The phrase carbon footprint has passed easily into common usage, but now there's a new green measure to check how lightly you tread on the planet.
Scientists at the University of Virginia have produced a 'nitrogen footprint' calculator to raise awareness of an environmental problem little known outside specialist circles.
University of Virginia environmental scientist James N. Galloway; research assistant Allison Leach, worked with colleagues from the Netherlands and the University of Maryland to produce a means of measuring how much of the essential yet potentially problematic chemical we produce.
''Nitrogen, as any farmer knows, is essential to plant life,'' said Galloway, associate dean for the sciences in the College of Arts and Sciences at U.Va. and the Sidman P. Poole Professor of Environmental Sciences. ''But the widespread use of synthetic nitrogen fertilizer to boost crop production has resulted in excess nitrogen coming off farms - essentially adding unwanted, unneeded fertilizer to our natural systems, with disastrous results. The combustion of fossil fuels adds even more nitrogen to our environment. It's a largely untold story.''
It's a problem taken seriously by the US Government, which has spent hundreds of millions of dollars trying to reduce the impact of nitrogen runoff in the Chesapeake Bay where nitrogen build-ups have led to toxic algal blooms and hypoxic or dead zones where marine life is choked out of existence.
Visit www.n-print.org and you'll be able to calculate how much you're contributing to excess nitrogen and how you can do something to reduce your impact: measures which in the most part will be familiar with anyone trying to live more sustainably.
Galloway and Leach hope to raise awareness of the so-called ''Nitrogen dilemma'' - how to use this vital chemical without causing irreparable damage to our environment. As well as algal bloom, nitrogen is implicated in health problems, polluting water, attacking the ozone layer, air pollution and global warming.