The devastating oil spill in the Gulf of Mexico has led us to consider the effects of oil contamination in other parts of the world. Nigeria's oil-rich Niger Delta is considered to be the world capital of oil pollution. But it's a violent place ? armed gangs attack people who work for the oil industry, kidnapping workers and blowing up pipelines ? and the area is under the control of the Nigerian military.
The BBC's Caroline Duffield has just got back from a reporting trip to the Niger Delta and shares her impressions from Lagos, Nigeria.