FLUORIDE CONCENTRATIONS IN TABLE SALTS SOLD IN SUPERMARKETS OF BOGOTÁ, COLOMBIA

Abstract

Purpose: To determine the fluoride (F) concentrations in table salts sold in Bogotá, Colombia, as well as to verify whether the values were consistent with the information provided by the manufacturers and with the standards of the national program of domestic salt fluoridation. Materials and methods: Twenty-eight different samples of table salt were purchased in the main supermarkets of Bogotá, comprising coarse, refined, and seasoned salts. Fluoride content was analyzed with an ion-specific fluoride electrode. Results: Mean (SD) F concentration for all samples was 133.8 (51.0) ppm F, ranging from 4.8 to 225.7 ppm F. The majority of samples (71%) had values below those recommended by the national program of salt fluoridation in Colombia. Conclusion: Most of the salts analyzed did not comply with the legislation for salt fluoridation in Colombia. Therefore, monitoring of the fluoride concentrations in salts for human consumption should be performed on a regular basis, so that fluoride levels are kept at safe and effective levels for caries control, without increasing the risk of dental fluorosis.

Headnote

ABSTRACT: Purpose: To determine the fluoride (F) concentrations in table salts sold in Bogotá, Colombia, as well as to verify whether the values were consistent with the information provided by the manufacturers and with the standards of the national program of domestic salt fluoridation. Materials and methods: Twenty-eight different samples of table salt were purchased in the main supermarkets of Bogotá, comprising coarse, refined, and seasoned salts. Fluoride content was analyzed with an ion-specific fluoride electrode. Results: Mean (SD) F concentration for all samples was 133.8 (51.0) ppm F, ranging from 4.8 to 225.7 ppm F. The majority of samples (71%) had values below those recommended by the national program of salt fluoridation in Colombia. Conclusion: Most of the salts analyzed did not comply with the legislation for salt fluoridation in Colombia. Therefore, monitoring of the fluoride concentrations in salts for human consumption should be performed on a regular basis, so that fluoride levels are kept at safe and effective levels for caries control, without increasing the risk of dental fluorosis.

Keywords: Diet; Fluorides; Public health surveillance; Salt fluoridation; Sodium chloride.

INTRODUCTION

Dental caries is a chronic disease, which continues to be a major public health challenge, with the highest prevalence in Asian and Latin American countries The estimated prevalence of untreated caries in permanent teeth worldwide in 2015 was 34.1%, and the most affected age groups with untreated caries are 1-4 and 19 yearolds.1 In this sense, adequate access to fluoridation programs is one of the most costeffective and safe preventive interventions that has been available during the last 60 years for the control of dental caries. However, living conditions, limitations on access to health services, and the existence of adequate legislation for the control of water or salt fluoridation are external factors that affect the prevalence and severity of the disease. The choice of a particular community fluoridation method (water, salt, or milk) depends on the feasibility of implementation in each country.2

The addition of 200-250 ppm fluoride (F) to table salt has contributed significantly to the reduction in the prevalence of caries in 12-year olds, reaching levels of 84% in Jamaica, 73% in Costa Rica, and 40% in Uruguay.3 In Mexico, after nine years of implementation of the national salt fluoridation program, the DMFT index of 12year-old students decreased from 4.4 (1988) to 2.5 (1997), resulting in a 43.7% net reduction.4 On the other hand, the prevalence of dental fluorosis in eight Mexicanborn cohorts during the implementation of the measure increased by about four times compared to the period prior to salt fluoridation.5

In Colombia, three methods of community fluoridation were compared in a clinical trial conducted in four different cities, with a follow-up of 8 years: San Pedro (fluoridated water with NaF at 1.0 ppm F), Armenia (fluoridated salt with NaF at 200 ppm F), Montebello (fluoridated salt with CaF2 200 ppm F) and Don Matias (control group, with no community method of fluoridation). The reduction in the DMFT index achieved in children of 10 and 12 years of age in the three experimental groups was close to 50%, ranging from 47% to 58%, with no statistical differences among them, concluding that salt fluoridation with either NaF or CaF2 has similar preventive effects when compared with water fluoridation.6

One of the disadvantages of the use of fluoridated salt is the control of the F concentration added, given that discrepant values can lead both to an increased risk of chronic toxicity (dental fluorosis) or to a reduction in the protective effect of F in caries control. In this regard, while the physical and chemical properties of fluoridated salt remain fairly unaltered over prolonged periods of storage, large variations have been reported in the F levels within the same trademark, as well as among different brands.7

The national program of fluoridation of table salt was implemented in Colombia in 1989, adopting a range between 180 and 220 ppm F as acceptable values. According to this legislation, the regular monitoring of F concentration in table salts should be performed by governmental authorities.8 A study in four Colombian cities in 2003 reported that 60% of consumption of salt samples had concentrations below 180 ppm F.9 In addition, in Bogotá, the analysis of samples sent to the laboratory of public health between the years 1992 and 2004 showed that 18% of samples did not comply with the legislation.10 The difficulty in controlling the addition of F to salts, added to the economic opening that allowed the commercialization of salts produced in other countries (in which different rules may be applicable), emphasize the need for the monitoring F concentrations in the salts available in the country's markets.

Based on the above, and considering the lack of recent data on the monitoring of F concentrations in salts commercialized in Colombia, the aim of this study was to determine the F concentrations in table salts sold in supermarkets in Bogotá, Colombia, as well as to verify the consistency of those values with the information provided by the manufacturer and with the rules of the national program of fluorination of table salt in the country (180-220 ppm F).

METHODS

Twenty-eight table salts of different brands available in the main markets of the city of Bogotá, Colombia, were acquired during the period from January 2015 to January 2016. Seventeen refined salts were analyzed with an ion-specific electrode by the direct method, after dilution in deionized water. Two refined salts that were not able to be fully diluted in deionized water, and nine salts containing seasonings were analyzed with the same electrode after hexamethyldisiloxane (HMDS)-facilitated diffusion. All analyzes were performed in triplicate. The samples were collected from the original packaging after thorough homogenization of their contents and the samples were taken from the middle portion of each package.

For the direct method, 2 g of each salt were weighed and diluted in 50 mL of deionized water. Following this, the F concentration in the resulting solutions was determined using direct potentiometry. For the HMDS-facilitated diffusion method, the salts were previously ground in a mortar and pestle, and the protocol described by Taves11 and modified by Whitford12 was followed.

Data were submitted to descriptive statistical analysis using the Microsoft Excel 2010 program with calculation of the mean and standard deviation of the triplicates. Only analyzes with reproducibility higher than 90% were accepted.

RESULTS

Twenty-six salts (93%) of the 28 brands analyzed were produced in Colombia, and the remaining products (7%), in Peru. Regarding packaging, 43% of the salts did not present the F concentration in the product label. Among the products with such a description, only one brand described values lower (175 ppm F) and higher (225 ppm F) than those set as the acceptable range by the national program for salt fluoridation in Colombia (180-220 ppm F), as described in Table 1. All the salts presented a batch number and a registered health record. Eight refined salts from different trademarks had the same health record. The same trend was observed for two salts containing seasonings. Four companies produced the 28 different brands evaluated in this study.

The mean (SD) F concentration of the 28 salts was 133.8 (51.0) ppm F, ranging from 4.8 to 225.7 ppm F. Twenty salts (71%) presented F levels below 180 ppm F, and one salt presented a F concentration slightly above the maximum value allowed (Tables 1 and 2). Considering only the refined salts (n = 19), the mean (SD) F concentration was 155.6 (37.3) ppm F, ranging from 91.7 to 225.7 ppm F. Of these, 11 salts (58%) had F levels below the minimum allowed, and five salts (26%) presented F concentrations 50% lower than the minimum allowed (Table 1).

Regarding the nine salts with seasonings, mean (SD) fluoride concentrations was 87.8 (45.2), ranging from 4.8 to 163.5 ppm F. No brand displayed the F concentration in their packages. All brands were produced in Colombia and the F levels observed were lower than the minimum established by the legislation (Table 2).

The results of the present study showed that most of the salts analyzed did not meet the legal requirements concerning the F concentration allowed (180-220 ppm F) for table salt consumed in Colombia.8 Although the packaging should inform the F concentration in the product according to this legislation,13 all salts with seasonings and three brands of refined salts did not present this information. It is noteworthy, however, that the legislation only applies to refined salts. Twenty salts (71% of the samples) showed values below those recommended, and an even greater variation in F concentrations of salts with seasonings was observed. These data reinforce the need for a periodic control of the F content in salts for human consumption, given that lower levels than those recommended may reduce the effectiveness of this measure in controlling dental caries, while higher values may increase the risk for development of dental fluorosis.

Despite the inconsistencies in the F concentrations in table salts from the beginning of the program of fluoridation of table salt in Colombia, the DMFT index dramatically reduced from 4.7 (in 1980) to 2.3 (in 1998),2 which further decreased to 1.5 (in 2014) at the age of 12 years. On the other hand, for the same year 2014, according to the Dean's Community Index of fluorosis, the data for the ages of 12 and 15 years old were classified as a "mild public health problem."14 The fluoridation programs should evaluate the rates of caries reduction and the degree of dental fluorosis within each community in order to establish a controlled and rational exposure to fluorides. In addition, there also is requirement for adequate and effective control measures for suppliers and manufacturers.

CONCLUSIONS

Most of the salts analyzed do not comply with the legislation of salt fluoridation in Colombia. Therefore, the monitoring of F levels in salts for human consumption must be carried out on a regular basis to ensure the maintenance of safe and effective levels of F for caries control, without increasing the risk of dental fluorosis. In addition, the inclusion of salts with a low-sodium content and seasoned salts in the Colombian market reinforce the need for updating the existing regulation of the national program for salt fluoridation in Colombia. Furthermore, the reduction of caries prevalence and the increase in the prevalence of dental fluorosis in Colombia, associated with irregularities in the concentration of F in table salts in the country, suggest the need for clinical and metabolic studies in order to determine the optimal concentration to be added to table salt, especially considering the overlapping sources of exposure to F.

References

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