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The relative toxicity of extracted and fractionated diesel engine emission material was assessed with two in virro mammalian cell culture systems, continously maintained Balb/c 3T3 cells and freshly-isolated baboon peripheral blood lymphocytes. Particulate emission material from a two-stroke cycle and a four-stroke cycle diesel engine was collected on filters and then solvent extracted. The neutral material was fractionated chromatographically after an initial chemical fractionation of the emission material into acidic, neutral and basic fractions. Balb/c 3T3 cells treated with chemically and chromatographically-differentiated fractions from both the two-stroke cycle and the four-stroke cycle diesel engines had different toxicities on a concentration dependent (pg m1-I) basis. Fractions from the four-stroke cycle engine showed greater toxicity than those from the two-stroke cycle engine. Toxicity comparisons were made on the basis of cloning efficiency measurements (indicative of effects on reproductive integrity) 8 days after a 72 h treatment interval, and on the basis of DNA, RNA and protein precursor incorporation rates (biochemical indices) during or immediately after 72 h of treatment. The Balb/c 3T3 system results were supported by similar results obtained when freshly isolated baboon peripheral blood lymphocytes were mitogen (concanavilin A) stimulated in the presence of the various fractions. The results in the in vitro lymphocyte system indicate a potential for altered immune defense capability if the cells were to be exposed to the fractions in vivo.

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