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Ecotoxicological information

Toxicity to terrestrial plants

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Endpoint:
toxicity to terrestrial plants: short-term
Type of information:
experimental study
Adequacy of study:
key study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: Guideline study with acceptable restrictions
Qualifier:
according to guideline
Guideline:
OECD Guideline 208 (Terrestrial Plants Test: Seedling Emergence and Seedling Growth Test)
Deviations:
no
Principles of method if other than guideline:
Second experiments were carried out in nurtient solutions
GLP compliance:
not specified
Analytical monitoring:
yes
Details on sampling:
analytical monitoring at test start and end of exposure and before renewal of test solution
Vehicle:
no
Details on preparation and application of test substrate:
test substance was dissolved in water
Species:
Lactuca sativa
Plant group:
Dicotyledonae (dicots)
Test type:
early seedling growth toxicity test
Study type:
laboratory study
Substrate type:
other: soilo and solution (and perlite as an unreactive substrate)
Limit test:
no
Remarks:
14 d in soil, 21 in nutrient solution
Test temperature:
21 +/- 4 °C
pH:
7.5
Moisture:
Soil experiment: 25 to 30 % moisture content (80% of the water-holding capacity)
Details on test conditions:
16:8 h light:dark 6500 lx fluorescent tubes
Nominal and measured concentrations:
analytical monitoring at start and end of test
Species:
Lactuca sativa
Duration:
7 d
Dose descriptor:
other: EC50 soil
Effect conc.:
67 mg/kg soil dw
Nominal / measured:
meas. (arithm. mean)
Conc. based on:
test mat.
Basis for effect:
growth
Remarks on result:
other: 95% C.I.: 52-86
Species:
Lactuca sativa
Duration:
14 d
Dose descriptor:
other: EC50 soil
Effect conc.:
> 100 mg/kg soil dw
Nominal / measured:
meas. (arithm. mean)
Conc. based on:
test mat.
Basis for effect:
growth
Species:
Lactuca sativa
Duration:
21 d
Dose descriptor:
other: EC50 nutrient solution
Effect conc.:
23 other: mg/L
Nominal / measured:
meas. (arithm. mean)
Conc. based on:
test mat.
Basis for effect:
growth
Remarks on result:
other: 95% C.I.: (16-31)
For most of the examined phenols (including o-cresol) applied concentrations 
dropped but remained larger than 50 % of the nominal values.
Validity criteria fulfilled:
not specified
Conclusions:
The toxicity of o-cresol to lettuce seedlings (Lactuca sativa) was determined according to OECD Guideline 208 in soil. The EC50 was 67 mg/kg soil d.w. after 7 d, >100 mg/kg soil d.w. after 14 d. The highest effect concentration (EC50 >100 mg/kg) was normalised to an OC content of 3.4% according to TGD (EU 2003), resulting in a corrected EC50 of >242 mg/kg.
Executive summary:

The short-term toxicity of o-cresol to lettuce (Lactuca sativa) was examined by Hulzebos (1993). The test compound was incorporated into soil according to OECD-guideline 208. The organic matter of 2 soil types used was given as 1.4 to 1.8 %. Lettuce seed was sown and the weight of the crops (above-ground biomass) was measured after 7 and 14 days. After an exposure period of 14 days, a nominal EC50 of >100 mg/kg soil (dry weight) was obtained. According to TGD (EU 2003), the effect concentration (EC50 >100 mg/kg) is corrected for a standard soil with a content of organic matter of 3.4 % resulting in a corrected EC50 of >242 mg/kg. The authors stated that “at the end of the test, the concentrations of most phenols in soil had dropped to a low value (<20% of the initial analysed concentrations)”.

Endpoint:
toxicity to terrestrial plants: long-term
Type of information:
other: expert judgement on long-term toxicity
Adequacy of study:
other information
Reliability:
other: expert judgement on long-term toxicity
Justification for type of information:
A long-term toxicity test on plants is not relevant according to column 2 of Annex X of Regulation EC 1907/2006, as the risk assessment does not indicate the need to investigate further the effects of the substance on terrestrial organisms (please refer to the Chemical Safety Report). The risk to soil organisms exposed to the substance is acceptable based on the PNECsoil calculated using the Equilibrium Partitioning Method and does not need to be refined using long-term tests.
Principles of method if other than guideline:
not applicable; expert judgement on long-term toxicity

A long-term toxicity test on plants is not relevant according to column 2 of Annex X of Regulation EC 1907/2006, as the risk assessment does not indicate the need to investigate further the effects of the substance on terrestrial organisms (please refer to the Chemical Safety Report). The risk to soil organisms exposed to the substance is acceptable based on the PNECsoil calculated using the Equilibrium Partitioning Method and does not need to be refined using long-term tests.

Executive summary:

A long-term toxicity test on plants is not relevant according to column 2 of Annex X of Regulation EC 1907/2006, as the risk assessment does not indicate the need to investigate further the effects of the substance on terrestrial organisms (please refer to the Chemical Safety Report). The risk to soil organisms exposed to the substance is acceptable based on the PNECsoil calculated using the Equilibrium Partitioning Method and does not need to be refined using long-term tests.

Description of key information

The toxicity of o-cresol to lettuce seedlings (Lactuca sativa) was determined according to OECD Guideline 208 in soil. The EC50 was  >100 mg/kg soil d.w. after 14 d. The effect concentration was normalised to an OC content of 3.4% , resulting in a corrected EC50 of >242 mg/kg.
However, in case of only one test result is available, the risk assessment should be performed both on this test result and on the basis of the outcome of the aquatic toxicity data. Therefore the equilibrium partitioning method with the PNEC for aquatic organisms is also taken into account for assessment.

Key value for chemical safety assessment

Short-term EC50 or LC50 for terrestrial plants:
242 mg/kg soil dw

Additional information

Several studies of toxicity of o-cresol towards terrestrial plants were found in the literature.

The scope of the terrestrial effects assessment under the adopted REACH regulation is restricted to soil organisms in a narrow sense and does not actually include adverse effects on soil functions that are only indirectly linked to the biota in soils.

Some tests were designed assessing the influence of o-cresol on germination and growth on moist filter paper or agar treated with the substance. As no soil was used in the tests standardisation of soil effect data to given soil parameters is not possible. Further, converting the results to an appropriate dimension is not applicable. Therefore the results should not be used for the hazard assessment.

Using soil, short-term toxicity of o-cresol to lettuce (Lactuca sativa) was examined. The test compound was incorporated into soil according to OECD-guideline 208. The organic matter of 2 soil types used was given as 1.4 to 1.8 %. Lettuce seed was sown and the weight of the crops (above-ground biomass) was measured after 7 and 14 days. After an exposure period of 14 days, a nominal EC50 of >100 mg/kg soil (dry weight) was obtained. According to TGD (EU 2003), the effect concentration (EC50 >100 mg/kg) is corrected for a standard soil with a content of organic matter of 3.4 % resulting in a corrected EC50 of >242 mg/kg. The authors stated that “at the end of the test, the concentrations of most phenols in soil had dropped to a low value (< 20% of the initial analysed concentrations)".