Linalyl acetate

Endpoint summary

Key value for chemical safety assessment

Effects on fertility

Description of key information

Read across (linalool CAS 78-70-6): Reproductive and developmental toxicity screening test similar to OECD 421, acc. to GLP:

Maternal NOAEL = 500 mg/kg bw/d (equivalent to 365 mg/kg bw/d linalool)

Developmental NOAEL = 500 mg/kg bw/d (equivalent to 365 mg/kg bw/d linalool) 

Read across (dehydrolinalool CAS 29171-20-8):

Reproductive and developmental toxicity screening test according to OECD 421, GLP:

Maternal NOAEL = 200 mg/kg bw/d

Developmental NOAEL = 200 mg/kg bw/d

Additional information

No data for toxicity to fertility are available for linalyl acetate. Since linalyl acetate is hydrolysed in intestinal fluids resulting in the metabolites linalool and acetic acid, repeated dose and reproductive toxicity studies using linalool (CAS 78-70-6) were included into this assessment. Furthermore, comparable toxicity profiles were noted for linalool and dehydrolinalool (CAS 29171 -20 -8) in acute toxicity studies and repeated dose studies, leading to alpha-2µ-globulin nephropathy, metabolic enzyme induction in the liver, hypersalivation and sedation / ataxia after repeated application. Therefore the available repeated dose and reproduction/developmental toxicity studies using dehydrolinalool were adopted to linalyl acetate via read-across.

 

In a repeated dose study according to OECD 407 and GLP, Sprague-Dawley rats received 160, 400 or 1000 mg/kg bw/d of the tested material (containing 72.9 % linalool in essential oil) via gavage during 28 days (HLA642-460). In this study, no macroscopically or microscopically remarkable findings regarding male or female reproductive organs have been reported up to 1000 mg/kg bw/d (equivalent to 729 mg/kg bw/d linalool), indicating an absence of toxicity to fertility.

 

A reproductive and developmental toxicity screening test (similar to OECD 421, acc. to GLP) was performed (Lorillard 412-005). Female Crl:CD (SD)BR rats were orally (gavage) administered 0, 250, 500 and 1000 mg/kg/day of coriander oil (containing 72.9% linalool) throughout the 7-day premating period, mating, gestation and lactation (post-natal day 4). Controls were treated with the vehicle only and males were not dosed. The rats were observed for clinical signs, weight, feed consumption and were necropsied and examined for gross lesions. Mating performance, duration of gestation and parturition and number of implantation sites were recorded. Litter (F1) were examined for number, viability, weight, sex ratio and external morphology. Delivered pups were additionally examined for viability, clinical signs and body weight during a 4-day postparturition period.

Excess in salivation was noted in all groups being significant for mid and high dose group. A significant number of rats in the 1000 mg/kg/day group had urine-stained abdominal fur during the premating period and 1-2 rats in this group showed ataxia and/or decreased motor activity infrequently during the premating and/or gestation periods.

Biologically remarkable decreases in body weight gain and feed consumption occurred in the 1000 mg/kg/day dose group during premating (significant after first dosage). During gestation, biologically remarkable increase in weight and feed consumption occurred for each group given the test article. Statistically significant increases in body weight gain occurred for the low and high dosage group rats and statistically significant increases in absolute and relative feed consumption values occurred for each group given the test article. These effects decreased in severity during lactation.

No adverse effects on mating, fertility or the durations of gestation or parturition occurred for female rats given dosages of linalool up to 1000 mg/kg/day, indicating the absence of adverse effects of linalool on female fertility.

Pup mortality was significantly increased for litters of dams given 1000 mg/kg/day linalool. When comparing implantation averages to delivered litter size in the 1000 mg/kg/day, the litter size was more decreased as compared to other groups. This indicates an increase in resorptions in the high dosage group. No other test substance related adverse effects were noted in the offspring.

The maternal NOEL for coriander oil was below 250 mg/kg/day based on clinical signs (salivation) and increased body weight gains and feed consumption. These changes were not considered to be evidence for severe adversity, hence the NOAEL was set at 500 mg/kg/day. The high-dose group (1000 mg/kg/day) showed reduced litter sizes, indicating in utero deaths, and significant increases in pup mortality in the first four days postpartum. No adverse effects regarding mating, fertility or duration of gestation or parturition occurred in any treatment group up to 1000 mg/kg/day. Clear adverse effects on reproductive performance and pup development occurred at 1000 mg/kg/day, that also resulted in significant maternal clinical signs, significant inhibition of average maternal weight gain before mating and significant increases in maternal weight gain and feed consumption during gestation. In the absence of significant toxicity to the dams, the test substance did not affect the reproductive performance or the developmental parameters of pups. The effects observed on reproduction and development are not, therefore, uniquely reprotoxic or developmentally toxic effects but seen to be a consequence to general toxic effects.

The maternal and developmental NOAELs were established to be 500 mg/kg/day corresponding to a NOAEL of 365 mg linalool/kg bw/day.

 

Dehydrolinalool was tested in a preliminary reproductive toxicity screening test according to OECD 421 and GLP in Fü-Albino (RORO) rats (DSM B154967). Twenty animals per sex and group were given the test article formulated in rape seed oil at doses of 0 (control), 50, 200 or 750 mg/kg/day (administration volume 5 ml/kg/day). The administration period for both sexes was through premating (2 weeks), mating (up to 2 weeks) and gestation up to day 4 of lactation.

Three females died/were sacrificed during pre-mating period and 3 females died/were sacrificed with delivery complications at the highest dose group. Body weight development and food consumption was comparable in all experimental groups. Hypersalivation was observed in males and females at 750 mg/kg throughout the study. However, this was not considered relevant for NOAEL derivation. Females at the highest dose groups showed sedation/ataxia during gestation and lactation. The duration of gestation, mean number of implantations, resorption rate, mean number of pups per litter, mean pup weight, sex ratio were not significantly affected by the treatment in either dose group. In addition, no signs of teratogenic action were observed in any pup of dams which survived the scheduled date of necropsy in any dose group.

However, at 750 mg/kg the pup live birth index and pup viability index was slightly reduced, when compared with the concurrent control. Moreover, dams with delivery complications were observed at the dose of 50 mg/kg (1 dam) and at 750 mg/kg (3 dams). No delivery complications were noted in the mid dose group (200 mg/kg) and therefore the finding at low dose level was not considered adverse due to missing dose-response relationship. The incidence of abnormalities in the urinary system and of renal and testicular development was increased at 750 mg/kg mainly due to pups of dams which died or were sacrificed during the delivery. Reduced live birth index is as well to a great extent related to delivery problems.

It is concluded, that dehydrolinalool does not adversely affect mating and fertility of males and females when administered in rape seed oil by oral gavage to rats from 2 weeks premating through day 4 of lactation up to 750 mg/kg/day. Delivery complications were noted at 50 and 750 mg/kg/day. The pup live birth index and pup viability index was slightly decreased at the maternally toxic dose of 750 mg/kg/day. An increased incidence of abnormalities of the urinary system and of impaired renal and testicular development was noted in pups of mothers treated with 750 mg/kg/day. However, most of the observed abnormal pups belong to those dams which died or were sacrificed moribund during delivery. No adverse effects on the reproductive indices and on the developing conceptus/pup were noted up to 200 mg/kg/day. The no-observed-adverse-effect-levels (NOAEL) were set at 200 mg/kg/day for the offspring and dams. The NOAEL was 750 mg/kg bw/day for males.

In EPA’s Endocrine Disruptor Screening Program (EDSP) linalyl acetate has been screened for potential endocrine disruption (see https://actor.epa.gov/edsp21/). Linalyl acetate has been found active in a bovine and human receptor binding assay with an AC50 value of 17.78 µM and 10 µM respectively (cytotoxicity limit 161.93 µM). These assays, i.e. the NVS_NR_bER assay and the NVS_NR_hER assay, detect loss of signal to the binding of the ER in a single radio-ligand binding design (extracted from bovine uterine membranes or MCF7 human breast cells), induced by an 18h incubation with linalyl acetate. Based on the outcome of all in vitro assays performed with linalyl acetate, the ToxCast model predictions led to a bioactivity prediction for the estrogen receptor (antagonist), whereas no agonistic ER and androgen receptor agonistic/antagonistic activity was predicted. Linalyl acetate however was inactive in a comparable murine isolated estrogen receptor assay. The biological relevance of the isolated receptor interactions observed are to be questioned, since linalyl acetate was inactive in all functional ER cell based assays to detect agonistic and antagonistic chemical activity performed in this program, i.e. 15 assays using different cell lines and readouts for estrogen receptor activation. Furthermore, the metabolically related read across substance linalool was fully inactive in all screening tests performed under the EDSP. The present in vivo data presented above do not provide evidence for antagonistic estrogen receptor activity of the relevant metabolite linalool and the structurally related dehydrolinalool and therefore question the biological relevance of the isolated findings of the EDSP.

 

Taken together, linalool, which was tested for female fertility, and dehydrolinalool, which was tested for male and female fertility showed no adverse effects. With regard to developmental toxicity / teratogenicity, it is concluded that both substances are neither developmental toxic nor teratogenic at doses not being maternally toxic. However, at maternal toxic doses, reduced litter sizes and increased pup mortality was noted for both substances. Further data on developmental toxicity are discussed in the respective section “Effects on developmental toxicity”. In analogy to the metabolite linalool and their structurally related dehydrolinalool, linalyl acetate is not considered to affect fertility or reproductive performance.

The available repeated dose toxicity studies (28-day or 90- day studies, OECD 421 screening studies) indicate no adverse effects on reproductive organs or tissues or reveal other concerns in relation with reproductive toxicity. However, an extended one-generation reproductive toxicity study according to columns 1 and 2 of Section 8.7.3., Annex X is planned and a respective testing proposal is included into this dossier.

Effects on developmental toxicity

Description of key information

Developmental toxicity study (OECD 414, GLP, oral, rat, gestation day 7-17) - read across linalool:
- NOEL maternal toxicity = 500 mg/kg bw/d linalool; 
- NOEL developmental toxicity and fetotoxicity = 1000 mg/kg bw/d linalool

Additional information

No data for developmental toxicity/teratogenicity are available for linalyl acetate. However, there is one reliable study which was conducted with the metabolically related test substance linalool (CAS 78-70-6) which was included into this assessment via read-across.

A one-generation reproductive toxicity screening study (according to FDA guidelines for reproduction studies for safety evaluation of drugs for human use and according to GLP) was conducted with an essential oil of coriander containing 72.9 % natural linalool (ArgusResearchLabs412-005). Groups of 10 virgin female rats were administered by gavage 250, 500 or 1000 mg/kg bw/d essential coriander oil (equivalent to 182, 365 and 729 mg/kg bw linalool) in corn oil, respectively only the vehicle in the controls. The females were mated with untreated males. Clinical signs, body weight and food consumption were recorded throughout the study. Mating performance, fertility, duration of gestation and parturition, maternal behaviour, litter size, dystocia, number of implantation sites and gross lesions at necropsy were examined. F1 offspring were examined for viability, sex ratio, external morphology and body weight at birth and on day 4 postpartum.

For developmental toxicity, adverse effects were only noted in the maternal high-dose group, with foetal deaths in utero, a concomitant decrease in live litter size and a significant increase in pup morbidity and mortality during the first four or five days postpartum. However, even at the highest dose administered to dams, there were no effects on, pup sex ratio, pup body weight or gross morphology. While at 1000 mg/kg bw/d there was significant foetal and pup mortality, there were no gross signs of teratogenicity in the pups. Specifically, the original report mentioned that "no anatomical malformations or variations were revealed by external examination or necropsy of the pups in this study". As stated in the section “fertility” , the effects on the offspring observed are not uniquely developmentally toxic effects but are considered to be a consequence to general toxic effects.

In the key study according to OECD 414 and GLP the developmental toxicity of linalool was evaluated in presumed pregnant Sprague-Dawley rats (25/group; Politano 2008). Oral dosages of 0, 250, 500, or 1000 mg/kg bw/day linalool were administered by gavage on 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 postdosage 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. On the basis of these data, the maternal no observed effect level of linalool is 500 mg/kg bw/day, whereas the developmental no observed effect level is1000 mg/kg/day.

Taken together, in analogy to linalool, linalyl acetate is not considered to be a developmental toxicant.

Toxicity to reproduction: other studies

Additional information

No data available.

Justification for classification or non-classification

The present data on reproductive toxicity do not fulfill the criteria laid down in 67/548/EEC and 272/2008/EEC, and therefore, a non-classification is warranted.