Hf overview

Education on HF

1. HF Overview By Dr. Ashok Laddha Occupational health physician

2. Content General Information Utilization of AHF and HF in industry Classification Physico – Chemical Properties General Hazards Physiopathology & Toxicology Treatment of injuries Decontamination First Aid Medical treatment

3. Background The history of hydrofluoric acid is linked to the history of fluorine because hydrogen fluoride was synthesized for the first time by C.W. Scheele from fluoride and concentrated acid, while trying to isolate the fluorine atom. On the industrial level, hydrofluoric acid results from the following reaction between calcium fluoride (molecular formula CaF2) and concentrated sulfuric acid, at 250 °C CaF2 +H2SO4=2HF + CaSO4

4. Synonyms Hydrogen fluoride (gaseous state) Anhydrous hydrofluoric acid (other name of the gaseous state) Hydrofluoric acid (name of aqueous solutions) Fluorhydric acid Fluoric acid HF (using the molecular formula to name the substance)

5. Why HF is weak acid? Bond between Flourine and Hydrogen is very strong because of very high electro negativity difference. That is why Flourine doesn't let Hydrogen go easily. So extent of donating H+ in is low in  HF  that is why it is considered  weak acid . It is classified as  weak  based upon its dissociation when in solution with water.

6. Most corrosive acid in world HF-SbF 5  is extremely corrosive, toxic, and moisture sensitive. Like most strong acids,  fluoroantimonic  acid can react violently with water, owing to the exothermic hydration.

7. INTRODUCTION Hydrofluoric acid (HF) is an inorganic acid commonly used in many domestic and industrial settings. HF was first used for etching glass due to its corrosive properties, but currently is also widely used in cleaning agents, rust removers, in the semiconductor industry, and for manufacturing fertilizer, pesticides and some plastics. Technically, HF is a weak acid when compared with other hydrogen halide acids, meaning the molecule does not strongly dissociate into hydrogen and fluorine ions when dissolved in water. In fact, after being dissolved in water, HF becomes much less dangerous and less acidic at low concentration (≤20%) . However, at high concentrations (>20%), small quantities of HF can cause life-threatening burns, and if the diagnosis is missed or the treatment delayed, the consequences may be devastating for the patient.

8. Utilization of AHF/HF Industry Uses Petrochemical As catalytic agent when alkylising petrol Glass Glass etching Medicine Propellant for medication, anaesthetic gases, production of antibiotics, production and coating of surgical prostheses, production of medicines Agrochemical Pesticides Metallurgy Metal cleaning/ aluminium production electronics Production of microchips, cleaning agents for electronic circuits Cleaning Agent Rust removers, outer wall cleaners Nuclear Processing of uranium ore coolants AC, Refrigerators Fluoro -chemistry Production of Fluoride salts, and Fluoro plastics Extinguishing Agent Fire extinguishers

9. Effect of Concentration Low concentration solutions (8-15%) cause little or no pain on exposure, but can cause delayed onset of severe pain and after 12-24 hours can develop signs of tissue corrosion. Intermediate concentration solutions (20-40%) cause pain after exposure and may cause deep tissue injury. High concentration solutions (50-70%) produce pain immediately after contact and result in severe tissue injury and systemic effects. The Occupational Safety and Health Administration HF workplace permissible exposure limit is 3 ppm in air, while 30 ppm concentrations are considered dangerous to life and health.

10. Classification Concentration Toxicity AHF + HF >85% ACUTE TOXICITY (oral, dermal and inhalation) Cat. 1 and 2 SKIN CORROSION Cat 1 HF <60% AND >85% ACUTE TOXICITY (oral, dermal and inhalation) Cat 1 and 2 SKIN CORROSION Cat 1A HF <60% HYDROFLUORIC ACID with not more than 60% of hydrogen fluoride Fatal if swallowed : Fatal in contact with skin Fatal if inhaled Causes severe skin burns and eye damage

11. Physical Properties Hydrogen fluoride is a colorless gas with a density of 1.15 g/L at room temperature, or a colorless liquid (below 20°C) with a density of 0.99 g/ mL. Hydrofluoric acid (solution of HF in water), is a colorless solution. Its exact physical properties (boiling point, melting point and density) depend on the concentration of HF in the aqueous solution.

12. Chemical Properties Hydrofluoric acid is a very strong, reactive and corrosive acid. It readily reacts with bases, acids, and oxidants. One of its best known reactions is its corrosive, dissolving effect on glass and ceramics (called etching). Due to reactivity towards glass and metals, it is typically stored in plastic containers.

13. Hazardous Reactions-1 Risk of explosion in contact with: cyanogen fluoride (polymerization) methanesulfonic acid -> oxygen difluoride release nitric acid + glycerol Risk of explosion in contact of hydrofluoric acid with: potassium permanganate metals potassium sodium   The substance can react dangerously with: ammonia organic substances sulfuric acid acetic anhydride; aminoethanol ; ammonium hydroxide; dry paper; silicon compounds; vinyl acetate

14. Hazardous Reaction-2 Anhydrous hydrogen fluoride may react dangerously with: arsenic(III)oxide; calcium oxide; metal oxides hydrofluoric acid may react dangerously with: metal silicides ; phosphorus pentoxide ; bismuth acid -> oxygen release fluorine sodium hydroxide Glass or quartz get etched.

15. Interesting Fact-1 There is no concentration of HF which can be relied upon as safe! There is no material that is completely resistant to HF degradation.

16. Interesting Facts-2 HF is extremely corrosive HF is extremely systemic toxic HF is highly reactive

17. Routes of Exposure Dermal Ingestion Inhalation Mucous Membrane Ocular

18. Target Organs-Toxicity Bone Teeth Skin Mucous Membrane Respiratory System Cardiovascular System GIT Neuromuscular

19. High Risk Group Computer chip manufacturing workers (etch stations and quartz tube cleaners and maintenance personnel) Oil field workers (e.g., "roustabouts"), and alkylation refinery workers Workers in the synthesis of fluorinated chemicals Laundry workers (only when involved with rust removers) Glass etchers Electroplaters Pesticide workers Agro workers

20. Bio Transformation Once absorbed into the blood, fluoride is rapidly distributed throughout the organs. Adult persons rapidly eliminate approximately 50% of the amount taken in. The excretion proceeds mainly within 24 hours with the urine and to a minor part via other pathways (with the feces, sweat, saliva and also mother’smilk ). The proportion which remains in the body long-term is almost exclusively (up to approximately 99%) deposited in the bones and teeth. During this, hydroxyl groups in the carbonate-apatite structure are replaced by fluoride ions. The accumulated fluoride can be at least partially remobilized and excreted. The half life for elimination from the bones was reported to be 8 – 20 years. Under prolonged steady exposure to fluoride, the fluoride contents in urine and plasma directly reflect the intensity of actual exposure. After occupational exposure ceases, the amount remaining in the body could be higher than what would be expected from the current level of exposure because of the slow mobilization of the part in the bones. [

21. Main Toxic Effects Acute: Corrosive action to the mucous membranes and skin, danger of serious damage of the eyes and lungs, disturbances to the metabolism, cardiovascular and nervous system Chronic: Irritation to the airways, eyes and skin; damage to the bones (skeletal sclerosis)

22. Mechanism of Action-2 primary mechanisms At concentrations >50%, HF acidity increases dramatically and it then behaves like a strong acid. The hydrogen ion causes a corrosive burn similar to other acid burns – this damage occurs immediately and results in visible tissue destruction. However, for low-concentration HF burns – which represent the large majority of HF burns – immediate corrosive destruction does not occur in any significant manner and there may be no immediate pain or tissue destruction. The second, more significant mechanism of tissue destruction is caused by fluoride ions. Liquefaction necrosis of deeper tissues is unique to HF because the acid is highly lipophilic and readily penetrates deep into tissue . The molecule then wreaks havoc as it releases its acidic hydrogen ion and fluoride ion in the presence of cations such as calcium and magnesium. This often-delayed reaction is responsible for the ‘pain out of proportion’ to physical examination findings, a result believed to be related to the local hyperkalemia effect secondary to calcium binding. Cell membrane permeability to potassium is increased by local calcium depletion; in addition, fluoride ions are believed to directly inhibit Na + K +  pumps. Both result in local hyperkalemia, neuronal depolarization and intense pain.

23. Mechanism of skin penetration 

24. Systemic Effect The systemic effects are primarily related to electrolyte disturbances – mainly hypocalcemia – but also hypomagnesemia , acidosis, fluorosis and hyperkalemia , which can lead to disturbances of renal, hepatic and cardiac function . Fluoride ions bind calcium and magnesium, and this process may occur at a rate exceeding the body’s ability to mobilize calcium and magnesium in the serum. In the majority of cases, clinical evidence of hypocalcemia is absent; therefore, high-risk patients must be evaluated by electrocardiography for prolonged QT interval and arrhythmias and placed on cardiac monitoring . In addition to causing hypocalcemia , fluoride ions are believed to be directly toxic to myocardial cells by inhibiting adenylate cyclase . For severe HF burns, serum electrolyte levels should be obtained urgently and then frequently monitored as dictated by the degree of clinical exposure and systemic involvement . .

25. Prolonged QT Interval

26. framework for risk of systemic toxicity HF burns with a high risk to develop lethal electrolyte imbalances 1% BSA burn with anhydrous HF 5% BSA burn with >70% concentrated HF 7% BSA burn with 50–70% concentrated HF 10% BSA burn with 20–50% concentrated HF 20% BSA burn with 5% Inhalation of HF at concentrations >5%

27. Symptoms of serious intoxications Symptoms of serious intoxications include: Hypocalcaemia (low calcium level in the blood) Hypotension (very low blood pressure), Tetany and/or laryngospasm (involuntary contraction of muscles either muscles or vocal cords) Respiratory failure (possibly due to pulmonary oedema ) Ventricular tachycardia (abnormal high pulse cardiac rate) => Ventricular fibrillation (heart quivers) => Cardiac arrest. Renal and hepatic functions may be impaired and muscular damage may be secondary to tetany Prolonged Q-T intervals in ECG/EKG as a result of hypocalcemia

28. Cutaneous Burn Management Apply 2.5% calcium gluconate gel to the affected area. If the proprietary gel is not available, constitute by dissolving 10% calcium gluconate solution in 3 times the volume of a water-soluble lubricant ( eg , KY gel). For burns to the fingers, retain gel in a latex glove. If pain persists for more than 30 minutes after application of calcium gluconate gel, further treatment is required. Subcutaneous infiltration of calcium gluconate is recommended at a dose of 0.5 mL of a 5% solution per square centimeter of surface burn extending 0.5 cm beyond the margin of involved tissue (10% calcium gluconate solution can be irritating to the tissue).

29. Inhalation Burn Patients with inhalation burns may develop acute lung injury presenting with the following: Hypoxemia Stridor Wheezing Rhonchi Ocular burns may present with severe pain.

30. Inhalation Burn Exposures to the head and neck should arouse suspicion of pulmonary involvement. If any doubt is present, admission for observation is advised. Specific treatment includes the following: Provide 100% oxygen by mask, 2.5% calcium gluconate by nebulizer with 100% oxygen, continuous pulse oximetry , ECG, and clinical monitoring. Acute lung injury is treated along conventional lines, as needed.

31. Ocular Burn Generously irrigate with sterile water or saline for at least 5 minutes. Local anesthetic may be required. If pain persists, irrigate with a 1% solution of calcium gluconate , which is made by diluting the 10% solution in 10 times the volume of normal saline. Do not use undiluted 10% calcium gluconate . Calcium salts are  very irritating  to the eye, and urgent ophthalmologic consultation should be requested prior to the irrigation with 1% calcium gluconate solution.

32. Complications-1 Severe burn with scaring Bone loss Electrolyte imbalance Renal Failure Hypotension Respiratory Failure Cardiac arrhythmia Ventricular Tachycardia Pulmonary edema .

33. Complication-2 Myocardial infraction Lingering chronic Lung Disease Eye exposure to hydrogen fluoride may cause prolonged or permanent visual defects, blindness, or total destruction of the eye. Swallowing hydrogen fluoride can damage the esophagus and stomach. The damage may progress for several weeks, resulting in gradual and lingering narrowing of the esophagus Skeletal Sclerosis

34. Warning Burns with concentrated HF are usually very serious, with the potential for significant complications due to fluoride toxicity. Concentrated HF, liquid or vapor, may cause severe burns, metabolic imbalances, pulmonary edema, and life threatening cardiac arrythmias . Even moderate exposures to concentrated HF may rapidly progress to fatality.

35. Pre -Hospital care-1 Treatment of hydrofluoric acid burns includes basic life support and appropriate decontamination, followed by neutralization of the acid by use of calcium gluconate or hydrofluoric-specific agent such as Hexafluorine , if available. If exposure occurs at an industrial site, obtain and transport any available treatment literature. Assess and manage acute life-threatening conditions in the usual manner. Emergency Medical Services (EMS) personnel should use gloves, masks, and gowns, if necessary. Remove soiled clothing. Initially decontaminate by irrigation with copious amounts of water. Ice packs on the affected area may alleviate symptoms by retarding diffusion of the ion.

36. Pre-Hospital care-2 If calcium gluconate gel or specific agent ( eg , Hexafluorine ) is available, apply liberally to the affected area. For digital burns, if calcium gluconate gel is not available, the fingers may be soaked in magnesium hydroxide–containing antacid preparations ( eg , Mylanta) en route to a medical facility. Retain gel/antacid in a latex glove if practicable, and the gloved hand may be immersed in iced water. Treat inhalation injuries with oxygen and 2.5% calcium gluconate nebulizer. Control pain with opioid agents

37. IMPORTANT GUIDE TO THE SUCCESS OF TREATMENT HF skin burns are usually accompanied by severe, throbbing pain that is thought to be due to irritation of nerve endings by increased levels of potassium ions entering the extracelluar space to compensate for the reduced levels of calcium ions, which have been bound to the fluoride. RELIEF OF PAIN IS AN IMPORTANT GUIDE TO THE SUCCESS OF TREATMENT

38. Important Safety Precaution FIRST AID RESPONDERS AND MEDICAL PERSONNEL MUST WEAR RUBBER (2 pairs of NEOPRENE OR POLYVINYL CHLORIDE [PVC]) GLOVES WHEN TREATING HF BURNS TO AVOID HAND BURNS!

39. Investigations Complete blood count Serum Calcium Serum Magnesium ECG PFT Renal function test Cardiac Markers Serum Electrolytes X-ray chest ABG Fluorides in urine Urine R/M Serum Fluoride level

40. Diagnosis Fluoride exposure can be confirmed by the determination of fluoride in the urine using a random spot urine collection. However, the determination of urinary fluoride is academic in patients with confirmed exposure. More important, determination of blood calcium is critical following significant exposure because absorbed fluoride may cause fatal hypocalcaemia.

41. Antidote 2.5% Calcium Gluconate Gel Calcium Gluconate Gel Diphorterine HF solution

42. Guidelines for calcium Replacement Guidelines advocate calcium replacement in high-risk groups even before the serum calcium level is determined . Proven hypocalcemia warrants calcium gluconate infusion parenterally and frequent serum calcium monitoring. Rapid urinary excretion and alkalization of urine have been described as effective means of fluoride ion removal. Hemodialysis has been reported to reduce both fluoride and potassium levels, and to treat persistent hypocalcemia despite calcium infusion. Some authors advise that if severe systemic toxicity develops despite intravenous calcium infusion and intensive care resuscitation, immediate surgical excision of the burn should be considered to remove the tissue source of the fluoride ions . This scenario is extremely rare and carries a poor prognosis. The use of urgent surgery in this setting is controversial because there are no controlled studies demonstrating any benefit over continued resuscitation.

43. Quaternary Ammonium Compounds Most HF burns can be satisfactorily treated by immersion of the burned part in an iced, aqueous solution of a quaternary ammonium compound. The most experience is with a solution of 0.13% benzalkonium chloride. The solutions should be cooled with ice cubes. Shaved or crushed ice may cause excessive cooling, with the danger of frostbite . Iced quaternary ammonium compound solutions offer several advantages over topical calcium gluconate gel:

44. Advantage Of QAC Ability to treat burns on multiple surfaces, such as the hand, more efficiently ; Reduction of local pain due to the cooling effect of ice; Possible slowing of the passage of the fluoride ion into deeper tissues and into the bloodstream due to local vasoconstriction ; Does not require continuous massaging Important Note:-Quaternary ammonium compounds should not be used for burns on the face, ears or other sensitive areas due to their irritating nature. It is preferable to use calcium gluconate gel or calcium gluconate injection in these areas.

45. Safe work Practice Anyone using HF must be trained in its use and a second person must be in attendance, aware of the use of HF and be prepared to assist in the event of an emergency. Training in the use of HF is provided by OHS. Tasks involving HF must be undertaken in a fume cupboard. Specimen storage areas must be marked as containing HF solutions. Solutions containing HF must be stored in polyethylene or Teflon containers. HF reacts with glass and, therefore, solutions containing HF are incompatible with glass storage vessels and equipment. Eyewash stations, emergency showers and hand washing facilities must be available in each work area. A first aid kit, which includes the HF module, must be available in each work area. Laboratory space and placement of equipment should not create a crowded working environment nor inhibit cleaning. All skin and eye contact must be avoided. Restriction of laboratory access is important. Waste containers for the safe disposal of acids must be provided.

46. TLV Irritation to nose and throat at 3 parts per million ( ppm ) Time-weighted average (TWA) of 0.5 ppm Short-term exposure limit (STEL) 15 min - 2 ppm 30 ppm is considered immediately dangerous to life and health (IDLH)

47. Exposure Limit The Permissible Exposure Limit (PEL) set by the U.S. Occupational Safety and Health Administration (OSHA) is a time weighted average exposure for 8 hours of 3 ppm . The American Conference of Governmental Industrial Hygienists (ACGIH) recommends a ceiling level of 2 ppm (1.53 mg/m³) with a 0.5 ppm TLV-TWA. The National Institute for Occupational Safety and Health (NIOSH) has established the level that is immediately dangerous to life and health (IDLH) at 30 ppm . The American Industrial Hygiene Association (AIHA) has published an Emergency Response Planning Guideline setting 50 ppm as the maximum level below which nearly all individuals could be exposed for one hour without experiencing or developing life-threatening health effects (ERPG-3), 20 ppm as the maximum level below which nearly all individuals could be exposed for one hour without

48. Caution Industrial experience indicates that prompt treatment, as described, will prevent the development of serious injury Therefore, speed is essential. Delays in decontamination, first aid care or medical treatment or improper medical treatment will likely result in greater damage or may, in some cases, result in a fatal outcome. Relief of pain is an important guide to the success of the treatment; therefore local anesthesia should be avoided

49. Take home message Be careful! ANY EXPOSURE OF AHF / HF MUST BE TREATED IMMEDIATELY AND SPECIFIC TO AHF/HF!