Personal monitoring of old chemical weapons' dismantling operations at Poelkapelle (Belgium)

This article focuses on safety aspects of the dismantling of Old Chemical Weapons in Belgium, in particular of the shell type 77 mm filled with mustard gas (HD) and frequently chlorobenzene. Experiments were set up in order to determine whether the exposure limits for these chemicals (long-term as well as short-term) were exceeded during the dismantling process. In this process, two distinct operations were identified: (i) task 1 in which drilling and sampling are the main operations; (ii) task 2, consisting of a milling operation in order to separate the head from the shell body, followed by emptying and packing. For both subtasks the measured values are in agreement with a lognormal distribution. Significantly higher values for HD and for chlorobenzene concentrations are associated with task 2. A long-term respiratory overexposure might be excluded for chlorobenzene; for HD, however, a respiratory protection factor of at least 200 is indicated. To evaluate possible short-term overexposure via the skin, C.t values were measured for a sequence of task 2 operations. The results cannot be compared with a specific statistical distribution due to the fact that (i) these values are not truly independent, and (ii) the number of measurements is too limited to apply other inferential statistical methods. From the raw data, however, one can conclude that the upper confidence limit value of the 95th percentile remains lower than the accepted limit of 5 mg.min/ m³.