6,6'-di-tert-butyl-2,2'-methylenedi-p-cresol

Ecotoxicological Summary

Hazard for aquatic organisms

Freshwater

Hazard assessment conclusion:

no hazard identified

Marine water

Hazard assessment conclusion:

no hazard identified

STP

Hazard assessment conclusion:

no hazard identified

Sediment (freshwater)

Hazard assessment conclusion:

no hazard identified

Sediment (marine water)

Hazard assessment conclusion:

no hazard identified

Hazard for air

Air

Hazard assessment conclusion:

no hazard identified

Hazard for terrestrial organisms

Soil

Hazard assessment conclusion:

no hazard identified

Hazard for predators

Secondary poisoning

Hazard assessment conclusion:

PNEC oral

PNEC value:

10 mg/kg food

Additional information

The substance is not legally classified as dangerous for the environment and so neither included in Annex I of Directive 67/548/EEC nor in Regulation 1272/2008 (CLP), including its 2nd and 3th ATP.

A scientific assessment is performed in order to decide whether the classification criteria covering effects on the aquatic environment shall be assigned for 6,6’-di-tert-butyl-2,2’-methylenedi-p-cresol.

As outlined in Annex VI of Directive 67/548/EEC, Chapter 5 and Annex I of the Regulation 1272/2008, Chapter 4, the available data on aquatic toxicity for the substance are evaluated for hazardous effects with regard to the substance properties, in particular the water solubility.

As a conclusion, a hazardous potential of the substance can be ruled out and hence no classification according to and the Dangerous Substance Directive 67/548/EEC (DSD) or Classification. Labelling and Packaging Regulation EC 1272/2008 (CLP) is required. The following aspects have been taken into account:

1. Consideration for difficult substance:

With an experimentally determined water solubility of 0.007 mg/l 6,6’-di-tert-butyl-2,2’-methylenedi-p-cresol is only poorly soluble in water. Therefore it can be considered as a difficult substance for environmental hazard assessment regarding REACH guidance R.7b.

2. Media preparation method

Due to the low water solubility of the substance (0.007 mg/l), a dispersant-solubilizer system (DMF/Castor oil HCO-40, 3/1 (w/w)) was used in all toxicity tests and stability of the test substance was monitored using GC-MS. A homogenous solution could be attained only at (and less than) the nominal concentration of 5.0 mg/l with the maximum allowable dispersant concentration of 100 mg/l. No precipitations or emulsions were observed at this nominal concentration.

The analytical results show stability of the test substance during each experiment and a recovery rate greater than 80 % of the nominal test concentrations. Thus it is shown that the dispersant-solubilizer system significantly increases the solubility of 6,6’-di-tert-butyl-2,2’-methylenedi-p-cresol in water. All measured test concentrations used in the aquatic toxicity tests were far exceeding the water solubility of the substance, representing unrealistic environmental conditions. Consequently, the effects observed in the aquatic toxicity tests are also at levels higher than the water solubility.

3. Interpretation of ecotoxicity test results

In the following table, the most relevant data used for classification purposes are presented:

Table: Data on aquatic toxicity, degradation and bioaccumulation of 6,6'-di-tert-butyl-2,2'-methylenedi-p-cresol

Organism	Test duration	Result (mg/l)	Reference
Aquatic plants Green algae (Selenastrum capricornutum)	72h	ErC50 > 5.0 NOEC = 1.3	EA Japan (1999)
Invertebrates Water flea (Daphnia magna)	48h 21d	EC50 > 4.8 NOEC = 0.34 LOEC = 0.89 Reproduction	EA Japan (1999) EA Japan (1999)
Fish Medaka (Oryzias latipes) Cyprinus carpio	96 h60 d bioconcentration study	LC50 > 5.0 suggested NOEC > 1.0	EA Japan (1999)EA Japan (2003)

Based on the characteristic as difficult substance and the use of dispersant-solubilizer in media preparation, the test results for 6,6’-di-tert-butyl-2,2’-methylenedi-p-cresol shall be assessed with care.

As no effects are observed up to the limit of the water solubility, the substance is considered to be not toxic (acute and chronic) for aquatic organisms.

Conclusion on the environmental hazard assessment and on classification and labelling

Based on substance properties (not readily biodegradable, BCF > 100 / 500) the substance might be classified as R53 “May cause long-term adverse effects in the aquatic environment” according to Directive 67/548/EEC and Chronic Cat 4 (H412“May cause long lasting harmful effects to aquatic life) according to Regulation 1272/2008.

Table: Data degradation and bioaccumulation of 6,6'-di-tert-butyl-2,2'-methylenedi-p-cresol

Test	Test duration	Result (mg/L)	Reference
Ready biodegradability	28d	0%	EA Japan 1992
Bioconcentration BCF	60d	840	EA Japan 2003

The “safety net criteria” apply to substances unless there exists additional scientific evidence concerning degradation and/or toxicity sufficient to provide an adequate assurance that neither the substance nor its degradation products will constitute a potential long-term and/or delayed danger to the aquatic environment.

Additional scientific evidence is provided by a Daphnia magna reproduction study performed under semi static conditions. The study was conducted in accordance with the OECD Test guideline 211. No toxic effects on reproduction and mortality against Daphnia were observed up to the limit of the water solubility. This result clearly indicates the absence of any chronic toxicity effects at the solubility limit, as the no-observed effect concentration is greater than the solubility limit determined in this study.

Conclusion on classification

In conclusion, a hazardous potential of the substance can be ruled out and hence no classification according to DSD (Directive 67/548/EEC) or CLP (Regulation EC 1272/2008) is required.