Impurity variations in a carbon black: Characterization by the ames Salmonella mutagenicity assay and polycyclic aromatic hydrocarbon analysis

Samples of a furnace carbon black, N-330, were collected from the production line during a period of three years. Following extraction with benzene and solvent exchange, the mutagenic response was determined with the Ames Salmonella assay in the TA98 and TA100 strains with and without addition of S9. The samples were mainly mutagenic in the presence of S9, showing that polycyclic aromatic hydrocarbons (PAHs) were the major mutagenic impurities. The mutagenic response varied 30-fold among the samples. Analysis of PAHs in the range from phenanthrene to coronerie also showed a wide variation between samples being correlated to the mutagenic response. The large concentration differences of impurities between batches implies that a single batch cannot be used for generalized toxicological studies. The presence of PAH and mutagenic impurities in the investigated carbon black is a significant source of these environmental pollutants compared to another source of concern, automobile exhaust.