Figure 3

IL-6 produced by RAW 264.7 macrophages after 16 hours incubation with the PM samples. Each bar shows mean ± standard deviation of two exposures in triplicate. Data was analyzed using multiple linear regression. * Statistically significant different from no concentration-response p < 0.05. × Sample excluded because of high endotoxin level. · Highest concentration not tested (not enough sample).