Measurement of 220Rn in exhaled breath of Th plant workers.

The concentration of /sup 220/Rn in the exhaled breath of workers currently employed in a Th plant was measured using a double filter system. The results are expressed in terms of the equivalent activity of /sup 224/Ra freely emanating /sup 220/Rn at the mouth. Measurements performed on 176 subjects, without isolating them from day-to-day work, showed /sup 220/Rn levels having a median of 0.74 Bq, with the group consisting of sweepers and helpers showing the highest average level (1.68 Bq). Measurements performed on 15 selected workers, after isolating them from work for a minimum duration of 48 h yielded /sup 220/Rn levels which were consistently lower than those obtained in the first measurements. This is attributed to the material undergoing short term elimination from the body. It was also found from the latter measurements that the group consisting of workers engaged in radioactive work for more than 24 y has an average /sup 220/Rn level of 2.65 Bq which is significantly higher than that (1.27 Bq) found in the group that has worked for less than 12 y. A conversion factor of 0.09 deduced by earlier investigators is assumed to be valid for estimating the actual /sup 224/Ra burdens frommore » the /sup 220/Rn data.« less