Chemical changes of rubber allergens during vulcanization
O. Bergendorff*1, C. Persson1, A. Lüdtke2, C. Hansson1
1Department of Dermatology, Lund University, Lund, Sweden
2Technical Centre, Trelleborg Industry AB, Trelleborg, Sweden
Background
Allergic contact dermatitis to rubber additives is a serious occupational health problem. The disease is more often seen among users of rubber products than personnel in the rubber industry. Occupations at risk are for example healthcare workers using disposable gloves and car factory workers assembling rubber details. Information on which allergens these individuals are exposed to are often based on data from the manufacturer on what raw materials that has been used. However, the additives are reactive chemicals and the vulcanization is performed at elevated temperature for a considerable time. This will most likely result in chemical changes of the rubber constituents during the process and result in an unknown composition of the material.
Methods
Collaboration has been established between the Department of dermatology at Lund University and a Swedish rubber factory (Trelleborg AB) aiming to investigate the chemistry of allergenic rubber additives. A synthetic rubber was prepared in an experimental scale at the site in Trelleborg. The rubber was made from well defined ingredients including common accelerators that are known to cause allergic reactions. At different stages during the process samples were taken out and deep frozen to stop the reaction. The samples were then analysed by HPLC and the reactions of the different additives were monitored.
Results
The common accelerator TMTD (tetramethythiuram disulfide) together with CBS (N-cyclohexyl-2-benzothiazyl sulphenamide) and MBTS (dibenzothiazyl disulphide) were added to the rubber before vulcanization. All of these compounds were consumed during the process. Instead two other contact allergens, ZDMC (zinc dimethyldithiocarbamate) and MBT (2-mercaptobenzothiazole) were present in the final product. Intermediate products appeared during the process.
Conclusions
An assessment of exposure to contact allergens in products used in occupational activities, cannot only be based on information on what additives were used in the manufacturing of the rubber product. Instead, chemical analysis of the products in use must be performed to take into account the chemical changes occurring during vulcanization. Such changes will result in both disappearance and formation of allergens. Collaboration in this project between expertise from both rubber industry and an allergy research unit has given important insight into the chemistry of rubber allergens.
Content last modified: 22 May 2005
