Genotoxic effects of carbon black particles, diesel exhaust particles, andurban air particulates and their extracts on a human alveolar epithelial cell line (A549) and a human monocytic cell line (THP-1)

The possible genotoxicity of small particulate matter has been under invest igation for the last 10 years. Diesel exhaust particles (DEP) are considere d as "probably carcinogenic" (IARC group 2A) and a number of studies show g enotoxic effects of urban particulate matter (UPM). Carbon black (CB) is ca rcinogenic in rats. In this study the cytotoxic and genotoxic potency of th ese three particle types was investigated by exposing human cells (A549 and THP-1 cell lines) in vitro to CB, DEP (SRM 1650, NIST), and UPM (SRM 1648, NIST) for 48 hr. Cytotoxicity was assessed using the AlamarBlue assay, whe reas genotoxicity was assessed using the single-cell gel electrophoresis (c omet assay). The particles were characterized with regard to their mean dia meter in tissue culture medium (CB 100 nm, DEP 400 nm, UPM 2 mum), their to tal carbon content (CB 99%, DEP 85%, UPM 15%), and their acid-soluble metal composition (UPM much greater than CB similar to DEP). The concentrations ranged from 16 ng/ml to 16 mug/ml for cytotoxicity tests and from 16 ng/ml to 1.6 mug/ml for genotoxicity tests. In both assays, paraquat was used as a reference chemical. The CB, DEP, and UPM particles showed no significant cytotoxicity. However, all three particles were able to cause significant D NA damage, although to a different extent in the two cell lines. The genoto xicity of washed particles and dichloromethane extracts was also investigat ed. In THP-1 cells CB washed particles and DEP extracts caused significant DNA damage. This difference in effect may be related to differences in size , structure, and composition of the particles. These results suggest that C B, DEP, and UPM are able to cause DNA damage and, therefore, may contribute to the causation of lung cancer. More detailed studies on influence of siz e, structure, and composition of the particles are needed. (C) 2001 Wiley-L iss, Inc.