A critique of empirical emission factor models: a case study of the AP-42 model for estimating PM10 emissions from paved roads

This paper provides a critical examination of empirical emission factor models by considering one model that typifies the class: the model used to estimate PM10 emissions from paved roads. We show that the model can yield highly uncertain emission estimates because (1) it lacks a mechanistic basis, (2) its formulation is highly dependent on the data set used to derive it, and (3) the accuracy of the model is completely determined by the methods used to measure emissions. The paper also describes a method to relate model performance statistics to statements about the uncertainty in emission estimates.