2-butyloctanoic acid

Toxicity to terrestrial plants

Link to relevant study record(s)

Reference

Endpoint:

toxicity to terrestrial plants: long-term

Type of information:

experimental study

Adequacy of study:

key study

Study period:

August 2019 - December 2019

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Remarks:

The study was performed in compliance with GLP.

Qualifier:

according to guideline

Guideline:

OECD Guideline 208 (Terrestrial Plants, Growth Test)

Version / remarks:

adopted 19 July 2006, study conducted with 6 terrestrial plant species

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Remarks:

GLP Certificate: Statement of GLP Compliance from Staatliches Gewerbeaufsichtsamt Hildesheim, Germany, dated 03.01.2017

Analytical monitoring:

no

Vehicle:

no

Details on preparation and application of test substrate:

- Method of mixing into soil (if used): The respective test item amounts were weighed out on quartz sand (1 % of the entire soil amount per concentration) for each test item concentration and blended thoroughly. Afterwards, the test item - quartz sand mixture and an appropriate amount of demineralized water (adjusting to a moisture of 45 % of the MHWC) was added to the soil. Subsequently, the soil was mixed carefully with a mixer (2-3 min) to ensure a homogeneous distribution.
- Controls: untreated test substrate

Species:

Avena sativa

Plant group:

Monocotyledonae (monocots)

Details on test organisms:

- Common name: oat
- Plant family: Poaceae
- Variety: KWS Contender
- Source of seed: KWS Lochow GmbH, 29303 Bergen, Germany
- Prior seed treatment/sterilization: none
- Historical germination of seed (germination of seed lot tested): see table #1 in section "Any other information on materials and method" below
- Seed storage: stored in the dark at the test facility at room temperature (22 ± 10 °C) and protected from moisture until use

Species:

Allium cepa

Plant group:

Monocotyledonae (monocots)

Details on test organisms:

- Common name: onion
- Plant family: Amaryllideaceae
- Variety: Exhibition
- Source of seed: Hild Samen GmbH, 71666 Marbach, Germany
- Prior seed treatment/sterilization: none
- Historical germination of seed (germination of seed lot tested): see table #1 in section "Any other information on materials and method" below
- Seed storage: stored dark at the test facility at room temperature (22 ± 10 °C) and protected from moisture until use

Species:

Beta vulgaris

Plant group:

Dicotyledonae (dicots)

Details on test organisms:

- Common name: sugar beet
- Plant family: Amaranthaceae
- Variety: Danicia KWS
- Source of seed: KWS Saat SE, 37574 Einbeck, Germany
- Prior seed treatment/sterilization: none
- Historical germination of seed (germination of seed lot tested): see table #1 in section "Any other information on materials and method" below
- Seed storage: stored dark at the test facility at room temperature (22 ± 10 °C) and protected from moisture until use

Species:

Brassica napus

Plant group:

Dicotyledonae (dicots)

Details on test organisms:

- Common name: rape
- Plant family: Brassicaceae
- Variety: Sherlock
- Source of seed: KWS Saat SE, 37574 Einbeck, Germany
- Prior seed treatment/sterilization: none
- Historical germination of seed (germination of seed lot tested): see table #1 in section "Any other information on materials and method" below
- Seed storage: stored dark at the test facility at room temperature (22 ± 10 °C) and protected from moisture until use

Species:

Lactuca sativa

Plant group:

Dicotyledonae (dicots)

Details on test organisms:

- Common name: lettuce
- Plant family: Asteraceae
- Variety: Larissa
- Source of seed: Hild Samen GmbH, 71666 Marbach, Germany
- Prior seed treatment/sterilization: none
- Historical germination of seed (germination of seed lot tested): see table #1 in section "Any other information on materials and method" below
- Seed storage: stored dark at the test facility at room temperature (22 ± 10 °C) and protected from moisture until use

Species:

Glycine max (G. soja)

Plant group:

Dicotyledonae (dicots)

Details on test organisms:

- Common name: soybean
- Plant family: Fabaceae
- Variety: Obelix
- Source of seed: Delley Samen und Pflanzen AG, CH-1567 Delley, Switzerland
- Prior seed treatment/sterilization: none
- Historical germination of seed (germination of seed lot tested): see table #1 in section "Any other information on materials and method" below
- Seed storage: stored dark at the test facility at room temperature (22 ± 10 °C) and protected from moisture until use

Test type:

seedling emergence and seedling growth test

Study type:

extended laboratory study

Substrate type:

natural soil

Limit test:

no

Total exposure duration:

21 d

Remarks:

28 d exposure for onion

Test temperature:

15.7 - 24.5°C

pH:

4.86 ± 0.08 / 5.63 ± 0.03 (pH values from two batches of soil)

Moisture:

35.1 - 93.8%

Details on test conditions:

TEST SYSTEM
- Testing facility: Noack Laboratorien, 31157 Sarstedt, Germany
- Test container (type, material, size): non-porous plastic containers (standard flower pots) with a diameter of ca. 12 cm
- Amount of soil: 0.70 kg per replicate
- Method of seeding: seeding holes were made with a seedling pistil, one seed was given into each hole and covered with soil
- No. of seeds per container: 5 (3 for soybeans)
- No. of replicates per treatment group: 8
- No. of replicates per control: 8
- No. of replicates per vehicle control: not applicable

SOURCE AND PROPERTIES OF SUBSTRATE (if soil)
- Source: Landwirtschaftliche Untersuchungs- und Forschungsanstalt Speyer (LUFA), 67346 Speyer, Germany
- Sand (0.063 - 2 mm): 93.4 % / 84.2 %
- Silt (0.002 - 0.063 mm): 3.0 % / 8.8 %
- Clay (< 0.002 mm): 3.7 % / 7.0 %
- Organic carbon: 0.649 % / 1.83 %
- Soil taxonomic classification: loamy sand
- Soil classification system: DIN classification
- Composition: A 2:1 mixture of natural soil LUFA 2.2 (batch number: Sp2.22419 (1st Definitive Test) and Sp2.23419 (2nd and 3rd Defintive Test) and quartz sand (12a) was used
- Maximum water holding capacity (in % dry weigth): 30.8 (exposure starting 2019-08-19) / 45.7 (exposure starting 2019-10-25) / 42.7 (exposure starting 2019-11-29)
- Pretreatment of soil: none
- Storage (condition, duration): not stated
- Source of quartz sand: Dörentrup Quarz GmbH Co. KG, 31089 Duingen, Germany

NUTRIENT MEDIUM
- Description: HAKAPHOS® SOFT SPEZIAL 16+8+22(+3) (Origin: Grünes Landhaus, 31139 Hildesheim, Germany)

GROWTH CONDITIONS
The test was conducted in a climatic chamber with conditions suitable for normal growth and reflecting typical environmental conditions for the species and varieties tested.
- Photoperiod: 16 h
- Light source: Special-fluorescent tube Fluora and Daylight (Osram)
- Light intensity and quality: 4713 ± 453 lx (factor to convert lux to µE/m2/s = 0.0135), cool white fluorescent tubes (special light sources for plants: they emit most of their light at the blue and red ends of the spectrum and are perfectly matching to that for photo-biological processes)
- Temperatures: 15.7 - 24.5°C
- Relative humidity (%): 35.1 - 93.8
- Watering regime and schedules: Bottom watering of the test containers with fertilized tap water as needed.
- Interval of applications: The control and test item treatments were applied once at the start of the exposure
- Method of application: The respective test item amounts were weighed out on quartz sand (1% of the entire soil amount per concentration) for each test item concentration and blended thoroughly. Afterwards, the test item - quartz sand mixture and an appropriate amount of demineralized water (adjusting to a moisture of 45 % of the MHWC) was added to the soil. Subsequently, the soil was mixed carefully with a mixer (2-3 min) to ensure a homogeneous distribution. The treated soil was transferred to the test containers and the seeds were sown (see seeding method).
- Fertilization: for watering a 0.05 ‰ solution of HAKAPHOS® SOFT SPEZIAL 16+8+22(+3) was used

EFFECT PARAMETERS MEASURED (with observation intervals if applicable) :
- Observations: Number of emerged seedlings, number of dead plants and visual phytotoxic effects on days 7, 14 and 21, onion additionally on day 28. The rating of the treated plants was done in relation to the untreated control plants. Observations included all variations, either inhibitory or stimulatory, between the treated replicates and the untreated controls. Such variations may be phytotoxic symptoms (e.g. chlorosis, necrosis, wilting), effects of growth and development rates.
- Measurements: shoot heights (in cm), fresh weights of the shoots (in g) at the end of the exposure period after cutting the plants at the soil surface. The shoot height was measured per plant. Average mean values per replicate were calculated. The shoot fresh weight was determined for all plants from the same pot and considered as one replicate.

- Phytotoxicity rating system (if used):
a) Observation parameters:
(1) Deformation of leaves (curling / twisting / sticking / …)
(2) Shoot deformations (curling / bending / …)
(3) Stunted growth
(4) Necrosis
(5) Chlorosis
(6) Lighter green
(7) Darker green
(8) Loss of colour
(9) Discoloration of leaves
(10) Wilting
(E) Dead plant (Number of dead plants)

b) Assessment of effects:
- = no effects observed / normal growth
+/- = slight effects
+ = medium effects
++ = strong effects


TEST CONCENTRATIONS
- Spacing factor for test concentrations: factor 2 for oats, onion, lettuce, soybean; factor 2.5 for sugar beet, rape
- Range finding study: yes, performed under the same laboratory conditions as specified for the definitive study with 4 replicates per concentration and control, test duration was 21 days, at test end, shoot fresh weight and emergence were determined
- Test concentrations: 10, 100, 1000 mg/kg DW
- Results used to determine the conditions for the definitive study: yes, for details on results of range finding study, see below tables #2a and 2b in section "Any other information on material and methos incl. tables"

Nominal and measured concentrations:

Nominal concentrations:
oats, onion, lettuce, soybean 1000 - 500 - 250 - 125 - 62.5 mg/kg DW
sugar beet, rape: 1000 - 400 - 160 - 64 - 25.6 - 10.24 mg/kg DW

Reference substance (positive control):

no

Remarks:

No reference item is recommended for this test according to the test guideline (OECD 208).

Species:

Avena sativa

Duration:

21 d

Dose descriptor:

EC25

Effect conc.:

> 1 000 mg/kg soil dw

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

seedling emergence

Species:

Allium cepa

Duration:

28 d

Dose descriptor:

EC25

Effect conc.:

> 1 000 mg/kg soil dw

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

seedling emergence

Species:

Beta vulgaris

Duration:

21 d

Dose descriptor:

EC25

Effect conc.:

> 1 000 mg/kg soil dw

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

seedling emergence

Species:

Brassica napus

Duration:

21 d

Dose descriptor:

EC25

Effect conc.:

> 1 000 mg/kg soil dw

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

seedling emergence

Species:

Lactuca sativa

Duration:

21 d

Dose descriptor:

EC25

Effect conc.:

125 mg/kg soil dw

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

seedling emergence

Remarks on result:

other: 95% CL

Remarks:

207 - 267 mg/kg DW

Species:

Lactuca sativa

Duration:

21 d

Dose descriptor:

EC25

Effect conc.:

69.9 mg/kg soil dw

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

other: shoot fresh weight

Remarks on result:

other: 95% CL

Remarks:

< 62.5 - 100 mg/kg DW

Species:

Lactuca sativa

Duration:

21 d

Dose descriptor:

EC25

Effect conc.:

192 mg/kg soil dw

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

other: shoot height

Remarks on result:

other: 95% CL

Remarks:

123 - > 250 mg/kg DW

Species:

Glycine max (G. soja)

Duration:

21 d

Dose descriptor:

EC25

Effect conc.:

> 1 000 mg/kg soil dw

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

seedling emergence

Key result

Species:

Lactuca sativa

Duration:

21 d

Dose descriptor:

NOEC

Effect conc.:

125 mg/kg soil dw

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

seedling emergence

Key result

Species:

Lactuca sativa

Duration:

21 d

Dose descriptor:

NOEC

Effect conc.:

125 mg/kg soil dw

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

other: shoot height

Key result

Species:

Lactuca sativa

Duration:

21 d

Dose descriptor:

NOEC

Effect conc.:

62.5 mg/kg soil dw

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

other: shoot fresh weight

Details on results:

The toxicity of 2-butyloctanoic acid was determined in three independent tests. In the first test (exposure phase 2019-08-19 to 2019-09-09) the effect levels for sugar beet and rape were too high to determine NOEC values. In the repetition, second definitive test (exposure phase 2019-10-25 to 2019-11-15), the effect levels were too low to determine the EC50-value for sugar beet. Therefore, sugar beet was repeated in a third definitive test (exposure phase 2019-12-03 to 2019-12-20). The second definitive test was used for evaluation of effect levels for rape and the third definitive test was used for determination of effect levels for sugar beet.
The percentage of inhibition of shoot height, shoot fresh weight and rate of emergence of all tested species is given in table #3 in section "Any other information on results incl. tables" below. NOEC, LOEC, EC25 and EC50-values are summarized in tables #4-6 in section "Any other information on results incl. tables" below.

Emerged seedlings: For oats, sugar beet, rape, lettuce and soybean > 50 % of the control plants were emerged after 7 days. For onion the rate of emergence of the control plants reached > 50 % within 14 days. For onion the experimental phase was prolonged until 28 days.

Visual phytotoxicity:
1) Oat: No visual phytotoxicity or dead plants noticed on day 7. On day 14 in the highest test substance concentration (1000 mg/kg DW) slight effects of stunted growth were noted in all replicates. On test end at day 21, in 3 replicates the effect was described as medium, whereas in the other replicates the slight effect of stunted growth remained. In all other test substance concentrations no effects were observed and a normal growth was noted.
2) Onion: No visual phytotoxicity or dead plants noticed on day 7. On day 14, 1 replicate at 250 mg/kg DW showed slight loss of color. On day 21, 2 dead plants were counted: one replicate in the highest test concentration (1000 mg/kg DW) and one at 250 mg/kg DW (same replicate which showed loss of color before). At the end of the exposure period at day 28 the remaining replicates in the highest test substance concentration showed slight effects of stunted growth. All other plants showed normal growth and no effects were found.
3) Sugar beet: no effects noted on day 7. One dead plant in the highest test substance concentration (1000 mg/kg DW) on day 14 noted. On day 21, at the end of the test, slight stunted growth in one replicate at 1000 mg/kg DW were observed. All other replicates showed normal growth.
4) Rape: On day 7, 7 of 8 replicates of the 400 mg/kg DW test substance concentration showed stunted growth with slight effects. At 1000 mg/kg DW all replicates showed medium effects of stunted growth. Day 14: in test substance concentration of 400 mg/kg DW, no effects and normal growth was noted, at 1000 mg/kg DW only slight effects of stunted growth remained. On test end, at day 21 the stunted growth in the highest test substance concentration were described as medium in 5 replicates and strong in 3 replicates. No other phytotoxic effect or dead plant was noted neither in the control nor in all other test substance concentrations.
5) Lettuce: No effects or dead plants noted on days 7 and 14. On day 21 at the end of the test, in test substance concentrations of 125 mg/kg DW slight effects of stunted growth observed in 4 of 8 replicates. At 250 mg/kg DW, slight effects (stunted growth) in 5 replicates, medium effects in 2 replicates and strong effects of stunted growth in the remaining 2 replicates. In test substance concentration of 500 and 1000 mg/kg DW no seedlings emerged.
6) Soybean: No visual phytotoxicity or dead plants noted at days 7 and 14. On day 21, 1 dead plant in the control group and slightly stunted growth in all replicates of the highest test substance concentration (1000 mg/kg DW) observed.

Deviations from the study plan: For the 2nd definitive study the soil was moistened to 42 % of MWHC of the soil due to a typing mistake. Nevertheless, the used moisture still meets the requirements stated in the guideline. This deviation was considered to have no impact on quality and integrity of the study.

Reported statistics and error estimates:

Percentage of inhibition: The percentage of inhibition of biomass growth (shoot height, shoot fresh weight) and rate of emergence were calculated in relation to the control. All dead plants were excluded from the calculation of shoot height and fresh weight (above-ground biomass).
NOEC / LOEC of biomass growth / emergence: One Way Analysis of Variance (ANOVA) was carried out for the determination of statistically significant differences compared to control replicates. When running a One Way Analysis of Variance, a Normality test (Shapiro-Wilk) and an Equal Variance test (Brown-Forsythe) were done first. P-values for both, Normality and Equal Variance test, are 0.05. The alpha-value for ANOVA (acceptable probability of incorrectly concluding that there is a difference) is alpha = 0.05. Failure of the normality test and / or the equal variance test can be caused by extremely homogeneous emergence and growth patterns as opposed to higher variances in other treatments. Due to the high and even number of replicates in the control and treatment groups, the failure had no influence on the robustness of the calculations.
EC-values and confidence intervals of biomass growth: ECx- values were calculated by sigmoidal dose-response regression using GraphPadPrism. Four parameters were used for dose-response fitting. Calculation of the confidence intervals for EC-values was carried out using standard procedures provided by GraphPadPrism. EC-values and graphical analysis were determined for those plant species where effects ≥ 25 % occurred.
Software: Excel, Microsoft Corporation, SigmaPlot (Windows), SPSS Incorporation, GraphPadPrism, GraphPad Software, Inc.

Table #3: Percentage of Rate of Emergence, Inhibition of Shoot Height and Shoot Fresh Weight

	Test concentration [mg/kg DW]	Mean Emergence rate Day 7 [%]	Mean Emergence rate Day 14 [%]	Mean Emergence rate Day 21 (Day 28 for onion) [%]	Shoot Height at Test End Mean ± SD [cm]	Shoot Fresh Weight at Test End Mean ± SD [mg]
Oats	0 (control)	93	95	95	41.3 ± 1.4	1136 ± 115
	62.5	98	98	98	41.0 ± 1.4	1155 ± 70
	125	95	100	100	39.9 ± 3.5	1116 ± 181
	250	90	93	93	41.4 ± 1.3	975 ± 94*
	500	98	98	98	39.3 ± 1.7	800 ± 79*
	1000	93	95	95	30.5 ± 5.3*	463 ± 154*
Onion	0 (control)	0	100	100	17.0 ± 1.9	220 ± 44
	62.5	0	98	98	16.9 ± 1.4	206 ± 19
	125	0	93	93	16.0 ± 1.9	196 ± 38
	205	0	93	93	16.5 ± 1.8	188 ± 35
	500	3	90	90	14.2 ± 1.6*	160 ± 38*
	1000	0	85	90	11.1 ± 1.7*	102 ± 26*
Sugar beet	0 (control)	95	98	98	7.7 ± 0.3	508 ± 39
	10.24	98	98	98	7.9 ± 0.3	519 ± 54
	25.6	100	100	100	7.8 ± 0.4	540 ± 60
	64	93	98	98	7.6 ± 0.6	492 ± 89
	160	90	95	95	8.4 ± 0.4#	654 ± 81#
	400	93	98	98	8.3 ± 0.3#	581 ± 93
	1000	83	85	85	7.4 ± 0.5	409 ± 57*
Rape	0 (control)	98	100	100	15.0 ± 0.7	1399 ± 158
	10.24	98	100	100	14.9 ± 0.8	1306 ± 170
	25.6	95	98	98	14.4 ± 1.4	1248 ± 178
	64	98	98	98	14.9 ± 0.8	1292 ± 179
	160	98	98	98	15.3 ± 0.7	1438 ± 181
	400	90	95	95	14.2 ± 0.9	1159 ± 83*
	1000	88	95	98	11.2 ± 1.4*	672 ± 147*
Lettuce	0 (control)	75	78	78	5.9 ± 0.5	407 ± 96
	62.5	85	90	90	5.6 ± 0.9	323 ± 98
	125	55	78	78	5.0 ± 0.8	211 ± 72*
	250	23	55	55*	4.1 ± 0.6*	143 ± 47*
	500	0	0	0*	-	-
	1000	0	0	0*	-	-
Soybean	0 (control)	96	100	100	19.9 ± 0.8	2582 ± 273
	62.5	92	96	100	18.8 ± 2.0	2423 ± 380
	125	29	88	92	16.9 ± 1.4*	2384 ± 368
	250	50	96	96	18.5 ± 1.3*	2291 ± 199
	500	33	96	96	17.4 ± 0.8*	2056 ± 234*
	1000	21	83	88	15.3 ± 0.9*	1718 ± 209*
values in bold* = statistically significant inhibition  # = statistically significant promoted growth, not included in calculations

Table #4: Shoot Height: NOEC, LOEC, EC25- and EC50-Values with Confidence Range (p)
Species	NOEC [mg/kg dw]	LOEC [mg/kg dw]	EC25 [mg/kg dw]	p = 95% [mg/kg dw]	EC50 [mg/kg dw]	p = 95% [mg/kg dw]
Oats	500	1000	964	824 - >1000	>1000	-
Onion	250	500	703	566 - 874	>1000	-
Sugar beet	1000	>=1000	>1000	-	>1000	-
Rape	400	1000	990	876 - >1000	>1000	-
Lettuce	125	250	192	123 - >250#	>250#	-
Soybean	62.5	125	> 1000	-	>1000	-
# No seedling emergence at test concentrations > 250 mg/kg dw

Table #5: Shoot Fresh Weight: NOEC, LOEC, EC25- and EC50-Values with Confidence Range (p)
Species	NOEC [mg/kg dw]	LOEC [mg/kg dw]	EC25 [mg/kg dw]	p = 95% [mg/kg dw]	EC50 [mg/kg dw]	p = 95% [mg/kg dw]
Oats	125	250	421	341 - 517	832	730 - 960
Onion	250	500	450	321 - 633	929	758 - >1000
Sugar beet	500	1000	>1000	-	>1000	-
Rape	160	400	573	425 - 710	956	826 - >1000
Lettuce	62.5	125	69.9	<62.5 - 100	133	91.5 - 196
Soybean	250	500	642	436 - 929	>1000	-

Table #6: Number of Emerged Seedlings: NOEC, LOEC, EC25- and EC50-Values with Confidence Range (p)
Species	NOEC [mg/kg dw]	LOEC [mg/kg dw]	EC25 [mg/kg dw]	p = 95% [mg/kg dw]	EC50 [mg/kg dw]	p = 95% [mg/kg dw]
Oats	1000	>=1000	>1000	-	>1000	-
Onion	1000	>=1000	>1000	-	>1000	-
Sugar beet	1000	>=1000	>1000	-	>1000	-
Rape	1000	>=1000	>1000	-	>1000	-
Lettuce	125	250	241	207 - 267	287	263 - 360
Soybean	1000	>=1000	>1000	-	>1000	-

Validity criteria fulfilled:

yes

Remarks:

The results of the control for all plant species met the required validity criteria. Therefore, the test is considered to be valid.

Conclusions:

VISUAL PHYTOTOXICITY:
In all test species visual phytotoxic effects of stunted growth were noticed, the most sensitive species being lettuce, in concentration of 125 mg/kg dw slight effects, in 250 mg/kg slight to strong effects were observed. In the other species, in the highest test substance concentration of 1000 mg/kg dw this effect was also described, ranging from slight to strong.
NUMBER OF EMERGED SEEDLINGS:
This endpoint was effected in species lettuce, no seedlings emerged at concentrations > 250 mg/kg dw, with NOEC being 125 mg/kg dw, and an EC25 of 241 mg/kg dw calculated for this endpoint (95% cl ranging from 207 - 267 mg/kg dw). In all other species the number of emerged seedlings were not effected up to the highest test substance concentration.
SHOOT HEIGHT:
It was most severly effected for species soybean and lettuce, the following values were derived:
Soybean: NOEC = 62.5 mg/kg dw, LOEC = 125 mg/kg dw, EC25 > 1000 mg/kg dw, EC50 > 1000 mg/kg dw
Lettuce: NOEC = 125 mg/kg dw, LOEC = 250 mg/kd dw, EC25 = 192 mg/kg dw (95% cl 123 - 250 mg/kg dw), EC50 > 250 mg/kg dw
SHOOT FRESH WEIGHT:
Species lettuce was the most sensitive species, the following values were calculated: NOEC = 62.5 mg/kg dw, LOEC = 125 mg/kg dw, EC 25 = 69.9 mg/kg dw (95% cl < 62.5 - 100 mg/kg dw), EC50 = 133 mg/kg dw (95% cl 91.5 - 196 mg/kg dw).

Executive summary:

The phytotoxicity of the test item to six terrestrial plant species was determined according to OECD 208 (July 2006) at the test facility in seedling emergence and seedling growth tests over a period of 21 days. For onion 50 % emergence of the control seedlings was reached after 14 days. Therefore, the test for onion was prolonged until day 28.

Test systems comprised two monocotyledon (oats, Poaceae; onion, Amaryllideaceae), and four dicotyledons (sugar beet, Amaranthaceae; rape, Brassicaceae; lettuce, Asteraceae; soybean, Fabaceae). The test was conducted with various test concentrations:

Oats, onion, lettuce, soybean: 1000 - 500 - 250 - 125 - 62.5 mg/kg DW (factor 2)

Sugar beet, rape: 1000 - 400 - 160 - 64 - 25.6 - 10.24 mg/kg DW (factor 2.5)

The test item was incorporated into the soil in which the seeds were sown. The test containers were bottom watered with nutrient solution as needed.

Potential toxic effects of the test item were assessed on day 7, 14 and 21 (onion additionally on day 28) by visual observations (number of emerged seedlings and phytotoxic effects) and at test end by shoot height and shoot fresh weight determination.

In all test species visual phytotoxic effects of stunted growth were noticed, the most sensitive species being lettuce, in concentration of 125 mg/kg dw slight effects, in 250 mg/kg slight to strong effects were observed. In the other species, in the highest test substance concentration of 1000 mg/kg dw this effect was also described, ranging from slight to strong.

The number of emerged seedlings was effected in species lettuce, no seedlings emerged at concentrations > 250 mg/kg dw, with NOEC being 125 mg/kg dw, and an EC25 of 241 mg/kg dw calculated for this endpoint (95% cl ranging from 207 - 267 mg/kg dw). In all other species the number of emerged seedlings were not effected up to the highest test substance concentration.

The shoot height was most severly effected for species soybean and lettuce, the following values were derived:

Soybean: NOEC = 62.5 mg/kg dw, LOEC = 125 mg/kg dw, EC25 > 1000 mg/kg dw, EC50 > 1000 mg/kg dw.

Lettuce: NOEC = 125 mg/kg dw, LOEC = 250 mg/kd dw, EC25 = 192 mg/kg dw (95% cl 123 - 250 mg/kg dw), EC50 > 250 mg/kg dw.

Species lettuce was the most sensitive species for shoot fresh weight, the following values were calculated: NOEC = 62.5 mg/kg dw, LOEC = 125 mg/kg dw, EC 25 = 69.9 mg/kg dw (95% cl < 62.5 - 100 mg/kg dw), EC50 = 133 mg/kg dw (95% cl 91.5 - 196 mg/kg dw).

Description of key information

The effects of 2 -butyloctanoic acid to terrestrial plants were determined in 6 species in seedling emergence and seedling growth test according to OECD Guidlene 208 (July 2000). Species lettuce was the most sensitive species, the following values were calculated for shoot fresh weight: NOEC = 62.5 mg/kg dw, LOEC = 125 mg/kg dw, EC50 = 133 mg/kg dw.

Key value for chemical safety assessment

Long-term EC10, LC10 or NOEC for terrestrial plants:

62.5 mg/kg soil dw

Additional information

The phytotoxicity of the test item to six terrestrial plant species was determined according to OECD 208 (July 2006) at the test facility in seedling emergence and seedling growth tests over a period of 21 days. For onion 50 % emergence of the control seedlings was reached after 14 days. Therefore, the test for onion was prolonged until day 28.

Test systems comprised two monocotyledon (oats, Poaceae; onion, Amaryllideaceae), and four dicotyledons (sugar beet, Amaranthaceae; rape, Brassicaceae; lettuce, Asteraceae; soybean, Fabaceae). The test was conducted with various test concentrations:

Oats, onion, lettuce, soybean: 1000 - 500 - 250 - 125 - 62.5 mg/kg DW (factor 2)

Sugar beet, rape: 1000 - 400 - 160 - 64 - 25.6 - 10.24 mg/kg DW (factor 2.5)

The test item was incorporated into the soil in which the seeds were sown. The test containers were bottom watered with nutrient solution as needed.

Potential toxic effects of the test item were assessed on day 7, 14 and 21 (onion additionally on day 28) by visual observations (number of emerged seedlings and phytotoxic effects) and at test end by shoot height and shoot fresh weight determination.

The number of emerged seedlings was effected in species lettuce, no seedlings emerged at concentrations > 250 mg/kg dw, with NOEC being 125 mg/kg dw. In all other species the number of emerged seedlings were not effected up to the highest test substance concentration.

The shoot height was most severly effected for species soybean and lettuce, the following values were derived:

Soybean: NOEC = 62.5 mg/kg dw, LOEC = 125 mg/kg dw, EC25 > 1000 mg/kg dw, EC50 > 1000 mg/kg dw.

Lettuce: NOEC = 125 mg/kg dw, LOEC = 250 mg/kd dw, EC25 = 192 mg/kg dw (95% cl 123 - 250 mg/kg dw), EC50 > 250 mg/kg dw.

Species lettuce was the most sensitive species for shoot fresh weight, the following values were calculated: NOEC = 62.5 mg/kg dw, LOEC = 125 mg/kg dw, EC 25 = 69.9 mg/kg dw (95% cl < 62.5 - 100 mg/kg dw), EC50 = 133 mg/kg dw (95% cl 91.5 - 196 mg/kg dw).