True it certainly is mysterious how they came to that figure but the LOAEL and NOAEL were for the effect of delaying development of the nervous system of rats, unborn pups not adult rats which is why I think use with babies or pregnant women is questionable, The reason for this effect seems to be unknown but may be, at a guess, due to oxidation of something in the blood responsible for this development.
I wouldn't call this oxidative stress though
• An MRL of 0.1 mg/kg/day has been derived for intermediate-duration oral exposure (15–364 days) to chlorite.
This MRL is based on a no-observed-adverse-effect-level (NOAEL) of 2.9 mg chlorite/kg/day and a LOAEL of 5.7 mg chlorite/kg/day for neurodevelopmental effects (lowered auditory startle amplitude) in rat pups that had been exposed throughout gestation and lactation via their mothers (Gill et al. 2000).