Bis(1,2,2,6,6-pentamethyl-4-piperidyl) [[3,5-bis(1,1-dimethylethyl)-4-hydroxyphenyl]methyl]butylmalonate

Endpoint summary

Description of key information

The substance causes granulomatous inflammation in intestine, spleen and liver upon subacute oral exposure to low doses (Ciba-Geigy 1979, BASF 2012a and b). A NOAEL of 2 mg/kg bw for subacute oral dosing was identified (BASF 2012b) and the mesenteric lymph nodes were found to be the most sensitive organ.

Key value for chemical safety assessment

Repeated dose toxicity: via oral route - systemic effects

Endpoint conclusion

Endpoint conclusion:

adverse effect observed

Dose descriptor:

NOAEL

2 mg/kg bw/day

Study duration:

subacute

Species:

rat

Quality of whole database:

Valid without restriction

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

Additional information

Repeated dose toxicity upon oral exposure was evaluated by a weight-of-evidence approach because existing studies failed to identify a NOAEL, but showed a very distinctive pattern of toxicity involving accumulation of macrophages in the intestinal mucosa, activated macrophages in mesenteric lymph nodes, spleen and liver together with changes in organ weights and white blood cells. These parameters were further evaluated in a 28 -day dose-range finder study for testing of reproductive toxicity (BASF 2012a) and then again as additional investigations in the GLP-compliant reproductive toxicity screening study (BASF 2012b).

In summary, the test item specifically affects macrophages in exposed organs (small intestine, liver, spleen). At doses of 0.5 and 2 mg/kg bw, no adverse effects were observed . At doses of 5 mg/kg bw and higher, adverse effects were observed. Foamy macrophages couldbe seen in mesenteric lymph nodes, liver and spleen giving the clinical picture of granulomatous inflammation. This is accompanied by increases in white blood cells which is consitent with inflammation. Mortality was observed at subacute doses of 50 mg/kg bw and above. The onset of mortality shortens with increasing doses. A contribution of bacterial infection via damage of the gastrointestinal mucosa is ruled out based on the histopatholgy findings.

At 10 mg/kg bw, findings were the following: Body weight loss in 4 male animals during towards the end of the administration period, poor general condition in 2 male animals towards the end of the administration period, swelling of limbs and unsteady gait in 2 male animals towards the end of the administration period and piloerection in 1 male animal towards the end of the administration period. Haematology changes involved a d

ecreased hemoglobin and hematocrit values in both sexes, decreased red blood cell (RBC) counts in females, decreased mean corpuscular volume (MCV) and mean corpuscular hemoglobin content (MCH) in males increased platelet counts in females increased total white blood cell (WBC) counts, absolute and relative neutrophil, absolute monocyte and absolute large unstained (LUC) counts in both sexes, decreased relative lymphocyte counts in both sexes, m

inimal to moderate necrosis of the liver in 5 of 10 male animals. Histopathology findings were granulomatous inflammation with necrosis of the mesenteric lymph node in 9 of 10 male (graded marked to massive) and 9 of 10 female (graded moderate to marked) animals and granulomatous inflammation with necrosis of the spleen in 2 of 10 male (graded moderate to marked) and 2 of 10 female (graded slight to moderate) animals

Effects were observed in gavage studies (Ciba-Geigy 1979b, BASF 2012a and b) and also in a draft report of a subacute feeding study (BASF 1976) as well is in a fourteen-day non-guideline immunotoxicity study with mice (BASF 1986). The study in mice was set up as a dermal study, however no precaution was taken against preening and this was indeed reported to have occurred. Therefore, significant oral exposure has to be assumed. In this study, 70 mg/kg bw caused spleen weight increase and thymus weight decrease, but no effects on body weight or clincial signs. The substance was described to exhibit an adjuvant-type activity; details are described in the section of specific investigations. At 7 mg/kg bw, one parameter was affected and 0.7 mg/kg bw was identified as NOEL. Considering the shorter duration, the different species, and the significant oral exposure, the results and the effective dose levels are consistent with the experimental data obtained with rats and the NOAEL of 2 mg/kg bw for subacute exposure is used for the risk asssessment.

For inhalation, no information on subacute toxicity is available. Considering the physico-chemical properties, systemic availability upon inhalation needs to be assumed.

Justification for selection of repeated dose toxicity via oral route - systemic effects endpoint:
In this study, the NOAEL was identified. GLP compliant. All relevant parameters investigated.

Repeated dose toxicity: via oral route - systemic effects (target organ) cardiovascular / hematological: lymph nodes

Justification for classification or non-classification

Dangerous Substance Directive (67/548/EEC)

The available studies are considered in sum reliable and suitable for classification purposes under 67/548/EEC. Mortility occurred at doses of less than 150 mg/kg bw upon subacute exposure. Findings at doses of less than 15 mg/kg bw are adverse and relevant for classification and labelling (eg necroses at 10 mg/kg bw). As a result the substance is considered to be classified as toxic (T; R25) 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. As a result the substance is considered to be classified in Category 1 (H372) for repeated dose toxicity under Regulation (EC) No. 1272/2008, as amended for the second time in Directive (EC 286/2011). The lymph nodes were identified as the most sensitive target organ for repeated exposure.