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This brief communication reports on the main findings of the LEMTOX workshop, held from 9 to 12 September 2007, at the Helmholtz Centre for Environmental Research (UFZ) in Leipzig, Germany. The workshop brought together a diverse group of stakeholders from academia, regulatory authorities, contract research organizations, and industry, representing Europe, the United States, and Asia, to discuss the role of ecological modeling in risk assessments of pesticides, particularly under the European regulatory framework. The following questions were addressed: What are the potential benefits of using ecological models in pesticide registration and risk assessment? What obstacles prevent ecological modeling from being used routinely in regulatory submissions? What actions are needed to overcome the identified obstacles? What recommendations should be made to ensure good modeling practice in this context? The workshop focused exclusively on population models, and discussion was focused on those categories of population models that link effects on individuals (e.g., survival, growth, reproduction, behavior) to effects on population dynamics. The workshop participants concluded that the overall benefits of ecological modeling are that it could bring more ecology into ecological risk assessment, and it could provide an excellent tool for exploring the importance of, and interactions among, ecological complexities. However, there are a number of challenges that need to be overcome before such models will receive wide acceptance for pesticide risk assessment, despite having been used extensively in other contexts (e.g., conservation biology). The need for guidance on Good Modeling Practice (on model development, analysis, interpretation, evaluation, documentation, and communication), as well as the need for case studies that can be used to explore the added value of ecological models for risk assessment, were identified as top priorities. Assessing recovery potential of exposed nontarget species and clarifying the ecological relevance of standard laboratory test results are two areas for which ecological modeling may be able to provide considerable benefits.

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Different cholinesterases from brain and body muscle of the fish three‐spined stickleback (Gasterosteus aculeatus) were investigated concerning their potential use in the biomonitoring of organophosphate insecticides (OPs). Stickleback brain contained acetylcholinesterase (AChE) but no butyrylcholinesterase (BChE). Body muscle contained both AChE and BChE. In vitro, body muscle BChE was three orders of magnitude more sensitive than brain or body muscle AChE to the OPs paraoxon and dichlorvos. In 1998, cholinesterase activities were recorded in stickleback from eight streams differing in pesticide contamination. Automated on‐site samplers that selectively collect water during runoff events were used to obtain water samples for pesticide analysis. The OP parathion was found in stream water sampled during runoff events in five cases. The variation of brain and body muscle AChE activity between streams was not related to water contamination by pesticides. Body muscle BChE was strongly decreased (>85%) in stickleback collected at all streams with previous parathion contamination events. A significant decrease in BChE (78%) occurred also, however, at one stream where other pesticides but no OPs were found. Because stickleback AChE and BChE differed strongly in their in vitro sensitivity and their response in the field, these enzymes should be considered separately in studies with fish.

Three test-plot series have been performed to gather information on runoff of sulfonamides from manured arable and grassland after sprinkler irrigation. To prepare test slurries with defined aged residues, liquid bovine manure was fortified with sulfadiazine, sulfadimidine, and sulfamethoxazole and stored short-term. After test-slurry application, the arable land was treated by soil cultivation before irrigation, and the manured grassland was irrigated directly with 50 mm h(-1) for 2 h. The runoff suspensions were sampled at 5- to 10-min intervals, separated into aqueous phase and suspended matter and residue analyzed. Higher runoff emissions were found from manured grassland plots. The discharge volumes ranged from 106 to 252 L and the total runoff emissions ranged from 13 to 28% of sulfonamides applied initially. Within the first 20 min of the irrigation period that represented a rainfall of 17 mm, emissions, on average, were 4%. The loads of sulfonamides predominantly occurred in the runoff water. The only emissions via suspended matter, on average, were 0.02%. On arable land, however, the runoff was reduced by soil cultivation. Discharge volumes and sulfonamide emissions were 36 to 128 L and 0.1 to 2.5%, respectively. Despite the high-intensity sprinkler irrigation, major emissions did not occur until a 60-min delay.