Question: What's the PM for the standard with 12.3 g/kWh CO?
Schema: create table table_2780146_6 (pm__g_kwh_ varchar, co__g_kwh_ varchar, PRIMARY KEY (pm__g_kwh_))
SQL: select pm__g_kwh_ from table_2780146_6 where co__g_kwh_ = "12.3"