This old MSDS revised in 2005 refers to the problem I described where they say "California identifies substances with acute LD50's less than 5000 mg/kg as "hazardous wastes". Sodium Tetraborate Pentahydrate is therefore a "hazardous waste" if spilled in California, and should be handled in accordance with applicable state regulations." For that reason, some companies decided not to ship boron products to California. However, that regulation changed and
newer MSDS (though still 2011 so not that new) don't refer to any California limitation anymore. Nevertheless, some places like
poolgeek.com say that "This product will not ship to the state of California."
I think the other thing that may have happened is that California may have required that manufacturers selling boron products had to classify it as an algaecide or at least register it as a pesticide. If you look at the
California Department of Pesticide Regulation Product/Label Database and look for the product PoolProof, you will find a registration for the Nisus PoolProof product. However, if I search by chemical names such as sodium tetraborate pentahydrate found in most borate pool products, I find the following registered (I left out ant killer products):
ACTIVE (03/03/10)BIOGUARD MAINTAIN POWER CHLOR ( 5185- 502-AA )
ACTIVE (06/05/12)MASTER LABEL - SUPER PUCK ( 5185- 460-ML )
ACTIVE (08/31/06)MASTER LABEL - SYNERGY TABS ( 5185- 435-ML )
ACTIVE (05/28/97)SYNERGY TABS ( 5185- 435-AA- 10305)
So it looks like BioGuard decided to register only some of their borate products, specifically Trichlor tabs that contain some boron in them. They did not register their Optimizer Plus and it looks like ProTeam didn't register their Supreme Plus product. Interestingly for boric acid there are pool and spa products:
ACTIVE (06/07/05)RENDEZVOUS PH MAGIC ( 7364-50023-AA )
ACTIVE (02/07/12)RENDEZVOUS SPA SPECIALTIES PH MAGIC ( 7364-50030-AA )
So you should show your pool store guy
Rendezvous Spa Specialties pH Magic which is 97.98% boric acid and
GLB Rendezvous pH Magic though both are described for use in spas. Have him explain how it could be illegal in California yet these products are sold and in fact registered in California for use in spas and also for pools according to the registration:
A 99008 ADJUVANT: WATER MODIFIER 0 A0 REGULAR
A 65011
SWIMMING POOL WATER SYSTE 0 A0 REGULAR