Development of a biomathematical model to describe the exposure dose relationship for inhaled dust among UK coal miners.

The aim of this study was to investigate exposure-dose relationships in humans with working lifetime exposures to respirable particulates, by using a bio-mathematical exposure-dose model to predict lung and lymph node dust burdens in coalminers with long-term exposure to respirable dust. To meet this aim, statistical and mathematical modelling techniques were used to analyse data from an autopsy study of UK miners held at the Institute of Occupational Medicine. In this study, we validated an existing lung dosimetry model for consistency with observed human lung and lymph burden data. The results of our test suggested that, for humans, the sequestration of dusts in the interstitial compartment is a more prominent feature than the retention of dust due to overload that is observed in animal studies. Modelling and statistical analyses have shown that quartz is more likely to be retained in the lung and lymph nodes than the non-quartz fraction of lung burden and that the quartz fraction may play an important role in the development of PMF. The results of statistical analyses have also shown that the translocation to the lymph nodes is not simply a linear function of lung burden, but may terminate beyond a threshold in lung burden. Our assessment of the variation in the model parameters yielded a distribution of values for the clearance rate and the translocation rate to the lymph nodes respectively. While other sources of uncertainty (e.g. uncertainty in exposure estimation) were not investigated in this study, the results suggested that variability can be quantified and incorporated in the current modelling framework. This approach may be useful for assessing risk in humans to dust exposure.