Rainer Frische

Criteria for assessing the environmental behavior of chemicals: selection and preliminary quantification.

Abstract The following criteria were found to be of prime importance for assessing the environmental behavior of chemicals: quantity (entering the environment), mobility, accumulation, persistence, and noxious effects (direct or toxic effects and indirect, e.g., meteorological, effects). These criteria were used in interdisciplinary “evaluation sessions” in order to assess retrospectively a number of well-known, “old” organic chemicals. The criteria were quantified using production volumes, physicochemical data, results of degradation and accumulation experiments, and toxicity values. The sum of the quantified criteria for each substance was related to the results of the evaluation sessions, using appropriate weighting factors. The criteria persistence and accumulation are the most important ones. Mutagenicity and carcinogenicity have to be strongly weighted in estimating the noxious effects. Mobility, although indispensable for estimating the distribution and persistence of a chemical, does not enter into the final assessment, since a high mobility can have beneficial as well as adverse effects. With the assessment of old chemicals being quite satisfactory, the method may now be extended to the more difficult case of new chemicals. Some suggestions for this procedure are presented.

Physicochemical properties as useful tools for predicting the environmental fate of organic chemicals

Abstract The distribution of a chemical between the environmental media air, water, and soil/sediment is largely determined by its physical and chemical properties. Relatively inexpensive (compared to field studies) measurements can be used in order to predict roughly the distribution of the chemicals. This is of greatest importance in testing new chemicals. In this case, nothing is known about the behavior of the substance in the natural environment. Models still remain to be developed for calculating the distribution on the basis of physicochemical data for different environmental conditions or, alternatively, by using globally averaged data. It is shown that—except in the case of highly persistent chemicals—distribution can only be considered in conjunction with (biotic and abiotic) degradation processes. According to our present knowledge, the key properties with regard to the environmental fate include vapor pressure, water solubility, adsorption and desorption behavior, partition coefficient (octanol/water), volatility from aqueous solution, and hydrolysis and photochemical reactivity in the air, in water, and when absorbed at surfaces (aerosol, soil, organic matter).

The Environmental Model Segment Approach for estimating potential environmental concentrations. I. The model.

Global distribution models which can be used for evaluating the environmental impact of persistent chemicals are not well suited to assess the environmental impact of less persistent substances; this is due to the fact that the environmental effects caused by the latter substances--if there are any--are only local or regional (close to the emission source), but not ubiquitous. As a tool for estimating potential regional exposure concentrations, the Environmental Model Segment Approach (EMSA) is presented. This model yields information about possible concentrations in reasonable worst-case situations.

The environmental model segment approach for estimating potential environmental concentrations. II: Application of the model to p-dichlorobenzene and trichloroethene

The Environmental Model Segment Approach introduced in Part I (R. Frische, W. Klöpffer, G. Rippen, and K. O. Günther, 1984, Ecotoxicol. Environ. Safety 8, 352-362) is applied to estimate potential environmental concentrations of p-dichlorobenzene and trichloroethene. Environmental concentrations of these chemicals can be estimated only with difficulty by other models because of many diffuse emission sources emitting mainly into the air. By comparison of the estimated with the measured environmental concentrations it is found that the claim of the model to yield values which apply to reasonable unfavorable environmental boundary conditions is satisfied for the medium air and for the biota (fish). Soil concentrations calculated by means of the model, assuming equilibrium with high air concentrations, are higher than the measured ones, while the calculated water concentrations are lower than the values often measured for river waters. The latter fact may be attributed to direct input of the substances into water which is not being taken into account.