Pirimiphos-methyl

Toxicity to terrestrial arthropods

Link to relevant study record(s)

Reference

Endpoint:

toxicity to bees: acute oral

Remarks:

and acute contact

Type of information:

experimental study

Adequacy of study:

key study

Study period:

Not specified

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

study well documented, meets generally accepted scientific principles, acceptable for assessment

Qualifier:

no guideline followed

Principles of method if other than guideline:

Oral and contact toxicities were determined by feeding worker honeybees solutions of a formulation with the test substance in an acetone/sucrose solvent, and by applying the chemical in acetone to the thorax of anaesthetised bees. The oral and contact 24-h LD50 values were then determined.

GLP compliance:

not specified

Application method:

other: Oral and contact

Analytical monitoring:

no

Vehicle:

yes

Remarks:

5% acetone and 20% sucrose

Details on preparation and application of test substrate:

ORAL EXPOSURE
- Preparation of test substance: The fonnulated chemical was serially diluted in water containing 5% acetone plus 20% sucrose to give concentrations of between 0.1 and 500 μg a.i./mL.
- Application of test substance: 0.2 mL of a concentration was fed to each group of ten bees giving an oral dose range of 0.002 to 10 μg a.i./bee. Control bees were fed the diluent only.

CONTACT EXPOSURE
- Preparation of test substance: Solutions of 'Actellic' were prepared at concentrations ranging from 10 to 1000 μg a.i./mL using acetone as the solvent.
- Application of test substance: A 1 μL drop of solution was placed on the ventral thorax of each anaesthetised bee, giving a dose range of 0.01 to 1 μg a.i./bee. Control bees were treated with a 1 μL drop of acetone only.

Test organisms (species):

Apis mellifera

Animal group:

Hymenoptera (honeybees)

Details on test organisms:

- Common name: Worker honeybee

Study type:

laboratory study

Limit test:

no

Total exposure duration:

24 h

Test temperature:

not reported

Humidity:

not reported

Photoperiod and lighting:

not reported

Details on test conditions:

TEST SYSTEM (Oral exposure)
- Test container: Cage
- No. of organisms per container: 10
- No. of replicates per treatment group: 3
- No. of replicates per vehicle control: 3
- No. of test: 10

TEST SYSTEM (Contact exposure)
- Test container: Cage
- No. of organisms per container: 10
- No. of replicates per treatment group: 3
- No. of replicates per vehicle control:3
- No. of test: 5

EFFECT PARAMETERS MEASURED
- Oral exposure: Twenty-four hour and forty-eight hour mortalities were recorded for the initial test. As there was no obvious increased effect after 48 hours, subsequent tests were recorded after 24 hours only.
- Contact exposure: The number of bees dead twenty-four hours after treatment were recorded; there being no obvirus increased effect after 48 hours in the initial test.

VEHICLE CONTROL PERFORMED: Yes (both oral and contact exposure)

Nominal and measured concentrations:

- Oral exposure nominal concentration: 0 (solvent control), 0.002, 0.02, 0.1, 0.3, 0.5, 1, 2 and 10 µg a.i./bee
- Contact exposure nominal concentration: 0 (solvent control), 0.01, 0.05, 0.1, 0.15, 0.25, 0.5 and 1 μg a.i./bee

Reference substance (positive control):

no

Key result

Duration:

24 h

Dose descriptor:

LD50

Effect conc.:

0.22 µg per animal

Nominal / measured:

nominal

Conc. based on:

act. ingr.

Basis for effect:

mortality

Remarks on result:

other: 95% C.I.: 0.18 - 0.28 µg a.i./bee

Key result

Duration:

24 h

Dose descriptor:

LD50

Effect conc.:

0.12 µg per animal

Nominal / measured:

nominal

Conc. based on:

act. ingr.

Basis for effect:

mortality

Remarks on result:

other: 95% C.I.: 0.11 - 0.14 µg a.i./bee

Details on results:

An overview of the results is provided in Table 1 – Table 4 in ‘Any other information on results incl. tables’.
- Oral toxicity: After 24 hours exposure period, the bees did not recover from anesthetic (CO2) in test 4, 5, and 6. High mortality was observed in test 8 and 9. The rest tests (test 1, 2, 3, 7 and 10) were used in statistically analysis to determine LD50 of oral toxicity. In those tests, ≤ 3 bees were dead in all triplicate control, 0.002 and 0.1 µg a.i./bee treated groups. Only one of the triplicate 0.1 µg a.i./bee groups in test 1 showed 8 bees dead, and the rest test groups were ≤ 3 bees dead. More than 5 out of 10 bees were dead in most ≥ 0.3 µg a.i./bee treated groups. 100% mortality was observed in 2 and 10 µg a.i./bee exposure groups.

- Contact toxicity: After 24 hours exposure period, ≤ 3 bees were dead in all triplicate control in all tests. Only one of the triplicate 0.01 µg a.i./bee groups and 0.1 µg a.i./bee groups in test 1 showed 5 out of 8 bees dead and 5 out of 9 bees dead, respectively. All the rest test groups of 0.01, 0.05 and 0.1 µg a.i./bee were ≤ 4 dead bees. More than 5 out of 10 bees were dead in most ≥ 0.15 µg a.i./bee treated groups. 100% mortality was observed in all ≥ 0.25 µg a.i./bee exposure groups.

Reported statistics and error estimates:

These tests were analysed statistically by plotting logit transformation on percentage kill against the log dose in μg of active ingredient per bee. Control death were accounted for by Abbotts correction factor.
For oral exposure, five tests with no more than four control deaths were statistically analysed. For contact exposure, tests with no more than 10% control mortalities were analysed statistically.

Table 1. Oral toxicity of the test substance (‘Actellic' 50% w/v e.c.) to worker honeybees (24hr mortalities – nos. dead out of 10).

µg a.i. /mL solution	µ.g a.i./ bee	Test 1	Test 2	Test 3	Test 7	Test 10
500	10	10 10 10	/ / /	/ / /	/ / /	/ / /
100	2	10 10 10	/ / /	/ / /	/ / /	/ / /
50	1	10 10 7	10 10 8	10 10 9	10 10 10	10 10 10
25	0.5	8 10 10	10 10 10	10 10 8	9 10 4	8 10 10
15	0.3	10 3 1	5 2 6/9	3 6 6	5 3 2	6 6 10
5	0.1	8 3 1	7/9 0 2	2 1 1	2 2 0	3 3 3
1	0•02	2 1 0	1/8 1 2	0 2 2	1 1 2	1 2 2
0.1	0.002	/ / /	2 2 0	1 0 0	0 0 0	0 0 0
Control	0	3 0 0	2 1 0	1 2 1	0 0 3	0 1 0

Note. Tests 4, 5, 6 - bees did not recover from anesthetic (CO2).

Tests 8, 9 - high mortalities at all concentrations and in controls.

Where fewer than 10 bees were to be assessed (due to escape) this was taken into account statistically.

 

Table 2. Oral Toxicity of the test substance to bees

Test No.	log (LD50)	LD50	95% C.I. for LD 50
Test 1 Standard error	- 0.687 0.165	0.20	0.09 – 0.45
Test 2 Standard error	- 0.686 0.127	0.20	0.11 – 0.38
Test 3 Standard error	- 0.557 0.062	0.27	0.20 – 0.37
Test 7 Standard error	- 0.467 0.069	0.34	0.24 – 0.47
Test 10 Standard error	- 0.881 0.093	0.13	0.08 – 0.20
Tests 1, 2, 3, 7,10 Standard error	- 0.653 0.047	0.22	0.18 – 0.28

Table 3. Contact toxicity of the test substance (‘Actellic' 50% w/v e.c.) to worker honeybees (24hr mortalities – nos. dead out of 10).

µg a.i. /mL solution	µg a.i./ bee	Test 1	Test 2	Test 3	Test 4	Test 5
1000	1	10 10 10	10 10 10	10 10 10
500	0.5	10 10 10	10 10 10	10 10 10	10 10 10	10 10 10
250	0.25	10 10 10	10 10 10	10 10 10	10 10 10	10 10 10
150	0.15	/ / /	/ / /	/ / /	7 4 6	4 6 4
100	0.1	1 1 3	2/9 5/9 2	0 2 3	2 3 1	1 1 4
50	0.05	0 1 1	4 0 0	1 2 1/9	0 1 2	0 2 1
10	0.01	5 1 0	2/8 1/9 5/8	0/9 3/9 0	1 0 3	0 1 0
Control	0	1 0 2	2 0 0	1 1 1/8	0 3 0	1 1 0

Table 4. Contact Toxicity of the test substance to bees

Test No.	log (LD50)	LD50	95% C.I. for LD 50
Test 1 Standard error	-0.886 0.085	0.12	0.08 – 0.19
Test 2 Standard error	-1.074 0.118	0.08	0.04 – 0.14
Test 3 Standard error	-0.885 0.058	0.13	0.09 – 0.17
Test 4 Standard error	-0.866 0.043	0.13	0.11 – 0.16
Test 5 Standard error	-0.843 0.035	0.14	0.12 – 0.17
Tests 1 - 5 Standard error	-0.898 0.029	0.12	0.11 – 0.14

Validity criteria fulfilled:

not specified

Conclusions:

Based on the findings, the LD50 of oral toxicity was determined to be 0.22 µg a.i./bee with 95% confidence interval of 0.18 – 0.28 µg a.i./bee. The LD50 of contact toxicity was determined to be 0.12 µg a.i./bee with 95% confidence interval of 0.11 – 0.14 µg a.i./bee.

Executive summary:

The acute contact and oral toxicity of the test substance to arthropods was investigated in the following study using worker honeybee as test organism. The study was not in accordance with a international standardised guideline and was not performed in compliance with GLP criteria. The study was therefore considered to have a Klimisch 2 reliability score. For the oral toxicity test, the test substance was dissolved in an water/acetone/sucrose concentration of which 0.2 mL was fed groups of ten bees, giving an oral dose of 0.002, 0.02, 0.1, 0.3, 0.5, 1, 2 and 10 µg a.i./bee. In addition, a solvent control of the diluent was included in the test as well. For each concentration, three replicate cages of ten bees were used per test. Ten tests were conducted in total for oral exposure. For the contact toxicity test, three replicate cages of ten bees were used for each concentration per test. In total, 5 tests were conducted for contact exposure. The test substance was dissolved at different concentrations in acetone. A 1 μL drop of the prepared solution was placed on the ventral thorax of each anesthetised bee, giving a contact dose of 0.01, 0.05, 0.1, 0.15, 0.25, 0.5 and 1 μg a.i./bee.

 

In the oral toxicity test, mortality after 24 hours was observed at 0.02 µg a.i./bee and increased with increasing dose levels in a clear dose-responsive manner. At 0.5 µg a.i./bee, mortality was close to 100%. Based on the findings, the LD50 of oral toxicity was determined to be 0.22 µg a.i./bee with 95% confidence interval of 0.18 – 0.28 µg a.i./bee. In the contact toxicity test, mortality after 24 hours was already observed at 0.01 µg a.i./bee and increased with increasing dose levels in a clear dose-responsive manner. At 0.25 µg a.i./bee, mortality was 100%. The LD50 of contact toxicity was determined to be 0.12 µg a.i./bee with 95% confidence interval of 0.11 – 0.14 µg a.i./bee

Description of key information

The 24-h LD50 = 0.22 µg a.i./bee (oral dosing), worker honeybee, no guideline followed, Ward 1976

The 24-h LD50 = 0.12 µg a.i./bee (contact dosing), worker honeybee, no guideline followed, Ward 1976

Additional information

The acute contact and oral toxicity of the test substance to arthropods was investigated in the following study using worker honeybee as test organism. The study was not in accordance with an international established guideline and was not performed in compliance with GLP criteria. However, the study was well documented and meets generally accepted scientific principles. The study was therefore considered to have a Klimisch 2 reliability score and was acceptable for assessment. For the oral toxicity test, the test substance was dissolved in an water/acetone/sucrose concentration of which 0.2 mL was fed groups of ten bees, giving an oral dose of 0.002, 0.02, 0.1, 0.3, 0.5, 1, 2 and 10 µg a.i./bee. In addition, a solvent control of the diluent was included in the test as well. For each concentration, three replicate cages of ten bees were used per test. Ten tests were conducted in total for oral exposure. For the contact toxicity test, three replicate cages of ten bees were used for each concentration per test. In total, 5 tests were conducted for contact exposure. The test substance was dissolved at different concentrations in acetone. A 1 μL drop of the prepared solution was placed on the ventral thorax of each anesthetised bee, giving a contact dose of 0.01, 0.05, 0.1, 0.15, 0.25, 0.5 and 1 μg a.i./bee.

 

In the oral toxicity test, mortality after 24 hours was observed at 0.02 µg a.i./bee and increased with increasing dose levels in a clear dose-responsive manner. At 0.5 µg a.i./bee, mortality was close to 100%. Based on the findings, the LD50 of oral toxicity was determined to be 0.22 µg a.i./bee with 95% confidence interval of 0.18 – 0.28 µg a.i./bee.

In the contact toxicity test, mortality after 24 hours was already observed at 0.01 µg a.i./bee and increased with increasing dose levels in a clear dose-responsive manner. At 0.25 µg a.i./bee, mortality was 100%. The LD50 of contact toxicity was determined to be 0.12 µg a.i./bee with 95% confidence interval of 0.11 – 0.14 µg a.i./bee.