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pyrig ORIGINALoARTICLE N ot C for Pu bli cat io Natural Fluoride Levels in the Drinking Water,t ess c e n Water Fluoridation and Estimated Risk of Dentale n
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Fluorosis in a Tropical Region of Brazil Fábio Correia Sampaioa*/Fábia Danielle Sales Cunha Medeiros e Silvaa/ Andréa Cristina Barbosa Silvaa/Ana Thereza de Azevedo Brito Machadob/ Demétrius Antônio Machado de Araújoc/Erik Melo de Sousad
Purpose: The aim of the present study was to determine the natural fluoride levels in the drinking water supplies of a tropical area of Brazil to identify the cities at risk of high prevalence of dental fluorosis and to provide data for future water fluoridation projects in the region. Materials and Methods: The present study was carried out in Paraíba, in the north-eastern region of Brazil. A total of 223 cities were selected, and local health workers were instructed to collect three samples of drinking water: one from the main public water supply and the other two from a public or residential tap with the same water source. Fluoride analyses were carried out in duplicate using a fluoride-specific electrode coupled to an ion analyser. Results: A total of 167 cities (75%) provided water samples for analysis. Fluoride levels ranged from 0.1 to 1.0 ppm (mg/l). Samples from most of the cities (n = 163, 73%) presented low levels of fluoride (< 0.5 mg/l). Samples from three cities (a total estimate of 28,222 inhabitants exposed) presented ‘optimum’ fluoride levels (0.6 to 0.8 mg/l). Samples from one city (16,724 inhabitants) with 1.0 mg/l of fluoride in the water were above the recommended level (0.7 mg/l) for the local temperature. Conclusions: It can be concluded that the cities in this area of Brazil presented low natural fluoride levels in the drinking water and could implement controlled water fluoridation projects when technical requirements are accomplished. A high or a moderate prevalence of dental fluorosis due to the intake of natural fluoride in the drinking water is likely to take place in one city only. Key words: Brazil, dental fluorosis, drinking water, fluoride Oral Health Prev Dent 2010; 8: 71–75.
a
Postgraduate Program in Preventive Dentistry and Pedodontics, Federal University of Paraíba, Campus I, Castelo Branco, 58051900, João Pessoa, Brazil.
b
State Health Secretariat of Paraíba, Dom Pedro II Avenue, 1826, 58044-440, João Pessoa, Brazil.
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Department of Molecular Biology, Federal University of Paraíba, Campus I, Castelo Branco, 58051-900, João Pessoa, Brazil.
d
Young Researcher FAPESQ Program, Emiliano Rosendo da Silva Street 58109-772, Campina Grande, Brazil.
Correspondence: Fábio Correia Sampaio, Rua Mário Batista Júnior 75 apto 602, Miramar—J. Pessoa, Paraíba, 58043-130, Brazil. Tel: +5583 3225 5532, +5583 9982 1111. Emails: fabio.sampa@ uol.com.br,
[email protected] *
Present address: Rua Olimpio de Macedo 2-22, Bauru, Sao Paulo, 17012-533 Brazil. Tel: +5514 8148 9982. Fax: +5514 3227 1486.
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Submitted for publication: 10.12.07; accepted for publication: 31.10.08.
ater fluoridation is regarded as one of the most important public health achievements in the last century (Centers for Disease Control and Prevention [CDC], 1999). This method of delivering fluoride is recommended by many international organizations and is regarded as a safe approach to reduce caries prevalence even in the deprived areas of the world (Petersen et al, 2005). On the other hand, the widespread use of other measures of caries prevention in fluoridated and non-fluoridated cities has raised the question: Does water fluoridation not have the same beneficial effect as observed decades ago? However, this observation cannot be extrapolated to countries with less intensive preventive dental care
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(Seppä et al, 2002). The present issue is relevant to some regions of Brazil where the availability of fluoridated dentifrices is rather low, but is gradually increasing, and controlled water fluoridation systems are planned and implemented in the regions where natural fluoride levels in the drinking water are low (Forte et al, 2001; Brasil, 2004a, 2006; Moreira et al, 2007). The prevalence of dental fluorosis in the rural areas of Paraíba, in north-eastern Brazil, is a matter of public health concern due to high natural fluoride levels (1.0 up to 5.8 mg/l) in the drinking water (Sampaio et al, 1999). Similar to other hot semidesert areas, drinking water sources are scarce and are mainly provided by groundwater reservoirs (wells) that can present traces of naturally occurring elements including fluoride (Sampaio and von der Fehr, 2000; Bjorvatn et al, 2003). Three rural areas with endemic dental fluorosis have already been mapped in Paraíba. Following a geological pattern of crystalline soils, the neighbouring states of Rio Grande do Norte and Ceará also identified areas with natural levels of fluoride in the drinking water that can be a risk for dental fluorosis (Chiang et al, 2000; Bleicher and Frota, 2003). These semi-arid regions are periodically affected by drought, with partial or total loss in agriculture, which in turn also affects the water supply to the population (Silva, 2004). Due to the hot climate, the optimum fluoride concentration in the drinking water by which dental caries can be controlled with minimal prevalence of dental fluorosis must be around 0.7 mg/l, with accepted values between 0.6 and 0.8 mg/l (Galagan and Vermillion, 1957; Brasil, 2006). The use of fluoridated dentifrice in this area is less than that in other parts of the country, and the mean decayed, missing and filled teeth (DMFT) index in most cities of Paraíba is > 3.0 for 12-yearold children (Sampaio et al, 2000; Moreira et al, 2007). To control caries prevalence, a recent federal programme named Brasil Sorridente (Smiling Brazil) will implement controlled water fluoridation systems in all of the cities where technical requirements for potable water are accomplished (Brasil, 2006). Safe and stable water supplies in the semi-arid northeastern region are being achieved with the aid of another federal programme putting in place comprehensive water resource management systems (Brasil, 2000). Only two cities of Paraíba have artificial or controlled water fluoridation programmes. In north-eastern Brazil, 16.5% of the cities have water fluoridation, and this is a low percentage compared
pyrig No Co t fo r P (Brasil, to the wealthier areas/regions of the country ub 2006; Peres et al, 2006). lica Brazilian cities with water fluoridation for > 15tion tecaries than years presented around 40% less dental ss e n c e
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similar cities where water fluoridation has never been available (Brasil, 2006). However, prior to implementation of any water fluoridation system, information about the natural fluoride concentration in the drinking water is necessary to avoid any overlap of fluoride sources. The present information is particularly relevant in the tropical areas where natural fluoride levels can be observed and high water consumption is likely to occur (Bjorvatn et al, 2003). However, no data about the levels of fluoride in the water of these Brazilian urban areas are available. The aim of the present study was to determine the natural fluoride levels in the drinking water supplies of the cities located in a hot climate region of Brazil (Paraíba) to identify the areas at risk for high prevalence of dental fluorosis and to provide data for future water fluoridation projects in the region.
MATERIALS AND METHODS Areas under study Paraíba is located in north-eastern Brazil, and it has 223 cities with an estimated population of 2,843,278 inhabitants (Brasil, 2007). The annual average temperature is high (between 29°C and 32°C) in most parts of its territory. The economy of Paraíba is largely dependent on agriculture. However, this area has severe economic restrictions due to long dry periods, and frequent droughts have led to great migrations from the countryside to the cities.
Collection and analysis of water samples Prewashed 50 ml polypropylene recipients were distributed to all cities. In each city, a kit with three recipients was given to local health workers who were previously trained for this task. They were instructed to collect water samples on the same day as follows: one sample from the main public water supply and the other two from a public or a residential tap from the same source. All of the samples were collected from September 2006 until May 2007. All of the procedures were completed in accordance with the Brazilian Regulatory Agency (Brasil, 2004b). The samples were cooled, coded and transported to the laboratory at the Federal University of Paraíba,
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pyr Co etigal No Sampaio t fo rP Table 1 Distribution of cities and number of inhabitants exposed to different fluoride levels in drinking water in Paraíba, ub lica Brazil tio n te Fluoride group (mg/l) Cities (N) Mean (SD) of fluoride levels (mg/l) Range Inhabitants ss e n c e
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< 0.19 0.20–0.39 0.40–0.59 0.60–0.79 > 0.80
122 37 04 03 01
0.10 (0.04) 0.25 (0.04) 0.45 (0.04) 0.60 (0.04) 1.00
0.01–0.19 0.20–0.36 0.41–0.50 0.60–0.62 1.00
2,597,675 483,875 29,620 28,222 16,724
82.3 15.3 0.9 0.9 0.5
Total
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0.16 (0.12)
0.01–1.00
3,156,116
100.0
and analysed using a fluoride-specific electrode (Orion Model 9609, Orion Research, USA) coupled to an ion analyser (Orion Model 710-A, Orion Research). All of the samples were analysed in duplicate using TISAB II as buffer, coded by a third party and analysed in a blind manner. Calibration was frequently carried out with fresh fluoride standards of 1 ml of 0.2 up to 1.6 mg/l. The data in millivolts were converted into micrograms of fluoride and fluoride concentration (mg/l) using Microsoft Windows and Excel. Only calibration curves with variation in percentage up to 5% for all standards and r v 0.99 were accepted. Repeatability was checked in 20% of the samples, and it was > 90%.
Statistical procedures The mean standard deviation (SD) of natural fluoride concentration of the three samples was calculated and categorised into five groups according to the fluoride concentration in mg/l: (i) < 0.19 mg/l (extremely low F concentration); (ii) from 0.20 up to 0.39 mg/l (very low F concentration); (iii) from 0.40 up to 0.59 mg/l (low F concentration); (iv) from 0.60 up to 0.79 mg/l (optimum F concentration); and (v) > 0.80 mg/l (high F concentration).
RESULTS A total of 167 cities had sent water samples for analysis. As a result, the present investigation covers 74.8% of the cities in Paraíba. The data in Table 1 present the mean (SD) of natural water fluoride levels (mg/l), and the distribution of cities and estimates of the exposed population in each water fluoride classifi-
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cation. The samples from the cities of Lastro, Brejo dos Santos and Cuité presented optimum fluoride levels in the drinking water. The samples from Poço Dantas had 1.0 mg/l of fluoride, which is 0.3 mg/l above the recommended level. Figure 1 shows the map of Paraíba and the spatial distribution of the municipalities that were classified according to the natural fluoride concentration in the drinking water. Except for two samples in two cities, there were no significant differences (> 0.1 mg/l) in the fluoride levels among the three samples of each city.
DISCUSSION In the present study, fluctuations in fluoride levels throughout the year were not assessed. However, most of the water sources were wells where a low variation in fluoride levels is expected to take place due to reduced evaporation. Thus, it is unlikely that a large variation in fluoride concentration had occurred throughout the months of the study. In fact, fluctuations in fluoride levels were not significant in wells of the countryside in that area (Sampaio et al, 1999). The rather consistent concentration of fluoride among the three samples is an indication that only one source of water is available in the cities (Buzalaf et al, 2002). The majority of the cities that were surveyed showed a water fluoride level classified as extremely low. This implies that many cities in Paraíba can be included as potential candidates for artificial water fluoridation programmes. A recent study showed that caries prevalence was significantly higher in children from state schools than in children from private schools (Moreira et al, 2007). As most of the children in this area of Brazil are from underprivileged
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Brejo dos Santos 0.6 mg/l Cuité 0.6 mg/l
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Fluoride groups No data < 0.19 N
0.20 - 0.39 0.40 - 0.59 0.60 - 0.79
Paraíba Brazil
0.80
Fig 1 Spatial distribution of municipalities according to natural fluoride levels in the drinking water in Paraíba, Brazil.
groups with high caries activity and who are registered in state schools, the effect on caries prevalence in Paraíba can be higher than in those areas where caries prevalence is already low. So far, only two cities in Paraíba have implemented artificial water fluoridation programmes. Since the programmes started in 2006, it is too early to evaluate any caries reduction associated with water fluoridation. However, as observed in the present study, three cities presented natural fluoride levels in the drinking water that are regarded as optimum for caries control. Caries prevalence in these cities is worth investigating. Not surprisingly, the cities in Paraíba with optimum natural fluoride levels in the drinking water are located close to Rio Grande do Norte (Fig 1). A wide area along the border of these Brazilian states hosts several metallic and non-metallic deposits that include fluorite (Chiang et al, 2000). With regard to the risk of dental fluorosis, only one city may be at risk for the prevalence of dental fluorosis that could raise public health concerns. In the rural areas of Paraíba where similar water fluoride values are found (1.0 mg/l), dental fluorosis affects 31% of permanent resident children (Sampaio et al, 1999). It is important to point out that even though this prevalence percentage can be regarded as high, most cases of dental fluorosis in these areas are not graded as severe, and thus have low aesthetic significance (Forte et al, 2001). 74
One additional source of fluoride for Brazilian children is the ingestion of fluoridated dentifrice (de Almeida et al, 2007). In Paraíba, the availability of fluoridated dentifrice is rather low. The fluoride intake is still mainly by water, but the consumption of fluoridated dentifrice is increasing in some areas (Forte et al, 2001; Moreira et al, 2007). However, the availability and regular use of fluoridated dentifrice in this area can be associated with socioeconomic status (Sampaio et al, 2000). Thus, considering the economic restrictions of the area, water fluoridation can be regarded as the most cost-effective and efficient way of reducing caries prevalence in the near future (Peres et al, 2006). The increase of exposure due to fluoridated dentifrice can raise the risk of dental fluorosis in areas with natural or artificial fluoride in the drinking water. Monitoring the dentifrice availability and use among children is warranted in this area, particularly the 1500 ppm fluoride dentifrice that is the cheapest in the area (Moreira et al, 2007). The cities in the north-eastern region with 0.4 mg/l of fluoride in the drinking water have 20% of children with dental fluorosis, and few cases are severe enough to raise aesthetic concerns (Sampaio et al, 1999). As in many African countries, in the rural tropical regions of Brazil, water is the most important source of fluoride (Bjorvatn et al, 2003; Brasil, 2004a). High intake of fluoride from foodstuffs in Brazil seems to Oral Health & Preventive Dentistry
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1. Bjorvatn K, Reimann C, Østvolt SH, Tekle-Haimanot R, Melaku Z, Siewers U. High-fluoride drinking water. A health problem in the Ethiopian Rift Valley 1. Assessment of lateritic soils as defluoridating agents. Oral Health Prev Dent 2003;2:141–148. 2. Bleicher L, Frota FHS. Panorama da fluoretação da água de abastecimento em municípios cearenses. Rev Aboprev 2003;5:13–21. 3. Brasil. Ministério da Integração Nacional, Ministério do Meio Ambiente, PROÁGUA/Semiárido: Manual Operativo, Vol 1 Brasília, 2000:5–67. 4. Brasil. Ministério da Saúde. Secretaria de atenção à saúde. Departamento de atenção básica. Coordenação nacional de Saúde Bucal. Projeto SB Brasil 2003: condições de saúde bucal da população brasileira no ano 2002–2003. Brasília: Resultados Principais, 2004a:3–51. 5. Brasil, Fundação Nacional de Saúde. Manual de Saneamento. Brasília, 2004b:3–47. 6. Brasil. Fundação Nacional de Saúde. Ministério da Saúde. Programa Brasil Sorridente, a saúde bucal levada a sério— sub-componente fluoretação da água. Manual de Orientações Técnicas. Brasilia, 2006:61.
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The present study was supported by the Brazilian Agency for Scientific and Technological Development (CNPq) and Project Identification Nos. CNPq 403241/2004-9 and FAPESQ-CNPq 003-04-PPP.
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be lower than in Africa. It is associated with processed food and mainly in the urban industrialised areas (de Almeida et al, 2007). As for the tropical regions of Brazil, mapping fluoride in the water is an important step before implementing water fluoridation programmes and estimating the risk of dental fluorosis. In at least four cities of Paraíba, artificial water fluoridation programmes are not necessary. Actually, in one of these cities, a defluoridation method is needed to reduce the risk of dental fluorosis. Finally, water fluoridation programmes can be implemented as a safe procedure in many cities of Paraíba where fluoride levels in the drinking water were below the recommended level for the local temperature.
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