Skeletal fluorosis in a resettled refugee from Kakuma refugee camp

Prevalence of Skeletal Fluorosis in Northern Tanzania: A Follow-Up Study

OBJECTIVES

Skeletal fluorosis is a metabolic bone disease caused by excessive exposure to fluoride, predominantly through contamination of drinking water. This study aimed to identify all cases of skeletal fluorosis in Tindigani village situated in Northern Tanzania. This was done following changes in drinking water sources after a previous prevalence study in 2009 in this population.

METHODS

In a door-to-door cross-sectional study of Tindigani village, a sample of residents was assessed for skeletal fluorosis and dental fluorosis. Diagnosis of skeletal fluorosis was based on pre-defined angles of deformity of the lower limbs. Dental fluorosis was diagnosed and graded using the Thylstrup and Fejerskov Index. Samples from current drinking water sources underwent fluoride analysis.

RESULTS

Tindigani village had a population of 1,944 individuals. Of the 1,532 individuals who were screened, 45 had skeletal fluorosis, giving a prevalence of 3.3% (95% CI=2.4, 4.3). Dental fluorosis was present in 82.5% of those examined (95% CI=79.8, 85.3). Dental fluorosis was present in all individuals with skeletal fluorosis and at higher grades than in the rest of the population. Drinking water samples were collected from 28 sources. These included piped, surface, well, and borehole water sources. Fluoride concentrations ranged from 0.45-38.59 mg/L of fluoride.

CONCLUSIONS

Skeletal fluorosis is an ongoing but preventable health problem in the current population. The delivery of sustainable low fluoride piped water to this community would be of clear health benefit. This has been addressed at a local level.

Periarticular calcifications containing giant pseudo-crystals of francolite in skeletal fluorosis from 1,1-difluoroethane "huffing"

Inhalant use disorder is a psychiatric condition characterized by repeated deliberate inhalation from among a broad range of household and industrial chemical products with the intention of producing psychoactive effects. In addition to acute intoxication, prolonged inhalation of fluorinated compounds can cause skeletal fluorosis (SF). We report a young woman referred for hypophosphatasemia and carrying a heterozygous ALPL gene variant (c.457T>C, p.Trp153Arg) associated with hypophosphatasia, the heritable metabolic bone disease featuring impaired skeletal mineralization, who instead suffered from SF. Manifestations of her SF included recurrent articular pain, axial osteosclerosis, elevated bone mineral density, maxillary exostoses, and multifocal periarticular calcifications. SF was suspected when a long history was discovered of 'huffing' a computer cleaner containing 1,1-difluoroethane. Investigation revealed markedly elevated serum and urine levels of F^-. Histopathology and imaging techniques including backscattered electron mode scanning electron microscopy, X-ray microtomography, energy dispersive and wavelength dispersive X-ray emission microanalysis, and polarized light microscopy revealed that her periarticular calcifications were dystrophic deposition of giant pseudo-crystals of francolite, a carbonate-rich fluorapatite. Identifying unusual circumstances of F^- exposure is key for diagnosing non-endemic SF. Increased awareness of the disorder can be lifesaving.

Fluoride regulates chondrocyte proliferation and autophagy via PI3K/AKT/mTOR signaling pathway

Fluorine is an essential trace element for human health. However, excessive fluoride intake causes skeletal fluorosis which affects cartilage development. Fluoride inhibited chondrocyte proliferation which is the initial and critical step of endochondral ossification, but the underlying mechanism has not been clearly illustrated. Mammalian target of rapamycin (mTOR) is an important protein kinase which modulates various cellular processes and is believed to be a central regulator of chondrocyte proliferation and autophagy. In this study, we explored the effect of fluoride on the proliferation and autophagy of chondrocytes and the regulatory role of mTOR signaling pathway. Our results suggested that NaF inhibited the protein expressions of proliferating cell nuclear antigen (PCNA) and pS6 in cultured fetal rat tibias. Furthermore, NaF significantly downregulated the expressions of mTOR signaling pathway-related genes, including PI3K, AKT, mTOR, 4EBP1 and S6K1 in mouse ATDC5 chondrogenic cell line. We also found that NaF increased autophagy in ATDC5 cells. The mRNA and protein levels of autophagy-related genes LC3, Beclin1 and p62 were significantly changed after NaF treatment. Further studies demonstrated that MHY1485, a small-molecular mTOR activator, totally reversed fluoride-induced promotion of autophagy. MHY1485 also recovered the downregulation of proliferative chondrocytes markers Sox9 and Type Ⅱ Collagen (Col2a1) induced by fluoride in ATDC5 cells. Taken together, our result demonstrate that fluoride suppressed proliferation and facilitated autophagy via PI3K/AKT/mTOR signaling pathway in chondrogenesis.

Non-endemic skeletal fluorosis: Causes and associated secondary hyperparathyroidism (case report and literature review)

Skeletal fluorosis (SF) is endemic primarily in regions with fluoride (F)-contaminated well water, but can reflect other types of chronic F exposure. Calcium (Ca) and vitamin D (D) deficiency can exacerbate SF. A 51-year-old man with years of musculoskeletal pain and opiate use was hypocalcemic with secondary hyperparathyroidism upon manifesting recurrent long bone fractures. He smoked cigarettes, drank large amounts of cola beverage, and consumed little dietary Ca. Then, after 5 months of Ca and D₃ supplementation, serum 25(OH)D was 21 ng/mL (Nl, 30-100), corrected serum Ca had normalized from 7.8 to 9.4 mg/dL (Nl, 8.5-10.1), alkaline phosphatase (ALP) had decreased from 1080 to 539 U/L (Nl, 46-116), yet parathyroid hormone (PTH) had increased from 133 to 327 pg/mL (Nl, 8.7-77.1). Radiographs revealed generalized osteosclerosis and a cystic lesion in a proximal femur. DXA BMD Z-scores were +7.4 and +0.4 at the lumbar spine and "1/3" radius, respectively. Bone scintigraphy showed increased uptake in two ribs, periarticular areas, and proximal left femur at the site of a subsequent atraumatic fracture. Elevated serum collagen type I C-telopeptide 2513 pg/mL (Nl, 87-345) and osteocalcin >300 ng/mL (Nl, 9-38) indicated rapid bone turnover. Negative studies included hepatitis C Ab, prostate-specific antigen, serum and urine electrophoresis, and Ion Torrent mutation analysis for dense or high-turnover skeletal diseases. After discovering markedly elevated F concentrations in his plasma [4.84 mg/L (Nl, 0.02-0.08)] and spot urine [42.6 mg/L (Nl, 0.2-3.2)], a two-year history emerged of "huffing" computer cleaner containing difluoroethane. Non-decalcified histology of a subsequent right femur fracture showed increased osteoblasts and osteoclasts and excessive osteoid. A 24-hour urine collection contained 27 mg/L F (Nl, 0.2-3.2) and <2 mg/dL Ca. Then, 19 months after "huffing" cessation and improved Ca and D₃ intake, yet with persisting bone pain, serum PTH was normal (52 pg/mL) and serum ALP and urine F had decreased to 248 U/L and 3.3 mg/L, respectively. Our experience combined with 15 publications in PubMed concerning unusual causes of non-endemic SF where the F source became known (19 cases in all) revealed: 11 instances from high consumption of black tea and/or F-containing toothpaste, 1 due to geophagia of F-rich soil, and 7 due to "recreational" inhalation of F-containing vapors. Circulating PTH measured in 14 was substantially elevated in 2 (including ours) and mildly increased in 2. The severity of SF in the cases reviewed seemed to reflect cumulative F exposure, renal function, and Ca and D status. Several factors appeared to influence our patient's skeletal disease: i) direct anabolic effects of toxic amounts of F on his skeleton, ii) secondary hyperparathyroidism from degradation-resistant fluorapatite bone crystals and low dietary Ca, and iii) impaired mineralization of excessive osteoid due to hypocalcemia.

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.

Characterization of Disinfection By-Products Levels at an Emergency Surface Water Treatment Plant in a Refugee Settlement in Northern Uganda

The reliance on chlorination in humanitarian operations has raised concerns among practitioners about possible health risks associated with disinfection by-products; however, to date, there has not been an evaluation of disinfection by-product (DBP) levels in an emergency water supply intervention. This study aimed to investigate DBP levels at a surface-water treatment plant serving a refugee settlement in northern Uganda using the colorimetric Hach THM Plus Method. The plant had two treatment processes: (1) Simultaneous clarification–chlorination (“rapid treatment”); and (2) pre-clarification and chlorination in separate tanks (“standard treatment”). For both standard (n = 17) and rapid (n = 3) treatment processes, DBP levels in unique parcels of water were tested at 30 min post-chlorination and after 24 h of storage (to simulate what refugees actually consume). DBP levels after 24 h did not exceed the World Health Organization (WHO) guideline limit of 300 ppb equivalent chloroform, either for standard treatment (mean: 85.1 ppb; 95% confidence interval (C.I.): 71.0–99.1 ppb; maximum: 133.7 ppb) or for rapid treatment (mean: 218.0 ppb; 95% C.I.: 151.2–284.8; maximum: 249.0 ppb). Observed DBPs levels do not appear to be problematic with respect to the general population, but may pose sub-chronic exposure risks to specifically vulnerable populations that warrant further investigation.