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Toxicological information

Epidemiological data

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Administrative data

Endpoint:
epidemiological data
Type of information:
experimental study
Adequacy of study:
supporting study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: acceptable, well-documented publication which meets basic scientific principles

Data source

Referenceopen allclose all

Reference Type:
publication
Title:
Mortalities of workers at the nitro plant with exposure to 2-mercaptobenzothiazole
Author:
Collins, J., J.; et al.
Year:
1999
Bibliographic source:
Occup. Environ. Med. 56, 667-671
Reference Type:
other: microfiche
Title:
An update of the 2-mercaptobenzothiazole study at the nitro plant, study 9504, January 1996
Author:
Monsanto Co.
Year:
1996
Bibliographic source:
NTIS/OTS0572929

Materials and methods

Study type:
cohort study (retrospective)
Endpoint addressed:
carcinogenicity
Principles of method if other than guideline:
other: cohort mortality study
GLP compliance:
no

Test material

Reference
Name:
Unnamed
Type:
Constituent
Details on test material:
MBT

Method

Details on study design:
cohort mortality study, examination of mortality of MBT exposed worker
Exposure assessment:
estimated

Results and discussion

Results:
Exposure to MBT does not seem to increase the risk of most cancer including cancers of the lung and prostate.
The confounding effect of PAB makes it impossible to evaluate MBT induced risk of bladder cancer in this population at this time.
Confounding factors:
exposure to 4-aminobiphenyl (PAB)

Any other information on results incl. tables

MBT workers have expected rates of lung and prostate cancer. There was an excess of bladder cancer among MBT worker who had definite exposure to PAB and MBT workers with potential exposure to PAB. However, there were no deaths from bladder cancer among workers with no exposure to PAB.

The authors concluded that the potential confounding of exposure to an unknown portion of PAB in the MBT workers makes it impossible to evaluate risk of bladder cancer in this population at this time. However, exposure to MBT doses not seem to increase the risk of most cancers including cancers of the lung and prostate.

Applicant's summary and conclusion

Conclusions:
MBT workers have expected rates of lung and prostate cancer. There was an excess of bladder cancer among MBT worker who had definite exposure to PAB and MBT workers with potential exposure to PAB. However, there were no deaths from bladder cancer among workers with no exposure to PAB.
The authors concluded that the potential confounding of exposure to an unknown portion of PAB in the MBT workers makes it impossible to evaluate risk of bladder cancer in this population at this time. However, exposure to MBT doses not seem to increase the risk of most cancers including cancers of the lung and prostate.
Executive summary:

In a follow up study, the mortalities of workers at the Nitro plant (West Virginia) with exposure to 2-mercaptobenzothiazole were evaluated (Collins 1999). In this study the mortalities of 1059 full time white male production workers employed at the plant from 1955 to 1977 were analyses. A detailed exposure assessment was done on the 600 workers with exposure to MBT. Nine years of additional follow up to the previous study (Strauss 1993) were added. In the follow-up study the standardised mortality ratios of the production workers for all causes of death and all cancers was at expected levels, which was different from the findings of the original study (Strauss 1993). For the entire follow up period lung cancer, prostate cancer, and the other cancer sites examined were at expected levels. Among the cancers, only rates of bladder cancer were greater than expected for the entire follow up period. The standardised mortality ratios for total cancer of workers exposed to MBT and potential exposure to PAB were similar to the entire study group and to the local population. Rates for lung cancer and prostate cancer were at expected levels. The standardised mortality ratio for bladder cancer was greater than expected when compared with the external reference group. The number of total cancers was greater than expected for MBT workers with one or more jobs with exposure to PAB. The number of lung cancers and bladder cancers for this group of workers were greater than expected. The MBT workers without a job definite exposure to PAB during their careers had an observed total cancer rate which was lower than expected. Observed deaths from bladder cancer, however, were greater than expected in this group based on five deaths. The five workers who died of bladder cancer held jobs with plant-wide responsibilities. These five workers had job titles of maintenance worker, yard labourer, or general production worker and thus the authors suggested that a possible risk of exposure to PAB. Workers with no potential exposure to PAB, or those workers hired after 1955, have a lower observed than expected risk of total cancer and there were no deaths from bladder cancer. The authors concluded that MBT workers had bladder cancer rates which were greater than expected, but an unknown portion of these workers had exposure to PAB. The potential confounding exposure to PAB, a potent bladder carcinogen, in an unknown portion of the MBT workers makes it impossible to evaluate risk of bladder cancer in this population. Although the lack of bladder cancers among workers hired after PAB manufacture ended would argue against a relation with exposure to MBT, the number of expected deaths in this group of workers is too small to be conclusive.