Case study on occupational exposures to radiation with possible co-exposure to heavy metals

Biodosimetry is a valuable tool for determining the ionising radiation dose received by exposed individuals. The dicentric chromosome assay and translocation analysis are both standardised methods of biodosimetry which analyse chromosome damage. The dicentric chromosome assay is most suitable for acute exposures in the recent past as the dicentric frequency decreases with time after exposure. Translocation analysis is more appropriate for chronic exposures and older exposures as the translocations are considered stable and long-lasting. For both, analysis of low doses is difficult due to the stochastic nature of the damage and high levels of uncertainty. Complicating matters, confounding factors, such as medical exposures or exposures to heavy metals, have been shown to have an additive or synergistic effect to damage from radiation. For the situation described here, the individuals were welders who were also potentially exposed to both radiation and heavy metals. Biodosimetry was performed on 8 welders who were potentially exposed to ionising radiation during an industrial radiographic procedure using 192 Ir for non-destructive testing. Analysis was performed 4–6 years after the suspected exposures and chromosome damage above expected background levels was detected. Here we discuss the analysis performed, the methods used to estimate whole-body doses and the involvement of confounding factors.