Pilot cross-sectional study for potential fibrogenic risk assessment in real multiwalled carbon nanotube aerosol exposure at the workplaces

Abstract

Aim. To assess the potential fibrogenic risk of real occupational exposure to multi-walled carbon nanotubes (MWCNT). Methods. The study was conducted at 2 MWCNT-producing enterprises with the same reactor type. 11 employees who had more than 1 year-long contact with MWCNT aerosol were included in the exposure group, the control group consisted of 14 people. Elemental carbon level and MWCNT presence were evaluated in workplace air samples by transmission electron microscopy. Blood and induced sputum samples were obtained from employees, transforming growth factor beta 1 (TGFβ 1), KL-6 glycoprotein and osteopontin levels were evaluated. To assess the relationship between MWCNT exposure and biomarker levels (age, gender, smoking were chosen as cofounders), generalized linear models including main effects and paired interactions were created. The regression coefficients confidence intervals were refined by bootstrap analysis. Results. Time-weighted average respirable MWCNT fraction was up to 6.11 mg/m 3. Transmission electron microscopy showed the presence of MWCNT agglomerates sized 0.5-10 μm in all air samples. The levels of TGFβ 1 in serum were significantly dependent on exposure to MWCNTs (b=10.47, 95% BCa=1.18-51.75), the KL-6 glycoprotein levels in induced sputum was significantly higher in exposure group (b=235.9, 95% BCa=21.2-482) compared to control group. Osteopontin did not prove itself as an informative indicator. Conclusion. Gained data suggest that MWCNT aerosol exposure at workplace may lead to fibrogenic biomarkers level changes in serum and induced sputum samples. Control measures for MWCNT aerosol levels and medical surveillance for employees should be introduced in MWCNT-producing and applying facilities.