Morphometric assessment of canine lung changes as monitoring tool for atmospheric pollution

Epidemiological and experimental studies have demonstrated that urban pollutants can cause chronic inflammation and higher tumour incidence in the dog airways. To assess if objectively measured lung changes can be proposed as a model to monitor public health risks related to air pollution, a retrospective study has been undertaken on 200 formalin fixed paraffin embedded randomly selected samples of canine lungs archived from 1975 to 2005. Histological sections stained with HE, Perls for iron and Masson trichrome for collagen, have been observed in transmitted and polarised light to assess the deposit of particulate matter and the degree of interstitial fibrosis. All parameters have been graded subjectively and also measured objectively by image analysis, and related to the dog age, sex, breed, lung changes and the epoch of sampling. Pneumoconiosis ranged from 0,02 to 1,52% of lung tissue, and was represented by black dust or grey crystalline refractile particles within macrophages in the peribronchiolar and perivascular interstitium. There was significant correlation between pneumoconiosis degree as subjectively estimated or measured by image analysis, but there was not strict association with other considered parameters. Regardless of concurrent diseases, interstitial fibrosis ranged from 0,55 to 34,95% of lung tissue, and was associated with higher deposits of crystalline dusts.