Agent Name

Phosphoric acid

CAS Number




Major Category

Toxic Gases & Vapors


Acide phosphorique [French]; Acido fosforico [Italian]; Acidum phosphoricum; Evits; Fosforzuuroplossingen [Dutch]; Hydrogen phosphate; Orthophosphoric acid; Phosphoric acid; Phosphoric acid, ortho-; Phosphorsaeure; Phosphorsaeureloesungen [German]; Sonac; Wc-reiniger; White phosphoric acid; o-Phosphoric acid; [ChemIDplus] UN1805


Acids, Inorganic


Thick, colorless, odorless, crystalline solid. [Note: Often used in an aqueous solution.]; [NIOSH]


". . . used in fertilizers, detergents, foods and beverages, water treatment, pickling and rust proofing metals, and for many other purposes." [ACGIH] Used in photography (platinum printing); [] Used as a wet etchant in semiconductor manufacturing at a standard concentration of 85%; [CSH, p. 46]


Liquid or solid form causes second degree burns after contact for a few minutes; [CHRIS] Usually shipped as a solid or 85% solution. [CAMEO] Phosphoric acid > 70% is corrosive to skin. [Quick CPC] Phosphoric acid is an eye, skin, and upper respiratory tract irritant. [ACGIH] "The risk of pulmonary edema is very small." [Desai H. Phosphorus and Phosphorus Compounds. In: Sullivan JB, Krieger GR (eds). Hazardous Materials Toxicology. Baltimore: Williams & Wilkins, 1992; p. 938.] Corrosive to the skin, eye, and respiratory tract; [ICSC] "If phosphoric acid is used as a catalyst, phosphine can be formed in the strongly reducing atmosphere of the hot emissions. In air, phosphine rapidly oxidizes to phosphorus oxide." [IARC 2012: Iron and steel founding]

Exposure Assessment
Skin Designation (ACGIH)

Insufficient data


1 mg/m3


3 mg/m3


1 mg/m3


2 mg/m3, inhalable fraction


1000 mg/m3

Excerpts from Documentation for IDLHs

Basis for original (SCP) IDLH: According to MCA [1958], phosphoric acid does not cause any systemic effect, and the chance of pulmonary edema from mist or spray inhalation is very remote. The rat oral LD50 of 1,530 mg/kg [Biofax 1970] cited by NIOSH provides a calculated IDLH of about 10,000 mg/m3. . . . Basis for revised IDLH: The revised IDLH for phosphoric acid is 1,000 mg/m3 based on acute oral toxicity data in animals [Biofax 1970]. This may be a conservative value due to the lack of relevant acute toxicity data for workers.

Vapor Pressure

0.02 mm Hg

Lethal Concentration

LC50 (rat) > 850 mg/m3/1H

Adverse Effects
Toxic Pneumonitis



Skin Burns

Links to Other NLM Databases
Health Studies

Human Health Effects from Hazardous Substances Data Bank:

Toxicity Information


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Related Information in HazMap

Industrial Processes with risk of exposure:


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