Search

This article presents a case study demonstrating the application of 3 individual-based, spatially explicit population models (IBMs, also known as agent-based models) in ecological risk assessments to predict long-term effects of a pesticide to populations of small mammals. The 3 IBMs each used a hypothetical fungicide (FungicideX) in different scenarios: spraying in cereals (common vole, Microtus arvalis), spraying in orchards (field vole, Microtus agrestis), and cereal seed treatment (wood mouse, Apodemus sylvaticus). Each scenario used existing model landscapes, which differed greatly in size and structural complexity. The toxicological profile of FungicideX was defined so that the deterministic long-term first tier risk assessment would result in high risk to small mammals, thus providing the opportunity to use the IBMs for risk assessment refinement (i.e., higher tier risk assessment). Despite differing internal model design and scenarios, results indicated in all 3 cases low population sensitivity unless FungicideX was applied at very high (×10) rates. Recovery from local population impacts was generally fast. Only when patch extinctions occured in simulations of intentionally high acute toxic effects, recovery periods, then determined by recolonization, were of any concern. Conclusions include recommendations for the most important input considerations, including the selection of exposure levels, duration of simulations, statistically robust number of replicates, and endpoints to report. However, further investigation and agreement are needed to develop recommendations for landscape attributes such as size, structure, and crop rotation to define appropriate regulatory risk assessment scenarios. Overall, the application of IBMs provides multiple advantages to higher tier ecological risk assessments for small mammals, including consistent and transparent direct links to specific protection goals, and the consideration of more realistic scenarios., (© 2015 SETAC.)

Risk and hazard assessments for the soil environment are performed on the basis of the total content of a contaminant in the dry bulk soil. Presently, scientific evidence is emerging and indicating that pore water may be a more relevant exposure medium for uptake of chemicals by biota and plants in soil. To deduce the degree to which pore water concentrations are indeed a better metrics for quantifying uptake of organic chemicals by terrestrial biota (mostly invertebrates), a literature search was performed and the available evidence in favor of any metrics was gathered in the context of a mandate of the European Food Safety Authority. It is concluded that knowledge on uptake routes of contaminants by soil invertebrates is far from complete. Overall it is clear that uptake of organic contaminants depends on species, soil type, and the chemical properties. The mode of exposure of soil invertebrates is determined by the way animals are in contact with their local environment. Morphology, physiology, and behavior are important factors in this respect, as is the mode of uptake of food, water, and oxygen. The contribution of oral uptake may vary within a specific taxon but for soil organisms in close contact with the soil solution, pore water–mediated uptake is in general the dominant pathway and it is commonly modified by soil specific ageing and speciation, and by specific factors of the organisms, such as nutrition status. Residual uptake appears to be the most important uptake route following pore water–mediated uptake. It is likely that in this case, too, pore water is involved as carrier in or at the surface of the soil in which the chemicals are dissolved. Intraspecies (especially between different life stages) and interspecies variances (e.g., size and ecological preferences) will most likely modify the actual contribution of potential exposure pathways, and a distinction must be made between hard-bodied and soft-bodied organisms. Hard-bodied organisms rely for uptake of oxygen and water on specialized organs, whereas water (pore water) and oxygen are mainly taken up via the skin in soft-bodied organisms. Hard-bodied animals are nevertheless in contact with pore water, as shown for spiders, woodlice, and collembolans. Uptake of nutrients and chemicals is possible for all invertebrates via their food, and this may be an important route in case of food sources in which high concentrations of chemicals are present. The assimilation efficiency will however depend on species-specific properties of the digestive tract and no general conclusions are to be generated in this respect. [ABSTRACT FROM AUTHOR]

A study of the availability of pesticide-treated seed on arable fields was performed. The research was carried out in three different areas of The Netherlands (soil types ranging between sand and heavy clay) and included the following topics: drilling techniques, soil conditions, location on the field and spillage. The results show that there is a large variation among the various crops in the percentage of seed remaining on the soil surface. This is mainly caused by differences in drilling techniques and soil conditions. The percentage of surface seeds after standard drilling is approximately four times higher than after precision drilling. The best correlation for the impact of soil conditions was found for the overall measure of clod weight. Large differences in seed densities (factor of 3.5) were found between the headland and the field centre. Spillage occurred in most crops investigated, with an average of two spills per field. Based on the field data it is recommended to use in the current risk assessment for birds and mammals the following percentages of seed remaining on the soil surface: 0.5% for precision drilling, 3.3% for standard drilling in spring and 9.2% for standard drilling in autumn. [ABSTRACT FROM AUTHOR]