Urea

Short-term toxicity to aquatic invertebrates

Link to relevant study record(s)

Reference

Endpoint:

short-term toxicity to aquatic invertebrates

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Published public domain study

Qualifier:

according to guideline

Guideline:

other: DIN 38412 Teil 11 (modified)

Deviations:

yes

Remarks:

no information available

Principles of method if other than guideline:

Acute toxicity to Daphnia, immobilisation test

GLP compliance:

not specified

Specific details on test material used for the study:

Details on properties of test surrogate or analogue material (migrated information):
Not applicable

Analytical monitoring:

not specified

Details on sampling:

No information available

Vehicle:

not specified

Details on test solutions:

No information available

Test organisms (species):

Daphnia magna

Details on test organisms:

Daphnia magna straus, of the IRCHA strain. Cultures were held in 2 litre beakers filled with at least 1.6 litres of tap water.
A total of 60 cultures were prepared, producing 24 hour old animals daily. The mother animals from these cultures were transferred daily (Monday to Friday) into freshly prepared culture glasses by means of wide-mouthed pipettes. The young animals produced from Tuesday to Friday of each week were accumulated daily on a DIN sieve 0.315 mm and used at test organisms. The young animals produced from Friday to Monday of each week were separated according to size using test sieves DIN 0.630 and 0.315 mm. The size classes were cultivated separately for breeding purposes. The gaps which occurred in the group of mother animals were filled from these animals which were kept in separate supply. Those which could be sifted out on a DIN test sieve 1.25 mm were used when the number of mother animals began to decrease below 30 per glass.
All culture glasses were covered with hour glasses and kept on white table tops. The cultures were fed daily. On Monday and Friday of each week the tap water for each culture was renewed, on Friday the culture glass was also replaced. This was done at the same time as the selective removal of animals described above.
The culture water was tempered, chlorine free, oxygen saturated tap water (hardness 16° d.H., pH 7.6-7.7). Tap water was used 24 hours after it was drawn, and the tap had run for a minimum of 1 hour prior to drawing.
Standardised dry feed "Mikrozell" was fed to the standard cultures. It was suspended 30 g/l of tap water and 10 ml suspension was added to each culture glass.
The temperature of the holding room was maintained at 20°C. The room was illuminated for 9 hours per day by means of Osram fluorescent tubes, colour 25 (room illumination intensity 2.5 W/m²); daylight was screened out.

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

24 h

Post exposure observation period:

No information available

Hardness:

The sum of calcium and magnesium ions in the artificial test water was 2.5 mmole/litre. The molar ratio of sodium to potassium ions was 10:1.

Test temperature:

20°C

pH:

Test medium: 8.0±0.2 (the pH of the test medium was not corrected following addition of the test substance).

Dissolved oxygen:

The test water was aerated to the oxygen saturation value.

Salinity:

No information/

Nominal and measured concentrations:

Nominal

Details on test conditions:

Artificial test water (test medium) was used for the toxicity test (see below for composition). The test substance was quantitatively dissolved in the test medium until optically clear, by means of a magnetic mixer in closed containers. The test mixtures were prepared as a double parallel dilution series, each with ten 24 hour old Daphnia per culture vessel. The vessels were covered with a loose layer of filter paper and were kept in an incubation cabinet for 24 hours at 20°C. At the end of the exposure period, the animals that could still swim were counted.
The pH and the oxygen content was measured in the test and control vessels at the end of the test period.

Reference substance (positive control):

yes

Remarks:

Potassium dichromate

Duration:

24 h

Dose descriptor:

EC50

Effect conc.:

> 10 000 mg/L

Nominal / measured:

nominal

Conc. based on:

dissolved

Basis for effect:

mobility

Details on results:

The 24 hour EC50 in Daphnia was > 10000 mg/l.

Results with reference substance (positive control):

Potassium dichromate; the average EC50 was 1.3 mg/l.

Reported statistics and error estimates:

The Schleicher and Schuell probablility network, calculation of 95% confidence limits and Chi-square.

The 24 hour EC₅₀ in Daphnia was > 10000 mg/l.

Validity criteria fulfilled:

not specified

Conclusions:

The 24 hour EC50 in Daphnia was > 10000 mg/l; urea is not acutely toxic to daphnids.

Executive summary:

The 24 hour EC₅₀ in Daphnia was > 10000 mg/l; urea is not acutely toxic to daphnids.

Description of key information

Low toxicity was demonstrated in Daphnia, freshwater snails and Aedes egypti larvae.

Key value for chemical safety assessment

Fresh water invertebrates

Fresh water invertebrates

Dose descriptor:

EC50

Effect concentration:

10 000 mg/L

Additional information

The 24 hour EC₅₀ for urea in Daphnia was reported to be >10000 mg/l; urea is not acutely toxic to daphnids. The 24 hour LC₅₀ values for freshwater snail eggs, juveniles and adults were reported to be 14241 mg/l, 18255 mg/l and 22998 mg/l. Following 48 hour exposure, the LC₅₀value for adults was calculated to be 13477 mg/l.   In another study, the 24 hour LC₅₀values for eggs, juvenile and adult snails were reported to be 13532 mg/l, 24504 mg/l and 26024 mg/l, respectively. Following 48 hours exposure, the LC₅₀value for adults was calculated to be 21412 mg/l. It is concluded that, under normal laboratory conditions, urea displays low molluscicidal activity. The 4 hour LC₅₀ in mosquito (Aedes aegypti) larvae is reported to be 60000 mg/l.