A spectrophotometric method for the quantitation of diesel exhaust particles in guinea pig lung

Particulate material in diesel engine exhaust deposits in the lungs of exposed animals. A technique for measuring the amount of soot in the lungs would be useful for determining the rates of the deposition and clearance of the submicron particles. The paper describes the use of light extinction for quantitating diesel particles in aqueous suspension. Particles collected by electrostatic precipitation and finely suspended in 0.01 N NaOH by sonication strongly absorb visible light. The extinction of light at 750 nm is proportional to the mass concentration of particles, with an extinction coefficient of 28 +/- 1 cm2 mg-1. Lungs from guinea pigs exposed to dilute diesel exhaust were dried and digested in potassium hydroxide and ethanol. The insoluble particles were centrifuged and resuspended in water by sonication. The optical density of the suspension was compared to that of suspensions made from lungs of animals not exposed to diesel exhaust, with or without known amounts of particulate added at the beginning of digestion. A concentration-dependent increase in the total amount of particles per lung was found for guinea pigs exposed to 0, 269, 813 and 1530 micrograms m-3 diesel particles for 6 months.