Human activity is releasing far more reactive nitrogen than the Earth can safely absorb, damaging climate, biodiversity, human health, soils and oceans.

Nitrogen, as any diver can tell you, can be deadly – especially when it forms bubbles in the bloodstream and causes painful decompression sickness. Yet we breathe it in and out all our lives without ill effect.

However, this apparently innocuous substance, in its reactive forms, is now responsible for a global environmental disaster that is driving extinction, ruining our health, overheating the planet and killing the oceans.

The most terrifying feature of nitrogen pollution is that so few people realise it is happening – or that we ourselves are the main cause of it, through our eating, shopping and travel habits.

“Nitrogen pollution is causing an environmental catastrophe with devastating consequences for Planet Earth – yet the scale of the problem remains largely unknown outside of scientific circles,” warns the United Nations Environment Program (UNEP).

Furthermore, humans are releasing three times more nitrogen into the Earth system than it naturally circulates, inflicting a form of planetary poisoning outside the ken of most societies, industries and governments. According to the Potsdam and Stockholm Institutes, humans are releasing around 165 million tonnes of nitrogen a year into a biosphere which has a safe limit of 62 million tonnes. Of the ‘safe planetary boundaries’, it is the one we have transgressed the worst.

When people think about major pollutants that are changing the habitability of the Earth, the one that springs most readily to mind is carbon dioxide (CO2). Each year we add an........

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