Project at a Glance

Title: New approach for detecting health hazards of NO2 inhalation: Period: April 29, 1981-October 31, 1982

Principal Investigator / Author(s): Richters, Arnis

Contract Number: A0-106-32

Research Program Area: Health & Exposure

Topic Areas: Health Effects of Air Pollution


Studies were carried out to determine if the effects of ambient level NO2 inhalation which lead to facilitation of blood borne cancer cell metastasis to the lungs, were dependent upon the NO2 exposure conditions. In all of our previous studies the pollutant exposures varied and were carried out before the introduction into the blood stream of cancer cells. In contrast, all experiments described in this report had the same NO2 level (-0.4 + 0.05 PPM) but the exposure length and the timing, with respect to circulating cancer cells, varied. Usually, there were three groups of animals in each experiment; filtered air control, NO2 exposed and ambient air group. The ambient air group was always kept in vivarium room air while the clean air control and the NO2 exposed groups were kept in special environmental chambers within their respective environments The NO2 levels were monitored continuously. B16 mouse melanoma cells were infused intravenously into the blood of animals before or after an appropriate exposure and the incidence of metastases development, determined three weeks later, permitted the assessment of the effects.

The results have indicated that ambient level NO2 exposures for ten to 12 weeks facilitate blood borne cancer cell metastasis to the lungs and indicate harmful NO2action. The NO2 exposures for three weeks, while cancer cells are in circulation, or for six weeks before cancer cell infusion, did not show facilitation of metastasis. The introduction of clean air periods between NO2 exposure episodes to some degree reduced the NO2 effects but only in the less sensitive portion of the test animals. Importantly, the polluted ambient air inhalation for as short a period as six weeks, resulted in facilitation of metastasis.

These findings support our earlier studies and indicate that certain ambient level NO2 and polluted ambient air exposures are harmful and play a role in facilitation of blood borne cancer cell metastasis to the lungs. These findings have a direct bearing on the human cancer problem since the probability exists that one in four individuals will develop cancer and most of the cancer patients have circulating cancer cells. Of primary importance is the fact that urban communities are exposed to similar levels of air pollutants almost daily. Thus the observations discussed here provide strong support for the need of improved air quality in urban areas and the need for studies to identify other air pollutants which may have the same action. The mechanisms involved remain unclear and need to be investigated. in addition, the findings should assist in establishing the rationale for setting air quality standards.

For questions regarding this research project, including available data and progress status, contact: Research Division staff at (916) 445-0753

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