Nitrate is inorganic nutrients used as fertilizer. Small amount of Glycerl trinintrate and its metabolites excreted by human won't cause any problem on environment. If large amount of nitrate is present in waterway, it can cause an undesirable proliferation of rooted aquatic plants and algae, and can lead to oxygen depletion. Some algae may also release toxic substances to the water. The drainage of fertilizers and other soil conditioners from agricultural fields to steams can cause such effects in downstream water and cause water pollution.

Algae on top of river	Fish die because of toxic algae bloom and the removal of oxygen as algal blooms decay

Nitrate isn't toxic to human and other animal. But foetus can easily get poisoning by nitrate. It is because nitrate V is converted to the toxic nitrate III ion in digestive system by bacteria. In normal case, the acidity of animal are high enough to destroy this bacteria but it isn't for foetus. If mother receives excess amount of nitrate, nitrate can pass through the placenta to poison the foetus. The animal born will be brownish colouration around the eyes and mouth or the mucous membranes. This is accompanied by a slow staggering gait, rapid heartbeat, frequent urination and laboured breathing. In severe case, it may lead to death.

 

Some studies showed that nitrate in drinking water can also cause diabetes in animal and has also been linked to stomach cancer, thyroid problems and birth defects.