Butadiene and isoprene: future studies and implications.

Based on the symposium on 1,-3-butadiene and isoprene at Blaine, WA, the following areas need special attention for future research: (1) discrepancies in PBPK modelling by different groups should be solved; (2) potential human target tissues (bone marrow, lymphatic tissues) should be better integrated into PBPK models; (3) the present rapid development in research on human genetic interindividual differences in 1,3-butadiene metabolism and toxicity should be supported, with the intention to determine human subgroups of differential susceptibility and to integrate this into epidemiological research; (4) further validation of past exposures in the epidemiologically studied corhorts is very desirable; (5) the question of possibly differential effects in 1,3-butadiene monomer workers and styrene-butadiene-rubber workers (lymphosarcoma?, reticulosarcoma?, leukemia?) should be resolved in future epidemiological studies; (6) potential human target tissues (bone marrow, lymphatic tissues) should be better integrated into PBPK modelling; (7) risk assessment of isoprene and, by quantitative comparison, of 1,3-butadiene in humans should consider the physiological background of endogenous isoprene production; and (8) future research on biomarkers should establish practical tools for medical surveillance of presently exposed persons.