B.L. Pool

Inhibition of Chemical Carcinogenesis

The inhibition of chemical carcinogenesis by specific antidotes has to be considered a long-term objective in cancer prevention. Taking three examples, the possibilites and limitations of such inhibition are elucidated.

Effect of long-term inhalation of N-nitroso-dimethyl amine (NDMA) and SO2/NOx in rats

This report focusses on preliminary results of a long-term inhalation assay with N-nitroso-dimethylamine (NDMA) at low concentrations. Chronic inhalation of 1 ppm of NDMA (4 h/day, 5 days/week) was found to be toxic in rats and diminished life expectancy by about 8 months compared to the control group. Mostly tumors of the nasal region (25/36) were observed. Inhalation of 0.2 ppm of NDMA lead to a high tumor yield in rats (20/36). At a concentration of 0.04 ppm (= 0.12 mg/m3 in air) 3 tumors of the nasal region have been found until now. In addition, a combined inhalation study of other air pollutants SO2 or NOx together with NDMA at the 0.2 ppm level is being performed. Tumors of the nasal region have been observed in the groups with SO2 + NDMA and NOx + NDMA as well as with NDMA alone. Differences in tumor response of the groups treated with NDMA alone or in combination with SO2/NOx cannot be assessed yet. The additional treatment with the air pollutants SO2 or NOx has not affected the body weight gain or any other observable parameters of the life quality of the rats.

Toxic and Genotoxic Effects of SO2 or NOx Alone and in Combination with Carcinogenic N—Nitrosamines

The influence of common air pollutants SO2 or NOx on the genesis of tumors induced by chemical carcinogens has not yet been studied extensively. We may envisage the gases to act either inhibitory, additively or synergistically during the induction of tumors by carcinogens. Preliminary studies did show that lifelong SO2 inhalation in combination with benzo(a)pyrene yielded an increased tumor rate in experimental animals (1). Studies on the interaction between SO2 or NOx with carcinogenic N-nitrosamines however, have not been reported. Therefore, we are performing a study on the interplay between SO2 or NOx and carcinogens at various levels, including in vitro studies, as well as a long term bioassay, which is still underway.

Carcinogenic Risk Factors and Cancer Prevention

The assumption that cancer in human beings is largely caused and triggered by environmental factors is undisputed today. Such carcinogenic factors include chemical substances, high-energy physical rays and viruses. Recognition and determination of such factors is the precondition for preventive measures.

Krebsauslösende Faktoren und Krebsprävention

Die Annahme, das Krebs beim Menschen in weitgehendem Mase durch Faktoren in seiner Umwelt bedingt und ausgelost wird, ist heute unbestritten. Zu solchen krebserzeugenden Faktoren (Karzinogenen) sind chemische Substanzen, energiereiche physikalische Strahlen und Viren zu zahlen. Die Erkennung und Bestimmung solcher Faktoren ist die Voraussetzung fur praventivmedizinische Masnahmen.