Lactate is a chemical in C2 and C3/DS. It is created from pyruvate, a byproduct of glucose digestion, when there is not enough oxygen in the norn's bloodstream. In C2, when a norn stops drowning, the lactate is then converted back into pyruvate. In C3, however, despite being labelled 'Neutral' in the C3 chemical list, it has no way of being removed from the body, and it damages the Muscle Tissue.
evolnemesis has theorised that because lactate is chemical number 1, a gene producing it is one of the most common possible kinds of mutations in C3/DS. (Requiring two mutations to be produced as an additional product- one to change the value of the 'something produced' in a reaction from 0 to 1 for lactate, and another to change the amount of nothing or lactate to be produced.)
- Lactate Cure? - more information on how to gengineer a lactate oxidation gene.