Cadmium and cancer: A study on canine tumours and environmental bioindicators (Sus scrofa)

Pets (i.e., dogs and cats) due to their spontaneous tumour development in shared environments with humans and their genetic, immunological, and molecular similarities, serve as valuable comparative oncology models. Heavy metals such as cadmium (Cd) have been recognized as potent environmental carcinogens with severe consequences for both human and animal health. Chronic exposure to these toxicants has been linked to various malignancies, including lung, breast, prostate, and kidney cancers. Given their persistence in ecosystems and ability to bioaccumulate, heavy metals represent a significant threat to long-term health, particularly in urban and industrialized areas. This study describes occurrence in pets of tumours affecting the skin, soft tissues, mammary glands and penis and testicles, in areas with varying levels of Cd pollution. The dataset included a population of 1764 dogs, 1057 females (480 neutered) and 707 males (204 neutered). To evaluate the potential contribution of metal pollution to tumour occurrence, a univariate and multivariate mixed-effects Poisson generalized linear model (GLM) has been developed to analyse both fixed and random effects. Areas with very high Cd pollution showed higher proportion of mammary gland tumours (PMR = 64.68; 95 %IC: 33.39-125.25), penis and testicular tumours (PMR = 19.73; 95 %IC: 2.77-141.30), soft tissue tumours (PMR = 100.55; 95 %IC: 37.19-271.79), and skin tumours (PMR = 116.23; 95 %IC: 72.67-185.94). These results suggest that environmental Cd pollution can play a role into the development of mammary gland, penis and testicular tumours, skin and soft tissue tumours in dogs. This link between environmental pollution and tumour onset underscores the value of comparative oncology in understanding cancer aetiology and improving public health strategies.