Kalio Keturah Nicholas remembers the time she could eat fresh fish from the river behind her house in Port Harcourt, Nigeria.

Those times are now a distant memory as oil spills onto the shore and everything in sight is covered in a thick layer of black soot.

Residents blame illegal refining of crude oil as the leading cause of soot in the atmosphere.

But for Kalio, it's not just a question of cleanliness anymore - the oil and soot are seriously affecting her health.

Precious Ede, the chairman of a government committee tackling soot in the region, says that the government is using military officers to crack down on illegal refining of crude oil, and sensitising the public on the dangers of air pollution.

Produced by: Charles Mgbolu, Anne Okumu and Sam Agbaje