Thiocarbamates Group - information sheet

Thioperoxydicarbonic diamide ([(H2N)C(S)]2S2), tetramethyl- (TMTD, also referred to as Thiram or Thiuram)
CAS Registry Number 137-26-8

Piperidine, 1, 1'-(tetrathiodicarbonothioyl)bis- (DPTT)
CAS Registry Number 120-54-7

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Overview

  • The Government of Canada conducted a science-based evaluation, called a screening assessment, of 2 substances in the Thiocarbamates Group (TMTD and DPTT) to address the potential for harm to Canadians and the environment. The screening assessment focuses on non-pesticidal uses of substances. The pesticidal uses of TMTD (known as Thiram) are being re-evaluated by Health Canada's Pest Management Regulatory Agency (PMRA).
  • Under the Canadian Environmental Protection Act, 1999 (CEPA 1999), the risk posed by a substance is determined by considering both its hazardous properties (its potential to cause adverse human health or ecological effects) and the amount of exposure there is to people or the environment. A substance may have hazardous properties; however, the risk to human health or to the environment may be low, depending upon the level of exposure.
  • TMTD is associated with human health and ecological effects of concern. As a result of this screening assessment, TMTD is proposed to be harmful to the environment but not to human health, for non-pesticidal uses of the substance (the focus of this assessment). DPTT is not proposed to be harmful to human health or to the environment as the risk posed by this substance is low.

About these substances

  • This screening assessment focuses on 2 substances, thioperoxydicarbonic diamide ([(H2N)C(S)]2S2), tetramethyl- and piperidine, 1,1'-(tetrathiodicarbonothioyl)bis-. These are also referred to as TMTD (or Thiram or Thiuram) and DPTT, respectively. They were assessed as part of the third phase of the Chemicals Management Plan (CMP).
  • TMTD and DPTT are industrial chemicals that do not occur naturally in the environment.
  • Industry data collected by the Government indicates that both TMTD and DPTT are imported into Canada but not manufactured in Canada. More information on the data collected by the Government may be found in the specific information gathering initiatives.
  • In Canada, TMTD is used in the manufacture of rubber products and a limited number of food packaging materials. It has uses as a component in automotive parts, in sealants and adhesives, and in adhesive tape products available to consumers. TMTD (known as Thiram) is also used as an active ingredient in pest control products.
  • In Canada, DPTT is only used in the manufacture of rubber products.

Exposure of Canadians and the environment

  • Exposure of Canadians to TMTD in Canada from products available to consumers (for example, rubber products, adhesive tape products, automotive parts or food packaging materials) is minimal or not expected.
  • Canadians may be exposed to TMTD from pesticidal uses; however, these sources of exposure are being addressed by the PMRA as part of the re-evaluation of the pesticidal uses of TMTD (Thiram).
  • The human health risk of DPTT was characterized using the Threshold of Toxicological Concern (TTC)-based Approach for Certain Substances. The estimate of exposure generated for DPTT was lower than the TTC value, indicating low concern to human health on the basis of current levels of exposure.
  • TMTD and DPTT have the potential to be released to the environment through discharges from wastewater treatment systems associated with manufacturing facilities for rubber products. Such releases are likely to result in exposure to aquatic organisms near points of release.

Key health and ecological effects (hazard)

  • To identify effects of concern for human health and the environment, national and international reports on TMTD were reviewed and used to inform this screening assessment.
  • In 2016, the PMRA published a proposed re-evaluation decision on the pesticidal uses of TMTD (Thiram). That evaluation identified health effects of concern for TMTD, including developmental neurotoxicity and carcinogenicity (ability to cause cancer).
  • Empirical data suggest that TMTD is highly toxic to aquatic organisms.
  • DTPP does not demonstrate any effect on aquatic organisms at its water solubility limit.

Risk assessment outcomes

  • Using the Threshold of Toxicological Concern (TTC)-based Approach for Certain Substances, DPTT is considered to be a low concern for human health at current levels of exposure.
  • Considering all information presented in the screening assessment, there is low risk of harm to organisms and to the environment from DPTT.
  • Based on the information presented in the screening assessment, the risk to human health from non-pesticidal uses of TMTD is low.
  • TMTD is not expected to remain in the environment for a long time or to accumulate in organisms. TMTD is, however, highly toxic to aquatic organisms. Exposure associated with current uses of this substance may pose a risk of harm to organisms.
  • The Government of Canada published the Draft Screening Assessment for the Thiocarbamates Group on February 3, 2018. This publication has a 60-day public comment period ending on April 4, 2018.

Proposed screening assessment conclusions

  • As a result of this screening assessment, the Government is proposing that TMTD is entering or may enter the environment at levels that may be harmful to the environment from its uses in the manufacture of rubber products.
  • However, the Government is proposing that TMTD is not harmful to human health at current levels of exposure from its non-pesticidal uses.
  • The Government is also proposing that DPTT is not entering the environment at levels that may be harmful to human health or to the environment.

Preventive actions and reducing risk

  • The Government of Canada published the Risk Management Scope Document for TMTD on February 3, 2018. This publication has a 60-day public comment period ending on April 4, 2018.
  • The Government intends to add TMTD to Schedule 1, also called the List of Toxic Substances, of CEPA 1999.
  • If the proposed conclusion is confirmed in the final screening assessment, the Government will consider the implementation of regulatory and/or non-regulatory controls to minimize the release of TMTD to the Canadian environment.
  • The PMRA proposed that Thiram pesticide products pose potential risks of concern to human health and the environment. As a result, uses of Thiram (TMTD) in all pest control products are proposed for cancellation. The PMRA's final re-evaluation decision is expected in the summer of 2018.
  • Although TMTD is not considered to be harmful to human health at current levels of exposure from non-pesticidal uses, this substance is recognized as having potential effects of concern (developmental neurotoxicity and ability to cause cancer). Therefore, there may be a concern for human health if exposures were to increase.
  • Follow-up activities to track changes in exposure and/or commercial use patterns for TMTD are being considered.
  • Stakeholders are encouraged to provide any information relevant to this substance that may help inform the choice of tracking activity, during the 60-day public comment period on the assessment. This could include information on new or planned import, manufacture or use of the substance, if this information has not already been submitted.
  • Further information and updates on risk management actions can be found in the CMP risk management actions table and the two year rolling risk management activities and consultations schedule.

Important to know

  • Canadians who may be exposed to TMTD or DPTT in the workplace should consult with their employer and an occupational health and safety (OHS) representative about safe handling practices, applicable laws, and requirements under OHS legislation and the Workplace Hazardous Materials Information System (WHMIS).
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