To find a practical biomonitoring method for researchers exposed to nanoparticles causing oxidative stress. In a continuation of a study in 2016-2018, biological samples (plasma, urine and exhaled breath condensate EBC) were collected in 2019-2020 from 43 researchers (13.8 ± 3.0 years of exposure) and 45 controls. Antioxidant status was assessed using glutathione (GSH) and ferric-reducing antioxidant power, while oxidative stress was measured as thiobarbituric acid reactive substances, all using spectrophotometric methods. Researchers' personal nanoparticle exposure was monitored. Plasma GSH was elevated in researchers both before and after exposure (p < 0.01); postexposure plasma GSH correlated with nanoparticle exposure, and GSH in EBC increased. The results suggest adaptation to chronic exposure to nanoparticles, as monitored by plasma and EBC GSH.