Editing Nitrate (section)

=== Methemoglobinemia ===
{{Main Article|Blue baby syndrome|Methemoglobinemia}}
One of the most common cause of [[methemoglobinemia]] in infants is due to the ingestion of nitrates and nitrites through [[well water]] or foods. 

In fact, nitrates ({{Chem2|NO3-}}), often present at too high [[concentration]] in drinkwater, are only the precursor chemical species of [[nitrite]]s ({{Chem2|NO2-}}), the real culprits of methemoglobinemia. Nitrites produced by the [[Denitrification|microbial reduction of nitrate]] (directly in the drinkwater, or after ingestion by the infant, in his digestive system) are more powerful [[Oxidizing agent|oxidizers]] than nitrates and are the chemical agent really responsible for the [[Redox|oxidation]] of Fe<sup>2+</sup> into Fe<sup>3+</sup> in the [[tetrapyrrole]] [[heme]] of [[hemoglobin]]. Indeed, nitrate anions are too weak oxidizers in [[aqueous solution]] to be able to directly, or at least sufficiently rapidly, oxidize Fe<sup>2+</sup> into Fe<sup>3+</sup>, because of [[Chemical kinetics|kinetics]] limitations.

Infants younger than 4 months are at greater risk given that they drink more water per body weight, they have a lower [[Nicotinamide adenine dinucleotide|NADH]]-[[cytochrome b5 reductase]] activity, and they have a higher level of fetal hemoglobin which converts more easily to [[methemoglobin]]. Additionally, infants are at an increased risk after an episode of [[gastroenteritis]] due to the production of [[nitrite]]s by [[bacteria]].<ref>{{Cite book | vauthors = Smith-Whitley K, Kwiatkowski JL | chapter = Chapter 489: Hemoglobinopathies | veditors = Kliegman RM |title=Nelson Textbook of Pediatrics | edition = 21st | date = 2000 |publisher=Elsevier Inc.|pages=2540–2558 | isbn = 978-0-323-52950-1 }}</ref> 

However, other causes than nitrates can also affect infants and pregnant women.<ref>{{Cite journal | doi=10.1111/j.1475-2743.2004.tb00344.x|title = Nitrate and human health| journal=Soil Use and Management| volume=20| issue=2| pages=98–104|year = 2006| vauthors = Addiscott TM, Benjamin N | s2cid=96297102 }}</ref><ref name="pmid10379005">{{cite journal | vauthors = Avery AA | title = Infantile methemoglobinemia: reexamining the role of drinking water nitrates | journal = Environmental Health Perspectives | volume = 107 | issue = 7 | pages = 583–6 | date = July 1999 | pmid = 10379005 | pmc = 1566680 | doi = 10.1289/ehp.99107583 | bibcode = 1999EnvHP.107..583A }}</ref> Indeed, the [[blue baby syndrome]] can also be caused by a number of other factors such as the [[cyanotic heart disease]], a [[congenital heart defect]] resulting in low levels of oxygen in the blood,<ref name="MedlinePlusEncyclopedia Cyanotic heart disease">{{MedlinePlusEncyclopedia|001104|Cyanotic heart disease}}</ref> or by gastric upset, such as diarrheal infection, protein intolerance, heavy metal toxicity, etc.<ref>{{cite journal | vauthors = Manassaram DM, Backer LC, Messing R, Fleming LE, Luke B, Monteilh CP | title = Nitrates in drinking water and methemoglobin levels in pregnancy: a longitudinal study | language = En | journal = Environmental Health | volume = 9 | issue = 1 | pages = 60 | date = October 2010 | pmid = 20946657 | pmc = 2967503 | doi = 10.1186/1476-069x-9-60 | doi-access = free | bibcode = 2010EnvHe...9...60M }}</ref>