--answer as to the (UPG?)

Hi mu-shen,

The Epsom salt may be identified in the USA standards as (UPG?) which is(USP) grade and other grades like Tech grade and some other grades !

The (UPS) grade is what may used for human use, and may be used internal as well as external and it is considered Cleaner of foriegn waste like Rat tirds etc which you may not want to eat !

Whereas the Tech Grade may be used in making Fertilizers etc and thus the need to keep Rats out of it may not be important !

Smile Tis your choice.