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Maximum contaminant levels (MCLs) are standards that are set by the United States Environmental Protection Agency (EPA) for drinking water quality. [1] [2] An MCL is the legal threshold limit on the amount of a substance that is allowed in public water systems under the Safe Drinking Water Act (SDWA).
In the metric system, a microgram or microgramme is a unit of mass equal to one millionth (1 × 10 −6) of a gram. The unit symbol is μg according to the International System of Units (SI); the recommended symbol in the United States and United Kingdom when communicating medical information is mcg .
The MIC is often expressed in micrograms per milliliter (μg/mL) or milligrams per liter (mg/L). In diagnostic labs, MIC test results are used to grade the susceptibility of microbes. These grades are assigned based on agreed upon values called breakpoints.
The magnesium and calcium concentrations in the filtered water were 2.50 and 4.50 milligrams per liter (0.00250 and 0.00449 oz/cu ft). The strontium and barium were only 30 and 40 micrograms per liter (3.0 × 10 −5 and 4.0 × 10 −5 oz/cu ft) and the beryllium concentration was less than 10 micrograms per liter (1.00 × 10 −5 oz/cu ft). [5]
Therefore, it is common to equate 1 kilogram of water with 1 L of water. Consequently, 1 ppm corresponds to 1 mg/L and 1 ppb corresponds to 1 μg/L. Similarly, parts-per notation is used also in physics and engineering to express the value of various proportional phenomena.
mg: milligram: 10 3 g kg: kilogram: 10 −6 g μg: microgram (mcg) 10 6 g Mg megagram 10 −9 g ng: nanogram: 10 9 g Gg gigagram 10 −12 g pg picogram 10 12 g Tg teragram 10 −15 g fg femtogram 10 15 g Pg petagram 10 −18 g ag attogram 10 18 g Eg exagram 10 −21 g zg zeptogram 10 21 g Zg zettagram 10 −24 g yg yoctogram 10 24 g Yg yottagram
" indicates that no standard has been identified by editors of this article and ns indicates that no standard exists. μg/L = micrograms per litre, or 0.001 ppm; mg/L = 1 ppm, or 1000 μg/L. * means action level; not a concentration standard. A public water system exceeding the action level must implement "treatment techniques" which are ...
mg/m 3 = milligrams of pollutant per cubic meter of air at sea level atmospheric pressure and T: ppmv = air pollutant concentration, in parts per million by volume T = ambient temperature in K = 273. + °C 0.082057338 = Universal gas constant in L atm mol −1 K −1: M = molecular mass (or molecular weight) of the air pollutant