University students protest against the 50th Annual Meeting...

University students protest against the 50th Annual Meeting of the Inter-American Development Bank in Medellin, Colombia, Thursday, March 26,2009.

Five models wearing gas masks pose for a photo as they protest worldwide pollution in Bogota, Wednesday, April 1, 2009.

A model walks her bicycle during a protest against worldwide pollution in Bogota, Wednesday, April 1, 2009.

Two models wearing gas masks ride bicycles during a protest against worldwide pollution as a man takes their picture in Bogota, Wednesday, April 1, 2009.

A police officer looks at a nude model wearing a gas mask as she protests worldwide pollution in Bogota, Wednesday, April 1, 2009.