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Toxicological information

Repeated dose toxicity: dermal

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Administrative data

Endpoint:
chronic toxicity: dermal
Remarks:
combined repeated dose and carcinogenicity
Type of information:
migrated information: read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
key study
Study period:
over a 15-year period from 1975 to after 1980.
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: This study is classified as reliable without restriction because it was carried out according to or similar to OECD TG 453.
Justification for type of information:
Concawe believes that dermal is the most relevant exposure route, and is sufficiently robust, to identify any potential hazards from repeated exposures to petroleum products to be able to adequately manage the potentially associated risks. However, the primary objective of the testing required for REACH is the identification of hazard, for which the default exposure route under the regulation is oral as this is considered to maximise systemic exposure. To address the regulatory exposure route issue, Concawe will review the current data base for evidence of systemic toxicity after dermal exposure and will also conduct a number of oral OECD 422 studies on prioritized substances in each relevant petroleum category. The document attached provides a concise overview of the information to further support the dermal route of exposure and proposed additional work, as part of a larger testing strategy (the strategy document can be found in Annex 13).

Data source

Reference
Reference Type:
publication
Title:
Evaluation of the dermal carcinogenicity of lubricant base oils by the mouse skin painting bioassay and other proposed methods
Author:
Chasey, K.L. and McKee, R.H.
Year:
1993
Bibliographic source:
Journal of Applied Toxicology 13, (1): 57-65

Materials and methods

Test guideline
Qualifier:
equivalent or similar to guideline
Guideline:
OECD Guideline 453 (Combined Chronic Toxicity / Carcinogenicity Studies)
GLP compliance:
not specified
Limit test:
no

Test material

Constituent 1
Reference substance name:
64742-55-8, 64742-54-7
IUPAC Name:
64742-55-8, 64742-54-7
Constituent 2
Reference substance name:
Hydrotreated distillates - Arab light paraffinic & South Louisiana paraffinic (Insufficiently Refined, IP 346 ≥ 3%)
IUPAC Name:
Hydrotreated distillates - Arab light paraffinic & South Louisiana paraffinic (Insufficiently Refined, IP 346 ≥ 3%)
Details on test material:
-Test substance:
Hydrotreated distillates (Arab light paraffinic, South Louisiana paraffinic)
- Substance Type: Other Lubricant Base Oils (Insufficiently Refined, IP 346 ≥ 3%)
- Distillation range: 500-1100 °F

Test animals

Species:
mouse
Sex:
male
Details on test animals or test system and environmental conditions:
TEST ANIMALS
- Source: C3H/HeJ from Jackson Laboratories, Bar Harbor, ME; C3H/HeNCrlBR from Charles River, Raleigh, NC
- Age at study initiation: 6 to 10 weeks old
- Weight at study initiation: not reported
- Fasting period before study: not reported
- Housing: singly housed or five per cage in suspended wire-mesh cages
- Diet (e.g. ad libitum): ad libitum
- Water (e.g. ad libitum): ad libitum
- Acclimation period: not reported


ENVIRONMENTAL CONDITIONS
- Temperature (°C): not reported
- Humidity (%): not reported
- Air changes (per hr): not reported
- Photoperiod (hrs dark / hrs light): not reported


IN-LIFE DATES: various

Administration / exposure

Type of coverage:
open
Vehicle:
not specified
Details on exposure:
TEST SITE
- Area of exposure: intrascapular area
- % coverage: not reported; dermal treatment area was approximately 5.25 cm2 (3.5 x 1.5 cm)
- Type of wrap if used: not reported
- Time intervals for shavings or clippings: clipped once weekly

REMOVAL OF TEST SUBSTANCE
- Washing (if done): not reported
- Time after start of exposure: not reported


TEST MATERIAL
- Amounts applied (volume or weight with unit): 37.5 μl aliquots twice per week or 25 μl aliquots three times per week.
- Concentration (if solution): not reported
- Constant volume or concentration used: no

USE OF RESTRAINERS FOR PREVENTING INGESTION: not reported
Analytical verification of doses or concentrations:
not specified
Details on analytical verification of doses or concentrations:
No data reported.
Duration of treatment / exposure:
24 months or lifetime
Frequency of treatment:
Twice per week or three times per week
Doses / concentrations
Remarks:
Doses / Concentrations:
25 μL aliquots three times per week or 37.5 μL aliquots twice per week (100 mg/kg/day)
Basis:

No. of animals per sex per dose:
No data reported.
Control animals:
yes
Details on study design:
No data reported.
Positive control:
Each set of studies included positive and negative control groups. Highly refined mineral oils were always used as the negative control materials. Some studies also included animals that were completely untreated or were shaved but had no material administered. The incidence of skin tumours within the negative control groups was extremely low. On occasion, a single animal in the negative control group developed a papilloma. No negative control group ever contained more than one tumour-bearing animal, and only benign tumours were produced. In the initial studies, a high boiling-point aromatic oil from a catalytic cracking unit was used as a positive control. This material contained a high concentration of carcinogenic PACs and was quite active in dermal carcinogenesis bioassays. In later studies, benzo[a]pyrene was also used. In all instances, the positive controls responded as expected. The control information is omitted for the sake of brevity.

Examinations

Observations and examinations performed and frequency:
Animals were examined twice weekly for the appearance of dermal tumours. Each tumour in the treatment area was examined carefully and classified grossly. All grossly diagnosed tumours were examined microscopically after study termination.
Sacrifice and pathology:
A complete necropsy was performed on each mouse. All body cavities were examined and all abnormal tissues were fixed in 10% neutral-buffered formalin. Organs and tissues that were examined grossly included liver, lung, kidneys, heart, adrenals, spleen, gallbladder, stomach, pancreas, caecum, urinary bladder, testes, seminal vesicles and lymph nodes. Tissues that were preserved for microscopic examination included dorsal skin from the treatment areas and coetaneous masses. In early studies, a complete pathological investigation of visceral organs was conducted. However, in later studies, visceral organs were only examined microscopically if grossly diagnosed tumours were present.
Other examinations:
No data reported.
Statistics:
The Weibull distribution function was used to estimate the median tumour latencies. The observational parameter that formed the basis for the median latency estimates was the time to onset of the first squamous cell tumour (either benign or malignant) for each animal. Statistical evaluation was limited to squamous cell carcinomas, squamous cell papillomas, and keratoacanthomas that arose at the site of test material application. Mortality rates were assessed by the product limit method. Tumour yields were compared by Fisher's exact test.

Results and discussion

Results of examinations

Clinical signs:
not specified
Dermal irritation:
not specified
Mortality:
not specified
Body weight and weight changes:
not examined
Food consumption and compound intake (if feeding study):
not examined
Food efficiency:
not examined
Water consumption and compound intake (if drinking water study):
not examined
Ophthalmological findings:
not examined
Haematological findings:
not examined
Clinical biochemistry findings:
not examined
Urinalysis findings:
not examined
Behaviour (functional findings):
not examined
Organ weight findings including organ / body weight ratios:
not examined
Gross pathological findings:
not examined
Histopathological findings: non-neoplastic:
not examined
Histopathological findings: neoplastic:
effects observed, treatment-related
Details on results:
No detailed data reported.

Effect levels

Dose descriptor:
LOAEL
Effect level:
100 mg/kg bw/day
Sex:
male
Basis for effect level:
other: Based on incidence of tumours.

Target system / organ toxicity

Critical effects observed:
not specified

Any other information on results incl. tables

Of the 94 samples tested for carcinogenic activity, 57 produced no tumour-bearing animals and the remaining 37 produced one or more. Among the groups containing tumour-bearing animals, seven had one, six had two, two had four and the remaining 22 had five or more. Responses are statistically significant in 22 of the 37 groups containing tumour-bearing animals. When the results are examined by processing history classification, all raw vacuum distillates (6/6), raw extracts (7/7) and hydrotreated extracts (6/6) produced tumours. Among the remaining classifications, most extracted distillates (19/21), extracted and hydrotreated distillates (33/37) and refined vacuum residua (2/2) produced fewer than two tumour-bearing animals per group. The hydrotreated distillates produced a mixed response.

 

A summary table of the samples tested is given below:

Table 1. Biological and analytical test results for Exxon database.

Sample Description

Bioassay Results

Analytical measurements

Classification by processing history

Crude oil feedstock^

Identification Number

Tumour response*

Median latency**

Mutagenicity index***

IP 346/80#

FDA 178.3620(b)##

Extracted and

VN

41

0/40

-

-

-

-

hydrotreated distillate

ALP

42

0/40

-

-

0.87

83

 

ALP/NSP

71

16/40

95

4.1

4.17

913

 

ALP/NSP

72

2/40

139

5

3.56

668

Hydrotreated distillate

ALP

78

7/40

118

6.3

-

-

 

ALP

79

12/40

91

< 1.0

7.39

-

 

ALP

80

0/40

-

-

3.29

-

 

ALP

82

7/50

107

5

7.07

-

 

SLP

83

20/50

93

2.4

3.81

1112

 

ALP/NSP

84

0/40

-

-

-

1188

 

ALP/NSP

85

0/40

-

-

-

599

 

ALP/NSP

86

0/40

-

2

3.01

708

^ AHP, Arab heavy paraffinic; ALP, Arab light paraffinic; GCN, Gulf Coast naphthenic; MP, mixed paraffinic; NSP, North Sea paraffinic; SLP, South Louisiana paraffinic; VN, Venezuelan naphthenic; WCP, West Canadian paraffinic; WTP, West Texas paraffinic.

*Listed is the number of animals with squamous cell tumours in the treatment area over the number of animals in the original test group. Samples producing two or more tumour-bearing animals were classified as carcinogenic.

**The median time to tumour, in weeks, as estimated by the Wiebull distribution function.

***The slope of the dose-response curve for mutagenesis. Samples producing mutagenic indices of ≥2.0 were classified as mutagenic.

# The weight percentage of the DMSO extractables, as determined by the IP346/80procedure. A weight percentage of ≥3.0 was considered to be positive.

## The ultraviolet absorbance at 280 nm of the DMSO extractables, as determined by the FDA 178.3620(b) procedure. An ultraviolet absorbance at 280 nm of ≥600 was considered to be positive.

Applicant's summary and conclusion

Conclusions:
The results demonstrate the influence of refining severity in controlling carcinogenicity. Most extracted distillates (19 out of 21), and extracted and hydrotreated distillates (33 out of 37), produced fewer than two tumour-bearing animals per test group.  Hydrotreatment alone produced a mixed response.
Executive summary:

Read across justification

No dermal repeated dose studies have been reported for petrolatum (carcinogenic or unknown feed-stock), but data have been reported for other lubricant base oils (IP 346 ≥3 wt%), materials similar to the oil entrained in petrolatum (carcinogenic or unknown feed-stock).

In these studies, male C3H mice, approximately 6 to 10 weeks of age were obtained from Jackson Laboratories (C3H / HeJ) or, (C3H / HeNCrlBR).  These mice were randomly distributed into test groups of 40 or 50 animals.  In early studies, mice were housed five per cage in suspended wire-mesh cages.  In later studies, they were housed singly in the same type of cages.  The hair in the interscapular area was clipped once weekly to facilitate test material application.  The test materials were applied by automatic pipette in either 37.5 μL aliquots twice a week or 25 µL aliquots three times a week.  All test materials were applied undiluted. In early studies, the treatment continued until the animals died spontaneously or were sacrificed in a moribund state.  In later studies, surviving mice were sacrificed after either 24 months of treatment or at the time at which grossly diagnosed squamous cell carcinomas developed.  Animals were examined twice weekly for the appearance of dermal tumours.  Each tumour in the treatment area was examined carefully and classified grossly.  All grossly diagnosed tumours were examined microscopically after study termination. The two largest subsets of the database are the solvent extracted oils (i.e., 21 oils) and the solvent extracted and hydrotreated oils (i.e., 37 oils).  The data for these subsets were highlighted due to the importance of solvent extraction in many lubricant base oil manufacturing schemes.  All commercial products refined in this way produced negative bioassays.  The solvent extracted oils that produced tumours were refined by experimental conditions that are not representative of those used in commercial refineries.

The LOAEL was determined to be 100 mg/kg/day based on the incidence of tumours observed.

This study is classified as reliable without restriction because it was carried out according to or similar to OECD TG 453.

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