Fluoride Tablet Toxicity - Types, Symptoms, and Treatment

Introduction

Fluoride can be found naturally in soil, water, plants, and animals. It is the 13th most abundant element found in the Earth’s crust and belongs to the halogen group of elements. It is the omnipresent and most reactive element present in nature. It is present in minute amounts in the human body's tissues, such as bone, enamel, and dentin. The beneficial effects of fluoride include reducing the prevalence of tooth decay and resulting in stronger bones and teeth.

However, ingesting fluoride exceeding the recommended limit can cause toxicity and adverse effects. Acute cases of fluoride toxicity most commonly result from the ingestion (intentional or accidental) of fluoride-containing products. Also, some parts of the world (for example, regions of India and China) have increased levels of fluoride in groundwater, which can result in chronic fluoride toxicity called fluorosis. This article discusses the mechanism of fluoride absorption, symptoms, adverse effects, and treatment of fluoride toxicity.

What Is Fluoride Toxicity?

Fluoride toxicity is a condition that results due to increased levels of fluoride in the body. At low concentrations, fluoride is considered safe for dental health. However, large amounts of soluble fluoride salts lead to harmful effects on the body.

Fluoride is commonly found in many household products, such as:

• Toothpaste.

• Dietary supplements (sodium fluoride).

• Vitamins.

• Insecticides and rodenticides (sodium fluoroacetate).

• Chrome-cleaning and glass-etching agents (ammonium bifluoride).

The recommended fluoride levels by WHO (World Health Organization) for dental health is 0.5 to 1 mg/L (milligrams per liter). Fluorosis (white or brown spots on the tooth enamel) is possible above this recommended dosage. Overall, the least amount of fluoride that can be dangerous for humans is estimated to be 5 mg/kg, which means 5 milligrams of fluoride for each kilogram of body weight. In medical terms, this dose is called a ‘probable toxic dose’ (PTD). This dose is sufficient to cause serious poisoning, and it can be life-threatening when medical treatment is unavailable.

What Are the Types of Fluoride Toxicity?

Fluoride toxicity can be divided into two types:

1. Acute Fluoride Toxicity - This type of fluoride toxicity occurs occasionally, but it can be fatal. It generally occurs due to accidental ingestion of fluoride salts or fluoride solutions such as sodium fluoride.
2. Chronic Fluoride Toxicity - This type of fluoride toxicity is more common than acute fluoride toxicity. One of the causes of chronic fluoride toxicity is the presence of high levels of fluoride in drinking water (groundwater) in some regions of countries like India and China. The adverse effects of this type depend mainly on the duration and dose of fluoride.

How Does the Human Body Absorb Fluoride?

Fluoride is commonly consumed through the mouth and absorbed through the digestive (gastrointestinal) tract. Other routes of fluoride absorption, such as dermal absorption and inhalation, are less common. The fluoride absorption starts in the stomach and upper region of the small intestine. Fluoride absorption depends on several factors, such as stomach pH, presence of food in the stomach, chemical formula of consumed fluoride, interaction with other food ingredients present in the digestive tract, and calcium, aluminum, and magnesium compounds. The absorbed fluoride is distributed in the intracellular and extracellular fluids through the circulation and is retained in the mineralized tissues of the body. The fluoride retained in mineralized tissues is reversible, which means the fluoride is slowly released back when the fluoride levels in plasma fall. Fluoride in the plasma can cross the placenta and is found in fetal and placental tissues. The fluoride that is not absorbed by the body is passed out of the body through feces.

Possible mechanisms of fluoride toxicity include:

• As fluoride is one of the most reactive elements, it attacks oxygen when present in toxic amounts in the body and disrupts the metabolism leading to the production of hydrogen peroxide as a product.

• Calcium forms a chemical complex with fluoride resulting in hypocalcemia (low levels of calcium in the body) and leading to inhibition of nerve impulses or nerve function.

• When fluoride comes in contact with moisture, it forms hydrofluoric acid, and this acid results in the burning of tissue because of low pH.

• Hypocalcemia and hyperkalemia (low levels of potassium in the body) lead to electrolyte imbalance and eventually result in problems in cardiac rhythm.

What Are the Symptoms of Fluoride Toxicity?

• Abnormal taste (soapy or salty taste).

• Watery and loose stools (diarrhea).

• Pain in the abdomen.

• Saliva flowing outside the mouth (drooling).

• Headache.

• Fatigue (weakness).

• Involuntary shaking of the body (tremors).

• Abnormal levels of potassium and calcium in the blood.

• Slow or irregular heartbeat (arrhythmia).

• Sudden cardiac arrest in severe cases.

What Are the Toxic Effects of Fluoride?

Fluoride toxicity can be divided into acute and chronic toxicity depending on the adverse effects on the body.

Acute Effects

• Nausea and vomiting.

• Hypocalcemia.

• Hypotension (low blood pressure).

• Hypersalivation (excessive salivation).

• Tetany (involuntary muscle spasm) of hands and feet.

• Mixed respiratory and metabolic Acidosis owing to renal or respiratory failure.

• Bronchospasm (muscle tightening of the airways).

• Convulsions and coma leading to death.

Chronic Effects

• Dental fluorosis.

• Skeletal fluorosis (increased bone density and mass due to excess fluoride).

• Dyspepsia and gastric irritation.

• Hypersensitivity reactions.

• Insufficiency of the renal system (increased serum creatinine and urea nitrogen).

• Muscular spasms and numbness.

• Birth defects (excess fluoride leads to neurological damage and reduced secretion of neurotransmitters) and cancer.

How to Treat Fluoride Toxicity?

The healthcare provider will suggest a few tests to assess the toxicity level. These tests include blood and urine tests, chest X-rays, and electrocardiogram (ECG) or heart tracing. After the reports of the tests are analyzed, the treatment plan is prepared.

The treatment options include:

• Intravenous (IV) fluids.

• Medications to relieve symptoms.

• Laxatives and induced vomiting.

• Oral administration of soluble milk or calcium to relieve gastrointestinal symptoms.

• Breathing support (such as a ventilator).

Conclusion

The beneficial role of fluoride in maintaining good oral health has been known for decades. However, people should also be aware of the harmful effects of excess consumption of fluoride. Fluoride can be dangerous when taken in excess and can be life-threatening. It has been found that fluoride toxicity can adversly affect the bones, teeth, brain, kidneys, and the thyroid. Immediate medical treatment should be provided for serious cases of fluoride toxicity. In areas with groundwater with high fluoride levels, alternate dental products with low fluoride levels should be given and monitored.