Although rarely used in science (ppm is typically used instead), one permyriad has an unambiguous value of one part per 10,000 (10 4) parts, and a value of 10 −4.
Consequently, 1 ppm corresponds to 1 mg/L and 1 ppb corresponds to 1 μg/L. Therefore, it is common to equate 1 kilogram of water with 1 L of water. When working with aqueous solutions, it is common to assume that the density of water is 1.00 g/mL. The quantity "1 ppm" can be used for a mass fraction if a water-borne pollutant is present at one-millionth of a gram per gram of sample solution. Parts-per notation is often used describing dilute solutions in chemistry, for instance, the relative abundance of dissolved minerals or pollutants in water.