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.
How Germany's industrial heartland became a center for environmental projects and Europe's Green Capital 2017, and how residents transformed a trash-strewn Rio slum into an oasis of green development. Plus, an African soccer legend is tackling plastic waste.