coconut oil, reaction products with glycerol esters of 3,5-bis(1,1-dimethylethyl)-4-hydroxybenzenepropanoic acid

Endpoint summary

Description of key information

90-days-study, oral (OECD Guideline Study 408, Notox 487736, 2008): NOAEL (male/female) = 14 mg/kg bw 
28-days-study, oral (OECD Guideline Study 407, RCC 636456, 1997): NOAEL (male/female) = 50 mg/kg bw 

Key value for chemical safety assessment

Repeated dose toxicity: via oral route - systemic effects

Endpoint conclusion

Dose descriptor:

NOAEL

14 mg/kg bw/day

Study duration:

subchronic

Species:

rat

Additional information

Oral:A 28- and a 90 -days repeated dose toxicity study, both investigating the test substance after oral administration, are available.

In the subacute toxicity study (RCC 636456, 1997), which was performed according to OECD guideline 407, the test substance was administered by gavage to 5 male and 5 female Wistar rats at doses of 50, 100, and 200 mg/kg bw. 5 additional animals were allocated to the control group and the 200 mg/kg bw dose group to investigate post-exposure recovery.

All animals of this study survived, except one female animal of the 50 mg/kg bw dose group. During the treatment period, body weight of the males in the 200 mg/kg bw dose group was slightly lower when compared with the controls. No effects were observed concerning haematology, clinical chemistry, urinalysis and gross pathology. Investigation of the organ body weights revealed a dose-related increase in liver weights of the male and female animals in the 100 and 200 mg/kg bw dose groups. Higher thyroid weights were recorded in male and female animals at 200 mg/kg at the end of the treatment group and in males at this dose after the recovery period. Hence, the NOEL for the test substance is defined as 50 mg/kg bw for rats of either sex and the NOAEL, resp. LOEL, is 200 mg/kg bw.

In a subchronic toxicity study (Notox 487736, 2008), which was performed according to OECD guideline 408, the test substance was administered by gavage to male (12/group) and female (10/group) Wistar rats at doses of 14, 56, and 222 mg/kg bw.

There were no clinical signs of toxicity noted during the observation period, except salivation and incidental findings (e.g. alopecia, wounds, broken tails) and no changes of the body weights were observed when compared to the animals of the control group. The number of testicular and epididymidal sperm cells and the percentage of normal sperm cells was similar for the 222 mg/kg bw dose group and control group. In the testes sections, no variation was present in the staging of spermatogenesis between the 222 mg/kg bw treated and the control group. Additional investigation for sperm parameters were included, but since no historical control data for this type of study was available and only 3 studies with a similar design could be used, the data is of no value.

Concerning haematology, slightly reduced values for prothrombin time were noted for males and females treated at 56 and 222 mg/kg bw. At 222 mg/kg, slight increased values for total protein, albumin and total bilirubin were observed for males and females. Additionally at this dose, females showed a decreased glucose level. At 222 and 56 mg/kg bw hepatic changes (enlarged and discolorated livers) in males and females were observed and at histopathology, treatment related changes in the liver became obvious as periacinar hepatocytic hypertrophy. Follicular epithelial hypertrophy in the thyroid was noted in males and females treated at 56 and 222 mg/kg bw. Additionally, thyroid follicular adenoma was noted for one male of the 222 mg/kg bw dose group.

Hence, a NOAEL for the test substance is defined as 14 mg/kg bw for rats of both sexes.

The species-specific mechanisms causing the thyroidal stimulation following uptake of 2,6-substituted phenols (and similar compounds) in rats have been described in standard textbooks and are generally acknowledged by the scientific community (Davies, D. T. (1996). Thyroid Endocrinoloy. Animal Clinical Chemistry: A primer for Toxicologists. Ed: A. O. Evans, and Francis,). From basic research performed over several years, it became clear, that the stimulation of glycuronidyl-transferase synthesis is used to facilitate excretion of 2,6-substituted phenolic antioxidants. However, glycuronidyl-transferase is also able to promote the excretion of thyroid hormones. This has remarkable consequences for the physiology of the rat upon exposure to phenolic antioxidants:

- In the rat, the thyroid hormones T₃ and T₄are not bound to a specific carrier protein in the plasma. Therefore, increased levels of glycuronidyl-transferase (induced e. g. by 2,6-substituted phenolic antioxidants) speed up the elimination of T₃and T₄. This causes a drop of the plasma concentrations of T₃and T₄. By feedback mechanism, reduced levels of T₃and T₄hormone subsequently lead to a stimulation of the thyroid to produce new hormone. The chronic stimulation of the thyroid can cause hyperplasia and can lead in extreme cases to thyroid tumours.

 -In primates, about 90% of the thyroid hormones T₃and T₄are bound to a specific protein (thyroxine binding protein) in the plasma. Due to this protein, primates are protected from significant changes of thyroid hormone levels in the plasma, even in the presence of high levels of glycuronidyl-transferase. Consequently, in primates thyroid hormone concen­trations are not affected, no feedback mechanisms are induced to produce new T₃and T₄and no thyroid hyperplasia occurs.

 The active, bioavailable substructure of this substance is closely related to 2’,6’-di-tertiary butylmethylphenole (=butylated hydroxytoluene, BHT). BHT is a direct food additive used world-wide since decades and causes - similar to this substance - a stimulation of the thyroid in rodents. BHT is known to be safe for humans due to the long-lasting experience and due to the well investigated mechanisms of toxicity (see above).

Dermal: No data available

Inhalation: No data available. The substance is a viscous liquid of low vapour pressure. Inhalation to vapour is not relevant.

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Repeated dose toxicity: via oral route - systemic effects (target organ) digestive: liver

Justification for classification or non-classification

Dangerous Substance Directive (67/548/EEC)

The available studies are considered reliable and suitable for classification purposes under 67/548/EEC. No serious irreversible effects were observed at dose levels of less than 150 mg/kg bw upon subacute exposure or 50 mg/kg bw for subchronic exposure. Rat-specific effects on thyroid are not relevant for classification and labelling. As a result the substance is not considered to be classified for repeated dose toxicity under Directive 67/548/EEC, as amended for the 28th time in Directive 2001/59/EC.

Classification, Labelling, and Packaging Regulation (EC) No. 1272/2008

The available experimental test data are reliable and suitable for classification purposes under Regulation 1272/2008. There were significant toxic effects at doses of less than 300 mg/kg bw upon subacute oral exposure in rats and less than 100 mg/kg bw for subchronic exposure. Effects on liver at 56 and 222 mg/kg bw were of an adaptive nature and did not result in significant changes in clinical chemistry. Effects on thyroid are rat-specific and do not need to be taken into account for classification and labelling. As a result the substance is not considered to be classified for repeated dose toxicity under Regulation (EC) No. 1272/2008, as amended for the second time in Directive (EC 286/2011).