Fluoride as pollutant in air, water and its impacts on plants
FLUORIDE AS POLLUTANT IN
AIR, WATER AND SOIL AND
ITS IMPACTS ON PLANTS
Roll # B11-16
Course Title: Agriculture And Environmental Pollution
Module Code Bot- 437
History Of Fluoride Pollution
Pliny the Elder died due to fluoride
The study began much later in 16th
century, with the use of fluorspar
(CaF2) as flux in metal smelting.
He described how miners used rocks
called fluores to aid the smelting of
History Of Fluoride Pollution
• Fluorine was found to be
present in rock
• It was used by the
biochemists as a tool to
help them to determine
• Published the first
detailed description of
fluoride injury in plants.
Properties Of Fluorine
• Not present in free elemental 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 Fluoride in Atmosphere
•According to Fleischer (1953), fluoride accounts for
0.032% of the earth crust
•Major minerals are Fluorite (CaF2), Fluorapatite
(Ca10F2(PO4)6) and Caryolite (Na3AlF6).
•Identified world reserves of fluoride are around 500 million t and
annual mine production is in excess of 4.5 million t.
•13th (Smith and Hodge, 1979) or 17th (Fleischer, 1953) most
abundant element in the earth crust.
• Depends on the geology, chemistry, physical characteristics and
climate of the area.
• If water is not in contact with high fluoride minerals the
range of concentration is from 0.01 to 0.4mg/L.
• The highest fluoride concentration tend to occur in arid
• The Rift Valley of East Africa has the highest concentration on
record, upto 300 mg/l
• 600 known, active volcanoes
• Halmer et al. (2002) have estimated the global
annual emmision of HF from valcanoes are being
from 7000 to 8000 kt.
• The total atmospheric inorganic fluoride under 0.1
and mostly <0.05µg/m3. (WHO, 2002)
• HF main form, others are; SiF, ammonium
flourosilicates, sodium flourosilicates, potasium
fourosilictes and potasium flouroborate.
• Roholm (1973) also reported the presence of NaF, MgF2, KF, CaF2.
Industrial Emission Of Fluoride
• Other sources are toothpastes, pharmaceuticals, wood preservatives and
• Result in the emission of gaseous and particulate fluoride into the atmosphere
• The combustion of coal
• Phosphate fertilizer and elemental phosphorus
• Iron and steel manufacture.
EPA Licensing Of Fluoride
• Portland Aluminium has an EPA Licence outlining
emission limits for fluoride.
• Licence limits set out in EPA licences require emissions to
be well within safe levels.
Rate Of Fluoride Deposition
• Chamberlain (1996)
Rate of deposition(µg/m2/s) = conc. in air (µg/m3) × deposition
• The deposition velocity, Vg, varies with the form of fluoride
(gas or particulate), particle size, wind speed, and the
nature of the plant canopy particularly its architecture and
Fluoride In Water
• Dissolve in water and split into ions.
• Speed of dissolution depend on pH, type of compound.
• Transport and transformation is influence by pH, hardness
and presence of clay.
• As they travel through the water cycle fluorides usually
combine with Aluminium.
Fluoride In Soil
• Fluoride is so strongly adsorbed 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
• Absorbed through leaf
• Move by transpiration into the
principal sites of accumulation
at the tip and leaf margins.
• In plant roots through passive
• Transported to the shoots via
• Onset symptoms depends on
Type and age
Composition of the air Rate of circulation
Type of light
• The injury starts as a gray or light-green water-soaked
lesion, which turns tan to reddish-brown.
• With continued exposure
Necrotic areas increase in size
Spreading inward to the midrib on broad leaves
Downward on monocot leaves
Fluoride injury symptoms on leaves of Gladiolus and Douglas fir.
• Effects of fluoride has been studied on Pinus ponderosa
by Solberg et al. (1955).
• Benedict and Breen (1955) have used weeds in evaluating
vegetation damage caused by air containing hydrogen
fluoride and other air pollutants.
• Fluoride is reported to cause adverse effects on plant
growth and yield.
Biochemical And Physiological
Impacts Of Fluoride Contamination
• The high internal fluoride concentration disturbs almost
all physiological and biochemical process in plants.
• A number of cellular processes identified to cause
deleterious effects on plants disruption of enzymes
Protein secretion and synthesis
Generation of reactive oxygen species
Alteration of gene expression
At micro molar
At milli molar concentrations
Acts as an anabolic reagent
Promotes cell proliferation
It acts as enzyme inhibitor
• Fluoride disrupts enzyme activity by binding to functional
amino groups that surrounds the enzyme’s active center.
• Inhibition of protein synthesis and secretion interrupts the
signaling pathway involves involved in cell proliferation
• Fluoride can increase oxidative stress
• Fluoride is a hazardous for both animal and plants.
• It causes serious damage to the crops grown in the
vicinity of fluoride.
• It effects almost all the biochemical and physiological
process of the plant that ultimately led to the reduction in
• Strict measures should be taken to avoid fluoride
• L.H. Weinstein, A.W. Davison; Fluoride in the Environment,
CABI publishers, Cambridge, USA, 2004.
• Greenwood, Delbert A., "Some Effects of Inorganic
Fluoride on Plants, Animals, and Man" (1956). USU Faculty
Honor Lectures. Paper 41.
• M. Baunthiyal, S. Ranghara, P. Garhwal; Physiological And
Biochemical Responses Of Plants Under Fluoride Stress:
An Overview, Research review Fluoride 47(4)287–293
• M.N. Ahmad, et al., Hydrogen Fluoride Effects On Local
Mung Bean And Maize Cereal Crops From Peri-Urban
Brick Kilns In South Asia, Research report Fluoride
47(4)315–319 October-December 2014.
• S. F. Yang And G. W. Miller, Biochemical Studies on the
Effect of Fluoride on Higher Plants, Biochem. J. (1963) 88,
• P. C. Mishra, S. K. Sahu, A. K. Bhoi, S. C. Mohapatra,
Fluoride Uptake and Net Primary Productivity of Selected
Crops, Open Journal of Soil Science, 2014, 4, 388-398.
• Summary & Details: Green Facts, Scientific Facts on
fluoride, source document IPCS (2002).