Research Program Area: Health & Exposure
The main objective of the study was to determine if an adverse nitrogen dioxide effect on host could be detected by studying the host's immune system and the development and the progression of a spontaneously occurring lymphoma, in a mouse model, which very closely resembles human malignancy. The nitrogen dioxide level was 0.25 parts per million. Following five varying exposure periods, equal numbers of age matched control and exposed animals were studied utilizing histopathological and immunological methods. A ten-month survival study was also carried out. The major findings were as follows: 1) significantly more exposed animals survived in the survival study: 2) the control animals showed more extensive lymphoma process following varying exposure periods; 3) the exposed animals showed significantly lower percentages of total spleen T lymphocytes and two subpopulations, following 37 and 181 days of exposure. Taken together these findings indicate that exposure to 0.25 ppm NO2 delayed the development of fulminant lymphoma and had an adverse effect on T lymphocytes. Therefore, in this study the NO2 exposure did not enhance the advancement of malignancy, it delayed it. However, this was due to the unique nature of this malignancy which originates among the major class of cells in defense system - the T lymphocytes. This delay should not be mistaken as being beneficial to the host. In fact, it is quite the opposite, the NO2 exposure has affected important lymphocyte subtypes and has prolonged and aggravated the disease process. It should be emphasized that the major cells of the immune system were affected by NO2 levels which are frequently encountered in many urban environments and one has to be concerned about similar effects occurring in human urban populations.
For questions regarding this research project, including available data and progress status, contact: Research Division staff at (916) 445-0753
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