Chronic effects on the respiratory tract of hamsters, mice and rats after long‐term inhalation of high concentrations of filtered and unfiltered diesel engine emissions

Abstract

A long-term exposure study with hamsters, mice and rats inhaling filtered and unfiltered diesel engine exhaust was carried out to investigate effects of chronic toxicity and, predominantly, carcinogenicity in the respiratory tract. The level of diesel exhaust in the exposure chambers corresponded to a concentration close to 4 mg m-3 in the unfiltered diesel exhaust. Satellite groups of animals were additionally treated with BaP, DBahA or nitrosamines in order to check for syncarcinogenic effects. In hamsters and rats, alveolar lung clearance and mechanical lung function tests as well as biochemical and cytological measurements in lung lavage fluids showed significant changes only after exposure to unfiltered diesel exhaust and, predominantly, in rats. No lung tumors were found in hamsters. Spontaneous tumor rates occurred in mice and both types of diesel exhaust increased the incidence of adenocarcinomas in the lungs. In rats, only the unfiltered diesel exhaust caused a lung tumor incidence. It amounted to 16% with no tumors in the controls. The heavy load of particulate matter in the lungs of rats was caused by an exposure-related impairment of the alveolar lung clearance and may have been instrumental in the induction of squamous cell tumors. However, an effect of particle-associated PAH cannot be excluded. Syncarcinogenic effects of diesel exhaust after initial carcinogen treatment were found only in the respiratory tract of rats.

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).…”

“…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) …”

Health hazard evaluation report: HETA-90-088-2110, Yellow Freight System, Inc., Columbus, Ohio, Maybrook, New York.

“…The studies in rats and mice confirmed the association between induction of lung tumors and exposure to whole diesel exhaust, and especially the particulate phase. 13,14,15,16,17,18 Several recent human epidemiology studies also consistently suggested an association between occupational exposure to whole diesel exhaust and lung cancer. 19,20,21,22,23 The most recent and thorough epidemiological studies were done by Garshick, et al 20,21 in railroad workers.…”

A perspective on the potential development of environmentally acceptable light-duty diesel vehicles.

“…In the late 1970s and 1980s, there was a substantial international effort to chemically characterize the PAH in gasoline and diesel vehicle exhaust and to test the effect of these emissions on microorganisms, cells, and animals. This effort became concentrated on diesel vehicles because of much higher PAH and particulate emissions (4), which were found to cause cancer in some laboratory animals (5). This process culminated in the classification of diesel particulate as a probable carcinogen (4) and in regulations to reduce diesel particulate emissions in the United States (6).…”