Study of powder stains used in the 1950s until the 1970s with regard to their content of azo dyes

Status:

completed 12/2007

Aims:

In the past, water-soluble pigmented stains were in use in the joinery trade which consisted partly of azo dyes; these in turn could potentially be cleaved into carcinogenic aromatic amines. Research conducted during investigations into cases of formally recognized occupational disease (BK) No. 1301, concerning changes to the mucous membranes, cancer or other growths in the urinary tract caused by aromatic amines, has revealed that the work of mixing the pigmented stain powders with water and applying the solution using brushes or pads was generally performed manually.
During mixing, and possibly during subsequent work (brushing, polishing with a chamois leather), a risk of inhalative exposure existed. Dermal exposure occurred particularly when pads were used for application of the stains. For the purposes of retrospective investigations concerning reported cases of occupational disease, information is desired on the azo dyes and aromatic amines used in the past for wood staining, and if appropriate on the quantities concerned. Once obtained, original samples are to be analysed appropriately.

Activities/Methods:

Approximately 160 powder stains used in the 1950s and 1970s were to be studied with reference to DIN EN 14362, "Methods for determination of certain aromatic amines derived from azo colorants".
For this purpose, the stains were subjected to reductive azo cleavage; the amines which were released were derivatized by means of heptafluorobutyric acid anhydride and then analysed by means of gas chromatography/mass spectrometry. The content was determined semiquantitatively by means of standards.

Results:

No aromatic amines classified as carcinogenic category K1 were detected in approximately 80% of the samples, and in approximately 50% of the samples, neither K1 nor K2 amines. Where present in samples, K1 amines did not exceed 35 mg/kg. It may therefore be concluded that azo pigments based upon K1 amines are very likely to have been of only minor relevance in the past as components of wood stains. In the majority of samples containing K2 amines, too, the content was found to be lower than 100 mg/kg. However, a proportion of the samples containing K2 amines were found to have concentrations in the order of several thousand (up to a maximum of several tens of thousand) mg/kg. This indicates that these stains contained K2-based azo dyes in the order of double percentage points. 4-Aminoazobenzene and o-toluidine were the amines most frequently encountered. The results of the project may be used in future investigations into cases of occupational disease.

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