Interpretation of Nasal Swab Measurements Following Suspected Releases of Actinide Aerosols
For radionuclides such as plutonium and americium, detection of removable activity in the nose (i.e., nasal swab measurements) are frequently used to determine whether follow-up bioassay measurements are warranted following a potential intake. For this paper, the authors analyzed 429 nasal swab measurements taken following incidents or suspicious circumstances (such as an air monitor alarming) at Los Alamos National Laboratory (LANL) for which the dose was later evaluated using in vitro bioassay. Nasal swab measurements were found to be very poor predictors of dose and should not be used as such in the field. However, nasal swab measurements can be indicative of whether a reliably detectable committed effective dose (CED) occurred. About 14% of nasal swab measurements between 1.25 and 16.7 Bq corresponded to CEDs greater than 1 mSv, so in general, positive nasal swabs always indicate that follow-up bioassay should be performed (positive nasal swabs less than 1.25 Bq are considered separately). This probability increased significantly for nasal swabs greater than 16.7 Bq. Only about 3% of nasal swabs with no detectable activity (NDA) corresponded to reliably detectable CEDs. A nasal swab with NDA is therefore necessary, but not sufficient, to negate the need for a follow-up bioassay if it was collected following other workplace indicators of a potential intake.