Photochemical smog has many names, including city smog or Los Angeles smog. Photochemical smog mainly consists of nitrogen oxides and hydrocarbon vapors that are emitted from cars and other industries. These chemicals react with sunlight in the lower atmosphere, which results in a thick, grey material that appears in the air. As a result of the fact that cars primarily produce photochemical smog, many call it Los Angeles smog because of the abundance of cars in this city.
Because photochemical smog surfaces in dense urban areas with lots of cars, it causes lots of health problems for individuals living in these urban areas. When the emitted chemicals combine, they form two gasses: ozone and nitrogen dioxide. Both of these gases are highly toxic and pose many problems for city-dwellers. They reduce visibility, which makes driving dangerous, and they can cause asthma and other breathing conditions.
Sulfurous smog, otherwise called London fog or industrial smog, was a major problem in the 1950s. During a period of widespread industrial expansion, London had numerous factories that burned coal along with other gases, which ultimately resulted in released sulfur dioxide into the air. As a result, the sulfur dioxide formed a huge cloud over London and caused a thick black discharge to blanket the city. In addition, it caused acid rain, or polluted rain, to fall on the city.
Because sulfurous smog blanketed cities with a black coating, major health problems resulted for London's citizens. The smog made it hard for citizens to breath and limited the amount of oxygen in the air. As a result, thousands of Londoners died, in addition to destroyed plant life and animals. Many consider this to be the deadliest environmental problem in recent history.