Hydrogen fluoride (HF) is an extremely toxic substance that is commonly used in many industries including textiles, pesticides, and semiconductors. When combined with water, it is known as hydrofluoric acid. For practical purposes, HF and hydrofluoric acid are considered the same chemical. In addition to severe cutaneous manifestations, HF can have devastating systemic effects. Systemic toxicity can occur by inhalation of gas, fumes, or aerosol, or by absorption through eyes, mucous membranes, and skin.
Hydrofluoric acid is unique among strong acids in that the small size of the HF molecule allows dilute hydrofluoric acid to pass through the epidermis and dermis into the underlying subcutaneous tissue as the undissociated acid. Once in the subcutaneous tissue, the hydrogen and fluoride ions will go along concentration gradient and dissociate to form hydrogen (H+) ions and fluoride (F-) ions. The high electronegativity of the fluoride ions causes interaction with biological macromolecules to cause tissue necrosis and destruction. This process continues unabated until the fluoride complexes with calcium ions to precipitate as calcium fluoride. Thus, calcium gluconate gel, which also penetrates through the epidermis and dermis into subcutaneous tissue, is the preferable treatment for dermal exposure to hydrofluoric acid. Pain is generally a good end point for this process in that when there are free fluoride ions in the subcutaneous tissue there is ongoing pain, but when the calcium ions form a calcium fluoride sink, then the pain and macromolecular destruction ceases.
Dermal contact produces immediate onset of redness, pain, and blistering that progress to deep chemical burns and skin necrosis. At concentrations less than 20%, erythema and pain may be delayed for 24 hours and may not be reported until significant tissue injury has occurred. At concentrations between 20% and 50%, erythema and pain may be delayed for 8 hours and may not be reported until tissue injury has occurred. Concentrations greater than 50% may result in immediate pain and erythema, rapid destruction of tissues, and acute systemic toxicity.
Respiratory symptoms may be immediate or delayed, up to 35 hours, and include sore throat, nasal irritation, sneezing, rhinorrhea, and cough. Severe exposures also produce dyspnea, wheezing, chest tightness, cyanosis, laryngeal swelling, chemical pneumonitis, pulmonary edema, and collapsed lung.
Systemic effects of HF toxicity may take days to appear and include nausea, vomiting, abdominal pain, and cardiac arrhythmias. Absorption of HF interferes with calcium metabolism, resulting in hypocalcemia with resultant tetany, seizures, and cardiovascular collapse. It may also produce hypomagnesemia and hyperkalemia with resultant paresthesias, weakness, paralysis, and cardiac arrest.
Victims at high risk for systemic effects include those with burns over 1% of body surface with a HF solution > 50% concentration, or those with burns to 5% of body surface at any concentration. Deaths have been reported with 2.5% of body surface exposure.
The Immediately Dangerous to Life or Health (IDLH) air concentration of HF is 30 ppm.
Codes
ICD10CM: T30.0 – Burn of unspecified body region, unspecified degree
SNOMEDCT: 218153003 – Burning caused by hydrofluoric acid
A burn is an injury to the skin resulting from direct contact or exposure from extreme heat or cold, friction, electricity, or chemicals. First-degree burns are superficial with red skin, pain, and no blistering. Second-degree burns involve destruction of the second layer of skin, causing blistering, swelling, and pain. Third-degree burns involve destruction of all layers of the skin, including fat, muscle, blood supply, and sometimes bone. Third-degree burns do not have pain associated with them.
Airway burns can affect the nose, throat, and windpipe and are typically caused by inhaling smoke, steam, or toxic fumes. The airway swells, which can cause suffocation. It is often difficult to determine the extent of airway burns.
It is important to try to assess the seriousness of a burn, which is determined, primarily, by the size of the burn and its depth. When in doubt, treat as a serious burn.
Who’s At Risk
Burns affect people of all ages, races, and sexes.
Hydrogen fluoride, also known as hydrofluoric acid, is an extremely toxic substance found in industries using or producing textiles, pesticides, ceramics, dyes, glass, petroleum, refrigerants, and semi-conductors. People working in these industries are more likely to be exposed to hydrogen fluoride. Farmers using pesticides may also be at risk.
Signs & Symptoms
Burns can appear in a variety of ways, depending on the extent and severity of the burn, but red, white, or charred skin with peeling, swelling, and blisters is typical.
Minor burns are the size of a quarter or smaller. All first-degree burns and any second-degree burns that are smaller than 2-3 inches in diameter that are NOT on the hands, feet, face, groin, buttocks, or over a major joint are considered minor burns.
Severe burns are deep and may cover a large portion of the body or more than one area of the body. Second-degree burns that are larger than 2-3 inches in diameter that are on the hands, feet, face, groin, buttocks, or over a major joint and ALL third-degree burns are considered severe burns.
Airway burns can include a charred mouth; singed facial hair; visible burns on the head, face, or neck; and coughing or difficulty breathing.
Self-Care Guidelines
Burns caused by chemical exposure require quick first aid while awaiting medical care; doing so can lessen the chemical's harmful effects. Your local Poison Control Center can best provide this information. The following general measures can be taken while awaiting professional care:
Remove the chemical, including clothing or anything on the person that came in contact with it, taking care to not spread the chemical elsewhere.
Continually flush the affected area with fresh water.
If 15 minutes have passed, apply cool, wet compresses to help relieve pain.
Protect the burn area from friction by covering it with a loose, dry, sterile dressing.
Note: Do not leave the victim alone, and watch for signs of shock.
In the case of burns to the eye, seek medical attention. General first aid is as follows:
Flush the eyes with cool water; if water increases pain symptoms, stop.
Using light pressure, apply a cool compress to the eye.
Note: Do not rub the eye, and do not cough or breathe on the burn.
When to Seek Medical Care
Always seek immediate professional medical care for hydrogen fluoride burns.
Treatments
The physician will likely determine the extent of the burn. In the case of an airway burn, bronchoscopy or lung scan may be done. Therapy and medications can reduce lung damage. Eyes may need to be irrigated and/or medicated.
Patient Information for Hydrogen fluoride burns