In vitro evaluation of the tumor‐promoting potential of diesel‐exhaust‐particle extracts

Diesel‐exhaust‐particle extracts at nontoxic doses were evaluated in BALB/c mouse embryo 3T3 cells and Chinese hamster V‐79 lung cells for their ability to mimic the actions of the known tumor promoter tetradecanoyl phorbol acetate (TPA). The extracts were tested in a two‐stage model of carcinogenesis in 3T3 cells and found to marginally promote the occurrence of transformed foci over a concentration range of 2–10 μg/ml. The particle extracts also caused a loss of cell‐surface fibronectin and produced an increased saturation density of 3T3 cells. Using V‐79 cells, the extracts were found to inhibit metabolic cooperation between cells. Based on these results, it was concluded that diesel‐exhaust particles contain compounds that act as weak tumor promoters.