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Toxicological information

Acute Toxicity: dermal

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Administrative data

Endpoint:
acute toxicity: dermal
Type of information:
migrated information: read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
key study
Study period:
Not stated
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: see 'Remark'
Remarks:
[Study conducted prior to introduction of test guidelines or adoption of GLP, however he testin laboratory is reputable and the study design appears to follow methods similar to those adopted subsequently as international standards] 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 acute dermal toxicity study (Annex VIII, 8.5.3). No reliable data on acute dermal toxicity of EPO is available. Therefore, read-across from existing acute dermal toxicity studies of the source substance, ESBO, is considered as an appropriate adaptation to the standard information requirements of Annex VIII 8.5.3 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:
1955
Report date:
1955

Materials and methods

Test guideline
Qualifier:
no guideline available
Principles of method if other than guideline:
Similar to OECD Guideline 402 or EC Method 403 but as a rangefinding test fewer rabbits used than recommended in formal guidelines adopted many years after study conduct.
GLP compliance:
no
Test type:
standard acute method
Limit test:
yes

Test material

Constituent 1
Reference substance name:
Soybean Oil Epoxide
IUPAC Name:
Soybean Oil Epoxide
Details on test material:
Liquid. Used undiluted. A pint of material was supplied from Run No.4, code 272, R.D. 82 on 19 August 1955.

Test animals

Species:
rabbit
Strain:
New Zealand White
Sex:
male
Details on test animals or test system and environmental conditions:
TEST ANIMALS
- Source: No data
- Age at study initiation: 3-5 months old
- Weight at study initiation: mean weight 2.5 kg
- Fasting period before study: No
- Housing: No data
- Diet (e.g. ad libitum): Rockland rabbit ration
- Water (e.g. ad libitum): No data
- Acclimation period: No data

ENVIRONMENTAL CONDITIONS
- Temperature (°C): No data
- Humidity (%): No data
- Air changes (per hr): No data
- Photoperiod (hrs dark / hrs light): No data

IN-LIFE DATES: From:No details provided To: No details provided

Administration / exposure

Type of coverage:
occlusive
Vehicle:
unchanged (no vehicle)
Details on dermal exposure:
TEST SITE
- Area of exposure: No data
- % coverage: No data
- Type of wrap if used: Impervious 'Vinylite' sheeting

REMOVAL OF TEST SUBSTANCE
- Washing (if done): No data
- Time after start of exposure: Exposure period was 24 hours

TEST MATERIAL
- Amount(s) applied (volume or weight with unit): 20 ml/kg bw applied undiluted
- Concentration (if solution): undiluted
- Constant volume or concentration used: yes
Duration of exposure:
24 hour occluded exposure
Doses:
20 ml/kg bw
No. of animals per sex per dose:
NOt stated, but report wording suggests only four rabbits were treated
Control animals:
not specified
Details on study design:
No further details available
Statistics:
Thompson's method for calculating median lethal doses, used where appropriate

Results and discussion

Preliminary study:
No data
Effect levels
Sex:
male
Dose descriptor:
LD50
Effect level:
> 20 mL/kg bw
Based on:
test mat.
Mortality:
Four rabbits survived treatment at 20 ml/kg bw. It appears that only four rabbits were treated and therefore there were no mortalities.
Clinical signs:
other: No data
Gross pathology:
No data
Other findings:
Topical application of 20 ml/kg bw to rabbit skin under fully occluded conditions for 24 hours, resulted in no deaths. All four treated rabbits survived 24 h treatment and the 13 day observation period

Any other information on results incl. tables

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 toxicity data (LD50 >5000 mg/kg bw) shows very low toxicity for the source chemical, ESBO, in rats. The source chemical is slightly irritating to skin and 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 acute dermal toxicity study (Annex VIII, 8.5.3). No reliable data on acute dermal toxicity of EPO is available. Therefore, read-across from existing acute dermal toxicity studies of the source substance, ESBO, is considered as an appropriate adaptation to the standard information requirements of Annex VIII 8.5.3 of the REACH Regulation for the target substance, in accordance with the provisions of Annex XI, 1.5 of the REACH Regulation.

Two read-across acute dermal toxicity studies are available. The key read-across study (RL2) was conducted according to a guideline equivalent or similar to OECD 402. In this study, groups of young male New Zealand rabbits (4/sex) were dermally exposed (occlusive) to ESBO (undiluted) for 24 hours at a dose of 20 mL/kg bw. Animals then were observed for 13 days. There were no mortalities and no evidence of dermal toxicity in the 4 rabbits treated. The dermal LD50 (males) for ESBO was >20 mL/kg bw. The dermal LD50 (males) for EPO is also predicted to be >20 mL/kg bw.

The supporting read-across study (RL2) was conducted according to a guideline equivalent or similar to OECD 402. In this study, groups of rabbits were dermally exposed to ESBO at a dose of 20 mL/kg bw. The dermal LD50 for ESBO was >20 mL/kg bw. The dermal LD50 for EPO is also predicted to be >20 mL/kg bw.

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 acute oral and dermal toxicity studies presented for the source substance, EPO does not need to be classified for acute toxicity or STOT-SE 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 acute dermal toxicity study conducted in rats with ESBO is likely to predict the acute dermal toxicity of EPO and is considered as adequate to fulfill the information requirement of Annex VII, 8.5.1.

The data matrix is in Section 5 of the full report attached in the study summary.

Applicant's summary and conclusion

Interpretation of results:
practically nontoxic
Remarks:
Migrated information Criteria used for interpretation of results: EU
Conclusions:
24 hour exposure to undiluted ESBO under fully occluded conditions did not result in signs of reaction to treatment, mortality or evidence of dermal toxicity in the four rabbits tested.
Executive summary:

24 hour exposure to undiluted ESBO under fully occluded conditions did not result in signs of reaction to treatment, mortality or evidence of dermal toxicity in the four rabbits tested.