Blue Baby Syndrome is caused by the contamination of nitrite (NO_{2^{-}}). High nitrate levels in ground water can cause methemoglobinaemia or blue baby syndrome, a condition found especially in infants less than six months. The stomach acid of an infant is not as strong as in older children and adults. This causes an increase in bacteria that can readily convert nitrate to nitrite (NO2). Nitrite is absorbed in the blood forming methaemoglobin leading to reduced oxygen supply to vital tissues such as the brain.