Urban levels of air pollution modifies the progression of urethane-inducedlung tumours in mice

This paper investigates the effects of air pollution in urethane-induced lu ng tumours in mice by means of histological, morphometrical, and DNA ploidy . The experimental exposure was done in locations with different air pollut ion profiles: a polluted area (downtown Sao Paulo) and a "clean" environmen t. Swiss mice were employed and urethane (3 g/kg) was used as a carcinogeni c substance. All the animals, whether exposed or not to air pollution, were sacrificed after 6 months, and the lung lesions were analysed. The results showed a significant effect of air pollution on tumour progression, observ ed by changes in the phenotype of the tumour cells as demonstrated by morph ometry and DNA ploidy. We observed more atypical adenomas in the air pollut ion-exposed group (p = 0.02). Coherently, morphometric differences were als o detected between the two groups. Neoplasms of exposed mice exhibited an i ncrease in the nuclear fraction (p = 0.002) and in the nucleus/cytoplasm ra tio (p = 0.011), as a decrease in the stromal fraction (p < 0.001). There w as a higher risk of aneuploidy in the 6-months-of-air-pollution-exposure gr oup (relative risk: 1.58; 95% of confidence interval: 1.007 to 2.403). Thes e results indicate that urban air pollution accelerates the process of prog ression towards malignancy.