Parts Per Billion
A means of expressing minute concentrations, often of an element, compound, or particle that contaminates soil, water, air, or blood. The expression may be on either a mass or a volu...
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Parts Per Million
A means of expressing small concentrations, usually of an element, compound, contaminant, or particle in water or a mixed medium such as soil and normally on a mass basis. Units that...
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Parts Per Trillion
A means of expressing extremely minute concentrations of substances in water or air. In the United States, the concentration is the number of units of the substance found in 1x1012 ...
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Parts Per Billion