Alcohols, C9-11-branched

Endpoint summary

Key value for chemical safety assessment

Effects on fertility

Description of key information

Limited information available (results from OECD 422; repro screening study used as dose range finding study).

Additional information

The results of the extended one generation study is still under investigation for further assessment. We've received a draft study report and we will be submit an updated registration when the final report is available for the extended one generation study (anticpated August 2023). Materials /methods and control information are shown in the robust study summary. 

Effects on developmental toxicity

Description of key information

Low potential for developmental toxicity.

Effect on developmental toxicity: via oral route

Dose descriptor:

NOAEL

1 000 mg/kg bw/day

Additional information

In the subchronic studies of isononanol, isodecanol, no changes in testicular weight were observed.  These data support the conclusion that members of the Oxo Alcohols C9 to C13 category are not selective reproductive toxicants. 

Isooctanol (Exxal 8) was administered by gavage to three groups of Crl:CDBR female rats at doses of 100, 500, and 1000 mg/kg. A fourth group (Group 1) served as a control and received the carrier (corn oil) only. Mated females were dosed once daily from Gestation Day (GD) 6 through GD 15. Dosing volumes were 5 ml/kg for all groups and based on the animals' most recent body weight.

 

Males and females were paired and housed overnight until confirmation of mating (sperm/plug = GD 0). Each mated female then was returned to its own cage and new females were placed in the males' cages until the required number of mated females was obtained. Mated females were assigned to dose groups in the order of mating.

 

Clinical observations were made daily during gestation. The animals were examined for viability at least twice daily during the treatment period and at least once daily at other times during the study. Body weight and food consumption measurements were made on GD 0, 6, 9, 12, 15, 18, and 21. On GD 21, animals were euthanized and cesarean sections were performed. Gross necropsies were performed, uterine weights with ovaries attached measured, uterine contents examined, and the required uterine implantation data recorded. All live fetuses were weighed, sexed externally, and examined externally for gross malformations. 

 

Approximately one-half of the fetuses of each litter were decapitated after being euthanized. The heads were preserved in Bouin's solution for at least two weeks, rinsed, and subsequently stored in 70% alcohol. Sections of the fetal heads were prepared with a razor blade, examined for the presence of abnormalities, and then discarded. The viscera of these fetuses were immediately examined for abnormalities by dissection. The remaining live fetuses were eviscerated, processed for skeletal staining, and examined for the presence of malformations and ossification variations.

 

Unscheduled mortality was limited to one high dose female which was euthanized in a moribund condition on GD 9. This animal was observed with extreme abdominal staining just prior to death. There were no significant findings at postmortem examination and therefore, the cause of morbidity could not be established. 

 

Adverse clinical signs were observed primarily in the high dose dams following dose initiation. Approximately eight of the twenty-four surviving dams were observed with a least one of the ensuing signs: emaciation, little sign of food consumption, abdominal/anogenital staining, rales, hypoactivity, no stool, and/or little sign of stool. These signs were transient, occurring for only one day in some animals, and were generally not observed in the animals following the cessation of dosing. The remaining dams in the group were free of observable abnormalities throughout the study, or had incidental findings such as alopecia. The majority of dams in the control, low and mid dose groups were free of observable abnormalities during the entire gestation period. 

 

Statistically significant body weight gain suppression was observed in the high dose females at the GD 6-9 body weight change interval and during the overall treatment period (GD 6-15) when compared with controls. Statistically significant decreases in mean food consumption were observed in the high dose females during the GD 6-9 interval and during the treatment period (GD 6-15) when compared with controls. However, these changes were transient and corrected mean body weight and mean food consumption of all treated group females were essentially equivalent for the overall gestation period (GD 0-21). 

 

There were no maternal findings found postmortem which were judged to be the result of treatment with EXXAL 8N. The majority of uterine implantation parameters were essentially equivalent between treated and control groups. There was an increase in post-implantation loss in the high dose females (17.3%) compared with controls (4.8%), although this difference was not statistically significant. Three dams in the high dose group did not have any viable fetuses at cesarean section, and only had implantation sites or early resorptions. The resorption of these fetuses was considered the result of the poor health of the dams rather than a direct developmental effect.

 

There were no statistically significant differences in mean fetal body weight between treated and control fetuses of either sex. Three low dose, two mid dose, and one high dose fetus were stunted. There were no statistically significant increases in total or individual external, visceral, or skeletal malformations, or external and visceral variations in the treated groups when compared with controls. Additionally, there were no statistically significant differences in the mean skeletal ossification sites between treated and control fetuses. 

 

There were statistically significant increases in total fetuses with skeletal variations and in the incidence of hypoplastic skull bones in the high dose group when compared with controls. However, the incidences of these findings were only slightly higher than the historical control range of this laboratory. Additionally, since the litter is the preferred unit of measure in developmental toxicology, the absence of a statistically significant increase in the litter-based incidence provides additional evidence the observed increase in this parameter was not biologically meaningful.

 

Statistically significant increases in rudimentary and well formed lumbar ribs were observed in the high and/or mid dose groups compared with controls on a per fetus and/or litter basis. On a per litter basis the increase in rudimentary lumbar ribs was statistically significant in the mid dose group when compared with controls. Although these increased incidences were not within the historical range of this laboratory, variations in skeletal structure such as rudimentary ribs are so common, they are regarded as alternative normal patterns and not regarded as harmful developmental toxic effects. Furthermore, rudimentary or well formed ribs are not considered biologically significant in the absence of other conventional signs of embryotoxicity, i.e. malformations, embryolethality, or fetal weight reduction. Rib variations have often been associated with maternal toxicity or stress. Therefore, the developmental significance of rib variations in the high dose fetuses probably relates to the transient maternal toxicity observed in the high dose females during the treatment phase of this study. Thus, this variation was not considered to be an adverse effect on the fetuses.  

 

In conclusion, signs of toxicity were apparent in the maternal animals at a dose level of 1000 mg/kg, as indicated by adverse clinical signs, reductions in body weight gain and food consumption. However, the findings were generally transient. There also was an increase in post-implantation loss in the high dose females, as three dams did not have any viable fetuses at cesarean section, only implantation sites/early resorptions. The resorption of these fetuses was considered the result of the poor health of the dams rather than a direct developmental effect. There were several statistically significant increases in the incidence of fetal skeletal variations both on an individual and litter basis in the treated groups compared with controls. However, most of these incidences were only slightly higher than the historical control range of this laboratory, or regarded as alternative normal patterns, and not regarded as harmful developmental toxic effects (Harris and DeSesso, 1994). Therefore, these common findings in fetal rats were not considered biologically important. Accordingly, the maternal NOAEL (No Observable Adverse Effect Level) was established at 500 mg/kg. The developmental NOAEL was established as 1000 mg/kg under the conditions of this study.

The key study, an OECD 414 test guideline Prenatal and Developmental Toxicity Study (rat) was performed using the test substance at 100, 500, or 1000mg/kg/d. The objectives of this study were to detect adverse effects of the test substance on pregnant Sprague-Dawley rats and development of the embryo and fetus consequent to exposure of the female from implantation to closure of the hard palate. Pregnant females were administered doses of 0 (vehicle control), 100, 500, or 1000 mg/kg/day by oral gavage once daily from Gestation Day (GD) 6 through 20 (25 rats/group). The females were sacrificed on GD 21 and the following parameters and endpoints were evaluated: viability, maternal clinical signs, maternal body weight and body weight gain, maternal food consumption, maternal thyroid hormone evaluation, gross necropsy findings, maternal thyroid weight and histopathology, ovarian and uterine examination, fetal sex ratio, fetal body weight, fetal anogenital distance, and fetal abnormalities (external, visceral, and skeletal).

Based on test substance-related maternal toxicity in the form of morbidity, mean body weight losses, lower mean body weight gains, and lower mean food consumption at 1000 mg/kg/day, a dose level of 500 mg/kg/day was considered to be the no-observed-adverse-effect level (NOAEL) for maternal toxicity when the test substance (Isoundecanol) was administered orally by gavage to time-mated Crl:CD(SD) rats.

Based on lower mean fetal body weights at 1000 mg/kg/day, a dose level of 500 mg/kg/day was considered to be the NOAEL for developmental toxicity. However, the significantly lower mean fetal body weights at 1000mg/kg/d were observed in the presence of maternal toxicity in the form of decreased food consumption, lower mean body weight gains, and mean body weight losses. The plausibly-linked undernutrition of the dams as a result of decreased food consumption were correlated with the observed fetal body weight decreases. Maternal body weight changes are likely also due to liver hypertrophy in the dams, as a dose-dependent, statistically significant increase in liver weight was observed in this study, and correlates with observations at this dose in the 90 -day study on the test substance (in males and females, liver weights were significantly increased with a concurrent observation of hepatocellular hypertrophy; Charles River Laboratories, Study ID 00438038, 2020), and resultant significant liver enzyme induction (see Toxicokinetics section of this dossier for quantification; microsomal enzyme induction study on liver samples from the 90 -day study). These are adaptive changes in liver in response to the high oral doses observed in non-pregnant females and adult males (in the 90 -day study) as well as increased liver weights in dams in this study. It is plausible that this, in turn, is affecting food consumption and liver metabolism such that it compromises systemic nutrition of the rat fetuses. Thus, the decreased fetal weights at high doses are due to a non-specific secondary mechanism (maternal stress and the disruption of homeostasis), which describes the maternal toxicity observed (Regulation (EC) No 1272/2008 of the European Parliament and of the Council on classification, labelling and packaging of substances and mixtures, updated 6.07.2019). Supporting this conclusion is the lack of malformations observed in fetuses at any dose, including 1000mg/kg/d. Additionally, it should be noted that maternal effects observed were not due to a mean effect, nor were the decreased fetal weights. Individual dams with lower terminal body weight at 1000mg/kg/d correlated with lower litter weights.

 

Justification for classification or non-classification

No classification for reproductive or developmental toxicity is indicated according to the general classification and labeling requirements for dangerous substances and preparations (Directive 67-548-EEC) or the classification, labeling and packaging (CLP) regulation (EC) No 1272/2008.