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Key value for chemical safety assessment

Additional information

In vitro studies (bold = Key Study)

Huels AG (1989), Amoco Co. (1991), Zeiger et al. (1992),MHW Japan (1997), NTP (2007):

negative in Salmonella typhimurium TA 100, TA 1535, TA 1538, TA 98, TA 97, TA 1537 and Escherichia coli WP2 uvrA (with or without metabolic activation; study design comparable to OECD Guidelines No. 471 and 472)

MHW Japan (1997): no chromosomal aberrations or polyploidy in Chinese hamster lung cells (CHL/IU; with or without metabolic activation; study design comparable to OECD Guideline No. 473)

Amoco Co. (1991) / NTP (2007): no chromosomal aberrations in CHO cells (with or without metabolic activation; study design comparable to OECD Guideline No. 473)

Amoco Co. (1991): negative in the CHO/HGPT mutation assay (with or without metabolic activation; study design comparable to OECD Guideline No. 476)

NTP (2007): sister chromatid exchanges in CHO cells: positive with metabolic activation and negative without metabolic activation (study design comparable to OECD Guideline No. 479)

Norppa & Vainio (1983): sister chromatid exchange assay in lymphocyte cultures of a healthy male donor: ambiguous without metabolic activation

In vivo studies:

NTP (2007): micronucleus assay with a study comparable to OECD Guideline No. 474: no significant increases in the frequencies of micronucleated erythrocytes in blood samples of male mice obtained at the conclusion of the 3-month study, but significant increase in micronucleated erythrocytes in high-dosed (1000 ppm) females. Reticulocytes (polychromatic immature erythrocytes; PCEs) were also scored for frequency of micronucleated cells in male and female mice. No increase in micronucleated PCEs was observed in either sex at the highest exposure concentration of 1000 ppm, indicating that the damage observed in the mature erythrocyte population in 1000 ppm females was reflective of long-term accumulation of damage and was not detectable immediately after exposure by analyzing recently-formed (within 48 hours) reticulocytes. In view of the nature of the observed increases in micronucleated cells in these female mice and the clear absence of clastogenic effect observed in mammalian cells in vitro, the significance of this weak positive result is uncertain (high dose only, without trend).


Short description of key information:
With alpha-methylstyrene a variety of different in vitro and in vivo studies have been performed, which in total gave no indication for a mutagenic/genotoxic potential of the substance.

Endpoint Conclusion: No adverse effect observed (negative)

Justification for classification or non-classification

Based on the available and valid in vitro and in vivo data a classification is not needed.