Prometryn

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:

12 to 14 Sep 1989 and 21 to 23 Sep 1989

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:

The test was conducted according to the test guidelines specified under the UK Control of Pesticides Regulations.

GLP compliance:

yes

Application method:

other: Contact and oral

Analytical monitoring:

yes

Vehicle:

yes

Remarks:

acetone

Details on preparation and application of test substrate:

PREPARATION OF TEST SOLUTIONS
The test substance was weighted and dissolved in acetone (glass distilled grade)(SOP ERG/055). The range of concentrations (contact doses : 25, 50 and 100 µg/bee and oral dosing solutions: 0.1, 0.2 0.4, 0.8, 1.6 and 3.2 mg/ml) were obtained by serial dilution , using acetone for contact-dosing , or sucrose (20%), for oral-dosing. Test solutions was then stored in closed glass flasks in a refrigerator at 4°C until transported by road to Luddington, where they will again be stored at 4°C until used for testing. After completion of the study, remaining supplies of the test substance will be archived at the test facility.

APPLICATION OF THE TEST SUBSTANCE
Test methods followed SOP ERG/022 for oral-dosing contact-dosing, and SOP ERG/023 for contact-dosing, with the following amendments:
- The feeding bottles fitted to test cages consisted of a modified Pasteur pipette inserted through the cork at the top of the cage. The narrow end of the pipette will be bent into a U-shape , allowing bees to feed from its tip. Test solution was introduced through the other end (outside the cage), which was plugged with cotton wool. To determine the amount of test solution consumed in oral tests, the entire feeder was weighed (to 0.001 g) before and after the 24 hour
feeding period.
- Bees were handled using forceps instead of a brush, as experience at Luddington had shown this to be more efficient.

Test organisms (species):

Apis mellifera

Animal group:

Hymenoptera (honeybees)

Details on test organisms:

TEST ORGANISM
- Common name: Honeybee
- Source: Obtained from colonies at Luddington
- Bees with a low incidence of disease are selected for testing, after examination according to SOP NBU/001.

Study type:

laboratory study

Limit test:

no

Total exposure duration:

48 h

Details on test conditions:

TEST SYSTEM
- No. of organisms per container (treatment): 10
- No. of replicates per treatment group: 3
- No. of replicates per vehicle control: 3
- Duration of test: Oral: 48 hours; Contact: 48 hours

RANGE FINDING STUDY
- Range-finding tests were carried out on 22-24 August and 29-31 August 1989.
- For the range-finding test of the contact exposure, 4 dose levels were used, 0.0996, 0.996, 9.96 and 99.6 µg of the test substance per bee. There were 2 replicate batches of 10 bees at each level and two batches of bees given a control dose of acetone.
- For the range-finding test of the oral exposure, 4 dose levels were used as well, 0.1, 1.0, 10.0, 49.8 µg of the test substance per bee. There were 2 replicate batches of 10 bees at each level and two batches of bees given a control dose of acetone in 20% sucrose.
- The results indicated very little bee mortality up to 99.6 µg/bee (contact dose) and 0.5 rag/ml (oral dosing solution). Therefore, the following dose levels:
Contact doses: 50 and 100 µg/bee
Oral dosing solutions : 0.1, 0.2 0.4, 0.8, 1.6 and 3.2 mg/ml

Nominal and measured concentrations:

- Contact nominal doses: 0 (solvent control), 24.9, 49.8 and 99.7 µg/bee
- Oral nominal dosing solutions: 0 (solvent control), 100, 200, 400, 810, 1610, 3230 µg/mL

Reference substance (positive control):

no

Key result

Duration:

48 h

Dose descriptor:

LD50

Effect conc.:

> 99 µg per animal

Nominal / measured:

nominal

Conc. based on:

act. ingr.

Basis for effect:

mortality

Remarks on result:

other: Contact test

Key result

Duration:

48 h

Dose descriptor:

LD50

Effect conc.:

> 130 µg per animal

Nominal / measured:

nominal

Conc. based on:

act. ingr.

Basis for effect:

mortality

Remarks on result:

other: Oral test

Details on results:

- Contact exposure: After 48 hours testing period, 1 bee died in one of the triplicate control groups, 9 bees escaped from the second control group and no mortality or escaping occurred in the third control group. For the substance treated groups (24.9, 49.8 and 99.7 µg/bee, triplicate groups of each dosage), either no mortality or only 1 in 10 bees died after 48 hours of exposure. Thus, the mortality at 48 hours after dosing did not allow calculation of the median lethal dose, because mortality was substantially less the than 50% at the highest dose (99.7 µg/bee) tested. Accordingly, it was concluded that LC50 was > 99 µg/bee.

- Oral exposure: After 48 hours testing period, 7 bees died in one of the triplicate control groups, the rest two control groups with no mortality occurred. For the average taken amount of 3.5, 4.1, 12.9, 97.8 and 130.6 µg test substance/bee groups,1, 3, 3, 7 and 1 bees were dead, respectively. Thus, the mortality at 48 hours after dosing did not allow calculation of the median lethal dose, because mortality was substantially less the than 50% at the highest dose (64.6 µg/bee) tested. Accordingly, it was concluded that LC50 was > 130 µg/bee.

Reported statistics and error estimates:

Since the results demonstrated insufficient mortality at the highest dose level to permit a valid probit analysis, toxicity was expressed at the LD50 being greater than that dose level.

Table 1. Results of contact dosing tests

Dose (µg/bee)	Cage No.	Number dead
		4 hrs	24 hrs	48 hrs
Control	111	0	1	1
	110*	0	0	0
	109	0	0	0
24.9	108**	0	10	10
	107	0	1	1
	106	0	1	1
49.8	105	1	10	10
	104	0	1	1
	103	0	1	1
99.7	102**	0	9	10
	101	0	1	1
	100	0	1	1

 

* 9 bees escaped from cage 110
** no food taken by bees in these cages

 

Table 2. Results of oral dosing tests

Concentration* (µg/ml)	Cage No.	Average amount taken (µg/bee)	Number dead
			4 hrs	24 hrs	48 hrs
Control	147	-	0	0	0
	146	-	0	6	7
	145	-	0	0	0
100 (2.0 µg/bee)	144	5.4	0	0	0
	143	3.5	0	1	1
	142	4.1	0	1	3
200  (4.0 µg/bee)	141	9.0	0	0	0
	140	7.0	0	0	0
	139	10.3	0	0	0
400  (8.0 µg/bee)	138	15.5	0	0	0
	137	12.9	0	2	3
	136	19.0	0	0	0
810  (16.2 µg/bee)	135	28.9	0	0	0
	134	40.2	0	0	0
	133	28.2	0	0	0
1610  (32.2 µg/bee)	132	56.1	0	0	0
	131	88.6	0	0	0
	130	64.8	0	0	0
3230 (64.6 µg/bee)	129	130.6	0	1	1
	128	97.8	0	3	7
	127	120.0	0	0	0

*values In brackets are expected doses per bee based on assumed likely consumption of 20 µL.

Validity criteria fulfilled:

not specified

Conclusions:

The 48-hour contact LD50 for the test material was > 99 μg/bee, the highest concentration tested. The 48-hour oral LD50 for the test material was > 130 µg/bee, the highest concentration tested.

Executive summary:

The acute contact and oral toxicities to terrestrial arthropods were investigated using honeybee (Apis mellifera) as test organism. The study was conducted according to the test guidelines of the UK Control of Pesticides Regulations, which are similar to the relevant OECD TG, and in compliance with GLP. The range of concentrations (contact doses: 24.9, 49.8 and 99.7 µg/bee; oral dosing solutions: 0.1, 0.2, 0.4, 0.81, 1.61 and 3.23 mg/mL) were obtained by serial dilution, using acetone for contact-dosing, or 20% sucrose in water  for oral-dosing. For the contact test, individual bees were treated topically with the desired dose and then observed for a period of 48 hours. Three replicate groups with ten bees each were set up for each test group. Bees were fed non-treated sucrose solution during the test period. A solvent control group (acetone) was also included. In the oral exposure test, the bees in groups of 10 were offered treated diet for 24 hours, resulting in maximum average uptake of 5.4, 10.3, 19.0, 40.2, 88.6 and 130.6 µg/bee in individual replicates of the different test groups as determined by reweighing the feeding tube after the 24-hour exposure period. A control group (20% sucrose) was also included. After treatment, bees were observed for toxic symptoms for an additional 24 hours.

After 48 hours, the mortality in the three test groups of the study on acute contact toxicity did not differ significantly from the mortality in the control group. Accordingly, it was concluded that the LC50 was >99 µg/bee.

After 48 hours, the mortality in the test groups of the study on acute oral toxicity did not differ significantly from the mortality in the control group. Accordingly, it was concluded that the LC50 was >130 µg/bee, the maximum dose consumed in one replicate group of bees of the maximum dose level.  

Description of key information

All available data were assessed and the most representative study is included here as key study.

The 48-h LD50 > 99 µg/bee (contact dosing), Apis mellifera, mortality, no guideline followed, Greig-Smith 1990

The 48-h LD50 > 130 µg/bee (oral dosing), Apis mellifera, mortality, no guideline followed, Greig-Smith 1990

Additional information

Effects on bees

The acute contact and oral toxicities to terrestrial arthropods were investigated using honeybee (Apis mellifera) as test organism. The study was conducted according to the test guidelines of the UK Control of Pesticides Regulations, which are similar to the relevant OECD TG, and in compliance with GLP. The range of concentrations (contact doses: 24.9, 49.8 and 99.7 µg/bee; oral dosing solutions: 0.1, 0.2, 0.4, 0.81, 1.61 and 3.23 mg/mL) were obtained by serial dilution, using acetone for contact-dosing, or 20 % sucrose in water for oral-dosing. For the contact test, individual bees were treated topically with the desired dose and then observed for a period of 48 hours. Three replicate groups with ten bees each were set up for each test group. Bees were fed non-treated sucrose solution during the test period. A solvent control group (acetone) was also included. In the oral exposure test, the bees in groups of 10 were offered treated diet for 24 hours, resulting in maximum average uptake of 5.4, 10.3, 19.0, 40.2, 88.6 and 130.6 µg/bee in individual replicates of the different test groups as determined by reweighing the feeding tube after the 24-hour exposure period. A control group (20 % sucrose) was also included. After treatment, bees were observed for toxic symptoms for an additional 24 hours.

After 48 hours, the mortality in the three test groups of the study on acute contact toxicity did not differ significantly from the mortality in the control group. Accordingly, it was concluded that the LC50 was >99 µg/bee.

After 48 hours, the mortality in the test groups of the study on acute oral toxicity did not differ significantly from the mortality in the control group. Accordingly, it was concluded that the LC50 was >130 µg/bee, the maximum dose consumed in one replicate group of bees of the maximum dose level.  

Effects on other non-target terrestrial arthropods

Several other studies on representative non-target arthropods (ground beetle, staphylinid beetle, parasitic wasp and green lacewing) have been performed to investigate the toxicity of the test substance in formulation. Tier 1 studies were performed exposing the parasitic wasp and green lacewing to spray residues on glass plates. In the Tier 1 tests with the beetle species, the applications were made to sand substrate including the beetles. Effects on survival and parasitisation rates were observed in parasitic wasp after application of the test substance in formulations up to 2500 g ai/ha (equivalent to 3.33 mg/kg soil dw) on glass plates representing a worst case exposure scenario. The parasitic wasp was the most sensitive organism, since no effects on survival and reproduction or feeding activity were observed in the other species at this rate. It is expected that the majority of species of the non-target arthropod community will not be at risk to the test substance.