Table 11.
Uncertainty analysis for exposure estimations
| Source of uncertainty | Potential to over‐ (−)*or underestimate the exposure (+)** | Explanation |
|---|---|---|
| Uncertainty analysis for oral exposure estimates | ||
| Food intake rates (FIR) used in the oral exposure estimates | −/+ | The food intake rate is based on a small bat species which can be considered representative for small European bats. Some European bats such as Pipistrellus pipistrellus are smaller and may have higher FIRs but the majority of European bats are larger. The FIR was measured in lactating bats and hence covers the life stage with highest FIRs. Further studies measuring FIR or energy requirements of bats may broaden the database and the resulting FIRs may change to higher or lower values but the magnitude of change is likely to be low |
| Residue per Unit Dose (RUD) for residues in insect food items | −−/+ |
The residues for flying insects were taken from a study where insects most relevant as food items for bats were collected. The study was conducted with a substance which has no acute toxic mode of action for insects and as such may be well representative for substances with low toxicity to insects. However, the data are from one study only and hence broadening the database may lead to a lowering or increase of the RUD For substances which are highly acutely toxic to insects, the real residues are most likely lower as the insects with high pesticide load will not be able to fly anymore and hence will not be available to bats feeding on flying insects |
| Drinking water demand | −/+ | The drinking water demand was taken from a study with lactating females of a small bat species. The life stage with highest drinking water demand is therefore covered. However, it is only one study and if the database would be broadened the values for the drinking water demand could be increased or reduced but the magnitude of this change is likely to be low |
| Oral exposure by grooming | −−−/+++ | Grooming is a potential source of oral exposure from residues collected on the fur and wings of bats. The available data were not sufficient to provide an estimate of oral exposure from grooming. There is indication that this exposure route could be substantial since a method to control vampire bats is even derived from the natural behaviour of social grooming |
| Oral exposure of pups based on a measured excretion of 83% of residues in milk | −− | The estimate of exposure of pups from uptake of residues in milk is based on an excretion of 83% of residues via milk. This measurement is from one study only. Broadening the database may lead to an increase or decrease of this value |
| Dermal exposure estimates | ||
| Duration of exposure of 1 min | +++ | If bats forage in a field where a pesticide is applied then the duration of exposure is likely to be greater than for 1 min |
| Duration of exposure of 2 h | −−− | A typical foraging flight of an aerial hawker lasts for 2 h. These 2 h could be spent in the vicinity of the treated field. However, it is unlikely that it will be exposed continuously for 2 h at high air concentrations |
| Distance to spray boom | −−− | In the dermal exposure estimates, it is assumed that the bat is very close to the sprayer. In reality, the bat will be only for a short time close to the sprayer each time when it is passing by the machinery during the foraging flight |
| Pesticide concentrations in air | −−/++ | The calculation of more accurate air concentrations and the path of the bat takes through the spray cloud may lead to higher or lower exposure |
| All spray droplets in the volume of air passed through by the bat ends up on the bat surface (calculation methods 1 and 2) | − | In reality, not all spray droplets in the volume of air the bat is passing through will end up on the surface of a bat |
| All spray droplets in the drift at 1 m away from the sprayer end up on the upper surface of the bat over the distance covered during bat flying time (calculation method 3) | +/− | In reality, not all spray droplets in the area covered by the bat flight will end up on the bat surface but on the other hand bats may be exposed to some droplets from the spray which would deposit further away than 1 m from the sprayer |
| Inhalation exposure | ||
| Duration of exposure of 1 min | +++ | If bats forage in a field where a pesticide is applied, then the duration of exposure is likely to be greater than for 1 min |
| Duration of exposure of 2 h | −−− | A typical foraging flight of an aerial hawker lasts for 2 h. These 2 h could be spent in the vicinity of the treated field. However, it is unlikely that it will be exposed continuously for 2 h at high air concentrations |
| Distance to spray boom | −−− | In the dermal exposure estimates, it is assumed that the bat is very close to the sprayer. In reality, the bat will be only for a short time close to the sprayer each time when it is passing by the machinery during the foraging flight |
| Pesticide concentrations in air | −−/++ | The calculation of more accurate air concentrations and the path of the bat takes through the spray cloud may lead to greater or lower exposure |
| Respired volumes | −/+ | Data on respiratory volumes were available for four bat species. The bats were large in comparison to European bat species. However, there was no indication that smaller bats would have greater respired volumes per kg bw and the available data for the four species were consistent. Therefore, it is not expected that respired volumes of European bats would be significantly different than the ones used in the exposure calculations |
| Inhalation of vapour not considered | +++ | Exposure to vapour can be significant for volatile substances and this may significantly increase inhalation exposure compared to inhalation of droplets |
*
’−’, ‘−−’, ‘−−−’ Low, medium or high potential to make the true exposure lower.
**
‘+’, ‘++’, ‘+++’ Low, medium or high potential to make the true exposure higher.