The National Dose Registry has recorded a value of zero
for all doses below the reporting limit of their respective
dosimetry processors, which was 0.20 mSv in most cases.
This procedure could underestimate the cumulative lifetime
doses and thus overestimate the risk. Although unlikely, considerable
underestimation of a cumulative dose could occur if
all doses recorded as zero were actually just below the reporting
limit. We had insufficient information to determine the
degree of underestimation that could result from this practice.