Application of mathematical modelling for assessing the urinary half-times of nickel in stainless steel welders.

The study regards workers employed in manual metal are welding of stainless steel (MMA/SS). For two weeks they collected their urine during the work shift and the 16 hours following in order to evaluate the kinetics of nickel. Using one-compartment mathematical modelling we calculated the values of the toxicant's urinary half life during the two phases of exposure and postexposure and also during non working weekends. The aim of the study was to find correlations between inhaled doses and excreted quantities and to acquire practical data for use in biological monitoring. In the welders the mean urinary half life in the exposure period was 59.5 hours, in the post exposure it was 95.6 hours, while in weekend it was 95.5 hours. The study showed that exposure to fumes containing nickel could determine the accumulation of the metal in slow elimination speed compartment. As a consequence of the accumulation of nickel in compartments with different elimination speeds, the collection of single urinary portions in biological monitoring seems to give little information about the actual exposure. In our opinion this indicates collecting urine samples throughout the entire work shift and the 16 hours following exposure.