[en] The uncertainties associated with the determined measurement of lung burdens of transuranium elements become important when positive results are obtained. A lung burden of 16 nCi of ²³⁹Pu with no uncertainty was reported for one individual on each of three different counts. Because the uncertainty was not reported it was impossible to evaluate the exposure with any degree of confidence. The result could mean that one lung burden of activity has been determined or it could mean that the detection limit for the method has not been exceeded and so the person has no measurable activity. An alternate method of measuring ²³⁹Pu in the body is to separate and count the ²³⁹Pu excreted in the feces or the urine. An assumption must be made about how the eliminations from the body represent the material deposited inside the body. Although uncertainties do exist in this assumption the advantage over chest counting is that the detection limit is only 0.002 of a maximum permissible lung burden instead of being a one permissible burden