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Potentiometric Analysis of Fluoride in Commonly Consumed Beverages: Method Development, Evaluation and risk Assessment.
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Journal of Food Composition and Analysis
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Amorello D, Barreca S, Pensato F, Orecchio S.
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106836.
Abstract
Highlights
- Electrochemical method development.
- Fluoride levels in food.
- Beverage analyses and risk assessment.
In this research paper, a potentiometric analytical method for the determination of Fluoride was developed and applied to analyse the most commonly consumed beverages. Considering all the beverages studied, the fluoride levels ranged from the detection limit (0.02 mg L-1) to 3.5 mg L-1, measured in tea samples obtained from an automatic dispenser. In conclusion, the investigated beverages do not pose a problem for humans if they are consumed in moderation. For coffees, barley-based drinks, infusions, chamomiles, herbal teas and teas, which are commonly prepared with tap or bottled water, the fluoride content of the water should also be added to the results obtained to assess the real contribution. The only drink potentially causing a risk, especially for children, could be tea prepared by infusing the leaves contained in paper filters because it contributes significantly to the daily dose of fluoride. This dose would increase if the fluoride contribution from water were taken into account.
FULL-TEXT STUDY ONLINE AT https://www.sciencedirect.com/science/article/pii/S0889157524008706
Excerpts:
… Fluoride inhibits bacterial metabolism and forms fluorapatite resulting in increased structural stability. However, excessive intake, especially if prolonged over time, can show several negative effects. Fluoride accumulates in teeth and bones, especially during growth, causing a pathological condition known as fluorosis. Since the beneficial properties or adverse effects depend on the dose and time of exposure, it is important to identify and evaluate all potential sources of fluoride in order to maximize the anti-caries effect and minimize the fluorosis risk. The first reports of fluorosis date back to 1888 when a family from Durango (Mexico) was described as having black teeth, subsequently, in 1891, enamel erosion was described in residents of Naples (Fawell et al., 2006). In detail, during the early 1900s, it was observed that Italian immigrants from cities near Naples, developed brown spots on their teeth directly related to the fluoride content in drinking water. Subsequently, it was recognized that the intake of fluoride in optimal quantities provides protection against the development of dental caries without having any negative effect on the colour of the teeth. Considering what has been observed, since 1945 in the United States experiments of collective prophylaxis have begun through artificial fluoridation of drinking waters of some cities, in which NaF was added in quantities to have a protective effect against tooth decay, without being harmful to health. Most Western European countries did not follow the American example, while other countries discontinued this practice during the late twentieth century (Ozsvath, 2008). It has been estimated that children and some adults ingest between 0.016 to 0.15 mg of fluoride via the toothpaste for every cleaning procedure. Toothpaste, therefore, can account for up to 25% of the total fluoride dose for children aged between 2 and 6 years, depending on the amount of toothpaste ingested while cleaning teeth (Guth et al., 2020). Currently, drinking water is the main source of fluoride intake, therefore, the World Health Organization (WHO) has established that the concentration of this element, for it to play a fundamental role in the prevention and maintenance of tooth and bone health, must be in the range 0.5-1.5 mg L-1. It is estimated, however, that more than 200 million people, living in around 20 countries, consume drinking water with fluoride concentration higher than the levels established by the WHO. Although drinking water is the main source of F– intake in humans, food and drink are also potential pathways exposure (Karami et al., 2019). Table 1, Table 2 show the concentrations of fluoride in several foods and drinks, respectively (Fawell et al., 2006, Cantoral et al., 2019).
Table 1. – Fluoride concentration (mg kg-1) in some foods.
Sample | [F—] | Reference | Sample | [F—] | Reference |
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Vegetable and fruit | 0.1-0.4 | Fawell et al., 2006 | Lemon | 0.009 | Cantoral et al., 2019 |
Barley, rice, potatoes | 2.0 | Fawell et al., 2006 | Fast food | 1.2 | Cantoral et al., 2019 |
Meat e poultry | 0.01-1.70 | Fawell et al., 2006 | Jelly | 3.7 | Cantoral et al., 2019 |
Fish | 0.06-4.57 | Fawell et al., 2006 | Pre-cooked rice | 4.3 | Cantoral et al., 2019 |
Oil and fat | 0.05-0.13 | Fawell et al., 2006 | Whole grain bread | 5.9 | Cantoral et al., 2019 |
Breast milk | 0.005-0.010 | Fawell et al., 2006 | Seafood | 1.9 | Cantoral et al., 2019 |
Lard | 0.003 | Cantoral et al., 2019 | Oysters | 14.7 | Cantoral et al., 2019 |
Papaya | 0.007 | Cantoral et al., 2019 | Fried/oven pork rinds | 14.7 | Cantoral et al., 2019 |
Table 2. – Fluoride concentration (mg L-1) in some beverages.
Sample | [F—] | Reference | Sample | [F—] | Reference |
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Coffee 1 | 0.10-0.58 | Satou et al., 2021 | Beer 1 | 0.05-0.10 | Satou et al., 2021 |
Coffee 2 | 0.03-0.15 | Satou et al., 2021 | Beer 2 | 0.08-0.88 | Jaudenes et al., 2018 |
Soluble coffee | 0.15-0.56 | Satou et al., 2021 | Beer 3 | 0.06-0.66 | Jaudenes et al., 2018 |
Alcohol 1 | 0.06-0.09 | Satou et al., 2021 | Beer 4 | 0.36-0.89 | Jaudenes et al., 2018 |
Alcohol 2 | 0.01-2.15 | Satou et al., 2021 | Beer 5 | 0.07-0.80 | Jaudenes et al., 2018 |
Infuses | 0.07-0.17 | Satou et al., 2021 | Beer 6 | 0.28-1.66 | Jaudenes et al., 2018 |
Beer 7 | 0.63-0.71 | Jaudenes et al., 2018 | Green tea | 0.26-0.41 | Liu et al., 2017 |
Beer 8 | 0.32-0.77 | Jaudenes et al., 2018 | Herbal teas | 0.02-0.40 | Liu et al., 2017 |
Tea | 1.06-6.68 | Satou et al., 2021 | Fruit juice | 0.02-0.04 | Liu et al., 2017 |
Black tea | 0.22-0.35 | Liu et al., 2017 | Carbonated drink | 0.01-0.24 | Liu et al., 2017 |
Differences in fluoride concentrations in beverages and foods, of different countries, can be attributed to proximity of the area from which the raw materials come from to a volcanic zone, the composition of the soil, the water used for irrigation or for food and drinks preparation (Cantoral et al., 2019).
***
Table 4. – Fluoride concentration (mg L-1) in some fruit juices and milks.
N° | Sample | [F–] | N° | Sample | [F–] |
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1 | Juice peach 1 | 0.196 ± 0.002 | 56 | Juice 4 | 0.071 ± 0.002 |
2 | Juice ace 3 | 0.205 ± 0.002 | 4 | Milk 1 | < 0.020 |
3 | Juice ace 5 | 0.278 ± 0.003 | 60 | Milk 2 | < 0.020 |
19 | Orange juice homemade | < 0.034 | 61 | Milk 3 | < 0.020 |
35 | Juice peach 2 | 0.052 ± 0.001 | 135 | Milk 4 | 0.212 ± 0.002 |
In the carbonated soft drinks (Table 5), fluoride content is highly variable and ranges from the detection limit (0.020 mg L-1) to 0.47 mg L-1 (sample n°118). Probably, this depends on the fact that the aforementioned drinks are industrially prepared using different processes and raw materials and it is possible to hypothesize that the samples (n° 16, 53, 68, 121) having undetectable concentrations of fluoride (made by the same multinational industry) were prepared using demineralized water, while, the samples with measurable concentrations of fluoride were prepared with tap water. In particular, the drink called soda, generally, is produced by small local artisan companies and contains water, citric acid, sugar or sweeteners, flavourings and carbon dioxide. Since it does not contain phosphates, as in the case of cola, it can be produced with non-demineralised water.
Table 5. – Fluoride concentration (mg L-1) in carbonated drinks.
N° | Sample | [F—] | N° | Sample | [F—] |
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14 | Lemonade 1 | 0.078 ± 0.002 | 41 | Chinotto 1 | 0.24 ± 0.002 |
33 | Lemonade 2 | 0.36 ± 0.001 | 66 | Chinotto 2 | 0.16 ± 0.002 |
16 | Cola 1 | < 0.020 | 42 | Carbonated orange soda 1 | 0.29 ± 0.002 |
54 | Cola 2 | 0.096 ± 0.001 | 95 | Carbonated orange soda 2 | 0.038 ± 0.001 |
55 | Cola 3 | 0.28 ± 0.001 | 132 | Carbonated orange soda 3 | < 0.020 |
68 | Cola 4 | < 0.020 | 53 | Tonic water 1 | < 0.020 |
40 | Soda1 | 0.25 ± 0.002 | 10 | Tonic water 2 | 0.089 ± 0.001 |
118 | Soda 2 | 0.47 ± 0.002 | 121 | Tonic water 3 | < 0.020 |
80 | Effervescent | < 0.020 |
***
Table 8. Fluoride concentration (mg L-1) in some tea.
N° | Sample | [F–] | N° | Sample | [F–] |
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20 | Instant tea 1 | 0.26 ± 0.003 | 86 | Tea bag 7 | 1.4 ± 0.002? |
21 | Instant tea 2 | 0.043 ± 0.002 | 87 | Tea bag 8 | 1.8 ± 0.003? |
112 | Bottled tea 1 | 0.11 ± 0.002 | 88 | Tea bag 9 | 1.9 ± 0.002? |
129 | Bottled tea 2 | 0.81 ± 0.001 | 91 | Tea black oriental bag 10 | 3.2 ± 0.002? |
130 | Bottled tea 3 | 0.098 ± 0.002 | 92 | Tea bag 11 | 0.84 ± 0.002? |
127 | Tea vending machine | 3.5 ± 0.003 | 96 | Tea bag 12 | 1.1 ± 0.002? |
44 | Tea bag 1 | 2.9 ± 0.003 | 97 | Tea bag 13 | 2.6 ± 0.002? |
47 | Tea bag 2 | 2.2 ± 0.004 | 107 | Tea bag 14 | 0.53 ± 0.002? |
48 | Tea bag 3 | 0.63 ± 0.001 | 108 | Tea bag 15 | 1.6 ± 0.003? |
49 | Tea bag 4 | 2.8 ± 0.002 | 109 | Tea bag 16 | 1.7 ± 0.002? |
50 | Tea bag 5 | 2.8 ± 0.003 | 129 | Tea bag 17 | 1.6 ± 0.002? |
51 | Tea bag 6 | 2.7 ± 0,003 |
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average concentrations at 5, 10 and 30 min of infusion.
Considering that the highest amount of fluoride is released from the tea bags during the infusion process, we evaluated a possible correlation between F– concentration and infusion time (Table 9).
Table 9. – Fluoride concentration (mg L-1) in some tea at 5, 10 and 30 min.
N° | Sample | [F–] 5 min. | [F–] 10 min. | [F–] 30 min. | % Release 5 min | % Release 10 min |
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86 | Tea bag 7 | 1.2 ± 0.002 | 1.4 ± 0.002 | 1.7 ± 0.003 | 69 | 86 |
87 | Tea green orange bag 8 | 1.8 ± 0.003 | 1.9 ± 0.001 | 1.9 ± 0.001 | 92 | 98 |
88 | Tea breakfast bag 9 | 1.6 ± 0.002 | 1.9 ± 0.003 | 2.0 ± 0.003 | 80 | 92 |
91 | Tea black oriental bag 10 | 3.2 ± 0.002 | 3.2 ± 0.002 | 3.3 ± 0.002 | 96 | 97 |
92 | Tea bag 11 | 0.80 ± 0.002 | 0.87 ± 0.001 | 0.87 ± 0.001 | 91 | 99 |
96 | Tea bag 12 | 0.90 ± 0.001 | 1.2 ± 0.002 | 1.2 ± 0.002 | 72 | 95 |
97 | Tea bag 13 | 2.3 ± 0.001 | 2.6 ± 0.002 | 2.8 ± 0.002 | 80 | 93 |
107 | Tea bag 14 | 0.46 ± 0.002 | 0.55 ± 0.003 | 0.57 ± 0.002 | 81 | 95 |
108 | Tea bag 15 | 1.4 ± 0.003 | 1.6 ± 0.002 | 1.9 ± 0.002 | 74 | 85 |
109 | Tea bag 16 | 1.6 ± 0.001 | 1.7 ± 0.002 | 2.0 ± 0.003 | 79 | 87 |
129 | Tea bag 17 | 1.5 ± 0.002 | 1.5 ± 0.002 | 1.7 ± 0.003 | 89 | 92 |
Mean release | 82 | 85 |
From the Table 9 and the Fig. 3 it is noted that most of fluoride (mean 82%) is released within the first 5 minutes of infusion, passing from 5 to 10 minutes, it increases to 0.1-0.2 mg L-1 (mean 85%) and at 30 minutes there is a further mean increase of 0.1 mg L-1.
***
Fluoride is present in all the analysed wines (Table 11), except for sample n°32. The predominant factors that determine its presence could be attributed both to the geographical origin, therefore to the soil on which the vines grow (Fabianowicz et al., 2019) and to the irrigation water. The concentration of fluoride in wine, however, can increase as result of accidental contamination and the use of fluorinated compounds as antiseptics and insecticides against parasites affecting the vineyards (Rodríguez Gómez et al., 2003). This source is responsible for increasing the concentration of fluoride in wine up to 3 mg L-1 (Paz et al., 2017). A high F– concentration in wine was found in 1965 when Spanish alcoholics showed fluorosis which, due to its origin, was defined as vinic (Rodríguez Gómez et al., 2003). To prevent the toxic effects, the International Organization of Vine and Wine (OIV) has identified 1 mg L-1 as the maximum limit of fluoride in wine (Paz et al., 2017).
Table 11. – Fluoride concentration (mg L-1) in wine samples.
N° | Sample | [F—] | N° | Sample | [F—] |
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5 | Wine red 1 | 0.086 ± 0.001 | 32 | Wine white 3 | < 0.020 |
31 | Wine red 2 | 0.18 ± 0.002 | 59 | Wine white 4 | 0.062 ± 0.001 |
34 | Wine red 3 | 0.13 ± 0.001 | 93 | Wine white 5 | 0.070 ± 0.001 |
58 | Wine red 4 | 0.12 ± 0.001 | 103 | Wine white 6 | 0.094 ± 0.001 |
113 | Wine red 5 | 0.082 ± 0.002 | 117 | Wine white 7 | 0.200 ± 0.001 |
114 | Wine red 6 | 0.047 ± 0.001 | 116 | Wine Liqueurs | 0.056 ± 0.003 |
115 | Wine red 7 | 0.15 ± 0.002 | 101 | Wine Moscato | < 0.034 |
7 | Wine white 1 | 0.15 ± 0.002 | 94 | Wine Strawberry | 0.073 ± 0.001 |
30 | Wine white 2 | 0.16 ± 0.001 |
The wines analysed not exceed the limit identified by the Organizzazione Internazionale della Vigna e del Vino (OIV) and therefore all satisfy the quality criteria. The liquors and distillates, with few exceptions (sample n° 38 F– = 0.11 mg L-1 and n° 120 F– = 0.054 mg L-1), contain fluoride concentrations below the detection limit.
Fluoride concentrations from Teflon-coated tableware surfaces, measured on the water boiled in a small saucepan, were lower than detectable values. Ultimately, in our case, the Teflon coating does not release and does not contribute to the intake of fluori