Duan Q, Jiao J, Chen X, Wang X. Association between water fluoride and the level of children’s intelligence: a dose-response meta-analysis. Public health. 2018 Jan;154:87-97. doi: 10.1016/j.puhe.2017.08.013.
OBJECTIVES: Higher fluoride concentrations in water have inconsistently been associated with the levels of intelligence in children. The following study summarizes the available evidence regarding the strength of association between fluoridated water and children’s intelligence.
STUDY DESIGN: Meta-analysis.
METHODS: PubMed, Embase, and Cochrane Library databases were systematically analyzed from November 2016. Observational studies that have reported on intelligence levels in relation to high and low water fluoride contents, with 95% confidence intervals (CIs) were included. Further, the results were pooled using inverse variance methods. The correlation between water fluoride concentration and intelligence level was assessed by a dose-response meta-analysis.
RESULTS: Twenty-six studies reporting data on 7258 children were included. The summary results indicated that high water fluoride exposure was associated with lower intelligence levels (standardized mean difference : -0.52; 95% CI: -0.62 to -0.42; P < 0.001). The findings from subgroup analyses were consistent with those from overall analysis. The dose-response meta-analysis suggested a significant association between water fluoride dosage and intelligence (P < 0.001), while increased water fluoride exposure was associated with reduced intelligence levels.
CONCLUSIONS: Greater exposure to high levels of fluoride in water was significantly associated with reduced levels of intelligence in children. Therefore, water quality and exposure to fluoride in water should be controlled in areas with high fluoride levels in water.
Krishna KumarYadav et al. Fluoride contamination, health problems and remediation methods in Asian groundwater: A comprehensive review. Ecotoxicology and Environmental Safety Volume 182, 30 October 2019, 109362
In low concentration, fluoride is considered a necessary compound for human health. Exposure to high concentrations of fluoride is the reason for a serious disease called fluorosis. Fluorosis is categorized as Skeletal and Dental fluorosis. Several Asian countries, such as India, face contamination of water resources with fluoride. In this study, a comprehensive overview on fluoride contamination in Asian water resources has been presented. Since water contamination with fluoride in India is higher than other Asian countries, a separate section was dedicated to review published articles on fluoride contamination in this country. The status of health effects in Asian countries was another topic that was reviewed in this study. The effects of fluoride on human organs/systems such as urinary, renal, endocrine, gastrointestinal, cardiovascular, brain, and reproductive systems were another topic that was reviewed in this study. Different methods to remove fluoride from water such as reverse osmosis, electrocoagulation, nanoﬁltration, adsorption, ion-exchange and precipitation/coagulation were introduced in this study. Although several studies have been carried out on contamination of water resources with fluoride, the situation of water contamination with fluoride and newly developed technology to remove fluoride from water in Asian countries has not been reviewed. Therefore, this review is focused on these issues: 1) The status of fluoride contamination in Asian countries, 2) health effects of fluoride contamination in drinking water in Asia, and 3) the existing current technologies for defluoridation in Asia.
“The results from a 2018 study (Rodeheffer et al., 2018) measuring the cognitive and decision-making performances of submariners exposed to elevated CO2 undermined the attempts to portray CO2 as a brain-function-impairing toxin. In the study, subjects were exposed to 3 CO2 conditions: 600, 2500, and 15000 ppm. The results indicated there were “no significant differences” in how the subjects performed for any of the CO2 exposure levels.” click here
Raquel S. Chaves, Catarina S. Vítor V. Cardoso, Maria J. Benoliel Miguel M. Santos. Hazard and mode of action of disinfection by-products (DBPs) in water for human consumption: Evidences and research priorities. Comparative Biochemistry and Physiology Part C: Toxicology & Pharmacology, Volume 223, September 2019, Pages 53-61
Disinfection of water system is an essential strategy to protect human health from pathogens and prevent their regrowth during water distribution, but the reaction of disinfectant agents with organic matter can lead to the formation of disinfection by-products (DBPs). Given their widespread occurrence, potential human health impacts and (eco)toxicity associated with exposure to DBPs are of particular interest due to their potential carcinogenicity and vary non-carcinogenic effects, such as endocrine disruption. Understanding the public health implications of this emerging issue is crucial for societies and decision-makers, supporting more effective water safety plans. Here, we review the recent literature on the effects of DBPs presented in drinking water and treated swimming pools water, focusing particularly in unregulated compounds and the putative underlying mode of action, linking the available data with adverse health outcomes. Overall, the majority of studies highlight the limited knowledge in the understanding of the underlying mode of action of DBPs. Yet, available evidences indicate that different signaling pathways seem to be involved in the adverse outcomes associated with distinct DBPs classes. The main knowledge gaps in this field are also identified, and future research priorities discussed.
S. Stanley Young and Warren B. Kindzierski. Evaluation of a meta-analysis of air quality and heart attacks, a case study. Critical Reviews in Toxicology https://doi.org/10.1080/10408444.2019.1576587
It is generally acknowledged that claims from observational studies often fail to replicate. An exploratory study was undertaken to assess the reliability of base studies used in meta-analysis of short-term air quality-myocardial infarction risk and to judge the reliability of statistical evidence from meta-analysis that uses data from observational studies. A highly cited meta-analysis paper examining whether short-term air quality exposure triggers myocardial infarction was evaluated as a case study. The paper considered six air quality components – carbon monoxide, nitrogen dioxide, sulphur dioxide, particulate matter 10 lm and 2.5 lm in diameter (PM10 and PM2.5), and ozone. The number of possible questions and statistical models at issue in each of 34 base papers used were estimated and p-value plots for each of the air components were constructed to evaluate the effect heterogeneity of p-values used from the base papers. Analysis search spaces (number of statistical tests possible) in the base papers were large, median 1⁄4 12,288 (interquartile range 1⁄4 2496 ” 58,368), in comparison to actual statistical test results presented. Statistical test results taken from the base papers may not provide unbiased measures of effect for meta-analysis. Shapes of p-value plots for the six air components were consistent with the possibility of analysis manipulation to obtain small p-values in several base papers. Results suggest the appearance of heterogeneous, researcher-generated p-values used in the meta-analysis rather than unbiased evidence of real effects for air quality. We conclude that this meta-analysis does not provide reliable evidence for an association of air quality components with myocardial risk.
Sharma D, Singh A, Verma K, Paliwal S, Sharma S, Dwivedi J. Fluoride: A review of pre-clinical and clinical studies. Environmental toxicology and pharmacology. 2017 Dec;56:297-313. doi: 10.1016/j.etap.2017.10.008.
Fluoride is ubiquitous in environment and profound in bones, teeth and calcified tissues of human body. Fluoride has been the topic of regular discussion and investigations. Besides its toxicity, fluoride has also been examined for its beneficial effects like prevention and treatment of tooth decay, microbial infection, inflammation, cancer, occurrence of renal stone and many more. Since last many decades, several efforts have been made at pre-clinical and clinical level to understand role of fluoride in biological system. The present review gives a brief account of prevalence, sources of fluoride toxicity and pre-clinical and clinical studies carried out on effects of fluoride in last six decades.
Hewavithana PB, Jayawardhane WM, Gamage R, Goonaratna C. Skeletal fluorosis in Vavuniya District: an observational study. The Ceylon medical journal. 2018 Sep 30;63(3):139-142.
BACKGROUND: The WHO recommended safe upper limit for fluoride in drinking water is 1.5 mg/l. Groundwater sources in many parts of Sri Lanka often exceed this limit. The high fluoride content of groundwater and high environmental temperatures in Vavuniya District predispose to pre-skeletal fluorosis and skeletal fluorosis in adults.
OBJECTIVES: To identify residents of Vavuniya District with clinical features of pre-skeletal and skeletal fluorosis; to describe their clinical, biochemical and radiographic features; to determine the fluoride content of blood and urine in individuals with established diagnoses, and of their drinking water.
METHODS: In 98 volunteers we detected 60 with clinical features of pre-skeletal and skeletal fluorosis. Clinical examination, biochemical and radiographic investigations were performed. Forty four with confounding factors were excluded. The balance 16 had radiographic investigation for fluoride bone disease, and assessment of clinical features for pre-skeletal fluorosis. The radiographic criteria of skeletal fluorosis were trabecular haziness, osteosclerosis, osteophytes, cortical thickening and ligamentous or muscle attachment ossification. All 16 had “spot” samples of 15 ml of venous blood taken for biochemical tests and fluoride estimation; and 30 ml of urine, and water from 16 dug wells for fluoride.
RESULTS: The 16 selected (11 males) had BMI between 20.6 and 31.9 kg/m2, and were between 22 and 84 years (x̅ = 59.9 + 20.4). They used water from domestic dug wells for drinking. All had adequate renal function. All serum and urine samples had raised fluoride levels way above the reference ranges for serum (0.02 – 0.18 mg/l) and urine (0.6 – 2.0 mg/l). The 16 water samples showed a mean fluoride content of 2.90 +0.93 mg/l.
INTERPRETATION: In a cohort of 60 individuals in Vavuniya with symptoms suggestive of skeletal fluoride toxicity, 6 had skeletal fluorosis, 10 had pre-skeletal fluorosis, and groundwater sources had fluoride levels much higher than WHO recommended upper limit for drinking water. Residents in Vavuniya are predisposed to pre-skeletal and skeletal fluorosis. All 16 had been misdiagnosed as various types of arthritis.