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CHAPTER – VII

Determination of Fluoride

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Introduction:

Fluoride is a naturally occurring compound derived from

fluorine, the 13th most abundant element on earth‟s crust. It occurs

in combined form because of its high reactiveness. It is present

naturally in almost all foods and beverages including water, but

levels of which can vary widely. Fluoridation is the addition of fluoride

compounds into drinking water, to adjust concentrations to levels between

0.8 and 1.0 mg/Lt for the beneficial effect of tooth decay prevention. The

fluoride accumulation of ground water varies according to the

source of water, geological formulation of the area and amount of

rain fall etc.,

Traces of fluorides are present in many waters, higher

concentrations are often associated with underground sources

which in turn vary with the type of rock the water flows through.

Low concentrations (0.6-1.5mg/lt) provide protection against dental

caries, especially in children. Fluoride can also have an adverse

effect on tooth enamel and may give rise to mild dental Fluorosis. In

India, approximately 62 million people including 6 million children

suffer from fluorosis because of high consumption of high Fluoride

content. Longer exposure to Fluoride leads to certain types of bone

diseases. Statistics reveal that fluoride poisoning is more spread

than the Arsenic contamination in ground water in the country.

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Water fluoridation is the controlled addition of fluoride

to a public water supply to reduce tooth decay. Fluoridated water

has fluoride at a level that is effective for preventing cavities; this

can occur naturally or by adding fluoride.(2) Fluoridated water

operates on tooth surfaces: in the mouth it creates low levels of

fluoride in saliva, which reduces the rate at which tooth enamel

demineralizes and increases the rate at which it remineralizes in the

early stages of cavities.(3) Typically a fluoridated compound is added

to drinking water, a process that in the U.S. costs an average of

about $0.95 per person-year.(2)(4) Defluoridation is needed when the

naturally occurring fluoride level exceeds recommended limits.(5) A

1994 World Health Organization expert committee suggested a level

of fluoride from 0.5 to 1.0 mg/L (milligrams per litre), depending on

climate(6) Bottled water typically has unknown fluoride levels, and

some domestic water filters remove some or all fluoride(7)

Dental caries remain a major public health concern in most

industrialized countries, affecting 60–90% of school children and the

vast majority of adults.(8) Water fluoridation prevents cavities in both

children and adults.(9) with studies estimating an 18–40% reduction

in cavities when water fluoridation is used by children who already

haveaccess to toothpaste and other sources of fluoride.(2) Although

water fluoridation can cause dental fluorosis, which can alter the

appearance of developing teeth, most of this is mild and usually not

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considered to be of aesthetic or public-health concern.(10) There is no

clear evidence of other adverse effects. Moderate-quality studies

have investigated effectiveness; studies on adverse effects have been

mostly of low quality.(11) Fluoride's effects depend on the total daily

intake of fluoride from all sources. Drinking water is typically the

largest source,(12) other methods of fluoride therapy include

fluoridation of toothpaste, salt, and milk.(13) Water fluoridation,

when feasible and culturally acceptable, has substantial advantages,

especially for subgroups at high risk(8)

The goal of water fluoridation is to prevent a chronic disease

whose burdens particularly fall on children and on the poor.(19) Its

use presents a conflict between the Common good and individual

rights.(20) It is controversial,(21) and opposition to it has been based

on ethical, legal, safety, and efficacy grounds.(22) Health and dental

organizations worldwide have endorsed its safety and

effectiveness.(3) Its use began in 1945, following studies of children in

a region where higher levels of fluoride occur naturally in the

water(23) Researchers discovered that moderate fluoridation prevents

tooth decay(24) and as of 2004 about 400 million people worldwide

received fluoridated water(18)

The major sources of Fluoride in ground water are Fluoride

bearing rocks such as fluorspar, cryolite, fluorspatite and

hydroxylapatite etc.

134

Fluoride Effects

Fluoride affected teeth

Fluoride affected legs Fluoride affected women

135

Fluoride contaminated water Fluoride contaminating ground water

Fluoride contaminating stream

136

The Guntur district with a geographical area of 11,328 sq.

kms falling between Latitudes 15o44' & 16o47' North. and

Longitudes 79o10' & 80o55' East is one of the Central coastal

districts of Andhra Pradesh. It comprises 57 mandals under

administrative control of 3 divisions namely Narasaraopet, Guntur

and Tenali (Fig.1).

Water samples(Bore Well & Open well ) collected from 16

sampling stations selected for the analysis were given below: S1

– Durgi S2 –Rayavaram , S3 -Adigoppula, S4 –Terla , S5 -

Karampudi, S6 –Macherla S7 –Ganapavaram , S 8-Chirumamilla S9

-Piduguralla , S10 -Nugendla , S11 -Epuru, S12 -Vinukonda, S13 -

Narmalapadu S14 - Bollapalli S15- Korampudi and S16 -Naguleru .

Samples for analysis were collected in sterilized bottles

using the standard procedure for grab (or) catch samples in

accordance with standard methods of APHA (1995) while collection

temperature of these areas was noted by 1100C thermometer. The

analysis of parameters namely pH, temperature and Fluoride were

carried out – as per the methods described in APHA (1995).

Determination of Fluoride has been carried out using fluoride ion

selective electrode. All the chemicals and reagents used were of

137

analytical grade. D.D water was used for the preparation of

solutions.

Environmental contamination by fluorides exposes

many organisms to potentially toxic effects and may exert some

stress on the ecological interrelationships among plant and animal

populations in natural biological communities. Research to date has

focused on human beings and species important to humans,(25)

relatively little is known of the potential ecological consequences of

fluoride pollution. This article presents a literature review of what is

known about the ecologicaleffects.

In brief, the available data fall short of providing

conclusive proof that any major, significant, or irreversible ecological

changes have occurred, or are likeIy to occur, as a result of existing

levels of fluoride pollution. (In this context, ecological effects means

changes in the balance of natural ecosystems, not the very severe

damage to commercial timber crops and livestock that has occurred

because of fluoride pollution. See, for example, “Fluorides in the air”

Environment, April 1973. Nevertheless, the available evidence does

support the view that fluorides are pollutants with considerable

potential for producing ecological damage. The compounds are

potentially serious contaminants not only when present in highly

localized, massive concentrations, but also when distributed in low-

138

level amounts over a long period of time. As future research begins

to bring potential ecological impacts of fluoride into better focus, it

seems very likely that proof will develop that the ecosystem does

suffer damage when fluoride levels of the magnitude discussed here

are present.

The evidence which supports concern over potential

ecological impacts of low-level fluoride pollution can be summarized

as follows:

* Levels of fluoride air pollution capable of leading to significant

accumulation in vegetation and consequent injury to some sensitive

plants have occurred several miles or more from sources of fluoride

emissions, despite air pollution controls.

* Significant fluoride accumulation has been demonstrated in

insects and in birds and mammals that feed on plants in the vicinity

of pollution sources. The accumulated levels have been high enough,

in some cases, to be potentially toxic, and such buildup represents a

major increase of fluoride in food chains.

seems capable of producing downstream concentrations of 0.5 to 3

parts per million (ppm). Concentrations are highest during summer

months, when biological activity is also at its peak. Some reports of

toxic effects in algae and freshwater vertebrates at 1 to 2 ppm

139

fluoride have been published. Most invertebrate species studied can

accumulate significant bodily burdens of fluoride at this level of

pollution, and there are indications that aquatic vegetation may also

concentrate the element. It seems very likely that fluoride is

accumulating, and probably being magnified, along aquatic food

chains.

* Substantial amounts of fluoride are transferred to the soil each

year. The degree to which this fluoride is available for uptake by soil

organisms, and the extent to which soil life may be affected by

fluoride in the environment, remain unknown.

* Possible conversion of fluoride into fluoroacetate (more toxic than

fluoride itself and related organic forms), and the likelihood that

fluoride may enter into synergistic actions with other contaminants,

greatly expand the potential for ecological damage by low-level

fluoride contamination.

Fluoride Air Pollution:

Estimates by the National Research Council and the

Environmental Protection Agency (27) suggest that between 120,000

and 155,000 tons of fluoride (calculated as hydrogen fluoride) are

emitted into the atmosphere each year in the U.S. Fluoride is

released from a variety of sources including aluminum smelting and

140

phosphate processing operations; the combustion of coal; and the

manufacture of steel, brick, tile, clay, and glass products.

Reductions in fluoride emissions with increasing application of

control regulations may be offset by the rapid growth of some

fluoride sources, particularly phosphate fertilizer and

aluminum production.

Most major fluoride sources use wet scrubbers to

remove the pollutant from exhaust streams. Such controls are

essential because concentrations as low as one part per billion (ppb)

in ambient air are capable of causing serious damage to vegetation

and may threaten livestock. (26)Concentrations of 10 ppb or higher

have been measured in the immediate vicinity of a source, (28)and

fluoride levels in the 1 ppb range may occur for several miles

downwind of an emission point. In general, however, except

downwind of a source, or in urban areas where many sources are

present, the air rarely contains measurable fluorides.

Environmental Effects:

According to a review by the US Department of Agriculture,

fluorides have done more damage to livestock, worldwide, than any

other air pollutant.(29) Some plants, including several important

timber varieties of coniferous trees, are sensitive to fluoride

damage.(26) Concentrations of 1.0 ppb or less can lead to long-term

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environmental damage because of biological magnification (the

significant increases in pollutant concentrations which occur at

each successively higher level in a food chain(28) Some forage grasses

can accumulate 200,000 times the level of fluoride present in the

surrounding air.(26)Prolonged ingestion of contaminated forage by

livestock can lead to excessive accumulation of fluoride in the bones

which may, in turn, produce skeletal deformities and other damage

to the animals' health.(30)

Several studies in the past five years have begun to explore

potential effects of fluoride on natural vegetation and wildlife species

not previously investigated. For example, when samples of lichens

and mosses were exposed to pollution from an aluminum smelter in

Quebec in four- or twelve-month studies at distances of from about

one-half to nine miles downwind of the source, the lichens showed

severe fluoride injury symptoms, especially near the source, and

both lichens and mosses accumulated the pollutant. Lichens,

exposed for four months about one-half mile from the source had

990 ppm, mosses, 570 ppm Even samples nine miles from the

source showed 190 ppm (lichens, at four months) and 78 ppm

(mosses, at twelve months).(32) Similar accounts of the effects of

fluorides on lichens in Pennsylvania and Scotland have been

published(33).

Several scientific groups in Montana recently investigated

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the effects of fluoride on a wide range of plants and animals exposed

to the contaminant. The polluted areas studied were near the

Anaconda Aluminum Company smelter in Columbia Falls and the

Rocky Mountain Phosphate Company plant in Garrison. Despite

pollution control measures employed by both companies (reported to

be 99 percent efficient in controlling fluoride emissions), fluoride

contaminated the environment and accumulated in a large number

oforganisms.

Vegetation in a 400-square-mile area downwind of the

Columbia Falls aluminum smelter accumulated significantly

elevated levels of fluoride (more than 10 ppm); on more than one-

quarter of that area, foliage levels exceeded 30 ppm(34) Several

species of pines, firs, grasses, hay, and a large number of of shrubs

and herbs were sampled, and many were found to contain

significant amounts of fluoride, even at distances of more than

twenty miles from the source. Insects of several dozen species were

captured in the polluted area, and almost all samples had high

levels of fluoride. Control samples, taken from a non polluted area,

showed fluoride levels of 3.5 to 16.5 ppm in their tissues while

insects from the study area had 6.1 to 585 ppm. Insects from the

pollinator group (such as bees) generally had the highest fluoride

levels. Some species that are predatory throughout their life cycles

143

had an elevated fluoride content, suggesting the transfer of the

pollutant through the food chain.(35)

University of Montana investigators analyzed the

thigh bones of more than 300 animals taken from different parts of

the study area. They found that skeletal fluoride accumulation was

10 to 40 times higher than that in animals taken from non polluted

areas. Many of the chipmunks, ground squirrels, and other

mammals and birds in the sample had bone fluoride levels in excess

of 1,000 ppm, and several individual animals had concentrations of

from 5,000 to 13,333 ppm(36)

The investigation of the area around the Garrison

phosphate operation revealed a similar, although geographically

more limited, pattern. The fluoride levels of many samples of

vegetation exceeded the 35 ppm state standard, some samples

contained more than 100 ppm. Animal specimens had above

normal accumulations which correlated well with the

concentrations in plants at the sites where the animals were

trapped.(37)

A similar study showed significantly elevated fluoride

levels in grass, and in bones of sparrows and frogs near an

aluminum smelter in Czechoslovakia.(38) In general, however, few

other data have been gathered on the potential impact of fluoride

pollution on wildlife species.

144

Although the data available to date are few, they fit a

pattern. The ability to accumulate fluoride from very low ambient air

concentrations, and to build up levels of 10 to 100 ppm or more

appears to be very widespread among different kinds of vegetation. A

broad range of herbivorous (plant-eating) animals in polluted

regions, sometimes many miles from the source of pollution, seem to

be accumulating substantial fluoride, primarily through their diet.

Levels in animals are generally higher relative to control sample

levels than levels in plants, reflecting the magnified effects which

occur as a pollutant moves up the food chain. Since very few

samples of predatory animals have been analyzed, no solid

conclusions can be drawn about the potential hazards to animals

higher in food chains. However, experience with other food chain

pollutants (for example, DDT) indicates that predators are often

hardest hit by cumulative contaminants. It seems urgent, therefore,

to obtain further data on fluoride accumulation in predatory

species.

Fluoride Toxicity:

The potential biological and ecological significance of fluoride

accumulation, as reported in these studies, is not easy to evaluate.

In general, there is little information available on the toxicity of

fluoride to most wildlife species. Data on domestic plants and

livestock indicate wide differences in the sensitivity, of various

145

species to fluoride injury.(39) Some conifers are among the most

sensitive plant varieties. Investigators in Montana reported that

pines, especially the western white pine, were dying out over

hundreds of acres near the aluminum plant in their study. They

concluded that loss of the pine trees was altering the normal

ecological succession of the forest community at those sites and

could lead to major changes in the vegetation patterns of the area.

(40) It is not known whether fluoride may be having injurious effects

on other important members of the plant community in the polluted

areas, but should such effects occur, they would alter not only the

balance of vegetative types, but of animals as well.

Extensive studies on domestic animals indicate that 30

to 40 ppm fluoride in forage can be seriously toxic to cattle when

ingested on a prolonged basis, and that sheep, swine, and other

species seem to be able to tolerate higher amounts of fluoride in

their feed(30) Data on herbivorous wildlife species are not available,

but it should be assumed, in the absence of contrary information,

that fluoride levels of 30 ppm or more found in large areas in

Montana may represent a hazard to animals which habitually feed

on the contaminated vegetation.

In domestic cattle, skeletal concentrations ranging from

1,450 to over 8,000 ppm have been associated with fluorosis

(fluoride poisoning), and bones from a horse injured by fluoride

146

pollution had 1,060 to 1,500 ppm(30) Although no direct relationship

was established between skeletal fluoride accumulation and health

effects in the animals in Montana, it seems logical that at least those

animals in which skeletal fluoride exceeded 5,000 ppm could have

suffered some adverse health impact.

Some information on fluoride toxicity to insects is available.

Mulberry leaves containing 10 to 15 ppm fluoride were lethal to

silkworm larvae, while leaves containing lower fluoride levels led to

reduced growth of the insects.(41) In other studies,(42) sodium

fluoride added to flour affected the survival and reproduction of the

flour beetle, Tribolium confusum; some concentrations appeared to

inhibit, and others to enhance, egg production. Considerable

evidence is available to indicate that honeybees are highly sensitive

to fluoride. Bee colonies in the vicinity of fluoride sources have

frequently been heavily damaged. Two of the Montana investigators

commented that the highest accumulation of fluoride among insects

in their study was in members of the pollinator group.(40) They

speculated that if other pollinators should prove as susceptible to

fluoride injury as the honeybee, patterns of pollination in a polluted

region could be substantially altered; and, as a consequence, the

abundance of many insect-pollinated plants could shift, with

attendant major changes in the ecology of an entire community.

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It must be emphasized that research to date has not probed

for such ecological effects, and we cannot say that they are

occurring in the vicinity of fluoride air pollution sources.

Nevertheless, the potential for such effects seems real enough,

making this an area in which more research would be

desirable.

Water Pollution Sources:

While fluoride air pollution primarily occurs in the vicinity

industrial sources, fluoride is released into the aquatic environment

by a far wider range of sources, and it seems very likely that most

bodies of water are contaminated by fluoride to some extent. Some

fluoride is present in waters from natural sources. Many minerals

contain soluble fluoride, and when ground water passes through

such fluoride-bearing rock formations, the water may become

contaminated. A few sources, primarily deep wells, contain 1 ppm

fluoride or more. Most surface waters contain less than 0.2 ppm

fluoride, and the majority are below 0.1 ppm (43) The oceans, as the

result of eons of leaching of mineral salts from the land, contain

from 1.2 to 1.4 ppm fluoride, about half in the form of fluoride ion

and half in the relatively insoluble, magnesium fluoride complex ion.

(44) Although natural, or "background," fluoride levels in most fresh-

water streams are in the 0 to 0.2 ppm range, available data indicate

that concentrations above 0.5 ppm, and occasionally as high as 2 or

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3 ppm, may be fairly common in water courses contaminated

by human activities.

Several human activities result in substantial fluoride input

to the aquatic environment. Many of the industries which have

fluoride air pollution problems are also sources of fluoride water

pollution. Air pollution control equipment often produces a fluoride

laden liquid waste which requires disposal. (Fluoride can be

removed from wastewater by treatment with lime in settling ponds, a

form of treatment which can reduce the fluoride content of an

effluent stream from more than 5,000 ppm to about 5 to 50 ppm)

(45)Aggregate figures for all fluoride sources are not available, but the

phosphate industry may discharge from 6,000 to 30,000 tons of

fluoride into waterways in the US annually.(46) The Environmental

Protection Agency has proposed standards for the primary

aluminum industry which, starting in 1977, would restrict fluoride

in wastewater discharge to an average of two pounds per ton of

aluminum produced. If all aluminum smelters were currently

meeting that standard, fluoride discharges would be 4,000 to 5,000

tons per year from this industry. However, only about one-third of

the plants now in operation are presently in compliance, so actual

fluoride pollution from the aluminum industry is probably

substantially larger.(47) Fluoride discharges from other industries are

not negligible, but are probably smaller than from phosphate and

149

aluminum operations.

Another significant source of fluoride water pollution is

domestic sewage. Approximately one-half of the communities in the

US which have centralized water distribution systems now add

fluoride to their water supplies for the partial control of tooth decay.

(48) Provision of fluoridated water for 100 million people requires the

addition of approximately 20,000 tons of fluoride to domestic water

supplies each year. Most of the water used in urban areas, and thus

most of the fluoride added to water supplies, is returned through

sewage systems to the aquatic environment.

A study of fluoride levels(49) in sewage in 56 California

cities demonstrated that domestic sewage already contains fluoride,

over and above that naturally present in water or added for dental

health. (50) Fluoride in human wastes, originating with fluoride in

foods, was tentatively identified as the source of the excess. The

investigator concluded that fluoride from toothpastes and other

sources would make a negligible contribution, and that no industrial

sources were contributing fluoride to the sewage samples studied.

The findings suggest that the total input of fluoride into the

environment from domestic sewage is probably more than the

20,000 tons estimated to be added to water supplies in communities

where fluoridation of drinking water takes place. Thus, even

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communities not fluoridating water may release significant fluoride

into receiving streams in their sewage.

The same study showed that secondary sewage treatment

(biological digestion of wastes) reduced fluoride in the final effluent

by an average of 57 percent, while primary treatment had no

appreciable effect on fluoride levels. Even with secondary sewage

treatment, however, it was concluded that significant amounts of

fluoride persisted in effluents.

Fluoride is present in phosphate fertilizers, and

some fluoride may be carried into surface waters in runoff from

agricultural lands. It is also likey that some portion of fluorides

emitted into the air is eventually carried by precipitation into surface

waters.(51) While these sources may be significant, good quantitative

estimates of the magnitude of fluoride input to the aquatic

environment by these routes are not available.

Environmental Concentrations:

Although fluoride air pollution leads to significant

environmental concentrations only in the vicinity of sources, low-

level fluoride water pollution appears to be morewidespread.

The US Geological Survey monitors water quality at several

thousand sites around the country, but fluoride data are not

routinely included in chemical analyses. Fluoride readings for some

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streams are available, however. Many rivers have fluoride contents

ranging from 0 to 0.2 ppm, but some have much higher levels. For

example, 1967 data for the Santa Ana River in California showed

fluoride levels of 0.9 to 3.6 ppm (average, 1.1 ppm), and single

readings in the Pit River (also in California) reached 1.8 and 2.1 ppm

(52) (Earlier monitoring at the same sites on the Pit River recorded

levels of 0.1 to 0.2ppm)(53)

A number of published studies relate environmental

fluoride concentrations to specific sources of the contaminant.

Tributaries of the East Gallatin River above the town of Bozeman,

Montana, contain 0.1 ppm fluoride or less, while the river below the

city's sewage outfall (the only fluoride source in the area) has been

found to have concentrations of 0.3 to 0.8 ppm(54)

Fluoride concentrations of from 0.17 to 2.06 ppm were

measured in a study of the Illinois River.(55)The highest

concentrations occurred during the summer months, when stream

volume was lowest. Fluoride sources upstream from the monitoring

site included several communities with fluoridated water supplies

and several major fertilizer manufacturing plants. A study of fluoride

input to Narragansett Bay, in Rhode Island, showed that 36 percent

of the fluoride entering the bay was due to fluoridation of water

supplies in five communities on rivers feeding into the estuary.(56)In

midsummer, pollution from these sources was enough to double the

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fluoride content of the rivers. A similar study in Japan showed

fluoride concentrations of 0.15 to 1.07 ppm in rivers feeding into

TokyoBay.(57)

Pollution near industrial sources, especially where only

limited wastewater treatment to remove fluoride is employed, can be

much more serious. Concentrations of 20 ppm or more were

reported for the Pamlico River (in North Carolina) near a phosphate

plant. (58)In most states where industrial fluoride discharge is a

problem, relevant water quality standards have been adopted.

Standards for drinking water sources generally are based on the US

Public Health Service Drinking Water Standards and prohibit

concentrations in excess of 1.5 to 2.0 ppm some states permit levels

of 5 to 10 ppm for bodies of water which are not sources of public

water supplies in order to prevent toxic effects to wildlife.(59)

Ecological Effects :

The critical question for biologists is whether chronic

exposure to these fluoride concentrations, which may be from two to

ten or more times higher than the background level, poses any

significant physiological or ecological hazard to aquatic life. It seems

reasonable to conclude that fluoride at these levels poses no major

risk to marine organisms. (56)Both the dilution factor, and the fact

that most oceanic forms evolved in an environment that contains

from 0.6 to 0.7 ppm fluoride ion, suggest that potential effects on

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marine life should be minimal if fluoride in rivers rarely exceeds 2

ppm However, freshwater organisms evolved in an environment that

was almost fluoride-free, and thus might be expected to be less well-

equipped to tolerate fluoride concentrations encountered in polluted

streams.

Relatively little is known about the potential impact of

fluoride on either freshwater or marine organisms. A number of

investigators have measured the short-term toxicity of various

fluoride compounds for a good number of species, but systematic

inquiries on the more general effects of long-term, low-level

pollution, analagous to the Montana air pollution studies discussed

above, have rarely been published. Thus, we may know the lethal

concentrations for many organisms, but we have very little

knowledge of the sublethal effects of fluoride on behavior or

reproductive processes, or of potential accumulation of the pollutant

in aquatic food chains. Yet such effects, should they occur, would

probably be more important ecologically than the mortality which

might result from very high, but short-lived, pollution episodes.(60)

Several investigators have exposed a variety of bacteria

and microscopic animal species that live in freshwater to a range of

fluoride concentrations extending well above those likely to be

encountered in streams, without any demonstrable toxic effects.

(61)Not many species have yet been tested, however, and the criteria

154

for evaluating toxicity were not sophisticated. The finding that

bacterial digestion of sewage removes much of the fluoride content of

the effluent (50)suggests that some bacteria may accumulate fluoride

from water. The importance of bacteria as a basic element in food

chains makes it important to learn more about the capacity of

microorganisms to bioconcentrate this contaminant.

The single-celled green alga Chlorella showed a 37

percent reduction in growth over 48 hours when exposed to a 2 ppm

fluoride solution; (62)43 ppm was reported lethal to another alga,

Scenedesmus. (63)Few other data on toxicity of fluoride to aquatic

plants are available, but several studies suggest that water plants

can accumulate the element. Five-day exposures to 100 ppm led to a

50-told concentration of fluoride by aquatic plants, and fourteen

days at 20 ppm produced a 38 fold increase. (51)Water hyacinths

absorb fluoride efficiently at concentrations above 10 ppm, and to a

much lesser extent at lower Ievels. (64)Several species of marine algae

(exposed to 0.5 to 0.7 ppm) contained 2 to 22 ppm fluoride. Eel

grass(65) and the alga Cladophora, however, showed no significant

fluoride buildup after seventy-two days in sea water with 52 ppm

fluoride. (66)One Russian study found an average fluoride content of

40.5 ppm in samples of several freshwater plants, (67)and other

studies strongly suggest that aquatic vegetation accumulates

fluoride. (68)However, the evidence as a whole is still too fragmentary

155

to provide a clear or systematic picture of the capacity for fluoride

buildup in aquatic plants.

Effects on Aquatic Animals:

Short-term fluoride toxicity data are available for a number of

invertebrate species, the majority of them marine varieties. Water

fleas are killed or immobilized by concentrations of various fluoride

compounds ranging from 5 to 500 ppm (69)Lobsters are not harmed

by 5 ppm fluoride.(70) Mussels may be killed by 1.4 to 7.2 ppm,(66)

and concentrations of 20 ppm or higher for extended periods have

been shown to be toxic or lethal to oysters, two species of crabs, and

a sand shrimp, but not to two types of prawns. (71) More significant

than the lethal effects of high concentrations, however, is the

marked ability demonstrated by almost all species studied in these

investigations to accumulate substantial bodily burdens of fluoride.

Even animals kept in sea water containing only 1 ppm fluoride had

bodily concentrations of from 100 to 300 ppm (72) The entry of

fluoride into food chains through bio concentration in aquatic

invertebrates is a subject in need of much more careful research.

Studies of the effects of fluoride on fish are far more

numerous than for any other form of aquatic life.(73)

Short-term lethal effects may occur at concentrations as low

as 3 ppm in sensitive species (for example, rainbow trout), while

156

other fish are not damaged until fluoride levels reach 100 ppm

Water temperature, hardness, chlorinity, and other environmental

factors, as well as the age and physiological state of the fish, can

influence the toxicity of a given concentration of fluoride.(74)

Sub lethal concentrations may have adverse effects on fish

behavior or reproduction, which could be ecologically significant.

Research findings are few and not confirmed, but trout eggs seem to

be delayed in development and hatching by 1.5 ppm fluoride.(75)

Fish are important food-chain organisms, and the ability

of many fish, like many other vertebrates, to accumulate elevated

fluoride levels in their skeletons (76) can introduce the contaminant

into the diet of fish-eating predators. Levels of 550 to 6,800 ppm

have been reported in bones of ocean fish, and 400 to 1,600 ppm in

trout from a naturally high-fluoride stream in Yellowstone National

Park. Such accumulation might pose a hazard to animals that eat

whole fish. Data on other aquatic vertebrates which may be

exposed to fluoride are sparse. Frogs were killed in one week by 900

ppm fluoride,(77) and decreased red and white blood cell counts were

observed in frogs kept in fluoride concentrations of 5 to 300 ppm

(78)There have also been indications that sub lethal fluoride

concentrations may adversely affect amphibian reproductive cycles.

(79)Frog eggs were retarded in development but hatched prematurely

in 1 ppm fluoride in well water, higher concentrations (13 to 450

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ppm) had the same effects on toad eggs, and metamorphosis in

tadpoles was significantly delayed by fluoride at 0.5 and4.5ppm.(80)

Most research on the effects of fluoride on aquatic organisms

dates back to the early 1960s or before, and more definitive studies

are required on the potential hazards suggested here. There is also a

pressing need to examine the potential impact of chronic, low-level

bioaccumulation of fluoride on predatory animals higher in aquatic-

based food chains. As is the case with fluoride air pollution, the logic

of ecosystem energy and nutrient flow patterns suggests that species

at the highest levels of a food chain are likely to bear the greatest

risk of harm, but virtually no effort has been made to look for such

damage. If fluoride has had such adverse effects on aquatic wildlife,

they have thus far been too subtle to attract attention. In the

absence of any substantive research data, it would be unwise to

assume that no risks exist.

Biological Effects:

The only research on the biological impacts of soils

contaminated by fluoride has dealt with uptake of the chemical by

plants. Data from one study showed that grasses grown in soils

containing 1,350 ppm fluoride could contain as much as 1,330

ppm(38 )In many similar reports, it has been observed that when

fluoride is present as both an air pollutant and a soil pollutant,

plant uptake from air (through the tiny openings in leaves where

158

gases are exchanged) is far more significant than from soil. Several

investigators have shown, however that substantial uptake can

occur from soil alone under some conditions.(86)

A number of investigators have shown that the uptake of

fluoride pollution from soil can have toxic effects on some plants.

For example, 1,000 to 1,500 ppm fluoride added to soil in one

experiment reduced the yield of winter wheat by 40 to 65 percent

and 400 ppm reduced growth of Tradescantia, a flowering plant by

28 to 34 percent; (80) a strong correlation has been demonstrated

between inhibition of pea seedling growth and increased fluoride

content of the soil, (81)and fluoride concentrations of 1.9 to 190 ppm

in soil reduced the growth of loblolly pine and red maple

trees.(82)

The most obvious ecological concerns arising from fluoride

pollution of the soil center around uptake of the contaminant by

plants, not only because of potential toxic effects to the plants

themselves, but also because the process may introduce additional

fluoride into the diets of animals.

But uptake by plants is just a small part of the possible impact

soil fluoride might have on living things. The soil is anything but a

sterile medium; it is, in fact, a very rich, and highly diverse,

ecosystem which includes thousands of species of microbes, fungus,

worms, and insects. (83) Many of these soil organisms are essential to

159

the fertility of the land - for example, they convert nitrogen to a form

useful to plants, help break down organic matter and by turning the

soil, help aerate it. Disruptions by soil ecology by toxic pollutants

could potentially reduce the land's ability to support plant life, and

thus, all life.

Whether the fluoride now being added to soils in fertilizers and

as fallout from air pollution poses any real threat to the ecological

balance of the soil community cannot be determined yet. There are

virtually no published data on the toxicity of fluoride to soil

organisms, or the potential for accumulation of fluoride in soil food

chains. Until research has been conducted on this subject, we will

have no way of knowing, but the possibility must be considered that

fluoride may be potentially

Materials and methods:

The Guntur district with a geographical area of 11,328 sq.

kms falling between Latitudes 15o44' & 16o47' North. and

Longitudes 79o10' & 80o55' East is one of the Central coastal

districts of Andhra Pradesh. It comprises 57 mandals under

administrative control of 3 divisions namely Narasaraopet, Guntur

and Tenali (Fig.1).

Water samples(Bore Well & Open well ) collected from 16

sampling stations selected for the analysis of fluoride were given

bellow: S1 – Durgi S2 –Rayavaram , S3 -Adigoppula, S4 –Terla , S5 -

160

Karampudi, S6 –Macherla S7 –Ganapavaram , S 8-Chirumamilla S9

-Piduguralla , S10 -Nugendla , S11 -Epuru, S12 -Vinukonda, S13 -

Narmalapadu S14 - Bollapalli S15- Korampudi and S16 -Naguleru .

Samples for analysis were collected in sterilized bottles using

the standard procedure for grab (or) catch samples in accordance

with standard methods of APHA (1995) while collection temperature

of these areas was noted by 1100C thermometer. The analysis of

parameters namely pH, temperature and Fluoride were carried out –

as per the methods described in APHA (1995). Determination of

Fluoride has been carried out using fluoride ion selective electrode.

All the chemicals and reagents used were of analytical grade. D.D

water was used for the preparation of solutions.

Results and discussion:

The results of various parameters for the determination of

fluoride in various samples are presented in Table – 1 to 3.

Temperature:

Temperature of water is basically important because it

effects bio-chemical reactions in aquatic organisms. A rise in

temperature of water leads to the speeding up of chemical reactions

in water, reduces the solubility of gases and amplifies the tastes and

odours. The average temperature of the present study ranged from

26.38 - 28.040C. It is known that pH of water (6.5 to 8.5) does not

has no direct effect on health. But lower value below 5.0 produce

161

sore taste and has higher value above 8.5 are of alkaline taste. The

pH values of the present investigation were within the ICMR

standards (7.0 – 8.5).

Fluoride:

The major sources of Fluoride in ground water are Fluoride

bearing rocks such as fluorspar, cryolite, fluorspatite and

hydroxylapatite etc. Excess fluoride consumption affects plants and

animals. Out of 16 sampling stations studied in all most 12

samples, fluoride concentration remained within the permissible

limits for drinking water. On the other hand in the remaining 5

samples (S1, S2, S11, S12 and S15), the fluoride content is (exceeded

1.5 mg/lt) above the permissible limits prescribed by ICMR

standards.

Conclusions:

It is observed form the above study that fluoride content in

certain areas was found above the levels than required. Since

drinking water is a basic need, the people in those areas should

consume protected water containing fluoride within the prescribed

limits in order to prevent dental and skeletal Fluorosis for the future

generation. Fluoride concentration can be diluted by inducing

ground water recharge techniques, i.e., Construction of percolation

tanks, flooding of ground water by mixing surface water by

promoting rain water harvesting.

162

Table – 1 Physico – Chemical Parameters of Water Samples

Collected in October 2009

Station No. Temperature

(0

C)

Color pH Fluoride

(mg/lt.)

S1 28.28 Color less 7.36 1.05

S2 26.38 Color less 7.42 0.93

S3 27.04 Color less 8.20 0.72

S4 27.82 Color less 7.58 0.96

S5 28.12 Color less 7.35 0.77

S6 27.25 Color less 7.64 1.32

S7 27.82 Color less 7.81 0.62

S8 27.44 Color less 8.08 0.85

S9 26.67 Color less 6.97 1.42

S10 27.22 Color less 7.80 1.25

S11 27.52 Color less 7.62 1.38

S12 27.84 Color less 7.51 1.41

S13 26.92 Color less 7.24 1.05

S14 27.58 Color less 8.02 1.30

S15 28.26 Color less 7.61 1.03

S16 27.83 Color less 7.82 1.26

* All the values are the average of 3 determinations.

163

Table – 2 Water Samples Collected in November 2009

* All the values are the average of 3 determinations.

Station

No. Temperature

(0

C)

Color pH Fluoride

(mg/lt.)

S1 27.28 Color less 7.30 0.73

S2 26.92 Color less 7.64 0.54

S3 28.13 Color less 7.84 0.42

S4 27.22 Color less 7.50 0.86

S5 27.72 Color less 7.81 0.35

S6 27.35 Color less 7.61 0.39

S7 27.82 Color less 8.20 0.65

S8 27.4 Color less 8.44 0.59

S9 26.8 Color less 6.93 1.02

S10 27.2 Color less 7.21 1.25

S11 28.03 Color less 7.54 1.32

S12 27.80 Color less 7.51 1.41

S13 26.91 Color less 7.21 1.05

S14 27.5 Color less 8.05 1.25

S15 28.20 Color less 8.03 1.29

S16 27.38 Color less 8.24 1.08

164

Table – 3 Physico –Water Samples Collected in December 2009

* All the values are the average of 3 determinations.

Station

No. Temperature

(0

C)

Color pH Fluoride

(mg/lt.)

S1 28.05 Color less 7.16 0.68

S2 26.90 Color less 7.24 0.74

S3 28.03 Color less 7.84 0.59

S4 27.84 Color less 7.53 0.55

S5 28.32 Color less 7.64 0.65

S6 27.23 Color less 7.61 0.79

S7 27.82 Color less 8.20 0.72

S8 27.4 Color less 8.44 0.59

S9 26.8 Color less 6.93 1.05

S10 27.2 Color less 7.21 1.12

S11 28.03 Color less 7.54 1.32

S12 27.8 Color less 7.51 1.41

S13 26.9 Color less 7.21 1.05

S14 27.5 Color less 8.05 1.15

S15 28.2 Color less 8.21 1.09

S16 27.8 Color less 8.24 0.78

165

Table – 4 water samples collected in Jan’10

* All the values are the average of 3 determinations.

Station No. Temperature

(0

C)

Color pH Fluoride

(mg/lt.)

S1 27.05 Color less 7.36 0.84

S2 26.70 Color less 7.29 0.78

S3 27.40 Color less 7.80 0.52

S4 27.80 Color less 7.73 0.45

S5 27.32 Color less 7.14 0.52

S6 27.55 Color less 7.65 0.43

S7 27.08 Color less 7.80 0.52

S8 27.52 Color less 8.14 0.69

S9 26.38 Color less 6.98 1.02

S10 27.25 Color less 7.43 0.92

S11 27.03 Color less 7.24 1.02

S12 27.22 Color less 7.51 1.22

S13 26.93 Color less 7.41 1.03

S14 27.56 Color less 7.85 0.95

S15 27.21 Color less 8.04 1.08

S16 27.35 Color less 7.54 0.85

166

Table – 5 Physico chemical parameters of water samples

collected in February 2010

* All the values are the average of 3 determinations.

Station No. Temperature

(0

C)

Color pH Fluoride

(mg/lt.)

S1 28.25 Color less 7.16 0.96

S2 27.75 Color less 7.55 1.04

S3 28.13 Color less 7.88 0.79

S4 28.54 Color less 7.62 0.77

S5 28.3 Color less 7.34 0.55

S6 29.04 Color less 7.68 0.69

S7 27.95 Color less 8.20 0.8

S8 27.78 Color less 8.34 0.69

S9 27.53 Color less 7.95 1.05

S10 28.2 Color less 7.71 1.20

S11 28.13 Color less 8.24 1.42

S12 27.97 Color less 7.58 1.38

S13 27.92 Color less 8.21 1.05

S14 27.75 Color less 8.22 1.25

S15 28.15 Color less 8.18 1.47

S16 28.65 Color less 8.20 1.05

167

Table – 6

water samples collected in March 2010

* All the values are the average of 3 determinations.

Station

No. Temperature

(0

C)

Color pH Fluoride

(mg/lt.)

S1 28.28 Color less 7.56 2.05

S2 26.92 Color less 7.49 1.73

S3 27.44 Color less 8.20 0.85

S4 27.89 Color less 7.82 0.92

S5 28.32 Color less 7.55 0.89

S6 29.05 Color less 7.64 1.24

S7 27.8 Color less 7.81 1.42

S8 27.62 Color less 8.25 0.85

S9 27.77 Color less 7.03 1.30

S10 28.26 Color less 8.10 1.15

S11 29.12 Color less 8.32 1.64

S12 27.84 Color less 7.76 1.79

S13 27.62 Color less 7.86 1.35

S14 27.83 Color less 8.22 1.20

S15 28.18 Color less 7.65 2.12

S16 27.96 Color less 7.87 1.42

168

00.20.40.60.8

11.21.41.6

S1 D

urg

i

S2 R

ayav

aram

S3 A

dig

op

pu

la

S4 T

erla

S5 K

arem

pu

di

S6 M

ach

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S7 G

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S8 C

hir

um

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S9 P

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S10

Nu

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S12

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S13

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S14

Bo

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S15

Nad

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la

S16

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ru

mg/

litVariation of Fluoride in Oct'09

Fluoride (mg/lt.)

00.20.40.60.8

11.21.41.6

S1 D

urg

i

S2 R

ayav

aram

S3 A

dig

op

pu

la

S4 T

erla

S5 K

arem

pu

di

S6 M

ach

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S7 G

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S8 C

hir

um

amill

a

S9 P

idu

gura

lla

S10

Nu

gen

dla

S11

Ep

uru

S12

Vin

uko

nd

a

S13

Nar

amal

apad

u

S14

Bo

llap

alli

S15

Nad

end

la

S16

Nag

ule

ru

mg/

lit

Variation of Fluoride in Nov'09

Fluoride (mg/lt.)

169

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

S1 D

urg

i

S2 R

ayav

aram

S3 A

dig

op

pu

la

S4 T

erla

S5 K

arem

pu

di

S6 M

ach

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S7 G

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am

S8 C

hir

um

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S9 P

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lla

S10

Nu

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S11

Ep

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S12

Vin

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nd

a

S13

Nar

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apad

u

S14

Bo

llap

alli

S15

Nad

end

la

S16

Nag

ule

ru

mg/

litVariation of Fluoride in Dec'09

Fluoride (mg/lt.)

0

0.2

0.4

0.6

0.8

1

1.2

1.4

S1 D

urg

i

S2 R

ayav

aram

S3 A

dig

op

pu

la

S4 T

erla

S5 K

arem

pu

di

S6 M

ach

erla

S7 G

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am

S8 C

hir

um

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a

S9 P

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gura

lla

S10

Nu

gen

dla

S11

Ep

uru

S12

Vin

uko

nd

a

S13

Nar

amal

apad

u

S14

Bo

llap

alli

S15

Nad

end

la

S16

Nag

ule

ru

mg/

lit

Variation of Fluoride in Jan'10

Fluoride (mg/lt.)

170

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

S1 D

urg

i

S2 R

ayav

aram

S3 A

dig

op

pu

la

S4 T

erla

S5 K

arem

pu

di

S6 M

ach

erla

S7 G

anap

avar

am

S8 C

hir

um

amill

a

S9 P

idu

gura

lla

S10

Nu

gen

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S11

Ep

uru

S12

Vin

uko

nd

a

S13

Nar

amal

apad

u

S14

Bo

llap

alli

S15

Nad

end

la

S16

Nag

ule

ru

mg/

litVariation of Fluoride in Feb'10

Fluoride (mg/lt.)

0

0.5

1

1.5

2

2.5

S1 D

urg

i

S2 R

ayav

aram

S3 A

dig

op

pu

la

S4 T

erla

S5 K

arem

pu

di

S6 M

ach

erla

S7 G

anap

avar

am

S8 C

hir

um

amill

a

S9 P

idu

gura

lla

S10

Nu

gen

dla

S11

Ep

uru

S12

Vin

uko

nd

a

S13

Nar

amal

apad

u

S14

Bo

llap

alli

S15

Nad

end

la

S16

Nag

ule

ru

mg/

lit

Variation of Fluoride in Mar'10

Fluoride (mg/lt.)

171

Variation of Fluoride in different months at different Stations

Station Oct Nov Dec Jan Feb Mar

S1 Durgi 1.05 0.73 0.68 0.84 0.96 2.05

S2 Rayavaram 0.93 0.54 0.74 0.78 1.04 1.73

S3 Adigoppula 0.72 0.42 0.59 0.52 0.79 0.85

S4 Terla 0.96 0.86 0.55 0.45 0.77 0.92

S5 Karempudi 0.77 0.35 0.65 0.52 0.55 0.89

S6 Macherla 1.32 0.39 0.79 0.43 0.69 1.24

S7 Ganapavaram 0.62 0.65 0.72 0.52 0.8 1.42

S8 Chirumamilla 0.85 0.59 0.59 0.69 0.69 0.85

S9 Piduguralla 1.42 1.02 1.05 1.02 1.05 1.3

S10 Nugendla 1.25 1.25 1.12 0.92 1.2 1.15

S11 Epuru 1.38 1.32 1.32 1.02 1.42 1.64

S12 Vinukonda 1.41 1.41 1.41 1.22 1.38 1.79

S13 Naramalapadu 1.05 1.05 1.05 1.03 1.05 1.35

S14 Bollapalli 1.3 1.25 1.15 0.95 1.25 1.2

S15 Nadendla 1.03 1.29 1.09 1.08 1.47 2.12

S16 Naguleru 1.26 1.08 0.78 0.85 1.05 1.42

172

0

0.5

1

1.5

2

2.5S1

Du

rgi

S2 R

ayav

aram

S3 A

dig

op

pu

la

S4 T

erla

S5 K

arem

pu

di

S6 M

ach

erla

S7 G

anap

avar

am

S8 C

hir

um

amill

a

S9 P

idu

gura

lla

S10

Nu

gen

dla

S11

Ep

uru

S12

Vin

uko

nd

a

S13

Nar

amal

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u

S14

Bo

llap

alli

S15

Nad

end

la

S16

Nag

ule

ru

Flu

ori

de

Co

nce

ntr

atio

n m

g/lt

Variation of Fluoride in differant months

Oct '09

Nov'09

Dec'09

Jan'10

Feb'10

Mar'10

173

174

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44) Riley, J.P., and G. Skirrow, Chemical Oceanography, vol. 2,

Academic Press, New York, 1965.

45). U.S. Environmental Protection Agency, Development Document

for Proposed' Effluent Limitations Guidelines and New Source

Performance Standards for the BASIC FEW TILIZER CHEMICALS

Segment of the Fertilizer Manufacturing Point Source Category,

Report No. EPA 440/1-73-011, Washington, D.C., Nov. 1973;

Development Document for Proposed Effluent Limitations Guidelines

and New Source Performance Standards for the PRIMARY

ALUMINUM SMELTING Subcategory of the Aluminum Segment of

the Nonferrous Metals Manufacturing Point Source Category, Report

No. EPA 440/1-73-019a, Dec. 1973.

46). The estimated tonnage of fluoride discharged as water pollution

by the phosphate industry was calculated as follows: Some 40

million tons of phosphate rock are mined annually in the U.S..

which may contain 2.5 to 4.5 percent fluoride by weight (USEPA,

Rep. No. EPA 440/1-73-011, ibid.). From 30 to 90 percent of the

180

fluoride may be evolved in gaseous or particulate form in the

processing of the rock into various phosphate products (USEPA,

ibid.; Marier and Rose, loc. cit.). If it is assumed that the average

fluoride content of rock processed is 3 percent and that 50 percent

of this is evolved in processing, some 600,000 tons of potential

fluoride air pollutants will be generated. Air pollution control devices

range up to 99 percent, plus. in efficiency; thus up to 594,000 tons

of fluoride (or more) Is likely to be retained in scrubber liquors. Lime

treatment and settling in gypsum ponds can remove 95 to 99

percent of the fluoride from wastewaters. Lacking exact data on the

efficiency of control measures currently employed throughout the

industry, I have simply assumed that between 1 percent and 5

percent of the fluoride in waste streams eventually reaches the

environment in effluent discharges, that is 5,940 to 29,700 tons per

year. If the actual state of controls in the industry averages less than

95 percent efficient, the figure would of course be higher.

47). U.S. EPA, Rep. No. EPA 440/1-73-011, loc. cit.

48). U.S. Public Health Service, Fluoridation Census, National

Institutes of Health, Bethesda, Md., 1970.

49) Todd, D.K., The Water Encyclopedia, Water Information Center.

Part Wasington, N.Y., 1970).

50) Masuda, T.T., "Persistence of Fluoride from Organic Origins In

Waste Waters," Developments in Industrial Microbiology, 5:53-70,

181

1964.

51). Marier and Rose, loc. cit.

52). U.S. Geological Survey, Water Quality Data, 1967, Part 11,

USGS Water Supply Paper No. 2015, Dept. of the Int., Washington,

D.C., 1972.

53). US. Geological Survey, Water Quality Data, 1962, Parts 9-14,

USGS Water Supply Paper No. 1945, Dept. of the Interior,

Washington, D.C., 1964.

54) BahiS, L.L., "Diatom Response to Primary Wastewater Effluent,"

J. Water Poll. Cant. Fed. 45:134-144, 1973. Soitero, R.A., "Chemical

and Physical Findings from Pollution Studies on the East Gallatin

River and its Tributaries," Water Research, 3:687-706, 1969.

55)Wang, W.C., and R.L. Evans, "Dynamics of Nutrient

Concentration in the Illinois River,". J. Water Poll. Cant. Fad.. 42: 2

117'3123, 19M.

56). Miller. G.R., Jr., K. Woolsey, and D.R. Kester, "Fluoride

Chlorinity Ratios In Narragansett Bay." Graduate School of

Oceanography, University of R.I, Kingston, R.I., ref. no. 72-1, 1972.

57). Kitime, Y., and V. Furukawa, "Distribution of Fluoride in Waters

of Tokyo Bay," J. Oceanographic Sac. Japan, 28(3):121-125, 1972.

58). Moore, O.J.. "The Uptake and Concentration of Fluoride by the

Blue Crab, Callinectes sapidus," Chesapeake Science, 12:1-13,

1971.

182

59). McKee, J.E., and H.W. Wolf, Water Quality Criteria, California

State Water Quality Control Board, Washington, D.C., Sept. 1971.

60). Sprague, J.B., "Measurement of Pollutant Toxicity to Fish, III.

Sublethal Effects and 'Safe' Concentrations," Water Research. 5-

245-266, 1971.

61).Wantland, W.W., "Effects of Various Concentrations of Sodium

Fluoride on Parasitic and Free-living Protozoa and Rotifera," J.

Dental Res., 35:763-772, 1956.

62). Smith, A.O., and B.R. Woodson, "The Effects of Fluoride an the

Growth of Chlorella pyrenoidosa," Virg. J. Sci., 16:1-8, 1965.

63). McKee and Wolf, loc. cit.

64). Rao, K.V., A.K. Khandekar, and D. Vaidyanadham. "Uptake of

Fluoride by Water Hyacinth, Eichhornia crassipes," Indian J. Exper.

Bio., 11:68-69, 1973.

65) Young, G.E., and W.M. Langille. "The Occurrence of Inorganic

Elements in Marine Algae of the Atlantic Provinces of Canada," Can.

J. Bot., 36:301-310, 1958.

66). Hemens, J., and R.J. Warwick, "The Effects of Fluoride on

Estuarine Organisms," Water Research. 6:1301-1308, 1972.

67). Danilova, V.V., "The Geochemistry of Dispersed Fluorine. 11.

Determination of Fluorine in Plants," Trav. Lab. Biogeochim. Acad.

Sci. URSS, 7:83-85, 1944 (English Abstract. Chemical Abstracts,

1947).

183

68). Mun, A.I., Z.A. Bazilevich, and K.P. Budeyeva, "Geochemical

Behavior of Fluorine in the Bottom Sediments of Continental

Basins," Geochem. Internat., 3:698-703, 1966.

69). Sanders, H.O., and O.B. Cope. "Toxicities of Several Pesticides

to Two Species of Cladocerans." Trans. Am. Fish. Soc., 95:165-169,

1966.

70). Stewart, J.E., and J.W. Cornick, "Lobster (Homarus

americanus) Tolerance for TRIS Buffer. Sodium Fluoride, and

Seawater Extracts of Various Woods," J. Fish. Res. Board Can.,

21:1549-1556, 1964.

71). Moore, D.J., "A Field and Laboratory Study of Fluoride Uptake

by Oysters," Report No. 20, Water Resources Research Institute,

University of N.C., Raleigh, N.C.1969. Moore, 1971, loc. cit. Hemens

and Warwick, loc. cit.

72). Moore, 1971, loc. cit. Hemens and Warwick, loc. cit.

73). Neuhold, J.M., and W.F. Sigler, "Effects of Sodium Fluoride on

Carp and Rainbow Trout," Trans. Am. Fish. Soc.. 89:358-370, 1960.

74). Sigler and Neuhold, ibid.

75). Ellis et al., loc. cit.

76). Fisher, F., and M.J. Prival, Total Fluoride Intake, Center for

Science in the Public Interest, Washington, D.C., 1973. Neuhold and

Sigler, loc. cit. Ke, P.J., H.E. Power, and L.W. Regier, "Fluoride

184

Content of Fish Protein Concentrate and Raw Fish," J. Sci. Food

Agric., 2 1 : 108-109. 1970.

77) Simonin and Pierron, loc. cit.

78). Kaplan, H.M., N. Yee, and S. Glaczenski. "Toxicity of Fluorides

for Frogs," Laboratory Animal Care, 14:185-189, 1964.

79). Cameron, J.A., "The Effect of Fluoride on the Hatching Time

and Hatching Stage in Rana pipiens." Ecology, 21:288-292, 1940.

80). Kuusisto and Telkka, ibid.

81). Hadjuk, J., "Extension Growth in Seedlings as a Biological Test

of Soils Contaminated with Fluorine Exhalates," Biologia,

24(10):728-737, 1969. (In German; English abstract in U.S. EPA

Pub No. AP-119, loc. cit.)

82). Davis, J.B., and R.L. Barnes, "Effects of Soil-Applied Fluoride

and Lead on Growth of Loblolly Pine and Red Maple," Environmental

Pollution, 5(1):34-44, 1973.

83). Smith, R.L., Ecology and Field Biology, Harper and Row, N.Y.,

1966.