Rayon Factory Research Articles

Unexpected increases in rotifer resting egg abundances during the period of contamination of Lake Orta

<p>Despite their ecological importance and rapid response to environmental changes, rotifers are rarely included in palaeolimnological studies. Here, we describe changes in abundance (ABD) and morphotype (MTs) diversity of rotifer resting eggs in the sediments of deep subalpine Lake Orta, Italy, covering a period prior to (pre-) 1926, during long-term ammonia and metal pollution from a rayon factory, and subsequent recovery of water quality. Following the pollution and bacterial oxidation of the ammonia, Lake Orta became the largest and deepest acid lake in Europe. Recovery of water quality followed both a ban on the discharge of industrial wastes, and a liming intervention in 1989 and 1990. We sectioned a sediment core collected from the deepest part of the lake (ORTA 07/2A) to provide a high time resolution, given the ca. 3-4 y cm<sup>-1</sup> of sediment accumulation. Rotifer resting egg (RRE) abundance and morphotypes were examined from the sediments and compared to limnological variables indicating the pollution. Rotifer resting egg abundance significantly increased with lake contamination (r=0.609 and -0.624 for copper and pH, respectively; P<0.001; n=27). A lake-water copper concentration threshold of ca. 40 µg L<sup>-1</sup>discriminated among pre-, during-, and post- pollution compositions of the rotifer morphotype assemblages. Diversity and morphotype richness increased during the recovery from copper pollution and with complete restoration from acidity, while abundance increased during pollution. The persistence of presumably viable <em>Brachionus</em> resting eggs and of hatched egg cases during the heavy pollution phase suggests that, unlike most other organisms, which were extirpated by the pollution of the lake, rotifers survived producing resting eggs, which secured future generations.</p>

Long-term persistence of sedimentary copper contamination in Lake Orta: potential environmental risks 20 years after liming

<p>Lake Orta, northern Italy, has suffered from severe copper pollution and human-induced acidification between the 1920s and the 1990s because of discharges from a rayon factory and electroplating industries located in its water basin. Following liming operations in the late 1990s, the chemical quality of the water column has been restored and signs of, still ongoing, biological recovery observed. Examination of two sediment cores collected close to the main historical Cu discharge and in the central part of the Lake shows that Cu concentrations in the uppermost layers of bottom sediments remain 10 to 40-fold higher than background levels. Past studies demonstrated the toxic potential of Lake Orta sediments to a variety of organisms at Cu concentrations comparable to present ones. Comparison with published results suggests that current level of Cu contamination may still pose a risk to sediment-ingesting organisms and slow down further ecological recovery of Lake Orta. Particular attention should be given to understand the effects of dietary ingestion of Cu from sediments which, unlike in previous ecotoxicological studies, may now represent the main route of Cu exposure for sediment-ingesting benthic organisms.</p>

Metabolic syndrome in carbon disulfide-poisoned subjects in Korea: does chemical poisoning induce metabolic syndrome?

Mass carbon disulfide (CS(2)) poisoning was reported at a viscose rayon factory in Korea. We evaluated the association between CS(2) poisoning and the prevalence of metabolic syndrome. The cases (n = 170) involved CS(2)-poisoned subjects, who participated in a health examination conducted at a hospital in Korea in 2005. The controls (n = 170) were selected randomly from the participants in the third Korean National Health and Nutrition Examination Survey. Metabolic syndrome was defined as having at least three of following metabolic abnormalities: abdominal obesity, elevated triglyceride, reduced high-density lipoprotein cholesterol, elevated blood pressure, and elevated fasting glucose levels. After adjusting for covariates (age, gender, education, marital status, alcohol consumption, and smoking), CS(2)-poisoned subjects had an increased risk of metabolic syndrome (prevalence ratio 1.57, 95% CI 1.25-1.98). The findings suggest that CS(2) poisoning may increase the risk of metabolic syndrome.

Effect of polymorphic variations of glutathione- S-transferase genes on carbon disulfide metabolism in Bulgarian workers from rayon factory

Effect of polymorphic variations of glutathione- S-transferase genes on carbon disulfide metabolism in Bulgarian workers from rayon factory

Electrocardiographic features of Korean carbon disulfide poisoned subjects after discontinuation of exposure

Mass poisoning by carbon disulfide (CS(2)) was reported at a viscose rayon factory in Korea in the late 1980s; the factory was subsequently closed in 1993. In this study, we evaluated the late electrocardiographic features in the CS(2) poisoned subjects. The cases were composed of 198 retired workers with a history of CS(2) poisoning. An age- and sex-matched reference group was randomly selected from people visiting a hospital for regular health checkups. Intervals, amplitudes and abnormal findings from the electrocardiograms (ECGs) of the two groups were compared. Except for the PQ interval, there were no significant ECG differences between the two groups. The cases exhibited ECG abnormalities more frequently than the reference group. Multiple logistic regression analysis revealed that CS(2) poisoning was positively associated with the presence of abnormal ECG findings (OR = 1.603; 95% CI, 1.008-2.549). This study suggests that CS(2) poisoned subjects may have an increased risk of ECG abnormalities even after the exposure to CS(2) is no longer present.

Effect of Occupational Exposure to Rayon Manufacturing Chemicals on Skin Barrier to Evaporative Water Loss

To evaluate the effects of the occupational exposure to rayon manufacturing chemicals (RMC, containing predominantly carbon disulfide (CS(2)) and minor sulfuric acid) in a rayon factory on the basal transepidermal water loss (TEWL), barrier integrity (BI), and sequential increasing TEWL profiles. Six Thais and five Chinese workers in the spinning department of a rayon manufacturing plant and five healthy unexposed controls were recruited as the test subjects. An area of 4.5 x 5.5 cm on the mid-side of the volar forearm on the right hand was stripped by means of moderate pressure with commercially available adhesive tape by the same technician throughout the experiment. The skin was progressively stripped until glistening. TEWL was measured at every three and five tape strips on the right hand. The corresponding site on the left hand was measured parallel as the self-control. We found significant differences in basal TEWL and in BI between Chinese workers and Chinese controls, and between Thai workers and Chinese workers, respectively. Two-stage patterns of progressive TEWL profiles were found in such a chronic and repeated occupational exposure to RMC containing CS(2). The occupational exposure to RMC could result in the perturbation of the skin barrier function. Basal TEWL might be more sensitive to chronic skin irritant exposure. The TEWL profile achieved to the glistening stage might be necessary to avoid erroneous pattern estimation. Due to the lack of Thais control in this study, the racial difference in response to the RMC warrants further study.

Combined exposure to carbon disulfide and sulfuric acid simultaneously increases the risk of hand dermatitis in rayon industry.

To evaluate the association between hand dermatitis (HD) and occupational exposure to CS(2) and to determine whether combined exposure to CS(2) and H(2)SO(4) exhibits a higher risk of HD. In all, 110 subjects from a rayon factory were recruited and their exposure was classified into CS(2) exclusively, H(2)SO(4) exclusively, combined exposure, and nonexposure control based on workers' job characteristics. A dermatologist was designated in the diagnosis of HD on palm and dorsal sites for each subject. Other confounding factors including detergent, glove wearing, and participation in wet work were determined using a person-to-person questionnaire interview from 37 randomly selected subjects. Significant elevated odds ratios (ORs) for HD were found in CS(2) exclusively (44.8, P < 0.01) and combined exposure (49.0, P < 0.001) compared with control. Dose-response trends of ORs for HD were found across control, single exposure, and combined exposure for both CS(2) and H(2)SO(4). HD could occur resulting from occupational exposure to CS(2) alone. This study was unable to affirm that the exposure to H(2)SO(4) alone is associated with HD due to limited H(2)SO(4) exposure subjects. The combined exposure to both CS(2) and H(2)SO(4) simultaneously could increase the risk of HD. The control remedy in preventing dermal contact with either CS(2) or H(2)SO(4) among the rayon workers should be performed immediately.

Six year observational cohort study of the effect of carbon disulphide on brain MRI in rayon manufacturing workers

Aims: To clarify whether the current occupational exposure limit (OEL) for carbon disulphide (CS2) is low enough to prevent the occurrence of adverse effects on the cerebrovascular system. Methods: A...

Lack of relationship between occupational exposure to carbon disulfide and endocrine dysfunction: a six-year cohort study of the Japanese rayon workers.

A six-year prospective cohort study was conducted to clarify whether the current carbon disulfide (CS2) exposure level is low enough to prevent subclinical health impairment and/or to ameliorate health effects due to previous high exposure. This paper describes the follow-up results, exposure assessment, and effects on the endocrine system. The study subjects were 432 male workers exposed to CS2 at one of the 11 rayon factories in Japan and 402 referent workers from the same factories, all of whom were examined in 1992-93. 251 CS2-exposed, 140 former-exposed and 359 referent workers participated in the follow-up survey (follow-up rate 89.9%) in 1998-99. Urinary 2-thiothiazolidine-4-carboxylic acid (TTCA) at the end of a shift as internal exposure index and the time-weighted average CS2 concentration as external exposure index were measured twice a year from 1992-1993. By using various blood indices, we evaluated effects on thyroid, hypophysis, and gonad function, as well as effects on glucose metabolism. Information on potential confounding factors, such as age, smoking and alcohol drinking, were collected and adjusted for. When the individual exposure level was represented by arithmetic mean for TTCA and CS2 concentration, geometric means (SD) of CS2 workers were 1.61 (1.91) mg/g.crea and 5.02 (1.84) ppm, respectively. There were no exposure-related differences in glucose metabolism or any of the endocrinological indices. No biologically significant effects of CS2 were found on endocrine function in Japanese rayon manufacturing workers when the average internal and external exposure levels were maintained below the current occupational exposure limit.

Biological monitoring of carbon disulphide: kinetics of urinary 2-thiothiazolidine-4-carboxylic acid (TTCA) in exposed workers.

The objectives of this study was to establish the kinetics of urinary 2-thiothiazolidine-4-carboxylic acid (U-TTCA) for workers exposed to carbon disulphide (CS2) and to investigate the effects of volume and creatinine adjustment methods for urine measurement. Ten workers in the spinning department of a rayon factory were individually monitored for airborne CS2 concentrations, with consecutive urine samples collected for 24-38 hours after termination of exposure. The U-TTCA, urine volume and creatinine level were measured for each sample. First-order and biphasic kinetics were determined using the curve-fit method, for the measurement series. For the first-order kinetics linearity fit, statistically significant correlation coefficients of 0.74-0.98 and 0.86-0.99 were derived for the volume- and creatinine-adjusted methods, respectively. For the biphasic kinetics approach, the overall correlation coefficients were 0.544-0.999 and 0.171-0.999 for the first and second phases of the creatinine-adjusted method, respectively. A post-shift U-TTCA of 3.0 mg/g Cr. equivalent, 40% below the current BEI setting at nearly PEL exposed level, was found. In conclusion, first-order kinetic response was confirmed for U-ITCA. Both volume- and creatinine-based urine adjustment are satisfactory for TTCA assessment as a biomarker of individual CS2 exposure although the correlation for creatinine-based measurement was modestly superior to the volume-based analogue. Based on the results of this study,we recommend a re-evaluation of the current biological exposure index of 5 mg/g creatinine at a CS2 exposure level of 10 ppm.

The cross-sectional study of the health effects of occupational exposure to carbon disulfide in a Chinese viscose plant.

This article presents results of carbon disulfide exposure assessment in a Chinese viscose rayon factory and represents the cross-sectional study beginning phase of the occupational epidemiological project. The authors measured external exposure levels to carbon disulfide at a Chinese viscose rayon factory and monitored results as internal exposure indexes by testing urine samples of workers exposed to carbon disulfide levels. The rate at which carbon disulfide is metabolized by exposed subjects was demonstrated by 2-thio-thiazolidine-4-carboxylic acid (TTCA) concentrations in urine of exposed subjects, which was studied to determine best time points for internal exposure sampling. Carbon disulfide concentrations in the air of the workplace were analyzed with gas chromatography with flame photometric detector (GC-FPD); presence of TTCA in urine samples of subjects was determined using a modified high-performance liquid chromatography method. Kinetics of TTCA excretion was studied by analysis at different time points during and after exposure of workers to carbon disulfide. A total of 155 personal samples were obtained. Carbon disulfide concentration at staple viscose hall was found to be 13.72 +/- 1.12 mg/m3 in terms of geometric mean and geometric standard deviation. Carbon disulfide concentration at filament spinning hall was found to be 20.05 +/- 1.33 mg/m3. TTCA values of subjects at staple spinning hall were 1.18 +/- 0.43 and 1.07 +/- 0.38 mg/g creatinine for subjects working at filament spinning hall. The best time for TTCA sampling is at the end of the exposure-working shift.

Benthos of Lake Orta in the year 1996

Lake Orta has been interested since 1926 by severe industrial pollution, due to the effluents of a rayon (artificial silk) factory that discharged huge amounts of copper and ammonia. As a consequence, the benthic fauna faced noticeable changes, becoming extremely poor in species. However, after extensive liming (in 1989-90), the biotic communities of the lake showed many signs of recovery, and in 1996 it was decided to study the benthos composition and abundance in detail, to assess whether the lake restoration resulted in a complete recovery of this biotic compartment. Actually, both the small number of taxa, and the low abundance of the benthos, indicate that the sedimentary environment is still very stressed. In fact, albeit this study shows that benthos fauna is actively recolonising Lake Orta bottom, spreading from river mouths, in 1996 the benthic community cannot be considered fully organised.

Decreased carotid artery distensibility as a sign of early atherosclerosis in viscose rayon workers.

Carbon disulphide (CS(2)) is known to accelerate atherosclerosis and to increase the risk for cardiovascular diseases. To assess the effect of CS(2) on the functional (distensibility and compliance) and the structural (intima media thickness) properties of the common carotid artery, and blood pressure and lipid metabolism parameters, a cross-sectional study on 85 workers from a viscose rayon factory and 37 controls was carried out. Exposure to CS(2) was assessed by personal monitoring and was well below the threshold limit value-time weighted average. Carotid arterial wall properties were determined using a non-invasive ultrasound wall movement detector system. No significant effect of CS(2) on blood pressure, total cholesterol, high-density lipoprotein cholesterol, low-density lipoprotein cholesterol or triglycerides was found. Among the vascular parameters studied, only distensibility was significantly lower and heart rate was significantly higher in exposed subjects compared with the controls. In conclusion, occupational exposure to CS(2) may cause early alterations in arterial elastic properties in young individuals, and even before lipid and clinical findings have occurred, important functional changes in the vessel wall are present.

Zooplankton of Lake Orta after liming: an eleven years study

Lake Orta (N. Italy) was severely polluted from 1927 by an effluent from a rayon factory, which discharged great amounts of ammonium nitrogen and copper into the lake. In the mid nineteen fifties, some plating factories also started dumping chromium and aluminum. As a result of ammonium oxidation, the lake became very acid and the concentration of metals in the waters reached very high values. Phytoplankton, zooplankton and fish disappeared suddenly from the lake which was by 1930 classified as “sterile”. Later on, about the fifties, a small population of Cyclops abyssorum re-colonised the lake together with some rotifers, in particular Hexarthra fennica. In mid eighties following the introduction of anti-pollution legislation, ammonium loads were greatly reduced and Daphnia obtusa was recorded. The lake waters however were still very acid, prompting the proposal of the Istituto Italiano di Idrobiologia to lime the lake with calcium carbonate to neutralise the excess acidity and reconstruct the alkaline reserve. This was done successfully from May 1989 to June 1990. pH values began to rise and in the same time the metal concentrations decreased, so that at present the lake waters are almost “normal”. In the meantime, due to the increased pH values, D. obtusa was replaced by D. longispina and, as toxic metal concentrations became lower, Megacyclops viridis, Bosmina longirostris, Diaphanosoma brachyurum, Keratella quadrata, Asplanchna priodonta. and other Brachionidae species appeared. Diaptomidae are still absent, except for some specimens of Arctodiaptomus wierzejskii.

Lake Orta: the undermining of an ecosystem

From 1927 to 1986 Lake Orta (North-western Italy) received loadings coming from a rayon factory, rich in copper and ammonium sulphate. Immediately after the onset of pollution, the food web was destroyed: first phytoplankton, then zooplankton, and finally fish and ultraplankton disappeared from the lake. Twenty years later a rise in nitrate nitrogen and copper ions was recorded and in the early sixties ammonium nitrogen started to accumulate and pH to fall. In the meanwhile, a poorly structured biological community appeared, mainly composed of Cyclops abyssorum (copepod), Hexarthra fennica (rotifer) and Coccomyxa minor (green alga). Fish and benthonic animals were still absent. In 1986 the ammonium loading was substantially reduced (copper had been partially recovered since 1956), so that the in-lake ammonium concentration began to decrease. Some phyto- and zooplankton as well as benthic species were recorded in this period. Nevertheless, as pH was still very acid and alkaline reserve absent: a proposal to lime the lake was accepted and funded by regional authorities. Liming was performed in May 1989-June 1990 and resulted in a real improvement of the environment.

First phase of macroinvertebrate repopulation of Lake Orta (Buccione Basin) after liming

The research described here was performed during 1993 and 1994 in the context of studies on the recovery of Lake Orta from acidification after the liming conducted from May 1989 to June 1990. The causes of the pollution were due to the oxidation of ammonium sulphate discharged from a factory producing rayon by a cupro-ammoniacal method and to the loads of heavy metals (Cu, Cr, Ni, Zn) derived from plating factories. One year after liming, an increase in pH and a marked decrease in metal concentrations were observed, and as a consequence some qualitative and quantitative changes were observed in 1992-93 in the planctonic communities and in the littoral macrobenthic fauna. This paper presents qualitative and quantitative data on macrobenthos collected along a transect between the littoral and the maximal depth in the Buccione Basin, which was directly affected by the effluents of the rayon factory. The data revealed some quantitative repopulation of this community, especially along the littoral. Qualitatively, however, the macrobenthos was still quite poor, consisting essentially of Oligochaeta and Diptera Chironomidae. The former were rare and mainly represented by Naididae between 15 and 22 m, while the Tubificidae were well represented in the littoral and the profundal zones. As regards the Chironomidae, the genera Procladius and Chironomus gr. thummi extended as far as the maximum depth, while others, such as Ablabesmyia, Parakiefferiella bathophila and Dicrotendipes gr. nervosus were mostly distributed in the littoral layers. Among the other taxonomic groups only the Trichoptera and the Diptera Ceratopogonidae were quantitatively significant. However, many systematic entities typical of the less polluted Italian subalpine lakes are still absent. In fact, the colonisation of Lake Orta by macrobenthic organisms is still influenced by the increased concentrations of heavy metals in the sediment precipitated from the water column. The research included analysis of lake water and sediments chemistry to obtain information on the trophic level of the environment.

Gases (CH4, CO2 and N2) and pore water chemistry in the surface sediments of Lake Orta, Italy: acidification effects on C and N gas cycling

Lake Orta, a subalpine, warm monomictic lake in northwestern Italy was heavily polluted from rayon factory discharges of ammonium and copper since 1926. In the 1950s accumulations of contaminants resulted in whole lake pHs of 3.8-4.0 from ammonium oxidation. Partial remediation started in the 1950s, but by 1985-89 the water remained acidified at pHs of 4.0. Artificial liming (14,500 t) in 1989-90 resulted in improved water quality and substantial recovery of the biological community. Sediment gases, sampled in 1989 before liming, from the lake's four basins showed severe inhibition of methanogenesis (CH4 = 0.0-0.15 mM) in the surface sediments (0.5-5 cm) of the southern basin, location of the plant effluent, as compared to the deep central and northern basins (0.9-1.4 mM). Four years after liming, cores collected in 1994 near the 1989 southern basin sites showed a slight change in surface sediment methane (0.07-0.82 mM), yet suggested continual sediment toxicity, at least to carbon cycling through methanogenesis. Calculations of diffuse flux of CH4 at the sediment-water interface (SWI) in 1989 were 6.6-7.4 mM m-2 day-1 for the central and northern basins and 0.13 for the southern basin. CH4 fluxes increased 16x to 2 mM m-2 day-1 in 1994 in the southern basin, possibly from remediation of near surface sediments. The impact of pollution on denitrification (formation of sediment N2 gas) was not so obvious since two processes could counteract each other (high NO3 - stimulating denitrification versus possible negative effects from acidity and metals). The calculated flux of N2 from the southern basin sediments increased 5x four years after liming compared to the period of acidification, suggesting possible toxicity towards denitrifiers during the earlier period. Core overlying water (0.68 mM) exhibited N2 concentrations close to saturation, while most surface sediments were twice as much (1.5 mM). Surface (0-6 cm) sediment N2 was similar at most sites, with the exception of 0.82 mM in the low porosity sediments of the Omegna basin at the lake’s outlet. The calculated diffuse flux of N2 at the SWI averaged 4 mM m-2 day-1 for the entire lake and varied between 1.3 at Omegna to 7.3 at the Central basin. It is suspected that surface sediment N2 production from denitrification and subsequent flux from sediments to overlying waters should resolve much of the deficit in the mass budget for water column nitrogen during the acidification period where only 35 percent of the ammonium oxidation could be accounted for as nitrate.

Cardiovascular effects in viscose rayon workers exposed to carbon disulfide.

The objectives of this study were to investigate the cardiovascular effects in workers currently exposed to carbon disulfide (CS2) below the threshold limit value (TLV) of 31 mg/m3 and to determine the prevalence of coronary heart disease (CHD) after long-term exposure. 172 men (91 workers exposed to CS2 in a viscose rayon factory and 81 referent workers) were examined using a medical and job history questionnaire, Rose's questionnaire, and electrocardiography at rest, and by measuring blood pressure and serum lipids and lipoproteins. Personal exposures were monitored simultaneously with active sampling and findings were analyzed according to the NIOSH 1600 method. As a result of technical and organizational improvements, personal CS2 exposures were well below the TLV (5.4-13.02 mg/m3). No significant effect of CS2 on blood pressure or lipids (total cholesterol, HDL and LDL cholesterol, triglycerides, and apolipoproteins AI and B) was found, even after allowance for confounding factors. The prevalence of CHD (ECG abnormalities and chest pain) was higher in the viscose rayon workers than in the workers with no exposure but reached statistical significance for men with exposure histories often years and more only (cumulative CS9 index > or = 150 mg/m3, the most highly exposed group). The findings suggest that the coronary risk is increased in workers previously exposed to high CS2 concentrations but not in those exposed to CS2 levels below the current TLV.

Antioxidative stress response in workers exposed to carbon disulfide.

To study the effects of carbon disulfide (CS2) on antioxidative stress systems of exposed workers. Enzyme-linked immunosorbent assay (ELISA) and thiobarbituric acid test (BAT) were conducted on 67 exposed workers and 88 controlled ones in a viscose rayon factory to determine their serum cuprozinc-superoxide dismutase (CuZnSOD) and malonyldialdehyde (MDA) levels. The average levels of CuZnSOD in workers exposed to CS2 both above and below 10 mg/m3 were higher than those in the control group (P < 0.0001), showing some dose-effect and dose-response relationships. SOD levels increased when the exposure index (EI) was less than 300, and remained at a high level at the range of 300 to 900. When EI was higher than 900, SOD tended to decrease. Meanwhile, the serum MDA levels increased. Both CS2 concentrations and exposure time contribute to the MDA levels. CS2 exposure could influence the stress response of the oxidative-antioxidative system of workers. Increased SOD levels could be considered as the stress response of antioxidative system to CS2 exposure in the early stages, and the influence of CS2 on SOD might be bi-directional. SOD and MDA might become objective indices in workers' health surveillance. The role of these two indices in the intoxication mechanism still needs to be clarified.

Carbon disulfide at a Chinese viscose factory external and internal exposure assessment.

This article presents the results of carbon disulfide exposure measurements in a Chinese viscose rayon factory. The objectives of the study were to identify the external exposure levels at a large factory and to investigate the 2-thiothiazolidine-4-carboxylic acid (TTCA) concentrations in the urine of the subjects who were exposed to carbon disulfide in the working place atmosphere. The metabolism of carbon disulfide in the exposed subjects was also studied in order to demonstrate the best points in time for the internal exposure sampling. The measurement of the amount of personal exposure to carbon disulfide in the air of the workplace was performed by GC-FPD; the presence of TTCA in the workers urine was analyzed by use of a modified HPLC method. The kinetics of TTCA excretion was studied by analyses at different time-points both during and after exposure to carbon disulfide in the subjects. A total of 155 personal samples were obtained. The carbon disulfide concentration in the staple viscose hall was 13.72 +/- 1.12 mg m-3 in terms of the geometric mean +/- geometric standard deviation, and was 20.05 +/- 1.33 mg m-3 in the filament spinning hall. The TTCA values in the subjects who worked in the staple spinning hall were 1.18 +/- 0.43 mg g-1 creatinine and 1.07 +/- 0.38 mg g-1 creatinine for subjects working in the filament spinning hall. The best time for TTCA sampling is at the end of the working shift, the TTCA excretion was stable for a period of 4-12 h after exposure of the subjects to the carbon disulfide. It might be that the Chinese have different anthropometric characteristics; a sampling bias may therefore appear among different races.