Palm oil, epoxidized

Skin irritation / corrosion

Administrative data

Endpoint:

skin irritation: in vivo

Type of information:

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

Adequacy of study:

key study

Study period:

10 August 1981 to 17 August 1981

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: see 'Remark'

Remarks:

[The experimental design is similar to that of OECD guideline 404 with enhanced exposure due to an extended exposure period - 24 hours - and inclusion of dermal abrasion prior to application of the test material.] 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 an in vivo skin irritation/corrosion study (Annex VIII, 8.1.1). No reliable data on in vivo skin irritation/corrosion of EPO is available. Therefore, read-across from an existing in vivo skin irritation/corrosion study of the source substance, ESBO, is considered as an appropriate adaptation to the standard information requirements of Annex VIII, 8.1.1 of the REACH Regulation for the target substance, in accordance with the provisions of Annex XI, 1.5 of the REACH Regulation.

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:

other: Proposed Guidelines of the United States Environmental Agency (EPA) S 163.81-5 "Primary dermal irritation study" Federal Register, Vol. 43, No. 163, August 22, 1978

Deviations:

yes

Remarks:

Exposure period was for 24 hours rather than 4 hours as currently required for assessment of irritation

GLP compliance:

no

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: Yellow liquid
- Lot/batch No.: Prod. Oct. 80
- Storage condition of test material: not stated
- Other:
- Solubility in water: insoluble

Test animals

Species:

rabbit

Strain:

New Zealand White

Details on test animals or test system and environmental conditions:

The test was performed on 3 male and 3 female adult New Zealand White rabbits bred and raised on the laboratory premises. They weighed 2 - 3 Kgs.

They were housed individually in metal cages numbered by ear tags.
They were kept at constant room temperature of 22 ± 2 °C, at a relative humidity of 55 ± 10 % and on a 12-hours light cycle day.
The animals received ad libitum standard rabbit food - NAFAG, No. 814, Gossau SG - and water.
Prior to treatment they were adapted to the laboratory for a minimum of 4 days.

Test system

Type of coverage:

occlusive

Preparation of test site:

other: skin was shaved. One site abraded one left unabraded

Vehicle:

unchanged (no vehicle)

Controls:

no

Amount / concentration applied:

Gauze patches of 2.5 x 2.5 cm laden with 0.5 mL of the test material were applied to the prepared abraded and intact skin.

The patches were covered with an impermeable material and were fastened to the body of the rabbit with adhesive tape.

Duration of treatment / exposure:

The dressings were removed after a 24 hour application.

Observation period:

The skin reaction was appraised using standard Draize assessment, on removal of dressing and during an observation period of 7 days.

Number of animals:

3 male and 3 female adult New Zealand White rabbits

Details on study design:

Before treatment the entire back and the flank of the rabbits were shaved with an electric clipper and immediately before treatment the shaved skin on one side was lightly sacrified using a scalpel blade.

Gauze patches of 2.5 x 2.5 cm laden with 0.5 mL of the test material were applied to the prepared abraded and intact skin. The patches were covereed with an impermeable material and were fastened to the body of the rabbit with adhesive tape.

The skin reaction was appraised on ths basis of the following evaluation scheme:

Score for skin irritation in rabbits:

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

Total possible erythema score:...................................... 4

Oedema formation
No edema: .......................................................................0
Very sllght edema (barely perceptible): ..................... 1
Sllght edema (edges of area well defined by
definite raising):............................................................. 2
Moderate edema (raised approximately 1 mm): ...... 3
Severe edema {raised more than 1 mm and
extending beyond area of exposure): ........................4

Total possible oedema score: ........................................ 4

Results and discussion

In vivo

Results

Irritation parameter:

primary dermal irritation index (PDII)

Basis:

mean

Time point:

other: 24 and 72 h post application

Max. score:

1.7

Reversibility:

fully reversible within: 7 days

Remarks on result:

other: Only limited information is provided relating to 24 and 72 scores. Reversibility is presented graphically

Irritant / corrosive response data:

The results of the primary skin irritation test are reported in Table 1.

Tha calculated primary irritation index was 2.6 - this includes results from abraded and non-abraded skin.
TK 11'278 was found to cause a moderate irritation when applied to intact and abraded rabbit skin, according to the interpretation of PII results

After 24 hours the surface of the erythema was greater than the site of application on all sites except No. 415 (intact) and No. 416 (abraded). This observation was made after 48 hours on both sites of animal No. 417 and after 72 hours on the abraded side of the same animal.

Results were revaluated to determine a possble classification in accordance with EU/GHS criteria.

In the absence of individual animal scores, taking into account the extended exposure period and assuming a linear response for ameliorating dermal responses between 24 and 72 hours, the mean results for non-abraded skin were averaged for 24 and 72 hour responses as an approximation of the Draize result. On this basis, the mean erythema score for non-abraded skin over 24-72 h was 1.5 and for oedema the mean result was 0.75.
Neiher of these values exceeds the EU classification threshold.

Other effects:

With the exception of the last day of the test, a slight sedation was observed.

Any other information on results incl. tables

Table 1       Calculation of the primary skin irritation index

Time after exposure (hours)	Mean Reaction Score
	Erythema		Oedema
	Intact Skin	Abraded Skin	Intact Skin	Abraded Skin
24	1.7	2.0	1.0	1.5
72	1.3	1.5	0.5	0.7
Total	3.0	3.5	1.5	2.2

Assessment of Irritation

0

0.1 - 1.0 = minimal

1.1 - 2.0 = slight

2.1 - 4.0 = moderate

4.1 - 6.0 = marked

6.1 - 8.0 = extreme

The scores read after 24 and 72 hours for erythema and edema for the intact as well as for the abraded skin were summed up and divided by 4. The primary irritation index was 2.6.

The abraded skin results are not appropriate for assessment under EU classification guidelines. The mean scores are 24 and 72 hours were used as approximations to the 24 -72h mean. Erythema and oedema mean scores were approximated to be 1.5 and 0.75 respectively. Neither results exceeds the EU classification threshold

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 the eye in rabbits. The source substance is not a skin sensitizer in the guinea pig maximization test. 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.

The data gap for the target substance EPO is an in vivo skin irritation/corrosion study (Annex VIII, 8.1.1). No reliable data on in vivo skin irritation/corrosion of EPO is available. Therefore, read-across from an existing in vivo skin irritation/corrosion study of the source substance, ESBO, is considered as an appropriate adaptation to the standard information requirements of Annex VIII, 8.1.1 of the REACH Regulation for the target substance, in accordance with the provisions of Annex XI, 1.5 of the REACH Regulation. The read-across in vivo skin irritation/corrosion study (RL2) was conducted according to US EPA 163.81-5 (1978). In the skin irritation/corrosion study, male and female New Zealand white rabbits (3/sex) were dermally exposed to 0.5 mL of ESBO for 24 hours to 6.25 cm2 of body surface area (abraded and intact skin). Animals then were observed for 7 days. Irritation was scored by the method of grading listed on OECD 404. ESBO was found to cause a moderate irritation when applied to intact and abraded rabbit skin. The calculated primary irritation index was 2.6, based on a combined assessment of abraded and non-abraded skin exposed for 24 hours. However, the abraded skin results are not appropriate for assessment under EU classification guidelines. The mean scores are 24 and 72 hours were used as approximations to the 24 – 72 hr mean. Erythema and oedema mean scores were approximated to be 1.5 and 0.75 respectively. Neither result exceeds the EU classification threshold. It is quite likely that the reactions observed were exacerbated by the prolonged exposure and so the estimated mean values are conservative estimates of irritating potential. In this study, ESBO is slightly irritating. The target substance, EPO, is predicted to be slightly irritating also.

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 in vivo skin irritation/corrosion study presented for the source substance, EPO does not need to be classified for skin irritation/corrosion 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 in vivo skin irritation/corrosion study conducted in rabbits with ESBO is likely to predict the in vivo skin irritation/corrosion study of EPO and is considered as adequate to fulfill the information requirement of Annex VIII, 8.1.1.

Applicant's summary and conclusion

Interpretation of results:

slightly irritating

Remarks:

Migrated information Criteria used for interpretation of results: OECD GHS

Conclusions:

Under the condition of the present experiment TK 11'278 was found to cause a moderate irritation when applied to intact and abraded rabbit skin.

The calculated primary irritation index was 2.6, based on a combined assessment of abraded and non-abraded skin exposed for 24 hours.

The abraded skin results are not appropriate for assessment under EU classification guidelines. The mean scores are 24 and 72 hours were used as approximations to the 24 -72h mean. Erythema and oedema mean scores were approximated to be 1.5 and 0.75 respectively. Neither results exceeds the EU classification threshold. It is quite likely that the reactions observed were exacerbated by the prolonged exposure and so the estimated mean values are conservative estimates of irritating potential.


According to Directive 67/548/EEC, no classification is warranted.
According to Regulation (EC) No. 1272/2008, no classification is warranted, nor according to GHS requirements.

Executive summary:

Under the condition of the present experiment TK 11'278 was found to cause a moderate irritation when applied to intact and abraded rabbit skin. The calculated primary irritation index was 2.6. The estimation of the mean score for irritation based on the 24 and 72 hour assessments was circa 1.0. According to Directive 67/548/EEC no classification is required for dermal irritation. According to Regulation (EC) No. 1272/2008, no classification is warranted.