We chose two markers of DNA damage signalling activation, phosphorylation of Checkpoint kinase 1 at Ser317 (pChk1) and H2A histone family member X at Ser139 (pH2AX), as both have previously been shown to be activated in response to PAH and PM exposures [Niziolek‐Kierecka et al., 2012; Jarvis et al., 2013]. This evidence concerns the gene H2AX and pulmonary arterial hypertension.