Magnesium oxide as carrier dust in benzo(a)pyrene-induced lung carcino-genesis in Syrian hamsters

The neoplastic progression induced by intratracheal instillation of benzo[a]pyrene (BP) and magnesium oxide (MgO) was compared with that induced by intratracheal instillation of BP and ferric oxide (Fe2O3). BP and MgO produced squamous cell carcinomas and papillomas in the larynx with a latent period as shor as 9 weeks. They also induced many papillomas as well as squamous cell carcinomas and adenocarcinomas in the trachea and a papilloma, squamous cell carcinomas, adenocarcinomas, adenosquamous lesions, and peripheral adenomatoid lesions in the bronchi. They rarely caused tumors in other organs; only a few forestomach papillomas, one melanoma on the dorsal skin, and one ovarian carconoma were seen BP, with Fe2O3 as the carrier, induced a comparable number of histologically similar tumors; however, tumors developed more frequently in the main bronchi. Thus MgO strongly facilitated the tumor-inducing effects of BP, causing tumors in different areas of the respiratory tract, and was as effective as Fe2O3 as a carrier agent in the experimental induction of respiratory tumors.