NITRATES form when nitrogen from animal waste, fertilizers, septic systems, decaying plants, etc. combine with oxygenated water. Nitrates can cause methemoglobinemia (blue baby syndrome) in infants under 6 months old, a very serious condition which can lead to coma and death . In pregnant women, nitrates can reduce oxygen to the fetus. Nitrates can be eliminated from drinking water with a Reverse Osmosis Filter.