Environmental dust exposure and lung cancer in dogs: evidence for a link

Background. Primary lung cancer in dogs has been putatively related to urban living and air pollution on epidemiologic basis, but a causative association has not been definitely shown. Furthermore, the relationship between the deposition of black dust matter in lungs (anthracosis) and primary pulmonary carcinoma has not been investigated in dogs. Methods. Amount, type and birefringence of pulmonary anthracosis were histologically assessed in a retrospective study by examining 35 dogs with primary epithelial lung cancer and 160 controls; the odd ratio (OR) was calculated for dogs with primary lung cancer. The same factors were analyzed to identify an association between type of lung tumor, histological grade, and TNM stage . Results. Papillary adenocarcinoma was most commonly diagnosed (45.7%). The majority of tumors was of histological grade 2, and the lung cancer was more often localized (clinical stage I). An increased risk for lung cancer was observed in dogs with higher amounts of anthracosis (OR: 2.20, CI 95%: 1.27-3.81; p < 0.01). Type of anthracosis and its birefringence were not related to lung cancer. Tumor type, histological grade, and TNM stage were not associated with amount, type and birefringence of anthracosis. Conclusions and Clinical Relevance. Anthracosis due to inhalation of polluted air contributes to lung cancer development in dogs. Further studies are required to characterize the specific environmental contaminants responsible for lung carcinogenesis in this species