1
|
Davis JA, Kraft A. Quantitative meta-analytic approaches for the systematic synthesis of data and hazard identification: A case study of decreased pain sensitivity due to trimethylbenzene exposure. Environ Res 2017; 158:598-609. [PMID: 28719868 PMCID: PMC11017105 DOI: 10.1016/j.envres.2017.07.017] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/20/2016] [Revised: 07/06/2017] [Accepted: 07/07/2017] [Indexed: 06/07/2023]
Abstract
Traditionally, human health risk assessments have relied on qualitative approaches for hazard identification, which involves weight of evidence determinations that integrate evidence across multiple studies. Recently, the National Research Council has recommended the development of quantitative approaches for evidence integration, including the application of meta-analyses, to help summarize and evaluate the results of a systematic review. In the meta-analytic approach, a pooled effect size is calculated after consideration of multiple potential confounding factors in order to determine whether the entire database under consideration indicates a chemical is a hazard. The following case-study applies qualitative and quantitative approaches to determine whether trimethylbenzene (TMB) isomers represent a neurotoxic hazard, specifically focusing on pain sensitivity. Following a thorough literature search, the only pain sensitivity studies available for TMBs initially seem discordant in their results: effects on pain sensitivity are seen immediately after termination of exposure, appear to resolve 24h after exposure, and then reappear 50 days later following foot-shock. Qualitative consideration of toxicological and toxicokinetic characteristics of the TMB isomers suggests that the observed differences between studies are likely due to testing time and the application of external stressors. Meta-analyses and -regressions support this conclusion: when all studies are included and possible confounders (isomer, testing time, laboratory, etc.) are accounted for, the pooled effect sizes are statistically significant, thus supporting that TMBs are a possible neurotoxic hazard to human health. Ultimately, this case study demonstrates how qualitative and quantitative methods can be combined to provide a robust hazard identification analysis by incorporating more of the available information.
Collapse
Affiliation(s)
- J Allen Davis
- National Center for Environmental Assessment, Office of Research and Development, US Environmental Protection Agency, United States.
| | - Andrew Kraft
- National Center for Environmental Assessment, Office of Research and Development, US Environmental Protection Agency, United States
| |
Collapse
|
2
|
|
3
|
Adenuga D, Carrillo J, Mckee RH. The sub-chronic oral toxicity of 1,3,5-trimethylbenzene in Sprague–Dawley rats. Regul Toxicol Pharmacol 2014; 69:143-53. [DOI: 10.1016/j.yrtph.2014.03.006] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2013] [Revised: 03/18/2014] [Accepted: 03/21/2014] [Indexed: 11/22/2022]
|
4
|
Abstract
We have constructed an in silico system for the prediction of CYP2E1-mediated reaction using a two-dimensional template derived from substrate structures. Although CYP2E1 prefers small-size molecules for the substrates, the enzyme mediates oxidations of large-size molecules, such as benzo[a]pyrene. Overlays of these substrates, to assemble their sites of oxidation into a specific area, suggested a range of regions frequently occupied. The region, having a benzo[a]pyrene-like shape, was thus used as a CYP2E1 template. In this system, atoms in substrates, except for hydrogen atoms, were placed on corners of honeycomb structures of the template after having expanded the structures. Using published data for the metabolism on more than 80 substrates of CYP2E1, the core template was further refined to verify the adjacent area and to define the relative contribution of template positions for the catalysis. The positions on the template were classified into four different point (0-3) groups, depending on relative usage. In addition, we set independent points (-5 to 3) for specific positions to incorporate three-dimensional or functional information. Total scores from both position-occupancy and -function points were calculated for all the orientations of possible conformers of test substrates, and the scores were found to predict the relative abundance (i.e., order) as well as the regioselectivity of human CYP2E1 reactions with high fidelities.
Collapse
Affiliation(s)
- Yasushi Yamazoe
- Division of Drug Metabolism and Molecular Toxicology, Graduate School of Pharmaceutical Sciences, Tohoku University , Sendai , Japan
| | | | | |
Collapse
|
5
|
Yoshida T. Estimation of absorption of aromatic hydrocarbons diffusing from interior materials in automobile cabins by inhalation toxicokinetic analysis in rats. J Appl Toxicol 2011; 30:525-35. [PMID: 20809541 DOI: 10.1002/jat.1522] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Aromatic hydrocarbons, as well as aliphatic hydrocarbons, diffusing from interior materials in automotive cabins are the most common compounds contributing to interior air pollution. In this study, the amounts of seven selected aromatic hydrocarbons absorbed by a car driver were estimated by evaluating their inhalation toxicokinetics in rats. Measured amounts of these substances were injected into a closed chamber system containing a rat, and the concentration changes in the chamber were examined. The toxicokinetics of the substances were evaluated on the basis of the concentration-time course using a nonlinear compartment model. The amounts absorbed in humans at actual concentrations in automobile cabins without ventilation were extrapolated from the results obtained from rats. The absorbed amounts estimated for a driver during a 2 h drive were as follows (per 60 kg of human body weight): 30 microg for toluene (interior median concentration, 40 microg m(-3) in our previous study), 10 microg for ethylbenzene (12 microg m(-3)), 6 microg for o-xylene (10 microg m(-3)), 8 microg for m-xylene (11 microg m(-3)), 9 microg for p-xylene (11 microg m(-3)), 11 microg for styrene (11 microg m(-3)) and 27 microg for 1,2,4-trimethylbenzene (24 microg m(-3)). Similarly, in a cabin where air pollution was marked, the absorbed amount of styrene (654 microg for 2 h in a cabin with an interior maximum concentration of 675 microg m(-3)) was estimated to be much higher than those of other substances. This amount (654 microg) was approximately 1.5 times the tolerable daily intake of styrene (7.7 microg kg(-1) per day) recommended by the World Health Organization.
Collapse
Affiliation(s)
- Toshiaki Yoshida
- Osaka Prefectural Institute of Public Health, 1-3-69, Nakamichi, Higashinari-ku, Osaka 537-0025, Japan.
| |
Collapse
|
6
|
Abstract
The main metabolites of o-xylene in urine are o-methylhippuric acid, o-toluic acid, o-toluic acid glucuronide, 3,4-dimethylphenol, 3,4-dimethylphenol conjugates and o-xylylmercapturic acid. The urinary excretion of o-toluic acid, o-toluic acid conjugates and o-xylene were increased by the prior administration of sodium benzoate. Conversely, the amounts of o-methylhippuric acid, 3,4-dimethylphenol conjugates and o-xylylmercapturic acid decreased by sodium benzoate pretreatment. In addition, the urinary excretion of o-methylhippuric acid was delayed by the pretreatment. The percentages of urinary excretion of the o-xylene metabolites were substantially changed by the pretreatment with sodium benzoate. These results therefore highlight a potential interaction of an air pollutant with a food additive, an interaction that remains to be established in man.
Collapse
Affiliation(s)
- H Moriwaki
- Osaka City Institute of Public Health and Environmental Sciences, Osaka, Japan
| | | | | | | | | | | |
Collapse
|
7
|
Tsujimoto Y, Warashina M, Nam VD, Noda T, Shimizu M, Yamaguchi Y, Moriwaki H, Morimoto T, Kakiuchi K, Maeda Y, Tanaka M. Determination of Urinary Phenolic Metabolites from Rats Treated with 1,2,3‐ and 1,3,5‐ Trimethylbenzenes. J Occup Health 2005; 47:337-9. [PMID: 16096360 DOI: 10.1539/joh.47.337] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Affiliation(s)
- Yuji Tsujimoto
- Osaka City Institute of Public Health and Environmental Sciences, Osaka, Japan.
| | | | | | | | | | | | | | | | | | | | | |
Collapse
|
8
|
Saillenfait AM, Gallissot F, Sabate JP, Morel G. Developmental toxicity of two trimethylbenzene isomers, mesitylene and pseudocumene, in rats following inhalation exposure. Food Chem Toxicol 2005; 43:1055-63. [PMID: 15833381 DOI: 10.1016/j.fct.2005.02.008] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2004] [Revised: 02/09/2005] [Accepted: 02/15/2005] [Indexed: 10/25/2022]
Abstract
The developmental toxicity of two trimethylbenzene isomers, mesitylene (1,3,5-trimethylbenzene) and pseudocumene (1,2,4-trimethylbenzene) was studied in Sprague-Dawley rats following inhalation exposure. Pregnant rats were exposed whole body to vapours of mesitylene (0, 100, 300, 600, and 1200 ppm) or pseudocumene (0, 100, 300, 600, and 900 ppm), 6h/day, on gestational days (GD) 6 through 20. Significant decrease in maternal body weight gain and food consumption was observed at concentrations of 300 ppm mesitylene, 600 ppm pseudocumene, or greater. Fetal toxicity, expressed as significant reduction in fetal body weight, occurred at 600 and 1200 ppm mesitylene, and at 600 and 900 ppm pseudocumene. There was no evidence of embryolethal or teratogenic effects following inhalation exposure to either of these chemicals. In summary, the no-observed-adverse-effect-level (NOAEL) for maternal toxicity was 100 ppm for mesitylene and 300 ppm for pseudocumene, and the NOAEL for developmental toxicity was 300 ppm for mesitylene and pseudocumene.
Collapse
Affiliation(s)
- A M Saillenfait
- Institut National de Recherche et de Sécurité, Avenue de Bourgogne, B.P. No. 27, 54501 Vandoeuvre, France.
| | | | | | | |
Collapse
|
9
|
Moriwaki H, Watanabe A, Arakawa R, Tsujimoto Y, Shimizu M, Noda T, Warashina M, Tanaka M. Simultaneous determination of metabolites of trimethylbenzenes, dimethylbenzylmercapturicacid and dimethylhippuric acid, in human urine by solid-phase extraction followed by liquid chromatography tandem mass spectrometry. J Mass Spectrom 2002; 37:1152-1157. [PMID: 12447892 DOI: 10.1002/jms.378] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
We describe a novel method for the determination of three kinds of dimethylbenzylmercapturic acids (DMM) and six kinds of dimethylhippuric acids (DMH), found in urine as metabolites of trimethylbenzenes, based on liquid chromatography/electrospray ionization tandem mass spectrometry. A solid-phase extraction procedure was used for the extractions of DMM and DMH from a urine sample, and the separation was performed on a reversed-phase C(30) column. The analytes were ionized by electrospray in the positive-ion mode. Operating in the multiple reaction monitoring mode, the linearity of the relative mass spectrometric responses to the internal standard versus analyte concentrations were established in the range 0.1-100 ng ml(-1). The extraction procedure was rapid and the relative standard deviations were below 5%. The detection limits of DMM and DMH in the urine by the proposed method were in the ranges 0.26-0.41 and 0.42-2.0 ng l(-1), respectively. Furthermore, DMM and DMH were detected in a urine sample from an individual who did not suffer from occupational exposure to trimethylbenzenes, by using this method.
Collapse
Affiliation(s)
- Hiroshi Moriwaki
- Osaka City Institute of Public Health and Environmental Sciences, 8-34, Tojo-cho, Tennoji-ku, Osaka 543-0026, Japan.
| | | | | | | | | | | | | | | |
Collapse
|
10
|
Abstract
Trimethylbenzene (TMB), like xylene (dimethylbenzene), is a significant constituent of some industrial solvent mixtures. In earlier studies, we found that in the rat a subacute low-level inhalation exposure to some of the TMB isomers may result in behavioral alterations detectable weeks after the exposure [Neurotoxicol Teratol 19;1997:327; Int J Occup Med Environ Health 11;1998:319]. The purpose of the present study was to compare m-xylene (XYL) and each of the TMB isomers: 1,2,3-TMB (hemimellitene - HM), 1,2,4-TMB (pseudocumene - PS), and 1,3,5-TMB (mesitylene - MES) with respect to the ability for inducing behavioral effects in the rat. The rats (10-11 animals per group) were exposed repeatedly for 4 weeks (6 h per day, 5 days per week) to XYL (XYL group), HM (HM group), PS (PS group) or MES (MES group) at 100 ppm, or sham exposed (C group) in 1.3 cu/m dynamic inhalation chambers. Starting 2 weeks after exposure the following forms of rat's behavior were assessed: radial maze performance, spontaneous activity in an open field, learning and retention of passive and active (two-way) avoidance response, and heat-induced paw licking before and after a 2 min footshock (a test for assessment of the stress response). None of the solvent-exposed groups differed considerably from the control one with respect to the radial maze performance. Compared to control rats, the rats of the XYL, PS and MES groups, but not those of HM group, showed a significantly higher spontaneous locomotor activity in the open field, an impaired passive avoidance learning and significantly longer paw-lick latencies 24 h after footshock. Acquisition, but not retention, of the two-way active avoidance response was significantly impaired in all solvent-exposed groups. The XYL group did not differ significantly from PS, MES or HM group in any of the behavioral parameters. The above results show that a short-term exposure to any of the TMB isomers or m-xylene at concentration as low as 100 ppm may induce persistent behavioral alterations in the rat.
Collapse
Affiliation(s)
- S Gralewicz
- Department of Toxicology and Carcinogenesis, Nofer Institute of Occupational Medicine, Lódź, Poland.
| | | |
Collapse
|
11
|
Tsujimoto Y, Noda T, Shimizu M, Moriwaki H, Tanaka M. Identification of the dimethylbenzyl mercapturic acid in urine of rats administered with 1,2,4-trimethylbenzene. Chemosphere 2000; 40:893-896. [PMID: 10718583 DOI: 10.1016/s0045-6535(99)00467-1] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
A study was undertaken of the mercapturic acid metabolism of 1,2,4-trimethylbenzene in the rat. Of three regioisomeric dimethylbenzyl mercapturic acids, i.e. 2,4-, 2,5- and 3,4-dimethylbenzyl isomers, the third isomer was not found in the urinary mercapturic acid isolated by preparative HPLC, from the comparison of NMR spectrum of the isolate with those of authentic specimens. The urinary mercapturate was then assigned to 2,4- and/or 2,5-dimethylbenzyl isomers. The excretion rate of the mercapturic acid was 14-20% of dose as 2,4-dimethylbenzyl isomer.
Collapse
Affiliation(s)
- Y Tsujimoto
- Osaka City Institute of Public Health and Environmental Sciences, Japan
| | | | | | | | | |
Collapse
|
12
|
Tsujimoto Y, Noda T, Shimizu M, Moriwaki H, Tanaka M. Identification of the dimethylbenzyl mercapturic acid in urine of rats treated with 1,2,3-trimethylbenzene. Chemosphere 1999; 39:725-730. [PMID: 10448551 DOI: 10.1016/s0045-6535(99)00008-9] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
The structure was investigated of the mercapturic acid excreted in urine of rats after the i.p. administration of 1,2,3-trimethylbenzene. Of the two regioisomeric mercapturic acids, i.e. N-acetyl-S-(2,3-dimethylbenzyl)-L-cysteine and N-acetyl-S-(2,6-dimethyl-benzyl)-L-cysteine, only the former was isolated by preparative HPLC and identified, by comparison with an authentic specimen. The excretion rate of the mercapturate was estimated to be approximately 5% of dose, not a substantial metabolic route.
Collapse
Affiliation(s)
- Y Tsujimoto
- Osaka City Institute of Public Health and Environmental Sciences, Japan
| | | | | | | | | |
Collapse
|
13
|
Fukaya Y, Saito I, Matsumoto T, Takeuchi Y, Tokudome S. Determination of 3,4-dimethylhippuric acid as a biological monitoring index for trimethylbenzene exposure in transfer printing workers. Int Arch Occup Environ Health 1994; 65:295-7. [PMID: 8175183 DOI: 10.1007/bf00405692] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
The relationship between exposure to 1,2,4-trimethylbenzene (1,2,4-TMB) and urinary concentration of 3,4-dimethylhippuric acid (3,4-DMHA), one of its metabolites, was studied in workers involved in transfer printing. Airborne TMBs were sampled by an organic vapor monitoring badge and analyzed by capillary gas chromatography. Urinary 3,4-DMHA and creatinine were analyzed under the same conditions of high-performance liquid chromatography. The exposure concentration of 1,2,4-TMB among workers was around 25 ppm, the threshold limit value (TLV). The urinary concentration of 3,4-DMHA was low at the start of each shift and high at the end. Exposure to the TLV (25 ppm) of 1,2,4-TMB results in a urinary 3,4-DMHA concentration of 410 mg/g creatinine (r = 0.897, P < 0.001). Urinary 3,4-DMHA concentration could be used as a biological monitoring index for 1,2,4-TMB exposure.
Collapse
Affiliation(s)
- Y Fukaya
- Department of Public Health, Nagoya City University Medical School, Japan
| | | | | | | | | |
Collapse
|
14
|
Ichiba M, Hama H, Yukitake S, Kubota M, Kawasaki S, Tomokuni K. Urinary excretion of 3,4-dimethylhippuric acid in workers exposed to 1,2,4-trimethylbenzene. Int Arch Occup Environ Health 1992; 64:325-7. [PMID: 1487328 DOI: 10.1007/bf00379541] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
The urinary excretion of 3,4-dimethylhippuric acid (34DMHA), a 1,2,4-trimethylbenzene (124TMB) metabolite, was investigated in workers exposed to 124TMB vapor. The time-weighted average of exposure to 124TMB was determined with a diffusive sampler. For biological monitoring of exposure, urine samples were collected from individual workers and analyzed for metabolites by high-pressure liquid chromatography. The concentration of urinary 34DMHA had a positive correlation with the level of exposure to 124TMB (r = 0.72). The data suggest that 34DMHA is one of the useful indicators for biological monitoring of 124TMB exposure.
Collapse
Affiliation(s)
- M Ichiba
- Department of Community Health Science, Saga Medical School, Japan
| | | | | | | | | | | |
Collapse
|
15
|
Busini S, Bavazzano P, Occhiato E. High-performance liquid chromatographic determination of 3,5-dimethylhippuric acid in the occupational exposure to trimethylbenzenes. J Chromatogr 1992; 577:180-4. [PMID: 1400739 DOI: 10.1016/0378-4347(92)80617-y] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
A high-performance liquid chromatographic method for the measurement of urinary 3,5-dimethylhippuric acid (3,5-DMHA) in the human biological monitoring of the occupational exposure to trimethylbenzenes has been developed. 3,5-DMHA was extracted from urine with ethyl acetate. The organic phase was dried under vacuum and the resultant product, dissolved in the mobile phase, was analysed by an isocratic system and a programmable photodiode-array detector adjusted to 205 nm. The mobile phase was water-acetonitrile (80:20, v/v) containing 0.1% acetic acid. 3,5-DMHA was chromatographed on a reversed-phase Supelco C18 column (3 microns; 15 cm x 0.46 cm I.D.), and identified by its retention time and ultraviolet spectrum. Quantitation was performed by peak area. The detection limit of the method is 30 ng/ml and the recovery and the accuracy are 96%.
Collapse
Affiliation(s)
- S Busini
- Industrial Toxicology, U.S.L. 10/A, Florence, Italy
| | | | | |
Collapse
|