Total phosphorus: Reporting for total phosphorus and what you need and don’t need to consider for the National Pollutant Release Inventory

Phosphorus is contained in many industrial chemicals and products such as corrosion inhibitors in hydraulic fluids, antidegradant agents in lubricating oils, flame retardants in plastics and rubber products, reducing agents in electroless nickel plating, etc.  This guidance contains examples of some items that you may (or may not) need to consider in your threshold calculations, depending on the application. For more information, contact the NPRI HelpDesk.

Please note that the threshold calculation for phosphorus must exclude the quantity of phosphorus that is manufactured, processed or otherwise used in activities exempt from reporting for Parts 1-3 substances (See the Guide for Reporting to the National Pollutant Release Inventory). Furthermore, to correctly perform threshold calculations for activities involving phosphorus containing chemicals and products, you need to understand the term "article".

An article is defined as a manufactured item that does not result in a release or disposal of an NPRI substance when it undergoes processing or other use. When articles are processed or otherwise used, and there are no releases or disposals, or the releases are recycled with due care, the NPRI substances in that article do not need to be included in the threshold calculation.

Reporting for total phosphorus

Phosphorous is listed twice in the NPRI as phosphorous (total, excluding yellow or white phosphorous) and phosphorous (yellow or white only) with the CAS RN 7723-14-0. The listing for phosphorous (yellow or white only) should be reported as the total of the yellow and white allotropes of elemental phosphorous. Total phosphorous does not have a CAS RN, since this substance must be reported as the total of the equivalent weight of phosphorous in phosphorous-containing compounds, but not including phosphorous (yellow or white). For example, if a facility were to manufacture 100 tonnes of cupric phosphate (Cu3(PO4)2) and 100 tonnes of sodium tripolyphosphate (Na5P3O10), with respective molecular weights of 380.58 g/mol and 367.86 g/mol, only the respective mass contribution of phosphorus of (2 × 31 g/mol) and (3 × 31 g/mol) in the two substances should be included in the threshold calculation.  The amount of total phosphorous that is manufactured is 16.3 tonnes (100 x 62/380.58) + 25.3 tonnes (100 x 93/367.86) = 41.6 tonnes. Since 41.6 tonnes is above the 10 tonne mass reporting threshold for quantities that are manufactured, processed or otherwise used (MPO), reporting is required.

Please note for the NPRI reporting requirements, the total phosphorus should be reported as "P" and if total phosphorus is measured as orthophosphate (PO₄³⁻), it should be converted to "P" by dividing by 3.06.

Examples of what you need and don't need to consider for the threshold calculations


Sealants and adhesives

Greases, lubricant oils and hydraulic fluids

Plastics and rubber products manufacturing

Paints and coatings



While phosphorus is essential to life, high concentrations can cause direct toxic effects.

Releases of any form of phosphorus must be reported because of the harmful effects of biologically available phosphorus in water. Phosphorus readily changes forms; releases to air can settle on land or water, and releases to land can leach into water.

Phosphorus can increase the growth of natural flora and fauna in rivers and coastal waters. It can alter biological diversity, reduce recreational potential and degrade source water for human consumption and industrial uses.

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