Recent Biomarkers for Monitoring the Systemic Fluoride Levels in Exposed Populations: A Systematic Review

Amide-imidol tautomerism based fluorescence turn-on probe for selective detection of fluoride ion through restricted intramolecular rotation

Fluoride ions play a crucial role in many biological functions such as bone disease treatment, water fluoridation, and caries many other treatments. Excessive intake of fluoride ions causes chronic diseases such as Arthritis, oxidative stress, brittle bones, brain damage, and cancer. With these reasons, a cost-effective and highly specific probe 3PDA have been developed for real-time monitoring of fluoride ions. Probe 3PDA is a pyridine-based "Turn-On" sensor, easily synthesized through the Schotten-Baumann reaction. This pyridine based probe demonstrated interesting optical characteristics such as large Stoke's shift (109 nm), solvatochromism, pH sensing, and ACQ behavior. Furthermore, probe 3PDA was effectively utilized for nanomolar (nM) sensing of fluoride ions through covalent interactions. UV-visible, fluorescence, and 1H NMR titration analyses were executed to verify amide-imidol tautomerism as a sensing mechanism. Amide-imidol tautomerism become highly favorable when fluoride interacts with probe 3PDA molecule. Fluoride ion as a strong hydrogen bond acceptor facilitates the conversion of amide form into imidol tautomer and causes restriction of intramolecular rotation (RIR) of bonds. Overall, presence of fluoride ions makes probe 3PDA molecule more rigid and less flexible. Moreover, DLS analysis was executed to verify the formation of aggregation and excimer disaggregation. DFT studies were employed to validate the sensitivity of probe 3PDA toward fluoride ions. The calculated LOD was 150 nM and LOQ was 502 nM for fluoride ion detection. Probe 3PDA was employed for naked eye solid state sensing of fluoride ions under daylight and UV irradiation at 365 nm. Furthermore, 3PDA was practically applied to estimate fluoride concentration in oral care products, mineral water, and spiked lake water. 3PDA-coated TLC strips were also designed as tiny portable tools for fluoridesensing.

Systemic fluoride levels in toenails as biomarkers of exposure and their association with the severity of dental fluorosis in Mexican schoolchildren - a cross-sectional study

INTRODUCTION

Elevated fluoride (F-) exposure during childhood produces dental fluorosis (DF). Nails have been used for monitoring systemic F- in relation to DF. The aim of this study was to evaluate F- levels in toenails in association with DF severity in Mexican schoolchildren.

MATERIALS AND METHODS

120 schoolchildren from nonendemic areas (NEAs) and endemic F- areas (EAs) were screened for DF via the Thylstrup and Fejerskov index (TFI). Toenails were collected to quantify systemic F-. The associations between the biomarker, DF severity, tap water intake, sex, and age were analyzed.

RESULTS

The mean F- in toenails in the NEAs and EAs were 0.63 ± 0.43 and 2.72 ± 1.38 mg/kg, respectively (p < 0.001). A positive correlation was observed between the biomarker and DF severity (rs = 0.755, p < 0.001). Tap water consumption and the biomarker were associated with DF severity (p < 0.001). Within TFI7-8 the mean F- level was higher in those ages 10-11 than in those ages 8-9 (p < 0.05).

CONCLUSION

Systemic F- levels in toenails are associated with DF severity in Mexican schoolchildren from both the NEAs and the EAs, which reflects the ability of the biomarker to accurately record the exposure to the compound in relation to clinical damage.

Drug molecules beyond chemical biology: fluorescence- and DFT-based investigations for fluoride ion sensing and the trace detection of chloroform

Excessive unmonitored use of fluoride has remained a threatening issue for a long time now as its long-term use is linked to several health issues. Similarly, chloroform is a highly carcinogenic solvent that requires proper monitoring. The increasing demand for a convenient, selective and sensitive fluoride and chloroform sensor intrigued us to utilize etoricoxib (ECX) as a sensor as it is highly safe and easily available. The photophysical properties of ECX, which were previously unexplored, were now studied with increasing water fractions and a significant aggregation-induced emission enhancement (AIEE) was seen through fluorescence spectroscopy. ECX was also successfully used for the trace level detection of chloroform through a significant emission enhancement. Similarly, the ECX-based sensor successfully detected fluoride ions by showing enhancement in emission intensity with maximum emission wavelength at 373 nm. Through fluorescence titration experiments, the effects of different conditions and interfering species on the sensing efficiency of ECX were studied, and the results showed that the sensor was highly selective and sensitive towards fluoride, with a limit of detection of 20 nM. Other than fluorescence spectroscopy, the type of interaction between the sensor and analyte was also studied through UV-Vis spectroscopy, revealing a non-covalent type of interaction, which was further validated through DFT studies. Frontier molecular orbital (FMO) analysis was performed along with density of state (DOS) studies to investigate the energy levels of the orbitals. Non-covalent interaction (NCI) and natural bond orbital (NBO) analysis provided information about the types of interaction and charge transfer. ECX has the potential to be used for real-time sensing applications and could be used for sensing moisture and fluoride in real samples.

The Association between Fluoride and Bone Mineral Density in US Children and Adolescents: A Pilot Study

The aim of this study was to examine the association between fluoride exposure and bone mineral density (BMD) in children and adolescents. We used data from the National Health and Nutrition Examination Survey (NHANES) 2015-2016. The fluoride concentrations in the water samples, plasma samples, and urine samples were measured electrometrically using an ion-specific electrode. Total body less head BMD (TBLH BMD) was measured using dual-energy X-ray absorptiometry (DXA). Weighted generalized linear regression models and restricted cubic splines (RCS) regression models were used to analyze the relationships between the three types of fluoride exposure and TBLH BMD. We performed subgroup analyses stratified by sex. A total of 1413 US children and adolescents were included in our study. In our linear regression models, we found inverse associations between fluoride concentrations in water and plasma and TBLH BMD. Additionally, we discovered a non-linear association between fluoride concentrations in water and plasma and TBLH BMD. No significant association or non-linear relationship was found between urine fluoride levels and TBLH BMD. This nationally representative sample study provides valuable insight into the intricate connection between fluoride exposure and skeletal health in children and adolescents.

Fluoride - a scoping review for Nordic Nutrition Recommendations 2023

Fluoride has a well-documented role in the prevention and treatment of dental caries, but the mechanism is attributed to local effects on the tooth enamel surface rather than systemic effects. Fluoride is not considered essential for humans, no deficiencies are known, and no optimal range, which will not result in moderate fluorosis in some individuals, can be set. Recently, research studies have shown evidence for a relationship between fluoride intake and cognitive outcomes and interaction with iodine nutrition, but the evidence is weak so more data are warranted. For performing longitudinal cohort studies in the Nordic and Baltic region, data on fluoride in food and beverages need to be implemented in food composition tables. As the preventive effects of fluoride are mainly from topical treatment, monitoring of fluoride intake and establishing reference values for fluoride in urine and plasma are warranted to establish safe intake values.

Investigation on Applying Biodegradable Material for Removal of Various Substances (Fluorides, Nitrates and Lead) from Water

Sapropel was used as a biodegradable material for water treatment. Sapropel is a sedimentary layer of a mix of organic and inorganic substances accumulated in the bottoms of lakes for thousands of years. It is a jelly-like homogeneous mass and has properties of sorption. Sapropel is used as a biosorbent and an environment-friendly fertiliser, and it is used in building materials and in the beauty industry as well. In water, there are abundant various solutes that may cause a risk to human health. Such substances include fluorides, nitrates and lead in different sources of water. The goal of this investigation is to explore and compare the efficiencies of removal of different pollutants (fluorides, nitrates and lead) from aqueous solutions upon using sapropel as a sorbent. In this research, various doses of sapropel (0.1, 0.5, 1, 5, 10, 20, 50, 100 and 200 g/L) and various mixing times (15, 30, 60, 90 and 120 min) were used for removal of fluorides, nitrates and lead from aqueous solutions. It was found that the maximum efficiency (up to 98.57%) of lead removal from aqueous solutions by sapropel was achieved when the minimum doses of it (0.1 and 0.5 g/L) were used. The most efficient removal of fluorides (64.67%) was achieved by using 200 g/L of sapropel and mixing for 120 min. However, sapropel does not adsorb nitrates from aqueous solutions.

Multiple anthropogenic influences in the Pará River (Amazonia, Brazil): A spatial-temporal ecotoxicological monitoring in abiotic and biotic compartments

The mineral wealth of the Amazon region is prone to intense exploration with consequent metals mobilization in ecosystems. Besides that, a number of other anthropogenic activities contribute to the imbalance of this important environment. The Pará River is an important water body in the Amazon basin and is under multiple anthropogenic influences, including disorderly urbanization, port activities and processing of minerals such as bauxite and kaolin. In this study, metals concentrations (Al, Cr, Pb, Ba, Ni, and Mn) in water, sediment and organisms (the fish Cheirocerus goeldii and the shrimp Macrobrachium amazonicum) and biochemical biomarkers (total antioxidant capacity, ACAP and lipid peroxidation, LPO) were analyzed along five points in the Para River with different distances to a center of anthropogenic activity, in three seasonal periods (rainy, transition and dry). Metals concentrations were similar among sites in each seasonal period but Aluminium (Al) presented the highest concentrations among all analyzed metals both in sediment and water considering all sampling points and all seasonal periods. In the dissolved fraction, Al had values above those established by the local environmental agency, especially during the rainy season. In the biotic compartment, both fish and shrimps showed higher concentrations of metals (Al and Ba) in the rainy season compared to the other seasons. Shrimp was more responsive to metal accumulation than fish, showing an adaptive response of biomarkers. Fish showed an increase of LPO in gills for individuals from the point of greater anthropogenic interference during the rainy season, but no differences in metal accumulation. We conclude that there is a seasonal pattern of metals concentration in different environmental compartments. Metal concentration in organisms and biomarkers responses, showed the effect of anthropogenic influences, which was not evident in results from chemical analyses alone, due to the intensive hydrodynamics in the region.

A Systematic Review and Meta-Analysis of the Relationship Between the Severity of Dental Fluorosis and Fluoride Biomarkers in Endemic Areas

The intake of high concentrations of fluoride, mainly through drinking water, diet and fluoridated dentifrices, produces fluorosis, which in its early stages is manifested as dental fluorosis (DF). To recognize exposure to fluoride in endemic areas and to evaluate the risk of developing health impairment, the WHO has established several biomarkers that are used to determine systemic fluorine (F-) exposure. Thus, the aim of this study was to conduct a systematic review and meta-analysis of the relationship between the severity of DF and fluoride biomarkers in endemic areas. The protocol of this study was previously registered as CRD42021244974. A digital search was carried out in PubMed/Medline, SpringerLink, Scopus, Cochrane and Google Scholar by employing the keywords "urine", "nails", "hair", "plasma", "saliva" and "dental fluorosis" for the original studies with content associated with F- for the biomarkers and DF. The mean difference was established as the effect measure for the meta-analysis. Seven studies fulfilled the eligibility criteria, among which five assessed urine and two employed nails as fluoride biomarkers. A positive significant difference was found between the biomarkers and the severity of DF (0.27, p < 0.001) and individually for each biomarker (urine: 0.14, p = 0.001; nails: 0.88, p < 0.05). The F- concentration in urine and nails is correlated with the severity of DF, with the most evident differences between healthy individuals and those with mild severity. Both biomarkers are adequate to assess this relationship in endemic areas of fluoride and DF.

Mapping the evidence for monitoring fluoride exposure in community prevention programmes for oral health using nail clippings and spot urine samples: a scoping review

BACKGROUND

There is an increased interest in identifying practical and accurate biomarkers for fluoride exposure. Due to the narrow 'dose-gap' between the benefit of caries reduction and the risk of dental fluorosis, monitoring of fluoride exposure is vital when introducing any fluoridation programme for the prevention of dental caries. This scoping review aimed to ascertain the nature and extent of the available evidence on how spot urine and nail clippings are used to measure fluoride intake/exposure, by using a unique approach of mapping the studies according to population, setting, type of study design, methodology and analytical approach in community prevention programmes.

METHODS

Multiple relevant databases were searched up to July 2021 for any study designs, including randomised controlled studies, quasi-experimental studies, surveys, retrospective and prospective cohort studies, case studies, phenomenological studies, and expert opinions.

RESULTS

The search retrieved 9,222 studies of which 155 met the inclusion criteria. A high proportion of the studies (25.2%) originated from Latin America and the Caribbean continent subregion. However, per country, China recorded the highest number, followed by India and Mexico. The majority (62.6%) employed a cross-sectional study design, and 65.8% combined participants from different age groups. Of the included studies, 82.6% used spot urine samples as a biomarker for assessing fluoride intake/exposure. Water fluoride concentration was reported in 66.5% of the studies with 46.6% of all included studies reporting a water fluoride concentration of > 1.2 mg/L. The methods used in assessing oral hygiene and dietary intake were not reported in 72.3% and 71.0% of the included studies, respectively. Only 35.5% of the included studies assessed the relationship between fluoride exposure and excretion.

CONCLUSIONS

This review revealed a large variability in the way in which spot urine samples and/or nail clippings are used to measure fluoride exposure in different settings and situations. Particularly, there are inconsistencies in the methodologies and the analytical approaches used in assessing fluoride exposure. Therefore, there is a need for more rigorous primary research studies using standardised approaches to determine the suitability of spot urine samples and nail clipping as biomarkers for monitoring fluoride exposure.

The association between fluoride in water and blood pressure in children and adolescents

BACKGROUND

The objective of this study was to determine the association between water and plasma fluoride and blood pressure (BP) among children and adolescents.

METHODS

Our study population was individuals of 8-18 years in the 2013-2016 National Health and Nutrition Examination Survey. We performed a multivariable linear and logistic regression analysis to examine the relationship between fluoride and BP.

RESULTS

In a linear regression analysis for systolic BP (SBP) (mm Hg) adjusting for age, sex, race, and poverty, fluoride in water (mg/L) was significant with a coefficient of -0.44 (p = 0.046) among adolescents (12-18 years). Additional adjustments for race, poverty, serum levels of cotinine, and BMI remained significant. While an inverse relationship was found in children (8-11 years), none were significant. Fluoride in plasma was not significant across all ages. The odds ratio of high BP for an increase in water fluoride also was not significant.

CONCLUSIONS

Higher concentrations of fluoride in water were associated with low SBP only among adolescents. Fluoride alone cannot be responsible for BP as several biological metabolic processes may influence its physiological effects. Fluoride consumption should be considered in conjunction with these processes.

IMPACT

The high fluoride in drinking water was statistically significantly associated with low systolic BP in children and adolescents. The odds ratio of high BP for an increase in fluoride in drinking water was not significant. Our study contributes to the existing literature by providing individualized data and results on an individual level.

Dust Characterization and Its Potential Impact during the 2014–2015 Fogo Volcano Eruption (Cape Verde)

Fogo (Fogo Island) is the youngest and most active volcano of Cape Verde. The last eruption occurred in 2014–2015. Aiming to assess the dust sources that impacted the air quality during the present study period, fresh lava samples were collected, while Saharan dust intrusions and transport were modeled. Rooftop dust was also collected on the island dwellings and a mineralogical and chemical characterization was undertaken. Air quality monitors were used to obtain concentrations of atmospheric particulate matter (PM) and gaseous pollutants. The mineralogical constitution was assessed by XRD and Electron Microprobe. The pseudototal chemical concentration was performed by XRF, ICP-MS and SEM; the latter includes particles morphology. During the study, WRF-CHIMERE results showed the intrusion of desert dust which affected the air quality. Lava was classified as tephritic to basanitic, with high potassium content. The Pollution Load Index for rooftop dust was >1 in all samples, suggesting an enrichment. Higher values were found in dust size fraction <63 µm, with contamination factor pointing to high enrichment of As, Ni and Pb, and very high enrichment of Cd. The non-carcinogenic hazard estimated for children suggested that health problems may arise. The carcinogenic risk was above the target risk, mostly due to As > Pb > Co. Ingestion was the main exposure route. PM10 concentrations exceeded the 24-h mean of 50 µg/m3 recommended by WHO. Nevertheless, TVOCs displayed levels lower than guidelines. The highest levels of CO2 were recorded in more populated villages and farthest from the volcano.