Nitrate is a compound formed from nitrogen and oxygen. Although nitrogen in many compounds is essential for life on Earth, excessive amounts of nitrates can be hazardous for plants and humans. This graphic shows how nitrogen is transformed into nitrates.
Tens of thousands of cargo ships will have to start using less polluting fuels in January, a boon for the environment that could however lead to higher bills for consumers
Moving cargo ships into the slow lane, an idea French President Emmanuel Macron floated at the G7 summit, would be one way to cut maritime transport's giant carbon footprint
Taxes on products considered polluting are struggling to gain ground in the EU despite backing from Brussels, in the face of opposition from movements like France's "Yellow Vests".
Electric vehicles took centre stage at this year's Geneva Motor Show, as automakers scrambled to bring their fleets into line with strict CO2 emissions standards set to kick in next year.