Pets that spend significant time in basements may have elevated lung-cancer risk. Veterinary research is limited but suggests similar mechanisms to human exposure. Most household pets are at lower risk than humans on lower floors.
More detail
Radon's biological mechanism (alpha-particle damage to lung tissue from inhaled radon-daughter products) applies to mammals generally. Veterinary epidemiology on radon is sparse because pets typically have shorter lifespans than the multi-decade exposure window required to detect a clear dose-response signal in humans. Pets that spend the majority of their day in a basement, particularly small dogs and cats whose breathing zone is closer to the floor, are at the highest pet-side risk. Most outdoor or upper-floor-sleeping pets see negligible radon exposure. Indoor cats sleeping in finished basement rooms are probably the highest-exposure household pet; large dogs that nap at floor level in conditioned basement spaces are second. Mitigation reduces pet exposure proportionally to human exposure. Cincinnati pet-exposure context: small dogs and indoor cats spending most of their time in basement living spaces are the highest-risk household pets. Veterinary studies on radon-related cancer in pets are limited but suggest similar mechanisms to human exposure. Mitigating the human exposure also mitigates the pet exposure. No specific pet-focused testing protocol is needed; the household-wide reading is what matters.