Association between Waste Management and Cancer in Companion Animals

BACKGROUND: Increased cancer rates have been documented in people residing in areas around Naples characterized by illegal dumping and incineration of waste. HYPOTHESIS: Risk of cancer in dogs and cats is associated with waste management. ANIMALS: Four hundred and fifty-three dogs and cats with cancer and 1,554 cancer-free animals. METHODS: Hospital-based case-control study in Naples (low danger) and nearby cities having a history of illegal waste dumping (high danger). Odds ratio (OR) between high- and low-danger areas was calculated for all tumors and various malignancies in dogs and cats. RESULTS: An increased risk for cancer development was identified in dogs but not in cats residing in high-danger areas (OR: 1.55; 95% confidence interval: 1.18-2.03; P < .01). A 2.39-fold increased risk of lymphoma (P < .01) accounted for the greater tumor frequency in dogs residing in high-danger areas. The risk of mast cell tumor and mammary cancer did not differ in dogs residing in high- or low-danger areas. CONCLUSIONS AND CLINICAL IMPORTANCE: Waste emission from illegal dumping sites increases cancer risk in dogs residing in high-danger areas. An increased prevalence of lymphoma has been previously recognized in humans living close to illegal waste dumps. Thus, epidemiological studies of spontaneous tumors in dogs might suggest a role for environmental factors in canine and human carcinogenesis and can predict health hazards for humans