Naphthenic acids, zinc salts, basic

Endpoint summary

Description of key information

No repeated dose toxicity study with naphthenic acids, zinc salts, basic is available. Thus, read-across to naphthenic acids, zinc salts is applied. In a relevant and reliable 2 -generation reproductive toxicity study, rats were exposed to 500, 1000 and 5000 ppm naphthenic acids, zinc salts via the diet. Parental animals of the high dose group showed body weight depression while food consumption was comparable to those of control animals. Thus, the NOAEL for systemic toxicity was set at 1000 ppm (equal to 50 mg/kg bw/day) based on effects on body weight.

There were no toxicological findings reported that would justify a classification for specific target organ toxicity with repeated exposure. Hence, no classification for naphthenic acids, zinc salts, basic as STOT RE via the oral route is required.

Key value for chemical safety assessment

Repeated dose toxicity: via oral route - systemic effects

Link to relevant study records

Reference

Reference 1

Endpoint:

sub-chronic toxicity: oral

Type of information:

experimental study

Adequacy of study:

key study

Study period:

January 1987 - February 1988

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

comparable to guideline study

Reason / purpose for cross-reference:

reference to same study

Qualifier:

no guideline followed

Principles of method if other than guideline:

30 male and 30 female Sprague-Dawley rats per group and generation (P and F1) were treated with zinc naphthenate. The dosage groups were as follows: 0, 500, 1000 and 5000 ppm in the diet. The vehicle was corn oil. In addition, a vehicle control group was also tested. The animals were treated 10 weeks prior to mating (males/females), during mating (males/females), gestation (females) and lactation (females).

GLP compliance:

yes

Remarks:

US-GLP (Title 40, Code of Federal Regulations, 1985 rev., Part 160, Good Laboratory Practice Standards

Limit test:

no

Species:

rat

Strain:

Sprague-Dawley

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS - Sprague Dawley COBS, CD rats
- Source: Charles River Laboratories of Wilmington, Massachusetts.
- Age at study initiation: 7 weeks of age
- Housing: animals were kept three per cage,
- Diet (ad libitum): certified rodent ration (Zeigler Bros., Inc., Gardners, Pennsylvania). The ration arrived in the form of lab block and was ground to a uniform consistency.
- Water (ad libitum): water
- Quarantine period: a 2-week quarantine; Body weights and feed consumption were monitored during this pretreatment period.

ENVIRONMENTAL CONDITIONS
- Temperature: 21.1°C (18.3 - 23.9°C)
- Relative humidity: 50% (40% - 60%)
- Photoperiod (hrs dark / hrs light): 12/12

Route of administration:

oral: feed

Vehicle:

corn oil

Remarks:

Mazola

Details on oral exposure:

DIET PREPARATION
Feed was prepared on a weekly basis by dissolving the appropriate amount of zinc naphthenate in corn oil with the aid of heat, while keeping the total volume of corn oil/zinc naphthenate for each dosage group constant. These solutions were, in turn, poured into ground rodent ration and thoroughly blended with a mechanical mixer.

Analytical verification of doses or concentrations:

yes

Details on analytical verification of doses or concentrations:

To ensure homogeneity and accuracy of the preparation, samples were extracted from each batch of feed and analysed for zinc content by atomic absorption.
Compound concentration in feed remained at a constant level throughout the entire study with no attempts to adjust for body weight gains.

Duration of treatment / exposure:

1) P generation:
Males:
- 10 weeks prior to mating
- throughout mating until necropsy
Females:
- 10 weeks prior to mating
- throughout mating, gestation and lactation

2) F1 generation:
Males:
- 10 weeks prior to mating starting after weaning
- throughout mating until necropsy
Females:
- 10 weeks prior to mating
- throughout mating, gestation and lactation

Frequency of treatment:

ad libitum

Remarks:

Doses / Concentrations:
500ppm (= 25mg/kg bw/day)
Basis:
nominal in diet

Remarks:

Doses / Concentrations:
1000ppm(= 50mg/kg bw/day)
Basis:
nominal in diet

Remarks:

Doses / Concentrations:
5000ppm(= 250mg/kg bw/day)
Basis:
nominal in diet

No. of animals per sex per dose:

P generation: 30 males / 30 females
F1 generation: 30 males / 30 females

Control animals:

yes, concurrent vehicle

Details on study design:

PILOT STUDY
The dosages of zinc naphthenate in the main study were based on the previously conducted pilot study which indicated effects between 2,700 ppm and 5,000 ppm in both parental sexes and their offspring.
The pilot study is described as follows:
A pilot study was conducted using 72 Sprague Dawley COBS, CD rats (six groups, each of six male and six female). Dosages for the study were calculated on a percent diet basis and were derived from expected food consumption and toxic signs seen in the acute oral studies. The concentration of zinc naphthenate in the feed ranged from 0.13 percent (1,300 ppm) in the low dosage group to 2.10 percent (21,000 ppm) in the high dosage group.

Results:
Male and female rats receiving 1 and 2 percent zinc naphthenate in their diet (10,000 ppm and 20,000 ppm) showed reduced body weights following 4 weeks of compound administration. Both sexes of rats in these groups also became lethargic and experienced urogenital staining from compound
consumption. Mating of rats within their respective groups indicated the 2 percent zinc naphthenate group required twice the mating time as did the other five dosage groups. Litters born of the highest two dosage groups (one and two percent) experienced reduced birth numbers and reduced total birth weights. At the time of weaning, offspring numbers and weights for these high dosage group litters were greatly reduced when compared to
litters of lower dosage groups and controls.

Positive control:

not stated

Observations and examinations performed and frequency:

1) P GENERATION

CAGE SIDE OBSERVATIONS: Yes
- Time schedule: animals were checked daily for toxic signs during the 10 weeks before mating.

DETAILED CLINICAL OBSERVATIONS: No

BODY WEIGHT: Yes
- Time schedule for examinations: body weights were recorded three times per week during the 10 weeks before mating.

FOOD CONSUMPTION AND COMPOUND INTAKE (if feeding study):
- Food consumption for each animal determined and mean daily diet consumption calculated as g food/kg body weight/day: Yes
- Compound intake calculated as time-weighted averages from the consumption and body weight gain data: No

FOOD EFFICIENCY:
- Body weight gain in kg/food consumption in kg per unit time X 100 calculated as time-weighted averages from the consumption and body weight gain data: No

WATER CONSUMPTION AND COMPOUND INTAKE (if drinking water study): No
OPHTHALMOSCOPIC EXAMINATION: No
HAEMATOLOGY: No
CLINICAL CHEMISTRY: No
URINALYSIS: No
NEUROBEHAVIOURAL EXAMINATION: No


2) F1 GENERATION

CAGE SIDE OBSERVATIONS: Yes
- Time schedule: daily during the 10 week exposure period prior to mating.

DETAILED CLINICAL OBSERVATIONS: No

BODY WEIGHT: Yes
- Time schedule for examinations: three times a week during the 10 week exposure period prior to mating

FOOD CONSUMPTION AND COMPOUND INTAKE (if feeding study):
- Food consumption for each animal determined and mean daily diet consumption calculated as g food/kg body weight/day: Yes
- Compound intake calculated as time-weighted averages from the consumption and body weight gain data: No data

FOOD EFFICIENCY:
- Body weight gain in kg/food consumption in kg per unit time X 100 calculated as time-weighted averages from the consumption and body weight gain data: No
WATER CONSUMPTION AND COMPOUND INTAKE (if drinking water study): No
OPHTHALMOSCOPIC EXAMINATION: No
HAEMATOLOGY: No
CLINICAL CHEMISTRY: No
URINALYSIS: No
NEUROBEHAVIOURAL EXAMINATION: No

Sacrifice and pathology:

1) P GENERATION

GROSS PATHOLOGY: Yes
HISTOPATHOLOGY: Yes
- Male animals: animals were euthanized by CO2, examined grossly, and tissues removed (testes, epididymides, seminal vesicles, prostate, pituitary, liver, kidneys), for histopathologic examination
- Maternal animals: the dams were sacrificed by CO2 at the time of weaning of the F1 generation. All dams were examined grossly while the vagina, uterus, ovaries, pituitary gland, liver, and kidneys were removed for histopathologic examination.

2) F1 GENERATION
- Male animals: following the 3-week mating period, F1 males were necropsied, taking sex and target organs for histopathologic examination.
- Maternal animals: F1 dams had organs taken for histopathologic examination.

In addition to the periodic sacrifices mentioned above, any animal dying spontaneously or for some reason removed from the study at an early date was submitted for gross necropsy. Gross necropsies consisted of the examination of all external surfaces, orifices, brain and spinal cord, thoracic, abdominal and pelvic cavities, and organs therein.

Clinical signs:

effects observed, treatment-related

Mortality:

mortality observed, treatment-related

Body weight and weight changes:

effects observed, treatment-related

Food consumption and compound intake (if feeding study):

no effects observed

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 specified

Histopathological findings: non-neoplastic:

effects observed, treatment-related

Histopathological findings: neoplastic:

no effects observed

Details on results:

1) P GENERATION

CLINICAL SIGNS AND MORTALITY
Male rats in the 0.5 percent dosage group appeared to become lethargic after week 9 of the dosing period. Alopecia was prevalent in the mid- and high-dosage animals of both sexes.
One male rat from the 0.1 percent dosage group was found cannibalised while the rats were group housed, prior to mating. Fighting was the apparent cause of death.

BODY WEIGHT AND WEIGHT GAIN
The P generation female rats in the 0.5 percent group (5000 ppm) experienced significantly reduced body weights by week 3 of compound administration, and continued through week 10. The control, low, and mid-dosage groups gained at similar rates.
Male rats fed a diet of 5000 ppm zinc naphthenate demonstrated significantly decreased body weights by week 8 of the 10 week dosing period.

FOOD CONSUMPTION AND COMPOUND INTAKE (if feeding study)
Weekly monitoring of feed consumption during the 10 week exposure period indicated all female rats ate similar portions, regardless of the dosage group. The same was also true for male rats, regardless of the zinc naphthenate concentration in the feed.

HISTOPATHOLOGY: NON-NEOPLASTIC
Histopathological examination of P generation rat tissues revealed compound-related lesions in the kidneys of male rats of the 0.5 percent dosage group. These lesions consisted of accumulations of amorphous to slightly granular, lightly eosinophilic material in the lumina of renal tubules, particularly near the corticomedullary junction. The term "nephrosis" was used to describe the lesions which were considered microscopically distinct from the intraluminal accumulations of homogenous proteinic material associated with the spontaneous degenerative nephropathy syndrome of rats. "Epithelial regeneration" of the renal tubules was evident, which may be assoicated with a variety of degenerative processes, especially the spontaneous degenerative nephropathy syndrome, mentioned above. However the increased incidence of this regeneration observed in the high-dosage rats suggests a compound-related effect. These lesions were not so advanced as to expect a clinically detectable effect on renal function. Lower concentrations of compound did not produce these effects, and all other findings were considered incidental.

2) F1 GENERATION

CLINICAL SIGNS AND MORTALITY
One dam, a control group animal, was found dead at approximately 17 days of pregnancy, and was submitted for necropsy. No apparent reason could be determined for the cause of death.

BODY WEIGHT AND WEIGHT GAIN
Body weights of female rats in the 0.5 percent dosage group were significantly depressed from the first week of the dosing period through week 10, when compared to the control group weights. Elevated body weights were observed in the 0.05 percent group from weeks 5 through 10.
As with the female rats, male rats in the 0.5 percent dosage group experienced significantly reduced lowered body weights throughout the pre-mating period. Again, male rats in the 0.05 percent group exceeded the body weights of the control and mid-dosage groups during weeks 7 through 10.

FOOD CONSUMPTION
Feed consumption figures during the dosing period revealed that all groups of rats, both male and female, ate similar portions of chow, and were not influenced by compound concentrations.

HISTOPATHOLOGY: NON-NEOPLASTIC
Histopathological examination of tissues form the F1 generation rats again showed "nephrosis " and " tubular regeneration" in the kidneys of a small number of male rats which was apparently associated with compound administration. All other findings were considered incidental or associated with spontaneous disease complexes of rats.

Key result

Dose descriptor:

NOAEL

Remarks:

(P Generation)

Effect level:

50 mg/kg bw/day (actual dose received)

Based on:

test mat.

Sex:

male/female

Basis for effect level:

other: NOAEL for general toxicity based on effects on body weights.

Key result

Dose descriptor:

NOAEL

Remarks:

(F1 Generation)

Effect level:

50 mg/kg bw/day (actual dose received)

Based on:

test mat.

Sex:

male/female

Basis for effect level:

other: NOAEL for general toxicity based on effects on body weights.

Key result

Critical effects observed:

not specified

Conclusions:

NOAEL general toxicity: 1000 ppm (corresponding to 50 mg/kw bw/day) based on effects on body weight.

P generation male and female rats fed with a high dose diet containing 5000 ppm zinc naphthenate showed body weight depression even though food consumption was comparable to other groups.
Lethargy was observed in males of the 5000 ppm group.

Reference 2

Endpoint:

sub-chronic toxicity: oral

Type of information:

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

Adequacy of study:

key study

Justification for type of information:

REPORTING FORMAT FOR THE ANALOGUE APPROACH

1. HYPOTHESIS FOR THE ANALOGUE APPROACH
This read-across is based on the hypothesis that source and target substances have similar toxicological properties because they hydrolyse to common products.

This prediction is supported by toxicological data on the substances themselves and on the dissolution products of the substances.
Target and source substances are mono-constituent substances. Both substances differ only in the production process, resulting in (i) an neutral product and (ii) a basic product.

The target substance is the basic product containing a slightly higher zinc content. The dissolution product, namely the zinc cation, is not the driver for toxic effects.
Consequently, the target substance is identical to the source substance and share a structural similarity with common functional groups, carboxylic acid, alkyl side chains.

Therefore, read-across from the existing repeated dose toxicity study on the source substance is considered as an appropriate adaption to the standard information requirements of Annex VIII- X, 8.6, 8.6.1 and 8.6.2 of the REACH Regulation for the target substance, in accordance with the provisions of Annex XI, 1.5 of the REACH Regulation.

The justification of the proposed read-across approach is elaborated in the next chapters. Please find this information in the attachements as well.


2. SOURCE AND TARGET CHEMICAL(S) (INCLUDING INFORMATION ON PURITY AND IMPURITIES)
a) Target substance
The target substance naphthenic acids, zinc salts, basic is a mono-constituent substance (EC: 282-762-6, CAS: 84418-50-8).
b) Source substance
The source substance naphthenic acids, zinc salts is a mono-constituent substance (EC: 234-409-2, CAS: 12001-85-3).
c) Purity and impurities
The source substance is derived from the same educts in the production process. Consequently, the hazard profile of the target substance is intrinsically covered.


3. ANALOGUE APPROACH JUSTIFICATION
a) Structural similarity and functional groups
The structure of the target and source substances are the same, namely a naphthenic acids, zinc salt. The target substance is the basic product containing a slightly higher zinc content compared to the neutral product. The dissolution product, namely the zinc cation, is not the driver for toxic effects with regard to Human Health and especially to local effects.

b) Common breakdown products
The common characteristic of the target substance and the source substance is that both liberate the same moiety upon dissolution in aqueous media. Zinc cations and naphthenate anions are formed upon dissolution under toxicological relevant conditions such as body fluids and in the environment.


4. DATA MATRIX
A comparison of the experimental toxicological data between the source and target substance is not applicable in the applied approach, since the overall ecotoxicity/systemic toxicity of the target substance is assessed by taking the (eco-)toxicological profile of the zinc cation and the acid anion (naphthenic acid) into account. An endpoint-specific description is provided in the respective endpoint summaries of both assessment entities.
The structural similarities between the source and the target substances and the similarities in their breakdown products presented above support the read-across hypothesis. Adequate, reliable and available scientific information indicates that the source and target substances and their subsequent degradation product have similar toxicity profiles.

Based on the considerations above, it can be concluded that the results of the repeated dose toxicity study conducted with the source substance is likely to predict the properties of the target substance and are considered as adequate to fulfil the information requirements of Annex VIII- X, 8.6, 8.6.1 and 8.6.2
Since the source substance is not classified as STOT RE via the oral route, the target substance naphthenic acids, zinc salts, basic will not be classified as well. Thus, the information requirements of Annex Annex VIII- X, 8.6, 8.6.1 and 8.6.2 are fulfilled by the source and target substance.

Reason / purpose for cross-reference:

read-across source

Remarks:

Doses / Concentrations:
500ppm (= 25mg/kg bw/day)
Basis:
nominal in diet

Remarks:

Doses / Concentrations:
1000ppm(= 50mg/kg bw/day)
Basis:
nominal in diet

Remarks:

Doses / Concentrations:
5000ppm(= 250mg/kg bw/day)
Basis:
nominal in diet

Clinical signs:

effects observed, treatment-related

Mortality:

mortality observed, treatment-related

Body weight and weight changes:

effects observed, treatment-related

Food consumption and compound intake (if feeding study):

no effects observed

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 specified

Histopathological findings: non-neoplastic:

effects observed, treatment-related

Histopathological findings: neoplastic:

no effects observed

Details on results:

1) P GENERATION

CLINICAL SIGNS AND MORTALITY
Male rats in the 0.5 percent dosage group appeared to become lethargic after week 9 of the dosing period. Alopecia was prevalent in the mid- and high-dosage animals of both sexes.
One male rat from the 0.1 percent dosage group was found cannibalised while the rats were group housed, prior to mating. Fighting was the apparent cause of death.

BODY WEIGHT AND WEIGHT GAIN
The P generation female rats in the 0.5 percent group (5000 ppm) experienced significantly reduced body weights by week 3 of compound administration, and continued through week 10. The control, low, and mid-dosage groups gained at similar rates.
Male rats fed a diet of 5000 ppm zinc naphthenate demonstrated significantly decreased body weights by week 8 of the 10 week dosing period.

FOOD CONSUMPTION AND COMPOUND INTAKE (if feeding study)
Weekly monitoring of feed consumption during the 10 week exposure period indicated all female rats ate similar portions, regardless of the dosage group. The same was also true for male rats, regardless of the zinc naphthenate concentration in the feed.

HISTOPATHOLOGY: NON-NEOPLASTIC
Histopathological examination of P generation rat tissues revealed compound-related lesions in the kidneys of male rats of the 0.5 percent dosage group. These lesions consisted of accumulations of amorphous to slightly granular, lightly eosinophilic material in the lumina of renal tubules, particularly near the corticomedullary junction. The term "nephrosis" was used to describe the lesions which were considered microscopically distinct from the intraluminal accumulations of homogenous proteinic material associated with the spontaneous degenerative nephropathy syndrome of rats. "Epithelial regeneration" of the renal tubules was evident, which may be assoicated with a variety of degenerative processes, especially the spontaneous degenerative nephropathy syndrome, mentioned above. However the increased incidence of this regeneration observed in the high-dosage rats suggests a compound-related effect. These lesions were not so advanced as to expect a clinically detectable effect on renal function. Lower concentrations of compound did not produce these effects, and all other findings were considered incidental.

2) F1 GENERATION

CLINICAL SIGNS AND MORTALITY
One dam, a control group animal, was found dead at approximately 17 days of pregnancy, and was submitted for necropsy. No apparent reason could be determined for the cause of death.

BODY WEIGHT AND WEIGHT GAIN
Body weights of female rats in the 0.5 percent dosage group were significantly depressed from the first week of the dosing period through week 10, when compared to the control group weights. Elevated body weights were observed in the 0.05 percent group from weeks 5 through 10.
As with the female rats, male rats in the 0.5 percent dosage group experienced significantly reduced lowered body weights throughout the pre-mating period. Again, male rats in the 0.05 percent group exceeded the body weights of the control and mid-dosage groups during weeks 7 through 10.

FOOD CONSUMPTION
Feed consumption figures during the dosing period revealed that all groups of rats, both male and female, ate similar portions of chow, and were not influenced by compound concentrations.

HISTOPATHOLOGY: NON-NEOPLASTIC
Histopathological examination of tissues form the F1 generation rats again showed "nephrosis " and " tubular regeneration" in the kidneys of a small number of male rats which was apparently associated with compound administration. All other findings were considered incidental or associated with spontaneous disease complexes of rats.

Key result

Dose descriptor:

NOAEL

Remarks:

(P Generation)

Effect level:

50 mg/kg bw/day (actual dose received)

Based on:

test mat.

Sex:

male/female

Basis for effect level:

other: NOAEL for general toxicity based on effects on body weights.

Key result

Dose descriptor:

NOAEL

Remarks:

(F1 Generation)

Effect level:

50 mg/kg bw/day (actual dose received)

Based on:

test mat.

Sex:

male/female

Basis for effect level:

other: NOAEL for general toxicity based on effects on body weights.

Key result

Critical effects observed:

not specified

Conclusions:

NOAEL general toxicity: 1000 ppm (corresponding to 50 mg/kw bw/day) based on effects on body weight.

P generation male and female rats fed with a high dose diet containing 5000 ppm zinc naphthenate showed body weight depression even though food consumption was comparable to other groups.
Lethargy was observed in males of the 5000 ppm group.

Endpoint conclusion

Endpoint conclusion:

adverse effect observed

Dose descriptor:

NOAEL

50 mg/kg bw/day

Study duration:

chronic

Species:

rat

Repeated dose toxicity: inhalation - systemic effects

Endpoint conclusion

Endpoint conclusion:

no study available

Repeated dose toxicity: inhalation - local effects

Endpoint conclusion

Endpoint conclusion:

no study available

Repeated dose toxicity: dermal - systemic effects

Endpoint conclusion

Endpoint conclusion:

no study available

Repeated dose toxicity: dermal - local effects

Endpoint conclusion

Endpoint conclusion:

no study available

Additional information

Since no repeated dose toxicity study with naphthenic acids, zinc salts, basic is available, read-across to naphthenic acids, zinc salts is applied.

Unlimited read-across from naphthenic acids, zinc salts to naphthenic acids, zinc salts, basic is justified, since the overbased naphthenic acids, zinc salts, basic only contains a surplus of zinc, which is, however, known not to be the driver for toxic effects with regard to Human Health.

One 2 -generation reproductive toxicity study in rats is available for naphthenic acids, zinc salts. The study is considered relevant and reliable without restrictions.

P generation male and female rats fed with a high dose diet containing 5000 ppm zinc naphthenate showed slight body weight depression even though food consumption was comparable to other groups. Lethargy was observed in males of the 5000 ppm group. Although no full histopathological examination was performed on all organs of the test animals, the effects on body weight observed in the high dose group animals are considered as mild signs of general systemic toxicity, suitable for setting a no observed adverse effect level. The NOAEL for systemic toxicity is 1000 ppm (corresponding to 50 mg/kw bw/day) based on effects on body weight.

In conclusion, the NOAEL for systemic toxicity in this 2 -generation reproductive toxicity study also covers the endpoint for repeated dose toxicity, thus can be used to fulfil the data requirements as laid down in regulation (EC) 1907/2006. For the purpose of hazard assessment of naphthenic acids, zinc salts, basic, the point of departure for the most sensitive endpoint will be used for the DNEL derivation. For the hazard assessment of Naphthenic acids, zinc salts, basic, the NOAEL of 50 mg/kg bw/day obtained in a two generation reproductive toxicity study with naphthenic acids, zinc salts will be used for the DNEL derivation.

Justification for classification or non-classification

In a relevant and reliable 2 -generation reproductive toxicity study, rats were exposed to 500, 1000 and 5000 ppm naphthenic acids, zinc salts via the diet. Systemic toxicity shown as body weight depression was observed in parental animals of the high dose group. There were no toxicological findings reported that would justify a classification for specific target organ toxicity with repeated exposure. Hence, no classification for naphthenic acids, zinc salts, basic as STOT RE via the oral route is required.