Enduring fluoride health hazard for the Vesuvius area population: the case of AD 79 Herculaneum

The Dose-Response Effect of Fluoride Exposure on the Gut Microbiome and Its Functional Pathways in Rats

Metabolic activities within the gut microbiome are intimately linked to human health and disease, especially within the context of environmental exposure and its potential ramifications. Perturbations within this microbiome, termed "gut microbiome perturbations", have emerged as plausible intermediaries in the onset or exacerbation of diseases following environmental chemical exposures, with fluoride being a compound of particular concern. Despite the well-documented adverse impacts of excessive fluoride on various human physiological systems-ranging from skeletal to neurological-the nuanced dynamics between fluoride exposure, the gut microbiome, and the resulting dose-response relationship remains a scientific enigma. Leveraging the precision of 16S rRNA high-throughput sequencing, this study meticulously examines the ramifications of diverse fluoride concentrations on the gut microbiome's composition and functional capabilities within Wistar rats. Our findings indicate a profound shift in the intestinal microbial composition following fluoride exposure, marked by a dose-dependent modulation in the abundance of key genera, including Pelagibacterium, Bilophila, Turicibacter, and Roseburia. Moreover, discernible alterations were observed in critical functional and metabolic pathways of the microbiome, such as D-lyxose ketol-isomerase and DNA polymerase III subunit gamma/tau, underscoring the broad-reaching implications of fluoride exposure. Intriguingly, correlation analyses elucidated strong associations between specific bacterial co-abundance groups (CAGs) and these shifted metabolic pathways. In essence, fluoride exposure not only perturbs the compositional equilibrium of the gut microbiota but also instigates profound shifts in its metabolic landscape. These intricate alterations may provide a mechanistic foundation for understanding fluoride's potential toxicological effects mediated via gut microbiome modulation.

High concentration of sodium fluoride in drinking water induce hypertrophy versus atrophy in mouse skeletal muscle via modulation of sarcomeric proteins

Fluoride at high doses is a well-known toxic agent for the musculoskeletal system, primarily in bone and cartilage cells. Research on fluoride toxicity concerning particularly on the skeletal muscle is scanty. We hypothesized that during skeletal fluorosis, along with bone, muscle is also affected, so we have evaluated the effects of Sodium fluoride (NaF) on mouse skeletal muscles. Sodium fluoride (80 ppm) was administered to 5-week-old C57BL6 mice drinking water for 15 and 60 days, respectively. We carried out histology, primary culture, molecular and proteomic analysis of fluoride administered mouse skeletal muscles. Results indicated an increase in the muscle mass (hypertrophy) in vivo and myotubes ex vivo by activating the IGF1/PI3/Akt/mTOR signalling pathway due to short term NaF exposure. The long-term exposure of mice to NaF caused loss of muscle proteins leading to muscle atrophy due to activation of the ubiquitin-proteasome pathway. Differentially expressed proteins were characterized and mapped using a proteomic approach. Moreover, the factors responsible for protein synthesis and PI3/Akt/mTOR pathway were upregulated, leading to muscle hypertrophy during the short term NaF exposure. Long term exposure to NaF resulted in down-regulation of metabolic pathways. Elevated myostatin resulted in the up-regulation of the muscle-specific E3 ligases-MuRF1, promoting the ubiquitination and proteasome-mediated degradation of critical sarcomeric proteins.

Molecular signatures written in bone proteins of 79 AD victims from Herculaneum and Pompeii

An extensive proteomic analysis was performed on a set of 12 bones of human victims of the eruption that in AD 79 rapidly buried Pompeii and Herculaneum, allowing the detection of molecular signatures imprinted in the surviving protein components. Bone collagen survived the heat of the eruption, bearing a piece of individual biological history encoded in chemical modifications. Here we show that the human bone proteomes from Pompeii are more degraded than those from the inhabitants of Herculaneum, despite the latter were exposed to temperatures much higher than those experienced in Pompeii. The analysis of the specimens from Pompeii shows lower content of non-collagenous proteins, higher deamidation level and higher extent of collagen modification. In Pompeii, the slow decomposition of victims' soft tissues in the natural dry-wet hydrogeological soil cycles damaged their bone proteome more than what was experienced at Herculaneum by the rapid vanishing of body tissues from intense heat, under the environmental condition of a permanent waterlogged burial context. Results herein presented are the first proteomic analyses of bones exposed to eruptive conditions, but also delivered encouraging results for potential biomarkers that might also impact future development of forensic bone proteomics.

Effect of Fluoride in Drinking Water on Fecal Microbial Community in Rats

Intestinal nutrition has a close association with the onset and development of fluorosis. Intestinal microbes play a major role in intestinal nutrition. However, the effect of fluoride on intestinal microbes is still not fully understood. This study aimed to evaluate the dose-response of fluoride on fecal microbes as well as the link between fluorosis and fecal microbes. The results showed that fluoride did not significantly alter the diversity of fecal microbiota, but richness estimators (ACE and Chao) increased first, and then decreased with the increase of water fluoride. At the genus level, 150 mg/L fluoride significantly reduced the abundances of Roseburia and Clostridium sensu stricto, and 100 mg/L and 150 mg/L fluoride obviously increased the abundances of Unclassified Ruminococcaceaes and Unclassified Bdellovibrionales, respectively. The correlation analysis showed fluoride exposure had a negative association with Roseburia and Turicibacter and was positively associated with Pelagibacterium, Unclassified Ruminococcaceae, and Unclassified Bdellovibrionales. Dental fluorosis was negatively associated with Clostridium sensu stricto, Roseburia, Turicibacter, and Paenalcaligenes and had a positive association with Pelagibacterium, Unclassified Ruminococcaceae, and Unclassified Bdellovibrionales. In conclusion, this study firstly reports fluoride in drinking water has a remarkable biphasic effect on fecal microbiota in rats, and some bacteria are significantly associated with fluoride exposure and dental fluorosis. These results indicate the gut microbiota may play an important role in fluorosis, and some bacteria are likely to be developed as biomarkers for fluorosis.

Study on Environmental Factors of Fluorine in Chagan Lake Catchment, Northeast China

The Chagan Lake Catchment is located in the midwest of Songnen Plain, which is a typical high fluoride groundwater area. High fluoride water has an important impact on the economic development and ecosystem stability of Chagan Lake. In this study, the spatial distribution characteristics and influencing factors of fluorine in Chagan Lake Catchment are discussed by using hydrochemistry and mathematical statistical analysis. The groundwater in the study area was characterized as Na+-rich and Ca2+-poor, with a high pH value and high HCO3– content. The average concentration of F– was 3.02 mg/L, which was the highest in Qian’an County. The dissolution of fluorine-containing minerals and the desorption of F– in soil provided the source of F– in groundwater, while calcite and dolomite precipitation, cation exchange, and evaporation concentration provided favorable conditions for F– dissolving, migration, and enrichment in water. In addition, the concentration of F– in surface water was 4.56 mg/L, and the highest concentration was found in Hongzi Pool and Hua’ao Pool. The elevated concentrations of F– in both surface water and groundwater in the study were affected by human factors, such as rice planting and water conservancy project construction.

Increasing fluoride content deteriorates rat bone mechanical properties

Elevation of bone fluoride levels due to drinking beverages with high fluoride content or other means such as inhalation can result in skeletal fluorosis and lead to increased joint pain, skeletal deformities, and fracture. Because skeletal fluorosis alters bone's mineral composition, it is likely to affect bone's tissue-level mechanical properties with consequent effects on whole bone mechanical behavior. To investigate this, we determined whether incubation with in vitro sodium fluoride (NaF) altered bone's mechanical behavior at both the tissue- and whole bone-levels using cyclic reference point indentation (cRPI) and traditional 3-point bending, respectively. Forty-two ulnas from female adult rats (5-6 months) were randomly divided into 5 groups (vehicle, 0.05 M NaF, 0.25 M NaF, 0.75 M NaF, and 1.5 M NaF). Bones were washed in a detergent solution to remove organic barriers to ion exchange and incubated in respective treatment solutions (12 h, 23 °C). Cortical tissue mineral density (TMD) and geometry at the mid-diaphysis were determined by microCT. cRPI was performed on the distal diaphysis (9 N, 2 Hz, 10 cycles), and then bones were tested in 3-point bending to assess whole bone mechanical properties. The incubations in vehicle (0 M) up to 1.5 M in vitro NaF concentrations achieved bone fluoride levels ranging from approximately 0.70 to 15.8 ppm. NaF-incubated bones had significantly greater indentation distances, higher displacement-to-maximum force, and lower estimated elastic modulus, ultimate stress, and bending rigidity with increasing NaF concentration compared to vehicle-incubated bones. cRPI variables were moderately correlated to whole bone mechanical properties such that higher indentation distances were associated with lower estimated elastic modulus, ultimate stress, and bending rigidity. In conclusion, in vitro NaF incubation mostly has a deleterious effect on bone mechanical behavior with increasing NaF levels that is independent of bone turnover and reflected, in part, by less resistance of the tissue to cRPI-based indentation.

Bone quality in fluoride-exposed populations: A novel application of the ultrasonic method

BACKGROUND

Various studies, mostly with animals, have provided evidence of adverse impacts of fluoride (F-) on bone density, collagen and microstructure, yet its effects on overall bone quality (strength) has not been clearly or extensively characterized in human populations.

OBJECTIVE

In this observational study, we assessed variation in an integrated measures of bone quality in a population exposed to wide-ranging F- levels (0.3 to 15.5 mg/L) in drinking water, using a novel application of non-ionizing ultrasonic method.

METHOD

We collected 871 speed of sound (SOS) measurements from 341 subjects residing in 25 communities, aged 10-70 years (188 males and 153 females). All subjects received scans of the cortical radius and tibia, and adults over the age of 19 received an additional scan of the phalanx. Associations between F- in drinking water and 24-h urine samples, and SOS as a measure of bone quality, were evaluated in bivariate and multivariable regressions adjusting for age, sex, BMI, smoking, and toothpaste use.

RESULTS

We found negative associations between F- exposure and bone quality at all three bones. Adult tibial SOS showed the strongest inverse association with F- exposure, which accounted for 20% of the variance in SOS measures (r = 0.45; n = 199; p < 0.0001). In adjusted analysis, a 1 mg/L increase in F- in drinking water was related to a reduction of 15.8 m/s (95% CI: -21.3 to -10.3), whereas a 1 mg/L increase in 24-h urinary F- (range: 0.04-39.5 mg/L) was linked to a reduction of 8.4 m/s (95% CI: -12.7, -4.12) of adult tibial SOS. Among adolescents, in contrast, weaker and non-significant inverse associations between F- exposure and SOS were found, while age, gender, and BMI were more significant predictors than in adults.

CONCLUSIONS

These results are indicative of a fluoride-induced deterioration of bone quality in humans, likely reflecting a combination of factors related to SOS: net bone loss, abnormal mineralization and collagen formation, or altered microarchitecture. The portable and low-cost ultrasound technique appears potentially useful for assessment of bone quality, and should be tested in other locations and for other bone-related disorders, to assess the feasibility of its more extensive diagnostic use in hard-to-reach rural regions.

Evidence of Skeletal Fluorosis at the Ray Site, Illinois, USA: a pathological assessment and discussion of environmental factors

OBJECTIVE

To carefully assess skeletal lesions in close environment context in order to evaluate whether skeletal fluorosis was present in individuals living in the prehistoric Midwest, USA.

MATERIALS

Skeletal remains from minimally 117 individuals recovered from the Ray Site, located in western Illinois (USA) and dated to the Middle/early Late Woodland periods (50 BC-AD 400).

METHODS

Macroscopic evaluation of all recovered skeletal elements.

RESULTS

Eight individuals display a constellation of abnormal bony changes, including osteosclerosis, a high frequency of fractures, and dental abnormalities.

CONCLUSIONS

The osteosclerotic changes along with the naturally high fluoride content of west central Illinois soil and water suggests the presence of skeletal fluorosis.

SIGNIFICANCE

This is the first report of skeletal fluorosis from archaeologically recovered human remains from North America.

LIMITATIONS

The ambiguous nature of the skeletal changes associated with fluorosis, especially in the less severe stages of the disease, renders determination of the etiology difficult.

SUGGESTIONS FOR FURTHER RESEARCH

The continuation of paleopathological investigations of fluoride toxicity within archaeological communities recovered from this region with emphasis on the incorporation of biomedical and environmental data. Furthermore, complementary analyses of the chemical composition and the histological presentation of the skeletons could provide support for this diagnosis.

Dental fluorosis in the Vesuvius towns in AD 79: a multidisciplinary approach

Background: Endemic fluorosis induced by high concentrations of fluoride in groundwater and soils is a major health problem in several countries, particularly in volcanic areas.Aim: To evaluate the occurrence of dental fluorosis resulting from exposure to high levels of environmental fluoride in 79 AD Herculaneum and close Vesuvius towns.Subjects and methods: The occurrence of dental fluorosis from teeth of the Herculaneum victims of the 79 AD eruption and some individuals from Pompeii (14-37 AD) and Nocera Inferiore (Salerno, IV sec. AD) was detected by means of Particle Induced Gamma-ray Emission technique (PIGE).Results: A clinical and analytical scenario of dental fluorosis resulted from the extreme high fluorine tooth content detected in teeth from Herculaneum and the Vesuvius area inhabitants. The adoption of PIGE technique has proved to be particularly effective in showing moderate as well as milder forms of dental fluorosis, otherwise not clearly detectable by clinical and histological analysis.Conclusions: Morphological, histological and elemental analysis of teeth of the 79 AD Herculaneum population show that in this area fluorosis occurred since Roman times.

A hypothesis of sudden body fluid vaporization in the 79 AD victims of Vesuvius

In AD 79 the town of Herculaneum was suddenly hit and overwhelmed by volcanic ash-avalanches that killed all its remaining residents, as also occurred in Pompeii and other settlements as far as 20 kilometers from Vesuvius. New investigations on the victims' skeletons unearthed from the ash deposit filling 12 waterfront chambers have now revealed widespread preservation of atypical red and black mineral residues encrusting the bones, which also impregnate the ash filling the intracranial cavity and the ash-bed encasing the skeletons. Here we show the unique detection of large amounts of iron and iron oxides from such residues, as revealed by inductively coupled plasma mass spectrometry and Raman microspectroscopy, thought to be the final products of heme iron upon thermal decomposition. The extraordinarily rare preservation of significant putative evidence of hemoprotein thermal degradation from the eruption victims strongly suggests the rapid vaporization of body fluids and soft tissues of people at death due to exposure to extreme heat.

Spondylolysis in the past: A case study of hunter-gatherers from Southern Patagonia

Spondylolysis is a fracture of the pars interarticularis, the portion of the neural arch that lies between the superior articular facets and the inferior articular facets. Clinical evidence has suggested repetitive trauma to be the most probable cause, even though morphological weakness of the vertebra is probably also involved. Prevalence is between 3% and 8% in modern populations, while in archaeological samples it varies from 0% to 71.4%. Considering that very little data about this condition is available in past populations from the southern extreme of South America, the aim of this paper is to analyze the spondylolysis in a human skeletal sample from Southern Patagonia and, at the same time, to explore the prevalence of spondylolysis in archaeological contexts around the world to gain a better understanding of the results presented here. The Southern Patagonian skeletal series analyzed here showed a prevalence of 20%, with lower prevalence in the pre contact sample (11.1%) than in the contact period (23.1%). Skeletons from the Salesian Mission "Nuestra Señora de La Candelaria" showed a higher prevalence (25%) than the sample of skeletal remains recovered from outside the mission (20%), suggesting that changes in lifestyle of hunter-gatherers during contact could be implicated in the development of spondylolysis in this sample. A worldwide survey displays a wide range of prevalence figures in American and Asian samples and low diversity between African and European populations. Hunter-gatherers from Southern Patagonia showed similar values to those observed in other American samples.

Association of dental and skeletal fluorosis with calcium intake and serum vitamin D concentration in adolescents from a region endemic for fluorosis

CONTEXT

Fluorosis is controlled by the duration of fluoride exposure and calcium and Vitamin D nutrition status.

AIM

To examine (a) prevalence of dental and skeletal fluorosis in adolescents from upper, middle, and lower socioeconomic strata (SES) and (b) association of fluorosis with calcium intake and Vitamin D status.

SETTINGS AND DESIGN

A cross-sectional study conducted in 10-13.9 years apparently healthy adolescents (n = 90), from different SES of Patan (Gujarat, India).

MATERIALS AND METHODS

Dental fluorosis was graded as mild, moderate, and severe. Radiographs of the right hand and wrist were examined and graded. Serum 25 hydroxyvitamin D3 (25OHD) and parathyroid hormone concentrations were measured. Diet was recorded (24 h recall) and calcium intake was computed (C-diet V-2.1, 2013, Xenios Technologies Pvt. Ltd).

STATISTICAL ANALYSIS

Generalized linear model was used to analyze relationships between fluorosis, SES, serum 25OHD concentration, and calcium intake.

RESULTS

Fluorosis was predominant in lower SES (17% had both dental and radiological features whereas 73% had dental fluorosis); no skeletal deformities were observed. Mean 25OHD concentrations and dietary calcium were 26.3 ± 4.9, 23.4 ± 4.7, and 18.6 ± 4 ng/ml and 441.2 ± 227.6, 484.3 ± 160.9, and 749.2 ± 245.4 mg/day, respectively, for lower, middle, and upper SES (P < 0.05). Fluorosis and SES showed a significant association (exponential β = 2.5, P = 0.01) as compared to upper SES, middle SES adolescents were at 1.3 times while lower SES adolescents were at 2.5 times higher risk. Serum 25OHD concentrations (P = 0.937) and dietary calcium intake (P = 0.825) did not show a significant association with fluorosis.

CONCLUSION

Fluorosis was more common in lower SES adolescents, probably due to the lack of access to bottled water. Relatively adequate calcium intake and serum 25OHD concentrations may have increased the efficiency of dietary calcium absorption, thus preventing severe fluorosis.

Impact of volcanic plume emissions on rain water chemistry during the January 2010 Nyamuragira eruptive event: implications for essential potable water resources

On January 2, 2010 the Nyamuragira volcano erupted lava fountains extending up to 300 m vertically along an ~1.5 km segment of its southern flank cascading ash and gas on nearby villages and cities along the western side of the rift valley. Because rain water is the only available potable water resource within this region, volcanic impacts on drinking water constitutes a major potential hazard to public health within the region. During the 2010 eruption, concerns were expressed by local inhabitants about water quality and feelings of physical discomfort (e.g. nausea, bloating, indigestion, etc.) after consuming rain water collected after the eruption began. We present the elemental and ionic chemistry of drinking water samples collected within the region on the third day of the eruption (January 5, 2010). We identify a significant impact on water quality associated with the eruption including lower pH (i.e. acidification) and increases in acidic halogens (e.g. F(-) and Cl(-)), major ions (e.g. SO(4)(2-), NH(4)(+), Na(+), Ca(2+)), potentially toxic metals (e.g. Al(3+), Mn(2+), Cd(2+), Pb(2+), Hf(4+)), and particulate load. In many cases, the water's composition significantly exceeds World Health Organization (WHO) drinking water standards. The degree of pollution depends upon: (1) ash plume direction and (2) ash plume density. The potential negative health impacts are a function of the water's pH, which regulates the elements and their chemical form that are released into drinking water.