Cubatao in Brazil was notorious for lethally high levels of air pollution, which led to malformations in newborn babies and widespread health problems.

But by the early 1990s, the city known as the "Valley of Death" had fought back, cutting pollution levels by 90%.

However, Cubatao is still among the most polluted cities in the region, and must work hard to maintain cleaner air.

Camilla Costa reports.

A week of coverage by BBC News examining possible solutions to the problems caused by air pollution.