First aid for a unique acid: HF

Eileen B. Segal
Segal Consults, 2701 Liberty St., Easton, PA 18045-2620

Date: April 30, 1998. An emergency on the popular TV program ER dealing with a security guard exposed to hydrofluoric acid (HF) prompted a good deal of discussion on various first-aid treatments. In the show, the man died. Could he have been saved if proper first-aid and medical treatment had been given promptly?

ER is fiction, but the truth is many deaths have resulted from exposure to HF. In the United States, more than 1000 cases of HF exposures are reported annually, but the actual number of exposures is unknown. Thus, a review of current emergency practices seems prudent,as there are questions regarding the best therapy.

Conventional first aid for exposures to all acids has been to rinse with water for 15 min, even longer for HF, and then get medical treatment from professionals. Although studies and experience have shown that HF requires a different approach from other acids, a review of a significant number of material safety data sheets has revealed the same standard emergency treatment- -water, water, and more water. Newer recommended procedures call for immediate flushing, but limited to 5 min, followed by by treatment from emergency responders.

HF is a mean character or as a professor of chemistry was heard to say, "Fluorine can rip a proton off your grandmother." Hydrofluoric acid is an extremely hazardous liquid; it can cause severe skin and eye irritation or deep-seated, slow-to-heal burns.

The insidious hazard is that symptoms may be slow to appear, depending on the concentration, and thus treatment may be delayed. At concentrations above 50%, immediate skin destruction is apparent by a white, marble-like discoloration accompanied by excruciating pain; the discoloration usually proceeds to blister formation. With 20-50% solutions, burns and pain can be delayed for 1 to 8 h; at concentrations of less than 20%, painful erythema (redness of the skin) may be delayed for 24 h. Concentrations as low as 2% may cause symptoms if skin contact is long enough.

HF’s mode of action is to bind calcium whenever contact occurs with skin or other body tissues. In the air-tissue interface, HF penetrates cells as the molecule as the molecule. Once absorbed, it forms soluble salts which are fully dissociable:

HF ® H⁺ + F^-

The dissociation is extremely fast and is highly favored at the physiological pH of 7.4. The fluoride ion is the villain, and it can cause liquefaction necrosis (consistent with alkali damage, not acid damage) of soft tissue and destruction of the supporting tissue by forming insoluble calcium fluoride.

2F^- + Ca²⁺ ® CaF₂

Unlike the action of other acids, which are rapidly neutralized, tissue destruction and neutralization of HF may proceed for days. Although flushing is effective in removing surface acid, it does not affect the F- which may have already penetrated. Because calcium is necessary for cell life, its binding can bring about cell death in a short time. If the exposure covers a large amount of skin surface, excessive amounts of calcium may be inactivated, so that inadequate amounts of Ca²⁺ are available for vital body functions. This causes hypocalcemia, in which heart function is diminished, the heart beat becomes abnormal , and cardiac arrhythmia; notably heart function is diminished, heart beat becomes abnormal, and cardiac arrhythmia (ventricular fibrillation) can occur. Liver and kidney damage may also occur.

The fluoride ion can also bind to magnesium to form insoluble MgF₂:

2F^- + Mg²⁺ ®MgF₂

The binding of magnesium causes hypomagnesemia, an abnormally low magnesium content of the blood plasma, which can cause neuromuscular hyperirritability (a pathological response of muscles and nerves to slight stimuli).

Also to be considered is the formation of other soluble fluorinated salts:

Na⁺ + F^- _ NaF
K⁺ + F^- _ KF

These salts are very toxic at high concentrations. They act as direct cellular poisons by interfering with enzyme mechanisms.

Fingertip injury may cause persistent pain and result in bone loss and nail-bed injury. The healing of skin burns may be prolonged, and extensive scarring may occur.

There are similarities and dissimilarities between the effects of exposure to HF and exposure to other types of acids.

Skin. Like other acids, the extent of injury depends on the amount, concentration, duration of contact, part of the body contacted, and temperature. The toxic effects of HF are primarily due to F^-, which can penetrate tissues and bind intracellular calcium and magnesium. Severe burns can be caused by exposure to concentrated HF (³50%) on 1% or more of the body surface, and to any concentration of HF on at least 5% of the body surface. Initial signs of damage are redness, edema, and blistering. The severe throbbing pain of burns is thought to be due to irritation of nerve endings by increased levels of potassium ions entering the extracellular space to compensate for the reduced levels of calcium ions, which have been bound to the fluoride. Dilute solutions of HF penetrate deeply before dissociation. Surface involvement is minimal and may even be absent.

Respiratory tract. Concentrated solutions and anhydrous hydrofluoric acid produce pungent fumes upon contact with air. These fumes can cause nasal congestion and bronchitis, even in low concentrations. Burns that occur when the vapors or liquid contact to the oral mucosa or upper airway may cause severe swelling, to the point of airway obstruction requiring a tracheostomy. Acute symptoms from inhalation exposure are coughing, choking, and nose and throat irritation, followed (after an asymtomatic period of 1-2 days) by chills, fever, difficulty in breathing, and cyanosis. Anyone with symptoms should be hospitalized for observation and/or treatment. As with dermal exposure, pulmonary edema may be delayed for several hours, even up to two days. This is likely in patients with burns of the face and neck. Pulmonary edema that does not respond to medical treatment may be fatal.

Gastrointestinal tract. If HF is ingested, severe burns to the mouth, esophagus, and stomach can result, with severe pain, bleeding, vomiting, diarrhea, and collapse of blood pressure. Systemic effects can also occur. A number of deaths have occurred after even small amounts of HF.

Eyes. Hydrofluoric acid can cause severe eye burns, with destruction or opacification of the cornea. Blindness may result from severe or untreated exposures. Immediate first aid and specialized medical care are necessary.

Chronic toxicity

The fluoride ion is considered the major concern from a chronic toxicity standpoint. Long-term, exposure to high levels of fluoride salts in water can cause mottling of teeth in children, fluorosis of bone, and sometimes osteosclerosis in adults and children. HF is not considered a developmental or reproductive hazard, although there have been rare cases of mottling of first teeth in infants born to mothers who had high daily intakes of fluoride during pregnancy. However, low doses of fluoride are thought to be essential for normal fetal development in humans. HF is not listed as a carcinogen or suspected carcinogen by the International Agency for Research on Cancer, the National Toxicology Program, OSHA, or the American Conference of Governmental Industrial Hygienists.

When exposures are promptly and successfully treated, results are generally favorable. Improper treatment can result in permanent damage, disability, or death. Treatment is directed toward binding of the fluoride ion to prevent tissue destruction. Speed is of the essence. All potentially exposed personnel should be trained in its handling, and first-aid actions should be planned before beginning work with HF.

AlliedSignal. AlliedSignal Inc., the world’s leading supplier of HF, provides a pamphlet, "Recommended Medical Treatment for Hydrofluoric Acid Exposure" (latest edition, July 1996). The company has shared its information broadly and has provided hundreds of free copies of the informative booklet (call 1-800-622-5002 for a copy). The treatments specified for contact or suspected contact follow.

• Skin contact

1. Move victim immediately to safety shower or other water source and flush affected area thoroughly with large amounts of cool running water.

2. Remove all contaminated clothing while flushing.

3. Rinsing may be limited to 5 min if 0.13% benzalkonium chloride solution or 2.5% calcium gluconate gel is available, with the soaks or gel applied as soon as the rinsing is stopped. If not available, rinsing must continue until medical treatment is rendered.

4. While the victim is being rinsed with water, someone should alert first-aid or medical personnel and arrange for subsequent treatment.

5.Immediately after thorough washing, use one of the measures below:

a. Begin soaking the affected areas in iced 0.13% benzalkonium chloride solution. Use ice cubes, not shaved ice, in order to prevent frostbite. If immersion is not practical, towels should be soaked with iced 0.13% benzalkonium chloride solution and used as compresses for the burned area. Compresses should be changed every 2 to 3 min. Soaks or compresses should be continued until pain is relieved or until more definitive medical treatment is provided. Relief of pain is an indication of the success of treatment; therefore, local anesthetics should be avoided.

b. Start massaging 2.5% calcium gluconate gel into the burn site. Apply gel every 15 min and massage continuously until pain and/or redness disappear or until more definitive medical care is given. It is advisable for the applier to wear surgical gloves.

Note: Clinical experience has shown that both benzalkonium chloride and calcium gluconate gel are effective when used correctly in appropriate situations. In an animal model, benzalkonium chloride soaks appear to be superior to calcium gluconate gel under the experimental conditions used (see Dunn et al., 1992, 1996).

6. After treatment of burned areas is begun, the victim should be examined to ensure there are no other burn sites which have been overlooked.

7. Arrange to have victim seen by a physician. Continue soaks or massaging.

1. Immediately flush the eyes for a least 15 min with large amounts of gently flowing water. Hold the eyelids open and away from the eye during irrigation to allow thorough flushing of the eyes. Do not use benzalkonium chloride solutions described for skin treatment. If sterile 1% calcium gluconate is available, washing may be limited to 5 min, after which the 1% calcium gluconate solution should be used repeatedly to irrigate the eye using a syringe.

2. Take the victim to a doctor, preferably an eye specialist, as soon as possible. Ice-water compresses may be applied to the eyes while transporting the victim (see the box on eye treatment).

• Inhalation

1. Immediately move victim to fresh air and get medical attention.

2. Keep victim warm, quiet, and comfortable.

3. If breathing has stopped, start artificial respiration at once. Make sure mouth and throat are free of foreign material and the airway is open.

4. Oxygen should be administered as soon as possible by a trained individual. Continue oxygen while awaiting medical attention.

5. A nebulized solution of 2.5% calcium gluconate may be administered with oxygen by inhalation.

6. Do not give stimulants unless instructed to do so by a physician.

7. The victim should be examined by a physician and held under observation for at least 24 h.

8. Vapor exposures can cause skin and mucous membrane burns as well as damage to pulmonary tissue. Vapor burns to the skin are treated the same as liquid HF burns.

• Ingestion

1. Have the victim drink large amounts of water as quickly as possible to dilute the acid. Do not induce vomiting. Do not give emetics or baking soda. Never give anything by mouth to an unconscious person.

2. Give several glasses of milk or several ounces of milk of magnesia, Mylanta, Maalox, or the like. The calcium or magnesium in these compounds may act as an antidote.

3. Get immediate medical attention.

DuPont. DuPont’s MSDS, dated Sept. 19, 1995, states, "Flush skin thoroughly with water for 5 minutes. Flushing with water thoroughly for 5 minutes is sufficient to effectively remove HF from skin. Additional flushing time is unnecessary and will delay further treatment."

DuPont has a technical information booklet, "Hydrofluoric Acid/ Anhydrous, Technical: Properties, Uses, Storage, and Handling," which it shares with the public. In addition, DuPont has prepared a 3 x 5" booklet and a 2.25 x 3.75" card with first-aid information for distribution to its customers and potentially exposed personnel.which can easily be carried on their persons (see box for a copy of the card).

Mallinckrodt Baker. This company is another supplier of HF; its MSDS advises a 15-20-min wash and then treatment with Hyamine 1622 ( tetracaine benzethonium chloride) or 0.13% Zephiran Chloride (benzalkonium chloride). However, the MSDS provides a "Note to Physician" in its section on first-aid measures for an alternative first-aid procedure, stating:

"It has been conclusively shown [references given] that flushing the affected area with water for one minute and then massaging HF Antidote Gel (contains calcium gluconate) into the wound until there is a cessation of pain is the most effective first aid treatment available. HF Antidote Gel is available in 25-g tubes....We recommend that any person in contact with HF should carry, or have access to, a tube of HF Antidote Gel at all times; ideally with one tube at the workplace, one on the person" and one at home. For safety’s sake, we believe that HF Antidote Gel should be issued to all employees who may come into contact with HF."

To obtain an MSDS from Mallinckrodt Baker, call 1-800-JTBAKER or 908-859-6911 and follow the voice prompts to obtain information by fax (the catalog number is 6904).

French researchers have produced an antidote for HF called Hexafluorine. It is an amphoteric binding agent which they claim enables it to absorb HF rapidly (a few seconds), preventing the superficial layers of skin from destruction and creating a natural protection against fluoride advance. They claim the "fluoride bound by Hexafluorine is 100 times stronger than when captured by calcium."They also claim that it is safe to use in the eyes.

Hexafluorine has been used in Europe and is now available through a distributor in the U.S. It seems to be a very effective treatment but it has not been approved by the Food and Drug Administration; without FDA backing, legal liabilities become a concern. A lack of sufficient documentation, together with the product’s high cost (>$1500 for a fire-extinguisher type dispenser), would be deterrents to its use. For those who would like more information, the U.S. vendor, Prevor, has a Web page at http://www.prevorusa.com.

Because of the seriousness of exposure to HF, the sooner it is rendered ineffective, the better. The procedures of AlliedSignal have been very effective, that is, a shorter flush time and faster application of calcium gluconate or benzalkonium chloride. At one time, the availability of these substances was a problem. Now calcium gluconate can be ordered in many local pharmacies and is available from Pharmascience Laboratories, 175 Rano St., Buffalo, NY 14207 (1-800-207-4477). Cost: 6 25-g tubes, $27.55/tube; 12 25-g tubes, $22.05/tube. Benzalkonium chloride is sold by Sanofi Winthrop Pharmaceutical, New York, NY.

In this age of litigation, a problem for some may well be a prohibition or reluctance to allow anyone other than a trained or licensed professional to administer any kind of medication. On the other hand, liability may be a larger issue in the case of bodily harm or even death for withholding what is considered an effective treatment.

Employers should make assessments, use up-to-date procedures, and establish a protocol for their workplaces. It is important that all potentially exposed personnel , first-aid responders, and medical staff be trained ahead of time in the chosen protocol.

Back to the fictitious security guard on ER: All we know is that the victim was beyond saving by the time he reached the hospital. Would he have been spared if emergency responders had begun treatment at the scene? It makes one wonder. Anyone dealing with HF should be prepared for that type of emergency. You don’t want to change fiction into reality.

Acknowledgment. I am especially grateful to personnel at AlliedSignal and DuPont for stimulating discussions and materials. Both companies were generous in sharing their information. Thanks are due to Dr. Bernard Blais for many personal discussions and his contribution to this article.

Copyright© 2004 American Chemical Society.
All Rights Reserved.