In theory, but keep in mind that ozone is everywhere in small quantities. While it can be carcinogenic, it's about the concentrations. Also when it's injected into the tank, it breaks down into the water and isn't released as ozone. Also there is usually a lot of gas exchange in our houses, especially around our tanks, so that helps.
If ozone is carcinogenic, I worry more about those ionic breeze machines than I do about an ozonizer on my aquarium, since my friends have had the ionic breeze things filling their places with ozonized air, and I've been breathing it in.... so yeah... ::shrug::