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and an equivalent weight of Fe 2 O 3 (hematite) as particulate carrier. Tumors were not present in animals
receiving ferric oxide or in untreated controls. Respiratory tract tumors (including squamous cell
carcinomas of the larynx, of the trachea, and of the bronchi, adenocarcinomas of the bronchi, and
adenomas of the bronchi and of the bronchioles and alveoli) developed in all groups of BaP/Fe 2 O 3
treated animals. The response was dose related.
In another experiment, Feron et al. (1973) gave male Syrian golden hamsters intratracheal doses of 0,
0.0625, 0.125, 0.5, or 1 mg BaP weekly for 52 weeks. A variety of tumors were produced throughout
the respiratory tract, including bronchoalveolar adenomas and carcinomas.
Thyssen et al. (1980) conducted an inhalation study in which male Syrian golden hamsters were
exposed to BaP condensation aerosol (in 0.1% saline; particle size ranging from 0.2 to 1.5 µm) for 10
to 16 weeks at a concentration of 9.8 to 44.8 mg BaP/m 3 . Neoplastic changes in the respiratory tract
were not seen.
In a subsequent experiment, Thyssen et al. (1981) exposed male Syrian golden hamsters to BaP
condensed onto sodium chloride particles at BaP concentrations of 2.2, 9.5, and 46.5 mg BaP/m 3 .
Tumors were not observed in the respiratory tract of the unexposed control group or the group that
received 2.2 mg/m 3 . The incidence of tumors in this organ system increased in a dose dependent
manner for the 9.5 and 46.5 mg/m 3 exposure groups. Papillomas, papillary polyps, and squamous cell
carcinomas were seen in the nasal cavity, larynx, trachea, pharynx, esophagus, and forestomach. Lung
tumors were absent.
(b) Feeding Studies
Feeding of pelletized chow containing BaP (50 to 250 ppm BaP for 4 to 6 months) to male and female
CFW mice caused gastric tumors (papillomas and squamous cell carcinomas), pulmonary adenomas,
and leukemia (Rigdon and Neal, 1966; 1969; Neal and Rigdon, 1967). The pulmonary adenomas,
gastric tumors, and leukemia occurred independently of each other (Rigdon and Neal, 1969). The
overall data strongly suggest a positive carcinogenic effect since there were no gastric tumors in 289
control mice while 178 out of 454 mice fed various levels of BaP had gastric tumors (Neal and Rigdon,
1967).
(c) Dermal Application
BaP has been shown to be carcinogenic by dermal application (ATSDR, 1990). Wynder and
associates demonstrated a positive dose-response relationship for BaP-induction of skin tumors in
Swiss and in C57BL mice and showed a tumor response at doses as low as 0.001% BaP applied
topically in acetone every 2 weeks for up to 2 years (Wynder and Hoffmann, 1959; Wynder et al.,
1957; 1960). In addition, incidences of 95% for papillomas and carcinomas of the skin were obtained
by chronic administration (3 times weekly for 1 year) of 0.001% BaP to the skin of Swiss mice
(Wynder and Hoffman, 1959). Extensive experiments conducted by Conney and associates
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