Elsevier

Toxicology

Volume 74, Issues 2–3, September 1992, Pages 173-184
Toxicology

Combined exposure to NO2, O3 and H2SO4-aerosol and lung tumor formation in rats

https://doi.org/10.1016/0300-483X(92)90137-4Get rights and content

Abstract

The promoting effects of a combined exposure to two pollutants (NO2, O3 or H2SO4-aerosol) at near ambient levels on lung tumorigenesis induced by N-bis(2-hydroxypropyl) nitrosamine (BHPN) were investigated in male Wistar rats. The rats were given a single intraperitoneal injection of BHPN (0.5 g per kg body wt.) at 6 weeks of age. They then were exposed to clean air, 0.05 ppm O3 (mean concentration for 10 h/day; 0.1 ppm peak concentration), 0.05 ppm O3 (mean concentration for 10 h/day; 0.1 ppm peak concentration) + 0.4 ppm NO2 or 0.4 ppm NO2 + 1 mg/m3 of H2SO4-aerosol for 13 months and were then maintained in a clean room for another 11 months. Room control animals were kept after injection of BHPN in a clean room for 24 months. The incidence of primary lung tumors in rats exposed to 0.05 ppm O3, 0.05 ppm O3 + 0.4 ppm NO2 and 0.4 ppm NO2 + 1 mg/m3 of H2SO4-aerosol with BHPN treatment was 8.3% (3 out of 36 rats), 13.9% (5 out of 36 rats) and 8.3% (3 out of 36 rats), respectively. The tumors were adenomas and adenocarcinomas. The incidence of adenomas was 2.8% (1 out of 36 rats) in the O3 alone group, 11% (4 out of 36 rats) in O3 + NO2 group and 5.6% (2 out of 36 rats) in NO2 + H2SO4 group. The incidence of adenocarcinomas was 5.6% (2 out of 36 rats) in the O3 group, 2.8% (1 out of 36 rats) in O3 + NO2 group and 2.8% (1 out of 36 rats) in NO2 + H2SO4 group. No lung tumors were found in the rats exposed to clean air with BHPN treatment and in animals not given BHPN but exposed to each air pollutant. The difference in tumor incidence between the clean air group with BHPN and the O3 + NO2 group with BHPN was statistically significant. The results show that exposure to O3 alone enhances tumor development and that the combined exposure to O3 or H2SO4 with NO2 produces an additional increase in incidence of lung tumor, respectively. The incidence of slight-moderate to marked alveolar cell hyperplasia in the groups exposed to each air pollutant with BHPN treatment was higher than that in the groups exposed to clean air with BHPN. Exposure to each air pollutant had no effect on the development of bronchiolar mucosal hyperplasia in lungs of rats treated with BHPN. These results suggest that the exposure to O3 + NO2 or NO2 + H2SO4 even at ambient levels of each pollutant may have a synergistic action as a tumor promoter and that free radical generation and lipid peroxide production by exposure to those air pollutants may be related to lung tumor promotion.

References (35)

  • S. Moriguchi et al.

    High dietary intakes of vitamin E and cellular immune functions in rats

    J. Nutr.

    (1990)
  • M. Tsuda et al.

    Increase in the levels of N-nitrosoproline, N-nitrosothioproline and N-nitro-2-methylthioproline in human urine by cigarette smoking

    Cancer Lett.

    (1986)
  • T. Kuroishi et al.

    Cancer mortality in Japan

    Gann Monogr. Cancer Res.

    (1981)
  • W. Haenszel et al.

    Lung-cancer mortality as related to residence and smoking histories. I. White males

    J. Natl. Cancer Inst.

    (1962)
  • A. Hanai et al.

    Comparison of lung cancer incidence rates by histological type in high and low incidence countries, with reference to the limited role of smoking

    Jpn. J. Cancer Res.

    (1988)
  • K. Kubota et al.

    Effect of long-term nitrogen dioxide exposure on rat lung: Morphological observations

    Environ. Health Perspect.

    (1987)
  • R.J. Shamberger et al.

    Antioxidants and cancer. IV. Initiating activity of malonaldehyde as a carcinogen

    J. Natl. Cancer Inst.

    (1974)

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