Smog is a type of air pollutant.
The word "smog" was made in the early 20th century as a portmanteau of the words smoke
and fog to refer to smoky fog.
The word was then intended to refer to what was sometimes known as pea soup fog, a familiar
and serious problem in London from the 19th century to the mid 20th century.
This kind of smog is caused by the burning of large amounts of coal within a city; this
smog contains soot particulates from smoke, sulfur dioxide and other components.
Modern smog, as found for example in Los Angeles, is a type of air pollution derived from vehicular
emission from internal combustion engines and industrial fumes that react in the atmosphere
with sunlight to form secondary pollutants that also combine with the primary emissions
to form photochemical smog.
The atmospheric pollution levels of Los Angeles, Mexico City and other cities are increased
by inversion that traps pollution close to the ground.
It is usually highly toxic to humans and can cause severe sickness, shortened life or death.
Etymology Coinage of the term "smog" is generally attributed
to Dr. Henry Antoine Des Voeux in his 1905 paper, "Fog and Smoke" for a meeting of the
Public Health Congress.
The July 26, 1905 edition of the London newspaper Daily Graphic quoted Des Voeux, "He said it
required no science to see that there was something produced in great cities which was
not found in the country, and that was smoky fog, or what was known as 'smog.'"
The following day the newspaper stated that "Dr. Des Voeux did a public service in coining
a new word for the London fog."
"Smog" also appears in a January 19, 1893, Los Angeles Times article and is attributed
to "a witty English writer."
Causes Coal
Coal fires, used to heat individual buildings or in a power-producing plant, can emit significant
clouds of smoke that contributes to smog.
Air pollution from this source has been report in England since the Middle Ages.
London, in particular, was notorious up through the mid-20th century for its coal-caused smogs,
which were nicknamed 'pea-soupers.'
Air pollution of this type is still a problem in areas that generate significant smoke from
burning coal, as witnessed by the 2013 autumnal smog in Harbin, China, which closed roads,
schools, and the airport.
Transportation emissions Traffic emissions – such as from trucks,
buses, and automobiles – also contribute.
Airborne by-products from vehicle exhaust systems cause air pollution and are a major
ingredient in the creation of smog in some large cities.
The major culprits are from transportation sources are carbon monoxide, nitrogen oxides,
volatile organic compounds, sulfur dioxide, and hydrocarbons.
These molecules react with sunlight, heat, ammonia, moisture, and other compounds to
form the noxious vapors, ground level ozone, and particles that comprise smog.
Photochemical smog Photochemical smog was first described in
the 1950s.
It is the chemical reaction of sunlight, nitrogen oxides and volatile organic compounds in the
atmosphere, which leaves airborne particles and ground-level ozone.
This noxious mixture of air pollutants can include the following:
Aldehydes Nitrogen oxides, such as nitrogen dioxide
Peroxyacyl nitrates Tropospheric ozone
Volatile organic compounds All of these harsh chemicals are usually highly
reactive and oxidizing.
Photochemical smog is therefore considered to be a problem of modern industrialization.
It is present in all modern cities, but it is more common in cities with sunny, warm,
dry climates and a large number of motor vehicles.
Because it travels with the wind, it can affect sparsely populated areas as well.
Natural causes An erupting volcano can also emit high levels
of sulphur dioxide along with a large quantity of particulate matter; two key components
to the creation of smog.
However, the smog created as a result of a volcanic eruption is often known as vog to
distinguish it as a natural occurrence.
The radiocarbon content of some plant life has been linked to the distribution of smog
in some areas.
For example, the creosote bush in the Los Angeles area has been shown to have an effect
on smog distribution that is more than fossil fuel combustion alone.
Health effects
Smog is a serious problem in many cities and continues to harm human health.
Ground-level ozone, sulfur dioxide, nitrogen dioxide and carbon monoxide are especially
harmful for senior citizens, children, and people with heart and lung conditions such
as emphysema, bronchitis, and asthma.
It can inflame breathing passages, decrease the lungs' working capacity, cause shortness
of breath, pain when inhaling deeply, wheezing, and coughing.
It can cause eye and nose irritation and it dries out the protective membranes of the
nose and throat and interferes with the body's ability to fight infection, increasing susceptibility
to illness.
Hospital admissions and respiratory deaths often increase during periods when ozone levels
are high.
Levels of unhealthy exposure The U.S. EPA has developed an Air Quality
Index to help explain air pollution levels to the general public.
8 hour average ozone concentrations of 85 to 104 ppbv are described as "Unhealthy for
Sensitive Groups", 105 ppbv to 124 ppbv as "unhealthy" and 125 ppb to 404 ppb as "very
unhealthy".
The "very unhealthy" range for some other pollutants are: 355 μg m−3 - 424 μg m−3
for PM10; 15.5 ppm - 30.4ppm for CO and 0.65 ppm - 1.24 ppm for NO2.
Premature deaths due to cancer and respiratory disease
The Ontario Medical Association announced that smog is responsible for an estimated
9,500 premature deaths in the province each year.
A 20-year American Cancer Society study found that cumulative exposure also increases the
likelihood of premature death from a respiratory disease, implying the 8-hour standard may
be insufficient.
Smog and the risk of certain birth defects A study examining 806 women who had babies
with birth defects between 1997 and 2006, and 849 women who had healthy babies, found
that smog in the San Joaquin Valley area of California was linked to two types of neural
tube defects: spina bifida, and anencephaly.
Smog and low birth weight According to a study published in The Lancet,
even a very small change in PM2.5 exposure was associated with an increase in risk of
a low birth weight at delivery, and this relationship held even below the current accepted safe
levels.
Areas affected
Smog can form in almost any climate where industries or cities release large amounts
of air pollution, such as smoke or gases.
However, it is worse during periods of warmer, sunnier weather when the upper air is warm
enough to inhibit vertical circulation.
It is especially prevalent in geologic basins encircled by hills or mountains.
It often stays for an extended period of time over densely populated cities or urban areas,
and can build up to dangerous levels.
United Kingdom London
In 1306, concerns over air pollution were sufficient for Edward I to ban coal fires
in London.
In 1661, John Evelyn's Fumifugium suggested burning fragrant wood instead of mineral coal,
which he believed would reduce coughing.
The Ballad of Gresham College the same year describes how the smoke "does our lungs and
spirits choke, Our hanging spoil, and rust our iron."
Severe episodes of smog continued in the 19th and 20th centuries, mainly in the winter,
and were nicknamed "pea-soupers".
The Great Smog of 1952 darkened the streets of London and killed approximately 4,000 people
in the short time of 4 days.
Initially a flu epidemic was blamed for the loss of life.
In 1956 the Clean Air Act started legally enforcing smokeless zones in the capital.
There were areas where no soft coal was allowed to be burned in homes or in businesses, only
coke, which produces no smoke.
Because of the smokeless zones, reduced levels of sooty particulates made the intense and
persistent London smog a thing of the past.
It was after this that the great clean-up of London began.
One by one, historical buildings which, during the previous two centuries had gradually completely
blackened externally, had their stone facades cleaned and restored to their original appearance.
Victorian buildings whose appearance changed dramatically after cleaning included the British
Museum of Natural History.
A more recent example was the Palace of Westminster, which was cleaned in the 1980s.
Smog caused by traffic pollution, however, does still occur in modern London.
Other areas Other areas of the United Kingdom were affected
by smog, especially heavily industrialised areas.
The cities of Glasgow and Edinburgh, in Scotland, suffered smoke-laden fogs in 1909.
Des Voeux, commonly credited with creating the "smog" moniker, presented a paper in 1911
to the Manchester Conference of the Smoke Abatement League of Great Britain about the
fogs and resulting deaths.
One Birmingham resident described near black-out conditions in the 1900s before the Clean Air
Act, with visibility so poor that cyclists had to dismount and walk in order to stay
on the road.
Mexico City, Mexico
Due to its location in a highland "bowl", cold air sinks down onto the urban area of
Mexico City, trapping industrial and vehicle pollution underneath, and turning it into
the most infamously smog-plagued city of Latin America.
Within one generation, the city has changed from being known for some of the cleanest
air of the world into one with some of the worst pollution, with pollutants like nitrogen
dioxide being double or even triple international standards.
Santiago, Chile Similar to Mexico City, the air pollution
of Santiago valley, located between the Andes and the Chilean Coast Range, turn it into
the most infamously smog-plagued city of South America.
Other aggravates of the situation reside in its high latitude and dry weather during most
of the year.
Tehran, Iran In December 2005, schools and public offices
had to close in Tehran, Iran and 1600 people were taken to hospital, in a severe smog blamed
largely on unfiltered car exhaust.
United States
Smog was brought to the attention of the general US public in 1933 with the publication of
the book "Stop That Smoke", by Henry Obermeyer, a New York public utility official, in which
he pointed out the effect on human life and even the destruction of 3,000 acres of a farmer's
spinach crop.
Since then, the United States Environmental Protection Agency has designated over 300
U.S. counties to be non-attainment areas for one or more pollutants tracked as part of
the National Ambient Air Quality Standards.
These areas are largely clustered around large metropolitan areas, with the largest contiguous
non-attainment zones in California and the Northeast.
Various U.S. and Canadian government agencies collaborate to produce real-time air quality
maps and forecasts.
Los Angeles and the San Joaquin Valley Because of their locations in low basins surrounded
by mountains, Los Angeles and the San Joaquin Valley are notorious for their smog.
The millions of vehicles in these regions combined with the additional effects of the
San Francisco Bay and Los Angeles/Long Beach port complexes frequently contribute to further
air pollution.
While strict regulations by numerous California government agencies overseeing this problem
have decreased the number of Stage 1 smog alerts from several hundred annually to just
a few, these geologically predisposed entrapment zones collect pollution levels from cars,
trucks and fixed sources which still exceeds health standards and is a pressing issue for
the more than 25 million people who live there.
Major incidents in the US 1948, October 30–31, Donora, Pennsylvania:
20 died, 600 hospitalized, thousands more stricken.
Lawsuits were not settled until 1951.
1953, November, New York: Smog kills between 170 and 260 people.
1954, October, Los Angeles: heavy smog shuts down schools and industry for most of the
month.
1963, New York: "a similar inversion" to London's 1962 "Killer Smog" is "blamed for 200 deaths."
1966, New York: smog is "blamed for 169 deaths."
Ulaanbaatar, Mongolia In the late 1990s, massive immigration to
Ulaanbaatar from the countryside began.
An estimated 150,000 households, mainly living in traditional Mongolian gers on the outskirts
of Ulaanbaatar, burn wood and coal to heat themselves during the harsh winter, which
lasts from October to April, since these outskirts are not connected to the city's central heating
system.
A temporary solution to decrease smog was proposed in the form of stoves with improved
efficiency, although with no visible results.
Coal-fired ger stoves release high levels of ash and other particulate matter.
When inhaled, these particles can settle in the lungs and respiratory tract and cause
health problems.
At two to 10 times above Mongolian and international air quality standards, Ulaanbaatar's PM rates
are among the worst in the world, according to a December 2009 World Bank report.
The Asian Development Bank estimates that health costs related to this air pollution
account for as much as 4 percent of Mongolia's GDP.
Southeast Asia
Smog is a regular problem in Southeast Asia caused by land and forest fires in Indonesia,
especially Sumatra and Kalimantan, although the term haze is preferred in describing the
problem.
Farmers and plantation owners are usually responsible for the fires, which they use
to clear tracts of land for further plantings.
Those fires mainly affect Brunei, Indonesia, Philippines, Malaysia, Singapore and Thailand,
and occasionally Guam and Saipan.
The economic losses of the fires in 1997 have been estimated at more than US$9 billion.
This includes damages in agriculture production, destruction of forest lands, health, transportation,
tourism, and other economic endeavours.
Not included are social, environmental, and psychological problems and long-term health
effects.
The second-latest bout of haze to occur in Malaysia, Singapore and the Malacca Straits
is in October 2006, and was caused by smoke from fires in Indonesia being blown across
the Straits of Malacca by south-westerly winds.
A similar haze has occurred in June 2013, with the PSI setting a new record in Singapore
on June 21 at 12pm with a reading of 401, which is in the "Hazardous" range.
The Association of Southeast Asian Nations reacted.
In 2002, the Agreement on Transboundary Haze Pollution was signed between all ASEAN nations.
ASEAN formed a Regional Haze Action Plan and established a co-ordination and support unit.
RHAP, with the help of Canada, established a monitoring and warning system for forest/vegetation
fires and implemented a Fire Danger Rating System.
The Malaysian Meteorological Department has issued a daily rating of fire danger since
September 2003.
Indonesia has been ineffective at enforcing legal policies on errant farmers.
Pollution index
The severity of smog is often measured using automated optical instruments such as Nephelometers,
as haze is associated with visibility and traffic control in ports.
Haze however can also be an indication of poor air quality though this is often better
reflected using accurate purpose built air indexes such as the American Air Quality Index,
the Malaysian API and the Singaporean Pollutant Standards Index.
In hazy conditions, it is likely that the index will report the suspended particulate
level.
The disclosure of the responsible pollutant is mandated in some jurisdictions.
The Malaysian API does not have a capped value; hence its most hazardous readings can go above
500.
Above 500, a state of emergency is declared in the affected area.
Usually, this means that non-essential government services are suspended, and all ports in the
affected area are closed.
There may also be prohibitions on private sector commercial and industrial activities
in the affected area excluding the food sector.
So far, state of emergency rulings due to hazardous API levels were applied to the Malaysian
towns of Port Klang, Kuala Selangor and the state of Sarawak during the 2005 Malaysian
haze and the 1997 Southeast Asian haze.
Cultural references
The London "pea-soupers" earned the capital the nickname of "The Smoke".
Similarly, Edinburgh was known as "Auld Reekie".
The smogs feature in many London novels as a motif indicating hidden danger or a mystery,
perhaps most overtly in Margery Allingham's The Tiger in the Smoke, but also in Dickens's
Bleak House and T.S.
Eliot's "The Love Song of J. Alfred Prufrock."
The 1970 made-for-TV movie A Clear and Present Danger was one of the first American television
network entertainment programs to warn about the problem of smog and air pollution, as
it dramatized a man's efforts toward clean air after emphysema killed his friend..
The history of smog in LA is detailed in Smogtown by Chip Jacobs and William J. Kelly.
See also 1997 Southeast Asian haze
2005 Malaysian haze 2006 Southeast Asian haze
2013 Harbin smog 2013 Eastern China smog
2013 Southeast Asian haze Atmospheric Chemistry
Contrail Criteria air contaminants
Emission standard Haze
Inversion effect Nitric oxide
Ozone Umweltzone
Vog Great Smog
References
External links Smog A Citizendium article
Eoearth.org, London Smog Disaster, Encyclopedia of Earth
NPI.gov.au, National Pollutant Inventory - Particulate matter fact sheet
Contrails.nl, Pictures of Contrails and Aviation Cirrus, since 1995 until now.
Ausetute.com.au, Photochemical Smog Iras.uu.nl, Airnet Workgroup Toxicology Report