Home > Parts per million

1 Illustrations of one part per million

The metric system is the most convenient way to express this since metric units go by steps of ten, hundred and thousand. For example, a milligram is a thousandth of a gram and a gram is a thousandth of a kilogram. Thus, a milligram is a thousandth of a thousandth, or a millionth of a kilogram. A milligram is one part per million of a kilogram thus, one part per million (ppm) is the same as one milligram per kilogram. Just as part per million is abbreviated as ppm, a milligram per kilogram has its own symbolic form -- mg/kg. Using our abbreviations, one ppm equals one mg/kg.

• one milligram in a kg is 1 ppm (by mass).
• one gram in a metric tonne.
• 1 liter (L) of pure water at 4°C and one standard atmosphere pressure weighs exactly 1 kg, so 1 mg/L is 1 ppm.
• one millilitre in a cubic metre (or kilolitre).
• In a percentage, 0.1% are 1000 ppm or 1% are 10,000 ppm.

2 Use

Examples of situations where parts per million are an appropriate measure include:

• relative abundances of rare element s in the earth's crust
• concentrations of pollutanttoxicology environment Pollutants are substances which directly or indirectly damage us or the environment. Many of the compounds which are dangerous to the environment can also be harmful to us in the long-term and come from nuclear- fossil sources, likes in the environmentAn environment is a complex of external factors that acts on a system and determines its course and form of existence. An environment may be thought of as a superset, of which the given system is a subset. An environment may have one or more parameters, p

3 Other parts per units

Similar, even smaller measures are:

• Parts per billionThe word billion , and its equivalents in other languages, refer to one of two different numbers. The obsolete word "milliard" can be used for 109 to avoid ambiguity, though this usage is unfamilar to some speakers of English. See long scale for a more de (ppb).
• Parts per trillionThe numeral trillion refers to one of two number values, depending on the context of where and how it is being used. It is the largest numerical value in everyday non-scientific use in the English language. Usage Short scale usage In Brazil, Russia, Turke (ppt).