Risk assessment places rubber chemical under scrutiny

An intermediate in rubber manufacture has been provisionally identified as meeting EU screening criteria for persistent, bioaccumulative and toxic (PBT) substances, prompting regulators to seek information on exposure from carpets, paper coatings, mattresses and other products.

An environmental risk assessment, issued by the Environment Agency in January,1 indicates that many uses of tert-dodecanethiol (TDM) pose potential risks, in particular emulsion polymerisation.

TDM is used as a reactive intermediate in the production of styrene butadiene rubber and acrylonitrile butadiene, or nitrile, rubber. The predominant use of the former is in automotive tyres. Other uses include mats, footwear, conveyor belts, container seals, hoses and cables.

If the assumed level of residual TDM in rubber and polymer dispersions are shown to be correct, the study says, then a risk may arise from downstream applications including:

  • Carpet and textile manufacture.

  • Paper coating and recycling.

  • Foam pillow and mattresses.

  • Formulation of products for inks, adhesives and construction.

    The Agency stresses that it has used conservative default values to fill data gaps, increasing uncertainties. The risks relate to marine sediments, freshwater sediments and seawater.

    TDM is produced in France, Germany and Belgium. The Agency says that where TDM is used in processes it regulates it will seek to ensure that best available techniques are used to minimise releases. The Agency has collected sediment monitoring data, but it is not yet possible to draw firm conclusions because of difficulties in developing suitable analytical methods for TDM.

    The Agency intends to work with industry and the Chemical Stakeholder Forum to formulate measures to reduce risks. It is seeking further information from industry on the intrinsic properties of thiols and their use patterns and emissions. In particular, it is seeking information on the levels of residual TDM in polymer emulsions and final products.

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