Cytotoxicity of incinerator fly ash on alveolar macrophages

Fly ash samples were collected from the electrostatic precipitator of a municipal incinerator in Hong Kong. The physical and chemical properties of fly ash particles of a diameter smaller than 10 mu m were studied by a scanning electron microscope incorporated with an X-ray energy dispersive microanalyzer, atomic absorption spectrophotometer, and X-ray powder diffractometer. The particles were very heterogeneous in size and shape and had high levels of trace metals (Cd, Cr, Cu, Fe, Mn, Ni, Pb, and Zn). The cytotoxicity of fly ash particles was assessed using an in vitro culture assay of rat alveolar macrophages. It was found that the particles damaged the surface morphology of the cell, decreased the cell viability and phagocytic activity, and increased the release of cytoplasmic (lactate dehydrogenase) and lysosomal ( beta -glucuronidase) marker enzymes into the culture medium. No hemolytic effect could be measured on the rat red blood cells, indicating that the plasma membrane is not the target site of the incinerator fly ash.