Pollution can take many forms.
Air, water, solid waste - most agree that pollution is harmful for people and other life on Earth. But more controversial is how to best prevent it - and clean it up.
In Europe, about half of all new cars on the road run on diesel. But that's about to change. Diesel is out of favor, as it has turned out to be a major source of air pollution, far worse than cars that run on petrol. Many European cities plan to ban diesel cars within the next decade, amongst them the Spanish capital, Madrid.
Mexico City is notorious for traffic congestion and high levels of smog and noise pollution. One effort to tackle this problem involves electric scooters. Econduce is a privately-run pioneer scooter sharing scheme. It was the first scheme of this sort in Latin America, and is one of a select few worldwide. Since its launch, it has grown quickly. But can it really help fix the city's problems?