Dietary intake of fluoride is believed to be largely derived from drinking water. In Malta, tap water presently contains less fluoride than is found in naturally occurring ground water obtained from aquifers. Over 55% of water production comes from reverse osmosis and such water is practically fluoride-free. Before the introduction of reverse osmosis water into the water budget, fluoride levels measured from 10 different tap waters averaged 0.51 ppm F-. Now, fluoride content measured from 19 tap water sources averaged 0.21 ppm F- and more than a third of these sources are practically fluoride-free. The incidence of dental caries in Malta has so far been low according to the international standards. We suggest that the lowering of the fluoride level in the water supplies may favour an escalation in the incidence of tooth decay in the future.peer-reviewe

Borg, Vincent

Vella, Alfred J.

English

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Maltese Medical Journal 14 Volume I Issue III 1989 CHANGE IN FLUORIDE CONTENT OF MALTESE TAPWATERS: IMPLICATIONS FOR ORAL HEALTH ABSTRACT Dietary intake of f1uoride is believed to be largely derived from drinking water. In Malta, tapwater presently contains less f1uoride than is found in naturally occur­ring ground water obtained from aquifers. Over 55% of water production comes from reverse osmosis and such water is practi­cally f1uoride-free. Before the introduction of reverse osmosis water into the water budget, f1uoride levels measured from 10 different tapwaters averaged 0.51 ppm F-. Now, f1uoride contents measured from 19 tapwater sources average 0.21 ppm F- and more than a third of these sources are prac­tically f1uoride-free. The incidence of den­tal caries in Malta has so far been low according to international standards. We suggest that the lowering of the fluoride level in the water supplies may favour an escalation in the incidence of tooth decay in future. INTRODUCTION Many substances when absorbed by living organisms in very small amounts may be essential to life while exposure to larger doses may evoke severe signs of intoxica­tion. The element f1uorine falls in such a category of essential trace elements. In adults a minimum of0.5 mg/dayis required for survival, the optimum range being from 2 to 10 mg/day. An intake of 10 to 20 mg/day however results in toxicity and doses higher than this may even be lethal (1). Although some fish may contain as much as 100 mg/ kg of f1uorine and tea may even have twice this concentration, most foods usually con­tain very little f1uorine, typically less than 10 mg/kg (2). The total intake of the sub­stance is thus normally considered to be derived from drinking water. Water con­taini ng 1.0 ppm fluoride is regarded as a "high f1uoride" water. This concentration off1uoride is believed to prevent dental car­ies without havingharmful effects on health en At concentrations of 2 ppm or higher, f1uorine in drinking wateris known to have deleterious effects on health. Chronic dental f1uorosis (mottled enamel) appears when Alfred J. Vella & Vincent Borg waters containing 2 ppm or more are in­gested during the first eight years of life. Ingestion of waters containing fluorine at concentrations higher than 8 ppm may lead to a symptomatic osteosclerosis. Crip­pi ing fluorosis may appear in rare instances of excessive industrial exposure to fluo­rides or where natural waters contain very high fluoride concentrations (4). Fluorine, as the fluoride ion F-, is found in both surface water and ground waters. The natural concentration of the element in ground water depends on such factors as the geological, physical and chemical char­acteristics of the water-supplying area, the consistency of the topsoil, the porosity and permeability of the aquifer rocks and the pH and temperature ofthe water. In Malta, only about 38% of water production is pres­ently obtained from ground water aquifers. A very small amount of the water demand, less than 1%, is occasionally obtained from surface water which is collected and treated in four water treatment plants. Four dis­tillers at the Marsa power station produce about 6% of daily requirements. Over 55% of drinking water is generated from sea waterby three reverse osmosis plants which between them produce about 30 million litres of water per day. Most of these primary production sources supply water directly to a complex system of reservoirs connected by a network of conduits and from these reservoirs the water is redis­tributed to towns and villages. Some loca­tions may also actually receive water di­rectly from primary sources such as bore­holes or reverse osmosis plants. Hence, variations or trends in the fluoride concentrations of local domestic tapwaters have to be seen in this perspective of a system of water sources that is both com­plex and variable in time. METHODS In this work we analysed a number of waters for their fluoride content. The samples were collected over a short period during December 1987 and January 1988 and analysed shortly afterwards. These waters were chosen from different sources, namely, primary production points (bore­holes, pumping stations, springs, purifica­tion plants), storage points (reservoirs, blending rooms) and domestic supplies from various towns and villages. Sea water from a point about 1 km offshore Valletta was also analysed. The chloride content and total hardness for all the samples were also determined. Besides these samples, other waters were analysed as follows: rain wa­ter; bottled "mineral water" both of local origin and imported. Standard methods ofanalysis were adopted for all the parameters measured. Fluoride was measured by the Megregian-Maier technique which is based on the reaction between fluoride ions and a zirconium-al­izarin monosulphonate lake. Standards in the range 0.00 to 2.00 ppm F- were run with the samples and the absorbance of the dye lake was measured at 530 nm using a double beam ShimadzulBausch and 1.0mb Spectronic 210UV spectrophotometer. Deionised water was used in the reference cell and as solvent for all the standards. Waters containing more than 800 ppm chloride were diluted before analysis for fluorine in order to eliminate analytical interferences. Total hardness, defined as the sum of the calcium and magnesium concentrations and expressed as CaC03 equivalent in ppm, was determined by complexometric titration. Chloride con­tent was determined by argentometric ti­tration. Alfred J. Vella B.Sc., M.Sc., Ph.D. (Colorado) Department of Chemistry, Faculty of Science, University of Malta. Vincent Borg Dip. Env. Se., Faculty of Dental Surgery, University of Malta. Maltese Medical Journal 16 Volume I Issue III 1989 Table 1 TABLE 1: ANALYSIS OF WATERS DERIVED FROM DIFFERENT SOURCES Production Pointa Depth/m Aquifer Rockb Formation F Total ppm Hardness Cl ppm ppm Wied Bordi BH 118 LCL 0.21 260 180 Tal-Hlas PS 33 GL 0.22 560 960 Tat-Torba BH 110 GL 0.30 340 340 Ta' Qali PS 110 GL 0.40 980 2200 Naxxar Res.BH 122 LCL 0.48 760 1600 Hal Mann BH 96 GL 0.50 240 140 Ta' Bakkja PS 110 GL 0.72 580 1020 Ta' Qali 11 BH 132 GL 0.75 320 220 Gozo Pipeline 0.69 320 380 Torri Cumbo WTP 1. 00 500 340- RO Plant,Lapsi ndc 80 380 RO Plant,Tigne nd 50 280 RO Marsa,Marsa nd 50 340 Dist.£l,PWRS nd nd nd Di::.t.£4,PWRS nd nd nd a BH ; borehole; PS ; pumping station; PWRS ; power station; WTP ; water treatment plant (surficial water). b LCL ; Lower Coralline Limestone; GL = Globigerina Limestone c nd ; not detected; detection limit for fluoride; 0.02 ppm F Table 2 TABLE 2 ANALYSES Storage Reservoir Ta' Qali Res. Luqa Res. Blending Rm PWRS Wier Rm Ta' QaliMercieca Res. St Maria Res. Sea water Table 3 OF WATERS DERIVED FROM DIFFERENT RESERVOIRS F ppm 0.48 0.17 0.15 0.54 0.48 0.38 1. 37 Total Hardness ppm 500 400 160 440 420 460 6600 Cl ppm 940 1040 410 920 1060 960 21600 TABLE 3 FLUORIDE CONTENT (PPH) OF DOHESTIC TAPWATER IN DIFFERENT AREAS Dec 1983a May 1984a Jan 1988b Floriana 0.30 Valletta 0.30 SI iema 0.70 st Paul's Bay 0.60 Me llieha 0.65 Rabat 1. 00 Dingli 0.45 Zurrieq 0.30 Qrendi 0.20 Hqabba 0.10 LuqaPaola ZejtunHarsascala GhaxaqBirkirkara LaqxijaIklin Gzira Ghajn Tuffieha a Data taken from Holler ( 5) b This work 0.40 0.30 0.60 0.30 0.60 nd 0.60 0.30 0.60 0.31 0.80 0.48 0.54 0.40 nd 0.40 nd 0.60 nd nd nd 0.22 nd 0.38 0.26 0.26 0.26 0.33 RESULTS Table 1 presents the fluoride concentra­tions found in waters produced from the various primary sources. The table also includes total hardness and chloride con­centrations of these waters. Table 2 shows similar data for waters sampled from storage or blending reser­voirs as well as data on the sea water sample analysed. Table 3 gives the fluoride concentrations in several domestic tapwatersobtained from different localities and compares them with earlier published results. Two samples of rain water collected tram Santa Venera during a rain storm in November 1987 were found to contain an average fluoride con­tent of 0.16 ppm and a chloride content of20 ppm. Four brands of imported bottled "mineral water" and two locally produced brands were analysed. The imported wa­ters contained respectively 0.40 ppm F (one brand) and 0.10 ppm F (the other three). One local brand contained 0.10 ppmF while the fluoride content of the other product was below our detection limit which we estimate to be 0.02 ppm F. DISCUSSION In Malta, ground water is produced from two main aquifers namely, the Perched Water Table (Upper Water Table) and the Main Sea Level Water Table (Lower Water Table). Rain water percolating down through the Upper Coralline Limestone and Greensand Formations is trapped by the impervious Blue Clay stratum and it then spreads out and collects as the upper table. The lower water table is formed by similar infiltration of rain water through exposed older formations (the Globigerina and Lower Coralline Limestone) and exists in a lenticular form floating on denser underlying salt water. Faults and fissures serve to connect these water tables in vari­ous places. The ground water samples analysed in this work were obtained from a series of bore­holes and pumping stations (water galler­ies) located on a north-south trend extend­ing from Naxxar to Siggiewi and exclu­sively tapping the Sea Level Water Table. Insofar as these samples accurately de­scribe the quality ofthe water in this major aquifer, we can see that ground water from this source contains fluorine in concentra­tions which vary from about 0.2 to 0.8 ppm. This variation in values reflects such fac­tors as (i) local differences in the concentra­tion offluorine-bearing minerals in the lime­stones; (ii) different residence times of the waters in the aquifer and (iii) mixing of different waters within the aquifer through joints and fissures in the rock. No doubt, a fraction of the fluorine in ground water --------Maltese Medical Journal 17 Volume I Issue III 1989 originates from sea water which intrudes into the water table and mixes with the fresh water by diffusion. However, using the chloride concentrations in the ground water samples as an indica­tor of the extent of sea water admixture, it can easily be shown that more than 99% of the fluorine in all the samples examined must originate from the rock matrix itself. It is likely that detrital minerals such as the fluoroapatites, ubiquitous in marine sedimentary rocks, are the major contribu­tors of fluorine to Malta's ground water. No attempt, however, was made to identify the presence of fluorine-bearing minerals in local limestones. At this point we refer to the fluorine content of the rain water samples examined. Here again, in view of the chloride content of the rain water, we calculate that only 0.8% of the fluorine in this water could have origi­nated from sea spray contamination. We speculate that the major source of fluorine in rain water is airborne pollutants proba­bly originating from coal firing at the Marsa power plant. This is supported by the ob­servation of fine black particles (of soot?) found present in the rain water collected. A working definition of tapwater is any natural or artificially produced water or mixture of waters which is certified as po­table by the water authority and which is supplied to users by means of a mains sys­tem. Tapwater samples were collected from four series oflocalities which were each fed from an independent reservoir, the latter being the Santa Maria reservoir at Ta' Qali and the Naxxar, Qrendi and Fiddien reser­voirs, respectively. As Table 3 shows, the levels of fluoride ions in all tapwaters ana­lysed ranged from less than 0.02 ppm, our limit of detection, to 0.54 ppm with a mean value of0.21 ppm F. These fluoride concen­trations are, in general, quite lower than those found naturally in ground waters produced from boreholes or water galleries. Furthermore, the mean value of fluoride concentrations measured in tapwaters duringDecember 1983 andMay 1984, taken together, is 0.51 ppm F. Thus, on average, tap water fluoride concentrations produced at the beginning of 1988 were smaller by a factor ofabout 59% from their values in late 1983/early 1984. Moreover, for a number of localities, e.g. Sliema, Qrendi and Zurrieq, the fluoride water content is now practi­cally negligible. This substantial reduction in fluoride con­centration in drinking water is a direct consequence of the production of nearly fluoride-free reverse osmosis water which was introduced in 1984. At present, three such plants are in operation and a fourth one, at Cirkewwa, has recently been com­pleted. Hence, the present contribution of reverse osmosis water to the total water budget of these islands is destined to in­crease even further. Other factors which may lead to a reduction in the share which ground waters make towards the total watel' budget are (i) an increase in salinity of the ground water due to sea water intru­sion: already the chlorides from most pro­ducing points are quite high in concentra­tion and (ii) an increase in nitrate (or pesti­cide or herbicide residue) concentration due to aquifer contamination from agricultural irrigation waters. According to published trade statistics, the consumption ofbottled "mineral water" may be substantial. However this water ap­pears to have little potential of increasing total dietary fluoride intake since most of the brands examined were quite low in fluoride. Fluoride levels in most local drinking wa­ters may drop to concentrations which could be insufficient for maintaining oral health. It appears from this work that already a number of domestic water supplies may have an extremely low fluoride content. Such a situation if sustained or further worsened by a continued fall in fluoride levels, will presumably have a negative effect on oral health which may manifest itselfin the near future. Past epidemiologi­cal studies (6 - 8) have indicated that the severity of dental caries in the permanent dentition in Malta ranked at a low level according to international standards. Ifthe fluoride contribution of drinking water to the total fluorine requirement is indeed dominant, as currently believed, then such a situation in the state of oral health with respect to dental caries may well change for the worse. ACKNOWLEDGEMENTS The authors thank the staff at the Water Works Department for their collaboration. The authors also thank Profs. H. Galea, G.E. Camilleri and P.J. Schembri for con­structive reviews of this manuscript. This paper is based on project work which one of the authors (VB) undertook in partial fulfil­ment of the requirements of the Diploma in Environmental Science (Evening Course) at the University of Malta. REFERENCES 1 	 Frieden E. (cd): Biochemistry of the Essential mtratrace Elements, New York, Plenum Press 1984, pp 1-15. 2 	 World Health Organization: Guidelines for Drinking-Water Quality, Volume 2, Health Criteria and Other Supporting Information, World Health Organiza­tion, Geneva, 1984, p. 101. 3 	 Jenkins G.N.: The Effects ofTrace Ele­ments on the Calcified Tissues, in Co­hen Band Kramer mH (eds): Scientific Foundation of Dentistry, London, W. Heinemann Medical Books Ltd., 1976, pp.376-382. 4 	 World Health Organization: Technical Report Series No. 146, Expert Commit­tee on Water Fluoridation, Geneva, 1958, pp.9-16. 5 	 Moller I.J.: Oral Heal th in Malta, Report on a Visit to Malta 16-19 December 1987, Copenhagen, W.H.O. Regional Office for Europe, 1987, p.26. 6 	 Moller I.J.: Oral Health Situation and PlanningofNational Oral Health Path­finder Survey, Copenhagen, W.H.O.Re­gional Office for Europe, 1985, p.2. 7 	 Galea H.: The dental health of seven year old children in Malta's state-run primary schools. St. Luke's Hospital Gazette 1971; 6: 126 - 133. 8 	 Olivieri-Monroe C.: A study of the oral health of Maltese school children. Br Dent J. 1968; 124: 177 - 182. ""w;-n'f:AL U'n~ ,~. : :'-' '1 :,? ). ;~ ,~ ,' t ,. h {. i,j, ..;~' ,:r: . ! MA ",',! ' The copyright of this article belongs to the Editorial Board of the Malta Medical Journal. The Malta Medical Journal’s rights in respect of this work are as defined by the Copyright Act (Chapter 415) of the Laws of Malta or as modified by any successive legislation. Users may access this full-text article and can make use of the information contained in accordance with the Copyright Act provided that the author must be properly acknowledged.  Further distribution or reproduction in any format is prohibited without the prior permission of the copyright holder. This article has been reproduced with the authorization of the editor of the Malta Medical Journal (Ref. No 000001)  

(cd): Biochemistry of the Essential mtratrace Elements,

A study of the oral health of Maltese school children. Br Dent J.

Oral Heal th in Malta, Report on a Visit to

Oral Health Situation and PlanningofNational Oral Health Path finder Survey, Copenhagen, W.H.O.Re gional Office for Europe,

Organization:

Organization: Guidelines for Drinking-Water Quality, Volume 2, Health Criteria and Other Supporting Information, World Health Organiza tion,

Regional Office for Europe,

The dental health of seven year old children in Malta's state-run primary schools.

The Effects ofTrace Ele ments on the Calcified Tissues,

Change in fluoride content of Maltese tapwaters : implications for oral health

https://www.um.edu.mt/library/oar/bitstream/handle/123456789/602/mmj010314.pdf?sequence=1&isAllowed=y

Change in fluoride content of Maltese tapwaters : implications for oral health

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