Naphthenic acids

Endpoint summary

Description of key information

For acute oral toxicity no key study could be put forward. Instead the available studies were considered in a Weight of Evidence approach, all resulting in LD50 values above limit dose (3.0 - 5.88 g/kg bw). From the  available studies the most detailed study was kept as for the chemical safety assessment. 
For acute dermal toxicity the LD50 was obtained from 2 studies, both showing LD50 values above limit dose (3.16 & 20.0 g/kg bw).The study with the lowest values was considered as Key study and the other served as supporting study. 
The endpoint acute inhalation toxicity has been waived based on the very low vapour pressure of the substance. Inhalation exposure is very unlikely under normal handling and use.

Key value for chemical safety assessment

Acute toxicity: via oral route

Link to relevant study records

Reference

Endpoint:

acute toxicity: oral

Type of information:

experimental study

Adequacy of study:

weight of evidence

Reliability:

4 (not assignable)

Rationale for reliability incl. deficiencies:

other: see 'Remark'

Remarks:

This study is reported in a 'Reclamed Substances Testplan' for Naphthenic acids in the frame of the High Production Volume Chemical Challende Program of US EPA and hence considered as secondary literature. Because no access to the original report was obtained a Klimisch score 4 for reliability has been assigned. However, this study has been evaluated by the American Petroleum Institute (API) and was found to be reliable without restriction. The following conclusion was drawn by the API: 'it appeared to be comparable to a guideline study with adequate experimental details provided. Although the investigators used male rats only, there is sufficient experimental detail to make a conclusion on the study's validity, and the results can be used to assess the potential acute toxicity of naphthenic acid.'

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 401 (Acute Oral Toxicity)

Deviations:

not specified

Principles of method if other than guideline:

Male rats only

GLP compliance:

not specified

Test type:

standard acute method

Limit test:

no

Species:

rat

Strain:

Wistar

Sex:

male

Route of administration:

oral: unspecified

Vehicle:

unchanged (no vehicle)

Doses:

Rats were dosed at 1.0, 1.47, 2.15, 3.16, 4.64, 6.81 and 10 g/kg of body weights.

No. of animals per sex per dose:

Seven groups of 5 male rats

Control animals:

not specified

Details on study design:

- Duration of observation period following administration: 14 days
- Frequency of observations and weighing: The rats were observed 1, 2, 4 and 6 hours ,after dosing and once daily for 14 days. Mortality, toxicity and pharmacological effects were recorded. Body weights were recorded pretest and in the survivors at 14 days.
- Necropsy of survivors performed: yes
All animals were examined for gross pathology

Sex:

male

Dose descriptor:

LD50

Effect level:

5 880 mg/kg bw

Based on:

test mat.

95% CL:

>= 4.31 - <= 8.02

Mortality:

Deaths occurred at the four highest dose levels: 3.26, 4.64, 6.81 and 10 g/kg bw. 8/10 animals died at the two highest dose levels.

Clinical signs:

other: Significant predeath toxic signs included tremors, lethargy, ptosis, ataxia, prostration, negative righting reflex, flaccid muscle tone, piloerection, diarrhea, chromodacryorrhea. dyspnea and chromorhinorrhea. Body weight changes were noted in the survivo

Gross pathology:

Significant necropsy findings in the animals that died during the study included dilated hearts and gastrointestinal irregularities.

Interpretation of results:

GHS criteria not met

Conclusions:

The LD50 was determined to be 5.88 (4.31-8.02) g/kg bw

Executive summary:

Seven groups of 5 male rats were dosed at 1.0, 1.47, 2.15, 3.16, 4.64, 6.81, and 10 g/kg of body weights. Mortality, toxicity and pharmacological effects were recorded. Body weights were recorded pretest and in the survivors at 14 days. At 14 days the survivors were sacrificed. All animals were examined for gross pathology.

Deaths occurred at the four highest dose levels: 3.26, 4.64, 6.81, and 10 g/kg bw. 8/10 animals died at the two highest dose levels. Significant predeath toxic signs included tremors, lethargy, ptosis, ataxia, prostration, negative righting reflex, flaccid muscle tone, piloerection, diarrhea, chromodacryorrhea, dyspnea and chromorhinorrhea. Body weight changes were noted in the survivors. Significant necropsy findings in the animals that died during the study included dilated hearts and gastrointestinal irregularities.

The LD50 was determined to be 5.88 (4.31-8.02) g/kg bw.

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed

Dose descriptor:

LD50

Value:

5 880 mg/kg bw

Quality of whole database:

Klimisch value of the studies varied from 3-4. All information was based on published data, including secondary sources; therefore details were missing. On the other hand, LD50 values were consistently higher than 2000 mg/kg bw.

Acute toxicity: via inhalation route

Endpoint conclusion

Endpoint conclusion:

no study available

Acute toxicity: via dermal route

Link to relevant study records

Reference

Endpoint:

acute toxicity: dermal

Type of information:

experimental study

Adequacy of study:

key study

Study period:

1979

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Although no indication that it is a GLP study, the availeble robust study summary published in the "robust study information on reclaimed substances: Naphthenic acid" by the API sufficient detail is provided to make a conclusion about its validity.

Reason / purpose for cross-reference:

reference to same study

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 402 (Acute Dermal Toxicity)

Deviations:

yes

Remarks:

This study is a combined study where Accute Dermal Toxicity is considered together with skin irritation.

Principles of method if other than guideline:

This study is a combined study where Accute Dermal Toxicity is considered together with skin irritation.

GLP compliance:

not specified

Test type:

standard acute method

Limit test:

yes

Species:

rabbit

Strain:

New Zealand White

Sex:

male/female

Type of coverage:

occlusive

Vehicle:

unchanged (no vehicle)

Details on dermal exposure:

3.16 g/kg naphthenic acid was applied dermally to the clipped abraded abdomens of each animal. The area was covered with gauze and secured by a thick plastic binder, which was removed atfter 24 hours, and the skin washed with water or corn oil.

Duration of exposure:

24 hours

Doses:

3.16 g/kg naphthenic acid was applied dermally to the clipped abraded abdomens of each animal

No. of animals per sex per dose:

2 per sex

Control animals:

not specified

Details on study design:

According to experimental protocol, if no deaths occurred at the initial level, no addition animals were dosed. If one animal died, the experiment was to be repeated using 3 more groups of animals dosed at varying levels.
Following the skin wash, animals were observed for mortality and toxic effects at 2 hr and 4 hr, and once daily thereatter. Body weights were recorded pretest and at termination. Dermal irritation was recorded at 24 hr, 3, 7, 10 and 14 days.
The rabbits were observed 1, 2, 4 and 6 hours after dosing and once daily for 14 days. Mortality, toxicity and pharmacological effects were recorded. Body weights were recorded pretest and in the survivors at 14 days. At 14 days the survivors were sacrificed. Ananimals were examined for gross pathology.

Sex:

male/female

Dose descriptor:

approximate LD50

Effect level:

> 3 160 mg/kg bw

Based on:

test mat.

Mortality:

no

Clinical signs:

other: lethargy, diarrhea, ptosis, adipsia, anorexia, and few feces

Gross pathology:

No

Other findings:

No deaths occurred at the 3.16 mg/kg dose level. Most of the animals (3/4) appeared normal during the first 2 to 4 hours of dosing, after which symptoms of toxicity were observed. 3 out of 4 animals (1 male, 2 female) showed signs of toxicity until day 12 or 13. During the first 5 days, all animals displayed one or more of the following symptoms: lethargy, diarrhea, ptosis, adipsia, anorexia, and few feces.
The LD50 was determined to be greater than 3.16 g/kg bw
Redness and irritation scores were recorded at 24 hr, 3, 7, 10 and 14 days post-washing. 4 Hour occluded sites (DOT, OECD methods)
Mean values (24, 48 & 72 hours) for erythema and edema at the intact sites were 1.69 and 1.3 respectively. The initial response of the skin to the test material was slight, with little difference in response between intact or abraded sites.

Interpretation of results:

GHS criteria not met

Executive summary:

New Zealand white rabbits were dermally treated with 3.16 g/kg Naphthenic acids under occlusive dressing for 24 hours, afeter which the skin was washed with water or corn oil. The rabbits were observed 1, 2, 4 and 6 hours after dosing and once daily for 14 days. No deaths occurred at the 3.16 mg/kg dose level. Most of the animals (3/4) appeared normal during the first 2 to 4 hours of dosing, after which symptoms of toxicity were observed. 3 out of 4 animals (1 male, 2 female) showed signs of toxicity until day 12 or 13. During the first 5 days, all animals displayed one or more of the following symptoms: lethargy, diarrhea, ptosis, adipsia, anorexia, and few feces.

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed

Dose descriptor:

LD50

Value:

3 160 mg/kg bw

Quality of whole database:

High quality study

Additional information

Acute oral toxicity was obtained from various studies, that were considered as Weight of Evidence information. There were various studies with limited to moderate information, however all providing consistent LD50 values:

- LD50 = 5.88 g/kg bw in male rats; male rats were dosed from 1 to 10 g/kg of body weights (HPVIS, 2003; Exxon, 1979). Deaths occurred at the four highest dose levels of 3.26, 4.64, 6.81, and 10 g/kg bw. 8/10 animals died at the two highest dose levels. Significant predeath toxic signs included tremors, lethargy, ptosis, ataxia, prostration, negative righting reflex, flaccid muscle tone, piloerection, diarrhea, chromodacryorrhea, dyspnea and chromorhinorrhea. Body weight changes were noted in the survivors. Necropsy findings in the animals that died during the study included dilated hearts and gastrointestinal irregularities.

- LD50 = 3.0 -5.2 g/kg bw in rats; this was based on fraction from crude kerosene acids and a fraction from mixed crude oils, respectively (Rockhold, 1955) . Death appeared to result from gastrointestinal disturbances, with the mortality peak occurring on the third to fourth day after administration. The animals exhibited anorexia, inanition, diarrhea, and asthenia.

- LD50 = 3.55 g/kg bw in mice (HPVIS, 2003; Penissi & Lynch, 1977). Clinical observations included CNS depression, corneal eye opacity,dryness of mouth, convulsions, diarrhea, and death due to respiratory arrest

- Finally acute oral toxicity testing was performed in Wistar rats with a mixture of naphthenic acids isolated from Althabasca oils sand (AOS). Single dosages of 3, 30 and 300 mg/kg bw were given to female rats and 300 mg/kg bw was given to male rats by oral gavage. Food consumption was temporarily suppressed in the high dose groups of both sexes. Histopathology 14 days after dosing revealed a significant incidence of pericholangitis in the high dose group of both sexes, suggesting hepatotoxicity as an acute effect. Other histological lesions included brain haemorrhage in the high dosed males, and cardiac perioarteriolar necrosis and fibrosis in female rats. *

Acute inhalation toxicity testing was waived according 8.5.2 column 2 of Annex VIII: Vapour pressure of Naphthenic acids is very low (<0.001 Pa at 25°C), thus inhalation of vapors is considered to be improbable and aerosols are not expected to be formed with standard uses.

Acute dermal toxicity was studied after 24 hours occlusive dressing in 2 studies in New Zealand rabbits:

- LD50 >3.16 g/kg (HPVIS, 2003; Exxon, 1979). No deaths occurred at the 3.16 mg/kg dose level and most of the animals (3/4) appeared normal during the first 2 to 4 hours of dosing, after which symptoms of toxicity were observed, e.g. lethargy, diarrhea, ptosis, adipsia, anorexia, and few feces.

- LD50> 20 g/kg bw (Auletta, 1979). Ataxia and motor activity decrease were evident throughout the fourteen day observation period; from Day 2 through Day 14 of the study these signs were noted at least once in all animals; abdominal griping and soft stool were noted in a few animals and oral, ocular and nasal discharge, alopecia, aggressiveness and fecal staining of the abdomen were noted sporadically in one or two animals.

* The oil sands extracts used in testing described in Rogers et al. (2002) was composed of a greater proportion of higher molecular weight naphthenic acid isomers than the registered sample. Three and four ring constituents comprised 38% of their test sample whereas they totalled 7% of the registered (and HPV) substance. The higher molecular weight naphthenic acid constituents in the oil sands extracts may have implications to the interpretation of effects. Rogers drew attention to the fact that the material he had isolated from oil sands had properties that differed from those of commercial materials that he was using for standards. In fact, there were differences in toxic properties and possible contaminants present in the samples of Rogers or methodological differences which were not representative for the commercial products, so the extent to which these are due to differences in the test protocols is not known (EPA, 2012; see attachment).

Justification for classification or non-classification

Available data suggest values for acute oral and dermal toxicity that warrant no classification for acute toxicity under Regulation 1272/2008 (CLP) nor under Directive 67/548/EC (DSD).