1,3,5-Triazine-2,4-diamine, N2-[(1R,2S)-2,3-dihydro-2,6-dimethyl-1H-inden-1-yl]-6-(1-fluoroethyl)-

Toxicity to aquatic plants other than algae

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

toxicity to aquatic plants other than algae

Type of information:

experimental study

Adequacy of study:

other information

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 221 (Lemna sp. Growth Inhibition Test)

GLP compliance:

yes (incl. QA statement)

Analytical monitoring:

yes

Vehicle:

no

Test organisms (species):

Lemna gibba

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

7 d

Duration:

7 d

Dose descriptor:

EC50

Effect conc.:

0 mg/L

Nominal / measured:

meas. (initial)

Conc. based on:

act. ingr.

Basis for effect:

frond number

Remarks on result:

other: 95% CI: 0.000351 - 0.000363 mg a.i./L)

Duration:

7 d

Dose descriptor:

NOEC

Effect conc.:

0 mg/L

Nominal / measured:

meas. (initial)

Conc. based on:

act. ingr.

Basis for effect:

frond number

Duration:

7 d

Dose descriptor:

EC50

Effect conc.:

0 mg/L

Nominal / measured:

meas. (initial)

Conc. based on:

act. ingr.

Basis for effect:

biomass

Remarks on result:

other: 95% CI: 0.000309 - 0.000446 mg a.i./L)

Duration:

7 d

Dose descriptor:

NOEC

Effect conc.:

0 mg/L

Nominal / measured:

nominal

Conc. based on:

act. ingr.

Basis for effect:

biomass

Conclusions:

The most sensitive response variable was frond number resulting in an overall ErC50 of 357 ng a.s./L in this study.

The lowest NOEC (76.2 ng a.s./L) was based on visual effects.

Reference 2

Endpoint:

toxicity to aquatic plants other than algae

Type of information:

experimental study

Adequacy of study:

other information

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 221 (Lemna sp. Growth Inhibition Test)

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Analytical monitoring:

yes

Vehicle:

no

Test organisms (species):

Lemna gibba

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

7 d

Nominal and measured concentrations:

Nominal concentrations of 3.92, 7.85, 15.7, 31.4, 62.8, and 126 ng a.s./L

Duration:

7 d

Dose descriptor:

EC50

Effect conc.:

0 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

act. ingr.

Basis for effect:

frond number

Duration:

7 d

Dose descriptor:

NOEC

Effect conc.:

0 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

act. ingr.

Basis for effect:

frond number

Duration:

7 d

Dose descriptor:

EC50

Effect conc.:

0 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

act. ingr.

Basis for effect:

other: total frond area

Remarks on result:

other: 95% CI: 0.0000741 - 0.0000883 mg a.i./L

Duration:

7 d

Dose descriptor:

NOEC

Effect conc.:

0 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

act. ingr.

Basis for effect:

other: total frond area

Findings:

Test conditions met all validity criteria, given by the mentioned guideline. The analytical findings of BCS-AA10717 found in freshly prepared test levels 31.4 – 126 ng a.s./L on day 0 in reference to nominal concentrations ranged between 91 and 100% (average 96%). In aged test levels on days 7 there were analytical findings between 87 and 97% (average 92%) of nominal.

Conclusions:

The most sensitive response variable (based on growth rates) was frond number resulting in (0-7-day)-ErC50 of 72.8 ng a.s./L in this study. The lowest NOEC (30.9 ng a.s./L) was based on both, visual effects and statistical data analysis of frond number and total frond area of plants.

Reference 3

Endpoint:

toxicity to aquatic plants other than algae

Type of information:

experimental study

Adequacy of study:

key study

Study period:

15 May - 08 Aug 2007

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Principles of method if other than guideline:

The aim of the study was to assess the initial and longer term ecotoxicological impact to a freshwater community and the subsequent recovery of the community at concentration levels relevant to the initial surface water PEC values (in the European Union) for a range of agricultural use scenarios.

GLP compliance:

yes

Analytical monitoring:

yes

Vehicle:

no

Test organisms (species):

other: mesocosm study

Details on test organisms:

Myriophyllum spicatum, Elodea nuttallii, Ranunculus circinatus, Ceratophyllum demersum, Potamogeton natans, Sagittaria sagittifolia, Salvinia natans and Lemna trisulca, Lemna gibbawere placed in each microcosm. The sediment introduced in the microcosms contained propagules of aquatic macrophytes (e.g Chara sp., Potamogeton perfoliatus, Potamogeton berchtoldii). The spontaneous growth of macrophytes in the volunteer section of the microcosms was allowed. In the preparatory phase of the microcosm experiment, however, some of these macrophytes were redistributed over the different microcosms to stimulate a similar development of all test systems. In addition, in the period 1 to 11 May 2007 all microcosms were seeded with a few shoots of the bioassay plants R. circinatus, E. nuttallii, (orginating from the experimental ditch facility), M. spicatum and C. demersum (originating from commercial suppliers) to also allow the development of these plants in the volunteer section of the microcosms.

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

70 d

Nominal and measured concentrations:

nominal: 0, 0.01, 0.032, 0.10, 0.32, 1.00, 3.20, 10.0 μg a.i./L

Duration:

70 d

Dose descriptor:

NOEC

Remarks:

overall

Effect conc.:

0 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

other: Several signs of toxicity depending on species.

Conclusion:

• Analysis of the test substance (AE1170437) in the water column 4 h after herbicide application indicated that all microcosms received the intended dose.

• In water samples from microcosms that received the intended treatment level of 0.01 μg a.s./L on average 139 % and 126 % of the intended dose was measured 4 hours and 2 days post application, respectively. Note that the limit of quantification (LOQ) of the detection method was 0.001 μg a.s./L. In water samples collected from microcosms that received higher concentrations on average 101 – 117 % of the intended dose could be measured 4 h post AE1170437 application, and 91 – 99 % was measured two days post herbicide application.

• Since the variability in concentration levels probably is higher during the first hours post herbicide application due to incomplete mixing, and the concentration of higher treatment levels can be measured with a higher accuracy, we decided to express the treatment-related responses observed in terms of the intended treatment levels (0.01 – 0.32 – 0.10 – 0.32 – 1.00 – 3.20 – 10.0 μg a.s./L).

• At the end of the experiment (day 69) approximately 14 – 23 % of the intended dose applied could still be detected in water samples.

• Of the macrophyte species investigated the lemnids (Lemna gibba, Spirodela polyrhiza) were more sensitive (NOEC of 0.01 μg a.s./L) than other growth forms of macrophytes.

• The fast majority of non-lemnid vascular plants started to show clear effects at the treatment level 0.1 μg a.s./L. At the treatment levels of 3.2 and 10 a.s./L recovery of affected macrophytes was not observed.

• In the microcosms macrophyte species were far more sensitive than phytoplankton and zooplankton taxa.

• In the microcosms community metabolism endpoints showed relatively minor treatment related effects. This might be explained by the fact that certain primary producers were not affected at all by the herbicide (e.g. Chara).

• Vascular plants that showed a relatively minor growth in controls, also were hardly affected by the test compound (e.g. Ceratophyllum demersum,

Ranunculus circinatus, Lemna trisulca).

• When considering all endpoints investigated in the microcosm experiment and in the associated bioassays (including the parallel bioassay with Lemna gibba),

the overall NOEC of the study is 0.01 μg a.s./L.

• When considering the endpoints that directly relate to the dynamics in exposure concentrations in the test systems (excluding the parallel Lemna gibba bioassay) the overall threshold level for effects can be set at 0.1 μg a.s./L, at least when considering an Effect class 2 response for Spirodela polyrhiza of minor importance.

• When excluding the responses of the lemnid macrophytes Spirodela popyrhiza and Lemna gibba, the NOEAEC level is 0.32 μg a.s./L, since at this treatment level only Effect class 2 responses were observed for Myriophyllum, Elodea

and a few algae. At the next higher treatment-level of 1.0 μg a.s./L long-term

responses without recovery were observed for the aquatic vascular plants

Myriophyllum spicatum and Elodea nuttallii.

Reference 4

Endpoint:

toxicity to aquatic plants other than algae

Type of information:

experimental study

Adequacy of study:

supporting study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

comparable to guideline study with acceptable restrictions

Qualifier:

according to guideline

Guideline:

EPA OPPTS 850.4450 (Aquatic Plants Field Study (Tier III))

GLP compliance:

no

Analytical monitoring:

yes

Vehicle:

no

Test organisms (species):

other: Elodea (Elodea canadensis), Sago pond weed, Long-leaf pondweed (Potamogeton pectinatus), Coontail weed (Ceratophyllum demersum), Water milfoil (Myriophyllum heterophyllum), Pickerel weed (Pontederia cordata), Water lily (Nymphaea odorata), Duckweed (Lemna

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

41 d

Test temperature:

11 to 24 °C in May
16 to 28 °C in June
14 to 29 °C in July 2005

Nominal and measured concentrations:

Nominal: Control, 0.32, 1.0 and 3.2 μg/L

Reference substance (positive control):

no

Duration:

41 d

Dose descriptor:

NOEC

Effect conc.:

0 mg/L

Nominal / measured:

nominal

Conc. based on:

act. ingr.

Basis for effect:

growth rate

Five of the eight aquatic plant species tested (e.g., Elodea, sago pondweed, water milfoil, pickerel weed and pond lily) became well established in the ponds and demonstrated varying degrees of sensitivity to the test substance. Coontail weed, Lemna gibba and Lemna minor were less successful at colonizing the ponds and did not allow a clear assessment of the test substance impact on these species. Because of the lack of growth of these species, effects determinations were not reported.

 

For those species that performed well enough to assess the effects of AE 1170437, the water lily was the most sensitive to the test substance with a NOEC for symptomology of < 0.32 μg/L. Water milfoil was the next most sensitive plant with a NOEC value of 0.32 μg/L. Elodea, sago pondweed and pickerel weed were all unaffected by the exposure and had NOEC values of 3.2 μg/L.

 

Although not all the species tested became well established during the study, the sensitivity of the ones that did flourish, provided NOEC values across the range of concentrations tested, with the lowest value being less than 0.32 μg/L, the lowest concentration tested. New healthy growth (recovery) was occurring in pond lilies exposed to 0.32 and 1.0 μg/L by the end of the 41-day study. Water milfoil, which was also sensitive to AE 1170437 (NOEC established at 0.32 μg/L based on dry weight), exhibited symptomatic effects at≥1.0 μg/L during the exposure. Therefore, there was no opportunity to view recovery. 

The NOEC values for survival and dry weight (growth) are considered the most relevant population-level linked endpoint evaluated. Based on AE 1170437 effect on growth (except for Lemna sp. and Ceratophyllum demersum, where control responses were not adequate for an effects determination), the NOEC for the study would be 0.32 μg/L.

Description of key information

NOEC (70 d): 0.00001 mg a.i./L

Key value for chemical safety assessment

EC10 or NOEC for freshwater plants:

0 mg/L

Additional information

Indaziflam is a selective, pre-emergence alkylazine herbicide therefore aquatic plants are sensitive to exposure as is expected from an herbicidal compound.

The most sensitive species tested was the aquatic plant Lemma gibba with an EC50 of 0.0000728 mg a.i./L, and NOEC of 0.000030 mg a.i./L. Due to the sensitivity of Lemna in standard testing, a series of higher tiered tests was performed in order to determine the potential toxicity of the substance to Lemna and other higher aquatic plants under more realistic conditions.

In the first study (M-303082-01-2) multiple species were tested in the outdoor studies including submerged species and rooted macrophytes. The NOEC based on plant growth from the pond study (non-GLP) was 0.00032 mg a.i./L.

The aquatic mesocosm study (M-304567-01-1) incorporated more species and endpoints, was of longer duration and was conducted under GLP. Thus, this study is used as key study. The NOEC for the higher aquatic plants (non-lemnid type) in the aquatic microcosm was 0.00001 mg a.i./L.

 

Table 1: Summary of other plant studies

Method	Endpoint	Results	Reference
Lemna gibba G3 OECD 221	Chronic 7 d, EC50 NOEC	0.0000728 mg a.i./L 0.0000309 mg a.i./L	Dorgerloh, M. (2007)
Lemna gibba G3 (with sediment) OECD 221	Chronic 7 d, ErC50 NOEC	0.000357 mg a.i./L 0.000154 mg a.i./L	Dorgerloh, M. (2006)
Pond study (EPA OPPTS 850.4450 (Aquatic Plants Field Study (Tier III)))	Chronic, 41 d, NOEC	0.00032 mg a.i./L	Hoberg, J.R. (2008)
Aquatic Microcosm (The aim of the study was to assess the initial and longer term ecotoxicological impact to a freshwater community and the subsequent recovery of the community at concentration levels relevant to the initial surface water PEC values (in the European Union) for a range of agricultural use scenarios)	Chronic, 70 d, NOEC	0.00001 mg a.i./L	Brock, T.C.M. et al. (2008)