The occurrence of fluoride in South African groundwater : A water quality and health problem

Groundwater is the most appropriate and widely used source of drinking water for many rural communities in South Africa. Pilot studies and surveys conducted by the Department of Water Affairs and Forestry (DWAF) indicated that there are a number of boreholes across the country that contain apart from fluoride, levels of nitrate, some heavy metals, total dissolved solids, sulphates and faecal coliforms (in some regions) that could pose a health risk if the water is used for drinking purposes. Very few boreholes have been tested for heavy metals or toxic organic substances. However, considering the levels of fluoride, in general, groundwater is of acceptable quality except for some areas in which elevated levels of natural groundwater fluoride occur. The study on which this paper is based was conducted to identify areas of high groundwater fluoride concentration in South Africa and to relate this to the occurrence of dental fluorosis in most communities using the groundwater for domestic use. Two sets of data were used. The fluoride data were obtained by extracting fluoride groundwater quality data from DWAF’s Water Management Systems (WMS) database. STATISTICA and ARCVIEW were used to process the data. The dental fluorosis data were obtained from a field study conducted by the Department of Health. The degree of dental fluorosis was determined using Dean’s classification criteria for dental fluorosis. The occurrence of dental fluorosis was observed in those areas in which fluoride levels were higher than the recommended guidelines for drinking water. The degree and severity of mottling in the subjects studied by the DOH team, corresponded with the level of fluoride in drinking water and the percentage morbidity of dental fluorosis varied from province to province, district to district and village to village.


Introduction
The beneficial attributes of fluorides to human health have been known for many years (WHO, 1970).When ingested at specific doses, the fluoride ion is beneficial to both bone and dental development in human beings.At correct intake levels it plays a very important role in the formation of teeth (Pontius, 1991).Too low fluoride intake levels during childhood may give rise to the occurrence of preventable dental caries in later years.Dental caries is a disease caused by specific bacteria harboured in dental plaque, fermenting carbohydrates to produce acids that can demineralise tooth enamel (Hammer, 1986).If this demineralization is allowed to continue, the enamel is penetrated permitting bacterial invasion and eventual loss of the tooth by decay in the absence of restorative dental care.
Too high fluoride intake normally gives rise to teeth mottling (dental fluorosis) and related problems.Chronic endemic fluorosis is a condition which is caused by an excess of fluorides in drinking water and which affects the calcification of the teeth, resulting in what is commonly known as dental fluorosis.Maughan-Brown in 1935 andRaubenheimer in 1938 first reported a study of the occurrence of mottled enamel in South Africa (WRC, 2001).In 1941, Ockerse produced three reports on human fluorosis in various regions of the former Union of South Africa.At that time 805 areas in which dental fluorosis occurred were known (Ockerse, 1947).The majority of dental fluorosis sufferers (mainly blacks) in South Africa live in rural areas.Different studies have shown that the occurrence of dental fluorosis in the majority of cases in South Africa are related to the fluoride content of groundwater used for drinking purposes (McCaffrey 1993;Fayazi, 1994;Du Plessis, 1995;WRC, 2001).
The issue of whether and at what levels of concentration, to manage the fluoride ion concentrations in South Africa's public water supplies is a contentious one.While the Department of Water Affairs and Forestry (DWAF), as the custodian of the country 's water resources, manages the fluoride levels through the criteria set in its guidelines, (DWAF, 1996) and the South African Bureau of Standards (SABS) determines the specifications (SABS, 2001), the Department of Health proposes compulsory fluoridation of public water supplies (Anon, 1998).Similarly, the awareness of excess fluoride consumption through water has been increasing countrywide.(McCaffrey, 1993;Fayazi, 1994;Rudolph et al., 1995;Du Plessis, 1995;WRC, 2001).
One of the main issues is the lack of adequate information on the environmental and health impacts of fluoride locally.Most of the information is highly technical for the local people and no proper interventions have been made to increase awareness.Most of the environmental issues are addressed in a recent Water Research Commission report (WRC, 2004).There is also a lack of accurate information in a user-friendly format about the current status of fluoride in the country's groundwater resources.This paper addresses these gaps by assessing the groundwater fluoride data from the Water Management System Database housed at DWAF's Resource Quality Services Directorate, for the period 1996 to 2000 in order to establish the current occurrence of fluoride ion concentration levels in groundwater sources and the impact of dietary fluoride (from groundwater consumption) on dental health.As

Approach
The fluoride data were extracted from DWAF's Water Management System (WMS) Database housed at the Resource Quality Services (RQS) directorate of DWAF.This constituted 14 509 groundwater samples, including boreholes and springs.The data were screened for errors, incorrect reference codes, incorrect co-ordinates and number of fluoride ion concentrations reported for the station.A statistical package, STATISTICA, was used to calculate a fluoride median value for each unique groundwater source.This resulted in a summarised data set comprising 6 042 values.Plotting these data on a map assessed the current status of fluoride ion distribution in the country (Fig. 1).This map was plotted using ARCVIEW and the available fluoride water quality data.
The dental fluorosis data were obtained from the National Department of Health (NDOH).These data were processed according to Wang et al. (1999), Table 1, in order to obtain the % morbidity of dental fluorosis.The results for the selected provinces are as shown in Tables 2, 3, 4 and 5.The results are based on the degree of mottling of the teeth as observed during the dental examinations.A comparison was made between the % morbidity of dental fluorosis and the drinking water quality in selected provinces.The results are shown in Figs. 2 to 5.

Results and discussion
The current status of fluoride ion distribution in South African groundwater is provided in Fig. 1.The figure shows that the problems of high fluoride ion concentrations are currently concentrated in the Limpopo, Northern Cape, North-West and Kwa-Zulu-Natal Provinces.These provinces have a high population still living in rural areas and prior to 1994 most of them used ground-and surface water for drinking purposes.A few cases were recorded in other parts of the country.The current situation of the fluoride distribution in the country is such that no clear demarcation can be made of areas deficient in fluoride since some areas have groundwater sources in which the fluoride ion concentrations are higher than the recommended limits for drinking water.This is an indication that the occurrence of low fluoride ion concentrations in groundwater is currently not a national problem.Many sources in the Limpopo, North-West, Northern Cape, Western Cape and KwaZulu-Natal Provinces are in need of partial defluoridation to the optimum level of fluoride concentration safe for drinking water purposes.This must receive serious consideration if the water from those sources is being used for drinking purposes.
The results of the general investigations of fluorosis obtained by the data from the DOH are as presented in Tables 2, 3, 4 and 5.The criteria used to interpret the results are as presented in Table 1.adopted from Wang et al. (1999).The information on the depend-ency of communities on groundwater for use as drinking water is presented in Table 6.This was obtained from DWAF.This information was obtained in order to confirm the link between high fluoride levels in groundwater, the consumption of this fluoride contaminated water and the occurrence of dental fluorosis in the same areas.It should be noted that in a province where the ISSN 0378-4738 = Water SA Vol. 31 No. 1 January 2005 3 9 Available on website http://www.wrc.org.zacommunities depend largely on groundwater for drinking water purposes like the North-West Province, the morbidity of dental fluorosis is high.However, it should be noted that due to the migratory nature of the South African population post-1994 some provinces like the Western Cape might show inconsistent results although it was confirmed that the Mitchell's Plain data are mostly for private boreholes.These boreholes might not necessarily be used for drinking water purposes but for other domestic uses such as general cleaning and irrigation purposes.
The distribution of dental fluorosis in selected provinces is shown in Figs. 2, 3, 4 and 5.The maps show the spatial distribution of the current % morbidity of dental fluorosis for the Western Cape, North-West and KwaZulu-Natal Provinces.The fluoride data are overlain on each provincial map in order to correlate the level of the morbidity of dental fluorosis and fluoride levels in drinking water.It should be noted that differences exist in the morbidity of dental fluorosis among the areas investigated and this is true for the fluoride levels in groundwater sources.It was difficult to present the Free State Province data using the same format as the dental fluorosis data were reported in regions whose digital data were not available at the time of writing this paper.
From the results, a percentage morbidity of dental fluorosis as high as 97% was recorded in the North-West Province.In comparing the distribution of the % morbidity of fluorosis with that of fluoride concentration in groundwater sources (Figs. 1 to 3), it is apparent that high morbidity of fluorosis is observed in areas where fluoride concentrations are extremely high and in most cases exceeding the

Conclusions
Areas with high fluoride ion concentrations in their groundwater supplies and high percentage morbidity of dental fluorosis have been confirmed.Many of these sources require partial de-fluoridation if they are currently being used for drinking water purposes or the development of alternative water supplies as a matter of urgency.Proper research must be initiated into investigating cheap and technologically simple processes for small-scale removal of fluoride from fluoride-rich groundwater or developing alternative methods of supply in areas where there is such a problem especially in rural areas.The authors are aware of the techniques developed in other countries but South Africans need to develop techniques suitable for their local conditions and affordable by the lay person in the rural communities.
Since the occurrence of low fluoride ion concentrations in groundwater is not a national problem, fluoridation of groundwater is not advisable.Alternatives to water fluoridation should be looked into for such areas.These could include salt fluoridation, milk fluoridation, or the use of fluoride supplements such as fluoride drops or tablets or fluoridated vitamins.However, before these methods can be implemented much research needs to be carried out to test their relevance and feasibility in the South African context.