AIR POLLUTION

 SMOG

Smog is a type of intense air pollution. The word 

"smog" was coined in the early 20th century, and is contraction (portmanteau) of the words smoke and fog to refer to smoky fog due to its opacity, and odor.The word was then intended to refer to what wassometimes known as pea soup fog, a familiar and serious problem in London from the 19th century to the mid-20th century. This kind of visible air pollution is composed of nitrogen oxides, sulphur oxides, ozone, smoke and other particulatesderived from coal combustion emissions, vehicular emissions, industrial emissions, forest and agricultural fires and photochemical reactions of these emissions.

Smog is often categorized as being either summer smog or winter smog. Summer smog is primarily associated with the photochemical formation of ozone. During the summer season when thetemperatures are warmer and there is more sunlight present, photochemical smog is the dominant type ofsmog formation.

 During the winter months when the temperatures are colder, and atmospheric inversions are common, there is an increase in coal and other fossil fuel usage to heat homes and buildingsPrimary pollutants are emitted directly from a source,such as emissions of sulfur dioxide from coal combustion. Secondary pollutants, such as ozone, areformed when primary pollutants undergo chemical reactions in the atmospherePhotochemical 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. These pollutants react in the atmosphere with sunlight to form secondary pollutants that also combine with the primary emissions to form photochemical smog. In certain other cities, such as Delhi, smog severity is often aggravated by stubble burning in neighboringagricultural areas. The atmospheric pollution levels ofLos Angeles

Delhi

, Lahore, Mexico City, Tehran and other cities are often increased by an inversion that traps pollution close to the ground. The developing smog is usually toxic to humans and can cause severe sickness, a shortened life span, or premature death.

Causes

1)Coal=Coal fires can emit significant clouds of smoke that contribute to the formation of winter smog.

 London, in particular, was notorious up through the mid-20th century for its coal-caused smogs, which were nicknamed 'pea-soupers.'

(One prominent example for this was China's 

Northeastern city of Harbin in 2013.)

 The emissions from coal combustion are one of the main causes of air pollution in China.[7] Especially during autumn and winter when coal-fired heating ramps up, the amount of produced smoke at timesForces some Chinese cities to close down roads, schools or airports.

2)Transportation emissions=#Traffic emissions – suchas from trucks, buses, and automobiles– also contribute to the formation of smog.

 #sources are carbon monoxide (CO),] nitrogen oxides (NO and NO2),[17] 

volatile organic compounds, and hydrocarbons (hydrocarbons are themain component of petroleum fuels such as gasoline and diesel fuel).

3)Photochemical smog=Photochemical smog, often referred to as "summer smog", is the chemical reaction of sunlight, nitrogenoxides and volatile organic compounds in the atmosphere, which leaves airborne particles and ground-level ozone

                     Natural causes

1)Volcanoes=An erupting volcano can emit high levels of sulfur dioxide along with a large quantity of  particulates 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. 

           Health effects

Smog is a serious problem in many cities and continues to harm human health.Ground-level ozone, sulphur 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.Hospital admissions and respiratory deaths often increase during periods when ozone levels are highHospital admissions and respiratory deaths oftenincrease during periods when ozone levels are high

( estimated 9,500 premature deaths in the province 

each year.2016)

Alzheimer riskRisk of certain birth defects(SPINA BIFIDA)

Low birth weight Areas affectedCanada Delhi India Beijing, China London MexicoCity, Mexico Santiago, Chile Tehran, Iran United States Los Angeles and the San Joaquin Valley Ulaanbaatar, MongoliaSoutheast Asia Pakistan