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Cravotto C, Fabiano-Tixier AS, Claux O, Abert-Vian M, Tabasso S, Cravotto G, Chemat F. Towards Substitution of Hexane as Extraction Solvent of Food Products and Ingredients with No Regrets. Foods 2022; 11:3412. [PMID: 36360023 PMCID: PMC9655691 DOI: 10.3390/foods11213412] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2022] [Revised: 10/20/2022] [Accepted: 10/24/2022] [Indexed: 08/13/2023] Open
Abstract
Hexane is a solvent used extensively in the food industry for the extraction of various products such as vegetable oils, fats, flavours, fragrances, colour additives or other bioactive ingredients. As it is classified as a "processing aid", it does not have to be declared on the label under current legislation. Therefore, although traces of hexane may be found in final products, especially in processed products, its presence is not known to consumers. However, hexane, and in particular the n-hexane isomer, has been shown to be neurotoxic to humans and has even been listed as a cause of occupational diseases in several European countries since the 1970s. In order to support the European strategy for a toxic-free environment (and toxic-free food), it seemed important to collect scientific information on this substance by reviewing the available literature. This review contains valuable information on the nature and origin of the solvent hexane, its applications in the food industry, its toxicological evaluation and possible alternatives for the extraction of natural products. Numerous publications have investigated the toxicity of hexane, and several studies have demonstrated the presence of its toxic metabolite 2,5-hexanedione (2,5-HD) in the urine of the general, non-occupationally exposed population. Surprisingly, a tolerable daily intake (TDI) has apparently never been established by any food safety authority. Since hexane residues are undoubtedly found in various foods, it seems more than necessary to clearly assess the risks associated with this hidden exposure. A clear indication on food packaging and better information on the toxicity of hexane could encourage the industry to switch towards one of the numerous other alternative extraction methods already developed.
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Affiliation(s)
- Christian Cravotto
- GREEN Extraction Team, INRAE, UMR 408, Avignon University, F-84000 Avignon, France
| | | | - Ombéline Claux
- GREEN Extraction Team, INRAE, UMR 408, Avignon University, F-84000 Avignon, France
| | - Maryline Abert-Vian
- GREEN Extraction Team, INRAE, UMR 408, Avignon University, F-84000 Avignon, France
| | - Silvia Tabasso
- Department of Drug Science and Technology, University of Turin, Via P. Giuria 9, 10125 Turin, Italy
| | - Giancarlo Cravotto
- Department of Drug Science and Technology, University of Turin, Via P. Giuria 9, 10125 Turin, Italy
| | - Farid Chemat
- GREEN Extraction Team, INRAE, UMR 408, Avignon University, F-84000 Avignon, France
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Spencer PS, Chen X. The Role of Protein Adduction in Toxic Neuropathies of Exogenous and Endogenous Origin. TOXICS 2021; 9:toxics9050098. [PMID: 33946924 PMCID: PMC8146965 DOI: 10.3390/toxics9050098] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/02/2021] [Revised: 04/20/2021] [Accepted: 04/24/2021] [Indexed: 02/07/2023]
Abstract
The peripheral (axonal) neuropathy associated with repeated exposure to aliphatic and aromatic solvents that form protein-reactive γ-diketones shares some clinical and neuropathological features with certain metabolic neuropathies, including type-II diabetic neuropathy and uremic neuropathy, and with the largely sub-clinical nerve damage associated with old age. These conditions may be linked by metabolites that adduct and cross-link neuroproteins required for the maintenance of axonal transport and nerve fiber integrity in the peripheral and central nervous system.
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Affiliation(s)
- Peter S. Spencer
- Department of Neurology, School of Medicine, and Oregon Institute of Occupational Health Sciences, Oregon Health & Science University, Portland, OR 97239, USA
- Correspondence:
| | - Xiao Chen
- Key Laboratory of Modern Toxicology of Shenzhen, Shenzhen Medical Key Subject of Health Toxicology (2020–2024), Shenzhen Center for Disease Control and Prevention, Shenzhen 518055, China;
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Piao F, Chen Y, Yu L, Shi X, Liu X, Jiang L, Yang G, Wang N, Gao B, Zhang C. 2,5-hexanedione-induced deregulation of axon-related microRNA expression in rat nerve tissues. Toxicol Lett 2019; 320:95-102. [PMID: 31760062 DOI: 10.1016/j.toxlet.2019.11.019] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2019] [Revised: 10/18/2019] [Accepted: 11/18/2019] [Indexed: 12/31/2022]
Abstract
Exposure to organic solvent in industry, including n-hexane is correlated with central-peripheral axonopathy, which is mediated by its active metabolite, 2,5-hexanedione (HD). However, the underlying mechanism is still largely unknown. Recently identified microRNAs (miRNAs) may play important roles in toxicant exposure and in the process of toxicant-induced neuropathys. To examine the role of miRNAs in HD-induced toxicity, neuropathic animal model was successfully built. miRNA microarray analysis revealed 105 differentially expressed miRNAs after HD exposure. Bioinformatics analysis showed that "Axon" and "Neurotrophin Signaling Pathway" was the top significant GO term and pathway, respectively. 7 miRNAs both related to "Axon" and "Neurotrophin Signaling Pathway" were screened out and further confirmed by Real-Time PCR. Correspondingly, the deregulation expression levels of proteins of four target genes (GSK3β, Map3k1, BDNF and MAP1B) were further confirmed via western blot, verifying the results of gene target analysis. Taken together, our results showed that the axon-related miRNAs to be associated with MAP1B or neurotrophin signal pathways changed in nerve tissues following HD exposure. These miRNAs may play important roles in HD-induced neurotoxicity.
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Affiliation(s)
- Fengyuan Piao
- Department of Occupational and Environmental Health, Dalian Medical University, Dalian 116044, PR China; Comprehensive Laboratory, Affiliated Zhongshan Hospital of Dalian University, Dalian 116044, PR China
| | - Yang Chen
- Department of Biotechnology, Basic Medical College, Dalian Medical University, Dalian 116044, PR China
| | - Li Yu
- College of Laboratory Medicine, Dalian Medical University, Dalian 116044, PR China
| | - Xiaoxia Shi
- Department of Occupational and Environmental Health, Dalian Medical University, Dalian 116044, PR China
| | - Xiaofang Liu
- Department of Food Nutrition and Safety, Dalian Medical University, Dalian 116044, PR China
| | - Liping Jiang
- Department of Food Nutrition and Safety, Dalian Medical University, Dalian 116044, PR China
| | - Guang Yang
- Department of Food Nutrition and Safety, Dalian Medical University, Dalian 116044, PR China
| | - Ningning Wang
- Department of Food Nutrition and Safety, Dalian Medical University, Dalian 116044, PR China
| | - Bihu Gao
- Department of Nephrology, Affiliated Zhongshan Hospital of Dalian University, Dalian 116044, PR China.
| | - Cong Zhang
- Department of Food Nutrition and Safety, Dalian Medical University, Dalian 116044, PR China.
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Pyrrole adducts in globin and plasma of workers exposed to hexane. Int Arch Occup Environ Health 2019; 92:873-881. [PMID: 30955093 DOI: 10.1007/s00420-019-01430-7] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2018] [Accepted: 04/03/2019] [Indexed: 10/27/2022]
Abstract
OBJECTIVES Urinary excretion of 2,5-hexanedione is currently used to estimate the exposure levels of hexane occurring to an individual during the previous work shift. However, because hexane exposures and urinary 2,5-hexanedione levels can vary considerably from day to day, and subchronic to chronic exposures to hexane are required to produce neuropathy, this biomarker may not accurately reflect the risk of an individual for developing hexane neuropathy. This investigation examines the potential of hexane-derived pyrrole adducts produced on globin and plasma proteins as markers for integrating cumulative exposures. Because the pyrrole markers incorporate bioactivation of hexane to 2,5-hexandione and the initial step of protein adduction involved in hexane-induced neuropathy, they potentially can serve as biomarkers of effect through reflecting pathogenetic events within the nervous system. Additionally, pyrrole formation is an irreversible reaction suggesting that hexane-derived protein pyrroles can be used to assess cumulative exposures to provide a better characterization of individual susceptibilities. METHODS To examine the utility of the proposed markers, blood samples were obtained from eleven workers who used hexane for granulating metal powders in a slurry to produce metal machining die tools and four non-exposed volunteers. Globin and plasma were isolated, and the proteins were digested using pepsin, reacted with Ehrlich's reagent and the level of pyrrole adducts were determined by absorbance at 530 nm. To determine the dose-response curve and dynamic range of the assay, erythrocytes were incubated with a range of 2,5-hexanedione concentrations and the net absorbance at 530 nm of isolated globin was measured. RESULTS Pyrrole was detected in both the globin and plasma samples of the workers exposed to hexane and the levels of pyrroles in plasma were positively correlated with the levels of pyrroles in globin for most of the workers. CONCLUSIONS This investigation demonstrates that detectable levels of hexane-derived protein pyrrole adducts are produced on peripheral proteins following occupational exposures to hexane and supports the utility of measuring pyrroles for integrating cumulative exposures to hexane.
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Determination of total urinary 2,5-hexanedione in the Chinese general population. ENVIRONMENTAL RESEARCH 2016; 150:645-650. [PMID: 27237929 DOI: 10.1016/j.envres.2016.05.030] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/19/2015] [Revised: 05/15/2016] [Accepted: 05/17/2016] [Indexed: 01/10/2023]
Abstract
OBJECTIVE Determination of the urinary levels of 2.5-hexanedione (2,5-HD) was performed in subjects belonging to the Chinese general population to define the reference value for this metabolite. METHODS Urine samples were collected from 8235 individuals (4216 men and 4019 women) from the healthy general population who had not been occupationally exposed to n-hexane or methyl-n-butyl ketone. The determination was performed by a gas chromatography mass spectrometry method using an ion-trap mass spectrometer. RESULTS The result showed that the urinary 2,5-HD median level was 0.159mg/L for the total samples. Males had statistically significant higher excretion of 2,5-HD in urine than females (median 0.171mg/L compared to 0.147mg/L, Z=-8.21, P<0.001). There was a statistically significant difference in urinary 2,5-HD levels among age groups. The excretion of 2,5-HD in urine was related to increasing age (r=-0.160, P<0.05). There was statistically significant difference in urinary 2,5-HD levels among people from difference provinces. The results showed that there was also a statistically significant effect in urinary 2,5-HD levels between current smokers and non-smokers. CONCLUSION Finding a measurable amount of 2,5-HD in urine does not mean that the level of 2,5-HD causes an adverse health effect. Biomonitoring studies on levels of urinary 2,5-HD can provide physicians and public health officials with reference values so that they can determine whether people have been exposed to higher levels of 2,5-HD than are found in the Chinese general population. These data can also provide a foundation for scientists to make a plan for further study.
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Yin H, Guo Y, Zeng T, Zhao X, Xie K. Correlation between levels of 2, 5-hexanedione and pyrrole adducts in tissues of rats exposure to n-hexane for 5-days. PLoS One 2013; 8:e76011. [PMID: 24098756 PMCID: PMC3786887 DOI: 10.1371/journal.pone.0076011] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2013] [Accepted: 08/16/2013] [Indexed: 11/18/2022] Open
Abstract
Background The formation of pyrrole adducts might be responsible for peripheral nerve injury caused by n-hexane. The internal dose of pyrrole adducts would supply more information for the neurotoxicity of n-hexane. The current study was designed to investigate the tissue distributions of 2, 5-hexanedione (2,5-HD) and pyrrole adducts in rats exposed to n-hexane, and analyze the correlation between pyrrole adducts and 2,5-HD in tissues. Methods Male Wistar rats were given daily dose of 500,1000, 2000, 4000 mg/kg bw n-hexane by gavage for 5 days. The rats were sacrificed 24 hours after the last administration. The levels of 2, 5-hexanedione and pyrrole adducts in tissues were measured by gas chromatography and Ehrlich’s reagent, respectively. The correlations between 2, 5-hexanedione and pyrrole adducts were analyzed by linear regression Results Dose-dependent effects were observed between the dosage of n-hexane and 2, 5-hexanedione, and pyrrole adducts in tissues. The highest level of 2, 5-hexanedione was found in urine and the lowest in sciatic nerve, while the highest level of pyrrole adducts was seen in liver and the lowest in serum. There were significant correlations among the free 2, 5-hexanedione, total 2, 5-hexanedione and pyrrole adducts within the same tissues. Pyrrole adducts in serum showed the most significant correlation with free 2, 5-hexanedione or pyrrole adducts in tissues. Conclusion The findings suggested that pyrrole adducts in serum might be a better indicator for the internal dose of free 2, 5-hexanedione and pyrrole adducts in tissues.
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Affiliation(s)
- Hongyin Yin
- Institute of Toxicology, School of Public Health, Shandong University, Jinan, Shandong Province, China
- Jinan Municipal Center for Disease Control & Prevention, Jinan, Shandong Province, China
| | - Ying Guo
- Institute of Toxicology, School of Public Health, Shandong University, Jinan, Shandong Province, China
| | - Tao Zeng
- Institute of Toxicology, School of Public Health, Shandong University, Jinan, Shandong Province, China
| | - Xiulan Zhao
- Institute of Toxicology, School of Public Health, Shandong University, Jinan, Shandong Province, China
| | - Keqin Xie
- Institute of Toxicology, School of Public Health, Shandong University, Jinan, Shandong Province, China
- * E-mail:
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Persson B, Vrethem M, Murgia N, Lindh J, Hällsten AL, Fredrikson M, Tondel M. Urinary 2,5-hexanedione excretion in cryptogenic polyneuropathy compared to the general Swedish population. J Occup Med Toxicol 2013; 8:21. [PMID: 23898939 PMCID: PMC3733657 DOI: 10.1186/1745-6673-8-21] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2013] [Accepted: 07/24/2013] [Indexed: 11/10/2022] Open
Abstract
Background 2,5-hexanedione (2,5-HD) is the main neurotoxic metabolite of methyl-n-butyl ketone (MBK) and n-hexane, and known to cause polyneuropathy. The aim of our study was to compare the urinary levels of 2,5-HD between cases with cryptogenic polyneuropathy and the general Swedish population, and to elucidate the role of certain external factors. Methods Morning urine samples were collected from 114 cases with cryptogenic polyneuropathy (77 men and 37 women) and 227 referents (110 men and 117 women) randomly selected from the population registry. None had any current occupational exposure to n-hexane or MBK. The urine samples were analysed by a gas chromatographic method based on acidic hydrolysis. Results Cases had statistically higher urinary levels of 2,5-HD (0.48 mg/L) than the general population (0.41 mg/L) and men higher excretion than women (0.48 mg/L and 0.38 mg/L, respectively). There was no difference in 2,5-HD levels between current smokers and non-smokers. Occupational exposure to xylene, alcohol consumption and ever exposed to general anaesthesia were associated with lower excretion in men while for occupational exposure to nitrous oxide in women higher excretion was seen. Higher excretion of 2,5 HD was inversely related to increasing age. Conclusions Significantly higher levels of urinary 2,5-HD were seen in men and cryptogenic polyneuropathy cases seemingly unexposed to n-hexane. Hypothetically, this might be due to either differences in metabolic patterns or some concealed exposure. The difference in means between cases and the general population is small and can therefore not allow any firm conclusions of the causality, however.
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Affiliation(s)
- Bodil Persson
- Division of Neurology and Neurophysiology, Department of Clinical and Experimental Medicine, Faculty of Health Sciences, Linköping University, Linköping, Sweden.
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Kawai T, Eitaki Y, Ukai H, Inoue O, Maeshima Y, Ueda N, Ohashi F, Sakurai H, Ikeda M. Validation of urine density correction in cases of hippuric acid and un-metabolized toluene in urine of workers exposed to toluene. INDUSTRIAL HEALTH 2010; 48:154-163. [PMID: 20424345 DOI: 10.2486/indhealth.48.154] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
Abstract
To investigate if it is appropriate to apply urine density correction when a urine sample is dense or dilute. Data on hippuric acid (HA-U), toluene (Tol-U), creatinine (CR) and specific gravity (SG) in end-of-shift urine samples and exposure to air-borne toluene were cited from previous publications. In practice, 837 cases were available, and they were classified into dense, intermediate and dilute groups taking 0.3 and 3.0 g/l of CR and 1.010 and 1.030 of SG as cut-off points. Lines of regression of HA-U and Tol-U (as observed, CR-corrected or SG-corrected) with air-borne toluene were calculated for each density groups, and correlation coefficients (CCs) were compared. The dense groups gave CCs similar to those of the intermediate groups. Dilute versus intermediate group comparison also gave promising results. These conclusions were however based primarily on the findings with observed values, because the numbers of cases in the dilute or dense group were limited when CR- or SG-correction was applied. Literature survey showed that urine density correction does not always improve the correlation between solvents in air and exposure makers in urine. It was concluded that no correction for urine density may be necessary in evaluating HA-U and Tol-U in dense (and probably also dilute) urine samples as markers of occupational toluene exposure. Just in case when correction for urine density is desired for any reason, SG-correction may be recommended.
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Affiliation(s)
- Toshio Kawai
- Osaka Occupational Health Service Center, Japan Industrial Safety and Health Association, Nishi-ku, Osaka, Japan
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Sari-Minodier I, Truchon G, Charest-Tardif G, Bérubé A, Tardif R. The effect of workload on biological monitoring of occupational exposure to toluene and n-Hexane: contribution of physiologically based toxicokinetic modeling. JOURNAL OF OCCUPATIONAL AND ENVIRONMENTAL HYGIENE 2009; 6:415-432. [PMID: 19384711 DOI: 10.1080/15459620902928141] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
A physiologically based toxicokinetic model was used to examine the impact of work load on the relationship between the airborne concentrations and exposure indicator levels of two industrial solvents, toluene and n-Hexane. The authors simulated occupational exposure (8 hr/day, 5 days/week) at different concentrations, notably 20 ppm and 50 ppm, which are the current threshold limit values recommended by ACGIH for toluene and n-hexane, respectively. Different levels of physical activity, namely, rest, 25 W, and 50 W (for 12 hr followed by 12 hr at rest) were simulated to assess the impact of work load on the recommended biological exposure indices: toluene in blood prior to the last shift of the workweek, urinary o-cresol (a metabolite of toluene) at the end of the shift, and free (nonhydrolyzed) 2,5-hexanedione (a metabolite of n-hexane) at the end of the shift at the end of the workweek. In addition, urinary excretion of unchanged toluene was simulated. The predicted biological concentrations were compared with the results of both experimental studies among human volunteers and field studies among workers. The highest predicted increase with physical exercise was noted for toluene in blood (39 microg/L at 50 W vs. 14 microg/L at rest for 20 ppm, i.e., a 2.8-fold increase). The end-of-shift urinary concentrations of o-cresol and toluene were two times higher at 50 W than at rest (for 20 ppm, 0.65 vs. 0.33 mg/L for o-cresol and 43 vs. 21 microg/L for toluene). Urinary 2,5-hexanedione predicted for 50 ppm was 1.07 mg/L at 50 W and 0.92 mg/L at rest (+16%). The simulations that best describe the concentrations among workers exposed to toluene are those corresponding to 25 W or less. In conclusion, toxicokinetic modeling confirms the significant impact of work load on toluene exposure indicators, whereas only a very slight effect is noted on n-hexane kinetics. These results highlight the necessity of taking work load into account in risk assessment relative to toluene exposure.
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Affiliation(s)
- Irène Sari-Minodier
- Groupe de recherche interdisciplinaire en santé, Département de santé environnementale et santé au travail, Université de Montréal, Québec, Canada
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Hamelin G, Charest-Tardif G, Truchon G, Tardif R. Physiologically based modeling of n-hexane kinetics in humans following inhalation exposure at rest and under physical exertion: impact on free 2,5-hexanedione in urine and on n-hexane in alveolar air. JOURNAL OF OCCUPATIONAL AND ENVIRONMENTAL HYGIENE 2005; 2:86-D7. [PMID: 15764529 DOI: 10.1080/15459620590909673] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
We used a modified physiologically based pharmacokinetic (PBPK) to describe/predict n-hexane (HEX) alveolar air concentrations and free 2,5-HD urinary concentrations in humans exposed to n-HEX by inhalation during a typical workweek. The effect of an increase in workload intensity on these two exposure indicators was assessed and, using Monte Carlo simulation, the impact of biological variability was investigated. The model predicted HEX alveolar air concentrations at rest of 19.0 ppm (25 ppm exposure) and 38.7 ppm (50 ppm exposure) at the end of the last working day (day 5), while free 2,5-HD urinary concentrations of 3.4 micromol/L (25 ppm) and 6.3 micromol/L (50 ppm) were predicted for the same period (last 4.5 hours of Day 5). Monte Carlo simulations showed that the range of values expected to occur in a group of 1000 individuals exposed to 50 ppm of HEX (95% confidence interval) for free 2,5-HD (1.7-14.7 micromol/L) is much higher compared with alveolar air HEX (33.4-46 ppm). Simulations of exposure at 50 ppm with different workloads predicted that an increase in workload intensity would not greatly affect both indicators studied. However, the alveolar air HEX concentration is more sensitive to modifications of workload intensity and time of sampling, after the end of exposure, compared with 2,5-HD. The PBPK model successfully described the HEX alveolar air concentrations and free 2,5-HD urinary concentrations measured in human volunteers and is the first, to our knowledge, to describe the excretion kinetics of free 2,5-HD in humans over a 5-day period.
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Affiliation(s)
- G Hamelin
- Département de santé environnementale et santé au travail, Université de Montréal, Montréal, Canada
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Prieto MJ, Marhuenda D, Roel J, Cardona A. Free and total 2,5-hexanedione in biological monitoring of workers exposed to n-hexane in the shoe industry. Toxicol Lett 2004; 145:249-60. [PMID: 14580896 DOI: 10.1016/s0378-4274(03)00302-3] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
OBJECTIVES To analyse the role of total 2,5-hexanedione (2,5-HD) compared with free 2,5-HD as a biological indicator of exposure to n-hexane at work. METHODS One-hundred and thirty two workers in contact with this solvent during their occupation in the shoe industry in the province of Alicante (Spain) were studied. Environmental and biological tests were carried out analysing variations of the concentration of the metabolite in urine corresponding to different working conditions. Environmental exposure was evaluated in each work place using active personal monitors and measured by gas chromatography (GC). Dichloromethane extracts of the urine samples collected at the end of the working shifts were analysed, before (determining free 2,5-HD, the toxic metabolite) and after acid hydrolysis (pH 0.1) (yielding the total 2,5-HD) and also by GC. The concentration of conjugated metabolite 4,5-dihydroxy-2-hexanone was calculated from the difference between total and free 2,5-HD. RESULTS Free 2,5-HD represented an average of 14.2% of the total 2,5-HD determined in urine, and this percentage increased significantly (P<0.01) with higher environmental levels of acetone. Other factors, such as absorption through the skin (depending on the use of gloves) and the day on which samples were taken also significantly affected the relation between the two indicators and their respective relationships with environmental concentrations of n-hexane. CONCLUSION Although analyses of the relationship between the levels of atmospheric n-hexane and those of metabolites in urine show a greater correlation for total 2,5-HD than for free 2,5-HD, our results suggest that free 2,5-HD could be a better indicator in evaluating risk of exposure to n-hexane, since the concentration is directly related to the neurotoxic effect.
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Affiliation(s)
- M J Prieto
- Faculty of Medicine, Legal and Forensic Medicine Division, University of Miguel Hernández, Apdo Correos no 18, E-03550 San Juan, Alicante, Spain.
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Yücesoy B, Yücel A, Erdem O, Burgaz S, Imir T, Karakaya AE, Karakaya A. Effects of occupational chronic co-exposure to n-hexane, toluen, and methyl ethyl ketone on NK cell activity and some immunoregulatory cytokine levels in shoe workers. Hum Exp Toxicol 1999; 18:541-6. [PMID: 10523867 DOI: 10.1191/096032799678845115] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
1. To evaluate the effects of occupational long-term co-exposure to n-hexane, toluen, and methyl ethyl ketone (MEK) on NK cell activity and serum IL-2, gamma-IFN levels, we studied a group of workers employed in a shoe factory where the jobs include use of glues and adhesives containing mainly n-hexane, and at low concentrations, toluen and MEK. 2. No differences were found in these parameters even in those workers with 3.3-fold higher mean levels of urine, 2,5-Hxdn and approximately twofold higher mean levels of urine hippuric acid as compared to controls. 3. We conclude that chronic co-exposure to n-hexane, toluen, and MEK at these levels is not associated with an impairment on either NK cell activity or serum IL-2 and gamma-IFN levels.
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Affiliation(s)
- B Yücesoy
- Department of Toxicology, Faculty of Pharmacy, Ankara University, 06100, Tandogan, Ankara, Turkey
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13
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Yokoyama K, Araki S, Murata K, Nishikitani M, Nakaaki K, Yokota J, Ito A, Sakata E. Postural sway frequency analysis in workers exposed to n-hexane, xylene, and toluene: assessment of subclinical cerebellar dysfunction. ENVIRONMENTAL RESEARCH 1997; 74:110-115. [PMID: 9339223 DOI: 10.1006/enrs.1997.3769] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
To clarify the effects of organic solvents on the postural balance system, 29 male sandal, shoe, and leather factory workers exposed to n-hexane, xylene, and toluene (solvent workers) were examined by computerized static posturography with sway frequency analysis. Concentrations of metabolites of solvents in urine samples taken from the workers in the morning before work ranged from 0.41 to 3.06 (mean, 1.20) mg/g creatinine (Cn) for 2,5-hexanedione, from 0.10 to 0.43 (mean, 0.19) g/g Cn for methylhippuric acid, and from 0.05 to 2.53 (mean, 0.37) g/g Cn for hippuric acid; estimated concentrations of n-hexane in workplace air ranged from 13 to 100 (mean, 40) ppm. Control subjects were 22 healthy males without exposure to solvents. With eyes open, postural sway with a frequency of 2-4 Hz in solvent workers was significantly larger than that in controls in the anteroposterior direction. With eyes closed, sway with a frequency of 0-1 Hz was significantly larger in solvent workers in the mediolateral and anteroposterior directions. Results of multiple regression analysis showed that with eyes open the 1- to 2-Hz and 2- to 4-Hz sways were related positively to 2,5-hexanedione and inversely with methylhippuric acid. The pattern of changes suggests that the vestibulocerebellar and spinocerebellar afferent systems are asymptomatically affected by n-hexane; the effect of n-hexane on the vestibulocerebellar system is possibly inhibited by xylene.
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Affiliation(s)
- K Yokoyama
- Department of Public Health, School of Medicine, University of Tokyo, Japan
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14
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Gori G, Bartolucci GB, Sturaro A, Parvoli G, Doretti L, Troiano R, Casetta B. High-performance liquid chromatographic determination of urinary 2,5-hexanedione as mono-2,4-dinitrophenylhydrazone using ultraviolet detection. JOURNAL OF CHROMATOGRAPHY. B, BIOMEDICAL APPLICATIONS 1995; 673:165-72. [PMID: 8611949 DOI: 10.1016/0378-4347(95)00257-x] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
The good correlation between exposure to n-hexane and 2,5-hexanedione urinary excretion confers on this diketone an important toxicological meaning. this paper proposes a reversed-phase HPLC method which includes, after acid hydrolysis, a derivatization step of 2,5-hexanedione with 2,4-dinitrophenylhydrazine at 70 degrees C for 20 min. The reaction conditions, such as temperature, reagent concentration and time, are optimized so as to allow the condensation of a single carbonyl group. A linear response was obtained in the 0.19-20.0 mg/l range with a detection limit of 0.03 mg/l, corresponding to a signal-to-noise ratio of 3. A phosphate buffer (pH 3.3)-acetonitrile mixture (50:50) as the eluent and UV detection at 334 nm were used.
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Affiliation(s)
- G Gori
- Istituto di Medicina del Lavoro, Università di Padova, Italy
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15
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Kawai T, Mizunuma K, Yasugi T, Horiguchi S, Iguchi H, Mutti A, Ghittori S, Ikeda M. Monitoring of exposure to methylpentanes by diffusive sampling and urine analysis for alcoholic metabolites. Occup Environ Med 1995; 52:757-63. [PMID: 8535496 PMCID: PMC1128357 DOI: 10.1136/oem.52.11.757] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
OBJECTIVES To investigate the possibilities of personal ambient monitoring and biological monitoring for methylpentane isomers. METHODS The performance of activated carbon cloth to absorb 2- and 3-methylpentane was studied by experimental vapour exposure followed by solvent extraction and gas chromatography (GC). Urine from workers and rats exposed to 2- and 3-methylpentane was analysed by GC with or without acid or enzymatic hydrolysis. RESULTS Carbon cloth absorbed 2- and 3-methylpentane linearly to exposures up to eight hours and to 400 ppm, and was sensitive enough to detect a 15 minute peak of exposure. The two isomers were clearly separated from hexane on a DB-1 column. For analysis of the urine, enzymatic hydrolysis was superior to acid hydrolysis. Exposure of rats to methylpentane vapours showed that 2-methyl-2-pentanol and 3-methyl-2-pentanol were excreted in urine in proportion to the dose of 2-methylpentane and 3-methylpentane, respectively. 2-Methyl derivatives of 1-, 3-, and 4-propanol, 2-methylpentane-2,4-diol, and 3-methyl-2-pentanol were minor metabolites. Analysis of urine from the exposed workers showed that 2-methyl- and 3-methyl-2-pentanol are leading urinary metabolites after exposure to the corresponding methylpentane. CONCLUSIONS Diffusive sampling is applicable to monitor 2- and 3-methylpentane vapours as is the case for hexane vapour. 2-Methyl-2-pentanol and 3-methyl-2-pentanol will be markers of occupational exposure to 2-methylpentane and 3-methylpentane, respectively. Also, 2-methylpentane-2,4-diol might be a marker of exposure to 2-methylpentane.
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Affiliation(s)
- T Kawai
- Osaka Occupational Health Service Center, Japan
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16
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Graham DG, Amarnath V, Valentine WM, Pyle SJ, Anthony DC. Pathogenetic studies of hexane and carbon disulfide neurotoxicity. Crit Rev Toxicol 1995; 25:91-112. [PMID: 7612176 DOI: 10.3109/10408449509021609] [Citation(s) in RCA: 138] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
Two commonly employed solvents, n-hexane and carbon disulfide (CS2), although chemically dissimilar, result in identical neurofilament-filled swellings of the distal axon in both the central and peripheral nervous systems. Whereas CS2 is itself a neurotoxicant, hexane requires metabolism to the gamma-diketone, 2,5-hexanedione (HD). Both HD and CS2 react with protein amino functions to yield initial adducts (pyrrolyl or dithiocarbamate derivatives, respectively), which then undergo oxidation or decomposition to an electrophile (oxidized pyrrole ring or isothiocyanate), that then reacts with protein nucleophiles to result in protein cross-linking. It is postulated that progressive cross-linking of the stable neurofilament during its anterograde transport in the longest axons ultimately results in the accumulation of neurofilaments within axonal swellings. Reaction with additional targets appears to be responsible for the degeneration of the axon distal to the swellings.
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Affiliation(s)
- D G Graham
- Department of Pathology, Duke University Medical Center, Durham, NC 27710, USA
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17
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Abstract
n-Hexane neuropathy was studied in 20 workers exposed for prolonged periods to this solvent, and with urinary 2,5-hexanedione concentrations exceeding the biological exposure index recommended by the American Conference of Governmental Industrial Hygienists (5 mg/L) with a mean of 11.02 mg/L (range 5.3-24.2 mg/L). Although neurological examination did not detect significant anomalies in any of the patients, and the conduction velocity and F waves of all the nerves tested were normal, neurographic studies revealed significant differences in the amplitude of sensory nerve action potentials (SNAP) recorded from the sural (mean 14.0 microV), median (mean 17.3 microV), and ulnar (mean 7.9 microV) nerves when compared with normal values from healthy adults of the same age range, examined under identical conditions. The amplitude of the SNAP in sural and median nerves correlated significantly with the number of years worked. The notable decrease in mean amplitude of the SNAP appeared to reflect the primary neurotoxic effects of 2,5-hexanedione.
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Affiliation(s)
- C Pastore
- Clinical Neurophysiology Unit (EMG), Hospital Universitari Sant Joan D'Alacant, Alicante, Spain
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18
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Periago JF, Cardona A, Marhuenda D, Roel J, Villanueva M, Marti J, Luna A. Biological monitoring of occupational exposure to n-hexane by exhaled air analysis and urinalysis. Int Arch Occup Environ Health 1993; 65:275-8. [PMID: 8144240 DOI: 10.1007/bf00381203] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
To compare two methods of biological monitoring for the evaluation of risk of occupational exposure to n-hexane, we analyze the relationship between environmental exposure to this solvent and urinary excretion of 2,5-hexanedione and n-hexane in exhaled air in 69 workers employed in the shoe industry. Environmental exposure to the solvent was monitored with personal diffusive samplers, which were desorbed with carbon sulfide and analyzed by gas chromatography. To measure 2,5-hexanedione, urine was subjected to acid hydrolysis, separation in octadecyl silane columns, elution with 5% aqueous acetonitrile solution and extraction with dichloromethane, followed by gas chromatography. In exhaled air, n-hexane was measured with a sampling system that permitted concentration of aliquots of end-exhaled air (alveolar air) from one or more exhalations in a tube packed with activated charcoal, which was then desorbed with carbon sulfide and analyzed by gas chromatography. Concentrations of n-hexane in breathing zone air were significantly correlated with urinary concentrations of 2,5-hexanedione (r = 0.88) and with exhaled air n-hexane (r = 0.86); in addition, the two biological indicators correlated significantly (r = 0.70). Analyses in both exhaled air and urine were thus considered useful for biological monitoring of the risk of exposure to n-hexane.
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Affiliation(s)
- J F Periago
- National Institute of Occupational Safety and Hygiene, Murcia, Spain
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19
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Cardona A, Marhuenda D, Martí J, Brugnone F, Roel J, Perbellini L. Biological monitoring of occupational exposure to n-hexane by measurement of urinary 2,5-hexanedione. Int Arch Occup Environ Health 1993; 65:71-4. [PMID: 8354578 DOI: 10.1007/bf00586062] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
Occupational exposure to n-hexane in shoe factory workers was monitored by measuring urinary 2,5-hexanedione, the major metabolite of this solvent and the probable cause of peripheral neuropathy in exposed workers. Solvent pollution was monitored in the work environments of 189 employees, of whom 123 (65%) worked in Alicante, Spain, and 66 (35%) in Veneto, Italy. 2,5-Hexanedione was measured in spot urine samples collected from workers at the end of the shift. Information on working conditions was obtained from a previous study. A significant linear correlation was found between mean environmental concentration of n-hexane and urinary concentration of 2,5-hexanedione. The variability in the correlation may have been due to the variable use of protective clothing (gloves), and to variations in exposure during the working week. In numerous workers, percutaneous absorption of n-hexane represented as much as 50% of the total absorbed dose. Urinary concentrations of 2,5-hexanedione tended to increase during the working week. Simultaneous exposure to n-hexane and toluene tended to reduce urinary excretion of 2,5-hexanedione, whereas exposure to n-hexane and methyl ethyl ketone tended to increase excretion of the metabolite.
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Affiliation(s)
- A Cardona
- Department of Toxicology and Legal Medicine, School of Medicine, University of Alicante, Spain
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20
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Kawai T, Yasugi T, Mizunuma K, Horiguchi S, Iguchi H, Uchida Y, Iwami O, Ikeda M. Comparative evaluation of urinalysis and blood analysis as means of detecting exposure to organic solvents at low concentrations. Int Arch Occup Environ Health 1992; 64:223-34. [PMID: 1468790 DOI: 10.1007/bf00378279] [Citation(s) in RCA: 47] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
One hundred and forty-three workers exposed to one or more of toluene, xylene, ethylbenzene, styrene, n-hexane, and methanol at sub-occupational exposure limits were examined for the time-weighted average intensity of exposure by diffusive sampling, and for biological exposure indicators by means of analysis of shift-end blood for the solvent and analysis of shift-end urine for the corresponding metabolite(s). Urinalysis was also performed in 20 nonexposed control men to establish the "background level." Both solvent concentrations in blood and metabolite concentrations in urine correlated significantly with solvent concentrations in air. Comparison of blood analysis and urinalysis as regards sensitivity in identifying low solvent exposure showed that blood analysis is generally superior to urinalysis. It was also noted that estimation of exposure intensity on an individual basis is scarcely possible even with blood analysis. Solvent concentration in whole blood was the same as that in serum in the case of the aromatics, except for styrene. It was higher in blood than in serum in the case of n-hexane, and lower in the cases of styrene and methanol.
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Affiliation(s)
- T Kawai
- Osaka Occupational Health Service Center, Japan
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