A risk-based methodology for deriving quality standards for organic contaminants in sewage sludge for use in agriculture--Conceptual Framework.

This paper describes a systematic methodology (Conceptual Framework) to derive quality standards for organic (anthropogenic) contaminants in sewage sludge added to agricultural land, in the context of revision of EU Sludge Directive 86/278/EEC and the broader Soil Thematic Strategy. The overall objective is to ensure, based on a risk assessment approach, a sustainable use of sludge over a long time horizon. ILSI-Europe's Conceptual Framework is in essence consistent with the EU Technical Guidance Document (TGD) for Environmental Risk Assessment of Chemicals in the soil compartment, or US-EPA's Sewage Sludge Use and Disposal Regulations, Part 503 Standards. A 'checklist' of different exposure pathways and transfer processes for organic contaminants needs to be considered, and the most sensitive relevant toxicological endpoint and its PNEC need to be identified. The additional complexity specific to deriving Sludge Quality Standards (SQS) is that the toxicity results may need-e.g., for (indirect) human toxicity-to be related back to maximum acceptable soil exposure levels (PEC(soil)). In turn, the latter need to be back-calculated to the maximum acceptable levels in sewage sludge (PEC(sludge)) at the time of application. Finally, for a sustainable sludge use, the exposure from repeated addition and potential chemical build-up over time (e.g., 100 years) needs to be assessed. The SQS may therefore vary with the (local) sludge application regime, and/or sludge pretreatment processes.

Congener specific transfer of PCDD/Fs from air to cows' milk: an evaluation of current modelling approaches.

Three different approaches have been used to model the transfer of individual PCDD/F congeners from the air to cows' milk. These are: (1) an 'Equilibrium Partitioning' approach, (2) a 'Deposition Velocity' approach and (3) a 'Scavenging' approach. Air-leaf transfers and livestock feed-milk transfers, the two most critical components of the food chain exposure model, are discussed. A representative database for measured PCDD/Fs in UK air, herbage and milk is presented and the performance of each predicted model concentration against this measured dataset is assessed. Weaknesses and uncertainties associated with modelling the complex transfer processes involved are highlighted.

The ecotoxicological significance of cadmium intake and residues in terrestrial small mammals.

Little is known about the ecotoxicological hazard of cadmium to wild small mammals. This paper reviewed laboratory and field studies to determine: (i) intake and residue lowest-observable-adverse-effect-levels (LOAELs) for the ecologically important parameters of reproduction and development; (ii) whether these LOAELs are exceeded by wild small mammals on contaminated habitats and what adverse effects result; and (iii) which species may be at most risk from cadmium. The intake LOAEL in laboratory rodents was 3.5-7.5 mg kg-1 body wt day-1 and the residue LOAEL, based on cellular damage in the kidney, was a renal cadmium concentration of 105 mg kg-1 dry wt. On contaminated habitats, these LOAELs are exceeded by common shrews Sorex araneus but not by wild rodents. However, there is little evidence of adverse cadmium-mediated effects in common shrews and this species may be tolerant to cadmium exposure. Large cadmium concentrations in body organs may simply reflect an ability to store cadmium in a nontoxic, metallothionein-bound state. In contrast, studies suggest that microtine voles may be sensitive to cadmium and, despite their relatively low cadmium intake and accumulated residues, may suffer adverse effects. The need to establish dose-residue-effect relationships for intakes and residues which are appropriate for wild species and also based on ecologically important parameters is discussed.

Predicting ecotoxicological impacts of environmental contaminants on terrestrial small mammals.

This review examines whether the effects of environmental contaminants on wild small mammals can be predicted from the results of single-species, laboratory toxicity studies. Heavy metals, organochlorines, chlorinated aromatic hydrocarbons, and OP/carbamate pesticides were identified as the groups of xenobiotics for which there are toxicity data for terrestrial small mammals and that, on the basis of persistence, acute toxicity, and bio-accumulation potential, present the greatest hazard to wild mammals. Laboratory-generated toxicity data, which used lethality and reproduction as measurable endpoints, were reviewed and intake and residue LOAELs estimated for representative chemicals (lead, endrin, PCBs) from the heavy metal, organochlorine, and chlorinated aromatic hydrocarbon substance groups; the OPs and carbamates were reviewed as a whole. Intakes and residues of these compounds in wild small mammals were compared with laboratory-defined LOAELs and the likelihood of effects predicted. The accuracy of these predictions was examined and the efficacy of extrapolating toxicity data from laboratory to wild species assessed. Qualitative extrapolation from laboratory to wild species was good for all the chemicals considered, laboratory tests correctly identifying the types of effects chemicals had on a wide range of wild mammals. In contrast, the quantitative extrapolation of dose-response data was either poor or largely unvalidated. This is because interspecies variation in sensitivity to xenobiotics and the effects on toxicity of differences in exposure pattern between laboratory and wild species are largely unquantified. Based upon the limited evidence available, errors in the direct extrapolation of dose-response data from laboratory to field may be as large as three orders of magnitude. Direct extrapolation of residue-response data from laboratory to wild mammals is good both for the effects of heavy metals on specific organs and for residues and acetylcholinesterase inhibition associated with pesticide-induced mortality. The use of organ residues or biomarkers to predict the severity of sublethal effects on reproductive output may be possible, although large residues or biomarker responses are not necessarily indicative of the severity of wider physiological effect. Appropriate residues/biomarkers may differ for various xenobiotics and even between species for the same xenobiotic. Further research is required to identify suitable markers that can be correlated with the occurrence and magnitude of ecologically important effects. Xenobiotics likely to have a direct effect on population dynamics are those that are persistent and adversely affect survival and reproduction. At present, this weak correlation is the only one that can be made between single-species laboratory tests and population effects.(ABSTRACT TRUNCATED AT 400 WORDS)

Trace metals in primary feathers of the Barn Owl (Tyto alba guttatus) in The Netherlands.

The number of Barn Owls in The Netherlands has been reduced substantially over the last few decades. Death as a result of poisoning seems unlikely, but the pathology of all bird species found dead in The Netherlands between 1975 and 1988 (n = 15 422) shows that 21% of all the birds were contaminated. However, the most important factor responsible for the decline in Barn Owl numbers in The Netherlands has not yet been established. As a part of a new national protection plan for the Barn Owl, the role of heavy metals has been investigated. Concentrations of heavy metals in the primary feathers of the Barn Owl varied according to their position in the wing; especially As, Sb, Fe and Zn whose concentrations depended on the place of the primary feather in the wing and the part of the vane which is used for the monitoring. The HS7 feather vane appears to provide a good estimate, even though the metal concentrations of this feather are always slightly lower than the concentrations in mixed samples of all ten primaries. It is recommended that they are used as a standard. Many factors affect metal concentrations. Increasing levels with age are found, presumably because metals are stored during growth at the end of the feathers as a method of reducing possible harmful effects. No significant correlations were found between the metal concentrations in the organs and those in the feather. Kidney and liver concentrations are always lower than the generally accepted levels for pathological damage of these organs. Even though metal concentrations in Barn Owl feathers are high compared with those reported for other birds in the Netherlands, it is concluded that Barn Owls are not adversely affected by current levels of heavy metal contamination in The Netherlands.

A mathematical model for cadmium in the stone loach (Noemacheilus barbatulus L.) from the River Ecclesbourne, Derbyshire.

A mathematical model which linked metabolism of stone loach with cadmium dynamics was developed using information from laboratory experiments and field studies. Three possible sources of cadmium were distinguished: water, food, and sediment. Predicted results over 1 year were compared with field observations from three sites in Derbyshire. The model adequately predicted growth of fish for all three sites. Predicted cadmium levels in loach were in good agreement with measured levels in fish from all three sites despite the fact that concentrations of cadmium in the environment were kept constant during each simulation. The weight of fish affected the relative importance of different pathways of cadmium intake under similar conditions. Uptake from water contributed substantially to body burden even though the concentration in water was lower than that in food or in sediment. However, uptake from both food and sediment could not be ignored given the measured levels of cadmium in the field. The relative importance of uptake from the three sources also differed with site. The model showed that metabolism, affected by temperature, is important to the dynamics of cadmium in the stone loach.

Lead and cadmium in stone loach (Noemacheilus barbatulus L.) from three rivers in Derbyshire.

Fish Noemacheilus barbatulus L. (stone loach) were caught at about 4-week intervals from single sites in three Derbyshire rivers, with different concentrations of cadmium and lead in sediments and water, during a 1-year sampling program. Fish were classified by age, site, and sampling occasion. Growth was allometric and affected by temperature. A steady state of cadmium burden was reached by fish of 2 years old or more but not by younger fish. For lead, fish rarely showed an increase in body burden. Differences in body size accounted for most of the variation in cadmium levels between loach of different age groups but were less important for lead levels. The exponent for body weight was not affected by age of fish and was about 0.79 +/- 0.06 for cadmium and 0.13 +/- 0.21 for lead. There was some correlation between cadmium levels in fish of different age groups taken at the same time from any site; levels of significance were higher when differences due to body size were discounted. Then, sampling time did not explain a significant part of the residual variation. Fluctuations in the cadmium and lead burdens for fish in the same age group from each of the sites were correlated for some comparisons. Loach from sites with higher metal concentrations had higher levels of both cadmium and lead. It is suggested that cadmium uptake from food contributed considerably to the body burden of loach.

Changes in concentration of lead and cadmium in water from three rivers in Derbyshire.

River water from three sites in different streams in Derbyshire was sampled during different periods within 1 year to evaluate fluctuations in cadmium and lead concentration. The results indicate that most of the cadmium was in solution, while most of the lead was associated with particles at all sites. Period of sampling appeared to have a greater effect on the concentration of cadmium and lead than flow rate: metal levels were higher in spring than in autumn. Nevertheless, the total lead concentration increased with flow rate, presumably because more particles were then brought into suspension; however, the lead concentration in the filtrate was reduced at higher flow rates, presumably due to dilution in the greater water volume. Dissolved cadmium concentration increased with rising flow rate at relatively low flow rates and was diluted at high flow rates. The data suggest that particles with which most of the lead is associated remain in suspension for a considerable time even when flow rate decreases.

Metabolic rate and uptake and loss of cadmium from food by the fish Noemacheilus barbatulus L. (stone loach).

Fish, Noemacheilus barbatulus (stone loach), of different body weights were used to study rates of uptake and loss of cadmium during and after dietary exposure. Fish were kept singly in a continuous-flow system, and fed tubificid worms. The worms had a range of cadmium levels, but all levels were below that needed to cause acute lethal toxicity in the fish. Body weight affected both the maintenance ration and the amount of food consumed ad libitum, but the exponent for body weight (0.78+/-0.04), relating body weight to food consumption, was unaffected by either temperature or the size of feeding ration. The cadmium content of the worms did not affect the size of the maintenance ration. Metal burden in fish changed rapidly both during and after exposure. After exposure, the cadmium burden of starved fish usually declined more rapidly than in fed fish. A 58-fold increase in cadmium content in the food produced a 28% increase of body burden in the fish, and there was no evidence for biomagnification. Maintenance ration and ration ad libitum and rates of uptake and loss of cadmium increased with temperature within the range 8-18 degrees C, but exposure to cadmium at 16 degrees C yielded a higher asymptotic body burden than either 8 degrees C or 18 degrees C. Rate constants for loss of cadmium after exposure appear to be lower than for loss during exposure. Rates of uptake and loss of cadmium vary with metabolic rate. A maximum in the rate of oxygen consumption was measured at 16 degrees C, above which the rate dropped, presumably due to stress. The exponent for body weight was unaffected by activity or temperature. Body weight of fish appeared to affect both the rates of uptake and loss of cadmium, and feeding rations and respiration to the same extent: body weight exponents were not dissimilar.