Nuclease, deoxyribo-

Ecotoxicological Summary

Hazard for aquatic organisms

Freshwater

Hazard assessment conclusion:

PNEC aqua (freshwater)

PNEC value:

8.1 µg/L

Assessment factor:

1 000

Extrapolation method:

assessment factor

PNEC freshwater (intermittent releases):

81 µg/L

Marine water

Hazard assessment conclusion:

PNEC aqua (marine water)

PNEC value:

0.81 µg/L

Assessment factor:

10 000

Extrapolation method:

assessment factor

STP

Hazard assessment conclusion:

PNEC STP

PNEC value:

65 000 µg/L

Assessment factor:

1

Extrapolation method:

assessment factor

Sediment (freshwater)

Hazard assessment conclusion:

no exposure of sediment expected

Sediment (marine water)

Hazard assessment conclusion:

no exposure of sediment expected

Hazard for air

Air

Hazard assessment conclusion:

no hazard identified

Hazard for terrestrial organisms

Soil

Hazard assessment conclusion:

PNEC soil

PNEC value:

9.7 µg/kg soil dw

Extrapolation method:

equilibrium partitioning method

Hazard for predators

Secondary poisoning

Hazard assessment conclusion:

no potential for bioaccumulation

Additional information

Deoxyribonuclease was tested for acute toxicity, including read-across studies.

Fish: Deoxyribonuclease as not tested, however, Alpha-amylase was not toxic at the the tested concentration of 100 mg/L (58.3 mg aep/L) and thus the NOEC was determined to be 100 mg/L (58.3 mg aep/L). The LC50 value could not be determnined due to the absence of toxicity of the test compound at the tested concentration. Due to the similar nature of enzymes, similar results can be expected for the test substance deoxyribonuclease.

Daphnia magna: Exposure of freshwater invertebrate Daphnia magna to the test item has been investigated and gave the following results based on the geometric mean measured test concentrations:
EC50 = 1546 (932 – 2571) mg enzyme concentrate dry matter/L, equivalent to 214 mg active enzyme protein (aep)/L (analytically measured as aep).
NOEC = 852 mg enzyme concentrate dry matter/L.
LOEC = 1704 mg enzyme concentrate dry matter/L.

Algae: Exposure of Raphidocelis subcapitata to the test item gave the following results based on the geometric mean measured test concentrations:
EC50 = 59 (26 – 108) mg enzyme concentrate dry matter/L, equivalent to 8.1 mg active enzyme protein (aep)/L (analytically measured as aep).
NOEC = <5.3 mg enzyme concentrate dry matter/L.
LOEC = ≤5.3 mg enzyme concentrate dry matter/L.

Inhibition control carried out in the test of ready biodegradability showed no inhibition of the activated sludge inoculum at an enzyme concentration above the expected levels in inlet to sewage treatment plants (STPs). Monitoring of enzymes in the inlet to municipal STPs (in Denmark) resulted in concentrations of less than 2 µg aep/L which are below the initial concentration used in tests for ready biodegradability, where no inhibitory effects were observed. It is concluded that a study on activated sludge respiration inhibition does not need to be conducted. The biodegradation studies are considered fully applicable for deoxyribonuclease and therefore, deoxyribonuclease is not considered to be toxic to microorganisms.

The lowest EC50 value was detected for daphnids and was determined to be 0.89 mg active enzyme protein/L. This value was used for PNEC derivation and the assessment factors 1000 and 10000 were applied for fresh and marine water, respectively.

 

The PNEC value for STP is based on actual measurements of enzyme concentration in STP connected to manufacturing site. Up to 65000 µg aep/L were detected in STP connected to manufacturing site and since there was no negative impact observed, this concentration is the estimated PNEC value for STP.

PNEC values for sediment exposure have not been derived because the enzyme is readily biodegradable, highly water soluble and has a very low potential for adsorption to sediments. Exposure of the sediment to toxicologically significant concentrations of the enzyme is thus not expected.

As no soil ecotoxicity data are available for the test enzyme, the PNEC for soil is based on the PNEC for surface water using the equilibrium partitioning method. PNEC soil was estimated to 9.7 µg active enzyme protein/kg soil.

The enzyme is not expected to cause any significant secondary poisoning as it is ready biodegradable and has no bioaccumulation potential. Furthermore, as the test enzyme is a protein it is expected to be degraded in the gastrointestinal tract. Thus, PNEC oral is not relevant.