Case Study for Combining Effects and Exposure Studies

Case Study for Combining Effects and Exposure Studies 

As an example for the use of field data (in this case, a combination of a generic study, a field-effect study and a field residue study), the following case study is presented the agricultural scenario was a spray application of an organothio-phosphate insecticide in arable crops. Due to the inherent bird toxicity (e.g., LDjq 10 mg a.s./kg bw) estimated according to the EU Guidance Document SANCO/4145/2000, the acute TER is 0.5 within a Tier 1 risk assessment [1]. Since the trigger value within the EU ( 10) is not met, a refined risk assessment is necessary. As a consequence, a field study was conducted to derive refined exposure parameters for small insectivorous birds in an arable crop. Furthermore, the effects of the product on the population were recorded. The field work of the 

Monitored compoimd-spedfic data were the survival rates of adults and nestlings within the treated area (effects imder field conditions). Furthermore, residues in/on food items (arthropod prey) within treated fields (term C within the ETE-calculation) were analyzed in arthropod samples collected with suitable methods (e.g., pitfall traps, inventory spray) from treated fields. 

Based on data for a relevant indicator species, refined values for body weight, fraction of diet obtained in treated area (PT) and fraction of food type in diet (PD), a refined TER was calculated. As a result of the intensive field work, a set of realistic dietary exposure levels could be calculated for the birds which were observed within 1-10 days after the application of the respective pesticide, resulting in acute TER-values between 12 and 697. These acute TER values, which substantially exceed the value obtained in the Tier 1 assessment (acute TER 0.5), are all higher than the trigger of 10 set by Annex VI of Directive 91 /414 EEC for a refined risk assessment. Furthermore, pesticide exposure did not adversely affect avian survival (neither adults nor young birds). In conclusion, an unacceptable risk for birds following the use of the compound under practical field conditions is not to be expected. 

Field studies are highly recommended to provide ecological (generic) data on potentially exposed wildlife species for refined risk assessments. As can be seen from the case study, the required input data (generic and/or compound specific) on relevant species and crop scenarios can be generated by tailor-made field studies. These quantitative data are very suitable for ETE-calculations. Therefore, specific data obtained from field studies may contribute to more scientific and realistic risk evaluations. 

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