Studies demonstrating that
naphthalene produces respiratory tract
tumors in mice and rats raised the question of whether humans are at risk for
cancer, at environmental or workplace concentrations of
naphthalene. Arguments in favor of a threshold-dependent mode of action for
tumor induction have been based on the facts that
naphthalene does not appear to bind to
DNA in vivo and that the rodent
tumors occurred at high dose levels associated with substantial target site toxicity. A summary of more than 45 publications describing results for
naphthalene in genetic toxicology test methods shows that 80% of the studies reported found no evidence of genotoxicity for
naphthalene and that some of the studies which reported positive finding were technically unsuited to study this class of chemicals and, therefore, generated unreliable data. The remaining positive findings for
naphthalene were all consistent with secondary
DNA effects produced by toxicity from
naphthalene alone or one of its metabolites. Based on the data reviewed in this report, it is not apparent that genetic lesions produced by
naphthalene or any of its metabolites drive the tumorigenic activity.