Applica-tion rate
Table E.3b Short-term risk for birds
Short-term ETE
TER Substance FIR / bw RUD
Applica-tion rate
Table E.3c Long-term risk for birds
MAF
Long-term ETE
TER Substance FIR / bw RUD
Applica-tion rate
Taking the results in Table E.3 into account, it appears that a risk to birds for the proposed uses cannot be excluded, as apart from the acute risk, the short- and long-term risk are not acceptable. Hence, for those uses that pose a risk it must be demonstrated by means of an
adequate risk assessment that there are no unacceptable effects under field conditions after the application of the plant protection product according to the proposed GAP.
Revised arthropod residue data are available in the new GD for birds and mammals (EFSA Journal 2009; 7(12):1483). Based on the state of the art the Ctgb agrees to use the revised arthropod residue data as evaluated in the new GD as a higher tier in national risk
assessments which are performed according to Sanco/4145/2000.
Other aspects of the new GD are used only in risk calculations based fully on the EFSA GD, i.e., the Sanco and the EFSA guidance documents are not mixed otherwise.
The revised RUD values for arthropods are given in Table E.4 below . Furthermore, a
generic DT50 of 10 days can be used for arthropods. Based on this value, an ftwa of 0.53 can be used for metobromuron.
Table E.4 Revised RUD values for arthropods
Crop/category of insects Crop stage mean 90th percentile Ground dwelling invertebrates
without interception1
ground directed applications
7.5 13.8
Ground dwelling invertebrates with interception2
applications directed to crop canopies
3.5 9.7
Insects (foliar dwelling invertebrates3)
whole season 21.0 54.1
1 applications on bare soil, or ground directed applications up to principle growth stage 3, ground directed applications in orchards/vines (e.g. herbicides)
2 applications directed to crop canopies (orchards/vines), ground directed applications on top of crops with principle growth stage of 4 or greater
3 no data are available for canopy dwelling invertebrates in winter or before the leaves appear (interception would be less)
According to Table E.4 the revised RUD value will be 13.8 instead of 29. This results in an ETE of 28.7 and 15.2 for the short- and long-term ETE, respectively and in TERs of >9.55 and 1.42, respectively. Thus, the risk to insectivorous birds is still not acceptable.
In reaction to the observed risk, the applicant submitted a risk assessment based on the new guidance for birds and mammals (EFSA Journal 2009; 7(12):1483). Therefore, a full risk assessment according to the EFSA (2009) GD is performed.
However, although it is a bare soil application, Ctgb questioned whether exposure to plant eating birds could be excluded. The following statement was presented by the applicant.
Statement applicant
“Relevance of post-emergence risk assessment scenarios”
The application of metobromuron will take place shortly after the preparation of the seed bed and planting of the seed potatoes.
The cultivation of potatoes is a highly industrialised process. The ideal seedbed for potato planting is uniformly firm, has appropriate soil moisture, is free from competing vegetation and is well-packed underneath with small surface clods to prevent soil erosion.
Conventionally, seedbeds are prepared in two phases, first with ploughs and disks to turn over the upper layer of the soil, bringing fresh nutrients to the surface, while burying weeds, the remains of previous crops, and both crop and weed seeds, allowing them to break down.
It also provides a seed-free medium for planting. In modern use, a ploughed field is typically left to dry out, and is then harrowed before planting to smooth and firm the seedbed with harrows or packers. Potatoes are then planted with automatic planters that put tubers into the correct depth and cover them with soil. Shortly after planting, the ground is gone over in order to form ridges around potatoes (Figure 5-1). Before the plants emerge, the ground is typically sprayed with an herbicide to make sure it stays free from competing vegetation. The
time between planting and emergence is the most delicate period of potato crop (van der Zaag 1992, Entrup and Oehmichen 2000, St John et al. 2011).
Figure 5-1 Typical pre-emergent potato field
After seedbed preparation fields are far from being optimal feeding grounds for birds and mammals. Fields are free from green vegetation. Seeds are buried under because a largely seed-free medium for planting crops is needed. First weeds might emerge within some time;
however, they will not contain high residues of metobromuron and will not produce seeds within a short time period. Applications of herbicides against emerging weeds between planting and emergence of potatoes further reduce the availability of green plant matter and seeds as food for animals. Metobromuron is primarily applied to avoid emergence and growth of newly emerging weeds, thus giving the emerging potato plants a competitive growth advantage.
Hence, bare soil fields after planting potatoes offer a very limited amount of seeds to
granivorous species. They further provide no cover for resting or nesting and no green plant material or foliar arthropods as food for herbivorous, omnivorous and insectivorous animals.
Moreover, residues in newly emerging potato plants or new weeds will be substantially lower compared to the EU default RUD value of 28.7 mg/kg in non-grass herbs following an early post-emergence application. In the potato metabolism study (application rate 2.5 kg a.s./ha) total residues (measured as 14C) in leaves increased with time and represented maximum of 1.75 mg/kg parent equivalent by day 63 after application before to declining to 0.17 mg/kg at harvest (111 days after application). It can therefore be concluded that post-emergence risk scenarios are not relevant for the pre-emergence application of metobromuron in potatoes.
Response Ctgb
The applicant submitted a sound statement. The Ctgb agrees and exposure to plant eating birds can be excluded for the proposed uses. In addition, regarding a granivorus species, the Ctgb will follow the existing guidelines and regards the linnet as a focal species for
granivorous birds.
Acute risk to birds
The screening step for the current application uses is presented in table E.5a.
Table E.5a Indicator species and default values for the acute risk assessment
Use Crop / crop group Indicator species
(screening step) Shortcut
value MAF90
Bare soil Bare soil and hop Small granivorous bird 24.7 -
Depending on the crop category, different bird indicator species are chosen. Acute “shortcut values” (based on 90th percentile residues) according to Table 6 of the Birds and Mammals Guidance document (2009) were considered for the screening assessment. “Daily dietary
dose” (DDD) values were calculated by multiplying respective “shortcut values” with the corresponding highest single application rates in kg/ha. “Multiple application factors” for 90th percentile residue data (MAF90) were selected from Table 7 of the guidance document. The DDD values were calculated according to the following equation: DDD = application rate [kg /ha] × shortcut value × MAF90. The TER value = LD50 / DDD. TER values for birds for the worst-case uses, considering default values, are shown in Table E.5b.
Table E.5b Screening assessment, TERA calculation
Indicator species Small granivorous bird
Crop /scenario Bare soil
Max. single application rate [kg a.s./ha] 2.0
Shortcut value 24.7
frequency 1
Interval [d] -
Multiple application factor for 90th percentile residue data (DT50 = 10 -
Daily dietary dose 49.4
Endpoint (LD50) [mg a.s./kg b.w.] 1429
TER 28.9
Trigger value [TER] 10
Refinement required No
* similar as with 1.44 kg a.s./ha and ∞ applications and an interval of 7 days.
Taking the results in Table E.5b into account, it appears that bare soil meet the standards laid down in the RGB. Therefore, the acute risk to birds is acceptable.
Long-term risk to birds
The screening step for the current application uses is presented in table E.6a.
Table E.6a Indicator species and default values for the long-term risk assessment
Use Crop / crop group Indicator species
(screening step) Shortcut
value MAFmean
Bare soil Bare soil and hop Small granivorous bird 11.4 -
Depending on the crop category, different bird indicator species are chosen. Shortcut values (based on mean residues) according to Table 10 of the Birds and Mammals Guidance document (2009) were considered for the screening assessment. The “daily dietary dose”
(DDD) values were calculated by multiplying the “shortcut values” with the respective highest single application rates of the active ingredient in kg/ha and a time-weighted average factor (TWA) of 0.53 – this factor estimates time weighted exposure over 21 days assuming a default DT50 of 10 days. “Multiple application factors” for mean residue data (MAFm) were selected from Table 11 of the guidance document.
The DDD values were calculated according to the following equation: DDD = application rate [kg / ha] × shortcut value × fTWA × MAFm. The TER value is NOEL or NOAEL / DDD. TER values for birds for the worst-case uses, considering default values, are shown in Table E.6b.
Table E.6b Screening assessment, TERLT calculation
Indicator species Small granivorous bird
Crop / crop group Bare Soil
Max. single application rate [kg a.s./ha] 2.0
Shortcut value 11.4
TWA 0.53
Frequency 1
interval -
Multiple application factor for mean residues -
Daily dietary dose 12.1
Endpoint (NOEL) [mg a.s./kg b.w./d] 21.6
TER 1.79
Trigger value [TER] 5
Refinement required Yes
Taking the results in Table E.6b into account, it appears that the bare soil scenarios do not meet the standards laid down in the RGB. Therefore, a first tier risk assessment is
nescessary.
First tier chronic risk assement bare soil
Table E.7 Long-term risk for birds in bare soil – first tier risk assessment
DDD Compound
(application time)
Generic focal species
Toxicity [mg/kg
bw/d] Appl.
rate [kg/h a]
SV MAFm TWA
DDD TER Trigger
potato (1 application, 2.0 kg a.s./ha, BBCH 00-09) BBCH < 10 Small
granivorous bird "finch"
11.4 - 0.53 12.1 1.8 5
BBCH < 10 Small omnivorous bird “lark”
8.2 - 0.53 8.69 2.5 5
BBCH < 10 Small insectivorous bird “wagtail”
21.6 2.0
5.9 - 0.53 6.25 3.5 5
The table above shows that the long-term risk to small granivorous, omnivorous and
insectivorous birds is not acceptable. Therefore, a higher tier risk assessment is necessary.
Refined chronic risk assessment birds
The applicant proposed refinement of the reproductive endpoint, focal species, FIR/bw and PT. Furthermore, qualitative arguments on food availability on treated fields (bare soil
application), dehusking, avoidance, diet composition for insectivorous birds, residue levels on insect prey and breeding time were made.
Reproductive endpoint Response applicant
The toxicity data from the chronic bird study (Rodgers, 2010) are considered more relevant for the reproductive risk assessment than the surrogate endpoint for parental toxicity as the LD50/10 of 143 mg a.s./kg bw/d is greater than the NOEL.
The No Observed Effect Level (NOEL) for reproduction in the study of Rodgers (2010) was set at 240 ppm (corresponding to a daily dose of 22.1 and 21.6 mg a.s./kg bw/d for females and males, respectively). This endpoint is based on a statistically significant difference in total number of eggs laid per female (adjusted for laying time) at the next higher
concentration of 384 ppm (corresponding to 36.2 or 34.2 mg a.s./kg bw for males and females, respectively). The total number of eggs laid per female (excluding non-treatment related injured birds) at 384 ppm was 42 eggs, compared to 62 eggs in controls. The number of eggs in the higher treatment group (614 ppm) was 41.
However, for the following parameters investigated in the study, no dose-response and no significant effects were observed up to the highest concentration of 614 ppm tested:
proportion of damaged eggs, eggshell thickness, viable embryos as a proportion of eggs set on day 0, live 3-week embryos as a proportion of those viable, normal hatchlings as a proportion of live 3-week embryos, normal hatchlings as a proportion of viable embryos, 14-day survivors as a proportion of normal hatchlings, 14-14-day survivors as a proportion of eggs laid.
When considering the number of 14-day survivors per female adjusted for laying time, no statistically significant difference to controls was observed up to a concentration of 384 ppm (corresponding to 36.2 and 34.2 mg a.s./kg bw/d for males and females, respectively). In contrast to the number of eggs laid defining the NOEL, the output of surviving chicks is of higher ecological relevance. Based on these results, it is therefore concluded, that the overall reproductive success of birds dosed up to a food concentration of 384 ppm is not affected by Metobromuron.
Furthermore, the results for chick bodyweights indicate that the vitality of surviving chicks is not affected. Only at the highest concentration of 614 ppm, and at the respective
concentration only the initial body weight, but not the body weight for 14 day old chicks, exhibited a significant effect and the bodyweight of 14-day old chicks does not indicate a dose-relationship.
The results related to parental toxicity (adult body weight and food consumption) suggest, that the observed effects in numbers of eggs laid are not to be interpreted as a direct effect on reproduction, but as an indirect effect caused by effects on parental food consumption.
Whereas effects on body weight in the period prior to egg laying are statistically significant only at 384 and 614 ppm, a dose-response relation indicates that also at lower
concentrations effects on body weight, even if not statistically significant, may account for the reduced egg production. Furthermore, effects seen in body weight are paralleled in a
reduction of consumed food over the dosing period, again following a dose-response relationship and with statistically significance for the two highest concentrations.
In accordance to EFSA (2009), short-term dietary data may also be considered if available.
In the 8-day dietary study by Sachsse and Ullmann (1975d) during the whole treatment and observation period no toxic symptoms were seen. An LC50 could not be determined.
However, considering that no birds died up to and including a diet concentration of 10000 ppm (corresponding to 192.1 mg a.s./kg bw/d), a very low dietary toxicity can be assumed.
However, reduced food consumption as well as reduced body weights were also observed in this 8-day dietary study. Egg production in the groups exposed to 6’000 and 10’000 ppm after the first day was stopped, confirming the secondary effect on reproductive performance.
However, no toxic symptoms were observed during the whole study period. This suggests an avoidance reaction of birds, rather than any toxicity of the active substance.
Thus, the effects on egg production can be attributed to parental effects. In accordance to the guidance document (EFSA 2009), purely parental effects observed in reproduction studies can be ignored, as the surrogate endpoint (i.e. LD50/10) obtained from the acute oral toxicity study represents a more appropriate indicator for the NOAEL for parental effects with potential to disrupt reproduction. The fact that reduced numbers of eggs are a secondary
(indirect) effect is further corroborated by literature data. It is well known that clutch sizes of birds are correlated with the availability of food (see e.g. Monaghan and Nager, 1997, Both et al., 2000, Robb et al., 2008, Oro et al. 1999 and Castro et al., 2003).
The review paper by Monaghan and Nager (1997) suggests that ‘egg production is an expensive process’. This is ‘corroborated by many correlative and experimental studies in wild birds showing that it [egg production] is closely linked to food supply’. This is in line with life history theory, ‘that clutch size is ultimately determined by the number of young that parents can provide with food’. As an example, in Audoun’s gull (Larus audounii) as expected, food availability influenced egg volume, clutch size and breeding success.
Likewise, according to Both et al. (2000), density is causally affecting clutch size as well as other reproductive parameters (as e.g. found for great tits). ‘In this species it has been suggested that clutch size is adjusted [among others] to the amount of food during egg laying’ (literature cited in Both et al., 2000). Density-dependent clutch size is stated to be ‘a behavioural response of individual females adjusting their clutch size to changes in density’.
The density-dependent effects on clutch size in the study by Both et al. are ‘likely to be caused by competition for resources’. Further evidence for clutch sizes depending on food availability is provided by experiments with supplementary feeding. A review on the effects of artificial food supplementation is provided by Robb et al. (2008). Because of the ‘acute need for energy during egg development and laying’, supplementary feeding ‘is likely to affect avian fecundity’, also by way of increasing the numbers of eggs laid. Food supplementation, for example, also had a positive effect on clutch sizes in the endangered Hihi, Notiomystis cincta (Castro et al., 2003).
The mechanism mediating effects of stress (as by food deprivation) on the numbers of eggs laid is via hormones. Thus, ‘hormones like prolactin and corticosterone can exercise a crucial influence on the behaviour of birds in the breeding season and therefore on their
reproductive success’ (see Quyang et al. 2011). According to these authors, who studied the correlation between hormone concentrations and breeding success in house sparrows, hormon levels are not only relevant during the breeding season. They also ‘dictate’ […] ‘how many eggs a breeding pair will lay’ […]. Accordingly, corticosterone can suppress
reproduction if birds experience significant stress, whereas the hormone prolactin stimulates reproduction (‘it controls the number of eggs per clutch and the intensity of brood care’).
Likewise, for example Silverin (1986), who studied the Pied Flycatcher, reports that ‘an experimentally increased plasma level of corticosterone during the nestling period drastically reduced reproductive success’. According to literature cited in Poisbleau et al. (2009), ‘poor environmental and individual conditions lead to a chronic stress response, which affects basal plasma levels of corticosterone’. However, what is more important in this context is the fact, that, ‘additionally, acute stressors’ […] ‘cause a short-term acute stress response with a rapid increase of plasma corticosterone. This indicates that stress over a short time period can rapidly result in reduced egg numbers.
In conclusion, the feeding status of female birds has an effect on the numbers of eggs produced. This can be interpreted as a behavioural response of birds, supposedly mediated via hormones that can be, from an evolutionary point of view, explained as an attempt to adjust reproductive parameters to environmental conditions.
Short-term vs. long-term effects on reproduction
Accordingly, it is argued that the reduction in numbers of eggs laid in the chronic bird study (Rodgers 2010) in the absence of any toxic effects even at exaggerated feed concentrations is an adaptive (behavioural) response to the reduced food consumption. This leads to the conclusion that the numbers of eggs laid might in fact be a short-term effect, as corroborated by the results of the short-term dietary effect study (Sachsse and Ullmann 1975d). However, in accordance with the above argumentation, neither is the reduced egg numbers observed in the study an ecologically relevant effect (the number and vitality of 14-day survivors are not affected), nor is the reduction qualified as a real reproductive effect but an indirect behavioural response not to be expected in the field (where birds can avoid food deprivation by feeding somewhere else).
In the absence of any ‘reproductive effects’ up to and including the proposed NOAEL of 34.2 mg a.s./kg bw/d which was obtained under constant dosing during the whole study period, short-term effects are not likely to influence reproductive parameters. Therefore, it is justified to base the reproductive risk assessments on the time-weighted average exposure by using the default twa-factor of 0.53 (reflecting the default DT50 of 10 days and an observation period of 21 days).
Ecological relevance
Taking into consideration the unrealistic exposure scenario of reproduction studies with dosing of animals at constant concentrations over the whole study period without accounting for the residue dissipation in the actual field situation, the effects on food consumption as well as the secondary effects on body weight and egg production are not considered to be of ecological relevance. No toxic effects on birds have been observed and reduced body weight can likely be attributed to an avoidance reaction. As under field conditions birds are not
Taking into consideration the unrealistic exposure scenario of reproduction studies with dosing of animals at constant concentrations over the whole study period without accounting for the residue dissipation in the actual field situation, the effects on food consumption as well as the secondary effects on body weight and egg production are not considered to be of ecological relevance. No toxic effects on birds have been observed and reduced body weight can likely be attributed to an avoidance reaction. As under field conditions birds are not