Sodium O-isobutyl dithiocarbonate

Epidemiological data

Administrative data

Endpoint:

epidemiological data

Type of information:

other: Human observational study

Adequacy of study:

supporting study

Reliability:

3 (not reliable)

Rationale for reliability incl. deficiencies:

other: see 'Remark'

Remarks:

Relevant methodological deficiencies or limitations: the authors did not adjust for age, a confounder that affects ophthalmological health. Carbon disulphide is both a reagent in the manufacture, as well as a decomposition product of xanthates. Sodium isobutyl xanthate readily decomposes to carbon disulphide, especially in the presence of moisture/water. Therefore, the health effects of carbon disulphide (CS2) need to be considered in the assessment of sodium isobutyl xanthate. In addition, xanthates decompose on aging to form a number of byproducts, depending on the pH, temperature, etc. Risks associated with xanthate are, therefore, a function of the breakdown of the product or un-reacted raw materials remaining in the product.

Data source

Reference

Reference Type:

publication

Title:

Cross-sectional study of the ophthalmological effects of carbon disulfide in Chinese viscose workers

Author:

Wang C, Tan X, Bi Y, Su Y, Yan J, Ma S, He J, Braeckman L, De Bacquer D, Wang F, Vanhoorne M

Year:

2002

Bibliographic source:

Int. J. Hyg. Environ. Health 205:367-372

Materials and methods

Study type:

cross sectional study

Endpoint addressed:

eye irritation

repeated dose toxicity: inhalation

Test guideline

Qualifier:

no guideline available

GLP compliance:

not specified

Test material

Test material information

Constituent 1

Reference substance name:

Carbon disulphide

EC Number:

200-843-6

EC Name:

Carbon disulphide

Cas Number:

75-15-0

Molecular formula:

CS2

IUPAC Name:

dithioxomethane

Test material form:

aerosol dispenser: not specified

Remarks:

migrated information: aerosol

Details on test material:

Carbon disulphide is both a reagent in the manufacture, as well as a decomposition product of xanthates. Sodium isobutyl xanthate readily decomposes to carbon disulphide, especially in the presence of moisture/water. Therefore, the health effects of carbon disulphide (CS2) need to be considered in the assessment of sodium isobutyl xanthate.
In addition, xanthates decompose on aging to form a number of byproducts, depending on the pH, temperature, etc. Risks associated with xanthate are, therefore, a function of the breakdown of the product or un-reacted raw materials remaining in the product.
- Name of test material (as cited in study report): Carbon disulfide

Method

Type of population:

occupational

Ethical approval:

not specified

Details on study design:

METHOD OF DATA COLLECTION
- Type: Questionnaire, Medical tests
- Details:
Current exposure was assessed using personal sampling. Historical exposure was assumed to be at similar levels because of no change in production techniques and evidence of similar levels from past records.
A questionnaire was used to gather information on education, smoking, drinking, occupational history, and medical history.
An ophthalmologist examined color vision and fundus.

STUDY PERIOD: 1997 - 1999

SETTING: Rayon-Viscose factory in China.

STUDY POPULATION
- Selection criteria: Minimum of 5 years work in the viscose rayon factory, no use of diabetic medicine, or chemicals that interfere with visual function.
- Total number of subjects participating in study: 271 CS2 exposed workers and 133 non-exposed workers.

HEALTH EFFECTS STUDIED:

Ophthalmological effects - eye complaints, color vision, retinal capillary anomalies

Exposure assessment:

measured

Details on exposure:

Current exposure was assessed using personal sampling. Historical exposure was assumed to be at similar levels because of no change in production techniques and evidence of similar levels from past records.
The CS2 exposure level in the study was 13.7 ± 20.05 mg/m3.

Statistical methods:

Prevalence of abnormal ophthalmologic findings in the different groups was compared using Fisher's exact test. The distributions of quantitative outcomes in both groups was tested according to the Analysis of Variance (ANOVA) and Student Newman-Keuls (SKN) test. Since the error scores of color discrimination were best fitted by a log normal distribution, Geometric mean +/- Geometric Standard Deviation was used in the statistical analyses.

Results and discussion

Results:

BASELINE CHARACTERISTICS

Participation rates were 94.3% and 95.2% in the exposed and control group respectively.

The two groups were also similar in sex, average age, smoking and drinking behaviour.

EXPOSURE:

The CS2 exposure level in the present study was 13.7 ± 20.05 mg/m3.

FINDINGS:

Male workers had a higher frequency of low color discrimination and a higher total error score than control group workers. This relationship was not statistically significant among female workers.

When stratified into 5-year employment duration categories:
Total error scores of the exposed were significantly higher than that of controls in all the 5-year groups.

Total error scores tended to rise with the duration of employment in males as well as in females, both in exposed and controls.

The green-zone error scores of the exposed were significantly higher than that of controls in the 5 - 9 years group for males and females.
The blue-zone error scores of exposed was only significantly higher than that of controls in the 5 - 9 year group for males.

In the exposed, the males' total error score and the blue-zone score of the 15 - 20 years group were significantly higher than that of the 5 - 9 years group.

The total errors score of females in the 15 ± 20 years group was significantly higher than that of the other groups.

Fundus examination of the subjects showed that the difference between exposed and control group was not statistically significant. No differences in prevalence of retinal capillary anomalies, such as retinal bleeding or retinal microaneurysms were found between exposed and unexposed groups.

Confounding factors:

Co-variance analysis was performed for smoking, alcohol consumption, and family income. Age was a potential confounder which was not controlled for.

Strengths and weaknesses:

Strengths: Exposure levels were quantitatively measured, and compared with historical records for consistency before extrapolating them to previous decades.

Weaknesses:
The cross-sectional study design is inherently weak due to an inability to determine temporal relationships between exposure and outcome, and difficulty in avoiding bias in the selected study sample.

Age which is a key confounder was not accounted for in analysis.

Applicant's summary and conclusion

Conclusions:

At CS2 concentrations of 13.7 ± 20.05 mg/m3, exposed subjects showed lower color discrimination when compared with those of the control group. Green-zone and blue -zone of color vision were more sensitive to the effect of CS2 than red-zone color vision. This association is possibly confounded by age which was not controlled for.
Workers with long-term exposure to CS2 did not report serious subjective symptoms. No retinal capillary anomalies were observed.
Carbon disulphide is both a reagent in the manufacture, as well as a decomposition product of xanthates. Sodium isobutyl xanthate readily decomposes to carbon disulphide, especially in the presence of moisture/water. Therefore, the health effects of carbon disulphide (CS2) need to be considered in the assessment of sodium isobutyl xanthate.
In addition, xanthates decompose on aging to form a number of byproducts, depending on the pH, temperature, etc. Risks associated with xanthate are, therefore, a function of the breakdown of the product or un-reacted raw materials remaining in the product.

Executive summary:

To evaluate the ophthalmological effect of carbon disulfide exposure on workers, 271 exposed workers in a viscose rayon factory were compared to 133 reference unexposed workers. Exposure levels were estimated using personal air samplers and cumulative exposure was estimated from it assuming an unchanged exposure environment. Self - administered questionnaires gathered information on medical and job history, and ophthalmological complaints, during past three months. An ophthalmological examination was conducted to identify retinal capillary anomalies and color vision. Results indicated that color vision was disturbed among workers who were exposed to average concentrations of 13.7 - 20.05 mg/m3. Workers with long-term exposure to CS2 did not report serious subjective symptoms. No retinal capillary anomalies were observed. The investigators failed to control for age, a confounder that affects ophthalmological health.