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PubMed2006

Tentative criteria for assessing workers exposure to toluene by urinary toluene screening.

This study assessed screening thresholds for determining workers exposure to toluene (Tol) by urinary Tol (Tol-U) and proposed applicable criteria for on-site settings. Participants' urine samples (n = 21) were collected at the end of the workday during the latter half of a week and the Tol-U concentration was assayed. Simultaneously, each worker's exposure dose to Tol in the breathing zone during work, Tol-TWA (time-weighted average), was measured. Tentative criteria were proposed. Level I, less than Tol-U 38 microg/l, has the least chance of exceeding Tol-OEL 50 ppm (occupational exposure limit for Tol recommended by the Japan Society for Occupational Health), probability 95% <. Level II, Tol-U 38-60 microg/l, has a low possibility of exceeding Tol-OEL. Level III, Tol-U 60-110 microg/l, has a high possibility of exceeding Tol-OEL. Level IV, more than Tol-U 110 microg/l, clearly exceeds Tol-OEL, probability 95% <.

Humans↗
PubMed2005

Photoelectron spectroscopy of S1 toluene: II. Intramolecular dynamics of selected vibrational levels in S1 toluene studied by nanosecond and picosecond time-resolved photoelectron spectroscopies.

We present results which suggest that the photophysics of S(1) toluene is significantly more complicated than that of the related molecules p-fluorotoluene or p-difluorobenzene. We have measured a range of photoelectron spectra for a number of S(1) internal energies, on different time scales and at different temperatures, in an attempt to unravel the competing processes, but the final conclusion remains outstanding.

Journal Article↗
PubMed2003

Determination of unreacted 2,4-toluene diisocyanate (2,4TDI) and 2,6-toluene diisocyanate (2,6TDI) in foams at ultratrace level by using HPLC-CIS-MS-MS.

Isocyanates can cause occupational asthma. By using available HPLC-UVF methods, isocyanates can be quantified only at levels above 1% of the Permissible Exposure Limits (PEL). Once sensitized, workers can react to concentrations below these limits of detection (LOD) making these methods insufficiently sensitive to adequately evaluate trace amounts of isocyanates present in air or in materials at safe levels for sensitized workers. This article describes a novel method for isocyanate analysis allowing the quantification of 2,4TDI and 2,6TDI monomers at very low concentrations using HPLC-CIS-MS-MS. The method's sensitivity increases with a decrease in the alkali radius. The LOD is 0.039 ng mL(-1) for 2,4TDI and 0.100 ng mL(-1) for 2,6TDI in solution when lithium is the alkali adduct, which is 20 times more sensitive than HPLC-UVF method. This new method allows determination in foam at levels of 0.078 ng g(-1) for 2,4TDI and 0.200 ng g(-1) for 2,6TDI respectively, for a 0.5 g foam sample. This is more than 100 times more sensitive than other methods for determining free monomers in solid materials. Analytical reproducibility and precision are better than 92% and 93% for both diisocyanate monomers. The use of HPLC-UVF conventional method failed to detect unreacted isocyanates in foam samples, but TDI monomers were quantified by HPLC-CIS-MS-MS.

Air Pollutants, Occupational↗
PubMed1993

The ototoxic effect of toluene and the influence of noise, acetyl salicylic acid, or genotype. A study in rats and mice.

Toluene is a widely used organic solvent causing loss of auditory sensitivity in rats and presumably in humans. Also, the hearing loss in humans occupationally exposed to noise has been reported to be aggravated by simultaneous exposure to solvents. The aim of the present investigation was to study the effects of toluene, alone or in combination with other factors, on auditory sensitivity. The influence of acoustic trauma and of acetyl salicylic acid (ASA) on toluene induced auditory sensitivity loss in the rat, as well as the influence on age-related auditory sensitivity loss in two genotypes of mice were studied. An attempt was also made to identify cochlear structures damaged by toluene. Rats or mice were exposed to toluene by inhalation during 1 or 2 weeks. Rats were exposed to noise before or after the toluene exposure, or exposed to ASA by gavage simultaneously with toluene. The effect on auditory sensitivity was measured by frequency specific auditory brainstem response (ABR) between 1.6 and 20 kHz. In the investigations concerning the site of the toluene induced impairment, distortion product otoacoustic emissions (DPOEs) and morphological techniques were used. A permanent loss of auditory sensitivity, as measured by ABR, with the maximal threshold shifts between 6.3 and 12.5 kHz, was found in rats after exposure to toluene. In addition, lowered amplitudes of the DPOEs were recorded, implying that the outer hair cells (OHCs) were affected by toluene. A morphological study confirmed that toluene mainly affects the OHCs. A potentiated loss of auditory sensitivity was seen when toluene had preceded the noise exposure. When the exposure sequence was reversed, i.e. noise preceded toluene, an additive effect was observed. ASA, itself known to cause a reversible auditory impairment, was found to enhance the loss of auditory sensitivity caused by simultaneous toluene exposure. Finally, toluene exposure accelerated the age-related hearing loss in C57BL/6J mice. In conclusion, toluene causes a characteristic mid-frequency auditory damage. The OHCs are particularly susceptible to toluene exposure. The auditory sensitivity loss induced by toluene can be enhanced by ASA and by ensuing noise exposure. Also, toluene exposure can influence the rate of progress of age-related hereditary loss of auditory sensitivity.

Analysis of Variance↗
PubMed2001

Stable hydrogen and carbon isotope fractionation during microbial toluene degradation: mechanistic and environmental aspects.

Primary features of hydrogen and carbon isotope fractionation during toluene degradation were studied to evaluate if analysis of isotope signatures can be used as a tool to monitor biodegradation in contaminated aquifers. D/H hydrogen isotope fractionation during microbial degradation of toluene was measured by gas chromatography. Per-deuterated toluene-d(8) and nonlabeled toluene were supplied in equal amounts as growth substrates, and kinetic isotope fractionation was calculated from the shift of the molar ratios of toluene-d(8) and nondeuterated toluene. The D/H isotope fractionation varied slightly for sulfate-reducing strain TRM1 (slope of curve [b] = -1.219), Desulfobacterium cetonicum (b = -1.196), Thauera aromatica (b = -0.816), and Geobacter metallireducens (b = -1.004) and was greater for the aerobic bacterium Pseudomonas putida mt-2 (b = -2.667). The D/H isotope fractionation was 3 orders of magnitude greater than the (13)C/(12)C carbon isotope fractionation reported previously. Hydrogen isotope fractionation with nonlabeled toluene was 1.7 and 6 times less than isotope fractionation with per-deuterated toluene-d(8) and nonlabeled toluene for sulfate-reducing strain TRM1 (b = -0.728) and D. cetonicum (b = -0.198), respectively. Carbon and hydrogen isotope fractionation during toluene degradation by D. cetonicum remained constant over a growth temperature range of 15 to 37 degrees C but varied slightly during degradation by P. putida mt-2, which showed maximum hydrogen isotope fractionation at 20 degrees C (b = -4.086) and minimum fractionation at 35 degrees C (b = -2.138). D/H isotope fractionation was observed only if the deuterium label was located at the methyl group of the toluene molecule which is the site of the initial enzymatic attack on the substrate by the bacterial strains investigated in this study. Use of ring-labeled toluene-d(5) in combination with nondeuterated toluene did not lead to significant D/H isotope fractionation. The activity of the first enzyme in the anaerobic toluene degradation pathway, benzylsuccinate synthase, was measured in cell extracts of D. cetonicum with an initial activity of 3.63 mU (mg of protein)(-1). The D/H isotope fractionation (b = -1.580) was 30% greater than that in growth experiments with D. cetonicum. Mass spectroscopic analysis of the product benzylsuccinate showed that H atoms abstracted from the toluene molecules by the enzyme were retained in the same molecules after the product was released. Our findings revealed that the use of deuterium-labeled toluene was appropriate for studying basic features of D/H isotope fractionation. Similar D/H fractionation factors for toluene degradation by anaerobic bacteria, the lack of significant temperature dependence, and the strong fractionation suggest that analysis of D/H fractionation can be used as a sensitive tool to assess degradation activities. Identification of the first enzyme reaction in the pathway as the major fractionating step provides a basis for linking observed isotope fractionation to biochemical reactions.

Anaerobiosis↗
PubMedDate not supplied

Effects of toluene inhalation on detection of auditory signals in rats.

Inhalation of organic solvents can affect vigilance and reaction time in humans. An animal model of vigilance was designed to assess the effects of toluene on these processes. Adult male Long-Evans rats were trained to detect auditory signals (20-msec increases in the intensity of white noise). Two to 4 s after each signal (or blank period), two retractable levers were inserted into the test chamber. A press on one lever after a signal and on the other lever after a blank resulted in the delivery of food. Signal detection analysis showed that sensitivity (Sensitivity Index, SI) and response bias (Responsivity Index, RI) increased with signal intensity, indicating that loud signals were more detectable than soft signals and that the animals' criterion for responding "signal" increased with signal intensity. Response latency for correct choices was faster for signal trials than for blank trials. Toluene vapor was added to the airstream of these chambers at concentrations of 0, 1000, 1500, or 2000 ppm, either 10 or 30 min before testing and for the duration of each 1-h test. In air, SI increased across the duration of the test; this within-session improvement was reversed by toluene. RI did not change in air; it was decreased by toluene at the beginning of each exposure session, returned to the control level during exposure to 1000 and 1500 ppm toluene and exceeded air control after 40 min exposure to 2000 ppm toluene. Latency increased monotonically across toluene concentrations and time on test. Neither signal intensity nor the duration of toluene exposure before testing altered these effects of toluene. SI, RI, and latency baselines were recovered after toluene exposure indicating that no persistent effects of toluene were detectable. This conclusion was supported by data from other rats showing that toluene exposure (2000 ppm for 2 h/day for 4 consecutive days) did not affect auditory thresholds, as determined by reflex modification of an acoustic startle response using a 16 kHz tone as a prepulse stimulus, 7 or 17 days after exposure to toluene. Finally, rats tested immediately or 20 min after exposure to 0, 1000, 1500, or 2000 ppm toluene were not affected by the vapor, indicating that the impairment observed during toluene inhalation did not persist beyond the period of exposure.

Administration, Inhalation↗
PubMed1991

Biological monitoring for occupational exposure to toluene.

A study was undertaken to examine the relationship between exposure of workers to toluene in the work environment and biological indicators of toluene exposure. The biological indicators studied were toluene in expired air, toluene in blood obtained by the finger prick method, and urinary hippuric acid. The study was undertaken in a factory in Singapore that manufactures speakers for audio systems. A total of 86 female workers exposed to toluene at the workplace and a control group of workers not exposed to toluene were examined. All of them were teetotalers, were nonsmokers, and gave no history of chronic drug usage. The 8-hr time-weighted average exposure level of toluene ranged from 1.6 ppm to 263 ppm. The study showed the expected toluene levels in finger prick blood was 1.4 micrograms/mL after an 8-hr exposure to 100 ppm of toluene. Toluene concentration in expired air of 16 ppm after an 8-hr exposure to 100 ppm compared favorably with other studies. The toluene in blood/expired air ratio was observed to be lower than in other studies. In this study, the expected urinary hippuric acid level for a 100-ppm exposure to toluene was 2.7 g/g creatinine. This level is higher than that recorded in other studies. The results showed that at low levels of toluene, urinary hippuric acid is not a valuable indicator of exposure. Toluene in expired air is the most reliable biological indicator of exposure to toluene.

Air Pollutants, Occupational↗
PubMed1986

Toluene concentrations in the blood and alveolar air of workers during the workshift and the morning after.

Occupational toluene exposure was studied during the workshift and the morning after by the analysis of environmental air, alveolar air, and blood. Environmental toluene exposure was measured by both continuous and instantaneous sampling. Instantaneous environmental toluene concentrations correlated better with alveolar toluene concentrations (r = 0.94; n = 155) than with blood toluene concentrations (r = 0.71; n = 52). Continuous environmental toluene concentrations correlated better with blood toluene concentrations (r = 0.84; n = 65) than with alveolar toluene concentrations (r = 0.52; n = 46). During the workshift and the morning after, blood and alveolar toluene concentrations correlated significantly with each other (r = 0.75; n = 66 and r = 0.67; n = 52). In a group of workers who were exposed to a mean environmental toluene concentration of 146 micromilligrams the concentrations of toluene in the alveolar air and blood the morning after were 3.2 micromilligrams (SD = 1.7) and 27.5 micromilligrams (SD = 12.7) respectively. With regard to the morning after toluene determinations, blood concentrations correlated (r = 0.52; n = 52; p less than 0.001) better than the alveolar concentrations with the corresponding afternoon values (r = 0.36; n = 52; p less than 0.01). The decline of the toluene concentrations from the end of one workshift to the start of the next exposure indicated a mean toluene half life of 3.8 hours in the alveolar air and of 4.5 hours in blood and therefore the 17 hour interval between two consecutive workshifts was insufficient for the complete elimination of absorbed toluene.

Air Pollutants, Occupational↗
PubMed1997

Phenol- and toluene-degrading microbial populations from an aquifer in which successful trichloroethene cometabolism occurred.

We characterized the bacterial populations that grew in a Moffett Field, Calif., aquifer following three sequential field tests of phenol- or toluene-driven cometabolism of trichloroethene (TCE). Reducing the toluene and phenol concentrations in most-probable-number (MPN) tubes from 50 to 5 ppm increased the population density measured for these degraders by 1.5 and 1 log units, respectively, suggesting that natural populations might be quite sensitive to these substrates. Phenol and toluene degraders were isolated from the terminal MPN dilution tubes; 63 genetically distinct strains were identified among the 273 phenol- and toluene-degrading isolates obtained. TCE was cometabolized by 60% of the genetically distinct strains. Most strains (57%) grew on both phenol and toluene, and 78% of these strains hybridized to the toluene ortho-monooxygenase (TOM) probe. None of the strains hybridized to probes from the four other toluene oxygenase pathways. Gram-positive strains comprised 30% of the collection; all of these grew on phenol, and 47% of them also grew on toluene, but none hybridized to the TOM probe. Among the gram-negative strains, 86% of those that grew on both toluene and phenol hybridized to the TOM probe, while only 5% of those that were TOM-positive grew on toluene alone. A larger proportion of TCE degraders was found among gram-negative than gram-positive strains and among organisms that grew on phenol than those that grew on toluene. Hybridization of strains to the TOM probe was somewhat predictive of their TCE-cometabolizing ability, especially for strains isolated on toluene, but there was also a significant number (20%) of strains that hybridized to the TOM probe but were poor TCE cooxidizers. No Moffett Field isolates were as effective as Burkholderia cepacia G4 in cooxidizing TCE. Most of the aquifer strains ranged from moderately effective to ineffective in TCE cooxidation. Such populations, however, apparently accounted for the successful phenol- and toluene-stimulated TCE removal that occurred during the field assessment of this remediation process. This suggests that naturally occurring communities of only moderate TCE-cooxidizing ability may support successful TCE bioremediation as long as the phenol or toluene present is not limiting. This activity, however, may not be sustainable for the long term, because TCE-inactive populations that consumed toluene at rates equal to that of the best TCE degraders were present and hence would be expected to eventually dominate the community.

Journal Article↗