Durability tests were made on three types of catalytic converters for automotive exhaust gas. A 10, 000 km driving test was given to nine test cars equipped with a market-sold catalyst for oxidation of CO and HC. The average purification efficiencies of Pt catalyst and Pd-Cr catalyst were found to be 95.0% for CO and 76.2% for HC, and 60.9% for CO and 60.2% for HC, respectively.
Cu catalyst, however, showed the worst efficiency, 60.0% for CO and 51.0% for HC, and the decrease of catalyst weight. The property changes of the catalyst between before and after the use were examined by X-ray diffraction, fluorescent X-ray, BET, differential thermoanalysis, and a hardness meter. The hardness decreased to 1/4 of the fresh, which caused attrition to release the catalyst to the air. The detorioration of the catalytic activity seemed to depend on the crystal structure changes, the decrease of the specific surface area, and adsorption of Pb.

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Rubber particles emitted from automobile tire tread by abrasion have been measured in the Iikura expressway tunnel, at the Tengenji crossing of roads, on the roof of buildings near the expressway and the crossing, and in the area far from roads.
The concentration of airborne rubber particles in the tunnel was 4.6-7.8μg/m³, which corresponds to 3.6-7.8% of the total airborne particulate matters collected. At the crossing, the concentration of airborne rubber particles was 2.4μg/m³ corresponding to 2.1% of the total particulate matters. On the roof of the buildings near the expressway and the crossing, the concentrations of rubber particles were significantly lower than those of the grounds.
In the area far apart from roads, airborne rubber particles were only 0.17% of the total particulate matters collected.
The concentration of rubber particles in unsuspended particulate matters in the tunnel was about 3% of the total unsuspended particulate matters collected.
Since zinc oxide (ZnO) is contained in tire tread compounds as a vulcanisation activator, zinc was measured at each sampling site to evaluate the contributions of zinc in the rubber particles to the total zinc concentrations.

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Pulse doses of soot abtained from heavy oil combustion were injected subcutaneously to infant ICR/JCL mice, and the animals were observed for 30 months.
Total tumor incidences in male of mice injected with soot or benzo (a) pyrene were statistically highly significant (X₂ =7.85-12.24, p<0.01-0.001) as compared with that of vehicle control, but those in female treated with soot or benzo (a) pyrene were contradictory. Tumors were found mainly in the lung, lymphoreticular tissue, and liver in both sexes. In the experimental groups, average survivals in male bearing pulmonary tumor, leukemia or liver tumor were shorter than that in the control, but those findings in female were also contradictory.

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