Correct Answer - Option 3 : > 50 ppm of nitrate
Concept:
According to EEC (European Environment Commission) excess of nitrate i.e. greater than 50 ppm in drinking water may lead to methemoglobinemia which is also called as blue baby syndrome. It may also cause stomach-cancer.
Methemoglobinemia may be acquired and caused by nitrates ingested in drinking water, dehydration (usually caused by gastroenteritis with diarrhoea), sepsis, or topical anaesthetics containing benzocaine or prilocaine.
Methemoglobinemia is a condition caused by elevate levels of methemoglobin in the blood. It is a form of haemoglobin that contains the ferri form of iron. The binding of oxygen to methemoglobin result in an increased affinity for oxygen in the remaining heme sites that are in ferrous state within the same tetrameric haemoglobin unit. This leads to an overall reduced ability of the red blood cell to release oxygen to tissues.
