New PBPK model applied to old occupational exposure to benzene

An intensive program of benzene monitoring using new techniques was underta ken in Western Europe in the late 1960s and early 1970s, Significant exposu re was found in the transport of benzene and gasoline, particularly during the loading of barges, and during the loading and operation of sea-going ve ssels. The ceiling threshold limit value of 25 ppm recommended at that time generated problems in assessing exposure, so alternative criteria were pro posed. During that period some shore-based exposures were reported, and the ir significance was discussed in several articles. The information gained a t that time is reexamined by physiologically based pharmacokinetic (PBPK) m odeling and is used to help validate an improved PBPK model, which is descr ibed and tested on results from experimental exposure in a companion articl e. The old field data, comprising five specific studies, confirm the releva nce of modeling to assessment of occupational exposure, and demonstrate its value for interpretation of field data, which is seldom as complete, syste matic, or accurate as that obtained in experimental work. The model suggest s that metabolism of benzene in humans may not be restricted to the liver. Sites and processes of metabolism merit further investigation.