The Gorleben salt dome is considered as a potential disposal site for radioactive waste. In the safety assessment study, a number of pumping tests are carried out in the geohydrological system surrounding the salt dome. The Gorleben pumping test is simulated in a number of subsequent steps. In the first modelling step the analytical Theis solution is applied. Significant differences between the calculated and observed drawdowns show that the Theis solution assumptions are inappropriate to describe the Gorleben geohydrological system. In the second modelling attempt, the pumping test is simulated numerically with the METROPOL computer code. Geological borelog data and geohydrological profiles and maps are interpreted to obtain information on the aquifer geometry, anisotropy and possible heterogeneity. Under the assumptions of an anisotropic and heterogeneous geohydrological system, simulations of the Weisses Moor pumping test provide calculated drawdowns which match the observed drawdowns reasonably.

The report is an update of the exploratory report acrolein (Slooff et al., 1991) that served as a basis for the discussion during the exploratory meeting on acrolein in March 1992. The meeting supported the conclusion that priority should be given to the compartment air and to the risks to humans. With respect to inhalation and dietary exposure of humans to acrolein, a maximum permissible concentration of 0.5 mug.m-3 and a tolerable daily intake of 0.5 mug.kg-1 bw. day-1 (equivalent to 30 mug.day-1 for a 60 kg person) has been derived, respectively. The available data on human exposure levels indicate that the current acrolein concentrations in outdoor air (incase of high traffic density) and, especially, in indoor air likely exceed the maximum permissible concentration in air and that the dietary intake of acrolein may exceed the tolerable daily intake. It is noted, however, that with respect to the Netherlands only very limited data on acrolein concentrations in outdoor air are available and that data on acrolein concentrations in indoor air and in foodstuffs and beverages are lacking. Therefor, a sound risk evaluation is not possible.<br>

This report presents a general overview of the field of risk comparison for radiation radioactive and chemical substances and industrial safety. It summarizes the results of interviews with representatives of DGM and RIVM, and describes different risk methods in a graphical presention.<br>

Four main natural resources can be distinguished: chemical elements, energy carriers, environmental resources (air, water, soil), and bioresources. Within bioresources can be distinguished: biomass (e.g. stock of wood or fish), and biodiversity. Biodiversity can be described in terms of genes, species or ecosystems. Although genetic variety is the most fundamental concept, species are mostly used as a more practical alternative. The Dutch environmental policy aims for the protection of 95% of the species. The Dutch policy for nature conservation selected "aim-species" on criteria as international rareness/distribution area, national rareness and declining trend. More attention should however be paid to: - the genetic information value per species (cladistic value), - the use of risk analysis. The motives of biodiversity consists of - financial or other utilitarian motives, - more spiritual or religious motives: . stewardship . esthetic, religious feelings of alliance with nature, . partnership (between man and nature based on mutual respect). The main functions are production, carrier, regulation and information. These functions can be subdived in at least 37 subfunctions. A summary of concrete and often monetised examples of functions is given to illustrate and underpin the importance of different functions. An overview of evaluation methods of biodiversity is given.

A pilot plant study on the behaviour of ethylene diamino- tetraacetic acid (EDTA) during groundwater recharge of river water confirmed that EDTA is nondegradable under anaerobic and subtoxic conditions and partially degradable under aerobic conditions. The degree of aerobic degradation showed to be dependent on EDTA concentrations and temperature. At concentrations of about 500 mug EDTA/l, at a retention time of 15 days in the recharge bed, the removal was approx. 60% at a temperature >10 degrees C and approx. 30% at a temperature < 10 degrees C. At concentrations of tens of mug/l, i.e. the present maximum concentration level in the water of the rivers Rhine and Meuse, the removal was approx. 33% at a temperature >10 degrees C and approx. 15% at a temperature <10 degrees C. At concentrations of 7 mug/l no removal was found. The most serious consequence of the pollution of river water by EDTA for the drinking water supply using dune or bank recharge appears to be the adverse effect on the removal of heavy metals, respectively their mobilisation during the recharge. From the studied heavy metals (Cd, Cu, Ni, Pb, Zn) the most profound mobilisation effects have been found for Pb, Ni and Cu. The mobilisation of Pb has been found by the recharge in the dune sand contaminated by suspended solids from river water. The mobilisation was substantially higher during winter than during summer. In winter at a EDTA concentration of 500 mug/l the mean Pb concentration in the effluent of the recharge tank exceeded the WHO drinking water quality guideline of 10 mug/l. Based on the varations of phosphate concentrations in the effluent of the tank, it has been suggest that the seasonal differences in the mobilisation effects were caused by the formation of highly insoluble Pb5(PO4)3Cl. Mobilisation effects for Cu and Ni were found already at a concentration as low as 90 mug EDTA/l.

This report contains general information on phthalic anhydride concerning the existing standards, emissions, exposure levels and effect levels. Since phthalic anhydride will rapidly hydrolyse to o-phthalic acid in the presence of water, this reaction product is included in the evaluation. In general data on phthalic anhydride are very scarce and incomplete, hampering a sound risk evaluation. In the Netherlands the registered emissions (0.57 tonne per year) are small (0.0005%) compared with the amount of phthalic anhydride produced, imported and applied (approx. 110,000 tonnes per year). For the general population, inhalation is considered the most likely exposure route. In one limited 8-month study with guinea pigs a LO(A)EL of 8,500 mug.m-3 was derived for phthalic anhydride. Based on the registrated emissions the exposure levels will not likely exceed the 1 mug.m-3 level. From this one may conclude that the risk of inhalatory outdoor exposure to phthalic anhydride to the general population seems to be small, if present at all. As to oral exposure, an tentative toxicological limit value of 0.375 mg.kg-1 bw per day NO(A)EL was derived from a two-year carcinogenicity study, applying a large safety factor (1,000). This tentative toxicological limit value is not likely to be exceeded. No data are available on the toxicity of phthalic anhydride and its main conversion product, o-phthalic acid, to aquatic and terrestrial species. Data on the occurrence in the environment in the Netherlands are scanty. Phthalic anhydride has been reported to hydrolyze very rapidly (estimated half-life of approx. 1.5 minutes). Consequently, its product is biodegraded rapidly as well. Taking into account the emission figures the risk for aquatic and terrestrial life is expected to be small. It is concluded that phthalic anhydride does not seem to present a significant risk to humans or ecosystems in the Netherlands. Therefore it is recommended not to stimulate in depth studies on phthalic anhydride but to remove phthalic anhydride from the attention substances list.

Since February 1990, dioxin levels are measured in cow's milk from selected dairy farms in the neighbourhood of dioxin sources like municipal waste incinerators (MWIs) and metal reclamation plants. Levels are expressed in picograms 2,3,7,8-TCDD toxicity equivalents (TEQ) per gram of milk fat, calculated on the basis of international toxicity equivalence factors (I-TEF) of individual congeners. This report presents the results of the measurements in samples of cow's milk from three dairy farms near the MWI of Rotterdam (the Lickebaert area), the Netherlands. These samples were collected in the period of July to September 1993. Dioxin levels ranged between 3.8 +/- 0.2 and 6.2 +/- 0.3 pg TEQ/g of fat. The decline as observed in the period April to June 1993 proceeds less clearly and seems to stabilize at a level between 4.6 +/- 0.2 and 5.1 +/- 0.3 pg TEQ/g of fat in September 1993, just below the Dutch legislation level for dioxins in cow's milk (6 pg TEQ/g of fat).

The determination of N-nitrosodimethylamine (NDMA) is beer by matrix dispersion solid phase extraction on Celite and GC-TEA detection was studied. The procedure that came out is described in the Annex and was labeled with performance characteristics resulting from the analysis of 11 beer samples differing in matrix composition as widely as possible. All samples were assayed, at least, in duplicate. NDMA levels found ranged, on average from 0.09 to 0.26 mug/kg. Sample 93M0198 contained on average (N=6) 0.13 mug/kg of NDMA and the coefficient of variation was 9.5%. For the remaining samples the repeatability, calculated as the difference in procent of the individual result versus the average result of the sample, is 15% or better. In all, 15 recovery experiments were carried out at NDMA spiking levels of 0.2 - 0.5 and 1.0 mug/kg. On average the recovery was 100 +/- 6%. The limit of detection and of quantitation were calculated from the results of 4 blank determinations, resulting in a tentative value of about 0.05 mug/kg and of about 0.1 mug/kg respectively. The determination of NDMA in beer by matrix dispersion solid phase extraction and GC-TEA detection is easy to handle and much faster, but less sensitive, then the combination of vacuum distillation and GC-TEA detection used so far.

In this study a ICP-MS-method was developed for the determination of Be and Al in ground and drinking-water samples. Detection limits are 50 ng/l Be and 2 mug/l Al if care is taken to avoid Al contamination ; the precision amounts to 2% RSD at elevated concentrations. Spectral interferences due to major components in ground water are negligible. Matrix effects are absent or are reduced to negligible levels after dilution of the samples to less than 5 muM Ba, 10 mM Ca, 1 mM Fe, 5 mM K, 5 mM Mg, 20 mM Na, 2 mM Si or 4 mM SO4. The calibration curve is linear up to at least 20 mug/l Be. Due to linearity problems in the range up to 50 mug/l Al, the ICP-MS technique is less suitable for the determination of Al. The ICP-MS method was applied to the analysis of ground and drinking-water samples from 91 locations in the Netherlands. 10% of the ground water samples and 3% of the drinking-water samples had concentrations above the detection limit for Be with a maximum of 900 ng/l Be in ground water samples and 200 ng/l Be in drinking-water samples. 20% of the groundwater samples and 20% of the drinking-water samples had concentrations above the detection limit for Al with a maximum of 985 mug/l Al in ground water samples and 205 mug/l Al in drinking-water samples.

This report is the Dutch contribution in the Pilot Project of OECD's Pesticide Program. The Netherlands acted as lead country for pyridate for the comparison of evaluations of six participating countries, including Australia, Canada, Germany, Switzerland, the Netherlands and the United States of America. The lay-out of reviews are compared with each other and it was shown that of all participating countries only the Netherlands summarize all studies on toxicology and ecotoxicology individually. Of all references of all countries together only 61 out of 372 references were reviewed by two or more countries. From the common studies the countries established always the same endpoints. Only for some studies different final fate and effect data were reported. But in all cases the differences were only small. It can be concluded that it seems possible for countries to use reviews prepared by other participating countries for establishing their own results. Standardization showed to be important for several subjects