Smog is a type of air pollution formed by a combination of smoke and fog. It occurs when there are high levels of air pollution, especially in densely populated cities where there is substantial transport and factory pollution. Smog can build up to dangerous levels in cities and remain in the air for long periods of time. Some cities known for smog issues include London, New York, Los Angeles, Mexico City, and many large cities in Southeast Asia. The causes of smog include the burning of fossil fuels for transportation and industry as well as chemical manufacturing. Health hazards from smog include breathing issues, cancer, and death from long term exposure. Solutions to reduce smog involve limiting pollution emissions and promoting alternatives to reduce vehicle usage

2. Smog is a type of air pollution. The word smog comes from the blend of two words, smoke and fog. Smog can form in any climate where there is a lot of air pollution especially in cities where this is substantial amount of transport and factory pollution. Smog stays for a long period of time in a densely populated city or urban areas such as London, New York, Los Angeles, São Paulo, Mexico City, Houston, Toronto, Athens, Beijing, Hong Kong and Seoul can build up to dangerous levels. effect Problems with smog before 2008 Olympics, China This photo was taken early in the morning, just before the morning rush hour in Beijing

3. LONDON London is known for its smog since the roman times. This city is also known for ‘Great smog in London’ which happened in 1952 , where 4,000 people were approximately killed. The current condition in London is better than 1952, but there is still a substantial amount. MEXICO CITY Since Mexico is located in the highlands the cold air drops into the urban areas trapping all the industrial and transport pollution under it. This has caused Mexico to be one of the most famous smog countries. LOS ANGELES Being surrounded by mountains Los Angeles is quite similar to Mexico. One main reason for this smog is because of the millions of vehicles in the city and the lack of public transport and the people’s preference of a private transport. The Great Smog in London

4. SOUTHEAST ASIA Smog is very common in this part of Asia, usually caused by forest fires in Indonesia. The farmers are often responsible for these fires since they need more land to farm on. This effects other countries like Brunei, Singapore, Philippines and Thailand. The southwesterly winds blow the smoke across the Straits of Malacca into these countries. Left- air on a day after rain. Right- air before the rain

6. EPA, Air and Radiation, visited on 23 rd September, http://www.epa.gov/air/basic.html Caroline, The Environment, A Global Challenge, copyright 1999 http://library.thinkquest.org/26026/Environmental_Problems/smog.html http://en.wikipedia.org/wiki/Smog, 23 rd September