Toxicity of chronic benzene inhalation: CD-1 mice exposed to 300 ppm

Benzene exposure effects on a mouse strain that does not harbor an endogenous lymphoma virus were studied. Exposed and control groups-each of 40 male, six-week-old Charles river, MA, Cd-1 mice-were studied over 222 calendar days. Mice exposed to benzene received a mean daily concentration of 300 plus or minus 2.6 ppm. Mean survival after the first exposure for benzene-exposed and sham-exposed mice was 179 days and 369 days, respectively. Chronic benzene exposure resulted in mortality, weight loss, and significantly reduced circulating red cell and lymphocyte levels. Suspending exposures after 31 weeks did not retard the mortality rate of the nine surviving benzene-exposed mice; these lifeshortening effects preclude study of tumor incidence at this high level. Benzene exposure has been linked to such hematological disorders as pancytopenia and acute myeloblastic leukemia.