. . . "PPB" . "1e-09"^^ . "Parts per billion"@en . "61" . . . . . "0112/2///62720#UAD926" . . . . "Dimensionless unit for concentration. Recommended practice is to use specific units such as \\(ug/l\\)."^^ . "http://aurora.regenstrief.org/~ucum/ucum.html#section-Derived-Unit-Atoms"^^ . . "[ppb]"^^ . .