**RMSE = 5.89**

The evaluation of this model demonstrates that only the chemical factors are very high predictors of the level of fine particulate matter. A model built with these parameters provides a significantly lower RMSE and higher r than the traffic and meteorology based models. This outcome was expected as the levels of anthropogenic PM2.5 that are directly related to the emission of other air pollutants, such as a number of different contaminants that come from the same sources. It can be concluded from this analysis that selecting some low-cost chemical recordings should improve the prediction accuracy of the affordable models.
