3,7-dimethyloctan-3-ol

Endpoint summary

Key value for chemical safety assessment

Effects on fertility

Description of key information

Key study EOGRTS acc. to OECD TG 443 and GLP (BASF 2022; 91R0267/10S213)

NOAEL for general, systemic toxicity (F0) = 4000 ppm (F0 278 mg/kg bw/d in males and 345 mg/kg bw/d overall mean in females)

NOAEL for general, systemic toxicity (adult F1) = 4000 ppm (338 -347 mg/kg bw/d in males and 361 - 362 mg/kg bw/d in females).

NOAEL for fertility and reproductive performance = 12500 ppm (887 mg/kg bw/d in males and 1053 mg/kg bw/d overall mean in females).

NOAEL for developmental toxicity = 4000 ppm (about 431 mg/kg bw/d during lactation)

 

Additional information

In the key study for the endpoint fertility/reproductive toxicity acc. to OECD TG 443 and GLP (BASF 2022; 91R0267/10S213), Tetrahydrolinalool was administered to groups of 25 healthy young Wistar rats/sex as a homogeneous addition to the food in different concentrations (0, 1200, 4000 and 12500 ppm). F0 animals were treated at least for 10 weeks prior to mating to produce a litter (F1 generation). Mating pairs were from the same dose group. Pups of the F1 litter were selected (F1 rearing animals) and assigned to 2 different cohorts (1A and 1B) which were subjected to specific postweaning examinations. Test diets containing Tetrahydrolinalool were offered continuously throughout the study.

The parents' and the pups' state of health was checked each day, and parental animals were examined for their mating and reproductive performances. Food consumption and body weights of the F0 parents and F1 rearing animals was determined regularly and a detailed clinical observation (DCO) was performed in all F0 parents and F1 animals in cohorts 1A and 1B at weekly intervals. Estrous cycle data were evaluated for F0 females over a three-week period prior to mating until evidence of mating occurred. In all cohort 1A females, vaginal smears were collected after vaginal opening until the first cornified smear (estrous) was recorded. The estrous cycle also was evaluated in cohort 1A and 1B females for 2 weeks around PND 75. Moreover, the estrous stage of each female was determined on the day of scheduled sacrifice.

The F1 pups were sexed on the day of birth (PND 0) and were weighed on the first day after birth (PND 1) as well as on PND 4, 7, 14 and 21. Their viability was recorded. At necropsy, all pups were examined macroscopically. Anogenital distance measurements were conducted on all live male and female pups on PND 1. All surviving pups were examined for the presence or absence of nipple/areola anlagen on PND 13 and were re-examined on PND 20.  Date of sexual maturation, i.e. day of vaginal opening (females) or balanopreputial separation (males), of all F1 pups selected to become F1 rearing animals was recorded.

Urine and blood samples for clinical pathological investigations were withdrawn from 10 selected F0 and cohort 1A animals per sex and group. Further blood samples were taken from all surplus (culled) PND 4 pups per sex and group as well as from 10 surplus PND 22 pups per sex and group.

Various sperm parameters (motility, sperm head count, morphology) were assessed in the F0 generation males and cohort 1A males at scheduled sacrifice or after appropriate staining. All F0 parental animals were assessed by gross pathology (including weight determinations of several organs) and subjected to an extensive histopathological examination; special attention being paid to the organs of the reproductive system. A quantitative assessment of primordial and growing follicles in the ovaries was performed for all control and high-dose F1 rearing females of cohort 1A. All F1 rearing animals were assessed by different pathological and histopathological examinations as well.

Stability, correct concentrations and homogeneous distribution of Tetrahydrolinalool in the diet were all confirmed through analytics.

The overall mean dose of Tetrahydrolinalool was approx. 84 mg/kg bw/d in the 1200 ppm group, approx. 278 mg/kg bw/d in the 4000 ppm group and approx. 887 mg/kg bw/d in the 12500 ppm group for the F0 male animals.

Throughout all study phases of F0 female animals the overall mean dose was approx. 104 mg/kg bw/d in the 1200 ppm group, approx. 345 mg/kg bw/d in the 4000 ppm group and approx. 1053 mg/kg bw/d in the 12500 ppm group.

In cohort 1A the overall mean dose mean dose of Tetrahydrolinalool was approx. 102 mg/kg bw/d in the 1200 ppm group, approx. 338 mg/kg bw/d in the 4000 ppm group and approx. 1073 mg/kg bw/d in the 12500 ppm group for the male animals and approx. 107 mg/kg bw/d in the 1200 ppm group, approx. 362 mg/kg bw/d in the 4000 ppm group and approx. 1108 mg/kg bw/d in the 12500 ppm group for the female animals.

In cohort 1B the overall mean dose mean dose of Tetrahydrolinalool was approx. 102 mg/kg bw/d in the 1200 ppm group, approx. 347 mg/kg bw/d in the 4000 ppm group and approx. 1122 mg/kg bw/d in the 12500 ppm group for the male animals and approx. 108 mg/kg bw/d in the 1200 ppm group, approx. 361 mg/kg bw/d in the 4000 ppm group and approx. 1148 mg/kg bw/d in the 12500 ppm group for the female animals.

There were no test substance-related mortalities or adverse clinical observations noted in any of the groups. In particular, regularly conducted detailed clinical observations revealed no effects. Food consumption was comparable among males and females of the F0 generation. In high dose males mean body weight was slightly decreased (from study day 56 to 70 as well as from study day 91 to 105 with a maximum by -6.6 % on study day 105). Mean body weights of females were comparable across all groups during pre-pairing, gestation and lactation. 

Estrous cyclicity was comparable in all groups and was not affected by the test compound. Likewise, male and female fertility and reproductive performance was not affected by administration of Tetrahydrolinalool. There was no effect on the number of implantation sites, number of live and stillborn pups, sex ratio, clinical observations in pups or pre- and postnatal survival. Mean pup weights were slightly decreased in the high dose group predominantly during the second half of the lactation period (during PND 4 – 7, PND 14 – 21 and PND 1 - 21 in male and female pups as well as both sexes combined down to -17 % vs. ctrl., respectively). There were no effects on anogenital distance or nipple retention in male pups. No abnormalities were observed at necropsy of the F1 pups.

The time of vaginal opening and preputial separation was later in the high dose group F1 animals, but this was attributable to the decreased body weight development in this group, since sexual maturation commenced even at comparable or even slightly lower body weights when compared to the controls.

In the F1A generation, food consumption was slightly lower in high dose males (during study days 14, 28 and 56) as well as in females (on study day 42 only). Body weights were slightly lower through the whole study in males and to a lower extend also in females, particularly in the cohort 1B. In cohort 1A, body weights were decreased in males during the entire study (down to -9% vs. control, respectively) and in females on study day 0 (-8%) and 7(-6%). Further, body weight changes were decreased in males from study day 35 to 42 and from study day 0 to 56. In cohort 1B, body weights were decreased in males from study day 7 onwards (down to -9% vs. ctrl) and in females on study days 7, 35 and 42 (down to -6% vs ctrl.). Body weight changes were decreased in in male animals of this cohort during study days 0-7, 7-14 and 0-49 (down to -11% vs ctrl.) as well as in female animals during study day 21-28 (-16% vs. ctrl.) There were no effects on estrous cyclicity in the F1 females.

Regarding clinical pathology, F0 and F1 males of the high dose groups showed an α2u globulinuria with increased transitional epithelial cells, cellular and granular casts present in the urine. This species-specific alteration is of no relevance for humans (Hard et al., 2018). Further, high dose F0 males and F1 females showed changes in glucose and urea levels which could indicate an alteration of liver cell metabolism, especially in the context of decreased total bilirubin values indicating a liver enzyme induction. In high dose F1 males, increased urea and creatinine levels together with the increased amount of blood (erythrocytes) in the urine might be indicative of an impaired renal function or of renal damage, although no corresponding histologic lesions were observed in the kidneys. Therefore, the cause of the clinical pathology findings cannot be elucidated.

Regarding pathology, target organ was the kidney in F0 and F1 male animals.

 

F0 generation parental animals

Concerning the eosinophilic droplets in the kidneys of male animals, a dose-dependent increase in number of affected animals and severity was observed in the treated test groups compared to controls. Further, granular casts were present to a minimal to slight degree in high dose males. Immunohistochemistry revealed a similar staining pattern to that described by Cesta et al 2013. Taken together, the presence of alpha2u-globulin (nephropathy) is likely. As casts indicating previous tubular injury were only present in the high dose group, the changes were considered treatment-related and adverse in this test group, but not adverse in low and mid dose groups. However, the findings are not relevant for humans due to the species specifity of alpha2u-globulin.

The increased mean absolute and relative liver weight in high dose males might be caused by an enzyme induction, also indicated by the clinical pathology results. This change was considered possibly treatment-related, but not adverse.

Except for one mid dose female, which presented with a bilateral ovarian atrophy, the reproductive organs of the mating pairs suspected of reduced fertility did not show histopathological findings that could explain the reduced fertility.

 

F1 generation, rearing animals, cohort 1A

The increased mean relative weight of the kidney in males of all test substance treatment groups might be linked to the increased protein-storage in the kidney. Concerning the eosinophilic droplets in the kidneys of male animals, a dose-dependent increase in severity was observed in the test groups compared to controls. Further, granular casts were present to a minimal to slight degree in test substance treated males. Immunohistochemistry revealed a similar staining pattern to that described by Cesta et al 2013. Taken together, the presence of alpha2u-globulin (nephropathy) is likely. As casts were only present in 1 and 2 animals of the low and mid dose groups, respectively, the changes were considered treatment-related, but not adverse. In the high dose group, the changes were interpreted as treatment-related and adverse due to the presence of granular casts indicative of tubular injury. Yet, these findings are not relevant for humans. The minimal increase in the presence of basophilic tubules in high dose males was interpreted as a sequelae of the alpha2u-globulin nephropathy. As only single tubules were affected, this change was considered treatment-related, but not as adverse.

An observed reduced mean absolute weight of brain, heart, and prostate in high dose males as well as the reduced mean absolute and relative weight of the adrenal glands and the heart of high dose females were considered possibly treatment-related, but not adverse, as no histopathological findings were present.

The results of the differential ovarian follicle count – comprising the numbers of primordial and growing follicles, as well as the combined incidence of primordial plus growing follicles – showed no significant differences between the control and the high dose group animals.

 

F1-generation, rearing animals, cohort 1B

An observed reduced mean absolute prostate weight and the increased mean relative liver weight in high dose males as well as the reduced mean absolute and relative weight of the adrenal glands of high dose females were considered possibly treatment-related, but not as adverse as no correlating histopathological findings were present in cohort 1A.

 

Surplus F1 generation pups on PND 22 (F1 weanlings not selected for cohorts)

The reduced mean absolute weight of the spleen in male high dose group pups was considered potentially treatment-related, but not adverse as no weight changes or histopathological findings were present in the spleen of cohort 1A animals.

All other findings across generations and cohorts occurred either individually or were biologically equally distributed over control and treatment groups. They were considered to be incidental or spontaneous in origin and without any relation to treatment.

 

Thus, under the conditions of the present extended one-generation reproduction toxicity study, the NOAEL for general, systemic toxicity is at 4000 ppm (about 278 mg/kg bw/d in males and 345 mg/kg bw/d in females) in the F0 parental rat, based on slightly reduced body weights, mainly in males.

The NOAEL in the F1 adult rats is 4000 ppm (about 338 to 347 mg/kg bw/d in males and 361 to 362 mg/kg bw/d in females).

The NOAEL for fertility and reproductive performance for the F0 and F1 parental rats is 12500 ppm (about 887 mg/kg bw/d and 1024 mg/kg bw/d in females during the pre-pairing period, 887 mg/kg bw/ during gestation and 1185 mg/kg bw/d during lactation).

The NOAEL for developmental toxicity in the F1 progeny is 4000 ppm (about 431 mg/kg bw/d during lactation), based on slightly reduced preweaning body weight gain, which was observed at the LOAEL (Lowest Observed Adverse Effect Level) of 12500 ppm (about 1185 mg/kg bw/d during lactation). However, these effects are considered to be mainly due to compound uptake of the offspring via food and not a direct developmental toxic effect. Furthermore, this effect was found at doses above the limit dose of 1000 mg/kg bw/d.

 

References

 

• Hard, G. C. Mechanisms of Rodent Renal Carcinogenesis Revisited. Toxicologic Pathology, 46 (8), 956-969 (2018)


• Cesta MF, Hard GC, Boyce JT, Ryan MJ, Chan PC, Sills RC. (2013). Complex histopathologic response in rat kidney to oral β-myrcene: an unusual dose-related nephrosis and low-dose alpha2u-globulin nephropathy. Toxicol Pathol.;41(8):1068-77.

Effects on developmental toxicity

Description of key information

Key study for developmental toxicity study in non-rodent species (OECD 414, GLP, oral, rabbit, gestation day 6-28; BASF 2022; 40R0267/10R214):

• NOAEL maternal toxicity = 150 mg/kg bw/d


• NOAEL developmental toxicity = 500 mg/kg bw/d

Key study for developmental toxicity study in rodent species (OECD 414, GLP, oral, rat, gestation day 7-17; read across linalool; Politano 2008):

• NOEL maternal toxicity = 500 mg/kg bw/d


• NOEL developmental toxicity = 1000 mg/kg bw/d

Additional information

In the key study for developmental toxicity according to OECD TG 414 and GLP, Tetrahydrolinalool was tested for its prenatal developmental toxicity in New Zealand White rabbits (BASF 2022; 40R0267/10R214). The test substance was administered as an aqueous suspension to groups of 25 inseminated female New Zealand White rabbits orally by gavage in doses of 50, 150 and 500 mg/kg bw/d on gestation days 6 through 28. The vehicle control group, consisting of 25 females, was dosed with the vehicle (0.5% Sodium carboxymethyl cellulose suspension in deionized water (with 5 mg/100 mL Cremophor EL) in parallel. A standard dose volume of 10 mL/kg bw was used for each test group. At terminal sacrifice on GD 29, 22-24 females per group had implantation sites. Food consumption and body weight of the animals were recorded regularly throughout the study period. The state of health of the animals was checked each day. On GD 29, all females were sacrificed and assessed by gross pathology (including weight determinations of the unopened uterus and placentas). For each doe, corpora lutea were counted and number and distribution of implantation sites (differentiated between resorptions, live and dead fetuses) were determined. The fetuses were removed from the uterus, sexed, weighed and further investigated for any external, soft tissue and skeletal (inclusive cartilage) findings.

Regarding clinical examinations, signs of maternal toxicity were observed at the high-dose level. One high-dose female died after abortion before treatment on GD 28 and two females had to be sacrificed after abortion ahead of schedule. In addition, the high-dose does showed a reduction in mean food consumption (up to 47% below control) resulting in an overall reduced food consumption of 22% less compared to the control during the whole treatment period (GD 6-28). The body weight/body weight gain values were also decreased and if calculated for the treatment period (GD 6-28), the high-dose does gained about 31% less weight in comparison to the control does. The above-mentioned findings were assessed as treatment-related and adverse. No treatment-related, adverse effects were observed in the low and mid dose group.

No differences of toxicological relevance between the control and the treated groups were determined for any reproductive parameters, such as conception rate, mean number of corpora lutea, mean number of implantations, as well as pre- and post-implantation loss. All differences observed are considered to reflect the normal range of fluctuations for animals of this strain and age or cannot be related to the treatment.

Similarly, no influence of the test substance on uterine weight, placental weight, fetal weight and sex distribution of the fetuses was noted at any dose.

The overall affected fetuses/litter incidence of all different types of variations was statistically significantly increased in the high-dose group. Specifically, the affected fetuses/litter incidence of ‘supernumerary thoracic vertebra’ was statistically significantly increased in this dose group. This finding is unlikely to be detrimental for survival or health, which qualifies it to be of low toxicological concern. In addition, the incidence of all classified fetal variations was well within the historical control range. It should be noted that this minor change of skeletal development occurred in the presence of maternal toxicity. Systemic toxicity such as abortion, reduction in food consumption and a decrease in body weight gain are evidence for distinct maternal stress which in turn may have had an impact on fetal development.

There was no evidence that the test substance was teratogenic at any of the tested doses.

Under the conditions of this prenatal developmental toxicity study, the oral administration of Tetrahydrolinalool to pregnant New Zealand White rabbits from implantation to one day prior to the expected day of parturition (GD 6-28) provided evidence of maternal toxicity, such as a reduction in food consumption and a decrease in body weight gain at the highest tested dose level of 500 mg/kg bw/d. In conclusion, the no observed adverse effect level (NOAEL) for maternal toxicity is the mid-dose level of 150 mg/kg bw/d. Since there was no evidence for toxicologically relevant adverse effects of the test substance on fetal morphology at any dose, the no observed adverse effect level (NOAEL) for fetal developmental toxicity is the highest dose of 500 mg/kg bw/d.

No developmental toxicity/teratogenicity study according to OECD TG 414 is available in a second (rodent) species for the registered substance Tetrahydrolinalool. However, information concerning developmental toxicity in rats can be deduced from the key reproductive toxicity study (EOGRTS; BASF 2022; 91R0267/10S213). No effect on the number of implantation sites, number of live and stillborn pups, sex ratio, clinical observations in pups or pre- and postnatal survival were observed. Mean pup weights were slightly decreased in the high dose group predominantly during the second half of the lactation period (during PND 4 – 7, PND 14 – 21 and PND 1 - 21 in male and female pups as well as both sexes combined down to -17 % vs. ctrl., respectively). In line, the time of vaginal opening and preputial separation was later in the high dose group F1 animals, but this was attributable to the decreased body weight development in this group, since sexual maturation commenced even at comparable or even slightly lower body weights when compared to the controls. There were no effects on anogenital distance or nipple retention in male pups.

No abnormalities were observed at necropsy of the F1 pups, which indicates no evident teratogenic effect of Tetrahydrolinalool in rats up to the limit dose of 1000 mg/kg bw/d. The pattern of organs affected by treatment with Tetrahydrolinalool (predominantly the kidney) was comparable between the parental P0 and the offspring F1 generation. Changes in organ weights selectively observed in F1 offspring were not correlating with any histopathological findings and were not considered adverse effects. Accordingly, the NOAEL for developmental toxicity in the F1 progeny was set at 4000 ppm (about 431 mg/kg bw/d during lactation), based on slightly reduced preweaning body weight gain, which was observed at the LOAEL of 12500 ppm (about 1185 mg/kg bw/d during lactation). However, these effects are considered mainly due to compound uptake of the offspring via food and not a direct developmental toxic effect.

Furthermore, a developmental toxicity study in rats (according to OECD 414 and GLP) with the structurally analogous substance linalool is available, which represents a key study to fulfill the data requirement for a developmental toxicity study in a rodent species (Politano 2008). Presumed pregnant Sprague-Dawley rats (25/group) received oral gavage doses of 0, 250, 500, or 1000 mg/kg bw/day linalool from gestational days 7 to 17. The presence of spermatozoa and/or a copulatory plug in situ was designated as gestational day 0. Rats were observed for viability, clinical signs, body weights, and feed consumption. Caesarean sectioning and necropsy occurred on gestational day 21. Uteri were examined for number and distribution of implantations, live and dead fetuses, and early and late resorptions. Numbers of corpora lutea were also recorded. Fetuses were weighed and examined for gender, gross external changes, and soft tissue or skeletal alterations. There were no maternal deaths, clinical signs, or gross lesions that were considered related to linalool. During the dosage period, mean relative feed consumption was significantly reduced by 7 % and mean body weight gains were reduced by 11 % at 1000 mg/kg/day. During the post-dosage period, feed consumption values at 1000 mg/kg bw/day were significantly higher than vehicle control values, which corresponded to the increase in body weight gains during this period. Caesarean section and litter parameters, as well as fetal alterations, were not affected by linalool at any of the three dosages tested. Based on these data, the maternal NOEL of linalool is 500 mg/kg bw/day, whereas the developmental NOEL is 1000 mg/kg/day.

Overall, the key developmental toxicity studies in rabbits and reproductive toxicity study (EOGRTS) in rats with Tetrahydrolinalool, as well as the key developmental toxicity study in rats with the structural analog linalool, demonstrate, that Tetrahydrolinalool is not a developmental toxicant.

Justification for classification or non-classification

The present data on reproductive toxicity do not fulfill the criteria laid down in regulation (EC) 1272/2008, and therefore, a non-classification is warranted.