Picric acid: Understanding specific chemicals hazard
Introduction and stories
Picric acid is a yellowish crystalline solid. It is used as a high explosive, an oxidant in rocket fuels, in matches and leather processing, in dyes, as a laboratory reagent for serum creatinine analysis in humans and experimental animals, other laboratory uses, metal etching, batteries, as a textile mordant, in manufacture of colored glass, and in the production of picramic acid and chloropicrin.
During the 1920s-30s, picric acid was used either alone or in combination with butyl aminobenzoate as an antiseptic dressing for burn wounds. About 4% of patients treated with picric acid developed sensitization local dermatitis and at least one case of serious central nervous system dysfunction occurred following topical picric acid application. Picric acid does not sensitize directly, but only after conversion to a more reactive compound.
- With direct contact, picric acid causes a yellowish staining of the hair and skin (pseudo-jaundice) which was common in workers when picric acid was used as an explosive in munitions production.
- Sailors on US Navy ships anchored in a harbor in Japan at the conclusion of WWII developed hematuria, presumed to be due to drinking water made from sea water after a large amount of picric acid-containing munitions were dumped into the harbor.
With systemic absorption and poisoning with picric acid, all the tissues are colored yellow. Because the yellow color gets into the aqueous humor of the eye, the vision appears yellow.
- Picric acid has been said to be readily absorbed through the skin and mucous membranes.
- Picric acid is an effective inhibitor of photosynthetic electron transport in plants. It can serve as a nitrate source for certain bacteria.
- Picric acid as a hematoxylin basic fuschin picric acid method has been used for the identification of early myocardial infarction during autopsies.
Let’s understand the risk it presents.
A little bit of chemistry
Picric acid is a phenolic compound, also known as 2,4,6-trinitrophenol. It is a yellowish, odorless solid material, although most often utilized as an aqueous solution.
CAS 88-89-1; Molecular Formula C6H2(NO2)3OH
Other names for picric acid include:
- Phenol trinitrate
- Carbazotic acid
- Pictronitric acid
- Carbonitric acid
- Nitrophenesic acid
- Nitroxanthic acid
Picric acid has reactivity with or is incompatible with copper, lead, zinc and other metals; salts; plaster; concrete, and ammonia. It is corrosive to metals and an explosive mixture results when aqueous solutions crystallize. Picric acid does not attack tin or aluminum.
US OSHA has classified picric acid as a Class A Explosive. Picic acid explodes at temperatures greater than 572° F. It is a combustible/flammable solid. It may explosively decompose on shock, concussion, or friction.
It has become increasingly common for bomb disposal units to be called out for outdated picric acid found in chemical laboratories where reaction with metal caps on containers can explode when attempted to be opened. Picric acid in containers with plastic caps may also form crystals that can be explosive when attempted to be opened. Soaking such plastic-capped containers in water may mitigate this risk. The Division of Chemical Health and Safety (C-CHAS) of the American Chemical Society list serve quite frequently has reported such occurrences over the past few years.
Eye/skin irritant/corrosive – skin absorption potential
Picric acid is an irritant of the eyes, skin, and mucous membranes. It can be absorbed through the skin. Picric acid is a skin sensitizer, resulting in allergic contact dermatitis.
Dermatitis caused by direct skin exposure to picric acid most often occurs on the face, particularly around the mouth and nose. It begins with erythema and then progresses through papules and vesicles to desquamation.
Toxicity may occur following systemic absorption by any exposure route and consists of lassitude, a bitter taste in the mouth, myalgias, anuria, polyuria, gastrointestinal disturbances, and hepatic and kidney injuries. This is what happened to US Navy sailors during WWII.
Exposure to dust or fumes can cause eye irritation, which may be worse because of sensitization. A direct splash of picric acid solution into the eye can cause corneal injury.
In one person occupationally exposed by inhalation, signs and symptoms included temporary coma, weakness, myalgias, and kidney injury manifested as anuria and then polyuria.
Ingestion of 2-5 grams of picric acid results in a bitter taste in the mouth, vertigo, headache, nausea, vomiting, and diarrhea, a yellowish skin discoloration, erythrocyte lysis, and hepatic and kidney injuries including hemorrhagic nephritis.
The European Chemical Agency (ECHA) recommends to label it with the H201, H301, and H311 risk phrases (full classification).
What to do in case of an exposure to picric acid
The above data suggest that an amphoteric washing solution such as Diphoterine® solution would most likely be of use with acute exposures to prevent or mitigate eye/skin injuries. In case of exposure to picric acid, emergency washing with Diphoterine® solution is recommended in order to limit the induced injuries.
Picric acid was positive in the Ames salmonella assay for mutagenicity when metabolic activation was present. It has also been reported to be non-mutagenic in the Ames test. Those contradictory results did not allow to draw a conclusion on picric acid mutagenicity.
Picric acid has produced contradictory effects in various assays for genotoxicity, being positive in some and negative in others.
A review by a committee of the Health Council of the Netherlands in 2002, did not find published data on long-term toxicity, carcinogenicity, or reproductive toxicity.
- US OSHA: Permissible Exposure Limit (PEL) 0.1 mg/m3 (Skin designation)
- US NIOSH: Recommended Exposure Limit (REL) 0.1 mg/m3
– Short-Term Exposure Limit (STEL) 0.3 mg/m3 (Skin designation)
– Immediately Dangerous to Life or Health (IDLH) 75 mg/m3
- US ACGIH: TLV/TWA 0.1 mg/m3
- The Netherlands: MAC (administrative occupational exposure limit) 0.1 mg/m3 8-hour TWA (Skin notation)
|H201||Explosive; Mass Explosive Hazard|
|H301||Toxic if swallowed|
|H311||Toxic in contact with skin; Toxic if inhaled|
- Al-Rufaie HK, Florio RA, Olsen EG. Comparison of the haematoxylin basic fuschin picric acid method and the fluorescence of haematoxylin and eosin stained sections for the identification of early myocardial infarction. J Clin Pathol 1983; 36(6):646-649.
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- INRS: No Data Found. INRS Toxicological Sheets, accessed August 11, 2014.
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- NIOSH: Picric acid, in: NIOSH Pocket Guide to Chemical Hazards, Department of Health and Human Services, Centers for Disease Control and Prevention, National Institute for Occupational Health and Safety, DHHS (NIOSH) Publication No. 2005-149, Cincinnati, OH, USA, 2007, p. 259.
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Alan H. Hall, M.D. President and Chief Medical Toxicologist
Toxicology Consulting and Medical Translating Services, Inc.
Laramie, Wyoming, USA
Clinical Assistant Professor
Colorado School of Public Health
University of Colorado-Denver
Denver, Colorado, USA