Biomonitoring of plasticizers: General background and workplace exposure

Background: The phthalate and plasticizer market is rapidly changing because labeling requirements as well as application prohibitions have been imposed on certain phthalates due to confirmed reprotoxic effects. The use of the historically most important plasticizer diethylhexyl phthalate (DEHP) is, therefore, rapidly declining. Less toxic phthalates and non-phthalate plasticizers are filling this gap. Human biomonitoring (HBM) is able to determine internal exposure to more than 10 different phthalates by measuring specific metabolites in urine. By means of extrapolating metabolite levels to amounts actually absorbed and the comparison with data from animal studies, HBM allows both a reliable assessment of exposure and also an objective risk assessment. Methods: Studies with HBM have shown that the general population is exposed to a large number of phthalates. The levels of some phthalates have been and are observed to be in excess of the environmental guidance values. Results: The HBM measurements show that the development of internal exposure closely reflects the changes in the phthalate market; therefore, exposure to critically assessed phthalates is steadily declining. The HBM data from the occupational environment also confirm that critically assessed phthalates have largely been replaced. Conclusion: To monitor the substitution process and also to be able to include the alternative plasticizers in a timely exposure and risk assessment, HBM methods for the main substitutes are currently being developed. For some of these substitutes, e.g. diisononyl 1,2-cyclohexanedicarboxylic acid (DINCH), dipropylheptyl phthalate (DPHP) and diethylhexyl terephthalate (DEHTP) preliminary HBM data are already available, which demonstrate increasing exposure but according to the current state of knowledge this should not be assessed as critical.