The new born NMRI mouse, a very sensitive animal model to measure the carcinogenic potential of a PAH-containing test atmosphere by inhalation exposure

Newborn and 7-month-old NMRI and C57BL/6N mice were exposed in whole body horizontal air flow exposure chambers 17h/day for 5 days or for 4 weeks (newborn mice) and for 17 weeks (7 month old mice) to 1.1 mg/m3 of a coal tar/pitch condensation aerosol (CTP) containing 20 ug/m3 BaP among other PAH. 10 months (20 months) after starting the 4-week exposure period, the newborn NMRI mice showed a lung tumor rate of 87 (97) %. The exposure for only 5 days led to a tumor rate of 33% (30%) after 10 months (20 months) experimental time. The corresponding control groups had a lung tumor rate of 13 (17) %. These data show that the lung tumor rate after 10 months experimental time was very similar to the tumor rate found after 20 months. An increased number of malignant and multiple tumors was found after 20 months but, only in the 4-week exposure group.