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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:

  1.  2,4,6-trinitrophenol
  2. Phenol trinitrate
  3. Carbazotic acid
  4. Pictronitric acid
  5. Carbonitric acid
  6. 2-Hydroxy-1,3,5-trinitrobenzene
  7. Lyddite
  8. Melanite
  9. Nitrophenesic acid
  10.  Nitroxanthic acid
  11. Shimose
  12. Trinitrophenol
  13. TNP

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.

Chronic effects/carcinogenicity

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.

Regulatory/advisories issues

  • 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)
Risk phrase Signification
H201 Explosive; Mass Explosive Hazard
H301 Toxic if swallowed
H311 Toxic in contact with skin; Toxic if inhaled

References consulted

  • 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.
  • Behrend C, Heesche-Wagner K. Formation of hydride-Meisenheimer complexes of picric acid (2,4,6-trinitrophenol) and 2,4-dinitrophenol during mineralization of picric acid by Nocardioides strain CB 22-2. Appl Environ Microbiol 1999; 65(4):1372-1377.
  • Cameron M. Picric acid hazards. oag.ca.gov/sites/all/files/agweb/pdfs/cd/safety/picric.pdf, accessed August 12, 2014.
  • Cocker J, Mason HJ, Warren ND, Cotton RJ. Creatinine adjustment of biological results. Occup Med (Lond) 2011; 61(5):349-353.
  • ECHA: Picricacid, accessed August 11, 2014.
  • Harris AH, Binkley OF, Chenowith BM. Hematuria due to picric acid at a naval anchorage in Japan. Am J Public Health Nations Health 1946; 36:727-733.
  • Hathaway GH, Proctor NH (eds). Picric acid, in: Proctor and Hughes’ Chemical Hazards of the Workplace, 5th ed. Wiley Interscience, Hoboken, NJ, 2004, pp. 588-598.
  • Health Council of The Netherlands. Picric acid; Health-based Reassessment of Occupational Exposure Limits. Committee on Updating Occupational Exposure Limits; a committee of the Health Council of The Netherlands. No. 2000/052, The Hague, 31 October 2002.
  • HSDB. Picric acid, in: Hazardous Substances Data Bank, National Library of Medicine, Bethesda, MD, USA. NLM-NIH (Toxnet), accessed August 11, 2014.
  • INRS: No Data Found. INRS Toxicological Sheets, accessed August 11, 2014.
  • Landsteiner K, Di Somma AA. Studies on the sensitization of animals with simple chemical compounds: VII. Sensitization to picric acid; subsidiary agents and mode of sensitization. J Exp Med 1940; 72(4):361-366.
  • Lenke H, Knackmuss HJ. Initial hydrogenation during catabolism of picric acid by Rhodococcus erythropolis HL 24-2. Appl Environ Microbiol 1992; 58(9):2933-2937.
  • Maguire HC, Chase MW. Studies on the sensitization of animals with simple chemical compounds. 13. Sensitization of guinea pigs with picric acid. J Exp Med 1972; 135(2):357-375.
  • 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.
  • Oettmeier W, Masson K. Picrate as an inhibitor of photosystem II in photosynthetic electron transport. Eur J Biochem 1982; 122(1):162-167.
  • Yuen PS, Dunn SR, Miyaji T, Yasuda H, Sharma K, Star RA. A simplified method for HPLC determination of creatinine in mouse serum. Am J Physiol Renal Physiol 2004; 286(6):F1116-1119.

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