Urea

Bioaccumulation: terrestrial

Administrative data

Endpoint:

bioaccumulation: terrestrial

Type of information:

(Q)SAR

Adequacy of study:

weight of evidence

Reliability:

3 (not reliable)

Rationale for reliability incl. deficiencies:

results derived from a valid (Q)SAR model, but not (completely) falling into its applicability domain, and documentation / justification is limited

Data source

Reference

Reference Type:

publication

Title:

BIOACCUMULATION IN THE SOIL TO EARTHWORM SYSTEM

Author:

Des W. CONNELL and Ross D. MARKWELL

Year:

1990

Bibliographic source:

Chemosphere, Vol. 20, Nos. 1-2, pp. 91-100, 1990

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

OECD Guideline 317 (Bioaccumulation in Terrestrial Oligochaetes)

GLP compliance:

no

Test material

Test material information

Constituent 1

Reference substance name:

Urea

EC Number:

200-315-5

EC Name:

Urea

Cas Number:

57-13-6

Molecular formula:

CH4N2O

IUPAC Name:

urea

Details on test material:

It is assumed that the purity is 100%

Results and discussion

Any other information on results incl. tables

The sources of variation in this study are substantial. Several sources of data from experiments conducted under different conditions are included. Also, it has been demonstrated (Chessels et. al., 1988) that pesticides in soils establish concentration patterns and gradients due to varying environmental conditions, leading to irregular exposure. Despite these limitations, the data are broadly consistent with the transfer of lipophilic compounds through a three phase system involving soil to soil water to organism partitioning, analogous to that observed in oligochaete worms. This is a passive process and is principally dependent on the lipid content of the worms and the organic carbon content of the soil. Transfer from soil to soil water can be described by the same relationships established for sediment to water equilibria. The transfer from soil water to earthworm is described by:

log Kb = log Kow - 0.6

This relationship is consistent with the theoretically derived equation for bioconcentration, which has been found to apply to bioconcentration by aquatic organisms. The bioaccumulation factor derived from the three phase partition theory is in accord with the observed bioaccumulation factor. It demonstrates a weak dependence on the log Kow value and strong dependence on the lipid content of the organism and the organic matter content of the soil.

The Log Kow for urea is -1.73.

Hence the log Kb as calculated with the equation above is -2 .23.

This indicates a low potential for bioaccumulation of urea.

Applicant's summary and conclusion

Conclusions:

Low potential for bioaccumulation.

Executive summary:

The sources of variation in this study are substantial. Several sources of data from experiments conducted under different conditions are included. Also, it has been demonstrated (Chessels et. al., 1988) that pesticides in soils establish concentration patterns and gradients due to varying environmental conditions, leading to irregular exposure. Despite these limitations, the data are broadly consistent with the transfer of lipophilic compounds through a three phase system involving soil to soil water to organism partitioning, analogous to that observed in oligochaete worms. This is a passive process and is principally dependent on the lipid content of the worms and the organic carbon content of the soil. Transfer from soil to soil water can be described by the same relationships established for sediment to water equilibria. The transfer from soil water to earthworm is described by:

log Kb = log Kow - 0.6

This relationship is consistent with the theoretically derived equation for bioconcentration, which has been found to apply to bioconcentration by aquatic organisms. The bioaccumulation factor derived from the three phase partition theory is in accord with the observed bioaccumulation factor. It demonstrates a weak dependence on the log Kow value and strong dependence on the lipid content of the organism and the organic matter content of the soil.

The Log Kow for urea is -1.73.

Hence the log Kb as calculated with the equation above is -2 .23.

This indicates a low potential for bioaccumulation of urea.