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CHEMINFO Record Number: 45
CCOHS Chemical Name: Hydrogen fluoride

Anhydrous hydrofluoric acid
Anhydrous HF
Anhydrous hydrogen fluoride
Fluorohydric acid (non-specific name)
HF (non-specific name)
Hydrogen fluoride gas

Chemical Name French: Fluorure d'hydrogène
CAS Registry Number: 7664-39-3
UN/NA Number(s): 1052
RTECS Number(s): MW7875000
EU EINECS/ELINCS Number: 231-634-8 (hydrogen fluoride)
Chemical Family: Mineral acid gas / inorganic acid gas / halogenated inorganic acid gas / hydrogen halide / hydrogen fluoride
Molecular Formula: F-H
Structural Formula: H-F and (H-F)6


Appearance and Odour:
Colourless gas at or above 19.5 deg C; fuming liquid below 19.5 deg C; sharp, penetrating odour.(2,24,25)

Odour Threshold:
0.04 ppm (0.03 mg/m3) (minimum perceptible concentration); 0.04 to 0.14 ppm (0.03 to 0.11 mg/m3) (3,21)

Warning Properties:
GOOD - TLV is more than 10 times the odour threshold.

Hydrogen fluoride is available in anhydrous form (either as a gas or a liquid), or as a solution in water (usually 30-70%; known as hydrofluoric acid). Although hydrogen fluoride exists in both the gaseous and liquid forms, in general, any HF released from its container would rapidly gas off into the air. Therefore, this CHEMINFO profile predominantly reviews the hazards and control information for hydrogen fluoride gas. Where relevant, reference will be made to hydrogen fluoride liquid. For information on hydrogen fluoride solutions in water, refer to the CHEMINFO profile on hydrofluoric acid. Anhydrous hydrogen fluoride is available in grades ranging from 99.0% to 99.96%. The major impurities are water, sulfur dioxide and hydrofluosilic acid.(25,26,27) Hydrogen fluoride is shipped in bulk in tank cars and tank trucks, or as a liquid in cylinders under its own vapour pressure of 2.1 kPa (0.3 psig) at 20 deg C.(24,25). The transport containers are usually of carbon steel construction.(25)

Uses and Occurrences:
Hydrogen fluoride is mainly used in the production of fluorocarbons, aluminum fluoride and synthetic cryolite (sodium aluminum fluoride). It is also used in the production of uranium hexafluoride; hydrofluoric acid solutions; and organic and inorganic fluorine-containing compounds; as an electrolyte in the manufacture of pure elemental fluorine; and in detergent alkylation; and in dye chemistry.(3,21,25-28) Liquid hydrogen fluoride is used as a catalyst in alkylation processes converting olefins and isoparaffins to gasoline; as a solvent; for cryogenic measurements; and as a fluorinating agent.(25,33)
Hydrogen fluoride can be released to the environment by volcanoes and sea salt aerosol, as well as from manufacturing and processing facilities (such as aluminum production), and welding processes. However, because of its very high reactivity, it is unlikely to remain in its original form for very long. (2,21)


Colourless gas at or above 19.5 deg C; fuming liquid below 19.5 deg C; sharp, penetrating odour. Will not burn. Cylinders or tanks may rupture and explode if heated. Highly reactive. Contact with metals, such as iron or steel, slowly releases flammable and potentially explosive hydrogen gas. VERY TOXIC, CORROSIVE GAS. May be fatal if inhaled. CORROSIVE to the nose, throat and respiratory tract. Causes lung injury-effects may be delayed. Absorbed fluoride can cause irregular heartbeat, nausea, vomiting, dizziness, and seizures. Long-term exposure may cause skeletal fluorosis (weakened bone structure).


Effects of Short-Term (Acute) Exposure

Hydrogen fluoride (HF) is an extremely corrosive gas. Low concentrations (a few ppm) can cause irritation of the nose, throat, eyes and respiratory tract. Higher concentrations can cause severe burns to the throat, airways and lungs. Absorbed fluoride can cause metabolic imbalances with irregular heartbeat, central nervous system depression, and seizures. Fluid accumulation in the lungs and irregular heartbeat has led to deaths within hours following inhalation and, in some cases, concurrent skin contact with unknown concentrations of HF.(2,21)
With serious exposures, throat irritation, coughing, chest pain, nausea and perhaps some difficulty breathing may be experienced during exposure. These symptoms usually resolve once exposure stops. The victim may feel fine and may even return to work. This latent period can last from 1-24 hours, depending on the extent of the exposure. Within 24-48 hours, the victim may experience a rapidly worsening difficulty in breathing, accompanied by coughing. These symptoms are due to the development of a life- threatening accumulation of fluid in the lungs (pulmonary edema). Severe short-term exposures may result in long- lasting effects such as shortness of breath and pulmonary emphysema (larger than normal air spaces in the lungs which decrease lung efficiency).
Exposure of 24 male volunteers to 0.24-6.34 ppm (cited as 0.2-5.2 mg/m3) for 1 hour caused upper airway symptoms even at the lowest concentration. Most symptoms disappeared within 4 hours after exposure.(9) Exposure of 19 male volunteers to 0.24-0.73, 0.85-2.92 or 3.05-6.34 ppm (cited as 0.2-0.6, 0.7-2.4 or 2.5-5.2 mg/m3) for 1 hour resulted in inflammatory changes in the airways at concentrations greater than 0.73 ppm.(49) Exposure of 10 male volunteers to 4.02-4.76 ppm (cited as 3.3-3.9 mg/m3) for 1 hour resulted in an immediate inflammatory response in the nose.(50)
Following the accidental release of HF into a community, the most commonly reported symptoms were burning throat, headache, and shortness of breath. Nausea, vomiting, and dizziness were commonly reported in those hospitalized. Affects on breathing were detected in lung function tests. A concentration of 10 ppm HF was measured downwind 1-hour after the release.(7)
Five volunteers tolerated average concentrations of 1.4 ppm for 15 days to over 4.2 ppm for 25-50 days (6 hours/day). Up to 2 ppm was reported to have no noticeable effect. At 2.6-4.7 ppm, some discomfort and slight irritation of the nasal passages was reported.(17,21)

Skin Contact:
Hydrogen fluoride is corrosive and exposure to the gas is expected to cause skin irritation. Any skin contact with hydrogen fluoride gas or liquid would also involve significant inhalation exposure. See "Inhalation" above for details.
"Skin burning" was reported in people exposed to HF accidentally released into the air. A concentration of 10 ppm was measured downwind 1 hour after the release.(7)

Eye Contact:
The gas or liquid can dissolve in moisture on the surface of the eyes, forming corrosive hydrofluoric acid.
Twenty-four male volunteers exposed to 0.24 to 6.4 ppm (cited as 0.2 to 5.2 mg/m3) for 1 hour reported eye irritation, even at the lowest concentration.(9) Five volunteers repeatedly exposed to 2.59-4.74 ppm reported a slight stinging sensation in the eyes.(17,21) Eye irritation was commonly reported by members of a community following accidental release of HF. A concentration of 10 ppm was measured downwind 1 hour after the release.(7)

Ingestion is not an applicable route of exposure for gases and the liquid will rapidly gas off as soon as it is exposed to the environment.

Effects of Long-Term (Chronic) Exposure

The major health hazards of hydrogen fluoride exposure are related to the irritant and corrosive effects experienced during short-term exposures.

FLUOROSIS: Fluoride is a bone seeker, and exposure to excessive amounts will weaken and degenerate the bone structure (osteosclerosis). Early signs of the disease (e.g. denser and thicker bones) may only be detected with x- ray examination. Early symptoms include pain in the joints of the hands, feet, knees and spine and a limited range of joint movement. There may also be heart, nerve, and intestinal problems. In some cases, greyish or chalk-white discolouration and pitting of the teeth may be noted. The disease is called fluorosis. The amount of fluoride stored in the bones usually increases with increasing fluoride intake.(1,3,8) Excess fluoride is removed slowly from the body over a period of years. Skeletal fluorosis may be slowly and partially reversible.(13)
There have been reports of employees with long-term exposure to hydrogen fluoride and/or fluoride dust developing very early signs of fluorosis.(1,2,21) Occupational fluorosis of crippling severity has rarely been seen since the 1930's and 1940's.(11,21) One large study followed 2258 aluminum workers exposed to fluoride (form not specified, but probably hydrogen fluoride and fluoride dust) for an average of 17.6 years. Exposures ranged up to 2.0 mg HF/m3 (actual measurements and sampling methods not provided). Possible or definite fluorosis was observed in 20.5% of cases. Of these cases, 14% were very early cases of possible fluorosis (multiple joint pains, limited motion in at least two joints or the spine and initial ossification observed on x-rays). Initial fluorosis (Stage 0) was observed in 5.12% of the cases, Stage I fluorosis in 1.0% and Stage II fluorosis in 0.05%. There were no cases of Stage III fluorosis.(10) A study of 107 potroom workers with severe fluoride exposure (2.4 to 6. 0 mg F/m3) for an average of 19.1 years showed that a large percentage (96% of 79 employees x-rayed) had developed varying degrees of skeletal fluorosis, but without physical impairment or noticeable signs or symptoms of the disease.(12)
An extensive review has concluded that the incidence of osteosclerosis is often high in employees exposed to airborne fluoride concentrations of higher than 2.5 mg F/m3 and/or when urinary levels of fluoride exceed 9 mg/L over long periods of time.(1,11) With higher air fluoride concentrations and with long continued employment, osteosclerosis develops more rapidly, the extent and the degree of abnormality are greater, the stage of osteosclerosis tends to be higher and the percentage of workers showing osteosclerosis is greater.(11)

Lungs/Respiratory System:
It is difficult to draw conclusions regarding the possibility of respiratory effects developing following long-term, low-level HF exposure. Many of the available studies are limited because employees were exposed to other potentially harmful chemicals at the same time. Nevertheless, reviews have concluded that HF exposure less than the occupational exposure limit would not cause lung disease, with the possible exception of increased frequency of upper respiratory infections in aluminum potroom workers.(11,21) Exposure to HF may increase the reactivity of the airways (bronchial hyperreactivity).(20) Increased reactivity of the airways may lead to symptoms such as wheezing and shortness of breath upon exposure to respiratory irritants or cold air.
One study of employees exposed to hydrogen fluoride and fluoride dusts in aluminum smeltering showed respiratory effects (lower forced expiratory volume, increased cough and sputum production) in the highest exposure group (more than 50% of working time spent in potroom).(19) No firm conclusions about the respiratory effects of hydrogen fluoride can be drawn from this study. Actual exposure concentrations are unknown (the employees wore respirators) and there was exposure to other respiratory irritants at the same time.
One study describes inflammation of the upper respiratory tract and nose, progressing to degeneration of the membranes and even perforation of the nasal septum. The exposures were described as "elevated".(11, unconfirmed) There are no further details available.

A number of studies have commented on the possibility that long-term fluoride exposure may cause certain skin disorders (e.g. dermatitis, rashes). Review of this literature does not reveal an association between long-lasting skin injury and exposures below 2.5 mg F/m3.(11)

Kidneys/Urinary System:
A number of studies have examined the possibility that long-term fluoride exposure may cause kidney effects. Reviews of this literature have concluded that it is unlikely that HF exposure below occupational exposure limits would cause kidney injury.(2,11)


It is not possible to draw conclusions about the potential carcinogenicity of hydrogen fluoride based on the available information. A number of studies have evaluated occupational groups exposed to fluorides, as well as other chemicals. Excess cancer rates have been reported in some groups with exposure to hydrogen fluoride and fluoride dusts. However, due to the concurrent exposures to other chemicals and other significant study design limitations, it is not possible to draw any specific conclusions about hydrogen fluoride.(1,2)

The International Agency for Research on Cancer (IARC) has not evaluated the carcinogenicity of this chemical.

The American Conference of Governmental Industrial Hygienists (ACGIH) has not assigned a carcinogenicity designation to this chemical.

The US National Toxicology Program (NTP) has not listed this chemical in its report on carcinogens.

Teratogenicity and Embryotoxicity:
Hydrogen fluoride is not expected to cause developmental effects.(2,51) There is no specific human information available. There are insufficient details available to evaluate the one animal study located.

Reproductive Toxicity:
There is no specific human or animal information available for hydrogen fluoride. No conclusions can be drawn about the potential for fluorides to cause reproductive effects.(2)

The available information does not suggest that hydrogen fluoride is mutagenic. In one limited study, positive results (sister chromatid exchanges in peripheral blood lymphocytes) were obtained in a small number of employees exposed to HF and several other chemicals.(18) In general, fluorides are only mutagenic at doses that are highly toxic to cells and whole animals.(2)

Toxicologically Synergistic Materials:
There is no information available.

Potential for Accumulation:
Hydrogen fluoride gas can enter the body through inhalation or skin contact. Absorbed fluoride is either excreted in the urine or taken up by bones and teeth. Fluoride stored in bones and teeth may be eliminated from the body over several years. Fluoride passes through the placenta and occurs in very low concentrations in saliva, sweat and milk.(1,2)


Take proper precautions to ensure your own safety before attempting rescue (e.g. wear appropriate protective equipment, use the "buddy" system). Remove source of contamination or move victim to fresh air. If breathing is difficult, oxygen and administration of 2.5% calcium gluconate may be beneficial if administered by trained personnel, preferably on a doctor's advice. DO NOT allow victim to move about unnecessarily. Symptoms of pulmonary edema can be delayed up to 48 hours after exposure. If breathing has stopped, trained personnel should begin artificial respiration (AR) or, if the heart has stopped, cardiopulmonary resuscitation (CPR) immediately. Avoid mouth-to-mouth contact by using mouth guards or shields. Immediately transport victim to an emergency care facility.

Skin Contact:
High concentrations of hydrogen fluoride (HF) gas may cause skin burns. The liquid rapidly gases off when exposed to room temperature. In these cases, inhalation exposure is the most significant concern. If skin contact has occurred, avoid direct contact with residual HF. Wear chemical protective clothing. Remove, double bag and seal contaminated clothing, shoes and leather goods (e.g. watchbands, belts). As quickly as possible, flush with lukewarm, gently flowing water. Limit flushing with water to 5 minutes if 0.13% benzalkonium chloride solution or 2.5% calcium gluconate gel is available. If these treatments are not available, continue flushing until medical treatment is available. If using benzalkonium chloride, soak the affected area(s) in 0.13% benzalkonium chloride solution chilled with ice cubes. If immersion of the affected area is not practical, soak towels with iced 0.13% benzalkonium chloride solution and use as compresses on the site of contact. Change compresses every 2-3 minutes. Continue until medical treatment is available. If using 2.5% calcium gluconate gel, massage gel into the site of contact. Apply gel every 15 minutes and massage continuously until medical treatment is available. Immediately transport victim to an emergency care facility. Discard contaminated clothing, shoes and leather goods.

Eye Contact:
HF gas or liquid can react with moisture in the eye(s) to form corrosive hydrofluoric acid, however inhalation is the principal concern. If irritation occurs, remove source of contamination or move victim to fresh air. If irritation persists, immediately flush the contaminated eye(s) with lukewarm, gently flowing water for 20 minutes, by the clock, while holding the eyelid(s) open. Neutral saline solution may be used as soon as it is available. Take care not to rinse contaminated water into the unaffected eye. If sterile 1% calcium gluconate is available, limit flushing to 5 minutes. Then, use the 1% calcium gluconate solution to repeatedly rinse the eye(s). Immediately transport victim to an emergency care facility. Continue flushing with water, neutral saline or 1% calcium gluconate during transport, if at all possible. NOTE: DO NOT use any of the hydrofluoric acid skin treatment preparations for burns to the eyes.

Ingestion is not an applicable route of exposure for HF.

First Aid Comments:
Provide general supportive measures (comfort, warmth, rest).
Consult a doctor and/or the nearest Poison Control Centre for all exposures.
Some recommendations in the above sections may be considered medical acts in some jurisdictions. These recommendations should be reviewed with a doctor and appropriate delegation obtained, as required.
All first aid procedures should be periodically reviewed by a doctor familiar with the material and its conditions of use in the workplace.

Note to Physicians:
For more information on first aid procedures and medical advice, refer to references 34, 35 and 52.


Flash Point:
Not combustible (does not burn)

Lower Flammable (Explosive) Limit (LFL/LEL):
Not applicable

Upper Flammable (Explosive) Limit (UFL/UEL):
Not applicable

Autoignition (Ignition) Temperature:
Not applicable

Sensitivity to Mechanical Impact:
Not sensitive. Stable material.

Sensitivity to Static Charge:
There is no information available for the gas. Liquid hydrogen fluoride (100% HF) will not accumulate static charge, since the electrical conductivity is high. Since it does not burn, HF will not be ignited by a static discharge.

Electrical Conductivity:
1 X 10(8) pS/m at 0 deg C (liquid hydrogen fluoride) (27)

Combustion and Thermal Decomposition Products:
Nothing more toxic than hydrogen fluoride gas itself.

Fire Hazard Summary:
Hydrogen fluoride (HF) is not flammable, but it is extremely corrosive and very toxic. If it is involved in a fire, it presents a very serious health hazard. Contact of HF (particularly in dilute aqueous solutions) with some metals produces flammable and potentially explosive hydrogen gas. A substantial amount of heat is generated when HF is mixed with water. Closed containers may rupture violently and suddenly release large amounts of product when exposed to fire or excessive heat for a sufficient period of time.

Extinguishing Media:
Hydrogen fluoride does not burn. Use extinguishing agents compatible with acid and appropriate for fire surrounding HF containers. Use water spray to keep fire exposed containers cool.

Fire Fighting Instructions:
Evacuate area and fight fire from a safe distance or protected location. Approach fire from upwind to avoid corrosive and very toxic HF gas.
If possible, isolate HF cylinders or containers and move from the fire area if this can be done without risk, and protect personnel. Otherwise, fire-exposed containers or tanks should be cooled by application of hose streams and this should begin as soon as possible and should concentrate on any unwetted portions of the container. Water is very effective in absorbing HF fumes escaping from leaking containers of HF. However, DO NOT direct water at open or leaking containers and take precautions not to get water into the HF containers. If water contacts the anhydrous liquid, a substantial amount of heat will be generated and there is a danger of violent HF splashing.

Protection of Fire Fighters:
HF is corrosive and very hazardous to health. Do not enter without wearing specialized protective equipment suitable for the situation. Firefighter's normal protective clothing (Bunker Gear) will not provide adequate protection. A full-body encapsulating chemical protective suit with positive pressure self-contained breathing apparatus (NIOSH approved or equivalent) may be necessary.


NFPA - Health: 4 - Very short exposure could cause death or major residual injury. (Hydrogen fluoride, anhydrous)
NFPA - Flammability: 0 - Will not burn under typical fire conditions. (hydrogen fluoride, anhydrous)
NFPA - Instability: 1 - Normally stable, but can become unstable at elevated temperatures and pressures, or may react vigorously, but non-violently with water. (hydrogen fluoride, anhydrous)


Molecular Weight: 20.01 (monomeric form); 54 (at 25 deg C and 101.3 kPa)

Conversion Factor:
1 ppm = 0.82 mg/m3; 1 mg/m3 = 1.22 ppm at 25 deg C (HF monomer) (calculated); 1 ppm=2.20 mg/m3; 1 mg/m3 = 0.45 ppm at 25 deg C (corresponding to a molecular weight of 54)

Physical State: Liquid
Melting Point: -83.55 deg C (-118.4 deg F) (25,36)
Boiling Point: 19.52 deg C (67.14 deg F) (26,37)
Relative Density (Specific Gravity): 0.99 (28); 0.96 (26) at 19.5 deg C (liquid) (water = 1); 2.201 g/mL at 25 deg C and 101.3 kPa (absolute density) (gas) (24)
Solubility in Water: Soluble in all proportions (2,28)
Solubility in Other Liquids: Very soluble in ethanol; moderately soluble in benzene, toluene, xylene; slightly soluble in diethyl ether and tetralin.(36)
Coefficient of Oil/Water Distribution (Partition Coefficient): Log P (oct) = 0.23 (estimated) (38)
pH Value: Not available
Acidity: Liquefied HF gas is one of the strongest acids known.(25,36) In water solution, HF is a fairly weak acid; (25,27,36)
Dissociation Constant: pKa = 3.19 (Ka = 6.46 X 10(-4)) (25,27,36)
Viscosity-Dynamic: 0.256 mPa.s (0.256 centipoises) at 0 deg C (liquid) (24,25)
Surface Tension: 10.2 mN/m (10.2 dynes/cm) at 0 deg C (24,25); 8.6 mN/m (8.6 dynes/cm) at 19.5 deg C (liquid) (25)
Vapour Density: 1.86 at 25 deg C (air = 1) (24,26) This corresponds to a Molecular Weight of 54. See Physical Properties Comments.
Vapour Pressure: 107 kPa abs (803 mm Hg; 1.06 atm) at 21.1 deg C (26); 188 kPa (1413 mm Hg; 1.86 atm) at 37.8 deg C (24)
Vapour Pressure at 50 deg C: 274 kPa (2058 mm Hg; 2.7 atm) at 50 deg C (24)
Saturation Vapour Concentration: Not applicable; gas at or above 19.5 deg C
Evaporation Rate: Not applicable; gas at or above 19.5 deg C
Henry's Law Constant: Not available
Critical Temperature: 188 deg C (370.4 deg F) (24,25,26)
Critical Pressure: 6484 kPa abs (64 atm) (24,26)

Other Physical Properties:
TRIPLE POINT: -83.4 deg C (-118.1 deg F) (24,26)
DIELECTRIC CONSTANT: 83.6 at 0 deg C (liquid) (24,25,27)

Physical Properties Comments:
There is an association of anhydrous hydrogen fluoride molecules in the gaseous and liquid states at normal room temperatures and pressures. At normal room temperatures and presssures, the mean degree of association is approximately 2.5-2.75, corresponding to an average molecular weight of about 50-55. This molecular association affects certain physical properties, such as boiling point and density. As a result, the actual density of the gas is greater than would be calculated from its monomeric formula.(3,25,27,48)


Normally stable. Hydrogen fluoride is one of the most stable diatomic molecules.(25,27)

Hazardous Polymerization:
Hydrogen fluoride tends to associate by means of hydrogen bonds to form polymers in both the liquid and gaseous states.(25,27) This polymerization is not hazardous.

Incompatibility - Materials to Avoid:

NOTE: Chemical reactions that could result in a hazardous situation (e.g. generation of flammable or toxic chemicals, fire or detonation) are listed here. Many of these reactions can be done safely if specific control measures (e.g. cooling of the reaction) are in place. Although not intended to be complete, an overview of important reactions involving common chemicals is provided to assist in the development of safe work practices.

Hydrogen fluoride is highly reactive.
WATER - dissolves in water with substantial generation of heat forming extremely corrosive hydrofluoric acid.(39,40)
METALS (e.g. iron, steel; particularly in the presence of water) - may react to form flammable and potentially explosive hydrogen gas.(25,27,40,41)
ANTIMONY OR ARSENIC CONTAINING METAL ALLOYS - can form extremely toxic stibine from antimony containing metal alloys and extremely toxic arsine from arsenic containing alloys.(41)
CYANOGEN FLUORIDE - may polymerize explosively at normal temperatures; may decompose violently at -80 deg C.(41)
BISMUTHIC ACID - reacts violently with the evolution of ozonized oxygen.(39,41)
METHANESULFONIC ACID - electrolysis of a mixture produces explosive oxygen difluoride.(41)
NITRIC ACID and LACTIC ACID - mixtures of the 3 acids, are unstable and can explode.(39,41)
PROPYLENE GLYCOL and SILVER NITRATE - may form explosive silver fulminate.(41)
STRONG BASES (e.g. ammonium hydroxide, sodium hydroxide or calcium oxide) - may react very violently.(39,41)
SULFURIC ACID - mixing the two acids may be violent.(41)

Hazardous Decomposition Products:
None reported

Conditions to Avoid:
High temperatures, water.

Corrosivity to Metals:
Hydrogen fluoride is corrosive to naval bronze, metals containing silica (such as cast iron), type 400 stainless steels, hardened steels, tantalum and titanium, and aluminum above 43 deg C. It is not corrosive to dry aluminum bronze, carbon steel (without non-metallic inclusions) up to 65 deg C, Hastelloy, Inconel, Monel, copper, nickel, aluminum up to 43 deg C, stainless steels (types 304/347, 316 and 20 Cb 3), platinum and lead.(24- 27,42,43)

Corrosivity to Non-Metals:
Hydrogen fluoride attacks plastics, such as chlorinated polyvinyl chloride (CPVC), elastomers, such as butyl GR-1, ethylene-propylene, isoprene, natural rubber and neoprene, glass and silicate ceramics, and leather. ABS (acrylonitrile-butadiene-styrene), Epoxy, Teflon (FEP and TFE), high molecular weight polyethylene, and KEL-F are resistant to HF.(24-27,40,42,44)


LC50 (mouse): 170 ppm (4-hour exposure); cited as 342 ppm (1-hour exposure) (5)
LC50 (male, rat): 655 ppm (4-hour exposure); cited as 1307 ppm (1-hour exposure) (4)
LC50 (male, rat): 2042 ppm (30-minute exposure (4)
LC50 (male, rat): 2690 ppm (15-minute exposure) (4)
LC50 (male, rat): 4970 ppm (5-minute exposure) (4)

Eye Irritation:

Eye irritation was observed in rats exposed to 6-68% of the LC50 for up to 1 hour.(4) Rats and mice exposed to lethal concentration developed eye irritation and clouding of the corneas.(5)

Skin Irritation:

Skin irritation was observed in rats, mice and guinea pigs exposed to lethal airborne concentrations.(4,5)

Effects of Short-Term (Acute) Exposure:

Hydrogen fluoride (HF) is corrosive to the respiratory tract, causing severe irritation and fluid accumulation in the lungs with deaths. Severe liver and/or kidney injury has been observed in animals exposed to high concentrations.

Rats and guinea pigs with brief inhalation exposures (up to 1 hour) to lethal concentrations showed nose irritation, respiratory distress, general weakness, decreased body weight and some deaths. Inflammation and tissue death in the nasal cavity, skin irritation, and kidney, liver and bone marrow damage were observed, but not statistically evaluated. Lower concentrations produced irritation of the nose and upper respiratory tract. Only very mild signs were seen in rats exposed to 307 ppm for 15 minutes or 103 ppm for 60 minutes.(4) Rats and mice exposed to lethal concentrations showed signs of respiratory distress. Autopsy showed evidence of lung injury.(5) Rabbits and guinea pigs were exposed to 30 to 9800 ppm for 5 minutes to 41 hours. Respiratory tract irritation was noticeable in all animals at all concentrations, but exposures of 60 ppm or lower produced mild effects. As the concentration increased, corrosion of the nasal passages was observed. Animals survived exposures of up to 30 ppm for 41 hours, but exposures to 300 ppm for 2 hours or more were fatal. Autopsy showed lung, heart, liver, spleen and renal injury.(6) In a study designed to maximize delivery of HF to the lower airways (animals were orally cannulated and HF was delivered directly to the middle section of the trachea), female rats were exposed to 135-1764 ppm for 10 minutes. It was determined that the estimated threshold for serious changes was 1357 ppm. It was concluded that a 10-minute exposure of 130 ppm would produce significant irritation, but not serious or irreversible damage in humans.(23)

Effects of Long-Term (Chronic) Exposure:

Long-term exposure to HF can cause severe irritation and corrosive effects to the respiratory system, including the lungs. Deaths have been observed at 30 ppm for less than 5 weeks. Severe liver and kidney damage has also been observed. Skeletal fluorosis has also been observed in animals exposed to fluorides. These studies are not reviewed here, because the effects are well-defined in humans.

Rats, mice, guinea pigs, rabbits and dogs were exposed to 8.6 or 30 ppm over 5 weeks (166 exposure hours; 29 days exposure). Exposure to 30 ppm was lethal to rats and mice (100% mortality). Autopsy showed lung injury (bleeding and fluid accumulation) in dogs, rabbits and rats exposed to 30 ppm. Rats also showed severe kidney damage (degeneration and necrosis) and bleeding under the skin, particularly around the eyes and on the feet. Ulceration of the scrotum was observed in the dogs. At 30 and 8.6 ppm, increased fluoride content of the bones and teeth was observed. One dog exposed to 8.6 ppm showed localized bleeding in the lung. Otherwise, no significant effects were observed at 8.6 ppm.(15) Rabbits, guinea pigs and monkeys were exposed to 18.5 ppm (cited as 0.0152 mg/L) for 50 days. Two out of three guinea pigs died. Severe lung (bleeding and inflammatory effects) and liver (fatty changes, congestion and necrosis) damage were observed in all guinea pigs. The rabbits also showed lung and liver injury, as well as kidney damage (extensive degeneration and necrosis). The monkeys did not show any significant lung or liver injury, but kidney injury (degenerative and inflammatory changes) was evident.(14)

Teratogenicity, Embryotoxicity and/or Fetotoxicity:
The one study identified cannot be obtained in English and cannot be evaluated.(22)

There is insufficient evidence available to conclude that HF is a mutagen. The only study available for HF using live animals is weak and inconclusive. Negative results were obtained in bacteria and positive results were obtained in a limited study in fruit flies. In general, fluorides have not produced mutagenic effects except in the presence of severe toxicity in cells or whole animals.(2)
Positive results (chromosomal damage in bone marrow cells) were obtained in female rats exposed to 1.22 ppm (cited as 1.0 mg/m3) for 1 month. Negative results were obtained in a dominant lethal test using mice exposed by inhalation to 1.22 ppm (cited as 1.0 mg/m3) for up to 4 weeks.(16) The complete original study is not available in English. Only one concentration was tested and the increased rate of damaged cells was due largely to an increase in hyperploidy, the significance of which is unknown.(2)
Negative results (gene mutation) were obtained for HF (form unspecified) in bacteria.(51, unconfirmed)
Positive results (sex-linked recessive lethality) were obtained in poorly reported studies using fruit flies (Drosophila).(51, unconfirmed)


Selected Bibliography:
(1) International Programme on Chemical Safety (IPCS). Fluorides. Environmental Health Criteria; 227. World Health Organization, 2002
(2) Agency for Toxic Substances and Disease Registry (ATSDR). Toxicological profile for fluorides, hydrogen fluoride, and fluorine (F). TP-91/17. Public Health Service, US Department of Health and Human Services, Apr. 1993
(3a) Perry, W.G., et al. The halogens: hydrogen fluoride, HF. In: Patty's industrial hygiene and toxicology. 4th ed. Edited by G.D. Clayton, et al. Vol. II. Toxicology. Part F. John Wiley and Sons, Inc., 1994. p. 4449-4465, 4479-4482
(3b) Teitelbaum, D.T. The Halogens. In: Patty's toxicology. 5th ed. Edited by E. Bingham, et al. Vol. 3. Chapter 48. John Wiley and Sons, 2001
(4) Rosenholtz, M.J., et al. A toxicopathologic study in animals after brief single exposures to hydrogen fluoride. American Industrial Hygiene Association Journal. Vol. 24 (May-June 1963). p. 253-261
(5) Wohlslagel, J., et al. Toxicity of solid rocket motor exhaust: effects of HCl, HF and alumina on rodents. Journal of Combustion Toxicology. Vol. 3, no. 1 (Feb. 1976). p. 61-70
(6) Machle, W., et al. The effects of the inhalation of hydrogen fluoride. I. The response following exposure to high concentrations. Journal of Industrial Hygiene. Vol. 16, no. 2 (Mar. 1934). p. 129-145
(7) Wing, J.S., et al. Acute health effects in a community after a release of hydrofluoric acid. Archives of Environmental Health. Vol. 46, no. 3 (May/June 1991). p. 155-160
(8) Gupta, B.N. Occupational diseases of teeth. Journal of the Society of Occupational Medicine. Vol. 40 (1990). p. 149-152
(9) Lund, K., et al. Exposure to hydrogen fluoride: an experimental study in humans of concentrations of fluoride in plasma, symptoms and lung function. Occupational and Environmental Medicine. Vol. 54, no. 1 (1997). p. 32-37
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Information on chemicals reviewed in the CHEMINFO database is drawn from a number of publicly available sources. A list of general references used to compile CHEMINFO records is available in the database Help.

Review/Preparation Date: 2002-09-27

Revision Indicators:
Physical Properties Comments 2002-12-09
Composition/purity 2002-12-09
WHMIS classification comments 2003-05-24
ERPG Comments 2003-06-10
Resistance of materials for PPE 2004-04-08
Short-term inhalation 2005-02-11
Short-term skin contact 2005-02-11
Short-term eye contact 2005-02-11
Long-term exposure 2005-02-11
First aid inhalation 2005-02-11
First aid skin 2005-02-11
First aid eye 2005-02-11
Note to physicians 2005-02-11
Toxicological info 2005-02-11
Bibliography 2005-02-11
TLV-TWA 2005-03-24
TLV definitions 2005-03-24
TLV basis 2005-03-25

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