Interestingly, previous investigation into the signalling events involved in how PAH pollutants regulate chemokine gene expression in airway epithelial cells demonstrated that different AHR ligands, as found on DEP particles, can induce CXCL8 and CCL5 but that only CXCL8 responses were dependent on the transcription factor NF-kB49. Here, CCL5 is linked to pulmonary arterial hypertension.