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Additional ecotoxological information

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Endpoint:
additional ecotoxicological information
Type of information:
(Q)SAR
Adequacy of study:
key study
Study period:
1992
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: see 'Remark'
Remarks:
The estimate of toxicity to a wide range of aquatic groups is based on a relatively simple parameters namely the octanol water partition coefficient (Kow) and the molecular weight of each material. The estimate has been prepared by one of the foremost authorities on aquatic toxicology in Europe. On the basis of its simplicity and origin a reasonable level of reliability can be placed on the results.
Justification for type of information:
QSAR prediction: migrated from IUCLID 5.6

Data source

Reference
Reference Type:
publication
Title:
Unnamed
Year:
1992

Materials and methods

Test guideline
Qualifier:
no guideline required
Deviations:
not applicable
Principles of method if other than guideline:
This is a QSAR estimation based on the Kow and molecular weight of the test materials. As highly chlorinated compounds were considered to have unreliable Kow values these were determined by the slow stirring technique. Values for all other chemicals were attained from the THOR and other databases.
GLP compliance:
not specified
Remarks:
not applicable
Type of study / information:
QSAR estimation of the toxicity of 102 narcotic chemicals to 19 species of bacteria, algae, fungi, protozoans, coelentrates, rotifers, molluscs, crustaceans, insects, fish and amphibians. The estimates are based on recently developed equilibrium partitioning theory using the Kow and molecular weight of the test material. Using this theory predicted no effect levels (NEL's) can be predicted of concentrations in water, sediment and biota. The primary experimental work consisted of reviewing Kow experimental work to identify tests using the slow stirring method as the authors believe that the existing Kow values obtained from the literature may overestimate this value. Additional work involved searching databases and the published literature for data together with extensive modelling.

Test material

Reference
Name:
Unnamed
Type:
Constituent
Details on test material:
Not applicable

Results and discussion

Any other information on results incl. tables

In table 2 in the study the results of the QSAR analysis on 4 species of bacteria, 3 species of algae, one species of fungi, one species of protozoa, one species of coelenterate, one species of mollusc, 4 species of arthropods, one species of fish and 3 species of amphibians are reported (the table is too large for reproduction here). Similarly in table 3 which details QSARS for narcotic chemicals 2 species of bacteria, 3 species of arthropods, 5 species of fish and 2 species of amphibians are reported (the table is too large for reproduction here. The authors note that for narcotic chemicals QSARS based on the reproduction of Daphnia and early life stage toxicity to fish species are the most sensitive of those investigated. In addition the authors note that the HC5 values calculated have a very similar SE values ranging from -0.85 to 0.13.

ARC values calculated on the basis of experimental evidence are shown in the table below.

Parameter

Endpoint

Species

Log ARC

+/- SE

ARC

Number of studies

LC50/NOLC

48-hour/28 day mortality

Various species

0.2 +/- 0.13

1.6

36

LC50/NOEC

24-hour immobilisation

/20 day reproduction

D.magnia

0.86 +/- 0.53

7.2

8

LC50/NOEC

28 day mortality/and growth

B.rerio

0.52 +/- 0.14

3.3

6

LC50/NOEC

'96 hour mortality/32 day growth

P.promelas

1.05 +/- 0.31

11.2

7

LC50/NOEC

28 day growth/'96 hour mortality

B.rerio

P.proelas

0.96 +/- 0.37

9.1

25

LC50/NOEC

18 - 20 day reproduction

D.magnia

0.29 +/- 0.09

1.9

10

LC50/NOEC

'96 hour population growth

S.capricornetum

0.55 +/- 0.09

3.5

3

LC50/EC11

15 minutes luminescence

P.phsphoreteum

0.79 +/- 0.26

6.2

20

Based on the nineteen NOEC based QSARS from the second table in the report 81 HC5 calculations were conducted. The authors note that these values take the form of a curvilinear function of the Kow similar in shape to the lower confidence limits obtained through linear regression analysis of the mean assessment factor. The lowest estimate of toxicity using QSARS for D.magnia and P.promelas/B.rerio is approximately 10 with no variation of note between the different extrapolation procedures used. Tests to confirm these assumptions with respect to species sensitivity demonstrated that the assumptions were correct. In addition it was shown that calculated HC5 values for bioaccumulation and sediment were dependent on Kow values i.e the HC5 values for narcotic materials in sediment with an organic carbon content of 5% and biota with a lipid content of 5% is constant at approximately 10xE-5 mol/kg. At low Kow values the HC5 total is identical to the HC5 water with differences between the two values becoming apparent at Log Kow >4.0.

Applicant's summary and conclusion

Conclusions:
The most important conclusion reached by the authors is that based on this prediction model specifically for narcotic chemicals with no specific mode of action a safety factor of 10 is adequate for the aquatic environment providing it has applied to the lowest NOEC provided by data on D.magna or an early life cycle fish study. In practice in the Netherlands a further factor of 10 is applied to arrive at the politically expedient of so-called "negligible risk" for individual chemicals.
The values for a chemical with a Log Kow of 2.49 (1,1,1-trichloroethane)are as follows
Log HC5 values.
Dissolved (mol/L) = -5.37(mol/L), Total = -5.37, Sediment = -4.39 (mol/kg), bioconcentration = -7.08 (mol/kg)
Executive summary:

QSAR estimates of toxicity of narcotic chemicals for 19 species of bacteria, algae, fungi, protozoans, colenterates, rotifers, molluscs, crustaceans, insects, fish and amphibians we used to predict the no effect level (NELs) at the ecosystem level by means of recently developed equilibrium extrapolation methods. Equilibrium partitioning theory was used to derive NELs for aquatic sediments and internal toxicant concentrations for aquatic organisms. The report contains a simple table depicting NELs for narcotic chemicals for water, sediment and residues in biota. These can be predicted on the basis of only the octanol/water partition coefficient and the molecular weight of the material of concern. Calculations were carried out for 102 narcotic chemicals.