Markers of lipid oxidative damage among office workers exposed intermittently to air pollutants including nanoTiO2 particles.

Abstract

Nanoscale titanium dioxide (nanoTiO2) is a commercially important nanomaterial used in numerous applications. Experimental studies with nanotitania have documented lung injury and inflammation, oxidative stress, and genotoxicity. Production workers in TiO2 manufacturing with a high proportion of nanoparticles and a mixture of other air pollutants, such as gases and organic aerosols, had increased markers of oxidative stress, including DNA and protein damage, as well as lipid peroxidation in their exhaled breath condensate (EBC) compared to unexposed controls. Office workers were observed to get intermittent exposures to nanoTiO2 during their process monitoring. The aim of this study was to investigate the impact of such short-term exposures on the markers of health effects in office workers relative to production workers from the same factory. Twenty-two office employees were examined. They were occupationally exposed to (nano)TiO2 aerosol during their daily visits of the production area for an average of 14±9 min/day. Median particle number concentration in office workers while in the production area was 2.32×104/cm3. About 80% of the particles were <100 nm in diameter. A panel of biomarkers of lipid oxidation, specifically malondialdehyde (MDA), 4-hydroxy-trans-hexenal (HHE), 4-hydroxy-trans-nonenal (HNE), 8-isoprostaglandin F2α (8-isoprostane), and aldehydes C6-C12, were studied in the EBC and urine of office workers and 14 unexposed controls. Nine markers of lipid oxidation were elevated in the EBC of office employees relative to controls (p<0.05); only 8-isoprostane and C11 were not increased. Significant association was found in the multivariate analysis between their employment in the TiO2 production plant and EBC markers of lipid oxidation. No association was seen with age, lifestyle factors, or environmental air contamination. The EBC markers in office employees reached about 50% of the levels measured in production workers, and the difference between production workers and office employees was highly significant (p<0.001). None of these biomarkers were elevated in urine. The approach presented here seems to be very sensitive and useful for non-invasive monitoring of employees exposed to air pollutants, including gases, organic aerosols, and nanoTiO2, and may prove useful for routine biomonitoring purposes. Among them, aldehydes C6, C8, C9, and C10 appear to be the most sensitive markers of lipid oxidation in similar occupational cohorts. One major challenge with sensitive biomonitoring techniques, however, is their non-specificity and difficulty in interpreting the meaning of their physiological values in the context of chronic disease development and damage-repair kinetics.