Air Pollution in Medellin
It's sad how bad the air gets contaminated here in town. Especially when there are no windy days and / or rain to cleanse the air in the Valley.
You don't really realize how bad it is until you leave town. I went to Guatape for the weekend and you could see for miles in the crisp crystal clear air in the mountains.
Upon returning to town, you could see the smog sitting in the valley and the air smelled bad. I remember back in the Spring the air contamination was so bad that one week all of the public "Undiad Deportivas" sport complexes were closed for almost a week. It's even gotten so bad in the past they have even banned cars besides Pico and Placa and let everyone ride the METRO for free.
The majority of the air pollution comes from all of the vehicles. They require annual smog checks for all the vehicles here. However, their emission allowances are not as strict as many locales in the USA. They have a higher sulfer content in the gasoline here. So they are saving money by not having to refine the gasoline as much. They could help alleviate the problem by refining the gasoline more but it would increase the cost of gasoline substantially.
Additionally, the City has been putting in dedicated bike lanes all over the City to help go green. However, by doing so they have also taken away car lanes and as a result travel time by car and congestion has increased substantially in the areas with the dedicated bike lanes.