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Toluene is a highly flammable and commonly used industrial chemical with severe health consequences on humans upon exposure and ingestion. In this study, multispecies bioassays were conducted using a species sensitivity distribution approach to determine acute and chronic hazardous concentrations of toluene in soil. Acute and chronic toluene toxicity tests were conducted with seven soil species from four taxonomic groups. The results from the toxicity tests were used to estimate the acute and chronic HC5 (hazardous concentration for 5 % of species) of toluene in the terrestrial environment at 58.9 (5.4–639.6) mg kg−1 and 2.2 (0.2–19.8) mg kg−1, respectively. To the best of our knowledge, this is the first study to estimate the hazardous concentration of toluene in soil by conducting a battery of bioassays. These values can be used as references for the environmental risk assessment of chemical accidents involving toluene and estimating its impact on soil to protect the terrestrial environment.

TOPIC: Critical Care TYPE: Medical Student/Resident Case Reports INTRODUCTION: Toluene is an aromatic hydrocarbon widely used as a solvent in industrial and commercial products including paints, adhesives, ink, and rubber. It is occasionally used as an inhalant drug for its intoxicating properties. While mostly known for producing neurologic effects, here we report a case of toluene induced acute lung injury. CASE PRESENTATION: A 61-year-old female with a medical history of alcohol abuse, depression, congestive heart failure with preserved ejection fraction presented with one week of weakness and shortness of breath. She had been seen twice in the week prior having tested negative for SARS-COV2. In the emergency department, O2 saturation was 70% with respiratory distress on room air requiring high flow nasal cannula support. Labs were notable for a potassium of 2.7 mmol/L, acute kidney injury, elevated transaminases, lactate of 2.8 mmol/L and leukocyte count of 9800/nL. CT showed diffuse bilateral ground glass opacities involving the lung parenchyma concerning for atypical including viral pneumonia. Upon admission to the ICU she developed worsening hypoxia and respiratory failure requiring intubation.A discussion with the patient's husband revealed she had a history of glue sniffing. She had recently been decreasing her alcohol intake and substituting this with an increased frequency of sniffing both permanent markers and modeling glue. This raised suspicion for chemical pneumonitis secondary to toluene induced acute lung injury. DISCUSSION: Toluene is a highly lipophilic molecule readily inhaled via the lungs and distributed widely throughout the body producing side effects like ethanol intoxication via interfering mainly with GABA receptors. Neurologic manifestations range from euphoria and hallucinations to cognitive dysfunction and ataxia with chronic use. It specifically causes renal tubular acidosis typically manifesting as a normal anion gap hyperchloremic acidosis with hypokalemia. It can also cause hepatic injury and cardiac automaticity and conduction abnormalities.Acute lung injury secondary to toluene has been described but less frequently reported. Toxicity can result in Reactive Airway Dysfunction Syndrome (RADS) from acute or chronic exposure to various chemical irritants. All hydrocarbons, including toluene, can cause chemical pneumonitis by direct contact with the pulmonary parenchyma and destroying alveolar and capillary membranes resulting in vascular permeability and edema. Symptoms may include cough, wheezing, respiratory distress, and hypoxia. Bilateral interstitial infiltrates may be delayed for several hours after the development of pneumonitis. There is no specific antidote for toluene toxicity. CONCLUSIONS: Treatment for toluene and many chemical induced pneumonitides consists of supportive care, supplemental oxygen, bronchodilators, inhaled and systemic glucocorticoids and may require intubation and admission to an ICU in severe cases. REFERENCE #1: Camara-Lemarroy CR, Rodriguez-Gutierrez R, Monreal-Robles R, Gonzalez-Gonzalez JG. Acute toluene intoxication–clinical presentation, management and prognosis: a prospective observational study. BMC Emerg Med. 2015;15:19. Published 2015 Aug 18. doi:10.1186/s12873-015-0039-0 REFERENCE #2: Alberts WM, do Pico GA. Reactive airways dysfunction syndrome. Chest. 1996;109(6):1618-1626. doi:10.1378/chest.109.6.1618 REFERENCE #3: Tormoehlen LM, Tekulve KJ, Nanagas KA. Hydrocarbon toxicity: A review. Clin Toxicol (Phila). 2014;52(5):479-489. doi:10.3109/15563650.2014.923904 DISCLOSURES: No relevant relationships by Ryan Lee, source=Web Response No relevant relationships by Dominic Valentino, source=Web Response

Toluene is a highly volatile organic solvent present in gasoline. Exposure mainly occurs by absorption via the pulmonary tract and easily reaches the central nervous system, which causes toxic effects. Toluene toxicity has been described but not well established. The present work aimed to evaluate the effects of airborne exposure to toluene, the in vivo model Caenorhabditis elegans was assessed to determine whether nematode could be used to evaluate the effects of exposure to toluene and the possible mechanisms of toxicity of the solvent. Worms at the first or fourth larval stages were exposed to toluene for 48 or 24 h, respectively, in a laboratory-developed vapor chamber at concentrations of 450, 850, 1250 and 1800 ppm. We observed increases in worm mortality and significant developmental delays that occurred in a concentration-dependent manner. An increased incidence of apoptotic events in treated germline cells was shown, which was consistent with observed reductions in reproductive capacity. In addition, toluene promoted significant behavioural changes affecting swimming movements and radial locomotion, which were associated with changes in the fluorescence intensity and morphology of GABAergic and cholinergic neurons. We conclude that toluene exposure was toxic to C. elegans, with effects produced by the induction of apoptosis and neuronal damage.

We present the case of a 25-year-old man with progressive limb weakness. His electrocardiogram showed prominent U waves which made us consider hypokalemia. The final diagnosis was toluene intoxication with severe hypokalemia and metabolic acidosis. Intravenous potassium administration and hydration effectively corrected the electrolyte and acid-base alterations; weakness resolved and the patient was discharged. The approach to a patient with acute weakness can be challenging. This case reminds us that the electrocardiogram can be a valuable tool in the evaluation and differential diagnosis of patients presenting to the emergency department with these conditions.

A number of bacteria can use toxic compounds as carbon sources and have developed complex regulatory networks to protect themselves from the toxic effects of these compounds as well as to benefit from their nutritious properties. As a model system we have studied the responses of Pseudomonas putida strains to toluene. Although this compound is highly toxic, several strains are able to use it for growth. Particular emphasis was given to the responses in the context of taxis, resistance and toluene catabolism. P. putida strains analysed showed chemotactic movements towards toluene. Strain DOT-T1E was characterised by an extreme form of chemotaxis, termed hyperchemotaxis, which is mediated by the McpT chemoreceptor encoded by plasmid pGRT1. Close McpT homologs are found in a number of other plasmids encoding degradation pathways of toxic compounds. The pGRT1 plasmid harbours also the genes for the TtgGHI efflux pump which was identified as the primary determinant for the resistance of strain DOT-T1E towards toluene. Pump expression is controlled by the TtgV repressor in response to a wide range of different mono- and biaromatic compounds. Strain DOT-T1E is able to degrade toluene, benzene and ethylbenzene via the toluene dioxygenase (TOD) pathway. The expression of the pathway operon is controlled by the TodS/T two component system. The sensor kinase TodS recognizes toluene with nanomolar affinity, which in turn triggers an increase in its autophosphorylation and consequently transcriptional activation. Data suggest that transcriptional activation of the TOD pathway occurs at very low toluene concentrations whereas TtgV mediated induction of pump expression sets in as the toluene concentration further increases.

The present study was designed to investigate the possible involvement of TLR4 pathway in the mouse hippocampus following toluene exposure. Male C3H/HeN and C3H/HeJ (TLR4 defective) mice were exposed to 0, 5, 50 or 500 ppm of toluene for 6 weeks. The expressions of TLR4-related signal transduction pathway mRNAs in the hippocampi were examined using real-time RT-PCR and an immunohistochemical analysis. In C3H/HeN mice, the relative mRNA expression levels of TLR4 and NF-κB activating protein were significantly up-regulated in the groups exposed to toluene, but not in the C3H/HeJ mice. Heat shock protein 70, a possible endogenous ligand for TLR4, mRNA was increased in the C3H/HeN mice exposed to toluene. This is the first report to show that TLR4 may have a role in the neurotoxic effects in mice exposed to toluene.

We aim to investigate the critical window of susceptibility to toluene exposure during brain development and the effects of fetal and neonatal toluene exposure on the expression of N-methyl-d-aspartate (NMDA) receptor subunits and related transduction pathway in infant mice hippocampus. Pregnant mice (GD 14), male offspring (postnatal day; PND 2) or PND 8 were exposed to either a filtered air control (0ppm), or 5, or 50ppm of toluene for 6h per day for 5 consecutive days. On PND 21, the expression levels of NMDA receptor subunits, cyclic AMP responsive element binding protein (CREB)-1, calcium/calmodulin-dependent protein kinase (CaMK)-IV, and apoptotic related genes (Bax, Bcl) mRNAs in the hippocampus were estimated using quantitative real-time RT-PCR and immunohistochemical analyses. NR2B, CaMKIV and CREB1 mRNAs increased significantly in the hippocampus of mice exposed to 50ppm toluene on PND 2-6. In contrast, almost all memory function-related gene mRNAs and proapoptotic and anti-apoptotic ratio increased significantly in mice exposed to 5 or 50ppm toluene on PND 8-12. However, mice exposed to toluene on GD 14-18 showed no significant change. Increased active caspase-3 immunoreactive cells were found in hippocampal CA1 area of PND 21 male mice exposed to 5ppm toluene during PND 8-12. Our results suggest that late postnatal period may be a vulnerable and critical period to toluene exposure. Then, we have also examined the effect of toluene exposure in brain development on learning ability in young adult mice and found that poor spatial learning performance in PND 49 male mice exposed to 5ppm toluene during critical period. This is the first study to show that the early toluene exposure induces persistent of the alteration of memory function-related genes in infant mice and memory deficit in later life via modulating the synaptic morphology and function.

We have previously shown that toluene inhalation produces significant impairments in the basilar dendritic outgrowth of pyramidal cortical cells. This neurotoxic effect was markedly inhibited by melatonin administration at a dose of 5mg kg(-1). The present study was designed to determine whether toluene and melatonin equally affect all basilar dendritic segments or if a differential response exists between the segments. Twenty-eight male mice were weaned at postnatal day 21 (P21) and randomly assigned to either the control (C; n=10,) or toluene (T; n=18) group. Between P22-P32, male rats were placed into a glass chamber and exposed to either toluene vapors (5-000-6000 ppm) or clean air for 10 min a day. When toluene exposure ended (P32), animals were further assigned to the following experimental groups: (a) control/saline (C/S; n=10), (b) toluene/saline (T/S; n=10), or (c) toluene/melatonin 5mg kg(-1) (T/M; n=8). Melatonin or vehicle solutions were administered daily between P32 and P38. Forty-eight hours after the final toluene exposure, the animals were sacrificed, and the pyramidal cortical cells were stained using the Golgi-Cox-Sholl procedure. The number of basilar dendritic branches/order was counted using the centrifugal ordering method. The results indicate that (i) toluene inhalation significantly impairs both proximal and distal basilar dendritic ramifications (in the parietal and frontal/occipital cortices, respectively) and (ii) melatonin both protects neurons from toluene neurotoxicity in all cortical areas studied and increases the complexity of the dendritic tree above control values.

Benzene, toluene and xylene are monocyclic aromatic hydrocarbon compounds, used both as individual compound and as mixtures, in industry as well as household. Previous studies involving exposures to these compounds, individually, have shown that benzene was more toxic compared to toluene or xylene. Here, we tested a working hypothesis that toluene and/or xylene in a mixture containing benzene affect benzene induced toxicity in a non-target organism, Drosophila melanogaster . We exposed D. melanogaster larvae transgenic for hsp70 , hsp83 or hsp26 and wild type (Oregon R strain) larvae to 25.0–100.0 mM benzene, 25.0–100.0 mM toluene and 25.0–100 mM xylene, individually or in mixtures. Subsequently, we examined the expression of stress genes (encoding heat shock proteins, hsps), generation of reactive oxygen species (ROS), induction of anti-oxidant stress markers and emergence of flies under treatment as well as control conditions. We observed that all these endpoints were significantly altered in all the treatment groups compared to their respective controls. However, the magnitude of toxicity of a benzene–toluene (BT) or benzene–xylene (BX) or benzene–toluene–xylene (BTX) mixture was significantly lower in the organism than that of individual chemical. Our results also show the modulation of toluene toxicity by xylene. Present study suggests antagonistic effect of xylene and toluene on benzene toxicity and additive/synergistic effect of xylene on toluene induced toxicity. Thus, expression of stress genes may be used as an assay for detection of early cellular toxicity. Further, our study supports the use of Drosophila as an alternative animal model for first tier screening of adverse effects of chemical mixtures.

Benzene is an important industrial chemical. At certain levels, benzene has been found to produce aplastic anemia, pancytopenia, myeloblastic anemia and genotoxic effects in humans. Metabolism by cytochrome P450 monooxygenases and myeloperoxidase to hydroquinone, phenol, and other metabolites contributes to benzene toxicity. Other xenobiotic substrates for cytochrome P450 can alter benzene metabolism. At high concentrations, toluene has been shown to inhibit benzene metabolism and benzene-induced toxicities. The present study investigated the genotoxicity of exposure to benzene and toluene at lower and intermittent co-exposures. Mice were exposed via whole-body inhalation for 6h/day for 8 days (over a 15-day time period) to air, 50 ppm benzene, 100 ppm toluene, 50 ppm benzene and 50 ppm toluene, or 50 ppm benzene and 100 ppm toluene. Mice exposed to 50 ppm benzene exhibited an increased frequency (2.4-fold) of micronucleated polychromatic erythrocytes (PCE) and increased levels of urinary metabolites (t,t-muconic acid, hydroquinone, and s-phenylmercapturic acid) vs. air-exposed controls. Benzene co-exposure with 100 ppm toluene resulted in similar urinary metabolite levels but a 3.7-fold increase in frequency of micronucleated PCE. Benzene co-exposure with 50 ppm toluene resulted in a similar elevation of micronuclei frequency as with 100 ppm toluene which did not differ significantly from 50 ppm benzene exposure alone. Both co-exposures - 50 ppm benzene with 50 or 100 ppm toluene - resulted in significantly elevated CYP2E1 activities that did not occur following benzene or toluene exposure alone. Whole blood glutathione (GSH) levels were similarly decreased following exposure to 50 ppm benzene and/or 100 ppm toluene, while co-exposure to 50 ppm benzene and 100 ppm toluene significantly decreased GSSG levels and increased the GSH/GSSG ratio. The higher frequency of micronucleated PCE following benzene and toluene co-exposure when compared with mice exposed to benzene or toluene alone suggests that, at the doses used in this study, toluene can enhance benzene-induced clastogenic or aneugenic bone marrow injury. These findings exemplify the importance of studying the effects of binary chemical interactions in animals exposed to lower exposure concentrations of benzene and toluene on benzene metabolism and clastogenicity. The relevance of these data on interactions for humans exposed at low benzene concentrations can be best assessed only when the mechanism of interaction is understood at a quantitative level and incorporated within a biologically based modeling framework.

The contributing role of indoor air pollution to the development of allergic disease has become increasingly evident in public health problems. It has been reported that extensive communication exists between neurons and immune cells, and neurotrophins are molecules potentially responsible for regulating and controlling this neuroimmune crosstalk. The adverse effects of volatile organic compounds which are main indoor pollutants on induction or augmentation of neuroimmune interaction have not been fully characterized yet. To investigate the effects of low-level toluene inhalation on the airway inflammatory responses, male C3H mice were exposed to filtered air (control), 9 ppm, and 90 ppm toluene for 30 min by nose-only inhalation on Days 0, 1, 2, 7, 14, 21, and 28. Some groups of mice were injected with ovalbumin intraperitoneally before starting exposure schedule and these mice were then challenged with aerosolized ovalbumin as booster dose. For analysis of airway inflammation, bronchoalveolar lavage (BAL) fluid were collected to determine inflammatory cell influx and lung tissue and blood samples were collected to determine cytokine and neurotrophin mRNA and protein expressions and plasma antibody titers using real-time RT-PCR and ELISA methods respectively. Exposure of the ovalbumin-immunized mice to low-level toluene resulted in (1) increased inflammatory cells infiltration in BAL fluid; (2) increased IL-5 mRNA, decreased nerve growth factor receptor tropomyosin-related kinase A and brain-derived neurotrophic factor mRNAs in lung; and (3) increased IgE and IgG(1) antibodies and nerve growth factor content in the plasma. These findings suggest that low-level toluene exposure aggravates the airway inflammatory responses in ovalbumin-immunized mice by modulating neuroimmune crosstalk.

The developmental toxicity of toluene was evaluated via whole body inhalation exposure, in pregnant Sprague Dawley rats exposed to toluene (99.9% pure) from gestation day (GD) 6-15 inclusive, 6h/day, at concentrations of 0, 250, 750, 1500 and 3000ppm (0, 938, 2812, 5625 and 11250mg/m(3)). Doses were selected from a preliminary study performed over a range of concentrations from 0 to 5000ppm, in which maternal and fetal toxicity were observed at 2000ppm and above. This study has been cited in various regulatory documents and is presented here to allow greater accessibility to results and conclusions. Toluene induced clinical signs in pregnant dams (ataxia, hyper-responsivity, increased water intake, decreased food consumption) at 3000ppm, ataxia and hyper-responsivity at 1500ppm, and reduced maternal body weight gain at 1500 during the exposure period only and at 3000ppm from initiation of exposure to GD20. At Caesarean section on GD20, no adverse effects on implantation, number and viability of fetuses, or fetal sex distribution were observed. Litter weight and mean fetal weight was reduced at 3000ppm and mean fetal weight was reduced at 1500ppm. Instances of reduced or unossified skeletal elements occurred at the same dose levels. Mean fetal weight was also reduced at 250ppm but not at 750ppm. Extensive statistical analysis of fetal body weight data support the conclusion that there is no toxicologically significant dose-related effect on fetal body weight at or below 750ppm. Low incidences (

Toluene, a widely used aromatic organic solvent, has been well characterized as a neurotoxic chemical. Although the neurobehavioral effects of toluene have been studied substantially, the mechanisms involved are not clearly understood. Hippocampus, which is one of the limbic areas of brain associated with neuronal plasticity, and learning and memory functions, may be a principal target of toluene. In the present study, to establish a mouse model for investigating the effects of acute toluene exposure on the amino acid neurotransmitter levels in the hippocampus, in vivo microdialysis study was performed in freely moving mice after a single intraperitoneal administration of toluene (150 and 300 mg/kg). Amino acid neurotransmitters in microdialysates were measured by a high performance liquid chromatography system. The extracellular levels of glutamate and taurine were rapidly and reversibly increased within 30 min after the toluene administration in a dose-dependent manner and returned to the basal level by 1h. Conversely, the extracellular level of glycine and GABA were stable, and no significant change was observed after the toluene administration. To further investigate the brain toluene level in the hippocampus of toluene-administered mice, we used a solid-phase microextraction (SPME) method and examined the time course changes of toluene in the hippocampus of living mice. The brain toluene level reached the peak at 30 min after injection and returned to the basal level after 2h. In the present study, we observed the relationship between brain toluene levels and amino acid neurotransmitter glutamate and taurine levels in the hippocampus. Therefore, we suggest that toluene may mediate its action through the glutamatergic and taurinergic neurotransmission in the hippocampus of freely moving mice.

Volatile organic compounds are the main substances causing multiple chemical sensitivity reactions in human. Our laboratory has previously showed that the exposure of low-level formaldehyde causes immunogenic and neurogenic inflammatory responses in mice. The aim of the present study was to investigate the effect of long-term, low-level toluene exposure on airway inflammatory responses in mice lung. We exposed female C3H mice to filtered air (0ppm) or 50ppm of toluene for 6h/day on 5days/week for 6 or 12 weeks in the whole body exposure chamber. One day following the last toluene exposure, we collected bronchoalveolar lavage fluid from each mouse and examined cellular infiltration and production of cytokines, chemokines, neurotrophins and substance P by using ELISA method. We found that the number of total cells and macrophages increased significantly in both 6 and 12-week-exposed mice. In addition, the production of interferon-gamma and substance P were decreased significantly and nerve growth factor was not affected in both 6 and 12-week-exposed mice. In contrast, neurotrophin-3 production in bronchoalveolar lavage fluid was significantly increased only in 12-week-exposed mice. Our findings suggest that long-term (12-week) exposure of mice to low-level toluene modulates airway inflammatory response via neurological signaling.

The relative sensitivity of rats and humans to volatile organic compounds (VOCs) such as toluene (TOL) and perchloroethylene (PERC) is unknown and adds to uncertainty in assessing risks for human exposures to VOCs. Recent studies have suggested that ion channels, including nicotinic acetylcholine receptors (nAChRs), are targets of TOL effects. However, studies comparing TOL effects on human and rat ligand-gated ion channels have not been conducted. To examine potential toxicodynamic differences between these species, the sensitivity of human and rat nAChRs to TOL was assessed. Since PERC has similar effects, in vivo, to TOL, effects of PERC on nAChR function were also examined. Two-electrode voltage-clamp techniques were utilized to measure acetylcholine-induced currents in neuronal nAChRs (alpha4beta2, alpha3beta2, and alpha7) expressed in Xenopus oocytes. PERC (0.065 mM) inhibited alpha7 nAChR currents by 60.1 +/- 4.0% (human, n = 7) and 40 +/- 3.5% (rat, n = 5), and inhibited alpha4beta2 nAChR currents by 42.0 +/- 5.2% (human, n = 6) and 52.2 +/- 5.5% (rat, n = 8). Likewise, alpha3beta2 nAChRs were significantly inhibited by 62.2 +/- 3.8% (human, n = 7) and 62.4 +/- 4.3% (rat, n = 8) in the presence of 0.065 mM PERC. TOL also inhibited both rat and human alpha7, alpha4beta2, and alpha3beta2 nAChRs. Statistical analysis indicated that although there was not a species (human vs. rat) difference with PERC (0.0015-0.065 mM) or TOL (0.03-0.9 mM) inhibition of alpha7, alpha4beta2, or alpha3beta2 nAChRs, all receptor types were more sensitive to PERC than TOL. These results demonstrate that human and rat nACh receptors represent a sensitive target for VOCs. This toxicodynamic information will help decrease the uncertainty associated with animal to human extrapolations in the risk assessment of VOCs.

The United States Environmental Protection Agency (USEPA) has pursued the estimation of risk of adverse health effects from exposure to chemical mixtures since the early 1980s. Methods used to calculate risk estimates of mixtures were often based on single chemical information that required assumptions of dose-addition or response-addition and did not consider possible changes in response due to interaction effects among chemicals. Full factorial designs for laboratory studies can produce interactions information, but these are expensive to perform and may not provide the information needed to evaluate specific environmentally relevant mixtures. In this research, groups of Japanese medaka (Oryzias latipes) embryos were exposed to binary mixtures of benzene and toluene as well as to each of these chemicals alone. Endpoint specific dose-response models were built for the hydrocarbon mixture under an assumption of dose-additivity, using the single chemical dose-response information on benzene and toluene. The endpoints included heart rate, heart rate progression, and lethality. Results included a synergistic response for heart rate at 72 h of development, and either additivity or antagonism for all other endpoints at 96 h of development. This work uses an established statistical method to evaluate the toxicity of an environmentally relevant mixture to ascertain whether interaction effects are occurring, thus providing additional information on toxicity.

After prolonged toluene-inhalation (for 20 days) at the common abuse density (1500 ppm for 4 h per day), the effect of toluene on spermatogenesis in rats was investigated. Body weight was significantly decreased in the toluene group (P < 0.05). However, the weights of the testis and epididymis were maintained. To confirm whether the toluene-inhalation influences testis and epididymis as a stress factor; anti-70kD heat-shock protein (HSP70) and c-fos gene product (c-Fos) were observed. To observe the change of the cell division and the proliferation in spermatogenesis, proliferating cell nuclear antigen (PCNA) were stained immunohistochemically, and apoptosis was also detected. There was no positive immunoreactivity for HSP70 or c-Fos. There was no significant difference in the PCNA-expression in both groups. It was considered that toluene-inhalation did not have a clear influence in the division of spermatogonium and spermatocytes. On in situ apoptosis detection, slightly enhanced signals were observed in the toluene-inhalation groups. This might have some influence on meiosis from spermatocyte to spermatid. However, in toluene-inhalation rats exposed to a common abuse density, it was considered that spermatogenesis was well maintained and not apparently damaged.

The effects of toluene on the sensitivity to seizures induced by aminophylline were investigated. Mice were pretreated with an ip injection of corn oil or toluene (100-500 mg/kg) followed by a timed intravenous infusion of aminophylline at various time intervals to assess the seizure thresholds and lethal doses. Toluene increased seizure susceptibility to aminophylline in a dose- and time-dependent manner. Toluene-induced enhancement of seizure susceptibility to aminophylline occurred as early as 30 min and persisted for at least 3 days after a single administration of toluene (500 mg/kg). Treatment of benzaldehyde, one of toluene's metabolites, also showed an increase in the susceptibility to aminophylline. The enhancing effect was also observed in caffeine-induced seizures 1 h, but not 1 day after toluene treatment. These results suggest that individuals with toluene exposure may increase the risk for convulsive and even lethal complications associated with the therapeutic use of aminophylline.

The main purpose of this study was to compare the effects of solvents from different chemical classes on anxiety and nociception. Independent groups of mice were exposed to air (control group), toluene (1000-4000 ppm), benzene (1000-4000 ppm), 1,1,1-trichloroethane (TCE, 2000-12000 ppm), diethyl ether (10,000-30,000) or flurothyl (200-600 ppm). After a 30-min exposure, animals were tested either in the anxiety paradigm conditioned defensive burying (CDB) test or in the hot plate test. All solvents but flurothyl produced anxiolytic-like actions being the order of potency toluene > benzene > TCE > diethyl ether. When tested in the hot plate paradigm, toluene and TCE increased nociception, benzene and diethyl ether had no effects, and flurothyl decreased nociception Additional groups of mice were conditioned to recognize the aversive stimulus (electrified prod) prior to toluene exposure and then tested in the CDB test. In unconditioned animals, toluene increased the number of shocks that mice received; however, when mice had previous experience in the CDB test, toluene lacked this effect. Taken together, these results show that inhalants have different effects with different potencies both in the CDB and in the hot plate tests. Additionally, data suggest that acute administration of toluene could impair learning.

The effect of toluene inhalation on oxidative damage in rat organs was examined. Male Wistar rats was inhaled toluene (1500 ppm for 4 h a day) for 7 days. Quantitatively and immunohistochemically, oxidative DNA damage, lipid peroxide (LPO) and superoxide dismutase (SOD) were examined. As a marker of the oxidative DNA damage, 8-hydroxy-2'-deoxyguanosine (8-OH-dG) immunoreactivity increased in the lung, liver and kidney. The amount of 8-OH-dG also increased in liver and kidney significantly. In the testis, the amount of 8-H-dG did not increase, however 8-OH-dG immunoreactivity enhanced in the spermatogonia. SOD immunoreactivity increased in the lung, liver and kidney. However, 4-hydroxy-nonenal immunoreactivity and the amount of LPO did not change in each organ. Thus, oxidative damage by toluene is mainly DNA damage, especially, the oxidative DNA damage observed in the lung, liver and kidney for the increase of the immunoreactivity and amount of 8-OH-dG.

Toluene is the most widely used industrial solvent. It has been shown to be ototoxic in mice and rats, and to increase permanent threshold shift in conjunction with exposure to noise. Chinchillas are widely used for studying noise effects on the cochlea. The present study was initiated to study toluene and noise interaction in chinchillas. Thirty-three chinchillas were exposed to a 95 dBA 500 Hz octave band noise plus 2000 ppm toluene, 8 or 12 h per day for 10 days. Auditory function was estimated using the auditory brainstem response (ABR) to tones between 500 Hz and 16 kHz. There was no effect on the ABR of toluene alone. Noise alone produced a threshold shift. There was no interaction of noise and toluene on the ear. The present study suggests that chinchillas are markedly less susceptible to the ototoxic effect of toluene than mice and rats. A working hypothesis as to the species differences was that chinchilla liver was able to detoxify the toluene. Hepatic microsomes from chinchillas, rats and humans were tested for their ability to convert toluene to the more water-soluble compound - benzyl alcohol. Chinchilla livers were found to contain more of the P450 enzymes CYP2E1 and CYP2B than rats or humans. In addition, the data show that the P450 enzymes are more active in chinchillas than in rats and humans. In conclusion, the results suggest that rats and mice are a more appropriate model for human toluene ototoxicity. However, chinchillas may provide a valuable model for investigating how ototoxic agents can be detoxified to less damaging compounds.

The organic solvent toluene is widely used in industry. The threshold limit value for extended occupational exposure to toluene is presently set to 200 ppm in the United States. We have investigated the effect of an inhalation exposure of 80 ppm for 4 weeks (6 h/day, 5 days/week), followed by a postexposure period of at least 4 weeks, on behavior and brain features in the rat. Toluene exposure appeared to affect spatial memory, since toluene-exposed rats showed a longer time in the correct quadrant in a Morris swim maze. This effect may indicate that the exposed rats used their praxis strategy longer before they started to look for the platform elsewhere. Toluene-exposed rats showed trends for increases in both locomotion and rearing behaviors and a significantly reduced beam-walk performance. The area of the cerebral cortex, especially the parietal cortex, was decreased by 6-10% in toluene-exposed rats, as shown by magnetic resonance imaging of living rats and autoradiograms of frozen brain sections. The K(D) and B(max) values of the dopamine D(3) agonist [(3)H]PD 128907 were not affected by toluene, as measured in caudate-putamen and subcortical limbic area using biochemical receptor binding assays and in caudate-putamen and islands of Calleja using quantitative receptor autoradiography. Hence, previously demonstrated persistent effects by toluene on the binding characteristics of radioligands binding to both D(2) and D(3) receptors seem to indicate a persistent effect of toluene selectively on dopamine D(2) receptors. Taken together, the present results indicate that exposure to low concentrations of toluene leads to persistent effects on cognitive, neurological, and brain-structural properties in the rat.

Toluene (methylbenzene) is a common environmental pollutant that is found in many hazardous waste sites and it is an aquifer contaminant. A concern is the potential risk to human and ecosystem health due to exposure to toluene and its major biotransformation products. The cytotoxicity of eight aromatic products of toluene aerobic biotransformation was investigated in bluegill sunfish BF-2 cells. The cytotoxicity was determined using several in vitro assay endpoints. BF-2 cells were propagated at 32 degrees C in an atmosphere of 5% CO2-95% air. The concentrations of these products causing 50% inhibition in cell replication, protein content, uptake of natural red, and colony formation were evaluated and compared. The results of the study indicate a direct relationship between the exposure concentration of these products and observed cytotoxic effects. In descending order of cytotoxicity, the compounds were 3-methylcatechol, 4-methylcatechol, catechol, o-cresol, p-cresol, m-cresol, benzaldehyde, and methyl benzoate.

Toluene and styrene are industrial solvents that can severely damage the auditory function in adult rats. In the present study, toluene (1000 to 2000 ppm) and styrene doses (500 to 1500 ppm) were investigated according to the same schedule: 6 hours per day, 5 days per week, for 4 consecutive weeks. The auditory function of the animals was tested by recording evoked potentials from the inferior colliculus over a frequency range from 2 to 32 kHz, whereas pathological data were evaluated by conventional histologic techniques. The permanent threshold shifts (PTS) were obtained with a styrene dose 2.4 times lower than that of the toluene. The slope of the regression line (PTS/doses) was 2.1 steeper with styrene than that obtained with toluene in the same experimental conditions. The sequence of histopathological events along the organ of Corti, especially the orderliness and the location of the traumas, was similar for paired concentrations of styrene and toluene, which were respectively 650 ppm, 1500 ppm for the first match, and 850 ppm, 1750 ppm for the second one. Both electrophysiological and histological findings point out the higher ototoxic potency of the styrene compared to that of the toluene. Assumptions concerning the ototoxic mechanism are addressed in the present paper.

To identify the frequency range most sensitive to toluene-induced auditory damage, the auditory function of adult Long-Evans rats exposed to 1750 ppm of toluene (6 h/day, 5 days/week, 4 weeks), was tested by recording auditory-evoked potentials directly from the round window of the cochlea. The present electrocochleographic findings do not support a specific mid- to high-frequency loss of auditory sensitivity. On the contrary, the electrophysiologic data, obtained for audiometric frequencies ranging from 2 to 32 kHz, showed a hearing deficit not only in the mid-frequency region (12-16 kHz), but also in the mid-low-frequency region (3-4 kHz). Actually, the effect of toluene was independent of the frequency in our experimental conditions. Histological analysis was consistent with electrophysiologic data because a broad loss of outer hair cells occurred in both mid- and mid-apical coil of the organ of Corti.

The response of the daphnid Ceriodaphnia dubia to six widely used industrial chemicals acting through nonpolar narcosis and a mixture was determined. Toxicological effect levels were based on reasonably steady-state, measured concentrations. Reproductive IC50S were 149 microM benzene, 82 microM trichloroethylene, 35 microM toluene, 31 microM ethylbenzene, 26 microM m-xylene, and 4 microM tetrachloroethylene. A QSAR describing 2-day LC50S as a function of log Kow accounted for 90.97% of the variation in response across chemical. A similar QSAR for chronic effects on reproduction accounted for 78.92%. Mixtures of benzene, trichloroethylene, and toluene had effects at concentrations below their individual LOELs. Observed effects of 20/24 mixtures tested fell within the 95% prediction interval for a concentration-addition model of joint action derived from tests with individual components. However, the observed response differed significantly from the predictive relationship. In general, the predictive relationship overestimated mixture toxicity. Fitted relationships reduced observed error by as much as 82% compared to the predictive model.

Chronic benzaldehyde exposure is known to cause central nervous system (CNS) disturbances. Previous studies have shown that benzaldehyde causes the formation of reactive oxygen species (ROS) in rat synaptosomal fractions. Benzaldehyde has also been implicated in ROS formation in the CNS of rats treated with toluene. We have found that benzaldehyde effectively inactivates the antioxidant enzyme glutathione peroxidase (Ki approximately 15 microM), but has no effect on the other antioxidant enzymes tested: catalase, superoxide dismutase, and glutathione reductase. This effect has been found to be specific to benzaldehyde since other structurally related and unrelated aldehydes tested were found to be devoid of inactivating capacity toward glutathione peroxidase. Since glutathione peroxidase is the main enzyme responsible for removal of hydrogen peroxide and organic hydroperoxides in brain, its inactivation by benzaldehyde may be a main contributor to the observed ROS formation and the observed neurotoxicity caused by either benzaldehyde or toluene exposure.

Exposure to toluene (40-320 ppm; 4 weeks, 6 h/day, 5 days/week), followed by a postexposure period of 29-40 days, decreased the wet weight of the caudate-putamen and of the subcortical limbic area (maximal effect of 10% attained at 80 ppm toluene) of the male rat. Furthermore, toluene exposure decreased the IC50 values (significant effects attained at 80 ppm), the KH, the KL, and the RH% values of dopamine on [3H]raclopride-binding in the caudate-putamen. Toluene exposure did not significantly affect either the body weights, the wet weights of the whole brain, the serum prolactin levels, the KD or the Bmax values of [3H]raclopride-binding in the caudate-putamen and the subcortical limbic area, or the IC50 values of dopamine at [3H]raclopride-binding sites in the subcortical limbic area. Exposure to xylene or styrene (80 and 40 ppm, respectively; 4 weeks, 6 h/day, 5 days/week), followed by a postexposure period of 26-32 days, had no effect on the parameters described above (prolactin levels were not analyzed). The present study indicates that long-term exposure to low concentrations of toluene (> or = 80 ppm), but not xylene (80 ppm) or styrene (40 ppm), leads to persistent increases in the affinity of dopamine D2 agonist binding in the rat caudate-putamen.

Effects of chronic exposure to n-hexane and toluene on some nerve-specific marker proteins in rat central nervous system (CNS) and peripheral nervous system (PNS) were assessed and compared. The rats were exposed to 2000 ppm n-hexane, 12 hr/day, 6 days/week, for 24 weeks, and to 1000 ppm toluene, 8 hr/day, 6 days/week, for 16 weeks. The level of neuron-specific enolase (NSE), creatine kinase-B (CK-B), and beta-S100 protein in cortex, cerebellum, spinal cord, and proximal and distal sciatic nerve was determined by enzyme immunoassay method. In n-hexane-exposed rats, the level of NSE, CK-B, and beta-S100 decreased significantly in the distal segment of the sciatic nerve, while the marker proteins in CNS and proximal sciatic nerve remained unchanged. In contrast, chronic exposure to toluene mostly affected these marker proteins in CNS tissues, displaying the increase of NSE, CK-B, beta-S100 in cerebellum, as well as the increase of beta-S100 in spinal cord. No quantitative changes of the three proteins in distal sciatic nerve were observed after exposure to toluene. n-Hexane-induced peripheral distal neuropathy and toluene-induced brain gliosis appeared to be responsible for this different pattern of biochemical changes. The present study suggests the usefulness of using these nerve-specific marker proteins to assess the solvent-related CNS and PNS neurotoxicity.

The effects of subchronic inhalation exposure to toluene (80 ppm, for 4 weeks, 5 days/week, 6 h/day) was studied on spatial learning (postexposure days 3-6) and memory (postexposure day 14) using a water maze, on spontaneous and apomorphine-induced (1 mg/kg, subcutaneously (s.c.)) locomotor activity (postexposure day 17) and on the binding parameters of the dopamine D2 agonist S(-)[N-propyl-3H(N)]propylnorapomorphine ([H]NPA) in membrane preparations of the neostriatum of the rat. Toluene treatment was found to cause a statistically significant impairment in acquisition and retention of the spatial learning task. Furthermore, toluene significantly increased (2-fold) apomorphine-induced locomotion and caused a trend for a 50-60% increase in motility without any significant effect on rearing. Spontaneous locomotion, motility and rearing were not affected by toluene. Toluene treatment produced a significant 30-40% increase in the Bmax values of [3H]NPA and a trend for a 20-30% increase in the KD values. These results indicate that subchronic exposure to toluene in low concentrations causes a slight but persistent deficit in spatial learning and memory, a persistent increase in dopamine-mediated locomotor activity and an increase in the number of dopamine D2 receptors in the rat.

Effects of toluene on the electroencephalogram (EEG) and its power spectra were measured during a 2-hr exposure in a dynamic inhalational chamber in young rats (30-53 days old) and compared to those in adult rats (63-77 days old). Rats were exposed to one of the three concentrations [low (108-111 ppm), medium (160-163 ppm), and high (407-432 ppm)] of toluene on different days. In tests on sleep-wake cycle, in the young animals the duration of the wake stage (W) was increased with decreases of rapid eye movement (REM) and non-REM (NREM) sleep during hr 1 and hr 2 of exposure to the low concentration. These effects were marked at the medium and the high concentrations. In adult rats, at the low concentration the increase of W and the decrease of REM were observed only at hr 1; however, at medium and high concentrations these changes of W and REM sleep were marked along with a decrease of NREM. Comparison of the changes of duration of different states in rats of two age groups showed that there was a significant difference in the increase of W and the decrease of NREM sleep in young rats at hr 2 of exposure to low concentrations only compared to those in adult rats. Tested on power spectrum in young rats during REM sleep recorded from the visual cortex, the power of delta waves increased at the medium and high concentrations and that of theta wave decreased at the high concentration during hr 2 of exposure compared to the controls.(ABSTRACT TRUNCATED AT 250 WORDS)

An efficient method for the unbiased estimation of the total number of neurons in rat brain cortex is presented. The method is reasonable fast, the counting procedure takes 2-3 h per rat, and gives an estimate of the total neuron number in cortex cerebri with an CE of 0.10. The rat cerebral cortex is found to have a mean volume of 253 mm3 and to contain a mean of 21 million neurons. The method has been used in a neurotoxicologic study, in which rats were given toluene perorally in doses of 200, 400 and 800 mg/kg/day, respectively, for 12 weeks, followed by an exposure-free period of 4 weeks. The total number of neurons in rat brain cortex cerebri showed no significant difference between exposed and non-exposed animals. The applicability of the method is discussed.

Motor incoordination, euphoria and hallucinations are symptoms reported for humans voluntarily intoxicated by industrial solvents. An epileptic-like consciousness impairment has also been noted. The present paper describes a technique used for the experimental study of solvent intoxication in which toluene and benzene can be applied directly into the trachea of freely moving cats with chronically implanted electrodes. This technique permits the control of solvent dose and time of exposure. Results showed a 3 Hz spike-wave activity in the gyrus cinguli recording with both toluene or benzene intoxication. Furthermore, benzene inhalation produced generalized tonic-clonic seizures. These effects were dose-related. However, a sensitization period was essential for the development of such alterations, and effects showed a tendency to shortening through chronic exposures. These alterations were correlated with behavioral disturbances such as nodding, twitching and apparent hallucinations. Results are discussed regarding the sensitization period, the optimal peak of effects, and the period of tolerance development relevant to an earlier found amygdalar activation that could be correlated with other methods inducing experimental seizures, such as repetitive stimulation of the brain (kindling).

Toluene and 5 aliphatic chlorinated hydrocarbons of wide industrial use were injected into the air space of fertilized chicken eggs at 2, 3 and 6 days of incubation. The embryotoxicity was evaluated as survival and death incidences after 14 days of incubation, and also the weights and lengths of the embryos were recorded. The approximate LD50 value for trichloroethylene and trichloroethanes varied between 50 and 100 mumol/egg while for toluene, tetrachloroethylene and methylene chloride it was over 100 mumol/egg. Macroscopic malformations of various kinds were produced with doses of 5-100 mumol/egg. The teratogenic potential of the tested compounds decreased in the following order: 1,1,1-trichloroethane greater than trichloroethylene greater than methylene chloride, tetrachloroethylene, 1,1,2-trichloroethane greater than toluene greater than olive oil control.

The subchronic oral toxicity of 4-chloro-alpha, alpha, alpha-trifluorotoluene (CTT) was assessed in Sprague-Dawley rats. Four groups of six male and six female rats were treated daily for 28 days, by gavage, with doses of 0, 10, 100 and 1000 mg CTT/kg body weight using olive oil as a vehicle. No clinical signs were observed, other than salivation in the high-dose group in the last week. The males of this group showed a significant decrease in body-weight gain without a concurrent decrease in food consumption. In males, there were significant dose-dependent increases in blood cholesterol and triglycerides, suggestive of alterations in lipid metabolism. The females showed only a small dose-related increase in serum lactate dehydrogenase. Specific histological alterations were found in the males given 1000 mg/kg/day, namely hyaline droplet nephrosis, along with a significant increase in relative kidney weight, and an increase in lipid vacuoles in the adrenal cortex. Slight nephrosis was also observed in males given 100 mg/kg. Both male and female rats showed a significant increase in relative liver weight at a dose of 1000 mg CTT/kg. CTT appears to have a low subchronic oral toxicity. Neither pathological nor biochemical alterations were found at 10 mg/kg body weight/day and this can be defined as the no-observable-effect level (NOEL).

The intraperitoneal administration of benzene produced marked increases in mouse striatal concentrations of beta-phenylethylamine, p-tyramine and, to a lesser extent, m-tyramine. Similar increases were observed in rat striatal p- and m-tyramine. The subcutaneous administration of benzene dissolved in sesame oil increased mouse striatal p-tyramine but did not change m-tyramine. Benzene administration to mice pretreated with p-tyrosine produced marked increases in mouse striatal p-tyramine as well as in m-tyramine. The statistical analysis of the results indicated that the treatment produced an interaction that led to an increase in the concentration of both the p- and m-isomers of tyramine. The administration of benzene to m-tyrosine-pretreated mice increased striatal m-tyramine but p-tyramine was not increased. The treatment produced no potentiation in the formation of p- or m-tyramine. Of the other organic solvents given, pyridine produced the most marked effects. Its administration increased the concentration of both p- and m-tyramine in the mouse striatum. Treatment with toluene, chloroform, carbon tetrachloride or isoamylalcohol produced moderate increases in mouse striatal p-tyramine while toluene, dichloromethane or isobutylalcohol also increased m-tyramine. These increases in brain beta-phenylethylamine, p-tyramine and m-tyramine may play a contributory role in the human toxicity of benzene and some of these organic solvents; these toxic effects could be exacerbated after ingestion of foodstuffs containing the aminoacids phenylalanine or p-tyrosine or for those under treatment with a monoamine oxidase inhibitor.

The pharmacologic and pharmacodynamic properties of inhaled toluene and acetone were evaluated under exposure conditions typical of solvent abuse episodes. Male mice and rats were exposed for varying periods of time to vapor levels ranging from 2,600 to 12,000 ppm toluene and 12,600 to 50,600 ppm acetone. A battery of simple tests of unconditioned performance and reflexes was used as a measure of CNS depression, or narcosis. The animals were tested at intervals during and after solvent exposures to evaluate induction of and recovery from CNS depression. Toluene was a more potent and rapidly acting narcotic than acetone, though toluene had a very short duration of action. Animals which inhaled 12,000 ppm toluene for 5 min exhibited marked depression, but recovered fully after breathing fresh air for 10 min. Animals inhaling a comparable vapor level of acetone took 9 hr to recover. Concentrations of toluene were monitored in the blood, liver, and brain during and after inhalation sessions. Although the highest degree of correlation was consistently seen between the extent of CNS depression and brain toluene concentrations, blood levels were also a reliable index of the depth of narcosis. Measurement of the concentration of toluene vapor in sc air blebs proved to be a potentially valuable, noninvasive technique for estimating body burdens of the chemical during ongoing exposures.

Male Sprague-Dawley rats were injected ip with benzene, toluene, or a mixture of xylene isomers at 20 mmol hydrocarbon/kg daily for 3 days. The effects of administration of these hydrocarbons upon their own in vitro metabolism, as well as upon cytochrome P-450, NADPH-cytochrome c reductase, aminopyrine N-demethylase, aniline hydroxylase, glutathione, glutathione S-transferase, and UDPglucuronyltransferase in liver were studied. Each hydrocarbon studied increased its own in vitro metabolism. Benzene had no effect on the metabolism of toluene or xylenes. Toluene and xylenes increased the metabolism of benzene, toluene, and xylenes. Cytochrome P-450 was elevated by toluene and xylenes, but was not affected by benzene. NADPH-cytochrome c reductase was induced by all three hydrocarbons. Aminopyrine N-demethylase and aniline hydroxylase were induced by toluene and xylenes and were not affected by benzene. Glutathione was elevated by benzene, decreased by xylenes, and not affected by toluene. Glutathione S-transferase was induced differentially by these hydrocarbons toward various substrates: toward 1-chloro-2,4-dinitrobenzene by benzene and toluene, toward 1,2-dichloro-4-nitrobenzene by benzene and xylenes, and no effect toward 1,2-epoxy-3-(p-nitrophenoxy)propane by any hydrocarbons. UDPglucuronyltransferase was induced by benzene and toluene when o-aminophenol and phenol were used as the substrate. Xylenes had no effect. Benzene was more effective at inducing conjugation enzymes. Xylenes were more effective at inducing cytochrome P-450 dependent enzymes. Toluene was equipotent at inducing both types of enzymes. The results indicate that the addition of methyl groups to the aromatic ring affects the inductive pattern of these monocyclic aromatic hydrocarbons.

The potential hazards of exposure to vapor-phase toluene on pulmonary host defenses were evaluated. Mice exposed to concentrations ranging from 2.5-500 ppm, including the threshold limit value level of 100 ppm, exhibited increased susceptibility to respiratory infection with Streptococcus zooepidemicus. The no-measurable-effect level for single, as well as for 5 exposures was 1 ppm. Significantly decreased pulmonary bactericidal activity was observed after single exposures to 500, 250, 100 and 2.5 ppm toluene, and after 5 daily 3-h exposures to 1.0 ppm of toluene. A 20-exposure study with toluene at 1 ppm produced no changes in either of the 2 assays.

This study compares the effects in vivo of CH2Cl2, CH2Br2, CHCl3, CH2I2, CHBr3, CCl4, CHI3, CBr4, CI4, C2Cl6, C2HCl5, C6H6, C7H8, C6H5Br, ethionine, thioaeetamide and dimethylnitrosamine on the functions and composition of liver endoplasmic reticulum 2 hr after poisoning. Within the halomethane series, the effects on lipid diene conjugate content, oxidative demethylase, 14C-glycine incorporation into protein and glucose 6-phosphatase of liver microsomes and cell sap RNA content, increase with decreasing effective negative charge on the halogen atoms (ϵ), an indicator of increasing halomethane free radical reactivity (cf.B. P. Dailey, J. chem. Phys.33, 1641,1960). Peak toxic effect is reached following CCl4 and CHI3. Glycine incorporation into protein is also decreased 2 hr after thioacetamide and dimethylnitrosamine. After dimethylnitrosamine, suppression of protein synthesis is concomitant with increases in lipid diene conjugate content and cell sap RNA. C6H5Br and ethionine, both known hepatotoxins, do not effect microsomal composition and function at this time, nor do C6H6 or C7H8 both organic solvents with solubility properties similar to CCl4. The findings support the hypothesis that free radical halomethane metabolites injure the endoplasmic reticulum by reacting with and chemically altering its constituents. While dimethylnitrosamine may act similarly, thioaeetamide, bromobenzene and ethionine apparently do not.