Parts per million

Parts per million (ppm)

Parts per million (ppm) is a unit of measurement used in many areas of science and engineering to express the level of impurities in a substance. It is equivalent to milligrams per kilogram (mg/kg) or milliliters per liter (ml/l).

Pronunciation: /pɑːrts pər ˈmɪljən/

Etymology: The term "parts per million" originated in the early 20th century as a way to measure the concentration of substances in air, water, and soil. It is derived from the mathematical concept of ratios.

Usage

In chemistry, ppm is used to measure the concentration of a substance in a solution or in a mixture. For example, a concentration of 1 ppm means that there is one part of the substance for every million parts of the solution or mixture.

In environmental science, ppm is often used to measure the concentration of pollutants in the air, water, or soil. For example, the concentration of carbon dioxide in the atmosphere is often reported in parts per million.

In medicine, ppm is used to measure the concentration of drugs in the body, or the concentration of contaminants in food or water.

Related Terms

• Parts per billion (ppb)
• Parts per trillion (ppt)
• Concentration
• Dilution
• Molarity
• Molality

See Also

• Measurement
• Unit of measurement
• Scientific notation
• Metric system

External links

• Medical encyclopedia article on Parts per million
• Wikipedia's article - Parts per million

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