ppmort
ppmort, short for "parts per million per year," is a unit used to express the rate of change of a concentration of a substance over time. It is commonly encountered in fields such as environmental science, atmospheric chemistry, and industrial hygiene. The "ppm" part refers to parts per million, a dimensionless quantity representing a ratio of a substance's concentration to the total concentration of the mixture. Multiplying this by "per year" indicates how much that concentration increases or decreases annually.
For example, if a pollutant in the air is increasing at a rate of 0.5 ppmort, it