Fluorosis is a crippling disease resulted from deposition of fluorides in the hard and soft tissues of body. It is a public health problem caused by excess intake of fluoride through drinking water/food products/industrial pollutants over a long period. Ingestion of excess fluoride, most commonly in drinking-water affects the teeth and bones.
It results in major health disorders like dental fluorosis, skeletal fluorosis and non-skeletal fluorosis. People exposed to large amounts of fluoride show dental effects much earlier than the skeletal effects. Dental fluorosis affects children and discolours and disfigures the teeth. Skeletal fluorosis affects the bones and major joints of the body like neck, back bone, shoulder, hip and knee joints resulting in to severe pain, rigidity or stiffness in joints. Severe forms of skeletal fluorosis results in marked disability. Non-skeletal forms of fluorosis are earlier manifestations, which develop long before the onset of typical changes in teeth and skeletal bones these are seen as gastro-intestinal symptoms and may overlap with other diseases leading to misdiagnosis. It affects men, women and children of all age groups.
Fluorosis is worldwide in distribution and endemic at least in 25 countries. It has been reported from fluoride belts: one that stretches from Syria through Jordan, Egypt, Libya, Algeria, Sudan and Kenya, and another that stretches from Turkey through Iraq, Iran, Afghanistan, India, northern Thailand and China. There are similar belts in the Americas and Japan.
It is not necessary that all symptoms are present at the same time. The severity and duration, (which is often episodic), depend on a person’s age, nutritional status, environment, kidney function, amount of fluoride ingested, genetic background, tendency to allergies, and other factors such as hardness of the water due to presence of calcium and magnesium.
Various symptoms are:
- Dental fluorosis: Clinical dental fluorosis is evident by staining and pitting of the teeth. In more severe cases all the enamel may be damaged (however, fluoride may not be the only cause of dental enamel defects; enamel opacities similar to dental fluorosis are associated with other conditions, such as vitamins A and D deficiency or a low protein-energy diet). Ingestion of fluoride after six years of age will not cause dental fluorosis. The teeth could be chalky white and may have white, yellow, brown or black spots or streaks on the enamel surface. Discolouration is away from the gums and bilaterally symmetrical.
- Skeletal fluorosis: The early symptoms of skeletal fluorosis, include stiffness and pain in the joints. In severe cases, the bone structure may change and ligaments may calcify, with resulting impairment of muscles and pain. Constriction of vertebral canal and intervertebral foramen exerts pressure on nerves, blood vessels leading to paralysis and pain.
Non skeletal fluorosis/ Effects of fluorosis on soft tissues /systems:
- Gastrointestinal symptoms: Abdominal pain, excessive saliva, nausea and vomiting are seen after acute high-level exposure to fluoride.
- Neurological manifestation: Nervousness and depression, tingling sensation in fingers and toes, excessive thirst and tendency to urinate
- Muscular manifestations: Muscle weakness & stiffness, pain in the muscle and loss of muscle power, inability to carry out normal routine activities.
- Allergic manifestation: Skin rashes, Perivascular inflammation: pinkish red or bluish red spot, round or oval shape on the skin that fade and clear up within 7-10 days.
- Effects on foetus: Fluoride can also damage a foetus, if the mother consumes water/food with high concentrations of fluoride during pregnancy/breast feeding. Abortions, still births and children with birth defects are common in endemic areas.
- Low haemoglobin levels: Fluoride accumulates on the erythrocyte (red blood cells) membrane, which in turn looses calcium content. The membrane which is deficient in calcium content is pliable and is thrown into folds. The shape of erythrocytes is changed. Such RBCs are called echinocytes, and found in circulation. The echinocytes undergo phagocytosis (eaten-up by macrophages) and are eliminated from circulation. This would lead to low haemoglobin levels in patients chronically ill due to fluoride toxicity.
- Urinary tract manifestations Urine may be much less in volume; yellow-red in colour and itching in the region may occur.
- Ligaments and blood vessel calcification: A unique feature of the disease is soft tissues like ligaments, blood vessels tend to harden and calcify and the blood vessels may be blocked.
Most of these manifestations are, no doubt, nonspecific, but their occurrence in subjects living in fluorosis-endemic areas should alert suspicion. These early warning signs have been extremely helpful in early detection of large numbers of cases in rural areas; prompt intervention programmes (i.e. providing safe drinking water) in these cases have provided considerable relief within a short span of time
Fluorosis is caused by excessive intake of fluorides from multiple sources such as in food, water, air (due to gaseous industrial waste), and excessive use of toothpaste. However, drinking water is the most significant source.
Moderate-level chronic exposure (above 1.5 mg/litre of water – the WHO guideline value for fluoride in water) is more common. Acute high-level exposure to fluoride is rare and usually due to accidental contamination of drinking-water or due to fires or explosions.
Fluoride in water is mostly of geological origin. Water with high levels of fluoride content are mostly found at the foot of high mountains and in areas where geological deposits are collected in sea.
Other risk factors–
- Several of the ready to serve foods, beverages, snacks have high content of black rock salt (CaF2) or ‘kala namak’ (which has 157ppm fluoride) and red rock salts.
- Tobacco or supari (aracanut) when they are chewed.
- Intake of certain drugs such as fluoroquinolone antibiotics, few anti-depressants, some anti-fungal drugs, cholesterol-lowering drugs, steroids and anti-inflammatory drugs, arthritis drugs, antacids, drugs for osteoporosis and otosclerosis. and numerous other drugs that contain fluoride can contribute to fluoride toxicity over time.
- Person with calcium deficiency or malnourished individuals appear to be more prone to develop dental and skeletal fluorosis.
- Fluoridated toothpastes: Indian studies have also shown that absorption of fluoride takes place within minutes after brushing the teeth with fluoridated toothpaste; the saliva from the oral cavity when analyzed for fluoride has also revealed high fluoride content.
- Fluoridated beverages.
- Fluoride-rich foods such as tea, ocean fish, gelatin, skin of chicken, fluoridated salt, food contaminated with post-harvest fumigants (e.g. sulfuryl fluoride) and pesticides (e.g. sodium aluminium fluoride, Na3AlF6, which may be used on grapes).
- Fluoride from any other environmental sources, including cigarette smoke and industrial pollution, e.g. fluoride in dust and fumes from industries such as those manufacturing steel, aluminum, enamel, pottery, glass, bricks, phosphate fertilizer, and others involved with power, welding, water fluoridation plants, refrigeration, rust removal, oil refining, plastics, pharmaceuticals, tooth-paste, chemicals, and automobiles.
- Diets rich in fat have been reported to increase deposition of fluoride in bones.
- It is also known that fluorosis, in its severe forms, is mostly restricted to a particular climate zone in the world — the areas with semi-arid tropical conditions. In these areas, the consumption of drinking water is high and the population is more vulnerable to the disease as compared to their counterparts in colder areas with low consumption of water, though the fluoride content of water in both the areas may be the same.
- Dental fluorosis can only occur if the fluoride exposure is during the first years of life while the teeth are forming.
- In China, fluoride toxicity occurs with: brick tea and food contaminated with fluoride during drying of chilies and corn with coal briquettes.
Mechanism after fluoride intake: Once fluoride enters the body either through the blood vessels in the mouth or through the gastrointestinal route, it reaches the various organs and tissues in the body. Fluoride (F) being an electronegative element, having a negative charge is attracted by positively charged ions like calcium (Ca++). Bone and tooth having highest amount of calcium in the body, attract the maximum amount of fluoride and is deposited as calcium fluorapatite crystals. At the same time, from certain areas in the bone and tooth, the unbound calcium is lost.
All the substances containing fluoride should be avoided during diagnosis. If the symptoms are caused by fluoride, they should diminish markedly within a week and largely disappear within several weeks. Gastrointestinal symptoms settle within 15 days.
(l) Physical tests for detection of skeletal fluorosis in endemic areas-
(a)The subject is asked to lift a coin from the floor without bending the knee. A person with skeletal fluorosis would not be able to lift the coin without flexing the large joints of lower extremity (unable to bend without bending knee, test is present in other disease also).
(b) Chin Test: The subject is asked to touch the anterior wall of the chest with the chin. If there is pain or stiffness in the neck, he/she is unable to bend the neck-touching the chest with chin is not possible.
(c) Stretch Test: The individual is made to stretch the arm sideways, fold at elbow and touch the back of the head. When there is pain and stiffness, it would not be possible to touch the back of the head.
(ll)Radiographs: X-ray would reveal increased girth, thickening and density of bone, ligaments calcified. Maximum ill effects of fluoride are detected in the neck, spine, knee, pelvic and shoulder joints. It also affects small joints of the hands and feet.
(lll)SA/GAG test (Sialic acid / Glycosaminoglycan test) -The SA/GAG test is for early detection/diagnosIs of fluoride toxicity. The value of SA/GAG will be reduced in fluorosis and will be significantly elevated in ankylosing spondylitis. The SA/GAG value shows no significant change in arthritis, osteoporosis and spondylosis.
(lV)Estimation of Fluoride content in:
- Drinking water– 1.0 ppm (parts per million) is considered as the permissible upper limit for fluoride content in drinking water.
- Blood (serum): The serum fluoride levels may or may not be informative as fluoride in circulation never maintains a steady state; it is diverted to other tissues; absorbed by tissues and excreted.
- Urine (24 hrs collection if possible): The urinary fluoride level is more useful compared to the blood fluoride level. If the subject has been ingesting food, water, drugs or any other substance contaminated with fluoride, urinary fluoride is bound to be high. (There is another possibility that , when an individual moves out of an endemic area and start living in a non-endemic area, there is a tendency for excreting high levels of fluoride for short duration of time (viz 1-2 months) and the subject will also have less pain in the joints and other regions. History taking is an important task in the diagnosis).
(V)Haemoglobin estimation: for detection of anaemia.
There is no treatment for severe cases of skeletal fluorosis, only efforts can be made towards reducing the disability which has occurred. However, the disease is easily preventable if diagnosed early and steps are taken to prevent intake of excess fluoride through provision of safe drinking water, promote nutrition and avoid foods with high fluoride content. Dental and skeletal fluorosis is irreversible and no treatment exists, the only remedy is prevention by keeping fluoride intake with in safe limits.
Dental fluorosis treatment:
- tooth whitening for mild fluorosis cases
- composit bonding
- Porcelain veneers
Fluorosis can be prevented by avoiding excessive intake of fluoride by individuals / community. Excessive fluoride intake and its adverse effects can be minimized or prevented by adapting following measures:
- by using alternative water sources,
- by removing excessive fluoride from drinking water,
- by improving the nutritional status of population/individuals at risk.
(a) Using alternative water resources include surface water, rainwater, and low fluoride ground water:
- Surface water: If surface water is used for drinking purposes particular caution is required, since it is often contaminated with biological and chemical pollutants. Surface water should be used after proper disinfection with simple and low cost method such as sand filtration, ultraviolate disinfection; chlorination (may be adequate in some places but not all places.)
- Rainwater: It is usually cleaner and low cost simple source, but problem is for large storage of water and large reservoir in the communities and households.
- Low fluoride ground water– fluoride content can vary in wells in the same area, depending on the geological structure of the aquifer and the depth at which water is drawn. Deepening tube wells and digging new wells in another site may be helpful. Fluoride is unevenly distributed in ground water both vertically and horizontally.
(b)Defluoridation of water (removing excessive fluoride from drinking water):
Use of safe drinking water with safe fluoride levels is the preferred option for the prevention of fluorosis; however access to safe water in fluorosis endemic areas is limited.
The de-fluoridation is the only solution; this can be done by different methods:
(i) Chemical precipitation-Alum coagulation (Nalgonda technique), Electrolyte defluoridation
- Alum coagulation/Flocculation: Raw water is mixed with aluminum sulphate (alum: hydrate aluminum salt)), lime or sodium carbonate (1/20th of alum, as process is best carried out under alkaline conditions) and bleaching powder (3 mg/l, is added to disinfect the water).Technique is suitable for community and house hold levels. At household level a bucket of water (20 liters) is mixed with alum, lime and bleaching ( doses of alum and lime are determined after assessing the fluoride content and alkalinity of water) and left for coagulation and settling of the flocks at the bottom of bucket for at least one hour. The treated water is withdrawn through a tap 5 cm above the bottom of the bucket, safely above the sludge level. Store the water for the drinking purposes in another bucket and discard the sludge.
- Electrolyte defluoridation: In this process when direct current is passed through the aluminum electrodes in water (containing excessive fluoride), active species of hydroxide of aluminum are produced; which adsorb the fluoride ions present in the water resulting in the formation of the sludge and treated water (which is used for drinking)
(ii)Adsorption: This approach is to filter water down through a column packed with a strong adsorbent such as activated alumina (AL2O3), activated charcoal, or ion exchange resins. This method is also suitable for both community and household levels. Once adsorbent become saturated with fluoride ions filter is backwashed with a mild acid or alkali solution, as the backwashing material is rich in fluoride, it should be disposed off carefully so that not re contaminating nearby ground water.
All methods produce sludge with very high concentration of fluoride (that has to be disposed of); therefore only water for drinking and cooking purposes should be treated, particularly in the developing countries.
(iii) Ionic separation–
- Reverse Osmosis Filtration
(c) Better nutrition: measures to improve nutritional status (intake of calcium and vitamin C, iron,antioxidants) of affected population particulary children are an effective supplement to technical solutions mentioned above. Mothers in affected areas should be encouraged to breastfeed since breast milk is usually low in fluoride.
Following procedures do not remove fluoride:
- Boiling water: will concentrate fluoride content rather than removing it.
- Freezing water: does not affect concentration of fluoride.
- Activated carbon: filters do not remove fluorides.
- Sensitizing the community with information on fluorosis, importance of drinking safe water and about healthy diet are important for prevention and control of fluorosis.
- Water contaminated with fluoride more than 1ppm should not be consumed.
- High fluoride containing products viz., Supari, tobacco, black rock salt, red rock salt (Sindhi), Drugs and cosmetics like toothpaste, mouth rinses and any other products proven to have high fluoride should be avoided.
- Intake of foods (rich in calcium, iron, vitamin c, other antioxidants), such as milk, curd, green leafy vegetables, fruits should be advocated.
Human Resource Development: to develop adequate human resource both in Health and Public Health Engineering Sectors. Special focus is laid on updating the information for medical personnel/doctors to recognize the disease. In a similar manner, the focus for public health engineering department/ integrated child development services and other departments is to practice early detection of endemic areas and proper water management.