Comparative response to long-term particle exposure among rats, mice, and hamsters

Ultrafine particles (...) showed an exposure concentration-dependent increase of the lung tumor rate in rats. Particle mass and particle surface area retained in the lungs of rats exposed to diesel soot, carbon black, and ultrafine TiO2 did not correlate well with the induced lung tumor rates. Even the tumorigenic potencies of various ultrafine carbon particles that differd in their specific surface areas by a factor of more than 10 showed no clear correlation with the particle surface areas retained in the lungs. Other particle characteristics like crystal structure, chemical functionality of particle surface, deaggregation behavior in the lung, and solubility of particle-attached material may modify the toxic and carcinogenic potency of the particles. Furthermore, the so-called BET surface measured by N2 adsorption may not represent the toxicological relevant surface area. (Abstract truncated)