Sulfurous Smog

• Sulfurous smog (also called winter smog and London smog) was first noted in London during the industrial revolution. Sulfurous smog is a mixture of sulphur dioxide and smoke that is trapped by fog over cities during the winter months. Industrial Revolution-era households primarily used coal for cooking and heating, clogging the air with sulfurous smoke. Also, factories at the time did not have laws governing pollutant dispersion. Tougher emissions restrictions and modern technology means that sulfurous smog is no longer so prevalent.
  
  

Impact of Sulfurous Smog

• One well-known characteristic of sulfurous smog was its dense, dark haze, starkly impairing visibility in industrial cities during the 18th and early 19th centuries. Sulfurous smog in London at the time often grew so thick that seeing across the street was difficult to impossible on some days. The impact on the population's health has been well-documented, with cases of asthma, emphysema, bronchitis and severe lung infection cited during that time. In 1952, when automobiles became commonplace in the city, therefore adding to the deteriorating air conditions, a 5-day sulfurous smog was responsible for more than 4,000 deaths in the city of London.
  
  

Sulfurous Smog Control

• The 1952 tragedy prompted Great Britain to impose The Clean Air Act of 1956. The act moved factories from city centers to less populated areas and introduced the use of tall factory chimneys for better pollutant dispersion. It also imposed smokeless zones where only smokeless fuels could be burned and introduced cleaner fuels such as gas, electricity and cleaner coals for household use. Later in the United States, the Clean Air Act of 1963 gave the EPA the power to set limits on certain air pollutants and limit emissions from such industries as steel mills and utility plants.
  
  

Photochemical Smog

• Most of today's smog is photochemical smog (also called summer smog and Los Angeles smog.) Caused by the reaction of sunlight to such pollutants as nitrogen oxides and hydrocarbons, photochemical smog can be a problem for all major cities, but primarily those with warm, dry climates where the chemical reaction creating ozone gas is most likely to occur. The problem is often exacerbated in cities surrounded by hills or mountains where less air circulation occurs.
  
  

Impact of Photochemical Smog

• Photochemical smog often creates a white or brownish haze, usually noticeable during morning hours. Physically, it causes headaches, eye irritation, coughing, wheezing and impaired lung function. It deteriorates fabrics and rubber, and damages plants, as well.
  
  

Photochemical Smog Control

• Since the harmful gasses of photochemical smog are emitted atmospherically, controlling them is more difficult than controlling those of sulfurous smog. One way to do so is by controlling vehicle emissions through the use of catalytic converters and cleaner burning fuels. Industrial emissions are also controlled by governments across the globe, though some environmental groups claim that tougher regulations need to be in place.