Influence of inhaled cadmium microparticles on mouse influenza pneumonia.

A study of the effect of inhaled cadmium microparticles (CdO) on the mouse death rate from influenza pneumonia was performed on 936 female specific pathogen-free (SPF) Swiss mice. The test animals received a single short (15 min) exposure to 9 mg Cd/m3 of air (acute exposure), or renewed short exposures to 1 mg/m3 once a day, 5 days a week, for 4 weeks (chronic exposure). The cadmium found in the trachea-bronchus-lung area was about 5 micrograms/g of fresh tissue at the end of acute exposure, and 4 micrograms/g at the end of chronic exposure. The viral challenge was performed 48 hr after acute exposure, or on the 14th day after the beginning of chronic exposure, the mice being reexposed to Cd for an additional 14 days in the latter case. Surprisingly, the infectious death rate of test mice was significantly lower than that of controls, both for acute and chronic exposure to CdO. These results are discussed.