Figure 4

Lung parenchymal cell proliferation rates (BrdU) in particulate-exposed rats and corresponding controls at 24 hrs, 1 week, 1 month and 3 months postexposure (pe). Values given are means ± S.D. Small but significant transient increases in lung cell proliferation indices were measured in the carbonyl iron, Pigment A TiO₂-exposed, and quartz-exposed rats at 24 hrs but were not sustained. Significantly larger increases in cell proliferation indices were measured in the lungs of quartz exposed rats through 3 months postexposure. *p < 0.05