Registration Dossier

Administrative data

Description of key information

Oral (OECD 407), rat: NOAEL (systemic) ≥ 1000 mg/kg bw/day 

Key value for chemical safety assessment

Repeated dose toxicity: inhalation - systemic effects

Endpoint conclusion
Endpoint conclusion:
no study available

Repeated dose toxicity: inhalation - local effects

Endpoint conclusion
Endpoint conclusion:
no study available

Repeated dose toxicity: dermal - systemic effects

Endpoint conclusion
Endpoint conclusion:
no study available

Repeated dose toxicity: dermal - local effects

Endpoint conclusion
Endpoint conclusion:
no study available

Mode of Action Analysis / Human Relevance Framework

Additional information

Repeated dose toxicity: oral administration

Subacute

To characterize repeated dose toxicity of the test substance a GLP-compliant study according to OECD 407 was performed (Allingham, 2014). 10 Wistar rats (Crl:WI (Han)) per group (5 animals/sex in each dose group) received the test substance with a purity of 74.9% (main constituent: 54.3%) at concentrations of 100, 300 and 1000 mg/kg bw/day via gavage. The doses were chosen based on results of a range finding study. The respective control group received aqua ad injectionem. Endpoints included clinical observations, body weight and food consumption measurements in addition to functional observations prior to and after exposure. Further, at the end of the study, haematology, clinical biochemistry, urinalysis and pathology were performed in all animals. Full histopathology was carried out on the control and high-dose animals with extension to the other dose groups for the liver, kidney, stomach and mesenteric lymph nodes.

No mortality occurred in the control or any dose group. All males in the high-dose group showed treatment-related clinical signs including salivation (4 males) and moving of the bedding (3 males). Further, high-dose males exhibited a blue skin which was most probably due to the colour of the test item. In high-dose females, moderate salivation and moving of the bedding was observed in 3 animals. No significant alterations in body weight development were recognized as body weights fell within the normal range of variation. Food consumption remained unaffected and ophthalmoscopic as well as functional examinations including neurobehavioural observations were unremarkable in all dose groups and both sexes.

Haematological parameter did not indicate a toxicologically relevant effect. Clinical biochemistry revealed dose-dependent changes in urea (high-dose males), cholesterol (high-dose males) and alkaline phosphatase (AP, mid- and high-dose females) reaching statistically significance in animals of the high-dose group. Further, glucose levels were significantly decreased in low- and mid-dose females without showing a dose-related effect. Dose-dependent alterations in total bile acids (TBA) and aspartate-aminotransferase (ASAT) did not reveal statistically significance.

A blue discoloration of several organs and tissues like skin, kidney, testes, epididymides, and liver found in both genders of the high-dose animals was observed in gross pathology attributable to the blue colour of the test item. Further, individual males in the low- and mid-dose group exhibited yellow spots on the right epididymides which were assumed to be incidental. Moreover, one high-dose female revealed a little extra tissue below the liver. Further incidental findings were represented by a discoloured dark thymus as well as a discoloured red auxilliary lymph node.

Absolute and relative organ weights were comparable among the groups except slight increases in relative liver weight in high-dose males and females, respectively. High-dose male animals further revealed slight decreases in thymus and prostate weights. Females showed slightly, but non-statistically significant increased weights of ovaries. As all deviations were within the variation of controls, the effects on the above mentioned organ weights are not considered as biologically relevant. Further, a decrease in the thyroid/parathyroid gland weight in mid- and high-dose females was determined reaching statistically significance only as relative organ weights compared to body weight.

Further, roughly dose-related effects in the stomach indicative for local irritations due to test item deposition and substance application were determined in both genders among the test groups starting in the low-dose group. As food consumption and body weight development appeared normal in affected animals, systemic toxicity based on the effects observed in the stomach is excluded. Minor amounts of grey pigment were seen within the corticotubular epithelium of the kidney in the high-dose animals of both sexes and in a single mid-dose female without accompanying effects on the organ. Moreover, interstitial macrophages were present in the testes of high-dose males associated with test item deposition. In the mesenteric lymph node, minimal or mild sinus histiocytosis was observed in 1/5 males of mid- and high-dose groups and in 1/5 low-, 2/5 mid- and 3/5-high-dose females which might be related to test item deposition. Moreover, minimal diffuse bile duct hyperplasia arising in the portal region of the liver was observed in the mid- and high-dose group in a dose-related manner. Neither degenerative nor necrotic changes were observed in the bile ducts nor cholestasis. Based on severity of the abnormality and the fact that ductular proliferation often represents a reparative effect on the bile duct system which is reversible after withdrawal of the agent (Hailey et al., 2014), minimal bile duct hyperplasia is not considered as predictive of potential hepatotoxicity. Moreover, animals of the mid- and high-dose group did not show any evidence of functional impact on the liver which exacerbates the identification of discernible toxic effects. In detail, decreased levels of ALP, glucose, TBA and increased ASAT do not provide sufficient evidence for liver toxicity; especially as liver toxicity is generally associated with elevated TB, ALP and TBA levels. Therefore, alterations observed in clinical parameters are not considered as reliable indicators for functional impact on the liver. Taking further into account that minimal bile duct hyperplasia is considered as non-adverse in rats with little to no concern to humans (Hailey et al., 2014), minimal bile duct hyperplasia induced by the test substance is considered non-adverse, especially as 1) the bile duct hyperplasia was observed with low severity without associated findings, 2) bile duct hyperplasia is known to occur in rats as a common spontaneous change which does not functionally impact the liver, 3) minimal ductular proliferation is often reparative, not carcinogenic and reversible (Hailey et al., 2014). Thus, in conclusion, a NOAEL 1000 mg/kg bw/day was defined for systemic toxicity in rats in the conducted study after sub-acute exposure to the test substance.

 

 

 

 


Justification for selection of repeated dose toxicity inhalation - systemic effects endpoint:
Study not required according to Annex VIII of Regulation (EC) No. 1907/2006.

Justification for selection of repeated dose toxicity inhalation - local effects endpoint:
Study not required according to Annex VIII of Regulation (EC) No. 1907/2006.

Justification for selection of repeated dose toxicity dermal - systemic effects endpoint:
Study not required according to Annex VIII of Regulation (EC) No. 1907/2006.

Justification for selection of repeated dose toxicity dermal - local effects endpoint:
Study not required according to Annex VIII of Regulation (EC) No. 1907/2006.

Justification for classification or non-classification

The available data on repeated dose toxicity of the test substance do not meet the criteria for classification according to Regulation (EC) 1272/2008 or Directive 67/548/EEC, and are therefore conclusive but not sufficient for classification.