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Smith SH, Antonelli PJ. Potential Toxicity of Boric Acid Powder Otic Insufflation. Otolaryngol Head Neck Surg 2024; 170:99-102. [PMID: 37622535 DOI: 10.1002/ohn.484] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2023] [Revised: 06/27/2023] [Accepted: 07/24/2023] [Indexed: 08/26/2023]
Abstract
OBJECTIVE Boric acid (BA) powder is commonly used to treat otologic conditions, such as mastoid bowl inflammation and chronic otitis externa. Exposure to 50 mg per day is thought to cause systemic toxicity in humans. Inflamed skin and mucosal surfaces readily absorb BA. The aim of this study was to measure the doses of BA commonly used in clinical otology and alert the otolaryngology community to BA's underappreciated potential source of systemic toxicity. STUDY DESIGN Prospective, controlled. SETTING Laboratory. METHODS BA dose administration was measured by weighing the BA generated by common insufflators: accordion bellows, House-Sheehy insufflator, DeVilbiss insufflator, and pneumatic powder blower. Manual insufflation was performed with 3 compressions of the bulb. The pneumatic blower was sprayed for 1 second. Measurements were repeated 10 times. RESULTS The DeVilbiss insufflator delivered the lowest mean BA dose, 6.1 mg (SD 3.4, range 2.1-13.7), followed by the House-Sheehy 8.9 mg (SD 8.4, range 1.6-27.8), the pneumatic blower 192.8 mg (SD 38.3, range 150.0-261.7), and the accordion, 284.1 mg (SD 215.0, range 37.8-730.8). CONCLUSION BA dose delivery is highly variable by insufflator type, and doses thought to cause systemic toxicity are commonly generated. Awareness of and further investigation into the potential toxicity of otic administration of BA seems warranted.
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Affiliation(s)
- Samuel H Smith
- Department of Otolaryngology, University of Florida, Gainesville, Florida, USA
| | - Patrick J Antonelli
- Department of Otolaryngology, University of Florida, Gainesville, Florida, USA
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The Effects of Different Doses of ROCK Inhibitor, Antifreeze Protein III, and Boron Added to Semen Extender on Semen Freezeability of Ankara Bucks. Molecules 2022; 27:molecules27228070. [PMID: 36432171 PMCID: PMC9698151 DOI: 10.3390/molecules27228070] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2022] [Revised: 11/07/2022] [Accepted: 11/15/2022] [Indexed: 11/22/2022] Open
Abstract
In the presented study, the effects of ROCK inhibitor Y-27632, antifreeze protein III, and boron at two different doses were investigated on the spermatological parameters of Ankara buck semen after freeze−thawing. Ejaculates were collected from bucks using an electroejaculator during the breeding season. The ejaculates that showed appropriate characteristics were pooled and used in the dilution and freezing of semen. The extender groups were formed by adding two different doses of three different additives (ROCK inhibitor Y-27632, 5 and 20 µM; antifreeze protein III, 1 and 4 µg/mL; boron, 0.25 and 1 mM) to the control extender. The semen was diluted with the different extenders at 35−37 °C and loaded into straws. Sperm samples frozen in liquid nitrogen vapors, following equilibration, were stored in liquid nitrogen. It was observed that extender supplementation improved post-thaw motility of Ankara buck semen after freeze−thawing. Differences were significant (p < 0.01) for 5 and 10 µM doses of ROCK inhibitor (71.82% and 74.04 % motility), as well as for 0.25 and 1 mM doses of boron (76.36% and 72.08% motility), compared to the control group (66.15% motility). With respect to the evaluation of acrosomal integrity and mitochondrial activity after freeze−thawing, although supplementation provided protection at all doses, the efficacy was not statistically significant (p > 0.05). It was observed that DNA damage was improved by antifreeze protein III at 1 µg/mL (1.23% ± 0.23%) and by boron at all doses (0.25 mM: 1.83% and 1 mM: 1.18%) compared to the control group (3.37%) (p < 0.01), following the thawing process. In the present study, it was determined that some additives added to the extender provided significant improvements in buck spermatozoa motility and DNA damage after thawing.
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Abdel-Wahab A, Ibrahim SS, El-Anwar AH, Mabrook EA, Ibrahim TB, Abdel-Razik ARH. Effects of dietary boron supplementation on the testicular function and thyroid activity in male goats: involvement of CYP17A1 gene. Reprod Domest Anim 2022; 57:1353-1362. [PMID: 35864721 DOI: 10.1111/rda.14212] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2022] [Revised: 07/19/2022] [Accepted: 07/20/2022] [Indexed: 11/28/2022]
Abstract
The physiological effects of dietary boron (B) supplementation for farm animals specifically goat on male fertility are still scarce and need deep investigation. Thus, the current study was designed to investigate how adding B to the diet of male goats affected their testicular and thyroid activity. For that purpose, twelve male goats were divided randomly into two groups (6 animals each); control group that was feed on the basal diet and B group that was fed the basal diet containing 70 mg B/kg diet for 6 months. Serum samples were collected at different intervals, while testicular biopsies were obtained at the end of the experiment. The results showed that 6 months of dietary B supplementation resulted in a significant increment in serum B concentration. The results of repeated measure analysis showed that there were significant GROUP and TIME x GROUP interactions effects on blood testosterone levels (F= 119.408, p=0.000, and F= 6.794, p=0.013, respectively), demonstrating that compared to control, B supplementation caused a significant rise in serum testosterone levels over time. However, the mean animal body weights and the serum levels of triiodothyronine (T3) and thyroxine (T4) were kept comparable to the control ones at the different time points. The most striking finding is that B supplementation increased significantly the mRNA expression of the CYP17A1 which is essential for steroidogenesis (P<0.001). In addition, a histological examination of testicular tissue corroborated our findings and demonstrated that B supplementation had a positive effect. As a result, B might be considered an excellent food supplement that could be safely added to the male goats' diet at the current dose to improve their reproductive capacity.
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Affiliation(s)
- Ahmed Abdel-Wahab
- Physiology Department, Faculty of Veterinary Medicine, Minia University, El-Minia, 61519, Egypt
| | - Shawky S Ibrahim
- Physiology Department, Faculty of Veterinary Medicine, Beni-Suef University, 62511, Beni-Suef, Egypt
| | - Ahmed H El-Anwar
- Physiology Department, Faculty of Veterinary Medicine, Beni-Suef University, 62511, Beni-Suef, Egypt
| | - Eid A Mabrook
- Physiology Department, Faculty of Veterinary Medicine, Beni-Suef University, 62511, Beni-Suef, Egypt
| | - Taha B Ibrahim
- Small and large ruminant farm, faculty of agriculture, Minia University, El-Minia, 61519, Egypt
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Zhang G, Wang A, Zhuang L, Wang X, Song Z, Liang R, Ren M, Long M, Jia X, Li Z, Su S, Wang J, Zhang N, Shen G, Wang B. Enrichment of boron element in follicular fluid and its potential effect on the immune function. ENVIRONMENTAL POLLUTION (BARKING, ESSEX : 1987) 2022; 304:119147. [PMID: 35314206 DOI: 10.1016/j.envpol.2022.119147] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/19/2022] [Revised: 02/23/2022] [Accepted: 03/13/2022] [Indexed: 06/14/2023]
Abstract
The blood-follicle barrier (BFB) between the blood and follicular fluid (FF) can maintain the microenvironment balance of oocyte. Boron, an exogenous environmental trace element, has been found to possibly play an important role in oocyte maturation. This study aimed to examine the distribution characteristics of boron across the BFB and find the potential effect of boron on FF microenvironment. We analyzed the concentration of boron in paired FF and serum collected from 168 women undergoing in vitro fertilization and embryo transfer in Beijing City and Shandong Province, China. To explore the potential health impact of boron enrichment in oocyte maturation, a global proteomics analysis was conducted to tentatively correlate the protein levels with the boron enrichment. Interestingly, the results showed that the concentration of boron in FF (34.5 ng/mL) was significantly higher than that in serum (22.0 ng/mL), with a median concentration ratio of 1.52. Likewise, the concentrations of boron in FF and serum were positively correlated (r = 0.446), suggesting that boron concentration in serum can represent its concentration in follicular fluid to a large extent.. This is the first time to observe the enrichment of boron in the FF to our knowledge. It is interesting to observe a total of 13 proteins, which mainly belong to immunoglobulin class, were positively correlated with boron concentration in FF. We concluded that boron, as one environmental trace element, was enriched in FF from blood validated by two area in north china, which may be involved in an increased level of immune processes of immunoglobulins.
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Affiliation(s)
- Guohuan Zhang
- Institute of Reproductive and Child Health, School of Public Health, Peking University, Beijing, 100191, PR China; Key Laboratory of Reproductive Health, National Health and Family Planning Commission of the People's Republic of China, Beijing, 100191, China; Department of Epidemiology and Biostatistics, School of Public Health, Peking University, Beijing, 100191, China
| | - Anni Wang
- Department of Neurosurgery, General Hospital of Ningxia Medical University, Yinchuan, 750004, China
| | - Lili Zhuang
- Reproductive Medicine Centre, Yuhuangding Hospital of Yantai, Affiliated Hospital of Qingdao University, Yantai, 264000, China
| | - Xikai Wang
- School of Basic Medical Sciences, Capital Medical University, Beijing, 100069, China
| | - Ziyi Song
- Reproductive Medical Center, Peking University People's Hospital, Beijing, 100044, China
| | - Rong Liang
- Reproductive Medical Center, Peking University People's Hospital, Beijing, 100044, China
| | - Mengyuan Ren
- Institute of Reproductive and Child Health, School of Public Health, Peking University, Beijing, 100191, PR China; Key Laboratory of Reproductive Health, National Health and Family Planning Commission of the People's Republic of China, Beijing, 100191, China; Department of Epidemiology and Biostatistics, School of Public Health, Peking University, Beijing, 100191, China
| | - Manman Long
- Institute of Reproductive and Child Health, School of Public Health, Peking University, Beijing, 100191, PR China; Key Laboratory of Reproductive Health, National Health and Family Planning Commission of the People's Republic of China, Beijing, 100191, China; Department of Epidemiology and Biostatistics, School of Public Health, Peking University, Beijing, 100191, China
| | - Xiaoqian Jia
- Institute of Reproductive and Child Health, School of Public Health, Peking University, Beijing, 100191, PR China; Key Laboratory of Reproductive Health, National Health and Family Planning Commission of the People's Republic of China, Beijing, 100191, China; Department of Epidemiology and Biostatistics, School of Public Health, Peking University, Beijing, 100191, China
| | - Zhiwen Li
- Institute of Reproductive and Child Health, School of Public Health, Peking University, Beijing, 100191, PR China; Key Laboratory of Reproductive Health, National Health and Family Planning Commission of the People's Republic of China, Beijing, 100191, China; Department of Epidemiology and Biostatistics, School of Public Health, Peking University, Beijing, 100191, China
| | - Shu Su
- Institute of Reproductive and Child Health, School of Public Health, Peking University, Beijing, 100191, PR China; Key Laboratory of Reproductive Health, National Health and Family Planning Commission of the People's Republic of China, Beijing, 100191, China; Department of Epidemiology and Biostatistics, School of Public Health, Peking University, Beijing, 100191, China
| | - Jiahao Wang
- China Center for Health Development Studies, School of Public Health, Peking University, Beijing, 100191, China
| | - Nan Zhang
- Gynecology Department, Peking University Cancer Hospital and Institute, Key Laboratory of Carcinogenesis and Translational Research, Beijing, 100871, China
| | - Guofeng Shen
- College of Urban and Environmental Sciences, Peking University, Beijing, 100871, China
| | - Bin Wang
- Institute of Reproductive and Child Health, School of Public Health, Peking University, Beijing, 100191, PR China; Key Laboratory of Reproductive Health, National Health and Family Planning Commission of the People's Republic of China, Beijing, 100191, China; Department of Epidemiology and Biostatistics, School of Public Health, Peking University, Beijing, 100191, China.
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Yılmaz Sarıaltın S, Üstündağ A, Mhlanga Chinheya R, İpek S, Duydu Y. Cytotoxicity, genotoxicity, oxidative stress, apoptosis, and cell cycle arrest in human Sertoli cells exposed to boric acid. J Trace Elem Med Biol 2022; 70:126913. [PMID: 34952296 DOI: 10.1016/j.jtemb.2021.126913] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/12/2021] [Revised: 12/10/2021] [Accepted: 12/13/2021] [Indexed: 12/18/2022]
Abstract
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.
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Affiliation(s)
- Sezen Yılmaz Sarıaltın
- Ankara University, Faculty of Pharmacy, Department of Pharmaceutical Toxicology, Ankara, Turkey
| | - Aylin Üstündağ
- Ankara University, Faculty of Pharmacy, Department of Pharmaceutical Toxicology, Ankara, Turkey.
| | - Rosa Mhlanga Chinheya
- Ankara University, Faculty of Health Sciences, Department of Forensic Chemistry and Toxicology, Ankara, Turkey
| | - Seda İpek
- Ankara University, Faculty of Pharmacy, Department of Pharmaceutical Toxicology, Ankara, Turkey
| | - Yalçın Duydu
- Ankara University, Faculty of Pharmacy, Department of Pharmaceutical Toxicology, Ankara, Turkey
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Bucak MN, Keskin N, Bodu M, Bülbül B, Kırbaş M, Öztürk AE, Frootan F, İli P, Özkan H, Başpınar N, Dursun Ş. Combination of trehalose and low boron in presence of decreased glycerol improves post-thawed ram sperm parameters: A model study in boron research. Andrology 2021; 10:585-594. [PMID: 34779585 DOI: 10.1111/andr.13130] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2021] [Revised: 10/20/2021] [Accepted: 11/10/2021] [Indexed: 12/16/2022]
Abstract
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.
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Affiliation(s)
- Mustafa Numan Bucak
- Department of Reproduction and Artificial Insemination, Faculty of Veterinary Sciences, Selçuk University, Konya, Turkey
| | - Nazan Keskin
- Department of Histology and Embryology, Faculty of Medicine, Pamukkale University, Denizli, Turkey
| | - Mustafa Bodu
- Department of Reproduction and Artificial Insemination, Faculty of Veterinary Sciences, Selçuk University, Konya, Turkey
| | - Bülent Bülbül
- Department of Reproduction and Artificial Insemination, Faculty of Veterinary Sciences, Dokuz Eylül University, İzmir, Turkey
| | - Mesut Kırbaş
- Bahri Dagdas International Agricultural Research Institute, Konya, Turkey
| | - Ali Erdem Öztürk
- Department of Reproduction and Artificial Insemination, Faculty of Veterinary Sciences, Erciyes University, Kayseri, Turkey
| | - Fateme Frootan
- National Institute of Genetic Engineering & Biotechnology (NIGEB), Tehran, Iran
| | - Pınar İli
- Denizli Vocational School of Health Services, Pamukkale University, Denizli, Turkey
| | - Hüseyin Özkan
- Department of Genetics, Faculty of Veterinary Sciences, Mustafa Kemal University, Hatay, Turkey
| | - Nuri Başpınar
- Department of Biochemistry, Faculty of Veterinary Sciences, Selcuk University, Konya, Turkey
| | - Şükrü Dursun
- Department of Gynecology and Obstetrics, Faculty of Veterinary Sciences, Aksaray University, Aksaray, Turkey
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Turck D, Castenmiller J, De Henauw S, Hirsch‐Ernst KI, Kearney J, Maciuk A, Mangelsdorf I, McArdle HJ, Naska A, Peláez C, Pentieva K, Siani A, Thies F, Tsabouri S, Vinceti M, Cubadda F, Frenzel T, Heinonen M, Marchelli R, Neuhauser‐Berthold M, Poulsen M, Maradona MP, Schlatter JR, van Loveren H, Rossi A, Knutsen HK. Safety of calcium fructoborate as a novel food pursuant to Regulation (EU) 2015/2283. EFSA J 2021; 19:e06661. [PMID: 34257728 PMCID: PMC8256803 DOI: 10.2903/j.efsa.2021.6661] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
Following a request from the European Commission, the EFSA Panel on Nutrition, Novel Foods and Food Allergens (NDA) was asked to deliver an opinion on calcium fructoborate as a novel food (NF) pursuant to Regulation (EU) 2015/2283. The NF, produced by chemical synthesis, contains a maximum of 2.9% of boron and on average 4.7% calcium and 84.2% fructose. It is intended to be marketed as food supplements targeting the general adult population, excluding pregnant and lactating women, at a maximum level of 220 mg/day (maximum boron intake of 6.4 mg per day). The combined intake of boron from the background diet and the NF is in the range of 9.6-9.9 mg/day (corresponding to up to 0.14 mg/kg body weight (bw) per day given a default bw of 70 kg). This is in the range of the acceptable daily intake (ADI) of 0.16 mg/kg bw per day. Under conditions mimicking the gastrointestinal (GI) environment, the NF is fully hydrolysed and the Panel considered boron toxicity relevant for the safety assessment. The Panel considers that there is no concern with respect to genotoxicity of the NF. The effect induced by the NF in a 13-week rat study is consistent with toxicological findings induced by treatment with boron compounds in animal studies. Epididymides-to-brain weight ratio was identified as the most relevant endpoint and the reference point derived was the lowest model averaged BMDL10 value of 529 mg/kg bw per day. This corresponds to 14.8 mg/kg bw per day of boron, which is higher than the critical no observed adverse effect level (NOAEL) (9.6 mg boron/kg bw per day) used for establishing the ADI of 0.16 mg/kg bw per day for boron. The Panel therefore applied the present ADI for boron in the assessment of the NF. The Panel concludes that the NF, calcium fructoborate, is safe under the proposed uses and use levels.
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Watson ATD, Sutherland VL, Cunny H, Miller-Pinsler L, Furr J, Hebert C, Collins B, Waidyanatha S, Smith L, Vinke T, Aillon K, Xie G, Shockley KR, McIntyre BS. Postnatal Effects of Gestational and Lactational Gavage Exposure to Boric Acid in the Developing Sprague Dawley Rat. Toxicol Sci 2021; 176:65-73. [PMID: 32392305 DOI: 10.1093/toxsci/kfaa061] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Human exposure to boron occurs primarily through diet and drinking water sources. Animal studies have found that reduced fetal weight following gestational exposure to boron (as boric acid) is the most sensitive toxicological effect. However, recent studies suggest that newborns in areas with elevated boron in drinking water may receive levels of exposure that exceed the U.S. EPA oral reference dose for B. Currently, there are no data to inform a boron risk assessment accounting for this developmental window. To address this knowledge gap, the National Toxicology Program evaluated developmental toxicity following pre- and postnatal boron exposure. Time-mated female Sprague Dawley (Hsd: Sprague Dawley SD) rats were administered 0-20 mg B/kg/day (as boric acid) via gavage from gestation day 6 to 21; offspring were dosed via gavage at the same respective dose level from postnatal day (PND) 1 to 28. There were no dose-related effects on dam bodyweight, bodyweight gain, or feed consumption. Clinical findings were limited to low incidences of umbilical hernia in the 20 mg B/kg pups which resolved by study completion. Pup plasma boron concentrations increased in dose-proportional manner and were similar between PND 4 and PND 28. Postnatal weight gain was significantly reduced at 20 mg B/kg, with male and female pups weighing 23% less than the controls on PND 28. These findings demonstrate that postnatal growth in the Sprague Dawley rat is sensitive to boron exposure and highlights the importance of evaluating the potential toxicity of agents with known human exposures during early life stages.
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Affiliation(s)
- AtLee T D Watson
- *Division of the National Toxicology Program, National Institute of Environmental Health Sciences, Research Triangle Park, North Carolina 27709
| | - Vicki L Sutherland
- *Division of the National Toxicology Program, National Institute of Environmental Health Sciences, Research Triangle Park, North Carolina 27709
| | - Helen Cunny
- *Division of the National Toxicology Program, National Institute of Environmental Health Sciences, Research Triangle Park, North Carolina 27709
| | - Lutfiya Miller-Pinsler
- †Toxicology and Pathology Services, Southern Research Institute, Birmingham, Alabama 35205
| | - Johnathan Furr
- †Toxicology and Pathology Services, Southern Research Institute, Birmingham, Alabama 35205
| | - Charles Hebert
- †Toxicology and Pathology Services, Southern Research Institute, Birmingham, Alabama 35205
| | - Brad Collins
- *Division of the National Toxicology Program, National Institute of Environmental Health Sciences, Research Triangle Park, North Carolina 27709
| | - Suramya Waidyanatha
- *Division of the National Toxicology Program, National Institute of Environmental Health Sciences, Research Triangle Park, North Carolina 27709
| | | | | | | | - Guanhua Xie
- §Social and Scientific Systems, Durham, North Carolina 27703
| | - Keith R Shockley
- ¶Division of Intramural Research, National Institute of Environmental Health Sciences, Research Triangle Park, North Carolina 27709
| | - Barry S McIntyre
- *Division of the National Toxicology Program, National Institute of Environmental Health Sciences, Research Triangle Park, North Carolina 27709
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Hadrup N, Frederiksen M, Sharma AK. Toxicity of boric acid, borax and other boron containing compounds: A review. Regul Toxicol Pharmacol 2021; 121:104873. [PMID: 33485927 DOI: 10.1016/j.yrtph.2021.104873] [Citation(s) in RCA: 26] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2020] [Revised: 01/06/2021] [Accepted: 01/18/2021] [Indexed: 01/14/2023]
Abstract
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.
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Affiliation(s)
- Niels Hadrup
- National Research Centre for the Working Environment, Copenhagen, DK, 2100, Denmark.
| | - Marie Frederiksen
- National Research Centre for the Working Environment, Copenhagen, DK, 2100, Denmark
| | - Anoop K Sharma
- Division for Risk Assessment and Nutrition, Group for Chemical Risk Assessment and GMO, National Food Institute, Technical University of Denmark, Denmark.
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Boric Acid, a Lewis Acid With Unique and Unusual Properties: Formulation Implications. J Pharm Sci 2020; 109:2375-2386. [DOI: 10.1016/j.xphs.2020.04.015] [Citation(s) in RCA: 21] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2020] [Revised: 04/05/2020] [Accepted: 04/22/2020] [Indexed: 12/16/2022]
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Effects of boron compounds on human reproduction. Arch Toxicol 2020; 94:717-724. [PMID: 32170343 DOI: 10.1007/s00204-020-02700-x] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2020] [Accepted: 03/05/2020] [Indexed: 12/23/2022]
Abstract
Because of the high pKa 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.
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BAŞARAN N, DUYDU Y, ÜSTÜNDAĞ A, TANER G, AYDIN S, ANLAR HG, YALÇIN CÖ, BACANLI M, AYDOS K, ATABEKOĞLU CS, GOLKA K, ICKSTADT K, SCHWERDTLE T, WERNER M, MEYER S, BOLT HM. Evaluation of the DNA damage in lymphocytes, sperm and buccal cells of workers under environmental and occupational boron exposure conditions. MUTATION RESEARCH-GENETIC TOXICOLOGY AND ENVIRONMENTAL MUTAGENESIS 2019; 843:33-39. [DOI: 10.1016/j.mrgentox.2018.12.013] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/29/2018] [Revised: 12/21/2018] [Accepted: 12/21/2018] [Indexed: 01/10/2023]
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Hjelm C, Harari F, Vahter M. Pre- and postnatal environmental boron exposure and infant growth: Results from a mother-child cohort in northern Argentina. ENVIRONMENTAL RESEARCH 2019; 171:60-68. [PMID: 30654250 DOI: 10.1016/j.envres.2019.01.012] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/01/2018] [Revised: 12/27/2018] [Accepted: 01/05/2019] [Indexed: 06/09/2023]
Abstract
BACKGROUND Experimental studies show developmental toxicity of boron and we recently found impaired weight and length in newborns of mothers exposed to boron through drinking water during pregnancy. OBJECTIVES To evaluate potential impact of pre- and postnatal boron exposure on infant anthropometry. METHODS In our mother-child cohort (n = 177) in Argentinean Andes, where drinking water concentrations of boron, lithium and arsenic have been found to vary considerably, we collected maternal blood and urine during and after pregnancy, placenta, breast milk, as well as infant urine and blood during the first 6 months of life. In all samples, boron and other potentially toxic elements were measured by ICP-MS. Infant weight (g), length (cm) and head circumference (cm) were measured at birth, 0-3 (n = 120) and/or 3-6 months (n = 120; 79 overlap) of age. RESULTS Boron concentrations in breast milk (range: 46-786 µg/L) correlated strongly with those in maternal serum (range: 47-624 µg/L; rs = 0.94) 0-3 months post-partum. In multivariable-adjusted linear regression, urinary boron (log2-transformed; range 60-9200 µg/L) in the youngest infants, but not maternal serum boron during pregnancy, was inversely associated with body weight at both 0-3 months (B: -141, 95% CI: -240; -42, p = 0.006) and 3-6 months (B: -200, 95% CI: -377; -23, p = 0.027). Infant urinary boron was also inversely associated with head circumference at 0-3 months (B: -0.39, 95% CI: -0.74; -0.04, p = 0.028), as well as length (B: -0.57, 95% CI: -1.1; -0.03, p = 0.040) and head circumference (B: -0.30, 95% CI: -0.64; 0.04, p = 0.083) at 3-6 months. CONCLUSIONS The observed first evidence that elevated environmental boron exposure in early infancy may adversely affect growth supports previous findings of boron-related impaired fetal growth. More research is needed to verify the findings at older age and in other populations.
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Affiliation(s)
- Camilla Hjelm
- Institute of Environmental Medicine, Karolinska Institutet, Box 210, SE-171 77 Stockholm, Sweden
| | - Florencia Harari
- Institute of Environmental Medicine, Karolinska Institutet, Box 210, SE-171 77 Stockholm, Sweden; Department of Occupational and Environmental Medicine, Sahlgrenska University Hospital and University of Gothenburg, Gothenburg, Sweden
| | - Marie Vahter
- Institute of Environmental Medicine, Karolinska Institutet, Box 210, SE-171 77 Stockholm, Sweden.
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14
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Pleus RC, Bruce G, Klintworth H, Sullivan D, Johnson W, Rajendran N, Keenan J. Repeated dose inhalation developmental toxicity study in rats exposed to cellulose insulation with boric acid additive. Inhal Toxicol 2019; 30:542-552. [PMID: 30829087 DOI: 10.1080/08958378.2019.1576806] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
Cellulose insulation (CI), a common building material, is a mixture of cellulose fibers and borates. Borates are approximately 20% of the product weight and act as a flame retardant. Given possible exposure to workers and consumers, an inhalation toxicity study was conducted following Organization for Economic Co-operation and Development (OECD) 414 for Prenatal Development Toxicity to evaluate if CI is a developmental toxicant. Pregnant female rats were exposed by nose-only inhalation to CI aerosols containing 20% boric acid for six h/day, from gestational day (GD) 6-19, and fetuses were evaluated for developmental parameters. Respirable CI was produced by grinding to produce respirable particles (MMAD 2.7-2.9 µm, geometric standard deviations (GSD) 1.9-2.6), which were then aerosolized. Target air concentrations were 15, 90, and 270 mg CI/m3. Controls were exposed to air only. Slight body weight reductions (average decrease <7% vs. control) were observed in male and female GD 20 fetuses in the mid and high dose groups. No embryo/fetal developmental toxicity or alterations in any other measured variable were reported at any dose. The no observed adverse effect level (NOAEL) for developmental outcomes was 270 mg/m3.
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Boron-exposed male workers in Turkey: no change in sperm Y:X chromosome ratio and in offspring’s sex ratio. Arch Toxicol 2019; 93:743-751. [DOI: 10.1007/s00204-019-02391-z] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2018] [Accepted: 01/10/2019] [Indexed: 10/27/2022]
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DeSesso JM, Scialli AR. Bone development in laboratory mammals used in developmental toxicity studies. Birth Defects Res 2018; 110:1157-1187. [PMID: 29921029 DOI: 10.1002/bdr2.1350] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2018] [Revised: 04/19/2018] [Accepted: 04/25/2018] [Indexed: 01/12/2023]
Abstract
Evaluation of the skeleton in laboratory animals is a standard component of developmental toxicology testing. Standard methods of performing the evaluation have been established, and modification of the evaluation using imaging technologies is under development. The embryology of the rodent, rabbit, and primate skeleton has been characterized in detail and summarized herein. The rich literature on variations and malformations in skeletal development that can occur in the offspring of normal animals and animals exposed to test articles in toxicology studies is reviewed. These perturbations of skeletal development include ossification delays, alterations in number, shape, and size of ossification centers, and alterations in numbers of ribs and vertebrae. Because the skeleton is undergoing developmental changes at the time fetuses are evaluated in most study designs, transient delays in development can produce apparent findings of abnormal skeletal structure. The determination of whether a finding represents a permanent change in embryo development with adverse consequences for the organism is important in study interpretation. Knowledge of embryological processes and schedules can assist in interpretation of skeletal findings.
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Duydu Y, Başaran N, Üstündağ A, Aydın S, Yalçın CÖ, Anlar HG, Bacanlı M, Aydos K, Atabekoğlu CS, Golka K, Ickstadt K, Schwerdtle T, Werner M, Meyer S, Bolt HM. Birth weights of newborns and pregnancy outcomes of environmentally boron-exposed females in Turkey. Arch Toxicol 2018; 92:2475-2485. [DOI: 10.1007/s00204-018-2238-4] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2018] [Accepted: 06/04/2018] [Indexed: 12/21/2022]
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18
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Boron and its compounds: current biological research activities. Arch Toxicol 2017; 91:2719-2722. [PMID: 28601966 DOI: 10.1007/s00204-017-2010-1] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2017] [Accepted: 06/06/2017] [Indexed: 10/19/2022]
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Igra AM, Harari F, Lu Y, Casimiro E, Vahter M. Boron exposure through drinking water during pregnancy and birth size. ENVIRONMENT INTERNATIONAL 2016; 95:54-60. [PMID: 27502898 DOI: 10.1016/j.envint.2016.07.017] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/04/2016] [Revised: 07/19/2016] [Accepted: 07/28/2016] [Indexed: 06/06/2023]
Abstract
BACKGROUND Boron is a metalloid found at highly varying concentrations in soil and water. Experimental data indicate that boron is a developmental toxicant, but the few human toxicity data available concern mostly male reproduction. OBJECTIVES To evaluate potential effects of boron exposure through drinking water on pregnancy outcomes. METHODS In a mother-child cohort in northern Argentina (n=194), 1-3 samples of serum, whole blood and urine were collected per woman during pregnancy and analyzed for boron and other elements to which exposure occurred, using inductively coupled plasma mass spectrometry. Infant weight, length and head circumference were measured at birth. RESULTS Drinking water boron ranged 377-10,929μg/L. The serum boron concentrations during pregnancy ranged 0.73-605μg/L (median 133μg/L) and correlated strongly with whole-blood and urinary boron, and, to a lesser extent, with water boron. In multivariable-adjusted linear spline regression analysis (non-linear association), we found that serum boron concentrations above 80μg/L were inversely associated with birth length (B-0.69cm, 95% CI -1.4; -0.024, p=0.043, per 100μg/L increase in serum boron). The impact of boron appeared stronger when we restricted the exposure to the third trimester, when the serum boron concentrations were the highest (0.73-447μg/L). An increase in serum boron of 100μg/L in the third trimester corresponded to 0.9cm shorter and 120g lighter newborns (p=0.001 and 0.021, respectively). CONCLUSIONS Considering that elevated boron concentrations in drinking water are common in many areas of the world, although more screening is warranted, our novel findings warrant additional research on early-life exposure in other populations.
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Affiliation(s)
- Annachiara Malin Igra
- Institute of Environmental Medicine, Karolinska Institutet, Box 210, SE-171 77 Stockholm, Sweden
| | - Florencia Harari
- Institute of Environmental Medicine, Karolinska Institutet, Box 210, SE-171 77 Stockholm, Sweden.
| | - Ying Lu
- Institute of Environmental Medicine, Karolinska Institutet, Box 210, SE-171 77 Stockholm, Sweden
| | - Esperanza Casimiro
- Atención Primaria de la Salud, Área Operativa XXIX, Hospital Dr. Nicolás Cayetano Pagano, San Antonio de los Cobres, 4411, Salta, Argentina
| | - Marie Vahter
- Institute of Environmental Medicine, Karolinska Institutet, Box 210, SE-171 77 Stockholm, Sweden
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Marone PA, Heimbach JT, Nemzer B, Hunter JM. Subchronic and genetic safety evaluation of a calcium fructoborate in rats. Food Chem Toxicol 2016; 95:75-88. [PMID: 27350145 DOI: 10.1016/j.fct.2016.06.021] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2016] [Revised: 06/17/2016] [Accepted: 06/21/2016] [Indexed: 11/25/2022]
Abstract
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.
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Affiliation(s)
- Palma Ann Marone
- Department of Pharmacology and Toxicology, Medical College of Virginia, Virginia Commonwealth University, Richmond, VA 23298, USA.
| | - James T Heimbach
- JHeimbach LLC, 923 Water Street, Box 66, Port Royal, VA 22535, USA.
| | - Boris Nemzer
- VDF FutureCeuticals, Inc., 2692 N. State Rt. 1-17, Momence, IL 60954, USA.
| | - John M Hunter
- VDF FutureCeuticals, Inc., 2692 N. State Rt. 1-17, Momence, IL 60954, USA.
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Hofmann T, Buesen R, Schneider S, van Ravenzwaay B. Postnatal fate of prenatal-induced fetal alterations in laboratory animals. Reprod Toxicol 2016; 61:177-85. [PMID: 27094378 DOI: 10.1016/j.reprotox.2016.04.010] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2016] [Revised: 04/06/2016] [Accepted: 04/11/2016] [Indexed: 01/11/2023]
Abstract
Currently it is common practice to evaluate the developmental toxicity hazard of chemicals or pharmaceuticals by evaluation of fetuses after administration of the compound to pregnant animals. These studies are designed to provide possible compound-related fetal changes near term, which are usually classified into malformations or variations. Malformations, but not variations are expected to adversely affect the survival or health. Therefore, classification has striking different regulatory consequences. For categorization as variation reversibility is an important criterion, but it is usually not examined in a standard guideline study. Although this issue has already been recognized long time ago, data dealing with the postnatal reversibility of fetal alterations are still rare. In the current review, literature data, regulatory documents as well as in-house data were compiled. Beside skeletal alterations of skull, vertebral column, ribs, shoulder and pelvic girdle, and extremities, kidney and heart defects are discussed and assessed.
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Affiliation(s)
- Thomas Hofmann
- BASF SE, Experimental Toxicology and Ecology, 67056 Ludwigshafen, Germany.
| | - Roland Buesen
- BASF SE, Experimental Toxicology and Ecology, 67056 Ludwigshafen, Germany
| | - Steffen Schneider
- BASF SE, Experimental Toxicology and Ecology, 67056 Ludwigshafen, Germany
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22
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Kimmel CA, Garry MR, DeSesso JM. Relationship between bent long bones, bent scapulae, and wavy ribs: malformations or variations? ACTA ACUST UNITED AC 2014; 101:379-92. [PMID: 25250905 DOI: 10.1002/bdrb.21122] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2014] [Accepted: 08/07/2014] [Indexed: 01/18/2023]
Abstract
BACKGROUND Shortened and bent long bones and bent scapulae are sometimes reported in fetuses with wavy ribs (Carney and Kimmel, ). Wavy ribs are typically seen in the presence of maternal and developmental toxicity, are transient and reversible postnatally, and are considered to be variations rather than malformations. METHODS We further assessed the literature cited in Kimmel and Carney () as well as papers published since then to determine under what conditions bent long bones in the absence of gross limb defects and bent scapulae were reported and whether information was available on the transient or permanent nature of these effects. RESULTS Long bone and/or scapular changes almost always occurred at a lower incidence than wavy ribs. In every case, maternal and fetal toxicity occurred at the same dose levels. In a few studies, pups were followed sequentially after birth and bent long bones and scapulae were transient in nature and appeared normal by the time of weaning. Rabbits were much less likely to show wavy ribs or long bone and scapular changes at birth, even in the presence of severe maternal and fetal toxicity. This species difference may be due in part to the great increase in bone mass and remodeling that occurs during the first few postnatal weeks in rodents, but which takes place during the longer fetal period in rabbits. CONCLUSION Our conclusion from this review is that bent long bones and scapulae, like wavy ribs, appear to be secondary to maternal and developmental toxicity, are transient, and like wavy ribs should be considered variations rather than malformations.
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Affiliation(s)
- Carole A Kimmel
- Exponent, Inc, Toxicology and Mechanistic Biology, Alexandria, Virginia
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23
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French JM. Imaging and morphology in reproductive toxicology - progress to date and future directions. Reprod Toxicol 2014; 48:37-40. [PMID: 24681297 DOI: 10.1016/j.reprotox.2014.03.008] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2014] [Accepted: 03/17/2014] [Indexed: 11/29/2022]
Abstract
This review looks at the recent development and application of imaging techniques for the morphological examination of fetuses from preclinical regulatory reproductive toxicology studies. Full replacement of the examination methods currently used in routine studies (microdissection, Bouin's fluid fixation/sectioning and alizarin red S/alcian blue preparations) by imaging techniques has yet to be achieved. Progress, especially in the application of micro-CT for skeletal examination, has been made but challenges, particularly the financial investment required, remain. Despite this apparent lack of progress the application of imaging techniques to "non-routine" preclinical reproductive toxicology studies has been used to good effect. The ability to acquire multiple images over a time course i.e. longitudinally has enabled the fate, particularly of skeletal features, to be determined. The additional evidence gained from such studies can be used to better inform the prenatal developmental hazard assessment of test compounds.
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Maier A, Vincent M, Hack E, Nance P, Ball W. Derivation of an occupational exposure limit for inorganic borates using a weight of evidence approach. Regul Toxicol Pharmacol 2014; 68:424-37. [DOI: 10.1016/j.yrtph.2014.02.001] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2012] [Revised: 01/30/2014] [Accepted: 02/01/2014] [Indexed: 12/26/2022]
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25
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Scientific Opinion on the re‐evaluation of boric acid (E 284) and sodium tetraborate (borax) (E 285) as food additives. EFSA J 2013. [DOI: 10.2903/j.efsa.2013.3407] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
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26
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Safety assessment of boron by application of new uncertainty factors and their subdivision. Regul Toxicol Pharmacol 2013; 65:108-14. [DOI: 10.1016/j.yrtph.2012.10.013] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2012] [Revised: 10/22/2012] [Accepted: 10/26/2012] [Indexed: 11/21/2022]
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27
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Early-life exposure to lithium and boron from drinking water. Reprod Toxicol 2012; 34:552-60. [DOI: 10.1016/j.reprotox.2012.08.009] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2012] [Revised: 08/13/2012] [Accepted: 08/31/2012] [Indexed: 11/18/2022]
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28
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Başaran N, Duydu Y, Bolt HM. Reproductive toxicity in boron exposed workers in Bandirma, Turkey. J Trace Elem Med Biol 2012; 26:165-7. [PMID: 22575543 DOI: 10.1016/j.jtemb.2012.04.013] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/26/2012] [Accepted: 04/04/2012] [Indexed: 11/17/2022]
Abstract
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.
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Affiliation(s)
- Nurşen Başaran
- Hacettepe University, Faculty of Pharmacy, Department of Toxicology, 06100 Sıhhiye, Ankara, Turkey.
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29
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Bolt HM, Başaran N, Duydu Y. Human environmental and occupational exposures to boric acid: reconciliation with experimental reproductive toxicity data. JOURNAL OF TOXICOLOGY AND ENVIRONMENTAL HEALTH. PART A 2012; 75:508-514. [PMID: 22686310 DOI: 10.1080/15287394.2012.675301] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
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.
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Affiliation(s)
- Hermann M Bolt
- Leibniz Research Centre for Working Environment and Human Factors (IfADo), Dortmund, Germany.
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30
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Cortes S, Reynaga-Delgado E, Sancha AM, Ferreccio C. Boron exposure assessment using drinking water and urine in the North of Chile. THE SCIENCE OF THE TOTAL ENVIRONMENT 2011; 410-411:96-101. [PMID: 21978616 DOI: 10.1016/j.scitotenv.2011.08.073] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/05/2010] [Revised: 08/30/2011] [Accepted: 08/31/2011] [Indexed: 05/14/2023]
Abstract
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.
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Affiliation(s)
- S Cortes
- Departamento de Salud Pública, Pontificia Universidad Católica de Chile, Santiago, Chile.
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31
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Laufersweiler MC, Gadagbui B, Baskerville-Abraham IM, Maier A, Willis A, Scialli AR, Carr GJ, Felter SP, Blackburn K, Daston G. Correlation of chemical structure with reproductive and developmental toxicity as it relates to the use of the threshold of toxicological concern. Regul Toxicol Pharmacol 2011; 62:160-82. [PMID: 22019814 DOI: 10.1016/j.yrtph.2011.09.004] [Citation(s) in RCA: 1211] [Impact Index Per Article: 93.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2011] [Revised: 09/15/2011] [Accepted: 09/16/2011] [Indexed: 10/16/2022]
Abstract
In the absence of toxicological data on a chemical, the threshold of toxicological concern (TTC) approach provides a system to estimate a conservative exposure below which there is a low probability of risk for adverse health effects. The original toxicology dataset underlying the TTC was based on NOELs from repeat dose studies. Subsequently there have been several efforts to assess whether or not these limits are also protective for reproductive/developmental effects. This work expands the database of chemicals with reproductive and developmental data, presents these data in a comprehensive and transparent format and groups the chemicals according to the TTC "Cramer Class" rules. Distributions of NOAELs from each of these classes were used to assess whether the previously proposed TTC values based on repeat dose data are protective for reproductive/developmental toxicity endpoints as well. The present analysis indicates that, for each Cramer Class, the reproductive and developmental endpoints would be protected at the corresponding general TTC tiers derived by Munro et al. (1996).
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Assessment of DNA integrity (COMET assay) in sperm cells of boron-exposed workers. Arch Toxicol 2011; 86:27-35. [DOI: 10.1007/s00204-011-0743-9] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2011] [Accepted: 07/25/2011] [Indexed: 10/17/2022]
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Carney EW, Ellis AL, Tyl RW, Foster PM, Scialli AR, Thompson K, Kim J. Critical evaluation of current developmental toxicity testing strategies: a case of babies and their bathwater. ACTA ACUST UNITED AC 2011; 92:395-403. [DOI: 10.1002/bdrb.20318] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2011] [Accepted: 06/03/2011] [Indexed: 02/03/2023]
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Platzek T, Krätke R, Schulz C. Kosmetische Mittel. Bundesgesundheitsblatt Gesundheitsforschung Gesundheitsschutz 2010; 53:610-4. [DOI: 10.1007/s00103-010-1058-3] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
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Pongsavee M. Effect of borax on immune cell proliferation and sister chromatid exchange in human chromosomes. J Occup Med Toxicol 2009; 4:27. [PMID: 19878537 PMCID: PMC2776007 DOI: 10.1186/1745-6673-4-27] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2009] [Accepted: 10/30/2009] [Indexed: 11/15/2022] Open
Abstract
Background Borax is used as a food additive. It becomes toxic when accumulated in the body. It causes vomiting, fatigue and renal failure. Methods The heparinized blood samples from 40 healthy men were studied for the impact of borax toxicity on immune cell proliferation (lymphocyte proliferation) and sister chromatid exchange in human chromosomes. The MTT assay and Sister Chromatid Exchange (SCE) technic were used in this experiment with the borax concentrations of 0.1, 0.15, 0.2, 0.3 and 0.6 mg/ml. Results It showed that the immune cell proliferation (lymphocyte proliferation) was decreased when the concentrations of borax increased. The borax concentration of 0.6 mg/ml had the most effectiveness to the lymphocyte proliferation and had the highest cytotoxicity index (CI). The borax concentrations of 0.15, 0.2, 0.3 and 0.6 mg/ml significantly induced sister chromatid exchange in human chromosomes (P < 0.05). Conclusion Borax had effects on immune cell proliferation (lymphocyte proliferation) and induced sister chromatid exchange in human chromosomes. Toxicity of borax may lead to cellular toxicity and genetic defect in human.
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Affiliation(s)
- Malinee Pongsavee
- Department of Medical Technology, Faculty of Allied Health Sciences, Thammasat University, Rangsit Campus, Patumthani 12121, Thailand.
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Demchuk E, Ruiz P, Wilson JD, Scinicariello F, Pohl HR, Fay M, Mumtaz MM, Hansen H, De Rosa CT. Computational Toxicology Methods in Public Health Practice. Toxicol Mech Methods 2008; 18:119-35. [DOI: 10.1080/15376510701857148] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
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Carney EW, Kimmel CA. Interpretation of skeletal variations for human risk assessment: delayed ossification and wavy ribs. ACTA ACUST UNITED AC 2007; 80:473-96. [DOI: 10.1002/bdrb.20133] [Citation(s) in RCA: 70] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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Abstract
Boron, the fifth element in the periodic table, is ubiquitous in nature. It is present in food and in surface and ocean waters, and is frequently used in industrial, cosmetic, and medical settings. Exposure to boron and related compounds has been recently implicated as a potential cause of chronic kidney disease in Southeast Asia. This observation prompted the present review of the published data on the effects of acute and chronic exposure to boron on renal function and structure in human beings and in experimental animals.
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Affiliation(s)
- Madeleine V Pahl
- Division of Nephrology and Hypertension, Department of Medicine, University of California, Irvine, CA, USA.
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Opinion of the Scientific Panel on Dietetic products, nutrition and allergies [NDA] related to the Tolerable Upper Intake Level of Boron (Sodium Borate and Boric Acid). EFSA J 2004. [DOI: 10.2903/j.efsa.2004.80] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023] Open
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40
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Mitchell A, Bakshi K, Kimmel C, Buck G, Feuston M, Foster PM, Friedman J, Holson J, Hughes C, Moore J, Schwetz B, Scialli A, Scott W, Vorhees C, Zirkin B. Evaluating chemical and other agent exposures for reproductive and developmental toxicity. JOURNAL OF TOXICOLOGY AND ENVIRONMENTAL HEALTH. PART A 2004; 67:1159-1314. [PMID: 15205023 DOI: 10.1080/15287390490460994] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
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Kroes R, Renwick AG, Cheeseman M, Kleiner J, Mangelsdorf I, Piersma A, Schilter B, Schlatter J, van Schothorst F, Vos JG, Würtzen G. Structure-based thresholds of toxicological concern (TTC): guidance for application to substances present at low levels in the diet. Food Chem Toxicol 2004; 42:65-83. [PMID: 14630131 DOI: 10.1016/j.fct.2003.08.006] [Citation(s) in RCA: 505] [Impact Index Per Article: 25.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
The threshold of toxicological concern (TTC) is a pragmatic risk assessment tool that is based on the principle of establishing a human exposure threshold value for all chemicals, below which there is a very low probability of an appreciable risk to human health. The concept that there are levels of exposure that do not cause adverse effects is inherent in setting acceptable daily intakes (ADIs) for chemicals with known toxicological profiles. The TTC principle extends this concept by proposing that a de minimis value can be identified for many chemicals, in the absence of a full toxicity database, based on their chemical structures and the known toxicity of chemicals which share similar structural characteristics. The establishment and application of widely accepted TTC values would benefit consumers, industry and regulators. By avoiding unnecessary toxicity testing and safety evaluations when human intakes are below such a threshold, application of the TTC approach would focus limited resources of time, cost, animal use and expertise on the testing and evaluation of substances with the greatest potential to pose risks to human health and thereby contribute to a reduction in the use of animals. An Expert Group of the European branch of the International Life Sciences Institute-ILSI Europe-has examined the TTC principle for its wider applicability in food safety evaluation. The Expert Group examined metabolism and accumulation, structural alerts, endocrine disrupting chemicals and specific endpoints, such as neurotoxicity, teratogenicity, developmental toxicity, allergenicity and immunotoxicity, and determined whether such properties or endpoints had to be taken into consideration specifically in a step-wise approach. The Expert Group concluded that the TTC principle can be applied for low concentrations in food of chemicals that lack toxicity data, provided that there is a sound intake estimate. The use of a decision tree to apply the TTC principle is proposed, and this paper describes the step-wise process in detail. Proteins, heavy metals and polyhalogenated-dibenzodioxins and related compounds were excluded from this approach. When assessing a chemical, a review of prior knowledge and context of use should always precede the use of the TTC decision tree. The initial step is the identification and evaluation of possible genotoxic and/or high potency carcinogens. Following this step, non-genotoxic substances are evaluated in a sequence of steps related to the concerns that would be associated with increasing intakes. For organophosphates a TTC of 18microg per person per day (0.3 microg/kg bw/day) is proposed, and when the compound is not an OP, the TTC values for the Cramer structural classes III, II and I, with their respective TTC levels (e.g. 1800, 540 and 90 microg per person per day; or 30, 9 and 1.5 microg/kg bw /day), would be applied sequentially. All other endpoints or properties were shown to have a distribution of no observed effect levels (NOELs) similar to the distribution of NOELs for general toxicity endpoints in Cramer classes I, II and III. The document was discussed with a wider audience during a workshop held in March 2003 (see list of workshop participants).
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Affiliation(s)
- R Kroes
- Utrecht University, Institute for Risk Assessment Sciences, Faculty of Veterinary Medicine, Yalelaan 2, PO Box 80176, NL- 3508 TD Utrecht, The Netherlands
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Wéry N, Narotsky MG, Pacico N, Kavlock RJ, Picard JJ, Gofflot F. Defects in cervical vertebrae in boric acid-exposed rat embryos are associated with anterior shifts of hox gene expression domains. BIRTH DEFECTS RESEARCH. PART A, CLINICAL AND MOLECULAR TERATOLOGY 2003; 67:59-67. [PMID: 12749385 DOI: 10.1002/bdra.10031] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
BACKGROUND Previously, we showed that prenatal exposure to boric acid (BA), an industrial agent with large production, causes alterations of the axial skeleton in rat embryos, reminiscent of homeotic transformations. Indeed, Sprague-Dawley rats exposed in utero to BA on gestation day 9 (GD 9) had only six, rather than the normal seven, cervical vertebrae. This finding, observed in 91% of GD 21 fetuses, suggests posterior transformations of vertebrae. The present study attempts to determine if these skeletal alterations could be explained by modifications of the hox code, involved in the establishment of positional information along the craniocaudal axis of the embryo. METHODS Pregnant rats were treated by gavage with BA (500 mg/kg, twice) on GD 9. Embryos were collected on GD 11 or GD 13.5 and processed for in situ hybridization. Several hox genes were selected according to the position of their cranial limit of expression in the cervical and thoracic region. RESULTS At GD 13.5, we detected a cranial shift of the anterior limit of expression of hoxc6 and hoxa6. We observed no difference between control and treated embryos in the location of the cranial limit of expression of the other genes: hoxd4, hoxa4, hoxc5, and hoxa5. CONCLUSIONS Our results demonstrate that following in utero exposure to BA on GD 9, a disturbance of the expression of hox genes involved inthe specification of most anterior vertebrae is observed at GD 13.5. Based on their expression domain and on their implication in the definition of the cervicothoracic vertebral boundary, it is likely that the anteriorization of hoxc6 and hoxa6 reported here is correlated to the morphological phenotype observed in BA-exposed fetuses at GD 21.
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Affiliation(s)
- Nathalie Wéry
- Unit of Developmental Genetics, Université Catholique de Louvain, Brussels, Belgium
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Fort DJ, Stover EL, Bantle JA, Dumont JN, Finch RA. Evaluation of a reproductive toxicity assay using Xenopus laevis: boric acid, cadmium and ethylene glycol monomethyl ether. J Appl Toxicol 2001; 21:41-52. [PMID: 11180279 DOI: 10.1002/jat.731] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Cadmium (Cd), boric acid (BA) and ethylene glycol monomethyl ether (EGME) were evaluated for reproductive and developmental toxicity in Xenopus laevis. Eight reproductively mature adult male and eight superovulated female Xenopus laevis were exposed to at least five separate sublethal concentrations of each material via the culture water for a period of 30 days. Four respective pairs were mated and the offspring evaluated for developmental effects; an evaluation of reproductive status was performed on the remaining four specimens. Ovary pathology, oocyte count, oocyte maturity and maturation capacity (germinal vesicle breakdown, GVBD) and necrosis were evaluated in the female, whereas testis pathology, sperm count, dysmorphology and motility were studied in the male. Based on this assessment, each test material exerted reproductive toxicity in Xenopus laevis, but with varying potencies. Adult female exposure to Cd and EGME particularly, and to a lesser extent to BA, resulted in transgenerational toxicity to the developing progeny. Further, this model appears to be a useful tool in the initial assessment and prioritization of potential reproductive toxicants for further testing.
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Affiliation(s)
- D J Fort
- The Stover Group, 5302 W. 6th Avenue, Stillwater, OK 74074-6746, USA.
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Fail PA, Chapin RE, Price CJ, Heindel JJ. General, reproductive, developmental, and endocrine toxicity of boronated compounds. Reprod Toxicol 1998; 12:1-18. [PMID: 9431568 DOI: 10.1016/s0890-6238(97)00095-6] [Citation(s) in RCA: 95] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Boric acid and inorganic borates are abundant in nature. They are widely used in industrial, agricultural, cosmetic, and numerous smaller applications. These compounds are toxic to all species tested at high doses, but they are not carcinogenic or mutagenic. The major toxicities are reproductive and developmental. Testicular effects occurred at approximately 26 mg boron equivalents/kg body weight (bw)/d (26 mg boron equivalent (BE)/kg bw/d). New data on endocrine toxicity includes altered follicle stimulating hormone and testosterone within 14 d of treatment. Because these hormonal changes may be secondary effects of testicular toxicity, borates are not suspect as endocrine disrupters. The most sensitive of all the endpoints are prenatal growth and morphologic development in the rat; these changes occurred at a dose of 12.9 mg BE/kg bw/d. The no observed adverse effect level for rat fetal development was 9.6 mg/kg BE. Considering the estimated human exposure levels and a safety factor of 30, humans are not at significant risk of reproductive failure due to borates from environmental sources. The margin of exposure is estimated at 72 for males and 129 for females. Thus, the likelihood of human toxicity caused by boric acid and inorganic borates from exposure during normal activities is remote.
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Affiliation(s)
- P A Fail
- Center for Life Sciences and Toxicology, Research Triangle Institute, NC 27709-2194, USA
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Price CJ, Strong PL, Murray FJ, Goldberg MM. Developmental effects of boric acid in rats related to maternal blood boron concentrations. Biol Trace Elem Res 1998; 66:359-72. [PMID: 10050930 DOI: 10.1007/bf02783148] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
Abstract
Timed-mated Sprague-Dawley rats (60/group) were exposed to boric acid (BA) from gestational days (gd) 0 to 20. BA added to the diet (0, 0.025, 0.050, 0.075, 0.1, or 0.2%) yielded boron (B) intakes of <0.35 (control), 3, 6, 10, 13, or 25 mg B/kg body wt/d. Approximately one-half of the dams/group were terminated on gd 20, maternal whole blood collected and frozen, and prenatal outcome (fetal growth, viability, and morphology) evaluated. Remaining dams received control diet beginning on gd 20, and litters were monitored throughout lactation. Blood samples were prepared by a high-temperature alkaline ashing method and analyzed for B by inductively coupled plasma (ICP) optical emission spectrometry. On gd 20, blood B concentrations of 1.27 +/- 0.298 and 1.53 +/- 0.546 microg B/g were associated with the no-observed-adverse-effect level (NOAEL) and lowest-observed-adverse-effect level (LOAEL) (10 and 13 mg B/kg/d, respectively) for developmental toxicity. Developmental toxicity persisted postnatally only at 25 mg B/kg/d, a dose associated with >10-fold increase in maternal blood B (2.82 +/- 0.987 vs. 0.229 +/- 0.143 microg B/g for controls). Maternal blood B concentrations were: 1. Significantly elevated in all BA-exposed groups. 2. Positively correlated with maternal BA intake. 3. Inversely correlated with fetal body weight at doses above the NOAEL.
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Affiliation(s)
- C J Price
- Chemistry & Life Sciences, Center for Life Sciences & Toxicology, Research Triangle Institute, Research Triangle Park, NC 27709-2194, USA
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Mantovani A, Maranghi F, Ricciardi C, Macrì C, Stazi AV, Attias L, Zapponi GA. Developmental toxicity of carbendazim: comparison of no-observed-adverse-effect level and benchmark dose approach. Food Chem Toxicol 1998; 36:37-45. [PMID: 9487362 DOI: 10.1016/s0278-6915(97)00116-6] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
The benchmark dose (BD) approach has been applied to foetal data from four gavage segment II studies (rat studies 1 and 2, rabbit study, hamster study) on the teratogenic benzimidazole carbendazim. Nineteen parameters were assessed using the log-normal model as a practical tool to derive BDs; good model fitting was observed for all except two parameters. Data were evaluated on a 'per-implant/foetus' basis; BDs were derived from response rate increases of 1, 5, and 10%. The values were compared to the lowest-observed-adverse-effect levels (LOAELs) and no-observed-adverse effect levels (NOAELs) obtained by Fisher's exact test on a 'per-implant/foetus' basis. Frank effects observed only at the top dose and/or small sample size tended to increase the 95% confidence limits and this influenced the determination of BD. Generally, the BD approach provided slightly more conservative estimates than NOAEL; overall, BD01 and BD05 were similar to NOAEL, or even lower for several parameters. The LOAEL in most cases was similar to BD10. Reference doses obtained by dividing BD01 by a 10 or 100 uncertainty factor, corresponded to residual risks of 10(-5) or below. For two critical parameters (hydrocephalus in rat study 1 and resorption rate in the rabbit study) a NOAEL could not be found, whereas a BD was always determined.
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Affiliation(s)
- A Mantovani
- Laboratorio di Tossicologia Comparata ed Ecotossicologia, Istituto Superiore di Sanità, Rome, Italy
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Abstract
The pharmacokinetics of boric acid (BA) have been studied in animals and humans. Orally administered BA is readily and completely absorbed in rats, rabbits, and humans, as well as other animal species. In animals and humans, absorbed BA appears to be rapidly distributed throughout the body water via passive diffusion. Following administration of BA, the ratio of blood: soft tissue concentrations of boron (B) is approx 1.0 in rats and humans; in contrast, concentrations of B in bone exceed those in blood by a factor of approx 4 in both rats and humans. In rats, adipose tissue concentrations of B are only 20% of the levels found in blood and soft tissues; however, human data on adipose tissue levels are not available. BA does not appear to be metabolized in either animals or humans owing to the excessive energy required to break the B-O bond. BA has an affinity for cis-hydroxy groups, and it has been hypothesized to elicit its biological activity through this mechanism. The elimination kinetics of BA also appear to be similar for rodents and humans. BA is eliminated unchanged in the urine. The kinetics of elimination were evaluated in human volunteers given BA orally or intravenously; the half-life for elimination was essentially the same (approx 21 h) by either route of exposure. In rats, blood and tissue levels of B reached steady-state after 3-4 d of oral administration of BA; assuming first-order kinetics, a half-life of 14-19 h may be calculated. The lack of metabolism of BA eliminates metabolic clearance as a potential source of interspecies variation. Accordingly, in the absence of differences in metabolic clearance, renal clearance is expected to be the major determinant of interspecies variation in pharmacokinetics. Because glomerular filtration rates are slightly higher in rats than in humans, the slight difference in half-lives may be readily explained. The most sensitive toxicity end point for BA appears to be developmental toxicity in rats, with a No Observed Adverse Effect Level (NOAEL) and Lowest Observed Adverse Effect Level (LOAEL) of 55 and 76 mg BA/kg/d, respectively. Mean blood B levels in pregnant rats on gestation day 20 in the pivotal developmental toxicity study were reported to be 1.27 and 1.53 mcg B/g at the NOAEL and LOAEL, respectively. Blood B concentrations in humans are well below these levels. Average blood B levels in the most heavily exposed worker population at a borate mine was 0.24 mcg B/mL, and the estimated daily occupational exposure was equivalent to 160 mg BA/d. Blood B levels in the general population generally range from 0.03 to 0.09 mcg B/mL. These blood B values indicate an ample margin of safety for humans. In summary, the pharmacokinetics of BA in humans and rodents are remarkably similar, and interspecies differences in pharmacokinetics appear to be minimal.
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Affiliation(s)
- F J Murray
- Murray & Associates, San Jose, CA 95138, USA
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Lanoue L, Taubeneck MW, Muniz J, Hanna LA, Strong PL, Murray FJ, Nielsen FH, Hunt CD, Keen CL. Assessing the effects of low boron diets on embryonic and fetal development in rodents using in vitro and in vivo model systems. Biol Trace Elem Res 1998; 66:271-98. [PMID: 10050925 DOI: 10.1007/bf02783143] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
Abstract
To date, boron (B) essentiality has not been conclusively shown in mammals. This article summarizes the results of a series of in vitro and in vivo experiments designed to investigate the role of B in mammalian reproduction. In the first study, rat dams were fed either a low (0.04 microg B/g) or an adequate (2.00 microg B/g) B diet for 6 wk before breeding and through pregnancy; reproductive outcome was monitored on gestation day 20. Although low dietary B significantly lowered maternal blood, liver, and bone B concentrations, it had no marked effects on fetal growth or development. The goal of the second study was to assess the effects of B on the in vitro development of rat postimplantation embryos. Day 10 embryos collected from dams fed either the low or adequate B diets for at least 12 wk were cultured in serum collected from male rats exposed to one of the two dietary B treatments. Dams fed the low B diet had a significantly reduced number of implantation sites compared to dams fed the B-adequate diet. However, embryonic growth in vitro was not affected by B treatment. The aim of study 3 was to define the limits of boric acid (BA) toxicity on mouse preimplantation development in vitro. Two-cell mouse embryos were cultured in media containing graded levels of BA (from 6 to 10,000 microM). Impaired embryonic differentiation and proliferation were observed only when embryos were exposed to high levels of BA (>2000 microM), reflecting a very low level of toxicity of BA on early mouse embryonic development. Study 4 tested the effects of low (0.04 microg B/g) and adequate (2.00 microg B/g) dietary B on the in vitro development of mouse preimplantation embryos. Two-cell embryos obtained from the dams were cultured in vitro for 72 h. Maternal exposure to the low B diet for 10, 12, and 16 wk was associated with a reduction in blastocyst formation, a reduction in blastocyst cell number, and an increased number of degenerates. Collectively, these studies support the concept that B deficiency impairs early embryonic development in rodents.
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Affiliation(s)
- L Lanoue
- Department of Nutrition, University of California at Davis, 95616, USA
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50
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Abstract
Inorganic borates, including boric acid, Na, ammonium, K, and Zn borates generally display low acute toxicity orally, dermally, and by inhalation. They are either not irritant or mild skin and eye irritants. Exceptions owing to physiochemical properties do occur. Longer-term toxicological studies have been reported mainly on boric acid or borax where the properties are generally similar on an equivalent boron (B) basis. The critical effects in several species are male reproductive toxicity and developmental toxicity. The doses that cause these effects are far higher than any levels to which the human population could be exposed. Humans would need to consume daily some 3.3 g of boric acid (or 5.0 g borax) to ingest the same dose level as the lowest animal NOAEL. No effects on fertility were seen in a population of workers exposed to borates or to a population exposed to high environmental borate levels. There is remarkable similarity in the toxicological effects of boric acid and borax across different species. Other inorganic borates that simply dissociate to boric acid are expected to display similar toxicity, whereas those that do not dissociate simply to boric acid may display a different toxicological profile.
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