In a scenario of repeated (annual) CT screening, the lifetime attributable risk of lung cancer and major cancers the most negative scenario is 5.5 and 8.1 per 10 000 people screened, respectively. So the risk increase is about 0.05 to 0.08%. Since these numbers are statisticakll significant, you can consider them non-negligible. But when you weight those numbers against the potential benefits in terms of reduction of CVD events, I think the decision whether to do a scan or not is quite in favour of having it done.