Palm oil, epoxidized

Skin sensitisation

Administrative data

Endpoint:

skin sensitisation: in vivo (non-LLNA)

Type of information:

migrated information: read-across from supporting substance (structural analogue or surrogate)

Adequacy of study:

key study

Study period:

13 July 1981 to 4 September 1981

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: see 'Remark'

Remarks:

There is no indication of the number of animals in the control group. There is no indication in the report that the concentration of the test substance used was the highest to cause mild-to-moderate skin irritation. Or that the concentration used for the challenge exposure was the highest non-irritant dose. This read-across is based on the hypothesis that source and target substances have similar toxicological properties because of their structural similarities and they are assumed to have similar toxicokinetic profiles i.e. they are expected to be metabolised in a similar fashion. The target substance Epoxidized Palm Oil (EPO) and source substance Epoxidized Soybean Oil (ESBO) are derived respectively from their raw materials, palm oil and soybean oil, and are of variable composition consisting of fatty acid triglycerides. Both EPO and ESBO are organic UVCB sub-type 1: substances of biological nature that have been modified in chemical processing. Both are manufactured by the reaction of the respective oils with an epoxidizing agent (50-60% hydrogen peroxide at 60-75°C). The olefinic bonds of the oils are converted to epoxy oxirane groups. As Palm oil has lower unsaturated bonds than Soybean Oil, less of the epoxidizing agent hydrogen peroxide is required and thus EPO has a lower epoxidized adduct content than ESBO and is therefore expected to be less chemically reactive. The % epoxidation in ESBO is 6-8% while the % epoxidation in EPO is 2.5-3.5%. The target substance (EPO) and source substance (ESBO) have a structurally similar backbone which is an epoxidized triglyceride structure derived from one glycerol molecule and three fatty acid molecules. Therefore, the source and the target substances share structural similarities with common functional groups and side chains varying in their length and the amount of epoxide groups. The target substance contains 8 fatty acids with the largest components being C16:0 palmitic acid (44%), C18:1 oleic acid (39.2%) and C18:2 linoleic acid (10.1%). The source substance contains 5 fatty acids with the largest components being C16:0 palmitic acid (11.3%), C18:1 oleic acid (39.2%) and C18:2 linoleic acid (55.8%). ESBO does not contain lauric (C12), myristic (C14) and arachidic (C20) acids while they are present in very low amounts in EPO (0.2, 1.1 and 0.3% respectively). Stearic acid (C18:0) is present in both substances at similar levels (4.5% in EPO and 3.4% in ESBO) while α-linolenic acid (C18:3) is present at 0.4% in EPO and 6.4% in ESBO. So, the main component of the triglyceride structure of both EPO and ESBO is C16 (44%; 11.3%) and C18 (54.2%; 88.7%). The data gap for the target substance EPO is a skin sensitisation study (Annex VII, 8.3). No reliable data on skin sensitisation of EPO is available. Therefore, read-across from an existing skin sensitisation study of the source substance, ESBO, is considered as an appropriate adaptation to the standard information requirements of Annex VII, 8.3 of the REACH Regulation for the target substance, in accordance with the provisions of Annex XI, 1.5 of the REACH Regulation.

Cross-reference

Reason / purpose for cross-reference:

reference to same study

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

1981

Report date:

1981

Materials and methods

Test guideline

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 406 (Skin Sensitisation)

Principles of method if other than guideline:

The optimisation test was used, an intracutaneous sensitisatopn procedure exceeding the sensitivity of the method recommended in the "Appraisal of the Safety of Chemicals in Foods, Drugs and Cosmetics" (1959), the US Association of Food and Drug Officials (AFDO).

GLP compliance:

no

Type of study:

guinea pig maximisation test

Test material

Test material information

Constituent 1

Reference substance name:

TK 11'278

IUPAC Name:

TK 11'278

Constituent 2

Reference substance name:

ESBO

IUPAC Name:

ESBO

Constituent 3

Reference substance name:

Epoxidised Soybean Oil

IUPAC Name:

Epoxidised Soybean Oil

Constituent 4

Reference substance name:

Soybean oil, epoxidized

EC Number:

232-391-0

EC Name:

Soybean oil, epoxidized

Cas Number:

8013-07-8

IUPAC Name:

8013-07-8

Details on test material:

- Name of test material (as cited in study report): TK 11'278
- Physical state: Liquid
- Lot/batch No.: prod. Oct. 80
- Expiration date of the lot/batch: January 1982

In vivo test system

Test animals

Species:

guinea pig

Strain:

other: Pirbright White

Sex:

male/female

Details on test animals and environmental conditions:

The test was performed on groups of 10 male and 10 female guinea pigs of the Pirbright White Strain, bred on the premise,s and weighing between 400 to 540 grams.
The animals were housed individually in type 3 Macrolon cages, kept at a constant room temperature of 22 ± 2 °C, at a relative humidity of 55 ± 10 % and in a 12 hour light cycle per day.
The animals were fed standard guinea pig pellets - NAFAG, No. 830, Gossau SG, SWitzerland - ad libitum and had ad libitum access to water.
Bodyweights were recorded immediately before initiation of dosing in the inductin phase and at termination of the study.

Study design: in vivo (non-LLNA)

Induction

Induction 1

Route:

epicutaneous, open

Vehicle:

other: propylenglycol 50 % / saline 50 %

Induction 2

Concentration / amount:

0.1 mL of 0.1 % solution of TK 11'278

Challenge

Challenge 1

Route:

epicutaneous, open

Vehicle:

other: propylenglycol 50 % / saline 50 %

Challenge 2

Concentration / amount:

0.1 mL of 0.1 % solution of TK 11'278

No. of animals per dose:

10 male and 10 female

Details on study design:

The optimisation test was used, an intracutaneous sensitisation procedure exceeding the sensitivity of the method recommended in the "Appraisal of the Safety of Chemical in Foods, Drugs and Cosmetics" (1959), the US Association of Food and Drug Officials (AFDO).

During the induction period the animals received injections every second day (except weekends) to a total of 10 intracutaneous injections of a freshly prepared 0.1 % solution of TK 11'278 in propylenglycol 50 % / saline 50 %. One control group was treated with the vehicle alone ("negative control").

On the first day of week 1, two injections of 0.1 mL were administered into the shaven skin of the right flank and on the following days a single intracutaneous injection was given into the flank.

During the second and third week of the induction period the test material was incroporated in a mixture of saline with complete Bacto Adjuvant. (saline : adjuvant = 1:1)

During week 6 a challenge injection of 0.1 mL of a freshly prepared 0.1 % solution of TK 11'278 in propylenglycol 50 % /saline 50 % was administered into the skin of the left flank.

Twenty-four hours after each injection during the first week of the induction period and 24 hours after the challenge injection the reactions were recorded.

The two largest perpendicular diameters (in mm) and the increase in the skin-fold thickness (in mm) were measured and by multiplication of these values the "reaction volume" was obtained (in µL) for each reading from each animal. The mean volume plus one standard deviation of the induction reactions observed in the individual animal in the first week was taken as representing the skin irritation "threshold" for each animal. Any challenge reaction greater than this threshold value in the induction period was graded as an allergenic reaction and the animal termed "positive". The number of "positive" animals in the test group was compared with the number of animals in the control group (treated with the vehicle alone) that showed a non-specific reaction of at least the same magnitude ("negative control").

During week 8 a subirritant dose (30 % TK 11'278 in vaseline) of the test compound was applied epicutaneously under occlusive dressings which were left in place for 24 hours. The skin irritation was recorded according to Draize (described in the "Appraisal of the Safety of Chemicals in Foods, Drugs and Cosmetics" 1959 of the US Association of Food and Drug Officials (AFD0) 24 hours after removal of the dressings. For irritation score see table below:

Score for Skin Irritation

Erythema and eschar formation
No erythema........................................................ 0
Very slight erythema (barely perceptible) ...... 1
Well defined erythema ....................................... 2
Moderate to severe erythema .......................... 3
Severe erythema (beed redness) to slight
eschar formation (injuries in depth) ...............4
Total Possible Erythema Score .........................4

Challenge controls:

No data

Positive control substance(s):

no

Results and discussion

Positive control results:

No data

In vivo (non-LLNA)

Results

Results 1

Reading:

other: after intradermal challenge injection

Hours after challenge:

24

Group:

test chemical

No. with + reactions:

2

Total no. in group:

20

Remarks on result:

other: Reading: other: after intradermal challenge injection. . Hours after challenge: 24.0. Group: test group. No with. + reactions: 2.0. Total no. in groups: 20.0.

Results 2

Reading:

other: after occlusive epicutanous application

Hours after challenge:

24

Group:

test chemical

No. with + reactions:

0

Total no. in group:

20

Remarks on result:

other: Reading: other: after occlusive epicutanous application. . Hours after challenge: 24.0. Group: test group. No with. + reactions: 0.0. Total no. in groups: 20.0.

Any other information on results incl. tables

Challenge reactions after occlusive epicutaneous administration of the test material:

Erythema scoer (Draize Score) 24 hours after removal of the dressing: 0

Neither the male or female guinea pigs displayed erythema.

Table 1        Incidence of positive animals per group after intradermal challenge injection

	No. of positive animals
	No. of treated animals	P
Vehicle alone	2/20	-
TK 11'278	2/20

Table 2        Incidence of positive animals per group after occlusive epicutaneous application

	No. of positve animals
	No. of treated animals	P
Vehicle alone	0/20	-
TK 11'278	0/20

Table 3        Meand Bodywieghts and Standard Deviation (g)

	Vehicle control		TK 11’278
	Male	Female	Male	Female
Pre-test	502/28	450/23	493/21	472/25
End of test	682/46	576/39	685/39	626/33
Mean body weight gain	180	136	187	154

Read-Across Justification: Full report is attached in study summary

3 Analogue approach justification

3.1. Physicochemical properties

Physicochemical data shows that the physicochemical properties of the target and source substances are similar as outlined in the data matrix (Table 3). Both are liquids and the structural differences in the side chains do not significantly influence the physicochemical properties of both substances, i.e. vapour pressure, water solubility and partition co-efficient (log Pow). Both substances are highly insoluble in water; <0.01 mg/L at 30°C for EPO and <0.02 µg/L at 20°C (calculated) for ESBO. Neither of the substances is volatile, with a vapour pressure of 0.5 kPa at 25°C for EPO and 8.4 x 10-8 Pa at 25°C for ESBO. Both substances are highly lipophilic; mean Log Pow >6.2 at 25°C for ESBO and log Pow >10 (calculated) for EPO.

3.2. Toxicokinetics

No specific experimental data on absorption, distribution, metabolism or excretion is available for the source or target substance. Read-across was performed for all human health toxicity endpoints to Epoxidised Soybean Oil (ESBO, CAS No. 8013-07-8). An OECD SIDS report is available that concluded on a proposed metabolic pathway for epoxidised fatty acid esters, including ESBO (OECD, 2006). The toxicokinetic analysis is based on physicochemical data from EPO, read-across ESBO data from in vivo animal models and the OECD SIDS report in the literature (OECD, 2006).

Physicochemical data

The molecular weight of EPO and ESBO is > 500 g/mol and is not in the range for favourable oral absorption (<500 g/mol). The calculated log Pow of EPO (>10) and mean Log Pow >6.2 at 25°C for ESBO indicate they are highly lipophilic and water solubility (<0.01 mg/L at 30°C) for EPO and <0.02 µg/L at 20°C (calculated) for ESBO indicates they are both insoluble in water. These characteristics will not facilitate transport of EPO or ESBO via passive diffusion. Based on its high lipophilicity, absorption of EPO and ESBO via the lymphatic system through micellular solubilisation by bile salts is likely, similar to other vegetable oils. Insolubility in water of both EPO and ESBO indicates low dermal uptake while the high log Pow values for both are an indication for a high uptake into the stratum corneum but little or no penetration into the lower layers of the epidermis and dermis. Overall, the physical state, molecular weight, calculated log Pow and water insolubility indicate that dermal absorption of EPO and ESBO is unlikely. Due to the low vapour pressure of EPO (0.5 kPa at 25°C) and ESBO (8.4 x 10-8 Pa at 25°C) and physical state (liquid), exposure via the inhalation route of both is expected to be negligible. Based on the information available for the analogue ESBO in the OECD SIDS report (OECD, 2006; see ‘Other data in the literature’), during metabolism, breakdown products are produced that are more water soluble than the parent substance i.e. free fatty acids, so it is expected that any EPO metabolites will be excreted in the urine.

Other data in the literature

The OECD produced a report on Epoxidised Oils and Derivatives in 2006 (OECD, 2006), which included ESBO. The OECD SIDS concluded that epoxidised fatty acid esters, such as ESBO and therefore we assume EPO, produce metabolic products with similar primary constituents as other vegetable oils and are assumed to have similar metabolic pathways e.g. breakdown in the gastrointestinal tract by esterases (pancreatic lipase) to epoxidised fatty acids and glycerol which enter the normal nutritional pools (JECFA, 1974). Pancreatic lipase works at the oil/water interface since triglycerides are insoluble. During metabolism in the GI tract, pancreatic lipase preferentially hydrolyses triglycerides to release the free fatty acids from the SN-1 and SN-3 (terminal) positions of the glycerol backbone. The other products of metabolism are mono- and di-glycerides (OECD, 2006). The EFSA Panel on Contaminants in the Food Chain agreed with this assessment for ESBO in 2011 (EFSA, 2011). Overall, the proposed metabolic pathway for ESBO is enzymatic breakdown to epoxidised fatty acids and glycerol; a similar pathway is predicted for EPO. Based on the information available for the analogue ESBO in the OECD SIDS report, during metabolism, breakdown products are produced that are more water soluble than the parent substance i.e. free fatty acids, so it is expected that any EPO metabolites will be excreted in the urine.

Available in vivo toxicological data

The in vivo read-across data from ESBO indicate no adverse effects if oral absorption occurs (acute oral LD50 of >5,000 mg/kg (3), 2 year combined chronic/carcinogenicity toxicity study

NOEL (male) of 1000 mg/kg bw/day and NOEL (female) of 1400 mg/kg bw/day (13), pre-natal developmental toxicity maternal/developmental NOAEL of 1000 mg/kg bw/day (14). The in vivo read-across data from ESBO indicates is poorly absorbed via the dermal route (slightly irritating in the in vivo skin irritation study in rabbits (6) and non-sensitising in Guinea pig maximization test (8)). Any significant dermal absorption is unlikely.

3.3. Comparison of data from human health endpoints

3.3.1 Toxicity data of the target and source substances

There is no existing human health toxicity data for the target substance, EPO. As is presented in the data matrix (Table 3), the acute oral (LD 50 (male/female) >5,000 mg/kg bw) and acute dermal toxicity data (LD50 >20mL/kg bw) shows very low toxicity for the source chemical, ESBO, in rats and rabbits. The source chemical is slightly irritating to skin and eye in rabbits. In the in vitro bacterial reverse mutation study (Ames test), in vitro chromosomal aberration study and in vitro gene mutation study in mammalian cells, the source substance ESBO was negative in the presence and absence of metabolic activation. The source substance ESBO is not genotoxic. In a 2 year combined chronic toxicity/carcinogenicity study in rats for 104 weeks, a NOEL value of 1000 mg/kg bw/day (male) and 1400 mg/kg bw/day (female) was derived. In a pre-natal developmental toxicity study in rats, the NOAEL (maternotoxic, embryofetal) was 1000 mg/kg bw/day with no adverse effects noted. In accordance with Column 2 of ANNEX IX of the REACH Regulation, a two generation reproductive toxicity study does not need not to be conducted as the existing read across combined chronic toxicity/carcinogenicity study from ESBO is available and does not indicate clear adverse effects on reproductive organs or tissues.

The data gap for the target substance EPO is a skin sensitisation study (Annex VII, 8.3). No reliable data on skin sensitisation of EPO is available. Therefore, read-across from an existing skin sensitisation study of the source substance, ESBO, is considered as an appropriate adaptation to the standard information requirements of Annex VII, 8.3 of the REACH Regulation for the target substance, in accordance with the provisions of Annex XI, 1.5 of the REACH Regulation. The key read-across study (RL2) was conducted according to a guideline that was equivalent or similar to OECD 406. In the study, male and female adult guinea pigs ((Pirbright White); 20 animals in test group, 10 animals in control group) were induced by applications of the test substance: 0.1 % solution of ESBO in 50% propylene glycol/ 50% saline (intradermal; Weeks 1, 2 & 3). During week 6, a challenge of 0.1 % solution of ESBO in 50% propylene glycol/50% saline was administered into the skin of the left flank. Twenty-four hours after each injection during the first week of the induction period and 24 hours after the challenge injection the reactions were recorded. During week 8, a sub-irritant dose (30 % ESBO in vaseline) was applied epicutaneously under occlusive dressings which were left in place for 24 hours. The skin irritation was recorded according to Draize. After intradermal challenge, 2/20 animals in both the test and control groups were positive. After occlusive epicutaneous application, 0/20 animals in both the test and control groups were negative. ESBO was considered non-sensitising based on the results of this study. EPO is also predicted to be non sensitising in guinea pigs.

3.3.2 Effect of structural differences between target and source chemical

The target substance consists of 8 fatty acids with the largest components being C16:0 palmitic acid (44%), C18:1 oleic acid (39.2%) and C18:2 linoleic acid (10.1%). The source substance consists of 5 fatty acids with the largest components being C16:0 palmitic acid (11.3%), C18:1 oleic acid (39.2%) and C18:2 linoleic acid (55.8%). ESBO does not contain lauric, myristic and arachidic acids while they are present in very low amounts in EPO (0.2, 1.1 and 0.3% respectively). Stearic acid is present in both substances at similar levels (4.5% in EPO and 3.4% in ESBO) while α-linolenic acid is present at 0.4% in EPO and 6.4% in ESBO. So, the main component of the triglyceride structure of both EPO and ESBO is C16 (44%; 11.3%) and C18 (54.2%; 88.7%). When these epoxidized fatty acid products are released during metabolism (see Section 3.2) they are not expected to have any adverse effects in the body as all are naturally occurring fatty acids and they are all ‘Not Classified’ in the ECHA Classification and Labelling (C&L) inventory (checked 24-08-15). The only exception is α-linolenic acid which is indicated as a skin sensitizer but this is not relevant to ESBO and EPO as the former is negative in the guinea pig maximization test and EPO is also predicted to be negative also. The main structural difference is that palm oil has lower unsaturated bonds than soybean oil therefore less of the epoxidizing agent hydrogen peroxide is required to produce the epoxidized derivatives. EPO has a lower epoxidized adduct content than ESBO and is therefore expected to be less chemically reactive. The % epoxidation in ESBO is 6-8% while the % epoxidation in EPO is 2.5-3.5%.

3.3.3 Classification and labelling

According to the ECHA Classification and Labelling (C&L) inventory, the source substance, ESBO, is ‘Not Classified’ (647 notifiers, joint entry; checked 24-08-15). The target substance, EPO, is not listed in the C&L inventory (checked 24-08-15). Based on the read-across skin sensitisation presented for the source substance, EPO does not need to be classified for skin sensitisation when the criteria outlined in Annex I of 1272/2008/EC are applied.

4. Conclusion

The structural similarities between the source and the target substances and estimated similar toxicokinetics presented above support the read-across hypothesis. The structural differences between the target and source substance are not expected to have an impact on the prediction. Adequate, reliable and available scientific information indicates that using the source substance for read across to the target substance is acceptable.

Therefore, based on the considerations above, it can be concluded that the skin sensitisation study conducted in guinea pigs with ESBO is likely to predict the skin sensitisation of EPO and is considered as adequate to fulfill the information requirement of Annex VII, 8.3.

Applicant's summary and conclusion

Interpretation of results:

not sensitising

Remarks:

Migrated information

Conclusions:

Under the experimental conditions employed, no differences between the test group and the vehicle-treated controls were seen. after either intradermal or epidermal challenge application of TK 11'278. According to Directive 67/548/EEC, no classification is warranted. According to Regulation (EC) No. 1272/2008, no classification is warranted.

TK 11'278 was found to be deviod of skin-sensitising (contact allergenic) potential in albino guinea pigs.

Executive summary:

Under the experimental conditions employed, no differences between the test group and the vehicle-treated controls were seen. after either intradermal or epidermal challenge application of TK 11'278.

TK 11'278 was found to be deviod of skin-sensitising (contact allergenic) potential in albino guinea pigs. According to Directive 67/548/EEC, no classification is warranted. According to Regulation (EC) No. 1272/2008, no classification is warranted.