Water quality fact sheet: Nitrate

The primary health concern regarding nitrate and
nitrite is the formation of methaemoglobinaemia, so-
called ‘blue-baby syndrome’. Nitrate is reduced to
nitrite in the stomach of infants, and nitrite is able to
oxidize haemoglobin (Hb) to methaemoglobin
(metHb), which is unable to transport oxygen
around the body. This reduced oxygen transport
becomes clinically manifest when metHb
concentrations reach 10% or more of normal Hb
concentrations; the condition, called methaemo-
globinaemia, causes cyanosis and, at higher
concentrations, asphyxia.