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Description of key information

- A 14-day repeated dose toxicity study: NOAEL = 500 mg/kg bw/d
- A 14-day repeated dose toxicity study: NOAEL = 150 mg/kg bw/d
- A reproductive screening study by oral (similar to OECD guideline No. 421): NOAEL (~45-day exposure) >= 100 mg/kg bw/day.
- 90-day repeated dose toxicity study by dermal: LOAEL rat > 125 mg/kg bw/day for systemic effect (both dermal and oral exposures) and LOAEL >= 125mg/kg bw/day for local effect
- No data available by inhalation: no classification for STOT-RE based on the overall data on overall toxicological data and the toxicokinetics of HCA.

Key value for chemical safety assessment

Repeated dose toxicity: via oral route - systemic effects

Endpoint conclusion
Dose descriptor:
NOAEL
150 mg/kg bw/day
Study duration:
subacute
Species:
rat

Repeated dose toxicity: dermal - systemic effects

Endpoint conclusion
Dose descriptor:
LOAEL
125 mg/kg bw/day
Study duration:
subchronic
Species:
rat

Additional information

ORAL ROUTE:

 

Three studies performed by oral route on α-Hexylcinnamaldehyde (HCA) were identified as weight evidence.

 

The first study is a Reproductive Developmental Toxicity Screening Test performed according to the OECD No. 421 and in compliance with the GLP. HCA was administered by gavage at 0, 12.5, 25, 50 and 100 mg/kg bw/day to male and female rats daily for 14 days before mating, during 7 -day cohabitation period, through pregnancy and until postpartum day 5.

In total both males and females were exposed to HCA for approximately a 45 -day period. The following parameters were evaluated: viability, clinical observations, body weights, feed weights, mating and fertility, delivery and litter observations, organ weights, necropsy observations and histopathology. The pups were clinically observed and weighed, and at sacrifice, they were externally and internally examined including single cross-sections of the head.

The effects observed were a reduction of maternal body weight gain (22%) and food consumption in the 100 mg/kg bw/day group on days 1 and 5 of lactation in comparison to the vehicle control group.

Under the conditions of this study a NOAEL of 100 mg/kg bw/day or greater was determined.

In a 14 days repeated dose study (second study), groups of Crl:CD (SD) rats (5/sex/dose) were administered daily with alpha-hexyl cinnamic aldehyde (HCA) at dose levels of 0 (vehicle control), 100, 250, 500 and 1000 mg/kg bw/day in corn oil by oral gavage. Animals were then observed for clinical signs, mortality, body weights and feed consumption throughout the study period and were all macroscopically necropsied after sacrifice or death.

At 1000 mg/kg bw/day, several rats died or were euthanized after two or three days of treatment, and dosage administration in this dosage group was subsequently discontinued. Signs of respiratory distress (i.e., bradypnea, gasping), mild to severe dehydration, urine-stained abdominal fur, decreased motor activity, ptosis, slight excess salivation, lost righting reflex, chromorhinorrhea, chromodacryorrhea and piloerection were observed at 1000 mg/kg bw/day; a few observations of excess salivation occurred in males and females at 500 mg/kg bw/day. At 1000 mg/kg bw/day, net losses in body weight were observed in both sexes during the first three days of dosage administration, with transient reductions in body weight gain occurring at 250 and/or 500 mg/kg bw/day during the same period. Corresponding reductions in feed consumption occurred in male and female rats given 1000 mg/kg bw/day of hexyl cinnamic aldehyde during the first three days of the study. Gross pathological observation revealed irritation of the gastric mucosa in male and female rats that died or were euthanized early in the 1000 mg/kg bw/day dosage group.

Microscopic examination was limited to gross lesions, kidneys (500 and 1000 mg/kg bw/day dose groups only), stomach, and the small and large intestines. In the high dose one animal had mild erosion in the non-glandular mucosa of its stomach. Several animals had minimal or moderate tubular degeneration and/or mild tubular dilation. All these lesions were considered test substance-related. The no effect level for the stomach and kidney changes was 500 mg/kg bw/day. The other gross and microscopic findings were considered incidental, commonly observed in controls of this strain and age of rats, and were considered unrelated to the administration of HCA.

Severe clinical signs, mortality, reduced body weight gain, reduced feed consumption, pathological signs of gastric irritation and microscopical changes in stomach and kidneys were observed at 1000 mg/kg bw/day. Under the test conditions, the No Observed Effect Level (NOEL) of hexyl cinnamic aldehyde in rats was considered as 250 mg/kg bw/day while the No Observed Adverse Effect Level was determined at 500 mg/kg bw/d based on the clinical effects, i.e. excess salivation and mild dehydration.

In the third study, HCA was administered orally by gavage to albino rats at 150, 375, 750, 1000 and 1500 mg/kg bw for 14 consecutive days.

One male died after three days of treatment at 1500 mg/kg bw/d. Profuse salivation occurred in the majority of animals following daily gavage. Body weights did not appear to be affected by the administration of HCA at the dose levels investigated. Gross pathological observation revealed mild to moderate irritation of the gastric mucosa in all groups with the exception of three animals treated at the 150 mg/kg bw/d level. These effects were considered as local effect due to simple destruction of membranes.

Under the conditions of this study a NOAEL of 150 mg/kg bw/day is determined based on the local effects on the gastric mucosa.

Supporting studies conducted on α-Amylcinnamaldehyde (ACA) were considered as relevant based on a read-across approach. In fact, HCA and ACA are alkyl-substituted cinnamaldehyde derivatives. Common structural features of these substances are that they contain a 3-phenyl-2-propenal backbone as illustrated in attached file. HCA and ACA are rapidly absorbed from the gut, metabolized and excreted primarily in the urine (within 24 hours) and, to a minor extent, in the faeces. The position and size of the substituent do not significantly affect the pathways of metabolic detoxication of cinnamyl derivatives. Therefore, Cinnamyl derivatives containing α-alkyl substituents, such as HCA and ACA, are extensively metabolized via β-oxidation followed by cleavage to yield mainly the corresponding hippuric acid conjugate excreted in the urine (see § 7.1). An illustration of the metabolic pathway is included as attached background material. However, larger substituents located at thealpha-position (like HCA) inhibitsbeta-oxidation to some extent and are excreted primarily unchanged or as the conjugated form of the cinnamic acid derivative.

Hence, these supporting studies showed an absence of effect up to 30 mg/kg bw/d in a 90-day repeated dose oral toxicity study while, at the highest dose (c.a.300 mg/kg bw/day), a slight but statistical significant increase in the relative weight of the liver and the kidneys may be considered of low toxicological concern. Therefore, the results obtained with ACA were consistent with those observed from the HCA testing studies.

In conclusion, the available data are considered adequate for the purpose of classification and labelling.Considering the overall results of studies and their consistency, no classification is justified for HCA regarding specific target organ toxicity - repeated exposure since no specific target organ for significant toxicity is identified, i.e.at the limit dose of classification (≤ 100 mg/kg bw/d for 90-day exposure).

 

DERMAL ROUTE:

 

Three studies performed by dermal route on Hexylcinnamaldehyde (HCA) were identified as weight evidence.

 

In the range-finding study of the 90-day repeated dose toxicity described below, HCA was applied percutaneously to the shaved dorsa of 10 male Sprague-Dawley rats at dose levels of 0.15, 0.375, 0.75, 1.5 and 3.0 g/kg bw/day for 28 consecutive days.

Erythema and eschar formation with cracking and dryness of the skin at the test article application site were noted at all dose levels. Hyperirritability was noted at 0.75, 1.5 and 3.0 g/kg and abnormally arched backs at 1.5 and 3.0 g/kg bw/d. The two high dose (3.0 g/kg) rats developed ataxia and survived only 7 and 11 days of treatment. Body weights and food consumption differed little at the 0.25, 0.375 and 0.75 g/kg bw/d dose levels. At 1.5 and 3.0 g/kg bw/d, body weights were reduced substantially but food intake was depressed only at 3.0 g/kg bw/d.

Intergroup comparison with respect to blood biochemical parameters revealed a dose-related negative effect on clotting time and white blood cell count. The 1.5 and 3.0 g/kg levels demonstrated a marked shift in the proportion of segmented neutrophils to lymphocytes. A reveiw of the various blood biochemical parameters investigated, suggested an adverse dose-related effect revealed by a progressive increase in BUN, SAP and SGPT values. The SGOT and Glucose values indicated a dose-related trend (decrease in Glucose and increase in SGOT) especially in group 3 (0.75 g/kg bw/d) and 4 (1.5 g/kg bw/d).

Gross pathological examination revealed local effects such as thickening of the skin at the application sites for the dose levels 0.375 and 0.75 g/kg bw/d. At 1.5 g/kg bw/d the test article caused thickening of the skin and erythema of both the dermis and epidermis along the lateral aspects of the application site.

Application of HCA at 3.0 g/kg bw/d produced dry and cracked skin at the administration site, body emaciation, congested lungs and gastrointestinal irritation. Both absolute and relative organ weight data displayed decreases in the weights of the thymus and spleen at 1.5 g/kg and other treated groups. The relative organ weight data for the gonads (right and left) displayed slightly heavier weights at the 1.5 g/kg dose level. Microscopic examination of the skin at the application dose levels except 0.15 g/kg bw/d. At 0.75 and 1.5 g/kg bw/d, kidney alterations consisting of focal dilation of the tubules were noted. Congestion of the gastrointestinal tract with sub-acute to chronic necrotizing and hemorrhagic enteritis of the small intestine was observed at 3.0 g/kg. Lymphoid depletion and necrosis with reticulo-endothelial hyperplasia were observed in one animal at 3.0 g/kg bw/d.

In the sub-chronic toxicity study performed similarly to OECD guideline No. 411 (main study following the range-finding study above), HCA was administered percutaneously to rats at 125, 250, 500 and 1000 mg/kg bw/day for 90 consecutive days. For control purposes, a control group was maintained without treatment.

Percutaneous administration of HCA resulted in dose-dependent dermal irritation characterized by erythema, cracking, dryness and sloughing. Five male and three female rats did not survive 90 days of treatment at 1000 mg/kg bw/d. Significant changes in the body weights, the absolute food consumption and the absolute food intake were observed in animals treated at both highest doses.

Hematology and clinical biochemistry were recorded after 13 weeks of test article administration. Urinalysis data obtained during the conduct of the study were unremarkable.

Gross examination at necropsy revealed dose-related irritation of the gastrointestinal tract mucosa and the treated skin. The liver and kidney weights of treated females were significantly increased at 250, 500 and 1000 mg/kg bw/d. Histopathological examination revealed morphological alteration at the 1000 mg/kg bw dose level in the form of hepatic hydropic vacuolization and single cell degeneration, splenic lymphoid depletion and fibrosis, focal gastric ulceration and chronic necrotizing dermatitis. Bone marrow examination revealed dose-related increase in the myeloid-erythroid and decrease of the cell-fat ratios. These results represented systemic effects while local effects were also observed since application of HCA induced cracking and dryness of the skin in all the treated animals

In both studies described above (the range-finder and the main study), the authors suggested that the gastrointestinal irritation observed at the highest tested doses was a consequence of HCA intake during grooming and ingestion of necrotic skin. Indeed neither coverage nor restrainers were used to prevent ingestion during the rat skin exposure. Therefore, the gastrointestinal irritation should be considered as local effect due to oral exposure to HCA. Moreover, this assumption is consistent with the irritation observed at the highest doses in the repeated dose oral toxicity study (see § 7.5.1). Systemic effects observed at this dose are more likely the consequence of HCA ingestion rather than the results of HCA skin application itself. Finally, the skin absorption potential of HCA which is estimated to be very low (0.183 %, see §7.1.2) supports this hypothesis.

 

Based on the observed effects, a LOAEL of 125 mg/kg bw/d can be set for local effects based on skin irritation while a relevant LOAEL for systemic effects cannot be determined since the animals were exposed both by dermal and oral route. However, as no systemic effect was observed at 125 mg/kg bw/d, it is assumed that the LOAEL for systemic effect by dermal route is likely much higher than this dose and therefore higher than the dermal dose limit of the CLP classification (≤ 200 mg/kg bw/d for 90-day exposure).

 

In the third repeated dose dermal toxicity study, HCA (5% purity in phenyl ethyl alcohol) was applied to the shaved skin of Sprague-Dawley Albino rat (5/sex/dose) at dose level of 25 mg/kg bw/d (0.5 mL/kg), daily, 7 days/week during a 90-day period. A control group received phenyl ethyl alcohol alone (1.0 mL/kg).

All rats were observed daily and skin reactions were recorded. Body weights were recorded weekly. At termination, selected hematology, clinical chemistry and urinalysis parameters were evaluated. All animals were examined grossly and liver and kidneys were weighed. Microscopic examination of the skin, liver, kidney, sterna bone marrow and spinal cord was conducted.

One male rat treated with HCA died on Day 14. At necropsy, there was evidence of a lung infection. The death was not considered to be related to treatment.

There were no dermal reactions observed on any rats in any group.

Under the conditions of the study there was no evidence of toxicity induced by treatment with HCA. The NOAEL is therefore 25 mg/kg bw/d, i.e. the highest dose tested.

Hence, the overall available data are considered adequate for the purpose of classification and labelling.Considering the results of both studies and their consistency,does not justify the classification of HCA for specific target organ toxicity - repeated exposure since no specific target organ for significant toxicity is identified,i.e.at the limit dose of classification.

.

INHALATION:

 

No data is available for chronic exposure by inhalation to HCA or by of its analogues. However, an acute toxicity study was performed in rats exposed by inhalation to aerosol of HCA (Klimisch 2, see §7.1.2).The animals were exposed to HCA aerosol form respirable particles of 1.3 µm diameter at 5 mg/L nominal concentration (2.12 mg/L actual concentration), for four hours. None of the animals died during exposure and following the 14-day observation period. Moreover, there were no clinical changes of possible toxicological significance. However, enlarged bronchial lymph nodes sometimes accompanied by pulmonary congestion, or multiple grey-green pinpoint foci in the lungs were recorded and considered as local effects.

Taking into account the relevant physico-chemical properties of HCA for inhalation such as the log Pow = 5.3 (see §4.7) and the water solubility = 1.62 mg/L (see § 4.8), HCA is a lipophilic liquid slightly soluble in water which is consistent with the available toxicokinetics data. Therefore, it is assumed that during exposure by inhalation, HCA is likely absorbed at the alveolar level and then, metabolized via β-oxidation and excreted primarily in the urine (within 24 hours) and, to a minor extent, in the faeces in the same way that occur after oral absorption (see §7.1). It is unlikely that repeated exposure by inhalation induces target organ toxicity at the limit of classification by inhalation according to the CLP (≤ 0.2 mg/L for 90-day exposure).

 


Repeated dose toxicity: dermal - systemic effects (target organ) other: skin

Justification for classification or non-classification

Harmonized classification:

No harmonized classification is available according to the Regulation (EC) No 1272/2008 including ATP1.

Self-classification:

The available data are considered adequate for the purpose of classification and labelling. The evidence available does not justify the classification of alpha- Hexylcinnamaldehyde for specific target organ toxicity - repeated exposure. No specific target organ for significant toxicity is identified.

No self-classification is proposed according to the Directive 67/548/EEC and the Regulation (EC) No. 1272/2008 (CLP Regulation).