The potential carcinogenic effect of inhaled automobile exhaust emissions was examined in rodents. Both rats and hamsters were exposed to the emissions from (1) a gasoline engine, (2) a gasoline engine fitted with a three-way catalytic converter, (3) a diesel engine and (4) a diesel engine with particle filtration. Exposures were for 16 hours per day, 5 days per week, for 2 years. All hamsters were sacrificed at the end of the 2-year exposure period, whereas the rats surviving after 2 years of exposure were maintained for a further 6-month observation period without additional exposure to emissions. Some of the hamsters in each treatment group were pretreated with diethylnitrosamine to induce respiratory tract tumours. No statistically significant changes were seen in the incidence of respiratory tract tumours in emission-exposed hamsters compared to controls. This lack of a treatment-related effect was seen in both the nitrosamine pretreated and the non-pretreated hamsters. There was no increase in the incidence of lung tumours in rats exposed to filtered diesel exhaust or to the exhaust from the gasoline or gasoline-catalyst engines. There was a statistically significant increase in the incidence of lung tumours in rats exposed to diesel engine emissions compared to controls. A clear dose response was evident in both males and females, although the incidence of lung tumours was markedly higher in females (96% in rats surviving beyond 2 years) than in males (44% in rats surviving beyond 2 years). An increased incidence of lung tumours was observed only in rats exposed to mean concentrations of diesel soot particles of either 2200 or 6600 micrograms/m3.(ABSTRACT TRUNCATED AT 250 WORDS)

Blood samples from rats and hamsters exposed to automotive engine exhausts in the Committee of Common Market Automobile Constructors long-term inhalation study at Battelle-Geneva were analysed for the levels of 2-hydroxyethylvaline (HOEtVal) and 2-hydroxypropylvaline (HOPrVal) in hemoglobin (Hb). These adducts to the N-terminus of the Hb chains were determined by gas chromatography-mass spectrometry of derivatives obtained by a modified Edman degradation that specifically cleaves off alkylated N-terminal amino acids (valine in Hb). The adduct levels found correspond to the metabolic conversion of about 5-10% of inhaled ethene and propene to ethylene oxide and propylene oxide, respectively, in agreement with results from earlier studies on mice inhaling radio-labelled alkenes. It is concluded that the alkenes, via epoxides, are the main sources of the observed HOEtVal and HOPrVal. From calculated doses and estimates of genotoxic potency the contribution from ethene in urban air to human cancer risk is discussed.

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The combined techniques of light microscopy, scanning (SEM) and transmission (TEM) electron microscopy were used for the first time to study the structure of unicameral lungs of a Tegu lizard (Tupinambis nigropunctatus). The lungs are prolate spheroid bags with blood supplied by superficial branches of a dorsal pulmonary artery and returned by diffuse, more deeply located veins. The primary bronchus enters the medial aspect near the apex of the lung. The lung wall is composed of trabeculae: (1) arranged in a faviform pattern, (2) forming individual faveoli (gas exchange chambers) which appear deepest in the cranial one-half of the lung, (3) all of which have a smooth muscle core overlain by either a ciliated or nonciliated epithelium. A ciliated epithelium lines the luminal surfaces of the large primary trabeculae and parts of smaller secondary trabeculae; it is composed of cone-shaped cells with ciliated-microvillous surfaces, and of columnar serous secreting cells. Nonciliated epithelium covers the luminal surface of portions of some secondary trabeculae, abluminal surfaces of primary and secondary trabeculae and all surfaces of the small tertiary trabeculae forming the faveoli. The nonciliated epithelium overlies an extensive superficial capillary network. The blood-gas barrier (0.7-1.0 μm thick) is composed of a thin cytoplasmic flange of Type I pneumonocytes, a thick homogeneous basal lamina and an attenuated endothelial cytoplasm. Numerous surfactant-producing Type II pneumonocytes are closely associated with the Type I pneumonocytes. The nonrespiratory ciliated epithelium may function in humidification of air and clearing of the lungs.

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