B737-800
Flight Crew Air Transport Pilot (ATP); Flight Crew Multiengine; Flight Crew Instrument
Other / Unknown; Time Pressure
Deviation / Discrepancy - Procedural Hazardous Material Violation; Deviation / Discrepancy - Procedural Published Material / Policy
General Maintenance Action; General Flight Cancelled / Delayed; General Work Refused
Chart Or Publication; Human Factors; Procedure
About 10 minutes prior to scheduled passenger flight pushback at ZZZ; received a HAZMAT NOTOC (hazardous material notice to Captain).  There were 6 lines of HAZMAT of which 5 were normal but one stood out with lithium metal batteries; ERG (emergency response guidebook) code 12FG.  I queried the messenger about them; he said he could take a picture of the box to show me.  While he went to do that I discussed the situation with the FO (First Officer).  The battery weight was.15 kg or just a bit over 5 ounces and contained in equipment.  That size battery is similar in weight to our iPad batteries.  12FG code is risk of fire/heat/smoke with the additional risk Z 'aircraft cargo fire suppression system may not extinguish or contain the fire.  Consider landing immediately'.  When carried in our cargo hold; with passengers on board; that sort of risk gets my attention.  When the messenger returned with the picture I queried him about carrying that cargo in the cockpit or passenger compartment where we at least have our BCB battery containment bag; in case something went wrong.  He said they didn't know which box batteries were in so that wasn't possible.  It was almost push time so I called and discussed the situation with Dispatch.  They agreed with my concern and said they weren't experts on HAZMAT but could research who was or we could just remove the batteries in the interest of expediency.  We then opted for removing the lithium batteries for simplicity and timeliness.  After this was accomplished; we got a revised load closeout and were on our way about 20-30 minutes late.  The rest of our flight was uneventful.  Having reviewed FOM guidance on this issue previously; I consider it somewhat vague.  While the likelihood for these batteries to start burning is slim; the impact would be catastrophic and the ERG  code even warns us of this.  This could easily be mitigated by having an item like this in the passenger cabin or cockpit where FAs (flight attendants) or pilots could at least deal with the threat with the BCBs which are provided for an unlikely event such as this.  FOM  deal[s] with this and state or imply that these types of things should not be in the cargo compartment.  FOM addresses HAZMAT codes but really gives no guidance other than inspecting NOTOC paperwork for date; tail number etc.I've been involved in carrying lots of hazardous materials in aircraft over my career and believe I'm well versed on the risk vs reward of it.  While technically the NOTOC I received was legal per our FOM; the risk of these batteries also noted on the NOTOC; didn't appear to make sense from a risk management or an SMS (safety management systems) standpoint.  Thus my questions about better potential options.  If we are intentionally doing something like this; I; Dispatch; other pilots etc would probably be better served with more of a heads up on the decision process and other options sooner in the departure process.  Were we just doing the minimum legal or is there a more appropriate way in hindsight?  It certainly seemed like pushback time induced pressure discouraged discussion/questions about this sort of thing.
B737-800 Captain reported refusing Hazmat cargo due to vague FOM guidance as well as lack of definitive Dispatch information regarding the risk of transporting Hazmat cargo.