Secondhand smoke, exposure to the toxins released from burning tobacco smoke exhaled by smokers, increases the risk of lung cancer. Scientists have identified over 7,000 chemicals in secondhand smoke; 69 of these can cause cancer. Emerging research also suggests associations between secondhand smoke and other malignancies, including bladder, breast, and brain cancer.
While we have known about the associations between secondhand smoke and cancer, particularly lung cancer, for decades, more recently, concerns about the effects of secondhand smoke on pets have arisen. While studies focusing on secondhand smoke exposures in pets remain rare and often inconclusive, a new article published in The Veterinary Journal demonstrates secondhand smoke can predispose dogs to bladder cancer.
Scottish terriers, as a breed, exhibit an elevated risk of canine bladder cancer. Thus, the researcher chose these dogs as a model cohort to identify environmental factors associated with bladder cancer. The researchers asked 120 Scottish terrier owners to complete questionnaires to facilitate the study. Researchers followed each dog for three years to see if bladder cancer developed, and, at enrollment, all dogs in the study were at least six years old.
Throughout the study, 32 dogs (~27%) developed bladder cancer. Notably, the analysis found bladder cancer significantly associated with dogs living with cigarette smokers. In fact, dogs exposed to secondhand smoke exhibited a six times higher risk of bladder cancer than dogs not living with a cigarette smoker.
The researchers also measured urine cotinine, an indicator of tobacco smoke exposure used to distinguish smokers from non-smokers and identify secondhand smoke exposure in non-smokers. Cotinine analysis measured quantifiable concentrations in 51 dogs, 18 of which (35.3%) developed bladder cancer. On the other hand, only 15% of dogs without quantifiable cotinine in the urine developed cancer.
The study showed two ways of assessing bladder cancer risk in dogs exposed to secondhand smoke. Living with a smoker, as determined by owner reporting, and measurable levels of cotinine in the urine both established a significant association with the development of bladder cancer. The authors conclude that secondhand smoke represents a modifiable risk factor for bladder cancer in pets.
Sources: Cancer Manag Res, Int J Environ Res Public Health (Kim), Environ Health Perspect, Int J Cancer, Vet J, Front Oncol, Int J Environ Res Public Health (Paci)
