bacterial lipopolysaccharide plus interferon-gamma (LPS/IFN-γ), or phorbol 12-myristate 13-acetate (PMA) or yeast Zymosan A fragments (Zymosan). The urban dust EHC-93

refers SGI-1776 to material collected from the baghouse filters of the Environmental Health Centre (EHC) building in Ottawa, ON, Canada and prepared as described previously (Vincent et al., 1997). Standard Reference Materials, SRM-1648 (urban particulate matter, St. Louis), SRM-1649 (urban dust/organics, Washington), SRM-1879 (respirable cristobalite, SiO2) and SRM-154b (titanium dioxide, TiO2) were obtained from the National Institute of Standards and Technology (Gaithersburg, MD, USA) and used as supplied, except for TiO2, which was subjected to three washes with methanol, followed by three washes with phosphate buffered saline (Vincent et al., 1997). Fine particulate matter from Vermillion, Ohio (VERP), with an aerodynamic size cut-off of 2.5 μm (PM2.5) collected on hi-vol filters in 1992 was recovered by sonication and lyophilization (Vincent et al., 1997). The metal oxides, iron II/III oxide (<5 μm diameter; 98%

purity), iron III oxide (<5 μm; 99+%), copper II oxide (<5 μm; 99+%) and nickel II oxide (<10 μm; 76–77%), were obtained Hormones antagonist from Sigma–Aldrich Co., St. Louis, MO, USA. The particulates including metal oxides were selected given that they cover a wide range of occupational limits for airborne exposures (ACGIH, 2010, NIOSH, 2007, Ontario Ministry of Labour, Sclareol 2010, OSHA, 2006 and Québec Gazette Officielle, 2009; Table 1). For aqueous extraction, one g of EHC-93 was suspended in 5 ml of deionized sterile water (>16 MOhms resistivity), sonicated on ice for 20 min, and centrifuged at 500g, 10 min. The extract was collected and the insoluble material was resuspended in 5 ml of water. This process was repeated twice and

pooled supernatant was centrifuged at 900g for 3.5 h. The pellet was combined with the previous insoluble fraction. The aqueous extract was further filtered through a 0.2 μm nylon filter. The filtrate was eluted with 5 ml of methanol and the eluate was pooled with the aqueous extract. The aqueous extract and the water-insoluble pellet were subsequently frozen at −80 °C and lyophilized. The native EHC-93 material is hereafter referred to as EHC-93tot, and the soluble and insoluble fraction, EHC-93sol and EHC-93insol, respectively. The water-leached EHC-93insol particles and the water-soluble leachate EHC-93sol had mass recovery of 97%, with 80% being recovered as solid leached particles and 17% as soluble material ( Vincent et al., 2001). Stock suspensions of particulate materials including metal oxides were prepared at 10 mg/ml in 0.025% Tween-80 and 0.9% NaCl.