You've developed the 'iron liver' mutation! This mutation confers +1 Endurance.
A reorganized liver filters out blood toxins such as poisons and drugs; unfortunately it also cuts the effectiveness of nanites. On the plus side, it turns excess alcohol into energy the body can use for healing itself and recovering from revival.
Your nanite healing resistance increases by 25 Your THC resistance increases by 40 Your speed resistance increases by 40 Your curare resistance increases by 60 Your alcohol resistance increases by 50 Your spider venom resistance increases by 70 Your PCP resistance increases by 75
Essentially, it allows you to drink alcohol for health and gives resistance to some toxins at the cost of some healing from nanites and some resistance to crank. It's often taken by players with low medic skill to allow on demand healing. Note that Jacks Liquors won't sell alcohol to underaged characters, so you will either need to rely on
bathtub gin the nerfed-to-death tub from the crack mansion or find another source of alcohol. I hear there are a few places that don't card anymore.
The main drawback to this mutation is the reduced effect from Nanite Healers. This is somewhat offset by the ability to "chug" containers of alcohol which will usually get you very drunk very quickly (note that with 50% resistance to alcohol, you will occasionally be completely uneffected by it). Every time your drunk status is increased, the alcohol effectively 'ticks', giving you a heartbeat's worth of healing. Although doing this can be dangerous (for example, if you're wielding a two handed weapon you'll unequip it, which may cause you to stop parrying) and is slower than a nanite healer, it has a bonus in that in addition to quick and powerful healing it gives a longer healing over time effect as the booze works its way through your system. Having alcohol in your system also causes the player to destress every heartbeat.
The Iron Liver mutation is very easy to get. It's just inside the chemical plant. Head south from AP until you hit the end of the road, then head west until you start "Traveling". When you arrive, head west and south through the gate. There are two mutations, one to the left and one south and east from there. These are screech and iron liver. No hostile mobs path in this area, so it's completely safe. Do not walk more than two or three rooms south of the gate though, as the mobs there are sometimes hostile and can be dangerous to new players.