Analysis of coal tar pitch and smoke extract components and their cytotoxicity on human bronchial epithelial cells

Coal tar pitch and its smoke are considered hazardous by-products and common pollutant generated from coal industry processing. In this study, coal tar pitch and its smoke extracts were characterized by gas chromatography/mass spectrometry (GC/MS) with dimethylsulfoxide. We identified only 0.3025% of components in the total coal tar pitch using GC/MS. Among 18 identified compounds, polycyclic aromatic hydrocarbons (PAHs) has the highest relative abundance (0.19%). The remaining components were composed of monocyclic aromatic hydrocarbons, heterocyclic compounds and alkenes. In contrast, among 38 coal tar pitch smoke extract constituents that have been profiled, 87.91% were PAHs, and the remaining 12.09% were composed of monocyclic aromatic hydrocarbons, heterocyclic compounds and alkenes. The cytotoxic effect of coal tar pitch and its smoke extracts on BEAS-2B cells were also evaluated by MTT assay. BEAS-2B cells exposed to coal tar pitch showed a non dose-dependent U-shaped cytotoxicity with a dosage for maximal inhibitory of 3.75 mg/L. In contrast, BEAS-2B cells exposed to coal tar pitch smoke extracts showed a dose dependent cytotoxicity with a LC50 of 8.64 mg/L Our study demonstrated the significant different composition and cytotoxicity of coal tar pitch and its extracts, suggesting two different underlying mechanisms that are pending future investigation. (C) 2010 Elsevier B.V. All rights reserved.