"Nitrogen pollution"
I am really, really hoping this is a joke.
Related science fact: Elemental nitrogen is a mostly inert gas that comprises 78 percent of the air we breath every day. Nitrogen compounds are building blocks of life at every level. The entire history of rotation farming is designed to try and get nitrogen into the soil. Where I grew up, ammonia tanks for fertilizer use were as common parked near our town as pickup trucks.
What's next?