Presentation of a general algorithm to include effect assessment on secondary poisoning in the derivation of environmental quality criteria. 2. Terrestrial food chains.

In a previous study a simple algorithm was presented for effect assessment on secondary poisoning of birds and mammals. This algorithm (MPC = NOECfish-eater/BCFfish) was drawn up by analyzing a two-step aquatic food chain (water-fish-bird/mammal). The algorithm was used to test whether quality criteria set for surface water, based on effect assessment for aquatic organisms, constitute a "safe" level for secondary poisoning. The present study analyzes whether this algorithm can equally well be used for effect assessment in a terrestrial food chain. The pathway soil-earthworm-bird/mammal was used as an example for a terrestrial food chain. Literature data of six selected compounds (lindane, dieldrin, DDT, PCP, cadmium, and mercury) on both bioconcentration factors for earthworms and toxicity data for birds and mammals were studied. Important differences were found between BCFs for this terrestrial pathway and BCFs for the aquatic pathway analyzed in the previous study. It was found that BCFs for earthworms were more dependent on soil-related properties than on compound-specific properties. Hence, it was concluded that the algorithm MPC = NOECworm-eater/BCFworm can be used only for effect assessment on terrestrial food chain in defined situations. By calculating maximum permissible concentrations for secondary poisoning (MPCsp) for a standard soil situation and comparing these to MPCs for soil organisms, it was concluded that secondary poisoning could be a critical pathway for cadmium and methyl mercury. For methyl mercury secondary poisoning in an aquatic food chain was also a critical pathway. Secondary poisoning of fish-eating birds and mammals is not likely to occur for cadmium at concentrations in water below the MPC calculated for aquatic organisms.

Presentation of a general algorithm to include effect assessment on secondary poisoning in the derivation of environmental quality criteria. Part 1. Aquatic food chains.

Effect assessment on secondary poisoning can be an asset to effect assessments on direct poisoning in setting quality criteria for the environment. This study presents an algorithm for effect assessment on secondary poisoning. The water-fish-fish-eating bird or mammal pathway was analyzed as an example of a secondary poisoning pathway. Parameters used in this algorithm are the bioconcentration factor for fish (BCF) and the no-observed-effect concentration for the group of fish-eating birds and mammals (NOECfish-eater). For the derivation of reliable BCFs preference is given to the use of experimentally derived BCFs over QSAR estimates. NOECs for fish eaters are derived by extrapolating toxicity data on single species. Because data on fish-eating species are seldom available, toxicity data on all birds and mammalian species were used. The proposed algorithm (MAR = NOECfish-eater/BCF) was used to calculate MARS (maximum acceptable risk levels) for the compounds lindane, dieldrin, cadmium, mercury, PCB153, and PCB118. By subsequently, comparing these MARs to MARs derived by effect assessment for aquatic organisms, it was concluded that for methyl mercury and PCB153 secondary poisoning of fish-eating birds and mammals could be a critical pathway. For these compounds, effects on populations of fish-eating birds and mammals can occur at levels in surface water below the MAR calculated for aquatic ecosystems. Secondary poisoning of fish-eating birds and mammals is not likely to occur for cadmium at levels in water below the MAR calculated for aquatic ecosystems.

Validation of some extrapolation methods with toxicity data derived from multiple species experiments.

For effects assessment several extrapolation methods are used which can be applied to estimate the concentration of toxic chemicals above which ecosystems may be affected. At present, however, it is uncertain whether the values calculated with these methods really represent concentrations harmless to ecosystems. Therefore, a validation is carried out by comparing no-observed-effect concentrations derived from multiple species experiments with extrapolated values. In this study validation was restricted to the methods of Aldenberg and Slob (1993) and Wagner and Løkke (Water Res. 25, 1237-1242, 1991), and a modification of the method of the Environmental Protection Agency (Slooff, 1992). Also, only organic compounds were studied. With restrictions, due to the paucity of data, it is concluded that single species toxicity data are a good starting point for establishing "safe" values for the aquatic ecosystem. Furthermore, extrapolation methods seem to be a good basis for determining these values if sufficient toxicity data are available for sensitive taxonomic groups. From the results of this study it was not possible to give preference to one of the validated extrapolation methods, but on theoretical ground the methods of Aldenberg and Slob and Wagner and Løkke are perferred.

Presentation of a general algorithm to include secondary poisoning in effect assessment.

A general algorithm for effect assessment on secondary poisoning for birds and mammals is presented. This algorithm (Maximum Permissible Concentration = NOECbird/mammal/BCF) was drawn up by analysing an aquatic food chain (water--fish--bird or mammal) and a terrestrial food chain (soil--worm--bird or mammal). NOECs and bioconcentration factors (BCFs) were collected for a set of selected compounds: lindane, dieldrin, cadmium and mercury in both water and soil, PCB153 only in water and DDT and PCP only in soil. BCFs for the terrestrial pathway are frequently < 1 and rarely above 10, though for the aquatic pathway BCFs up to 10(4) were found for the same compounds. By calculating MPCs for fish-eaters and comparing these to MPCs calculated for aquatic organisms, secondary poisoning could be a critical pathway for methyl-mercury and PCB153. For lindane the conclusion depends on whether a separate or combined data set is chosen for birds and mammals. By calculating MPCs for a standard soil situation and comparing these to MPCs for terrestrial organisms, secondary poisoning could be a critical pathway for cadmium and methyl-mercury.

Ecotoxicological effects assessment: a comparison of several extrapolation procedures.

In the future, extrapolation procedures will become more and more important for the effect assessment of compounds in aquatic systems. For achieving a reliable method these extrapolation procedures have to be evaluated thoroughly. As a first step three extrapolation procedures are compared by means of two sets of data, consisting of (semi)chronic and acute toxicity test results for 11 aquatic species and 8 compounds. Because of its statistical basis the extrapolation procedure of Van Straalen and Denneman is preferred over the procedures of the EPA and Stephan et al. The results of the calculations showed that lower numbers of toxicity data increase the chance of underestimating the risk of a compound. Therefore it is proposed to extend the OECD guidelines for algae, Daphnia, and fish with chronic (aquatic) toxicity tests for more species of different taxonomic groups.

The usefulness of histopathology in aquatic toxicity studies.

1. A survey was carried out to examine the usefulness of histopathology for the identification of toxic effects of environmental contaminants in fish. 2. Two small fish species, Poecilia reticulata (guppy) and Oryzias latipes (medaka) were used, and two exposure periods (1 and 3 months) were chosen. 3. The following compounds were studied: beta-hexachlorocyclohexane, bis(tri-n-tributyltin)oxide, di-n-butyltindichloride, sodium bromide, methyl bromide, and methylmercury chloride. 4. The following is concluded: histopathology provides useful data in characterizing toxic effects in fish; there is a slight advantage for Poecilia reticulata over Oryzias latipes; there is no advantage for 3 months exposure vs 1 month.

Relation between water solubility, octanol/water partition coefficients, and bioconcentration of organic chemicals in fish: a review.

A survey was made of the literature describing relations between water solubility (S), the octanol-water partition coefficient (Poct), and the bioconcentration factor (BCF) of organic chemicals. Based on the relations between BCF and Poct it can be concluded that mostly BCF is log BCF = 0.79 log Poct-0.40. From relations between Poct and S it can be concluded that for most organic chemicals log Poct will not exceed 3 if S is greater than ca. 3 mmol/liter. This limit is far more reliable than the value of 2000 mg/liter which has been proposed by OECD Experts and confirmed by other authors.

Toxicity, biodegradability, and accumulation of a number of Cl/N-containing compounds for classification and establishing water quality criteria.

The evaluation of the ecotoxicity of chemical compounds is often hampered by the scarcity of the literature data on toxicity, biodegradability, and accumulation. In this study additional data on 16 Cl/N-containing organic compounds were gathered by laboratory experiments. For assignment to so-called gray or black lists, two different classification schemes were used. According to both schemes 3-nitrotoluene, 1,2- and 1,3-dichlorobenzene, the 1-chloro-nitrobenzenes, 2,3-dichloronitrobenzene, 2-chloroaniline, and 2-chloro-4-nitroaniline were marked as black list substances, primarily based on poor biodegradability; 2- and 4-nitrotoluene, nitrobenzene, and 2-methoxyaniline were classified as gray list substances. For 3- and 4-methoxyaniline and 1,4-dichlorobenzene no agreement in classification was obtained. Additionally, water quality criteria are proposed for 2-, 3-, and 4-nitrotoluene and nitrobenzene, based on long-term toxicity data: respectively 0.3, 0.2, 0.4, and 1.0 mg/liter.

Study on the toxicity of sodium bromide to different freshwater organisms.

The toxicity of sodium bromide for freshwater organisms was tested using algae (Scenedesmus pannonicus), crustaceans (Daphnia magna) and fish (Poecilia reticulata and Oryzias latipes). Depending on the species tested, the acute toxicity varied from 44 to 5800 mg Br-/litre (EC50 values) and the No Observed Effect Concentrations (NOEC values) in the long-term tests varied from 7.8 to 250 mg Br-/litre. Bromide ion markedly impaired reproduction in both crustaceans and fish. Histologically no effects were observed in the long-term test with Oryzias, but in the reproduction test with Poecilia, hyperplasia of the thyroid, atrophy and degeneration of the musculature and regressive changes in the female reproductive tract were observed. As a criterion of water quality, 1 mg Br-/litre has been proposed, on the basis of reproductive performance in the Poecilia test. The concentrations found in surface water frequently exceed this value and sometimes reach levels at which acute effects on water organisms can be expected.

The toxicity of benomyl, thiophanate-methyl, and BCM to four freshwater organisms.

The EC50 or LC50 values after a 2-day exposure of the three fungicides benomyl, thiophanate-methyl and BCM, have been determined using four freshwater organisms: Chlorella pyrenoidosa, Daphnia magna, Lebistes reticulatus and Salmo gairdneri. The influence of BCM on the reproductive capacity of Daphnia was also investigated and from these data provisional ecological limit was established.

The short-term toxicity of some feed additives to different freshwater organisms.

The short-term toxicity (EC50 respectively LC50 after 2 or 4 days) of 13 feed additives was determined to 4 freshwater organisms of different trophical levels: Chlorella pyrenoidosa, Daphnia magna, Lebistes reticulatus and Salmo gairdneri. The most toxic (LC(EC)50 less than 1 mg/1) were robenidine (to all tested organisms) and stenorol (to Daphnia); moderately toxic (1 less than LC(EC)50 less than 10 mg/1) was pyrimethamine. Amprolium, ethopabate, furazolidone and zoalene proved to be little toxic (LC(EC)50 greater than 10 mg/1); whereas buquinolate, carbadox, clopidol, decoquinate, grofas and sulfaquinoxaline were under the experimental conditions not toxic for the tested organisms.