Continuous exposure to low-frequency noise and carbon disulfide: Combined effects on hearing.

Carbon disulfide (CS2) is used in industry; it has been shown to have neurotoxic effects, causing central and distal axonopathies.However, it is not considered cochleotoxic as it does not affect hair cells in the organ of Corti, and the only auditory effects reported in the literature were confined to the low-frequency region. No reports on the effects of combined exposure to low-frequency noise and CS2 have been published to date. This article focuses on the effects on rat hearing of combined exposure to noise with increasing concentrations of CS2 (0, 63,250, and 500ppm, 6h per day, 5 days per week, for 4 weeks). The noise used was a low-frequency noise ranging from 0.5 to 2kHz at an intensity of 106dB SPL. Auditory function was tested using distortion product oto-acoustic emissions, which mainly reflects the cochlear performances. Exposure to noise alone caused an auditory deficit in a frequency area ranging from 3.6 to 6 kHz. The damaged area was approximately one octave (6kHz) above the highest frequency of the exposure noise (2.8kHz); it was a little wider than expected based on the noise spectrum.Consequently, since maximum hearing sensitivity is located around 8kHz in rats, low-frequency noise exposure can affect the cochlear regions detecting mid-range frequencies. Co-exposure to CS2 (250-ppm and over) and noise increased the extent of the damaged frequency window since a significant auditory deficit was measured at 9.6kHz in these conditions.Moreover, the significance at 9.6kHz increased with the solvent concentrations. Histological data showed that neither hair cells nor ganglion cells were damaged by CS2. This discrepancy between functional and histological data is discussed. Like most aromatic solvents, carbon disulfide should be considered as a key parameter in hearing conservation régulations.

Volatile organic compounds in plasma for the diagnosis of esophageal adenocarcinoma: a pilot study.

BACKGROUND AND AIMS: A noninvasive screening test that can detect esophageal adenocarcinoma (EAC) at an earlier stage could improve the prognosis associated with EAC. The role of plasma volatile organic compounds (VOCs) for the diagnosis of EAC has not been previously studied. METHODS: Plasma samples were collected from subjects with EAC and GERD before endoscopy. Twenty-two preselected VOCs were analyzed with selected ion flow tube mass spectrometry. RESULTS: The headspaces from 39 plasma samples (20 EAC, 19 GERD) were analyzed. The levels of 9 VOCs (acetonitrile, acrylonitrile, carbon disulfide, isoprene, 1-heptene, 3-methylhexane, [E]-2-nonene, hydrogen sulfide, and triethylamine) were significantly altered in EAC patients compared with GERD patients. A multivariable logistic regression analysis was performed to build a model for the prediction of EAC. The model identified patients with EAC with an area under the curve of 0.83 (95% confidence interval, 0.67-0.98). CONCLUSIONS: Plasma VOCs may be useful in diagnosing EAC. Larger studies are needed to confirm our pilot study observations.

Indicators of cardiovascular risk among workers exposed to high intermittent levels of carbon disulphide.

The effects of exposure to carbon disulphide have been studied mostly among workers in the viscous rayon industry, where the usual exposure profile has been relatively steady exposure over work shifts. We investigated 13 workers in a small chemical company who were exposed to low levels, peaking intermittently to relatively high levels in the range of 100-200 ppm at the end of the work shift, a pattern that may change the risk profile. Our investigation was part of a compliance order that was fought by the company and our access and follow-up was limited. Two workers had burns on their bodies associated with exposure to caustic. Four had elevations in total serum cholesterol, one had elevated serum triglycerides and three had elevations in fasting blood glucose--two of them were known to be diabetics before employment and one had a history of unexplained peripheral neuropathy. No consistent pattern suggestive of a defined lipoprotein abnormality was obvious but several atherogenic profiles were observed. Five had abnormalities on electrocardiogram, four of whom appeared to be among the most heavily exposed. The presence of these changes taken together in this context may suggest accelerated atherosclerotic changes. Tests of liver and kidney function were within the normal range for all workers, as was a complete blood count. Four of the workers had evidence of a bilateral reduction in hearing threshold at 4,000 Hz. A complete set of recommendations was forwarded to the employer, emphasizing further control of exposure to carbon disulphide, personal protection requirements and a cardiovascular risk reduction programme. Conditions improved in the plant following modifications introduced in response to a stop work order from the provincial government's occupational health and safety agency. However, a fire in 1998 put the company out of business and ended further follow-up or interventions. We conclude that these findings, while difficult to interpret because of the circumstances of the investigation, are compatible with an atherogenic effect of exposure to peaking levels of carbon disulphide. The observation should be tested in a larger population with fewer confounding factors and greater control over the investigation.

Carbon disulfide neurotoxicity in rats: II. Toxicokinetics.

Carbon disulfide (CS2) is an important industrial chemical widely used in the production of rayon, cellophane, fungicides and biocides. The uptake and elimination kinetics of CS2 was characterized for a single i.v. dose and for a single inhalation exposure. The uptake of CS2 into the blood was rapid with half times of 6 to 9 minutes. Elimination was relatively quick with terminal elimination half times of 41 to 77 minutes. The plateau CS2 blood concentration was lower in females than in males and lower in the male 50 ppm treatment group than would be predicted by linear dose proportionality compared to the 500 ppm and 800 ppm treatments. The CS2 blood concentration for the female 50 ppm group was below the limit of detection. The total and central compartment apparent volumes of distribution, 4.2 l/kg and .9 l/kg, were estimated from a single 50 mg/kg i.v. dose. The concentration of CS2 in blood resulting from repeated exposure, was investigated in a 13 week inhalation study. Blood samples were taken in rats previously exposed to 0, 50, 500, and 800 ppm CS2 for 2, 4, 8, or 13 weeks. The concentration of CS2 in the blood of male rats remained relatively constant throughout study. However the female 500 and 800 ppm groups showed a marked decrease over the course of the 13 week study. The concentration of CS2 in the blood from the 500 and 800 ppm groups of both sexes at all time points was higher compared to the 50 ppm group, than would be predicted by linear dose proportionality. The concentration of 2-thiothiazolidine-4-carboxylic acid in urine collected from the same animals lacked dose proportionality between the treatment groups at all time points. CS2 exposure caused dose-related decreases in body weight gain in both male and female rats.

Immunomodulatory effects of occupational exposure to mancozeb.

The effects of occupational exposure to ethylene-bis-dithiocarbamate of manganese and zinc on the immune system were evaluated in a group of mancozeb-exposed manufacturers and controls. The immune system tests revealed the following: (a) lymphocyte proliferative responses triggered by different activators and mitogen-induced IL-2 production were higher in exposed subjects than in controls; (b) production of monocyte/macrophage-derived IL-1 and polyclonal IgG and IgM, by beta-lymphocytes, did not differ between exposed subjects and controls; (c) percentages and absolute numbers of total T-cells, T-helper cells, T-suppressor/cytotoxic cells, activated T-cells, total beta-cells, and natural killer cells were similar in exposed subjects and controls; (d) serum immunoglobulin classes and complement fractions were within the range of normality; and (e) rheumatoid factor and non-organ-specific serum autoantibodies were absent in exposed and control subjects. An increase in T-cell functional response was found in the exposed group, suggesting a slight immunomodulator effect of mancozeb in conditions of low-level, prolonged occupational exposure.

Blood and urine concentrations of chemical pollutants in the general population.

The concentration of 9 environmental chemical pollutants in the general population was measured in blood and urine. For the 9 different pollutants, the blood samples tested varied from 88 for acetone to 431 for benzene. Urine samples varied from 48 for styrene to 213 for n-hexane. Six of these agents (benzene, toluene, styrene, n-hexane, acetone and carbon disulphide) were present in all or almost all (100-94%) blood samples. The three chlorides (chloroform, trichloroethylene and tetrachloroethylene) were present only in 60-85% of samples. After acetone, with blood concentrations in microgram/1 (mean 840 microgram/l), the highest mean blood levels were those of toluene (1097 ng/l), chloroform (955 ng/l) and n-hexane (642 ng/l). Trichloroethylene and free carbon disulphide showed similar values (458 and 438 ng/l, respectively). Finally, benzene, styrene and tetrachloroethylene showed the lowest values (262, 217 and 149 ng/l, respectively). There was generally a significant difference between rural and urban workers in terms of blood benzene (200 ng/l vs 264 ng/l), trichloroethylene (180 ng/l vs 763 ng/l) and tetrachloroethylene (62 ng/l vs 263 ng/l). In a group of subjects potentially exposed to industrial solvents, classed as chemical workers, blood benzene, toluene, chloroform and n-hexane were significantly higher than in rural and urban workers. Smokers showed a significantly higher blood concentration than non-smokers for benzene (381 ng/l vs 205 ng/1), toluene (1431 ng/l vs 977 ng/l), and n-hexane (838 ng/l vs 532 ng/l). All or almost all urine samples (100-92%) contained all the compounds except trichloroethylene and tetrachloroethylene, present in 79% and 76% of samples, respectively (table 2). Urinary concentrations of all compounds did not differ significantly between rural and urban workers. Benzene and toluene were significantly higher in in urine of smokers than of non-smokers. Chloroform and n-hexane showed significantly higher urinary than blood values. Excluding acetone, with urinary and blood concentrations in pg/l, chloroform, toluene and n-hexane showed the highest mean concentrations both in blood and in urine.

Effects of disulfiram on serum dopamine-beta-hydroxylase and blood carbon disulphide concentrations in alcoholics.

The aim of this study was to investigate the effects of single and repeated disulfiram doses on serum dopamine-beta-hydroxylase activity and blood carbon disulphide concentrations in a group of abstinent alcoholics. The increase in the blood concentration of carbon disulphide was dose dependent after the oral administration of 100-400 mg of disulfiram. Free carbon disulphide peaked at 12 h while the protein-bound fraction increased at least up to 24 h. Both single (100-400 mg p.o.) and repeated (200 mg daily p.o. for ca. 1 month) administrations failed to inhibit the activity of serum dopamine-beta-hydroxylase. The repeated daily administration of 200 mg of disulfiram also had no influence on copper-activated serum dopamine-beta-hydroxylase, which was the same before and after 1-month treatment period. Contrary to the disulfiram group, the activity of the copper-activated enzyme in the serum of abstinent alcoholics declined significantly during the same 30 days.

Carbon disulfide in blood: a method for storing and analysing samples.

Concentrations of free and acid-labile carbon disulfide in human blood were determined by gas chromatography mass-spectrometry. Carbon disulfide was measured in the blood of 62 subjects not occupationally exposed to the solvent, and in 27 subjects treated with disulfiram (which is partially biotransformed into carbon disulfide). In blood, a small part of carbon disulfide is free (it can be analysed without any blood treatment); most carbon disulfide is bound ("acid labile" carbon disulfide), and requires acid hydrolysis to become free and detectable. During the first phase of our study, stored samples of blood (storage at 4 degrees C for 15-40 days) were used. Later, we analysed fresh blood samples. A significant decrease in carbon disulfide was found in stored samples in comparison to fresh samples. During storage, free and acid-labile carbon disulfide in blood decreased respectively to 26% and 27% of the initial concentration within a month. In fresh samples, free carbon disulfide concentrations in blood showed a median of 139 ng/l in normal subjects. Acid-labile carbon disulfide concentrations were much higher (median 2743 ng/l). Free and acid-labile carbon disulfide in blood were closely correlated (r = 0.9358). Blood samples stored at -80 degrees C maintained a constant concentration of carbon disulfide over almost three weeks.

Blood concentrations of carbon disulphide in dithiocarbamate exposure and in the general population.

Blood carbon disulphide (CS2), both free and total, was determined by gas chromatography-mass spectrometry in 112 "normal" subjects and in 20 subjects employed in a dithiocarbamate factory, comprising ten blue-collar workers involved in dithiocarbamate production and ten white-collar office staff. The ten production workers were examined over two workshifts, the first at the beginning of the week (Monday) and the second after an intervening period of at least 1 day. Three blood samples were taken for each shift studied, one prior to starting work, one at the end of the shift and the third 16 h after the end of the shift (on the following morning). The mean CS2 blood levels measured in the 112 normal subjects was 663 ng/l for the free fraction and 3178 ng/l for the total. In 16 blood samples taken from the ten dithiocarbamate factory office workers, the mean free and total CS2 blood levels were 846 and 4140 ng/l, respectively, i.e. not significantly different from those observed in the normal subjects. At the end of the first 8-h shift, the ten dithiocarbamate factory production workers had free and total CS2 values of 1070 and 8471 ng/l, respectively, which were significantly higher than those observed prior to starting work (240 and 4738 ng/l). All the total CS2 levels measured in the shop-floor workers, with the sole exception of the values recorded prior to the start of the Monday shift (4738 ng/l), ranged from 7047 to 8471 ng/l and were significantly higher than those measured in the white-collar staff (4140 ng/l).

Blood concentration of carbon disulphide in "normal" subjects and in alcoholic subjects treated with disulfiram.

Assay of free and acid labile carbon disulphide (free and total CS2 respectively) in human blood was performed by gas chromatography/spectrometry. The method used a large dynamic head space volume and a "cryogenic trap". Blood CS2 concentration was measured in 42 subjects not occupationally exposed to CS2 (group A) and in 11 alcoholic subjects (group B) treated with disulfiram. Free CS2 concentration showed a mean value of 261 ng/l in the 42 subjects in group A and 9482 ng/l in eight subjects of group B. Total CS2 concentration was 897 ng/l and 40,084 ng/l in groups A and B respectively. Differences between the groups were highly significant for concentrations of both free and total CS2. Total CS2 concentration was about four times as high as free CS2 concentration in both groups. A significant correlation was found between free and total CS2 concentration both in group A and in group B. In the alcoholic subjects (group B), blood concentrations of both free and total CS2 were related to time of sampling after treatment with disulfiram.

Carbon disulfide effects on the visual system. I. Visual thresholds and ophthalmoscopy.

The visual effects of carbon disulfide exposure were studied in macaque monkeys with measurements of visual thresholds, fluorescein angiography and fundus photography. Five monkeys were exposed by inhalation for 6 hr a day, 5 days a week to 256 ppm carbon disulfide (CS2). The motor dysfunction observed in these monkeys appeared to be entirely reversible. All five suffered severe reductions in visual acuity and contrast sensitivity although flicker resolution was not affected. Visual loss was found to be irreversible, with degeneration of substantial numbers of retinal ganglion cells (companion paper) in those monkeys permitted to survive after the termination of exposure. None of the monkeys developed retinal microaneurysms or hemorrhages, major accepted signs of visual toxicity in CS2 exposed humans; thus, permanent visual loss may result from carbon disulfide exposure even in the absence of retinal vascular effects.

Characterization of carbon disulfide binding in blood and to other biological substances.

Free and bound forms of CS2 are present in subjects exposed to CS2. In rats exposed to 2 mg/liter (approximately 640 ppm) of CS2 for 4 hr, concentrations of acid-labile CS2 (AL CS2, a form of bound CS2 that can be recovered from biological samples by acid treatment) in plasma and red blood cells (RBCs) increased linearly with exposure time. The majority (90%) of the blood AL CS2 was present in the RBCs. About 95% of the AL CS2 in plasma and in RBCs of exposed rats was found in the precipitates after treatment with ammonium sulfate. Incubation of fractionated human RBC lysates with CS2 showed that CS2 binding in these fractions was proportional to the hemoglobin concentration. These observations show that in blood, CS2 binds (in the form of AL CS2) mainly to hemoglobin and to a small extent to other blood proteins. Binding of CS2 to small molecules, including amino acids, accounted for only a small fraction of blood AL CS2. In in vitro studies, CS2 also bound to human albumin, gamma-globulin, and horse heart myoglobin. It was also found that CS2 binds to amino and sulfhydryl compounds at physiological pH. Plasma incubated with CS2 was found to chelate copper. Chelation of copper-containing enzyme by the reaction products of CS2 and biological amines has been observed and has been proposed as one of the mechanisms by which CS2 induces neurotoxicity (M.J. McKenna and V. DiStefano, 1977b, J. Pharmacol. Exp. Ther. 202, 253-266). Radioisotope studies showed that a substantial portion of the radioactivity could not be released from 14CS2-treated plasma and serum upon acid treatment at elevated temperature. These studies suggest the existence of non-acid-labile bound CS2, besides AL CS2, in plasma and serum treated with CS2.

The role of the red blood cell in the transport of carbon disulfide.

When rats were exposed to 2 mg l-1 (approximately 640 ppm) of carbon disulfide (CS2) for 4 h, the concentration of free CS2 in the red blood cells (RBCs) approached a plateau within 2 h. Free CS2 in plasma reached a steady state concentration within 15 min of exposure. More than 90% of the free CS2 in blood was found in the RBCs regardless of the length of exposure. In vitro studies showed that about 90% of the free CS2 partitioned into the RBCs regardless of whether the CS2 was added first to the plasma or directly to the RBCs. Hence, it appears that the RBC is the major carrier of CS2 in blood. It was found that 98% of the free CS2 in red blood cell lysates was associated with hemoglobin. Free CS2 in RBCs was readily partitioned into olive oil (RBCs/oil = 1/6), less readily into the plasma (RBCs/plasma = 12/1), and only to a small extent into phosphate buffer (RBCs/buffer = 39/1). The extraction of free CS2-loaded RBCs into albumin solution increased with increasing albumin concentrations. CS2 can be extracted with buffer, protein solution, and oil, indicating that CS2 in RBCs can be transferred to the medium in which the RBCs contact. It is proposed that RBCs may also play an important role in the transport of CS2 from lung to tissues and vice versa. The possible role of RBCs in the transport of other organic solvents in the blood is also discussed.

Elimination kinetics of disulfiram in alcoholics after single and repeated doses.

Elimination kinetics of disulfiram were determined in 15 male alcoholics after 250 mg disulfiram taken by mouth as a single dose and again after 12 days of dosing. Apparent t 1/2s were calculated for disulfiram, diethyldithiocarbamate (DDTC), diethyldithiocarbamate-methyl ester (DDTC-Me), diethylamine (DEA), and carbon disulfide (CS2) and were found to be 7.3, 15.5, 22.1, 13.9, and 8.9 hr. Elimination t 1/2 for CS2 in breath was 13.3 hr. Average time to reach maximal plasma concentration after either single or repeated doses was 8 to 10 hr for disulfiram, DDTC, DDTC-Me, DEA, and CS2 in breath, while plasma CS2 concentration peaked 5 to 6 hr after disulfiram. In these studies, 22.4% and 31.3% of the disulfiram after single and repeated dosing was eliminated in the breath during one dosing interval. In urine, 1.7% and 8.3% of the disulfiram dose was eliminated as DDTC-glucuronide after single and repeated dosing, while DEA accounted for 1.6% and 5.7% of the dose. There was marked intersubject variability in plasma levels of disulfiram and its metabolites. This variability may be the result of the lipid solubility of disulfiram, differences in plasma protein binding, or the effect of enterohepatic cycling.

Blood-bound carbon disulfide: an indicator of carbon disulfide exposure, and its accumulation in repeatedly exposed rats.

Carbon disulfide is present in exposed subjects in free and bound or acid-labile forms. Sensitivities of the blood acid-labile CS2 (AL CS2) concentration and the modified iodine-azide test (IAT) were compared as indicators of CS2 exposure. Rats were exposed to 15 (approximately 5 ppm), 30, 60, or 120 mg/m3 of CS2. Exposure to 15 or 30 mg/m3 of CS2 could not be detected by the modified IAT. However, a linear relationship between blood CS2 (free or AL CS2) concentrations and these exposure levels was observed. Free CS2 is eliminated rapidly, while AL CS2 is eliminated very slowly from the exposed subjects. Repetitive daily exposures (8 hr/day) to 120 mg/m3 of CS2 were carried out in rats. Blood AL CS2 concentrations in exposed rats increased with each successive exposure while the free CS2 level remained relatively constant. By the sixth or seventh daily exposure the blood AL CS2 concentration was about 2.5 times that of the first 8-hr exposure and about 3 times the level of free CS2. These results indicated an appreciable accumulation of CS2 in subjects repeatedly exposed to low concentrations of the solvent. Rats were also exposed to CS2 8 hr/day for 5 days. After a 2-day nonexposure period (Days 6 and 7), the animals were reexposed on Day 8. The blood AL CS2 concentration in animals exposed on Day 8 was substantially higher than in those that received a single 8-hr exposure (Day 1), despite the hiatus on Days 6 and 7. These results indicated that blood AL CS2 was not totally eliminated during the 2-day nonexposure period. In in vitro experiments, the binding profile of CS2 to human blood was remarkably similar to that of rats exposed to CS2 by inhalation.

[Modifications of disulfiram and its metabolites in blood in alcoholic hepatopathy (author's transl)]. / Modifications des taux sanguins du disulfiram et de ses métabolites dans l'insuffisance hépato-cellularie d'origine alcoolique.

In cirrhotic, steatosic and healthy subjects, the authors studied the metabolism of disulfiram (TETD) administrated orally (500 mg) 3 consecutive days. Carbon disulfide (CS2) and the whole TETD, diethyl dithiocarbamate (DDC) disulfides, were determined by a gas chromatographic method. The evolution of metabolites is similar in steatosic and healthy subjects. In cirrhotics the CS2, DDC and disulfides level increase within the 3 days. This phenomenon may be related with hepatic toxicity of TETD and with the persistence of disulfiram-alcohol reaction. The authors suggest to use low doses of disulfiram in cirrhotic.

Determination of disulfiram and metabolites from biological fluids by high-performance liquid chromatography.

A high-performance liquid chromatographic method is described for the determination of disulfiram, diethyldithiocarbamate, diethyldithiocarbamate methyl ester, carbon disulfide, and diethylamine from a single sample of plasma or urine. The analytical procedure is based on a quantitative stepwise extraction of disulfiram and diethyldithiocarbamate methyl ester, or the conversion of diethyldithiocarbamic acid, carbon disulfide and diethylamine to diethyldithiocarbamate methyl ester for chromatographical determination. The procedure is specific, precise and simple. The application of the analytical methods developed for the determination of disulfiram and the various metabolites in plasma from mice given disulfiram intraperitoneally or humans given Antabuse orally is illustrated.

Methods for detecting disulfiram in biologic fluids: application in studies of compliance and effect of divalent cations on bioavailability.

Studies regarding the efficacy of disulfiram in the treatment of alcoholism have not included a method of evaluating compliance to the prescribed regimen. This article outlines current methods used to detect disulfiram in blood, breath, and urine.