Table 16.

Sources of uncertainty and their effects on the risk assessment for amphibians and reptiles

Source of uncertainty in the current risk assessment	Potential to be protective	Potential to be underprotective	Impact on the risk assessment for amphibians and reptiles
Variability in toxicological sensitivity between species within one group of organisms	Variability between species is very narrow	Variability between species is very large	Variability in species unknown → further data needed
Representativeness in toxicological sensitivity of surrogate species for other species within one group of organisms	Surrogate species is a sensitive species	Surrogate species is not a sensitive species	Sensitivity of tested species (e.g. X. laevis) unknown → further data needed
Toxicological sensitivity of tested life stage	Most sensitive life stage is tested	Tested life stage does not cover sensitivity of other life stages	Sensitivity of different life stages (esp. adults) unknown, possibly compound specific (e.g. effects on eggs) → further data needed
Ecological relevance of observed effects in the toxicological studies	Critical effects have been addressed directly	Critical (e.g. endocrine) effects may remain unnoticed	Not all effects are adequately addressed. Sublethal studies needed to address, e.g. metamorphosis and immunosuppression
Study length to observe effects	Study duration long enough to observe critical and relevant effects	Study duration too short to observe latency of effects	Short‐term exposure of juveniles in the aquatic may lead to long‐term effects in terrestrial adults
Route of exposure addressed in the study design	Relevant route of exposure adequately addressed in the study design	Relevant route of exposure not adequately addressed in the study design	Dermal exposure currently not adequately addressed
Representativeness of laboratory studies and exposure models for the field	Laboratory studies and exposure models are representative for the field	Indirect effects occurring in the field are not adequately addressed in the studies. Exposure models are no representative	Extrapolation needs to be checked against field studies
Interaction with other non‐regulated stressors	No interactions occur	Interactions are relevant	Not addressed, e.g. Pesticide exposure may increase susceptibility to diseases
Multiple regulated stressors in a temporal scale (e.g. multiple applications of different products on one field)	Other products in spray schedules have no increased adverse effect	Additive or synergistic adverse effects due to treatments with several products one after the other	Not addressed. Particularly relevant for species living within the field (e.g. reptiles) or moving across the fields (e.g. amphibians)
Multiple regulated stressors on a spatial scale (e.g. multiple inputs in a catchment)	Habitat lies solely in field and adjacent off‐crop areas	Habitat is larger than one field, resp. receives input from several sources	Spatial scale relevant for aquatic species. Habitat range needed for terrestrial species is not addressed → further data needed
Location/proximity of surface water body to the field	Distance from field to water body is equal or greater than assessed	Pond may be situated in the middle of a field	Distribution of aquatic amphibian habitats needed and exposure models need to be adjusted
Size of standard water body (30 resp. 100 cm deep)	Depth of natural water bodies is equal or greater (90th percentile)	Habitats are very shallow temporary water bodies of a few cm depth	Description of aquatic amphibian habitats needed and exposure models need to be adjusted
Distribution of the test substance in test vessel to determine relevant exposure concentration	Substance is distributed in the field as in the laboratory study	Patches with increased concentration due to poor circulation in standing or slow flowing waters	Relevant exposure concentration needs to be modelled
Assessment of different routes of exposure separately	Exposure models are worst‐case enough so that different routes of exposure do not need to be combined	Exposure of an individual may be orally, dermally and by inhalation	Exposure models need to be adjusted to account for combined exposure routes of an individual
Assessment of exposure in different systems (aquatic and terrestrial) separately	Species have distinct, separate habitats	Exposure of an individual in the aquatic and terrestrial system concurrently	Exposure models need to be adjusted to account for combined exposure in water and on land
Health status of laboratory animals in comparison to animals in the field	Test Animal is equally healthy in the laboratory and the field	Pre‐exposure in the field increases sensitivity of the animal	Effect currently poorly understood (possibly development of resistance or increase in sensitivity) → further data needed
Population spatial structuring	The population exists as a spatially undifferentiated population not relying on fragile spatial dynamics for long‐term survival	The population exists as an unstable metapopulation or source‐sink population that can easily be disrupted	Not addressed. Most amphibians and many reptiles exist in spatially structured populations potentially subject to disruption
Long‐term year on year effects	There is no effect of previous year's impacts, i.e. full recovery within a season	There are carry‐over effects of impacts from previous years increasing the vulnerability in the following years	Not addressed. Amphibians and reptiles are long‐lived, increasing the chance of cumulative effects over a number of years building up