Why ordinary saline PH is acidic(5.5)?

Why ordinary saline PH is acidic(5.5)?
Because it's above neutral even!!
That's a really interesting question.
Pure saline solutions consist singular of Na+ and Cl- ions in solution. As such, the pH of the saline SHOULD be nonpartisan.
But it isn't. Saline solutions are typically marked as have a pH of anything between 4 and 7. Why?
I had to do some research on this, but it turns out that in that are two possible causes:
1) It seem that atmospheric carbon dioxide (CO2) is principally to blame. It dissolves in the saline, forming carbonic acerbic:
CO2 + H20 --> HCO3- (equation left unbalanced)
2) Some authors also purpose that the PVC packaging may increase the bitterness of the solutions.
Interesting!