  • 1952 – The Great Smog kills 12,000 Londoners in 5 days
  • 1962 – London’s last severe fog occurs before laws curb pollution

So while London had experienced issues with foggy conditions back into the Middle Ages, the 19th century saw fog problems worsen exponentially as London’s population and industry grew. Long-lasting, high casualty fogs continued occurring into the 1950s, until change finally came after the devastating Great Smog of 1952 galvanized cleanup efforts.

Health Effects of London Fog

When you inhale irritating sulphur dioxide, coal particulates, ash, and other noxious substances, it’s not surprising the dense toxic soup of a London fog caused numerous health issues:

  • Respiratory Problems – Coughing, chronic bronchitis, pneumonia, tuberculosis
  • Lung Damage – Scarring, shortness of breath, decreased function
  • Heart Issues – Strain from lack of oxygen, cardiac arrest, heart attacks
  • Asphyxiation – The fog could smother and suffocate people to death
  • Cancer – Lung and other cancers from toxins and coal tars
  • Excess Deaths – Tens of thousands of deaths attributed to fog exposure

The sulfur dioxide and other pollutants literally poisoned people as they walked through the foggy streets of London. Those with pre-existing health conditions were especially vulnerable. The tragic amount of excess deaths during fog events shows just how deadly breathing the toxic air could be. Chronic health issues also plagued survivors for years after exposure.

How Has London Fog Changed Over Time?

While progress was slow, change did finally come in the mid-1900s to clear the London air. Here are some key improvements over time:

  • 1940s-1950s – Switch from coal gas to cleaner natural gas for home heating
  • 1956 – Clean Air Act passes after 1952 Great Smog, regulates emissions
  • 1960s – Further emission laws target industries and reduce coal burning
  • Present Day – Air quality vastly improved from 50+ years of clean air laws

Today, while an occasional light mist might obscure visibility, true dense London fogs have disappeared after over a century of fatally foul air. Thanks to elimination of coal burning, clean fuel requirements, and emission standards, London air is far cleaner and safer to breathe.

Do London Fogs Contain Calories?

Now that we’ve reviewed what exactly London fog consists of, let’s examine the key question: do these toxic fogs actually contain calories that someone could ingest by breathing them in? Could simply walking through old London streets laden with smog mean you were inhaling thousands of calories with each breath?

Calories and Nutrition

First, let’s cover some basics on calories and where they come from. Calories refer to the energy stored in food, which the body can convert into energy. The average adult requires around 2000-2500 calories per day from their diet to energize the body’s processes. Calories are found in:

  • Carbohydrates – 4 calories per gram
  • Protein – 4 calories per gram
  • Fat – 9 calories per gram

Your body digests food, breaks it down into basic components like glucose and fatty acids, then absorbs these to provide usable energy in the form of calories. So for something to contain calories, it must have calorie-containing compounds like carbohydrates, fats, or proteins that can be converted to energy.

London Fog Composition

Recall that London fog is a mix of natural fog and air pollution, primarily:

  • Nitrogen oxides
  • Sulfur oxides
  • Coal smoke and particulates
  • Ash
  • Soot

None of these contain any carbohydrates, proteins, fats, or other compounds that can provide calories. While inhaling fog droplets allows a small amount of water into your lungs, the pollution components are irritants, toxins, and particulate matter – none of which have caloric content.

Can Inhaling Provide Calories?

Another key fact is that you need to ingest and digest something for it to deliver calories. Simply inhaling a substance does not provide usable energy for the body. Anything inhaled is not passed through the digestive system, so it cannot be broken down into nutrients absorbed by the body. No absorption = no calories.

The lungs’ purpose is simply to pass oxygen into the bloodstream while removing carbon dioxide. They do not absorb or digest material in a way that provides calories or nutrition. So even if the London fog did contain calorie sources like carbohydrates or fat, inhaling it would not impart those calories to your body. Only ingested/digested material can provide calories.

Calorie Content of Air

Normal air contains:

  • 78% nitrogen
  • 21% oxygen
  • Small amounts of argon, carbon dioxide, and other gases

There are no carbohydrates, fats, proteins, or other calorie sources in clean air. Air does not contain nutrients or calories. While oxygen is vital for life, inhaling oxygen does not provide energy in the form of calories. Any additional pollutants in London fog just added toxicity – not additional calories.

Why Do People Think London Fog Has Calories?

If London fog clearly doesn’t contain any calories, why is there confusion and this myth that heavy fog provides energy you can inhale? There are a few possible reasons behind the caloric fog misconception.

Calories From Eating vs. Inhaling

One issue is that people associate the concept of calories with any kind of intake, without considering the difference between ingesting and inhaling. Yes, the body can get energy from calories in food you ingest. However, calories do not transfer over to substances inhaled into the lungs. Somewhere along the way, the idea of fog providing calories may have arisen from a mistaken linkage between breathing air and eating food as similar forms of intake.

Hunger and Appetite Effects

Inhaling cold, moist air has actually been shown to slightly increase hunger levels and appetite. Even without calories, some signally from the lungs to the brain may make you feel like eating. This effect might have led to the notion that heavy fog provides energy and calories since people feel hungrier after being out in it. However, the studies showing this appetite increase did not find any actual caloric load being imparted.

Misconceptions Around Air

Since air is invisible, intangible, and its composition poorly understood by the average person, it can be easy to develop misconceptions around components found in air. The notion may have formed that thick heavy fog contains higher levels of oxygen, nutrients, or other substances that impart energy when inhaled. But in reality, even dense pure fog contains just water and clean air components like nitrogen – no added calories.

Creative License

Artistic license could also be one origin of the caloric fog myth. Novelists or other writers lyrically describing characters out in the fog may have figuratively referred to them as “inhaling sustenance” or similar. If interpreted too literally, this could have spawned the idea that fog provides actual calories and energy.Creative metaphors can sometimes take on a factual air if their context is lost.


So in summary, while London’s fogs were dense, toxic hazards, their dangers came from pollution – not calories. Key points:

  • London fog contains no digestible calorie sources like carbohydrates, protein or fat
  • Inhaling cannot provide calories – only ingested food can deliver energy
  • Air, oxygen, and other gases do not contain calories
  • Appetite changes from fog exposure don’t impart actual calories

While it may seem like London air was thick enough to chew on during the worst fogs, the smoggy mix itself provided no nutritional value or calories. The myth likely arose from creative license or misapplied knowledge around ingestion vs inhalation. So next time you’re out in the fog, rest assured that the only calories you’ll get come from stopping to enjoy hot soup, a hearty sandwich, or another filling meal!

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