Fluoride Pollution

Dr. Md. Khalequzzaman, PhD

Associate Professor
Department of Public Health and Informatics
Bangabandhu Sheikh Mujib Medical University, Dhaka
romenraihan@yahoo.com
 Fluoride
• Fluoride is the 13th most abundant naturally occurring element in the earths
crust.
• This has been found by Henri Moissan in 1886.
• The concentration of Fluoride in water is directly proportional to the degree of
fluorosis.
• Enamel mottling is widespread in area with water having Fluoride content of 3
ppm.
• The highest Fluoride concentration ever found in natural water was 2800 mg/L,
recorded in lake Nakuru in the Rift Valley in Kenya.
 Fluoride
1970
Fluoride was found to be present in rock phosphate deposits.

20th Century
It was used by the biochemists as a tool to help them to determine the
biochemical pathways.

1848, Stockhardt & Schroder

Published the first detailed description of fluoride injury in plants.
 Properties of Fluorine
• Not present in free element state
• Most reactive
• Most electronegative
• Fluorine can form both covalent and electrovalent bonds
• Fluorine forms very strong bonds with carbon
• They are resistant to biological and chemical attack
 Sources of Flouride in Atmosphere
• Natural sources

• Anthropogenic
sources
 Use of Fluoride
Hydrogen fluoride is used
• In aluminium production
• In Chlorofluorocarbon (CFCs) production
• In the production of aluminium fluoride, sodium fluoride and other fluoride salts.
• Petroleum, chemical, and plastics industries.
• To clean metals, bricks, or remove sand from metal castings.
• To enamel, polish glass and galvanize iron.
 Point Sources of Fluoride
The primary sources of fluoride emissions are the industries that
• Manufacture it or use it in production
• Aluminium industry,
• Oil drilling and refining
• Chemical and plastics industries
• Agricultural and pesticide chemical manufacturers
• Dye manufacturers,
• Manufacturers of metal parts.

Consumer Products
• Toothpaste, pesticides, ceramic and glass polishing and frosting materials, special dyes,
• Drinking water in some areas may be naturally or artificially enriched in fluoride.
 Fluoride Cycle
• When fluoride is emitted to the air as a gas or
particulate it may be carried by the wind and
deposited on surrounding vegetation and soil.
• The gas dissolves in clouds, fog, rain, or snow.
This impacts the environment as wet acid
deposition ('acid rain’).
• In the environment it will react with other
chemicals present (ammonia, magnesium,
calcium) to form salts, neutralizing the acid.
• Industrial emissions of fluoride compounds can produce elevated concentrations in the atmosphere.
• Hydrogen fluoride will exist as a particle, which may dissolve in clouds, fog, rain, dew, or snow.
• In clouds and moist air, it will travel along the air currents until it is deposited as wet acid deposition
(acid rain, acid fog, etc).
• In waterways it rapidly mixes with the water.
 Fluoride in water
• Dissolve in water and split into ions
• Speed of dissolution depend on pH, type of compound
• Transport and transmission in influenced by pH, hardness and
presence of clay
• As they travel through the water cycle, fluoride usually combine with
Aluminium.
 Fluoride in Soil
• Fluoride is so strongly absorbed by the soil that the leaching is slow.
• The most widespread source of soil contamination arise from the use
of phosphate fertilizers.
• In soils, fluoride is predominantly combined with Aluminium or
calcium.
• When the soil is slightly acidic, fluoride tends to adsorb more strongly
to soil particles.
 Fluoride in Plants
Gaseous fluoride
• Absorbed through leaf stomata
• Move by transpiration into the principal
sites of accumulation at the tip and leaf
margins

Dissolved in water
• In plant roots through passive diffusion
• Transported to the shoots via xylem
 Fluoride Pollution
• Hydrogen fluoride dissolves in water to make hydrofluoric acid.
• Hydrogen fluoride will corrode most substances except lead, wax, polyethylene,
and platinum.
• Hydrogen fluoride is used to manufacture other fluorine-based chemicals
including Sodium fluoride, which is a white powder, although sometimes it is dyed
blue for identification purposes.
 Effects of Fluoride Pollution
• Low levels of fluoride in drinking water
(0.5 to 1 mg/l) protect against dental
caries
• High levels of fluoride in drinking water
(above 1.5 mg/l) will lead to adverse Skeletal Fluorosis

health impacts ranging from dental

fluorosis to skeletal fluorosis
• Fluoride levels in water beyond desirable /
permissible limits is typically found in
groundwater and not surface water.

Dental Fluorosis
 Water Fluoridation
• Water fluoridation is the process of adding fluoride to the water supply so the
level reaches approximately 0.7 ppm, or 0.7 milligrams of fluoride per liter of water
this is the optimal level for preventing tooth decay.
• Fluoridation is a safe, effective, and economical process endorsed by the
American Dental Association, the American Water Works Association, and public
health groups worldwide.
• Small amounts of fluoride are present naturally in all water sources.
• Water fluoridation is the precise adjustment of the natural fluoride concentration
in a public water supply up to the level recommended for preventing tooth decay.
 Defluoridation
• The process of water treatment that reduce the concentration of fluoride in the
water, in order to make it safe for human consumption is DEFLUORIDATION.

BASIC REQUIREMENTS
• Modest investment
• Low maintenance cost
• Simple design
• Operable by villagers
• Able to reduce fluoride content, e.g. from 5 to 0.5 mg/L
Thank you