Is exhaled nitric oxide a marker of air pollution effect?

Exhaled nitric oxide, measured through noninvasive breath testing with a portable device [1], is an established biomarker of airway inflammation [2]. This relies on the fact that NO is a gaseous molecule produced in a type of inflammatory response. Specifically, in humans, NO is produced from l-arginine, an α-amino acid that is used in the biosynthesis of proteins, by three enzymes called NO synthases (NOS), namely inducible NOS (iNOS), endothelial NOS and neuronal NOS [3]. In the state of inflammation, several cells, including eosinophils, use iNOS to produce NO. Due to these properties, exhaled NO has been used as a biomarker for the diagnosis and follow-up of asthma, and as a guide to therapy in asthmatics [4, 5]. It is open to debate whether F eNO is a biomarker of the effects of air pollution <http://ow.ly/ZrSke>