Demographic Determinants of Residue Profiles of Fungicidal Compounds in Common Voles (Microtus arvalis) under Semi-Natural and Natural Conditions

Abstract

Environmental risks from plant protection products (PPPs) need to be assessed to ensure safe use. The risk assessments are generally carried out using the common vole as a focal species with conservative theoretical estimates of external exposure. These are then compared to dose-related toxicity endpoints established in toxicity studies, often with laboratory species. The aim of the present study was to determine the actual internal dosimetry of PPPs' active ingredients (AIs) in a population of common voles to provide the basis for informed higher tier risk assessment. As a proof of concept, two fungicidal AIs (fludioxonil and cyprodinil) were investigated using a range of application methodologies. Individuals were treated using oral gavage application (AI dose: 100/200 mg/kg) and fed treated grass (AI sprayed at 2 kg/ha) under laboratory, semi-natural, and natural conditions. Our results show that demographic factors play a significant role in the individual residue profile and that age structure is a key aspect that determines the overall exposure risk of a population. These results are consistent from laboratory to field conditions. Future approaches could establish dose-residue relationships that are reflective of natural food intake rates in wild common vole populations in the risk assessment of PPPs.

Keywords: generic focal species; registration; risk assessment; toxicokinetics.

Figure 1

Graphical representation of the effect of individual body weight on grass consumption. The y-axis represents the multiples of individual body weight that were consumed per day. Study data means are presented by a solid line. Predicted values, not covered by original data set, for heavier individuals are presented by a dashed line.

Figure 2

Periodogram of vole activity displaying the frequency (in hours) of above-ground activity in all four enclosures as well as their mean value. Spectral density on the y-axis represents the dimensionless signal strength, here above-ground vole activity, in relation to the frequency.

Figure 3

Single factor effects of time on individual AI residues (A,C cyprodinil; B,D fludioxonil) from different application methodologies (A,B oral gavage; C,D grass feeding) as a result of generalized linear mixed modeling. Differences in the temporal scale of model projections reflect different trial lengths.

Figure 4

Single factor effects of individual weight on AI residues (A cyprodinil; B fludioxonil) from different application methodologies as a result of generalized linear mixed modeling. Differences in the temporal scale of model projections reflect different weight distributions within the population.