Phosphoric acid, aka orthophosphoric acid, is a colourless and odourless inorganic acid. Its molecular formula is H3PO4, and in its pure form it is a crystalline solid. [1,2,3]
Phosphoric acid has a range of uses across various applications. It is used as an ingredient in fertilisers and detergents. The acid is also used as a food and drink additive for a sharp, tangy taste. It is used in dental cements, as an acid catalyst in making ethylene, and as an analytical agent.
Routes of Exposure 
The main routes of exposure to phosphoric acid are skin and eye contact.
Phosphoric acid poisoning affects a range of systems, including the integumentary and respiratory systems.
Acute Effects 
Severity of symptoms depend on the level and type of exposure.
If inhaled, this acid can irritate the nose and throat. If phosphoric acid comes into contact with a person’s skin or eyes, it can cause pain, severe burns, blurred vision, blistering and redness. Ingestion of the acid may cause burning of the throat, stomach, lips and tongue, and symptoms may be diarrhoea, nausea, cramps and vomiting. Permanent damage can result from acute phosphoric acid exposure.
Chronic Effects [4,5]
Chronic exposure to phosphoric acid is toxic to multiple body systems. Long term exposure to the acid can result in red, dry, cracked skin (dermatitis) and/or conjunctivitis. It can also cause erosion of the teeth and ulcerative changes in the mouth.
First Aid Measures 
Ingestion: DO NOT induce vomiting. Move patient into recovery position. If the person is conscious (and not showing any signs of drowsiness), then you can give them water to rinse their mouth. Contact a medical professional immediately.
- Skin contact: Avoid direct contact with contaminated clothing. Wearing protective clothing if necessary, remove all contaminated clothing, footwear and accessories. Do not re-wear clothing until it has been thoroughly decontaminated; rinse with flowing water for at least 30 minutes. Contact a doctor immediately.
- Eye contact: Flush eyes (including under the eyelids), with fresh running water for at least 30 minutes. Removal of contact lenses should only be done by skilled personnel. Do not stop flushing due to the lens. Contact a medical professional immediately.
- Inhalation: Move the patient to a fresh air source. If symptoms persist, contact a medical professional.
- General: Never administer anything by mouth to an unconscious, exposed person.
Exposure Controls/Personal Protection 
Engineering controls: Emergency eyewash fountains and quick-drench areas should be accessible in the immediate area of the potential exposure. Ensure there is adequate ventilation, or use a local exhaust ventilation.
- Personal protection: Safety glasses with side shields or chemical goggles, protective and dustproof clothing, gloves, a P.V.C apron and an appropriate mask or dusk respirator. Do not wear contact lenses as they could absorb chemicals in the air. Wear impervious shoes. Other protection could overalls. For specifications regarding other PPE, follow the guidelines set in your jurisdiction.
The American Conference of Governmental Industrial Hygienists (ACGIH) has set a Time Weighted Average (TWA) concentration limit for phosphoric acid of 1mg/m3.
Australia Exposure Standards have set a TWA for phosphoric acid of 1mg/m3.