Reproductive toxicity parameters and biological monitoring in occupationally and environmentally boron-exposed persons in Bandırma, Turkey

Cytotoxicity, genotoxicity, oxidative stress, apoptosis, and cell cycle arrest in human Sertoli cells exposed to boric acid

BACKGROUND

Boron, which is used in a range of industries worldwide, is an essential micronutrient for plants and "probably essential" for humans. Conflicting reports have been published regarding the toxicity of boron compounds. Moreover, boric acid and sodium borates are classified as toxic to development and reproduction in the European Union-Classification, Labelling and Packaging Regulation (EU-CLP Regulation). The scope of our study was to ascertain whether boric acid caused the cytotoxic and genotoxic effects, as well as oxidative stress, apoptosis, and cell cycle profiles on human Sertoli cells.

METHODS

The possible toxic effects of boric acid on human Sertoli cells were investigated by in vitro methods. The cellular viability and DNA damage were examined by neutral red uptake and alkaline comet assay, respectively. Oxidative stress, apoptosis, and cell cycle arrest profiles were analyzed by flow cytometry.

RESULTS

Boric acid was neither cytotoxic nor genotoxic in a wide concentration range (0.5-1000 μM) on human Sertoli cells. No significant difference in the DNA damage was observed between boric acid-treated and control groups (p > 0.05). Boric acid did not stimulate oxidative stress, apoptosis, and cell cycle arrest within the tested concentrations.

CONCLUSION

Our study provides novel insights into the influences of boric acid on human Sertoli cells which are used as a model in male reproductive toxicity studies. The concentrations tested in our study were extremely higher than the blood and semen boron levels reported in epidemiological studies.

Combination of trehalose and low boron in presence of decreased glycerol improves post-thawed ram sperm parameters: A model study in boron research

BACKGROUND

Sperm cryopreservation has been widely used in the field of reproductive biotechnology. It applies to certain males of economic and scientific values, including livestock breeds or endangered animal species. The development of a semen extender with a low cryoprotectant concentration and an appropriate amount of trehalose and boron can prevent the deterioration of sperm parameters.

OBJECTIVE

The main goal of this study is to establish a suitable ram extender model, by examining different combinations of high (5%) and low (3%) glycerol concentrations (to reduce its toxic effects on sperm freezing), a fixed amount of trehalose and an increased dose of boron to prevent the deterioration of sperm parameters, and investigate the levels of gene expressions.

MATERIALS AND METHODS

The Merino ram ejaculates were collected. The collected ejaculates providing the defined criteria were pooled. The pooled ejaculates were divided into eight aliquots and diluted with the Tris extender including different combinations of glycerol (5% and 3%) and boron (0.25, 0.5, and 1 mm) concentrations and a fixed amount of trehalose, then frozen. After freeze-thawing process, sperm motility, mitochondrial membrane activity, plasma membrane integrity, acrosomal membrane integrity, DNA damage (single cell gel electrophoresis (COMET) and TUNEL assays) as well as NAD(P)H quinone oxyreductase (NQO1), glutamate-cycteine ligase (GCLC), and glutathione S-transferase (GSTP1) for molecular mechanisms of sperm cell response to oxidative stress were assessed for different extender groups following freeze-thawing process: 5% glycerol + 0 mm boron (G5B0.00), 5% glycerol + 0.25 mm boron (G5B0.25), 5% glycerol + 0.5 mm boron (G5B0.50), 5% glycerol + 1 mm boron (G5B1.00), 3% glycerol + 0 mm boron (G3B.00), 3% glycerol + 0.25 mm boron (G3B0.25), 3% glycerol + 0.5 mm boron (G3B0.50), and 3% glycerol + 1 mm boron (G3B1.00).

RESULTS

G3B0.25 presented higher percentages of subjective motility, mitochondrial activity, and viability of spermatozoa comparing with G5B0.00 and groups with boron. Supplementation of 0.25 mm boron with and without trehalose (G3B0.25 and G5B0.25) showed higher acrosome integrity, compared with G5B0.00, G5B1.00, G3B0.50, and G3B1.00. For TUNEL analysis, G3B1.00 showed the highest DNA integrity among the experimental groups which was statistically significant only with G5B0.50 (p < 0.05). The mRNA levels of NQO1 were significantly decreased in G5B1.00, G3B0.50, and G3B1.00, when compared to G5B0.00. In comparison with G5B0.00, supplementation of 1 mm boron with and without trehalose had significantly lower expression of GCLC. The level of GSTP1 gene was significantly lower (approximately threefold) in G3B1.00, compared to G5B0.00 (p < 0.05).

DISCUSSION AND CONCLUSION

It can be assumed that the increase of the boron concentration in the extender may have important adverse effects on sperm parameters and antioxidant gene expression after thawing. The results obtained from this study will help to understand the toxicity limits of boron and eliminate the toxicity of glycerol in studies of gametes and tissue freezing. Therefore, it can be concluded that the use of sufficient boron can decrease cryodamages of cryopreservation of mammalian spermatozoa as well tissue engineering.

Toxicity of boric acid, borax and other boron containing compounds: A review

Boron, often in the form of boric acid, is widely used as a flame retardant in insulation products, and although humans ingest boron through food, high exposure may lead to unwanted health effects. We assessed the toxicity of boric acid, borax and other forms of boron, after inhalation, dermal and oral exposure. After oral exposure, boron is absorbed over the gastrointestinal tract. Intact skin seems to pose a more effective barrier to boron than compromised skin. Boron excretion seems to mainly occur via the urine, although after skin exposure boron has been demonstrated in bile and gastrointestinal contents. Inhalation toxicity data are sparse, but one animal study showed reduced foetal weight after inhalation of cellulose that had a boric acid content of 20%. Skin exposure to boric acid has proven fatal in some cases, and the range of toxicity effects include abdominal as well as local effects on the skin. Fatalities from boric acid also have occurred after oral ingestion, and the endpoints in animals are weight loss and reproductive toxicity. Concerning genotoxicity studies, the overall picture indicates that boron-containing compounds are not genotoxic. There was no evidence of the carcinogenicity of boric acid in a 2-year study in mice.

Development of FTIR Spectroscopy Methodology for Characterization of Boron Species in FCC Catalysts

Fluid Catalytic Cracking (FCC) has maintained its crucial role in refining decades after its initial introduction owing to the flexibility it has as a process as well as the developments in its key enabler, the FCC catalyst. Boron-based technology (BBT) for passivation of contaminant metals in FCC catalysts represents one such development. In this contribution we describe Fourier Transform Infrared Spectroscopy (FTIR) characterization of boron-containing catalysts to identify the phase and structural information of boron. We demonstrate that FTIR can serve as a sensitive method to differentiate boron trioxide and borate structures with a detection limit at the 1000 ppm level. The FTIR analysis validates that the boron in the FCC catalysts studied are in the form of small borate units and confirms that the final FCC catalyst product contains no detectable isolated boron trioxide phase. Since boron trioxide is regulated in some parts of the world, this novel FTIR methodology can be highly beneficial for further FCC catalyst development and its industrial application at refineries around the world. This new method can also be applied on systems beyond catalysts, since the characterization of boron-containing materials is needed for a wide range of other applications in the fields of glass, ceramics, semiconductors, agriculture, and pharmaceuticals.

Effects of Boron on Cytotoxicity, Apoptosis, and Cell Cycle of Cultured Rat Sertoli Cells In vitro

The present study aimed to investigate the effects of the administration of boron on viability, apoptosis, and cell cycle of primary rat Sertoli cells (SCs) in vitro. SCs were aseptically isolated from 18-22-day-old male Sprague-Dawley (SD) rats. SCs were identified with immunofluorescence using anti-vimentin antibody. Further, to investigate the effects of boron on Sertoli cells, SCs of the boron treatment group were exposed to different concentrations (0.25, 0.5, 1, 5, 10, 40, and 80 mmol/L) of boric acid. Using MTT and Cell Counting Kit-8 assays, the impact of boron on SCs viability was analyzed. Cell apoptosis and cycle of SCs were analyzed using flow cytometry. A concentration of 0.5 mmol/L boric acid resulted in the highest viability and lowest necrosis and apoptosis. Above this concentration (even 1.0 mmol/L) showed lower viability and higher levels of necrosis and apoptosis. Administration of < 0.5 mmol/L boron significantly promoted the viability of Sertoli cells (P < 0.01); however, the exposure to high dose (> 10 mmol/L) of boron exhibited significant adverse effects on Sertoli cells (P < 0.01) and even toxic effects, inhibiting cell viability compared to the control group. Flow cytometry analysis showed that treatment with 0.5 mmol/L of boron significantly inhibited the apoptosis of Sertoli cells and the proportion of cells in S and G₂/M phases was markedly increased; however, a higher concentration of 40 and 80 mmol/L of boron promoted Sertoli cell apoptosis and cells were completely arrested at G₀/G₁ phase. Boron at doses below 0.5 mmol/L could significantly improve the viable capacity of testicular Sertoli cells in vitro and inhibit their apoptosis. However, high dose of boron (at a concentration higher than 5.0 mmol/L) exhibited noticeable toxic effects, inhibiting cell viability, accelerating apoptosis of Sertoli cells, and arresting cell cycle at G0/G1 phase.

Ecological risk assessment of trace metals and comprehensive contamination indicators in the coastal waters of Macao, South China Sea

Few systematic and scientific assessments have been conducted on marine environmental quality in the coastal waters of Macao, a major city in the Pearl River Delta, China. In this study, we investigated the spatial distribution of trace metals (TMs) and comprehensive contamination indicators of marine water in Macao and evaluated their ecological risks. The total amount of typical TMs (∑TMs) in surface water ranged from 2.71 μg/L to 201 μg/L. ∑TMs (Hg, As, and Cd) in sediments ranged from 0.34 mg/kg to 54.8 mg/kg. TM contamination in surface water was influenced by spatial position and tidal current direction. The spatial distribution and correlation analysis of TMs and comprehensive contamination indicators were assessed, and ecological risk assessment indicated that the surface water and sediments in coastal waters of Macao are of relatively good quality, although high sulfide levels could be detected in surface water.

Effects of boric acid on cell death and oxidative stress of mouse TM3 Leydig cells in vitro

BACKGROUND

Boron (B) is an abundant element on earth and presents at physiological pH in the form of boric acid (BA). It has both positive and negative effects on biological systems. BA and sodium borates have been considered as being toxic to the reproduction system in animal experiments. Unfortunately, the molecular mechanism underlying the toxic effects of BA is not fully understood.

METHODS

Here, we demonstrate the influence of BA on mouse TM3 Leydig cells which are male reproductive system cells targeted by BA exposure. The cytotoxicity was evaluated by MTT and NRU assays. Annexin V-FITC/PI double staining kit, mitochondria membrane potential (ΔΨm) assay kit with JC-1 and caspase-3 colorimetric assay kit were used to indicate the cell death pathway. To estimate the role of oxidative stress in BA induced toxicity, glutathione (GSH) level, catalase (CAT) and superoxide dismutase (SOD) activities were measured manually.

RESULTS

The cell viability assays showed that BA was not cytotoxic within the tested concentrations up to 1000 μM. Sub-toxic concentrations were used for detecting oxidative stress status. BA exposure was significantly reduced GSH level at 1000 μM and CAT activity in a concentration-dependent manner. However, SOD activity was increased at the tested concentrations (100-1000 μM). Moreover, ΔΨm was significantly decreased at 500 and 1000 μM of BA, while caspase-3 activity was not changed apparently.

CONCLUSION

These findings demonstrated that BA is not cytotoxic and apoptotic but may slightly induces oxidative stress in TM3 Leydig cells at higher concentrations.

Effects of boron compounds on human reproduction

Because of the high pK_a of boric acid, inorganic borates, when taken up by the human or animal organism, exist in the body almost exclusively in the form of non-dissociated boric acid. Therefore, the variety of inorganic boron compounds is commonly addressed in the toxicological literature as "boron" (B). There is a discussion concerning categorisation of inorganic boron compounds as reproductive toxins. Boron treatment of rats, mice and dogs was dose-dependently associated with testicular toxicity, characterised by inhibited spermiation at lower dose levels and by reduction of epididymal sperm counts at higher dose levels. The NOAEL for such fertility effects of boric acid in male rats (oral feeding, Sprague Dawley strain) was evaluated to be 17.5 mg B/kg bw per day. As far as developmental toxicity is concerned, oral dosing of 9.6 mg B/kg bw daily to female pregnant Sprague Dawley rats remained without effects, with foetal skeletal effects observed at higher doses. Therefore, 9.6 mg B/kg bw (oral dosing) was evaluated as NOAEL for developmental effects of boric acid. The blood level in rats, equivalent to this NOAEL, is 1270 ng B/g. As far as B-exposed humans are concerned, field studies on the effect of boron on human reproduction are possible only in a few boron-rich geographical areas. Published field studies were conducted in China's Liaoning province, the Argentinian Andes and Western Anatolia/Turkey. Particularly relevant are studies on occupationally B-exposed groups, because the potential exposure to boron is much higher in occupational compared to environmental settings. Comparison of estimated daily B exposure levels in humans and actually measured B blood levels confirms the preference of biomonitoring for exposure assessment in environmental and occupational studies. A boron blood level scaling shows that the levels of high occupational B exposures reported in China and in Turkey are compatible. Compared to the experimental B blood levels at boron-related NOAELs for male fertility and for developmental toxicity in rats, the human blood level means of the highest occupational exposure groups in China and in Turkey are lower by factors of > 4 and > 2, respectively. Basically, concentrations of B within the body that exert reproductive toxicity in humans are not reached under the conditions of human normal handling and use, including conditions of extreme occupational exposures. In consequence, all relevant results of studies into human reproductive toxicity of B are basically negative. Considering the effective doses, there is no scientific contradiction between experimental and human results of B reproductive toxicity.

Effects of boric acid feeding on the oxidative stress parameters in testes, sperm parameters and DNA damage in mice

This study was aimed to determine the effects of boric acid on oxidative stress, testicular tissue and spermatozoon DNA. Experiments were performed with Swiss Albino mice divided equally into two groups based on the tratment period: one for 4 and the other for 6-week duration. These groups were further divided into subgroups as Control and those administered daily at oral doses of 115 mg/kg, 250 mg/kg and 450 mg/kg of boric acid. Then, testicular tissue were examined postmortem and analyzed using ex-vivo biochemical tools for oxidative stress, spermatozoon membrane integrity, sperm motility and live cell rate (%). In both 4 and 6-week groups, v. seminalis weight, membrane integrity, motility, live cells and GSH levels exhibited a decreasing trent compared to the controls. In addition, 6-week group had a decrease in SOD level. MDA level was higher in controls in both 4 and 6-week groups. Spermatozoon DNA was intact in the 4-week group, but damaged in the 6-week group, and the degree of the damage dependent on the administered dose. Boric acid induces oxidative stress in testicular tissue, and its long-term application (only 6 weeks) caused damage in spermatozoon DNA.

Dietary boron supplementation enhances sperm quality and immunity through influencing the associated biochemical parameters and modulating the genes expression at testicular tissue

INTRODUCTION

Dietary boron improves immune and antioxidant status and calcium metabolism in mammals. However, till date the effects of dietary boron supplementation on male reproduction, especially on sperm production and sperm quality in farm animals are not documented.

OBJECTIVE

The present study was aimed to investigate the influence of dietary boron on semen production, semen quality, immunity and molecular changes in the testis, blood and seminal plasma and to assess the interrelationship with other minerals in male goats.

METHODOLOGY

The study was conducted in 21 adult male goats divided into 3 groups (control, boron and selenium supplemented groups, n = 7 each). In boron group, boron was supplemented at 40 ppm and in selenium group, selenium was supplemented at 1 ppm over and above the basal level. In control group, only the basal diet was fed without supplementary boron or selenium. The feeding trial was carried out for 60 days. Selenium was taken as a positive control for the dietary boron supplementation experiment. Following feeding trials, the sperm concentration, kinematics and functional attributes, immunity and molecular level changes in the testis, biomolecular changes in the blood and seminal plasma and also interrelationship with other minerals were studied.

RESULTS

The average sperm concentration (million/ml) and the total sperm production (million/ejaculate) were significantly (p < 0.05) increased in boron supplemented group when compared to selenium and control groups. The boron levels in blood plasma (r = 0.65) and seminal plasma (r = 0.54) showed a positive correlation with sperm progressive motility. Blood and seminal plasma metabolic biomarker namely, aspartate aminotransferase (AST) (p < 0.01) was significantly lower in the boron and selenium supplemented group than control, while alanine aminotransferase (ALT) (p < 0.05) was significantly lower in the boron supplemented group than selenium and control group. There was a significant increase in the mRNA expression of serine proteinase inhibitor (SERPIN) and interferon γ (IFNγ) in the testis of boron supplemented than the control group. Boron supplementation up-regulated the immune-regulatory gene, interleukin 2 (IL2) and antioxidant gene, catalase (CAT) in the peripheral blood mononuclear cells (PBMC). On contrary, toll-like receptor 2 (TLR2) mRNA expression was significantly (p < 0.05) down-regulated in boron and selenium supplemented groups.

CONCLUSION

The study revealed that dietary boron supplementation increased the sperm output, sperm motility and enhanced the immune and antioxidant defense capacity in male goats. The improved semen quality can be attributed to enhanced expression of testicular SERPIN, a crucial protein for the regulation of spermatogenesis process.

Boron-rich diet may regulate blood lipid profile and prevent obesity: A non-drug and self-controlled clinical trial

BACKGROUND

Boron is an element commonly found in nature. The main boron source for organisms is through food and drinking water. In recent years, it is suggested that the "boron-rich diet" can affect human health positively. However, more detailed studies are needed.

OBJECTIVE

The aim of this study was to examine the effect of increased dietary boron intake on some biochemical parameters in humans.

MATERIAL AND METHODS

Thirteen healthy women consumed diets containing 10 mg more boron than their routine diet for one month. This boron intake was provided with the increase of boron-rich foods such as dried fruits, avocado, and nuts in the diet. Some biochemical and hematologic parameters were determined in blood, urine and saliva samples taken before and after a boron-rich diet.

RESULTS

Serum, salivary, and urine boron concentrations increased 1.3, 1.7, 6.0 fold, respectively. The most significant clinically change was found in the lipid profile. Serum total, LDL, VLDL cholesterol, and triglyceride levels decreased significantly. Body weight, body fat weight, and Body Mass Index also decreased. Significant changes in serum TSH and salivary buffering capacity were also found.

CONCLUSION

Increasing the intake of boron through dietary means might contribute to beneficial effects on lipid metabolism, obesity, and thyroid metabolism; salivary boron may reflect serum boron; and boron may be used as a cariostatic agent in dentistry. An increased intake of other dietary factors such as fiber, potassium, iron, vitamin A, and vitamin E in the boron-rich foods might have been responsible of the effects described. To our knowledge, this study is the first clinical study in which dietary boron intake is increased via foods.

Environmental boron exposure does not induce DNA damage in lymphocytes and buccal cells of females: DNA damage in lymphocytes and buccal cells of boron exposed females

Boron (B) compounds are essential for plants and animals and beneficial for humans in nutritional amounts. I animals and humans increasing evidence have shown beneficial effects on B compounds on nutrition and on antioxidant status. The genotoxic effects of environmental B exposure in women living in boron-rich and boron-poor areas was examined in this study. For this purpose, the DNA damage in the lymphocytes and buccal cells of females were assessed by Comet and micronucleus (MN) assays respectively. No significant difference was observed in the DNA damage of the lymphocytes of B exposed groups of female volunteers in Comet assay. Even buccal micronucleus (MN) frequency observed in the high exposure group was significantly lower than the low exposure group (p < 0.05). The results of this study came to the same conclusions of the previous studies that boron does not induce DNA damage even under extreme exposure conditions.

Is There an Association Between Extreme Levels of Boron Exposure and Decrease in Y:X Sperm Ratio in Men? Results of an Epidemiological Study

Objectives

A negative association between Y:X sperm ratio and high levels of boron exposure was suggested in an epidemiological study conducted in boron mining areas of China. That study, however, was criticized by many authors due to some weaknesses in the study design. The present epidemiological study was designed to corroborate or refute the above-mentioned negative association between boron exposure and Y:X sperm ratio in men.

Materials and Methods

The study was conducted in a boric acid production zone in Bandırma. One hundred sixty-three male workers voluntarily participated in our study. The workers employed in the boric acid production facilities were assigned as the exposed workers (n=86). The control group was composed of workers employed in the steam power plant, energy supply unit, demineralized water plant, mechanical workshop, etc. (n=77). Blood and semen samples were sampled from the participating workers at the end of the work shift. Y:X sperm ratio in semen samples was determined by fluorescence in situ hybridization. Boron concentrations in semen and blood samples were determined using inductively coupled plasma-mass spectrometry.

Results

Boron-mediated adverse effect on the Y:X sperm ratio was not determined in workers in our study even under extreme occupational exposure conditions. The results of our study refute the negative association between Y:X sperm ratio and high levels of boron exposure that was suggested in a previously published epidemiological study conducted in boron mining areas of China.

Conclusion

The results of our study indicate that boron-mediated adverse effects on the Y:X sperm ratio do not seem possible even under occupational boron exposure conditions.

Acute exposure to boron in Nile tilapia (Oreochromis niloticus): Median-lethal concentration (LC50), blood parameters, DNA fragmentation of blood and sperm cells

Recently, Boron (B) contamination of aquatic ecosystem has received considerable critical attention due to its toxic effects at high concentrations on plants as well as animals. Previous studies on toxic effects of B have not dealt with DNA damages in blood and sperm cells of Nile tilapia (Oreochromis niloticus), together with blood parameters. This study consisted of two successive experiments purposes to determine these findings, including the median-lethal concentration (LC₅₀) of B for Nile tilapia. In the first one, at 96 h, LC₅₀ of B for Nile tilapia was 141.42 mg L^-1 B. In the second one, Nile tilapia were treated with five elevated B concentrations (1, 5, 25, 50 and 100 mg L^-1 B) and hematological, serum biochemical parameters, and DNA damages of Nile tilapia in these treatments were determined comparing with the control after 14 days of exposure. Hematological parameters (red blood cell count, hematocrit, and hemoglobin) were similar to each other in all groups while serum biochemical parameters (glucose, total protein, cholesterol, alkaline phosphatase, glutamic oxaloacetic transaminase, and glutamic pyruvic transaminase) in B treatments, especially in 50 and 100 mg L^-1 B groups, were found significantly higher (P < 0.05). DNA fragmentation was detected in all blood cells in ≥25 mg L^-1 B treatments, while all sperm cells in 100 mg L^-1 B treatments. These results demonstrated the harmful effects of B at high concentration (50 and 100 mg L^-1 B) on the DNA integrity of blood and sperm cells, and also the serum biochemical parameters.

Structural and biological overview of Boron-containing amino acids in the medicinal chemistry field

Amino acids are the basic structural units of proteins as well as the precursors of many compounds with biological activity. The addition of boron reportedly induces changes in the chemical-biological profile of amino acids.

METHODS

We compiled information on the biological effect of some compounds and discuss the structure-activity relationship of the addition of boron. The specific focus presently is on borinic derivatives of α-amino acids, the specific changes in biological activity caused by the addition of a boron-containing moiety, and the identification of some attractive compounds for testing as potential new drugs.

RESULTS

Borinic derivatives of α-amino acids have been widely synthesized and tested as potential new therapeutic tools. The B-N (1.65 A°) or B-C (1.61 A°) or B-O (1.50 A°) bond is often key for the stability at different pHs and temperatures and activity of these compounds. The chemical features of synthesized derivatives, such as the specific moieties and the logP, polarizability and position of the boron atom are clearly linked to their pharmacodynamic and pharmacokinetic profiles. Some mechanisms of action have been suggested or demonstrated, while those responsible for other effects remain unknown.

CONCLUSION

The increasing number of synthetic borinic derivatives of α-amino acids as well as the recently reported crystal structures are providing new insights into the stability of these compounds at different pHs and temperatures, their interactions on drug targets, and the ring formation of five-membered heterocycles. Further research is required to clarify the ways to achieve specific synthesis, the mechanisms involved in the observed biological effect, and the toxicological profile of this type of boron-containing compounds (BCCs).

Blood boron levels and anthropometric measurements in prepubertal children

This study was conducted to assess the blood boron levels (BBL) in prepubertal children in the West and Central Anatolia regions of Turkey and its relationship with chosen anthropometric measurements. A multistage sampling design that combined multicluster (West Anatolia vs. Central Anatolia regions and rural vs. urban residents) and simple random sampling methods were used for the sample selection. BBL was measured using inductively coupled plasma mass spectrometry. Weight, height, mid-arm circumference, and triceps skinfold thickness were measured. Z-scores for weight-for-age, height-for-age, and body mass index (BMI)-for-age were calculated. Furthermore, arm-muscle area, arm-fat area, and fat percentage were measured. This study enrolled 2126 children, of whom 50.7% were male. The mean age was 8.9 years. The mean concentration of BBL was 15.6 μg/L (interquartile range: 11.7-19.6 μg/L). Children in urban areas had significantly higher BBL than those in rural areas (17.2 ± 5.5 vs. 11.9 ± 4.6 μg/L; p < .001). Children in the West Anatolia region had significantly lower BBL than those in the Central Anatolia region (14.5 ± 5.9 μg/L vs. 17.8 ± 5.0 μg/L; p < .001). BBL was not affected by maternal education, occupation, sex, and anemia. BBL was found to be significantly lower in children with low BMI, low triceps skinfold thickness, low arm fat area, and low-fat percentage. Change in BBL was associated with the region and residence in Turkey. BBL differed between well-nourished and malnourished children. Further studies are needed to evaluate the relationship between anthropometry and BBL.

Impact of chromium and boron compounds on the reproductive function in rats

The purpose of this research is to study the process of mutagenesis and the reproductive function in male rats under separate and combined exposure to chromium and boron compounds. The experiment was conducted on two groups of animals. The first group was used to assess the ability of potassium dichromate and boric acid to induce mutation in germ and somatic cells under isolated and combined administration with the use of the dominant lethal mutations test and the micronuclei test in the polychromatophilic erythrocytes of the bone marrow. The second group was used to test the combined and separate effect of the compounds under consideration on the reproductive function of male rats during the spermatogenesis cycle. When used in specific doses, boron compounds are a promising means of preventing and correcting chromium-induced effects in chromium production facility workers and people who live in ecologically adverse regions.

Boric Acid Reduces the Formation of DNA Double Strand Breaks and Accelerates Wound Healing Process

Boron is absorbed by the digestive and respiratory system, and it was considered that it is converted to boric acid (BA), which was distributed to all tissues above 90 %. The biochemical essentiality of boron element is caused by boric acid because it affects the activity of several enzymes involved in the metabolism. DNA damage repair mechanisms and oxidative stress regulation is quite important in the transition stage from normal to cancerous cells; thus, this study was conducted to investigate the protective effect of boric acid on DNA damage and wound healing in human epithelial cell line. For this purpose, the amount of DNA damage occurred with irinotecan (CPT-11), etoposide (ETP), doxorubicin (Doxo), and H₂O₂ was determined by immunofluorescence through phosphorylation of H2AX^(Ser139) and pATM^(Ser1981) in the absence and presence of BA. Moreover, the effect of BA on wound healing has been investigated in epithelial cells treated with these agents. Our results demonstrated that H2AX^(Ser139) foci numbers were significantly decreased in the presence of BA while wound healing was accelerated by BA compared to that in the control and only drug-treated cells. Eventually, the results indicate that BA reduced the formation of DNA double strand breaks caused by agents as well as improving the wound healing process. Therefore, we suggest that boric acid has important therapeutical effectiveness and may be used in the treatment of inflammatory diseases where oxidative stress and wound healing process plays an important role.

Boric Acid Is Reproductively Toxic to Adult Xenopus laevis, but Not Endocrine Active

The potential reproductive and endocrine toxicity of boric acid (BA) in the African clawed frog, Xenopus laevis, was evaluated using a 30-day exposure of adult frogs. Adult female and male frogs established as breeders were exposed to a culture water control and 4 target (nominal) test concentrations [5.0, 7.5, 10.0, and 15 mg boron (B)/L, equivalent to 28.5, 42.8, 57.0, and 85.5 mg BA/L] using flow-through diluter exposure system. The primary endpoints measured were adult survival, growth (weight and snout-vent length [SVL]), necropsy data, reproductive fecundity, and development of progeny (F1) from the exposed frogs. Necropsy endpoints included gonad weight, gonado-somatic index (GSI), ovary profile (oocyte normalcy and stage distribution), sperm count, and dysmorphology. Endocrine endpoints included plasma estradiol (E2), testosterone (T), dihydrotestosteone (DHT), gonadal CYP 19 (aromatase), and gonadal 5α-reductase (5-AR). BA exposure to adult female X. laevis increased the proportion of immature oocytes (< stage II) in the ovaries of females, reduced sperm counts and increased sperm cell dysmorphology frequency in male frogs exposed to 15 mg B/L. No effects on the other general, developmental (F1), or endocrine endpoints were observed. Based on the results of the present study, the no observed adverse effects concentration (NOAEC) for the reproductive endpoints was 10 mg B/L; and 15 mg B/L for reproductive fecundity, F1 embryo larval development, and endocrine function. These results confirmed that although BA is capable of inducing reproductive toxicity at high concentrations, it is not an endocrine disrupting agent.

Subchronic and genetic safety evaluation of a calcium fructoborate in rats

A branded calcium fructoborate product, a nature-identical calcium salt of bis (fructose) ester of boric acid found in plants and a natural source of boron in the human diet and sold under the trade name FruiteX-B(®) Brand Calcium Fructoborate ("FrxB"), was evaluated in a 90-day dietary toxicity study and two genotoxicity studies. In the 90-day study, four groups of 10 male and 10 female Crl:SD CD(®) IGS rats were fed diets with FrxB admixtures of 0.56, 1.12, and 1.68% dietary concentration, providing mean overall daily intakes of FrxB in male rats of 385.8, 774.9, and 1161.3 mg/kg bw/day, and 392.1, 784.4, and 1171.1 mg/kg bw/day in female rats. There were no mortalities, no clinical or ophthalmologic signs, body weight, body weight gain, food consumption, food efficiency, Functional Observational Battery (FOB), or Motor Activity (MA) findings associated with the administration of FrxB. There were no adverse changes in hematology, coagulation, clinical chemistry, or urinalysis parameters in male or female rats considered the result of test substance administration. At necropsy, there were no macroscopic, histopathological findings, or organ weight changes deemed related to administration of the test substance. Under the conditions of this study, based on the toxicological endpoints evaluated, the no-observed-adverse-effect level (NOAEL) for FrxB in the diet was 1161.3 and 1171.1 mg/kg bw/day in male and female rats, respectively. Bacterial mutagenicity studies and a micronucleus test using Chinese hamster V79 cells demonstrated no mutagenic or genotoxic potential of the tested brand of calcium fructoborate.

Relationship Not Found Between Blood and Urine Concentrations and Body Mass Index in Humans With Apparently Adequate Boron Status

The impact of boron on the development of obesity remains controversial in the analysis of experimental and clinical data. The objective of this study was to investigate the relationship between blood and urine boron concentrations and obesity in normal, overweight, obese, and morbidly obese subjects in different age groups. A total of 105 subjects were categorized into 12 groups based on body mass index and three different age levels: as young adult (18 to 34 years old), adult (35 to 54 years old), and older adult (greater than 55 years old). Age, gender, body mass index, and blood and urine boron concentrations were recorded for each subject. There were 50 women and 55 men, with a mean age of 44.63 ± 17.9 years. Blood and urine boron concentrations were similar among the groups (p = 0.510 and p = 0.228, respectively). However, a positive correlation between age and blood boron concentration (p = 0.001) was detected in contrast to the presence of a negative correlation between age and urine boron concentration (p = 0.027). Multiple linear regression analysis showed that there was no significant relationship between gender, age, and quantitative values of body mass index for each subject, and blood and urine boron concentrations. Although the relationship between boron and obesity has not been confirmed, changes of blood and urine boron concentrations with age may have some physiologic sequences to cause obesity.

Protective Effect of Boric Acid on Oxidative DNA Damage In Chinese Hamster Lung Fibroblast V79 Cell Lines

OBJECTIVE

Many studies have been published on the antioxidative effects of boric acid (BA) and sodium borates in in vitro studies. However, the boron (B) concentrations tested in these in vitro studies have not been selected by taking into account the realistic blood B concentrations in humans due to the lack of comprehensive epidemiological studies. The recently published epidemiological studies on B exposure conducted in China and Turkey provided blood B concentrations for both humans in daily life and workers under extreme exposure conditions in occupational setting. The results of these studies have made it possible to test antioxidative effects of BA in in vitro studies within the concentra- tion range relevant to humans. The aim of this study was to investigate the protective ef- fects of BA against oxidative DNA damage in V79 (Chinese hamster lung fibroblast) cells. The concentrations of BA tested for its protective effect was selected by taking the blood B concentrations into account reported in previously published epidemiological studies. Therefore, the concentrations of BA tested in this study represent the exposure levels for humans in both daily life and occupational settings.

MATERIALS AND METHODS

In this experimental study, comet assay and neutral red uptake (NRU) assay methods were used to determinacy to toxicity and genotoxicity of BA and hydrogen peroxide (H2O2).

RESULTS

The results of the NRU assay showed that BA was not cytotoxic within the tested concentrations (3, 10, 30, 100 and 200 µM). These non-cytotoxic concentrations were used for comet assay. BA pre-treatment significantly reduced (P<0.05, one-way ANOVA) the DNA damaging capacity of H2O2 at each tested BA concentrations in V79 cells.

CONCLUSION

Consequently, pre-incubation of V79 cells with BA has significantly reduced the H2O2-induced oxidative DNA damage in V79 cells. The protective effect of BA against oxidative DNA damage in V79 cells at 5, 10, 50, 100 and 200 μM (54, 108, 540, 1080, and 2161 ng/ml B equivalents) concentrations was proved in this in vitro study.

Assessing the reproductive health of men with occupational exposures

The earliest report linking environmental (occupational) exposure to adverse human male reproductive effects dates back to1775 when an English physician, Percival Pott, reported a high incidence of scrotal cancer in chimney sweeps. This observation led to safety regulations in the form of bathing requirements for these workers. The fact that male-mediated reproductive harm in humans may be a result of toxicant exposures did not become firmly established until relatively recently, when Lancranjan studied lead-exposed workers in Romania in 1975, and later in 1977, when Whorton examined the effects of dibromochloropropane (DBCP) on male workers in California. Since these discoveries, several additional human reproductive toxicants have been identified through the convergence of laboratory and observational findings. Many research gaps remain, as the pool of potential human exposures with undetermined effects on male reproduction is vast. This review provides an overview of methods used to study the effects of exposures on male reproduction and their reproductive health, with a primary emphasis on the implementation and interpretation of human studies. Emphasis will be on occupational exposures, although much of the information is also useful in assessing environmental studies, occupational exposures are usually much higher and better defined.

Effects of boric acid and 2-aminoethoxydiphenyl borate on necrotizing enterocolitis

OBJECTIVE

The aim was to study the effects of boric acid (BA) and 2-aminoethoxydiphenyl borate (2-APB) on oxidative stress and inflammation in an experimental necrotizing enterocolitis (NEC) rat model.

METHODS

Experimental NEC was induced in 40 newborn Sprague-Dawley rats by asphyxia and hypothermia applied in 3 consecutive days. Rats were subdivided into 4 subgroups as NEC, NEC+BA, NEC+2-APB, and controls. BA and 2-APB were applied daily before the procedure. Serum total antioxidant status, superoxide dismutase (SOD), tumor necrosis factor (TNF)-α, interleukin (IL)-6, and erythrocyte glutathione (GSH) levels were measured. Pathological changes for NEC in intestinal architecture were evaluated by a grading system.

RESULTS

Pretreatment with BA and 2-APB resulted in a decrease in NEC incidence. In all of the NEC groups, decreased serum levels of GSH and SOD were measured. Boron limited GSH consumption but had no effect on SOD levels. Total antioxidant status levels were not statistically different among groups. In our experimental NEC model, BA, but not 2-APB, prevented the increase of TNF-α. Pretreatment with BA and 2-APB downregulated the activity levels of IL-6 in NEC.

CONCLUSIONS

In the experimental NEC model, BA and 2-APB partly prevent NEC formation, modulate the oxidative stress parameters, bring a significant decrease in GSH consumption, and enhance the antioxidant defense mechanism, but have no effect on total antioxidant status. BA inhibits the hypoxia and hypothermia-induced increase in both IL-6 and TNF-a, but 2-APB only in IL-6. Boron may be beneficial in preventing NEC.

Occupational causes of male infertility

PURPOSE OF REVIEW

To highlight and discuss the new evidence on occupational and environmental risk to male reproductive function.

RECENT FINDINGS

Semen quality following occupational exposure to boron (an acknowledged experimental reproductive toxicant) and benzene, and new evidence on low-level environmental exposure to widespread xenobiotics with endocrine actions.

SUMMARY

The naturally occurring semimetal boron is an experimental reproductive toxicant, but now a Turkish semen study corroborates earlier evidence that high-level occupational exposure is not toxic to human spermatogenesis. It seems that human exposure levels are below the levels that cause reproductive toxicity in rodents. On the contrary, there is now ample evidence that the carcinogenic substance benzene may cause chromosomal aberrations in sperm at very low exposure levels. This includes chromosomal deletions that are known to cause infertility, mental retardation and congenital malformations. This research highlights the need to scrutinize the chemicals for possible male-mediated developmental toxicity. Several occupational studies are addressing adult testicular function in men exposed to chemicals that may interfere with endocrine signalling such as bisphenol A and phthalates, but findings are rather inconsistent and it remains to be established whether these widespread chemicals have any impact on male fertility.

Reverse relationship between blood boron level and body mass index in humans: does it matter for obesity?

The exact role of boron in humans is not known although its supplementation causes several important metabolic and inflammatory changes. The objective of this study is to evaluate the possibility of an association between blood boron level and obesity in normal, overweight, obese, and morbidly obese subjects. A total number of 80 subjects, categorized into four groups based on their body mass index as normal, overweight, obese, and morbidly obese, were enrolled in this study. Age, sex, body mass index, and blood boron levels were recorded for each subject. Although the distribution of female and male subjects and blood boron levels were similar between groups, the mean age of normal subjects was significantly lower than the others (p = 0.002). There was a significant relationship between age and quantitative values of body mass index for each subject (β = 0.24; p = 0.003). In addition, between blood boron levels and quantitative values of body mass index for each subject, a significant reverse relationship was detected (β = -0.16; p = 0.043). Although age seemed to be an important variable for blood boron level and body mass index, blood boron levels were shown to be lower in obese subjects in comparison to non-obese subjects.

Reproductive toxicity in boron exposed workers in Bandirma, Turkey

Boric acid and sodium borates have been considered as being "toxic to reproduction and development", following results of animal studies with high doses. However unfavorable effects of boron exposure on reproduction and development have not been proved in epidemiological studies so far. The aim of the present study was to investigate the reproductive toxicity indicators in highly exposed workers employed in a boric acid production plant in Bandırma, Turkey. Two hundred and four workers participated in this study. The mean blood boron concentration of the high exposure group of workers was 223.89 ± 69.49 (152.82-454.02)ng/g. Unfavorable effects of boron exposure on the reproductive toxicity indicators were not observed.

Exposure assessment of boron in Bandırma boric acid production plant

Boric acid and sodium borates have been considered as being "toxic to reproduction and development", following results of animal studies with high doses. Experimentally, a NOAEL of 17.5mg B/kg-bw/day (corresponds to ∼2020 ng boron/g blood) has been identified for the (male) reproductive effects of boron in a multigenerational study of rats, and a NOAEL for the developmental effects in rats was identified at 9.6 mg B/kg-bw/day (corresponds to 1270 ng boron/g blood). These values are being taken as the basis of current EU safety assessments. The present study was conducted to assess the boron exposure under extreme exposure conditions in a boric acid production plant located in Bandırma, Turkey. The mean blood boron concentrations of low and high exposure groups were 72.94 ± 15.43 (48.46-99.91) and 223.89 ± 60.49 (152.82-454.02)ng/g respectively. The mean blood boron concentration of the high exposure group is still ≈ 6 times lower than the highest no effect level of boron in blood with regard to the developmental effects in rats and ≈ 9 times lower than the highest no effect level of boron in blood with regard to the reprotoxic effects in male rats. In this context, boric acid and sodium borates should not be considered as toxic to reproduction for humans in daily life.

Human environmental and occupational exposures to boric acid: reconciliation with experimental reproductive toxicity data

The reproductive toxicity of boric acid and borates is a matter of current regulatory concern. Based on experimental studies in rats, no-observed-adverse-effect levels (NOAELs) were found to be 17.5 mg boron (B)/kg body weight (b.w.) for male fertility and 9.6 mg B/kg b.w. for developmental toxicity. Recently, occupational human field studies in highly exposed cohorts were reported from China and Turkey, with both studies showing negative results regarding male reproduction. A comparison of the conditions of these studies with the experimental NOAEL conditions are based on reported B blood levels, which is clearly superior to a scaling according to estimated B exposures. A comparison of estimated daily B exposure levels and measured B blood levels confirms the preference of biomonitoring data for a comparison of human field studies. In general, it appears that high environmental exposures to B are lower than possible high occupational exposures. The comparison reveals no contradiction between human and experimental reproductive toxicity data. It clearly appears that human B exposures, even in the highest exposed cohorts, are too low to reach the blood (and target tissue) concentrations that would be required to exert adverse effects on reproductive functions.

Boron exposure assessment using drinking water and urine in the North of Chile

Boron is an essential trace element for plants and humans however it is still an open question what levels of boron are actually safe for humans. This study, conducted between 2006 and 2010, measured exposure levels of boron in drinking water and urine of volunteers in Arica, an area in the North of Chile with high levels of naturally occurring boron. Samples were taken of tap and bottled water (173 and 22, respectively), as well as urine from 22 volunteers, and subsequently analyzed by inductively coupled plasma spectroscopy (ICP-OES). Boron varied in public tap water from 0.22 to 11.3mgL(-1), with a median value of 2.9mgL(-1), while concentrations of boron in bottled water varied from 0.01 to 12.2mgL(-1). Neither tap nor bottled water samples had concentrations of boron within WHO recommended limits. The concentration of boron in urine varied between 0.45 and 17.4mgL(-1), with a median of 4.28mgL(-1) and was found to be correlated with tap water sampled from the homes of the volunteers (r=0.64). Authors highly recommend that in northern Chile - where levels of boron are naturally high - that the tap and bottled water supplies be monitored in order to protect public health and that regulatory standards also be established for boron in drinking water in order to limit exposure.