Chemosphere, Vo1.15, No.2, DD 139-147, 1986 0045-6535/86 $3.00 + .OO Printed in Great Britain 01986 Pergamon Press Ltd. CHEMICAL DEGRADATION OF XENOBIOTICS II. SIMULATION OF THE BIOTIC TRANSFORMATION OF BIS(2-ETHYLHEXYL)PHTHALATE AND DIOCTYLPHTHALATE BY ABIOTIC MEANS J. Brodsky, J.T. Andersson, K. Ballschmiter* University of Ulm, Department of Analytical Chemistry D-7900 Ulm, F.R.G. I. Introduction Bis(2-ethylhexyl)phthalate (BEHP) is a high-volume industrial chemical with an annual production of nearly 5xi05 tons. It is primarily used as a plastisizer for polyvinyl chloride. It nowadays occurs so ubiquitously in the environment that in fact elaborate precautions are required in environmental sampling to avoid this contaminant. The large amounts consumed and the wlde-spread distribution assure an almost universal exposure to it. Although generally considered a safe chemical, concern about its safety has arisen after evidence was found that BEHP could cause tumours in bioassays of rats and mice [I]. The metabolic products of BEEP are of obvious interest in any study of the safety of this and related phthalates. Through the use of various gas-chroma- tographic and mass-spectroscopic techniques eighteen oxidized metabolites were identified from the urine of BEHP-treated rats [2,3] (Fig. I) , all of them displaying one hydrolysed ester group and one or two oxygenated functionalities in the remaining ester alkyl group. Several of the products arise through oxidative loss of carbon atoms. Ring-oxidized products were not observed. To a large extent the product pattern resembles that from alkanes in that ~- and ~-I oxidation predominates but the situation is complicated by the fact that introduction of an hydroxyl group can take place also at other positions. Phthalate esters are hydroxylated in the ring by Micrococci if the alcohol moiety contains up to six carbon atoms in length [4]. As a complement to biological studies of the metabolism of environmentally relevant chemicals, work in our laboratory has shown [5] that it is possible to use simple chemical reactions to simulate the biotic pathways. An absolute correspondence between the biotic transformation and the chemical simulation can of course never be expected since the reaction conditions are widely different, but still a useful correspondence is often observed. The advantages of a preliminary chemical simulation of the metabolism of environmentally relevant chemicals are several: larger amounts can be used, facilitating product identification and isolation of substances which may be of benefit as reference compounds for biotic studies; shorter times are needed; simpler experimental set-up without the need for animals, test cultures or simulated ecological systems. We have now extended our chemical studies to two phthalates, BEHP and dioctyl- phthalate (DOP). Our aim was to find conditions which simulate biotic reaction patterns in that the ester alkyl group should be oxidized but not the aromatic ring. Furthermore, in order to keep the concept of chemical simulation as general and simple as possible, we wished to limit ourselves to those oxidants which were effective An previously investigated systems. 139