Tumours of the respiratory tract in rats and hamsters following chronic inhalation of engine exhaust emissions

Abstract

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)

Determination of Particulate and Unburned Hydrocarbon Emissions from Diesel Engines Fueled with Biodiesel

“…Both of them are the result of incomplete combustion of the fiiel or lubricating oil. Some recent laboratory research on rats has shown that the solid carbon, or soot, portion of diesel particulates is probably essential for initiation of tumor formation [2,3]. The associated soluble organic fraction, particularly the polynuclear aromatic hydrocarbons (PAH) and Nitro-PAH, also makes a contribution to the overall carcinogenic efiect [4].…”

Meta-analysis of rat lung tumors from lifetime inhalation of diesel exhaust.

“…Using these criteria, we identified eight chronic inhalation studies (16,(33)(34)(35)(36)(37)(38)(39). Some studies indude results from animals sacrificed at interim periods (36,37).…”

“…Some studies indude results from animals sacrificed at interim periods (36,37). The exposure concentrations and study results are summarized in Table 1, and Figure 1 illustrates data on the proportion of animals (males and females combined) with a lung tumor as a function of exposure to DEP, using the metric described below.…”

“…The null result in two strains of rats at low exposure, plus the null results in longterm bioassays of DEP-exposed mice (46) and DEP-exposed hamsters (33,36) …”

Toxicological and epidemiological evidence for health risks from inhaled engine emissions.

“…The cancer study by Brightwell et al (9) of rats and hamsters exposed to GE, mentioned above, also included limited evaluations of respiratory function (24), but no significant alterations were observed. In 1966, Hueter et al (25) reported limited measurements of the respiratory function of guinea pigs during 20 months of exposure to GE at 100 ppm CO, but found no significant effects.…”