The main nitrogenous waste in the human body is [A] Urea. Urea is formed in the liver during the breakdown of proteins and amino acids in a process called deamination. Ammonia, a highly toxic compound, is initially produced from the deamination process, but the liver converts it into urea, which is less toxic and more soluble in water. Urea is then transported through the bloodstream to the kidneys, where it is filtered out of the blood and excreted in urine. Uric acid, on the other hand, is a waste product of purine metabolism and is excreted by the kidneys in small amounts. Ammonium nitrate is not a naturally occurring waste product in the human body but rather a chemical compound used in fertilizers.