Parts per million

The term parts per million (abbreviated ppm) describes a ratio of density used for measuring small concentrations of a substance within a mass/volume of a much larger one. Most often used to measure minute concentrations of substances in liquid or gaseous volumes.

1 ppm = 0.0001% = 1:1000000

To revive the crew in 2367, Data used five parts per million of ADTH. 

Beta Agni II's water supply was contaminated with forty parts per million of tricyanate later that year. 

To counter a graviton field, Jadzia Dax used one part per million of tridium in 2369. 

A class 17 nebula in the Delta Quadrant was composed of 7,000 parts per million of sirillium in 2373. 

Seventeen parts per million of argonite was well under safety margins for the air supply on Deep Space 9. 

External link
Teile pro Million Parts per million