how is nitrogen harmful and / or helpful in the human body?

Answer 1

Bubbles of N2 gas in the blood stream cause the bends in divers (Decompression sickness). Nitrites and nitrates can both be toxic to humans and animals.

Nitrogen is found in all protein and enzymes and in genetic material (RNA & DNA). Life would not be possible without nitrogen.

Look at the last reference for the Nitrogen cycle.

Answer 2

nitrogen harmful helpful human body

Answer 3

Helpful: it's in every single protein, piece of DNA, and almost every other molecule in your body except for fat and steroids.

Harmful: It's not really harmful, mostly because it's not something you can really get too much of, and most things are only harmful if you get too much of them. As a matter of fact, for many organisms nitrogen is the limiting nutrient (many bacteria and plants are limited in how much they grow by how much nitrogen they can get, which is why people use fertilizers, which are largely made up of nitrogen).

Learn more here: http://en.wikipedia.org/wiki/Nitrogen#Biological_role