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The Of/Oh-horizons of 447 forest stands in Germany were evaluated for concentrations and spatial distribution of selected polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs), and organochlorine pesticides (OCPs). While concentrations of dichlorodiphenyltrichloroethane (DDT) and PCBs show similar spatial distribution patterns for all measured compounds within each compound class, significantly different distributions were identified for concentrations of low-molecular-weight PAHs [2- and 3-ring PAHs plus fluoranthene (FLA) and pyrene (PYR)] in contrast to high-molecular-weight PAHs (4-6-ring PAHs without FLA and PYR). Maxima of persistent organic pollutant (POP) concentrations could be mostly explained by specific locatable sources. Because of the slow degradation rates of these target substances, this is especially relevant for historic contamination sources, such as extensive 1980s DDT usage in the former German Democratic Republic and industrial facilities that produced hexachlorobenzene (HCB) or PCBs. A contribution of ubiquitous background pollution derived from long-range atmospheric transport is likely for some compounds in the studied area, e.g., DDT in the western part of Germany and dieldrin. However, most target compounds appear to be mainly sourced from local or regional emissions. This is supported by the absence of clear dependencies between POP concentrations and most evaluated environmental and local parameters. We suggest that these results generally reflect the distribution of POPs in densely populated and industrialized countries located in temperate regions.

An evaluation was made of the recently developed risk assessment methodologies for new and existing chemicals in the European Communities. The evaluation also included the methodologies to prioritize chemicals and procedures for risk management, i.e., the (draft) guidance document for the development of strategies for risk reduction. The way in which chemicals are prioritized is accepted with only very few comments. Clear progress has been made in the development and harmonization of risk assessment methodologies and the application of estimation methodologies. Nevertheless, improvements are necessary for the estimation of consumer and occupational exposure, the derivation, use and transparency of assessment factors for chemicals and classes of chemicals based on the mode of toxic action, environmental exposure models and their validation and relation with monitoring data. As far as risk management is concerned it was recommended to improve the integration of the myriad of directives and regulations, to clarify definitions, to provide clear guidance on the determination and weighing of advantages and implications of risk reduction measures and to develop tools, including voluntary agreements, to speed up the slow chemical-by-chemical approach.

Recently we purified and cloned the mitogen/oncogene-activated Mr 70,000 (70K) S6 kinase from the livers of rats treated with cycloheximide (Kozma, S. C., Lane, H. A., Ferrari, S., Luther, H., Siegmann, M., and Thomas, G. (1989) EMBO J. 8, 4125-4132; Kozma, S. C., Ferrari, S., Bassand, P., Siegmann, M., Totty, N., and Thomas, G. (1990) Proc. Natl. Acad. Sci. U. S. A. 87, 7365-7369). Prior to determining the ability of this kinase to phosphorylate the same sites observed in S6 in vivo, we established the effects of different cations and autophosphorylation on kinase activity. The results show that the 70K S6 kinase is dependent on Mg2+ for activity and that this requirement cannot be substituted for by Mn2+. Furthermore, 50-fold lower concentrations of Mn2+ block the effect of Mg2+ on the kinase. This effect is not limited to Mn2+ but can be substituted for by a number of cations, with Zn2+ being the most potent inhibitor, IC50 approximately 2 microM. In the presence of optimum Mg2+ concentrations the enzyme incorporates an average of 1.2 mol of phosphate/mol of kinase and an average of 3.7 mol of phosphate/mol of S6. The autophosphorylation reaction appears to be intramolecular and leads to a 25% reduction in kinase activity toward S6. In the case of S6 all of the sites of phosphorylation are found to reside in a 19-amino acid peptide at the carboxyl end of the protein. Four of these sites have been identified as Ser235, Ser236, Ser240, and Ser244, equivalent to four of the five sites previously observed in vivo (Krieg, J., Hofsteenge, J., and Thomas, G. (1988) J. Biol. Chem. 263, 11473-11477). A fifth mole of phosphate is incorporated at low stoichiometry into the peptide, but the amino acid which is phosphorylated cannot be unequivocally assigned. The low level of phosphorylation of the fifth site in vitro is discussed with regard to known results and to a potential three-dimensional model for the carboxyl terminus of S6.