thiourea; thiocarbamide

Toxicity to soil macroorganisms except arthropods

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

toxicity to soil macroorganisms except arthropods: short-term

Type of information:

experimental study

Adequacy of study:

weight of evidence

Study period:

no data

Reliability:

4 (not assignable)

Rationale for reliability incl. deficiencies:

documentation insufficient for assessment

Remarks:

Documentation insufficient for assessment. In addition, the purity of the test substance is not reported. However, as effects could only be observed at very high test substance concentrations (28-d LC50 = 3550 mg/kg soil), it is assumed that the toxicity can be attributed to the test substance itself and not to potential impurities.

Qualifier:

according to guideline

Guideline:

other: Guideline for the testing of the toxicity of chemicals and plant treatment products in earthworms (Eisenia foetida Sav.)

GLP compliance:

not specified

Analytical monitoring:

no

Details on sampling:

Not applicable.

Vehicle:

no

Details on preparation and application of test substrate:

- Method of mixing into soil: not reported

Test organisms (species):

Eisenia fetida

Animal group:

annelids

Details on test organisms:

TEST ORGANISM
- Common name: earthworm
- Source: FhG
- Age at test initiation: 3-6 months
- Weight at test initiation: ca. 500 mg

ACCLIMATION
- Acclimation period: no data
- Acclimation conditions: same as test:
* room temperature: 21 +/- 0.5 °C
* 16:8 h (light:dark)
* illumination: 700 lux

Study type:

laboratory study

Substrate type:

artificial soil

Limit test:

no

Total exposure duration:

28 d

Post exposure observation period:

Not applicable.

Test temperature:

21 +/- 0.5 °C

pH:

Not reported.

Moisture:

Not reporetd.

Details on test conditions:

TEST SYSTEM
- Test container: material not reported, size: 1.5 L
- Amount of soil or substrate: 650 g
- No. of organisms per container (treatment): 10
- No. of replicates per treatment group: 4
- No. of replicates per control: 1


SOURCE AND PROPERTIES OF ARTIFICIAL SUBSTRATE:
- Composition:
* 65 g white peat
* 32.5 g bentonite
* 3.25 g cow manure
* 6.5 g lime
* 542.75g quartz sand
* 227.5 ml H2O
- Storage: 24 h prior to use in the experiment

OTHER TEST CONDITIONS
- Photoperiod: 16:8 (light:dark)
- Light intensity: 700 lux

EFFECT PARAMETERS MEASURED: mortality after 28 days

Nominal and measured concentrations:

Nominal: 0, 1,500, 3,000, 4,500 and 6,000 mg/kg

Reference substance (positive control):

yes

Remarks:

Chloroacetamide

Key result

Duration:

28 d

Dose descriptor:

LC50

Effect conc.:

3 550 mg/kg soil dw

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

mortality

Details on results:

- Mortality at end of exposure period:
* 0 mg/kg soil dw: 0 % mortality
* 1,500 mg/kg soil dw: 2.5 % mortality
* 3,000 mg/kg soil dw: 17.5 % mortality
* 4,500 mg/kg soil dw: 100 % mortality
* 6,000 mg/kg soil dw: 100 % mortality

- Changes in mean body weigth of live adults at end of exposure period:
* 1,500 mg/kg soil dw: 43 mg
* 3,000 mg/kg soil dw: 131 mg

Results with reference substance (positive control):

LC50 (28 d) = 18 mg/kg

Reported statistics and error estimates:

No data.

Table 1: Test results with thiourea

Test substance concentration [mg/kg]	Mean reduction in body weight after 28 d [mg]	Number of living earthworms after 28 d				Mortality after 28 d [%]
		A	B	C	D
Control (0)	-	10				0
1,500	43	10	10	9	10	2.5
3,000	131	9	10	7	7	17.5
4,500	-	0	0	0	0	100
6,000	-	0	0	0	0	100
Thiourea LC50 (28-d) = 3,550 mg/kg

 

Validity criteria fulfilled:

not specified

Conclusions:

The 28-d LC50 of thiourea for Eisenia foetida in artificial substrate is 3550 mg/kg soil dw.

Executive summary:

In a 28 day acute toxicity study, earthworms (Eisenia foetida) were exposed to thiourea at nominal concentrations of 0, 1500, 3000, 4500, and 6000 mg/kg dry weight of artificial substrate. The reference chemical used was chloroacetamide. The experiment was carried out in accordance with the “Guideline for the testing of the toxicity of chemicals and plant treatment products in earthworms (Eisenia foetida Sav.)”. The 28 day LC50 was 3550 mg/kg dw of substrate. Thiourea is therefore considered to be non-toxic to earthworms.

 

Due to deficiencies in study documentation this study is used in a weight-of-evidence approach in the assessment of thiourea.

Reference 2

Endpoint:

toxicity to soil macroorganisms except arthropods: long-term

Type of information:

experimental study

Adequacy of study:

weight of evidence

Study period:

no data

Reliability:

4 (not assignable)

Rationale for reliability incl. deficiencies:

documentation insufficient for assessment

Qualifier:

no guideline available

Principles of method if other than guideline:

Tomato roots were grown in petri dishes and inoculated with egg masses of M. javanica and the effects on the root and nematode development were determined 4 weeks after inoculation

GLP compliance:

not specified

Analytical monitoring:

not specified

Details on sampling:

see section "any other information on materials and methods incl. tables"

Vehicle:

not specified

Details on preparation and application of test substrate:

no data

Test organisms (species):

other: Meloidogyne javanica

Animal group:

nematods

Details on test organisms:

no data

Study type:

laboratory study

Substrate type:

other: Roots of tomato (Lycopersicon esculentum)

Limit test:

no

Total exposure duration:

96 h

Remarks:

The observation period was 4 weeks

Post exposure observation period:

28 days

Test temperature:

4 °C

pH:

no data

Moisture:

n.a.; the study was conducted in basal medium

Details on test conditions:

Experiment 1: Root growth and nematode development were examined 4 weeks following inoculation by weighing the fresh roots, both infected and noninfected, and by sampling 100 +/-5 nematode individuals per culture from galled roots stained for 5 minutes in boiling acid fuchsin-lactophenol.

Experiment 2: The nematocidal action of Thiourea was examined by two methods: 50 ml conical flasks containing 25-ml sterile solutions thiourea at concentrations of 0, 1, 10, and 100 ppm with six replicates of each treatment. The flasks were kept in the dark at 4°C for 96 hours. Every 24 h the moving nematodes per 1 ml sample from each flask was counted

Experiment 3: A 3 cm petri dish containing basal medium was placed in a 9 cm dish containing basal medium enriched with 12 ppm of thiourea. The excised tomato roots were placed in the smaller dish and the lateral roots were allowed to grow in both dishes. Only roots in the small dish were inoculated to prevent direct nematode contact with the chemical being tested. Each treatment was replicated 10 times.

Nominal and measured concentrations:

Experiment 1: Nominal concentrations: 6, 12, 18, 23 and, 46 mg/L thiourea
Experiment 2: 0, 1, 10 and 100 mg/L thiourea
Experiment 3: 12 mg/L thiourea

Reference substance (positive control):

no

Key result

Duration:

28 d

Dose descriptor:

NOEC

Effect conc.:

6 other: ppm

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

other: microscopic examination; development of nematodes

Thiourea did not affect root growth at concentrations < 12 mg/L. Thiourea inhibited nematode development at concentrations above 6 mg/L. Only 36 % of the nematodes developed into mature adults, compared to 90 % of the control.

Thiourea affected development of coenocytes in roots treated with 12 mg/L thiourea.

Nematodes of the species M. javanica, T. semipenetrans, or P. thornei were not killed by incubation in aqueous solutions of thiourea in concentrations up to 100 mg/L for 96 hours.

Validity criteria fulfilled:

not specified

Conclusions:

Thiourea was shown to inhibit nematode development by affecting the plant metabolism essential to coenocyte formation. A NOEC of 6 ppm thiourea was established based on development of the nematodes.

Executive summary:

Glazer & Orion (1984) investigated the effects of thiourea on the development of nematodes. Excised tomato roots, growing on basal medium and inoculated with eggs of Meloidogyne javanica, were exposed to thiourea concentrations in the range of 6‒46 mg/litre. After 96 h of exposure, thiourea concentrations of 12 mg/litre inhibited nematode development. Only 36 % matured to adults (in the untreated control: 90 %) after an observation period of 4 weeks. For M. javanica (second larval stage), Tylenchulus semipenetrans (second larval stage), and Pratylenchus thornei (adult and juvenile organisms), no increased mortality was found after incubation in aqueous solutions of thiourea at concentrations up to 100 mg/litre for 96 h. The authors furthermore demonstrated that thiourea is taken up via the plant roots and that the nematicidal effect is systemic.

Reference 3

Endpoint:

toxicity to soil macroorganisms except arthropods: short-term

Type of information:

experimental study

Adequacy of study:

weight of evidence

Study period:

No data.

Reliability:

4 (not assignable)

Rationale for reliability incl. deficiencies:

documentation insufficient for assessment

Qualifier:

equivalent or similar to guideline

Guideline:

other: no guideline reported

Principles of method if other than guideline:

Guideline not reported.
3-6 months old earthworms were exposed to thiourea at 1000 mg/kg in artificial substrate. Prior to testing earthworms were conditioned 3-5 days to the substrate. Mortalities were recorded after 28 days of exposure.

GLP compliance:

not specified

Analytical monitoring:

no

Details on sampling:

Not applicable.

Vehicle:

no

Details on preparation and application of test substrate:

- Method of mixing into soil:
* components of the artificial substrate were mixed with a heavy duty mixer (Allfix A2-1, Bauknecht) in 10 L stainless steel bowl for 10-12 min.
* 350 ml deionized water were simultaneously added

Test organisms (species):

Eisenia fetida

Animal group:

annelids

Details on test organisms:

TEST ORGANISM
- Common name: earthworm
- Source: Fraunhofer Institut für Toxikologie und Aerosolforschung Schmallenberg, Germany
- Age at test initiation: 3 - 6 month
- Weight at test initiation: 20 % of earthworms: >/= 400 mg
48 % of earthworms: 300-399 mg
32 % of earthworms: 200-299 mg

ACCLIMATION
- Acclimation period: 3-5 days prior to testing
- Acclimation conditions: no data

Study type:

laboratory study

Substrate type:

artificial soil

Limit test:

yes

Total exposure duration:

28 d

Post exposure observation period:

Not applicable.

Test temperature:

No data.

pH:

No data.

Moisture:

No data.

Details on test conditions:

TEST SYSTEM
- Test container: no data
- Amount of soil or substrate: no data
- No. of organisms per container: no data
- No. of replicates per treatment group: no data
- No. of replicates per control: no data


SOURCE AND PROPERTIES OF ARTIFICIAL SUBSTRATE:
- Composition:
* White peat
* Bentonite
* Cow manure
* Lime
* Quartz sand
* H2O
- Storage until use in closed 24 L polyethylene boxes


EFFECT PARAMETERS MEASURED: mortality and sublethal effects after 28 days

Nominal and measured concentrations:

Nominal: 1000 mg/kg

Reference substance (positive control):

yes

Remarks:

chloroacetamide

Key result

Duration:

28 d

Dose descriptor:

EC50

Effect conc.:

> 1 000 mg/kg soil dw

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

mortality

Duration:

28 d

Dose descriptor:

EC0

Effect conc.:

1 000 mg/kg soil dw

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

other: sublethal effects

Details on results:

No details reported.

Results with reference substance (positive control):

No results reported.

Reported statistics and error estimates:

No data.

Validity criteria fulfilled:

not specified

Conclusions:

The 28-d LC50 of thiourea to Eisenia foetida is > 1000 mg/kg artificial soil dw.

Executive summary:

In a 28 day limit test on the acute toxicity of thiourea to earthworms (Eisenia foetida), earthworms were exposed to thiourea at a nominal concentration 1000 mg/kg dry weight of artificial substrate. The reference chemical used was chloroacetamide. The 28 day LC50 was > 1000 mg/kg dw of substrate. In addition, no sublethal effects could be observed at that concentration. Thiourea is therefore considered to be non-toxic to earthworms.

 

Due to deficiencies in study documentation this study is used in a weight-of-evidence approach in the assessment of thiourea.

Description of key information

Two 28-d studies on the toxicity to Eisenia foetida (endpoint recorded: mortality) are available. The studies were conducted by Korte et al. (1984) and Friesel et al. (1984). The reported LC50 values(28 d) were > 1,000 mg/kg substrate and equal to 3,550 mg/kg substrate, respectively. In addition, in the limit test conducted by Korte et al. (1984), no sublethal effects could be observed at 1,000 mg/kg substrate. Therefore thiourea is considered to be non-toxic to earthworms.

Key value for chemical safety assessment

Short-term EC50 or LC50 for soil macroorganisms:

3 550 mg/kg soil dw

Additional information

Two 28-d studies on the toxicity to soil macroorganisms (except arthropods) are available. The studies were conducted by Korte et al. (1984) and Friesel et al. (1984). Due to deficiencies in study documentation they are used in a weight-of-evidence approach in the assessment of thiourea.

In the 28 day limit test on the acute toxicity of thiourea to earthworms (Eisenia foetida) conducted by Korte et al. (1984), earthworms were exposed to thiourea at a nominal concentration of 1,000 mg/kg dry weight of artificial substrate. The substrate consisted of white peat, bentonite, cow manure, lime, quartz sand and water. The reference chemical used was chloroacetamide. The 28 day LC₅₀ for thiourea was determined to be > 1,000 mg/kg of substrate. In addition, no sublethal effects could be observed at that concentration.

In the second 28 day acute toxicity study, earthworms (Eisenia foetida) were exposed to thiourea at nominal concentrations of 0, 1500, 3000, 4500, and 6000 mg/kg dry weight of artificial substrate. The substrate had the same composition as that used by Korte et al. (1984). In addition, the exact amounts of the individual constituents were reported (65 g white peat, 32.5 g bentonite, 3.25 g cow manure, 6.5 g lime, 542.75g quartz sand, 227.5 ml water). Similar to Korte et al. (1984), chloroacetamide was used as reference substance. The experiment was carried out in accordance with the “Guideline for the testing of the toxicity of chemicals and plant treatment products in earthworms (Eisenia foetida Sav.)”. The 28 day LC₅₀ was 3,550 mg/kg of substrate.

Based on the findings summarised above thiourea is considered to be non-toxic to earthworms.

In addition, Glazer & Orion (1984) investigated the effects of thiourea on the development of nematodes. Excised tomato roots, growing on basal medium and inoculated with eggs of Meloidogyne javanica, were exposed to thiourea concentrations in the range of 6‒46 mg/litre. A 96-h exposure at thiourea concentrations of 12 mg/litre inhibited nematode development: Only 36 % matured to adults (in the untreated control: 90%) after an observation period of 4 weeks. For M. javanica (second larval stage), Tylenchulus semipenetrans (second larval stage), and Pratylenchus thornei (adult and juvenile organisms), no increased mortality was found after incubation in aqueous solutions of thiourea at concentrations up to 100 mg/litre for 96 h. The authors furthermore demonstrated that thiourea is taken up via the plant roots and that the nematicidal effect is systemic.

The endpoints investigated by Glazer & Orion (1984) are non-standard and the publication was rated as non-reliable due to deficiencies in documentation. The results are referenced for information purposes only.