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Chapter: Modern Medical Toxicology: Chemical Poisons: Non-Metallic Chemical Poisons

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Fluorine - Chemical Poisons

Fluorine is a diatomic halogen gas. It is a very corrosive and toxic gas, and is found in the soil in combination with calcium.

Fluorine

Physical Appearance

·     Fluorine is a diatomic halogen gas. It is a very corrosive and toxic gas, and is found in the soil in combination with calcium. It is released into the atmosphere by the burning of soft coal, and during manufacturing processes involving superphosphate, aluminium, steel, lead, copper, etc.

·     Salts (referred to as fluorides) include sodium fluoride and sodium fluoroacetate. Both are crystalline, white, odourless, tasteless, and strongly alkaline.

Uses

Sodium fluoride and sodium fluoroacetate are widely used as cockroach and rat killers.

In dentistry, fluorides are used in toothpastes, topical gels, and mouthwashes.

Usual Fatal Dose

·              70 to 140 mg/kg of fluoride ion. In general, 2.2 sodium fluoride contains 1 mg of fluoride ion.

·              Fatal blood fluoride level: more than 0.2 mg/100 ml.

·              Urinary fluorine output of less than 5 mg/L is used as an index of safe working level for long-term exposure.

·              The safe upper limit for fluorine gas is 1 ppm.

Mode of Action

·              Fluorine and fluorides act as direct cellular poisons by inter-fering with calcium metabolism and enzyme mechanisms. Fluoride combines with hydrochloric acid in the stomach to form hydrofluoric acid which is a powerful corrosive. After absorption, fluoride ions combine with cations in the serum, particulaly calcium and magnesium leading to hypocalcaemia and hypomagnesaemia. Hyperkalaemia is often an added hazard.

·              Dermal cutaneous burns are caused by the violent reaction between the skin and fluorine producing a thermal burn.

Clinical Features

Acute Poisoning—

·              Fluorine is an extremely strong tissue irritant, causing caustic irritation of eyes, skin, and mucous membranes. Thermal burns or frostbite may occur.

·              Inhalation of fluorine gas leads to headache, respiratory distress, polydipsia, and polyuria.

o     Ingestion of fluorides in large amounts can cause the following manifestations:

o     Metallic taste, salivation, vomiting, diarrhoea, abdominal pain.

o     Paraesthesias, paresis, tetany, convulsions.

o     Ventricular arrhythmias, cardiovascular collapse, coagulopathies.

Chronic Poisoning—

·              Leads to a condition called fluorosis:

o     This is usually the result of high fluoride content in water supply. Fluoridation of water is done to prevent caries. When the water fluoride content is more than 3 to 5 ppm, chronic exposure leads to mottling of teeth (Fig 8.8). The enamel loses its lustre and becomes rough, pigmented, and pitted.


o     Skeletal fluorosis is a different entity which is also associated with high fluoride concentration in water and soil. In non-endemic areas it may occur as a result of occupational exposure (aluminium production, magnesium foundries, superphosphate manufacture, etc.) . The effects are usually more severe in children.

Main features include genu valgus or varum (bow legs or knock knees) (Fig 8.9), lateral bowing of femora, sabre shins, and deformities of thorax, vertebrae, pelvis, and joints. There may also be mottling of teeth.


In adults there may be thickening of long bones, development of exostoses and osteophytes, calcification of ligaments and tendons, polyar-thralgia, and contractures of hips and knees.

Treatment

Acute Poisoning—

a.Insecticide fluoride ingestion—

·              Stomach wash with magnesium sulfate, followed by activated charcoal and sorbitol.

·              Treat convulsions with anticonvulsants.

·              Supportive measures, including the use of haemo-dialysis.

b.Non-insecticide fluoride ingestion –

Mild:

·              Administer milk.

·              Watch the progress for at least 12 hours. If symptoms such as vomiting, diarrhoea or abdominal pain occur, treat as mentioned below.

Moderate to Severe:

·              Stomach wash (if vomiting has not occurred). -- Administer milk, oral calcium salts, or aluminium (or magnesium) based antacids to bind fluoride.

·              Treat hypocalcaemia, hypomagnesaemia, and hyper/hypokalaemia.

·              Consider haemodialysis for severe poisoning.

c.Frostbite—

Rewarming:

·              Place affected area in a water bath with a temperature of 40 to 420C for 15 to 30 minutes until thawing is complete. The bath should be large enough to permit complete immersion of the injured part, avoiding contact with the sides of the bath.

·              Correct systemic hypothermia.

·              Rewarming may be associated with increasing pain, requiring narcotic analgesics.

Wound Care:

·              Digits should be separated by sterile absorbent cotton; no constrictive dressings should be used. Protective dressings should be changed twice per day.

·              The injured extremities should be elevated and should not be allowed to bear weight.

·              Prophylactic antibiotics may be administered. -- Clear blisters should be debrided but haemor- rhagic blisters left intact.

·              Further surgical debridement should be delayed until mummification demarcation has occurred (60 to 90 days). Spontaneous amputation may occur.

·              Tetanus prophylaxis is advisable.

·              Topical aloe vera may decrease tissue destruc-tion and can be applied every 6 hours.

·              Ibuprofen is a thromboxane inhibitor and may help reduce tissue loss. Adult dose of 200 milli-grams every 12 hours is recommended.

Forensic Issues

Most cases of poisoning (acute or chronic) are accidental. Suicidal poisonings have been reported with fluoride-based rodenticides and cockroach killers.

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