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Project Status: complete

Report Published October 1981:

Title: New approach for detecting health hazards of NO2 inhalation: Period: 1/21/79-5/30/81

Principal Investigator / Author(s): Richters, Arnis

Contractor: University of Southern California, School of Medicine

Contract Number: A9-076-31

Research Program Area: Health & Exposure

Topic Areas: Health Effects of Air Pollution


On the basis of preliminary observations which suggested that inhalation of ambient levels of NO2 may facilitate blood borne cancer cell metastasis to the lungs, more extensive studies were undertaken to investigate this aspect further. Since increased blood borne cancer cell metastasis to lungs may reflect injury to the pulmonary microcirculation or alterations in the immune system or even both, the development of metastases could serve as a very meaningful biological indicator for harmful NO2 effects. Moreover, it would have direct relevance to human health since many humans, particularly cancer patients, harbor cancer cells in their circulation. Experiments were designed, using a mouse model, to test ambient level NO2 inhalation effects on the frequency of blood borne cancer cell metastasis development. To date, five experiments have been carried out, two of which were preliminary studies and the other three were major experiments. The two preliminary experiments (M125, M130) were intended to finalize the methodologies and involved 26 and 40 animals respectively and both were carried out at 0.8 ppm NO2 exposure. The three major experiments (Ml28, M137, Ml38) involving 270 animals were carried out at 0.8 ppm, 0.3 ppm and 0.5 ppm NO2 exposure respectively. There were three groups of animals in each experiment (filtered air control, NO2 exposed, and vivarium ambient air control) with 30 animals per group. The results have indicated that the 0.8 ppm NO2 exposed animals developed the highest frequency of melanoma nodules when compared to control animals who inhaled filtered NO2 free air. Similar results were also obtained with 0.3 ppm exposure for 12 week period but with a lower level of significance. The animals residing in ambient vivarium air also showed more melanoma nodules in their lungs than did the controls. However ,exposure for 8 weeks to 0.5 ppm did not reveal significant differences between the three groups and the latter may indicate that the length of exposure to ambient level pollutants is important. Thus, the data obtained from the major portion of this study indicates that the inhalation of ambient levels of NO2 or ambient vivarium air, under the described experimental conditions, facilitates blood borne cancer cell metastasis to the lungs. Further studies are warranted since other exposure conditions need to be evaluated and the question arises as to whether similar events may take place in human urban populations.


For questions regarding this research project, including available data and progress status, contact: Heather Choi at (916) 322-3893

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