9.20.2016

The real reason nitrite is more toxic and dangerous than nitrate

So we may have heard that nitrites oxidize hemoglobin in the blood producing methemoglobin.  This eliminates heme's oxygen carrying capacity and makes you turn blue.  Not only this but nitrite toxicity can be deadly.  What makes it so dangerous?  

If its mechanism of toxicity is directly oxidizing the blood wouldn't nitrates be worse since they have more oxygens (No3 vs No2) and are better oxidizers than nitrites?  Well the answer to this is that it isn't the nitrite that is dangerous, but in what the nitrite becomes after it oxidizes something.  No2 (nitrite) has roughly the same oxidation power as No3 (nitrate).  However nitrate turns into N2O4 or HNO2.  HNO2 is nitrite so some nitrate gets converted to nitrite but not much.  Most turns into N2O4 which has about the same oxidation power (oxidation potential) as nitrate or nitrite so no harm done there. If N2O4 reacts then it turns into nitrite.  Also some nitrite or nitrate gets turned into NO the vasodilator which is doubly as oxidative as nitrite or nitrate. And finally NO gets converted to N2O which is laughing gas.  N2O is only about as oxidative as hydrogen peroxide so not too bad.  That is where that path ends and the N2O gets turned into N2 which is just harmless nitrogen gas.  

HOWEVER Nitrite gets converted to H2N2O2 which is one of the most potent oxidizers known!  Almost double the oxidation power of NO, H2N2O2 (hyponitrous acid) is on par with fluorine gas!  So this conversion of nitrite to hyponitrous acid is the real reason why nitrite is so much more dangerous than nitrate or nitric acid.  And it is the hyponitrous acid, not the nitrite, that is dangerous.

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