Exposure, hydrofluoric acid

This case illustrates the problem of low level chronic hydrofluoric acid exposure and the insidious nature of osteosclerosis (chronic skeletal fluorosis). Source Wilkie J (1940). Two cases of fluorine osteosclerosis. British Journal of Radiology 13, 213-217.)... 

D. Dermal hydrofluoric acid exposure. For any exposure involving the hand or fingers, obtain immediate consultation from an experienced hand surgeon or medical toxicologist. Regardless of the specific therapy chosen, systemic narcotic analgesics should be strongly considered as adjunctive therapy. 

Successful treatment of severe exposures is dependent on rapid reactions by those responding to the incident and by the affected person(s). In the following sections, reference is made to various medications specific to the treatment of hydrofluoric acid exposure. It is unlikely that the typical rescue squad called to the scene will have these medications so they should be part of the first aid supplies maintained in the immediate area where exposures may occur. Have someone call for emergency medical assistance as soon as possible and direct them to arrange treatment with a physician or trauma center familiar with chemical bums. In all types of exposure, the first action recommended is prolonged flushing with copious amounts of water so an eyewash station, a shower and a source of potable water should be immediately available. 

Honeywell. Recommended Medical Treatment for Hydrofluoric Acid Exposure, Honeywell, Morristown, NJ, May 2000 available at http //membership.acs.Org/F/FLUO/Links.htm (accessed August 15, 2009). 

Sheridan RL, Ryan CM, Quinby Jr WC, Blair J, Tompkins RG, Burke JF. Emergency management of major hydrofluoric acid exposures. Bums. 1995 21(l) 62-4. 

Strausburg M, Travers J, Mousdicas N. Hydrofluoric acid exposure a case report and review on the chni-cal presentation and management. Dermatitis. 2012 23(5) 231-6. 

Toxicity. Sulfur tetrafluoride has an inhalation toxicity comparable to phosgene. The current OSHA standard maximum allowable concentration for human exposure in air is 0.4 mg/m (TWA) (54). On exposure to moisture, eg, on the surface of skin, sulfur tetrafluoride Hberates hydrofluoric acid and care must be taken to avoid bums. One case of accidental exposure of electrical workers to decomposed SF gas containing SF has been cited (108). 

Handling and Toxicity. Tungsten hexafluoride is irritating and corrosive to the upper and lower airways, eyes, and skin. It is extremely corrosive to the skin, producing bums typical of hydrofluoric acid. The OSHA permissible exposure limits is set as a time-weighted average of 2.5 mg/kg or 0.2 ppm (22). 

Potassium Heptafluorotantalate. Potassium heptafluoiotantalate [16924-00-8], K TaF, ciystallizes in colodess, rhombic needles. It hydroly2es in Foiling water containing no excess of hydrofluoric acid. The solubility of potassium heptafluorotantalate in hydrofluoric acid decreases from 60 g/100 mL at 100°C to 0.5 g/100 mL at room temperature. The different solubility characteristics of K TaF and K NbOF are the fundamental basis of the Matignac process (16). A phase diagram exists for the system K TaF —NaCl—NaF—KCl (68). Potassium heptafluorotantalate has an LD q value of 2500 mg/kg. The recommended TWA maximum work lace exposure for K TaF in air is 2.5 mg /m (fluoride base) (69). 

Hydrofluoric acid is highly corrosive to skin and mucous membranes. Even in fairly low concentrations, it causes painful skin burns and severe damage to eyes and the respiratory system. Exposure at higher levels results in destruction of tissues and death. No one in l e.xas City was exposed to more than trace concentrations of hydrofluoric acid. The acid vessel had a capacity of about 850 barrels of which a small fraction was released. 

Tantalum is severely attacked at ambient temperatures and up to about 100°C in aqueous atmospheric environments in the presence of fluorine and hydrofluoric acids. Flourine, hydrofluoric acid and fluoride salt solutions represent typical aggressive environments in which tantalum corrodes at ambient temperatures. Under exposure to these environments the protective TajOj oxide film is attacked and the metal is transformed from a passive to an active state. The corrosion mechanism of tantalum in these environments is mainly based on dissolution reactions to give fluoro complexes. The composition depends markedly on the conditions. The existence of oxidizing agents such as sulphur trioxide or peroxides in aqueous fluoride environments enhance the corrosion rate of tantalum owing to rapid formation of oxofluoro complexes. 

To protect against adverse effects from exposure to hydrofluoric acid in the workplace, the Occnpational Safety and Health Administration has established a permissible exposnre limit (PEL) of 3 ppm averaged over an 8-honr work shift. The National Institnte for Occnpational Safety and Health has fonnd that the concentration of HF that is immediately dangerous to life or health is 30 ppm. 

Workers exposed to an airborne fluoride concentration of 5mg/m complained of eye and respiratory tract irritation and nausea. The lethal oral dose of sodium fluoride for humans has been estimated to be 32-65 mg F/kg of body weight. Effects from ingestion are diffuse abdominal pain, diarrhea, and vomiting excessive salivation, thirst, and perspiration painful spasms of the limbs and sometimes albuminuria." Gastrointestinal effects produced after the acute ingestion of toxic amounts of fluoride likely arise from the corrosive action of hydrofluoric acid, which is produced within the acidic environment of the stomach. Cardiac arrest after accidental exposure to high levels of fluoride has been attributed to the development of hypocalcemia and/or hyperkalemia. ... 

Because fluorine is the most reactive of the elements, free fluorine is rarely found in nature. Fluorine reacts with water to produce ozone and hydrofluoric acid. In humans, the inhalation of high concentrations causes laryngeal spasm and bronchospasm, followed by the delayed onset of pulmonary edema. At sub-lethal levels, severe local irritation and laryngeal spasm will preclude voluntary exposure to high concentration unless the individual is trapped or incapacitated. Two human subjects found momentary exposure to 50 ppm intolerable 2 5 ppm was tolerated briefly, but both subjects developed sore throat and chest pain that persisted for 6 hours. Short-term exposures to concentrations up to 10 ppm were tolerated without discomfort. ... 

HF solutions in contact with skin result in marked tissue destruction undissociated FIF readily penetrates skin and deep tissue, where the corrosive fluoride ion can cause necrosis of soft tissues and decalcification of bone the destruction produced is excruciatingly painful.Fluoride ion also attacks enzymes (e.g., of glycolysis) and cell membranes. The process of tissue destruction and neutralization of the hydrofluoric acid is prolonged for days, unlike other acids, which are rapidly neutral-ized. ° Because of the insidious manner of penetration, a relatively mild or minor exposure can cause a serious burn. When skin contact is with solutions of less than 20%, the burn manifests itself by pain and erythema with a... 

Tantalum is remarkably resistant to corrosion by acids, and is, in fact, referred to as a noble metal. It is not attacked by hydrochloric acid, nitric acid or aqua-regia, whether hot or cold, dilute or concentrated it is not attacked by hot dilute sulphuric acid, but boiling concentrated sulphuric acid dissolves it slowly. It dissolves in hydrofluoric acid, however, although when both metal and add are very pure, solution takes place only very slowly. A mixture of hydrofluoric add and nitric add attacks the metal rapidly, and in contact with platinum or carbon it is readily dissolved by hydrofluoric acid with evolution of hydrogen. Tantalum excellently withstands exposure to sea air, sea-water, sulphur dioxide, and mine effluents.1... 

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