Naphthenic acids, lithium salts

Endpoint summary

Key value for chemical safety assessment

Effects on fertility

Description of key information

There are no data for lithium naphthenate. Data from appropriate read across substances are presented, with data on fatty acids C18 (unsaturated) lithium salts and naphthenic acids.

 

A dermal reproductive toxicity screening study in rats with fatty acids C18 (unsaturated) lithium salts was conducted according to OECD 422 and no adverse effects were seen in any of the reproductive parameters examined at any dose. Based on these data, the NOAEL for reproductive and developmental toxicity was 1089.75 mg/kg/day (Harlan 2010).

 

There were no treatment-related effects on any of the assessed reproductive parameters in an OECD Test Guideline 422 combined repeated dose and reproductive/developmental toxicity screening study involving the exposure of rats to a mixture of naphthenic acids by oral gavage at up to 900 mg/kg bw/day. The reproductive NOAEL was therefore established as 900 mg/kg bw/day (HPVIS, 2010).

 

Fatty acids C18 (unsaturated) lithium salts consists of a mixture of lithium salts C18 monocarboxylic acids with varying levels of saturation, with low concentrations of lithium salts C16 monocarboxylic acids with varying levels of saturation. The fatty acid components are chemically the same as the fatty acids exempt from registration under REACH Annex V and are considered to be non-hazardous. Any toxicity from this substance is expected to be driven by the lithium ion. Therefore, taking molecular weight, and thus lithium concentrations, for lithium salts of saturated C16 and 18 monocarboxylic acids as representative structures, fatty acids C18 (unsaturated) lithium salts is expected to have a lithium content in the range of 1.91 % to 2.97%. The lithium content for the hazard sample of lithium naphthenate is approximately 2.5%, which falls in the middle of this range and therefore the NOAEL of 1089.75 mg/kg/day for fatty acids C18 (unsaturated) lithium salt is considered applicable to lithium naphthenate.

 

As the NOAEL of 900 mg/kg bw/day for naphthenic acids is lower than the NOAEL for the lithium cation (NOAEL of 1089.75 mg/kg bw/day read across from fatty acids C18 (unsaturated) lithium salt), this value was taken as a worst-case scenario. As the molecular weight of the lithium salt of naphthenic acids is greater than the molecular weight of naphthenic acids themselves, the NOAEL of 900 mg/kg bw/day was applied directly to lithium naphthenate.

Link to relevant study records

Reference

Reference 1

Endpoint:

toxicity to reproduction

Remarks:

other: combined repeated dose & reproductive/developmental toxicity screening

Type of information:

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

Adequacy of study:

key study

Study period:

2010

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: The study is performed by NTP according to GLP and valid methods, therefore it is considered to be adequate, reliable and relevant for classification. The score 1 was given bij HPVIS.

Justification for type of information:

See IUCLID section 13 for read across justification

Reason / purpose for cross-reference:

read-across source

Qualifier:

according to guideline

Guideline:

OECD Guideline 422 (Combined Repeated Dose Toxicity Study with the Reproduction / Developmental Toxicity Screening Test)

Deviations:

no

Qualifier:

according to guideline

Guideline:

other: OPPTS 870.3650

Deviations:

no

GLP compliance:

yes

Limit test:

no

Species:

rat

Strain:

Sprague-Dawley

Sex:

male/female

Details on test animals or test system and environmental conditions:

no data

Route of administration:

oral: gavage

Vehicle:

corn oil

Details on exposure:

PREPARATION OF DOSING SOLUTIONS:
The naphthenic acids were suspended in corn oil to the appropriate concentrations and administered in 10 ml/kg doses.

Details on mating procedure:

- M/F ratio per cage: 1:1
- Length of cohabitation: 14 days. All females confirmed to have mated were placed in plastic maternity cages once mating was confirmed.
- Proof of pregnancy: vaginal plug referred to as day 0 of pregnancy
- Further matings after two unsuccessful attempts: Females for which copulation was not detected were placed in maternity cages at the end of the 1
- Any other deviations from standard protocol:Length of gestation was calculated as the time from confirmation of mating to the onset of delivery.

Analytical verification of doses or concentrations:

not specified

Duration of treatment / exposure:

Dosing of males was initiated 14 days prior to pairing and throughout a 14 day mating period for a total of 28-29 doses. Dosing of females was also initiated 14 days prior to pairing and continued throughout the mating and gestational periods until study termination on post-natal day 3. The total number of doses ranged from 39-53 depending on the time at which mating occurred.

Frequency of treatment:

Daily

Remarks:

Doses / Concentrations:
0, 100, 300, 900 mg/kg/day
Basis:
actual ingested

No. of animals per sex per dose:

12

Control animals:

yes, concurrent vehicle

Positive control:

no

Parental animals: Observations and examinations:

CAGE SIDE OBSERVATIONS:
- All rats were examined twice daily for mortality and general health.
- All animals were examined approximately 1 hour after each treatment, and all unusual observations were recorded.

DETAILED CLINICAL OBSERVATIONS:
- Time schedule:Detailed physical examinations of all animals were conducted weekly (See Section 7.5.1)

BODY WEIGHT: Yes
- Time schedule for examinations: females: recorded once week prior to test substance administration, on the first day of dose administration and weekly until evidence of copulation was obtained. From that point body weights of female rats were recorded on gestation days (GD) 0, 4, 7, 11, 14, 17, and 20 and on lactation days (LD) 0, 1 and 4 (termination). For females for which there was no evidence of copulation, body weights were recorded weekly until termination.

FOOD CONSUMPTION:
- Food consumption by adult animals was also recorded on the same schedule as the body weights.

WATER CONSUMPTION: No

OTHER:
- Parental mating, fertility, conception and copulation indices , gestation length, numbers of former implantation sites, absolute and relative organ weights, and pre-coital intervals.
- Toxicological parameters: See Section 7.5.1.

Oestrous cyclicity (parental animals):

no data

Sperm parameters (parental animals):

no data

Litter observations:

STANDARDISATION OF LITTERS
- Performed on day 4 postpartum: no

PARAMETERS EXAMINED
On the day of parturition, all pups were examined for viability, for the presence of gross malformations and to assess gender. The numbers of live and stillborn pups were recorded.
All offspring were uniquely identified and examined daily for signs of mortality and ill health. All offspring were individually weighed on PND 1 and 4. Gender was assessed on PND 0 and 4. At scheduled termination, PND 4, all surviving offspring were euthanized and discarded without further examination.

GROSS EXAMINATION OF DEAD PUPS: no data

Postmortem examinations (parental animals):

SACRIFICE
- Male animals: 14 days after mating
- Maternal animals: . Females for which there was no evidence of mating were sacrificed on post-cohabitation day 25, those that showed evidence of mating but failed to deliver were euthanized on post-mating day 25, and all others were euthanized on post-natal day 4.

GROSS NECROPSY: YES
- At termination rats were euthanized by carbon dioxide inhalation.
- Necropsies were conducted on all animals sacrificed in extremis or at study termination.

HISTOPATHOLOGY / ORGAN WEIGHTS
- An examination of target organs including male and female reproductive organs was also carried out as part of this test (See also Section 7.5.1).
- Organs examined included: ovaries with oviduct, uterus with cervix and vagina, testes with epididymides, prostate and seminal vesicles.
- The ovaries, testes and uteri were weighed and all were examined histologically

Postmortem examinations (offspring):

All offspring were individually weighed on PND 1 and 4.
Gender was assessed on PND 0 and 4At scheduled termination, PND 4, all surviving offspring were euthanized and discarded without further examination.

Statistics:

Parental mating, fertility, conception and copulation indices were analyzed using the Chi-square test with Yates’ correction (Hollander and Wolfe, 1999). Mean parental body weights (weekly, gestation and lactation), body weight changes and food consumption, offspring body weights and body weight changes, gestation length, numbers of former implantation sites, numbers of corpora lutea, number of pups born, live litter size on PND 0, unaccounted for sites, absolute and relative organ weights, and pre-coital intervals were evaluated by one-way analysis of variance (ANOVA) (Snedecor and Cochran, 1980) to determine intergroup differences between the vehicle control and test substance-treated groups. If the ANOVA revealed significant (p < 0.05) intergroup variance, Dunnett test (Dunnett, 1964) was used to compare the test substance-treated groups to the control group.

Reproductive indices:

See Tables below and in Section 7.8.2.
Mating, fertility, pregnancy and gestation indices were not provided as such, however No. of females mated, pregnant and with litters were given.
Pre-implantation loss not provided, but No. of corpora lutea and No. of implantation sites given.
Implanation index not provided, but No. of implanatation given.
Post-implantation indexes given.

Offspring viability indices:

Viability index not provided, but No. born and alive on day 4 given.
Sex ratio given (See Section 7.8.2)

Clinical signs:

no effects observed

Body weight and weight changes:

no effects observed

Food consumption and compound intake (if feeding study):

no effects observed

Organ weight findings including organ / body weight ratios:

no effects observed

Histopathological findings: non-neoplastic:

no effects observed

Other effects:

not examined

Reproductive function: oestrous cycle:

not examined

Reproductive function: sperm measures:

not examined

Reproductive performance:

no effects observed

The absolute epididymal weights were increased in the 900 mg/kg/day group but were not significantly different when expressed on a per body weight basis. The uterine weights were also significantly elevated but this was considered to have been a consequence of the fact that the females were all in lactational anaestrous. The uterine weights were within the historical range of the laboratory and were not considered to have been toxicologically important. There were no weight differences in any of the other organs and no pathological changes in any of the reproductive organs at the highest dose tested (900 mg/kg/day).

Dose descriptor:

NOAEL

Effect level:

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

Based on:

act. ingr.

Sex:

male/female

Basis for effect level:

other: mating index

Dose descriptor:

NOAEL

Effect level:

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

Based on:

act. ingr.

Sex:

male/female

Basis for effect level:

other: reproductive organ effects

Clinical signs:

no effects observed

Mortality / viability:

mortality observed, treatment-related

Description (incidence and severity):

Decrease No. born pups at 900 mg/kg bw - See Section 7.8.2

Body weight and weight changes:

effects observed, treatment-related

Description (incidence and severity):

decrease at 900 mg/kg bw - See Section 7.8.2

Sexual maturation:

not examined

Organ weight findings including organ / body weight ratios:

not examined

Gross pathological findings:

no effects observed

Histopathological findings:

not examined

Dose descriptor:

NOAEL

Generation:

F1

Effect level:

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

Based on:

act. ingr.

Sex:

male/female

Basis for effect level:

other: mating index

Dose descriptor:

NOAEL

Generation:

F1

Effect level:

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

Based on:

act. ingr.

Sex:

male/female

Basis for effect level:

other: reprodiuctive organ effects

Reproductive effects observed:

not specified

Table 1. Summary of reproductive parameters assessed in the repeated dose/reproductive toxicity study of refined naphthenic acids.

Dose (mg/kg/day)	Corn Oil Control	100 mg/kg/day	300 mg/kg/day	900 mg/kg/day
Number of females paired	12	12	12	12
Number of female mated	12	12	10	11
Number of females pregnant^a	9	12	10	11
Number of females with litters	9	12	10	11
Pre-coital interval (days)^b	1.4+0.7	2.3+1.1	4.2+3.3^c	3.8+3.5
Gestation length (days)	21.4+0.6	21.9+0.3	22.0+0.5	22.1+0.5
Corpora lutea	15.6+2.3	14.0+1.4	15.1+3.0	13.8+2.1
Implantation sites	15.0+2.4	13.6+1.1	13.0+1.2	12.2+3.7
Number born	14.1+1.9	12.9+1.1	12.0+1.6	10.8+3.8^c
Post-Implantation loss (%)^d	6.0	5.1	7.7	11.5

a. Pregnant = uterine implantation sites.

b. Data summarized as mean+standard deviation.

c. p < 0.05

d. Post-implantatoin loss = (No. of implantations - No. of life fetuses)/No. of implanatations (%)

Conclusions:

No reproductive effects were identified. The NOAEL for mating and reproductive effects of is 900 mg/kg/day.

Executive summary:

A combined repeated dose toxicity study with the reproduction/developmental toxicity screening test in Wistar ratswas performed by oral gavage with Naphtenic acids in corn oil. There were 3 test material treated groups (100, 300 and 900 mg/kg bw) along with a vehicle treated group (corn oil) each in 12 animals/sex/group. Male rats were dosed during premating, mating and afterwards for 28 days in total and females were dosed during premating, mating, gestation and up to day 3 post partum. In this section, only reproductive toxicity parameters are discussed: (furher info on repeated & developmental parameters is given in Section 7.5.1 and 7.8.2. Target organ findings were identified at the dose of 900 mg/kg bw, whereas 100 mg/kg bw was considered as the NOAEL for systemic toxicity.

No reproductive effects were identified up to 900 mg/kg bw . There were no weight differences in any of the other organs nor any pathological changes in the reproductive organs up to the highest dose tested (900 mg/kg/day). The NOAEL for mating and reproductive organ effects was 900 mg/kg/day.

Reference 2

Endpoint:

screening for reproductive / developmental toxicity

Type of information:

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

Adequacy of study:

key study

Study period:

2010-2011

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: According to or similar to guideline study OECD 422; GLP

Justification for type of information:

See IUCLID section 13 for read across justification

Reason / purpose for cross-reference:

read-across source

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 422 (Combined Repeated Dose Toxicity Study with the Reproduction / Developmental Toxicity Screening Test)

Deviations:

no

GLP compliance:

yes

Limit test:

no

Species:

rat

Strain:

Sprague-Dawley

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Charles River Laboratories
- Age at study initiation: approx. 8 weeks
- Weight at study initiation: Males - 266-311g; Females (nulliparous and nonpregnant) - 191-222g
- Housing: Individually housed in suspended, stainless steel, wire-mesh type cages, except during pairing, near parturition and during lactation. P females moved to plastic caging with wood chip bedding from GD20 - LD 4. Animal enrichment per SOP-ACU-89
- Diet (e.g. ad libitum): Lab Diet Certified Rodent Diet #5002, PMI Nutrition International, Inc., ad libitum.
- Water (e.g. ad libitum): ad libitum
- Acclimation period: 1 week

ENVIRONMENTAL CONDITIONS
- Temperature (°F): 64-79
- Humidity (%): 30-70
- Photoperiod (hrs dark / hrs light): 12 h /12 h

IN-LIFE DATES: From: 30 November 2010 To: 1 Febraury 2011

Route of administration:

dermal

Vehicle:

water

Details on exposure:

TEST SITE
- Area of exposure: dorsal surface; equivalent to approx. 10% of the total body surface area
- Type of wrap if used: gauze dressing and non-absorbent cotton covered with self-adhesive take and athletic tape.
- Time intervals for shavings or clipplings: As required

REMOVAL OF TEST SUBSTANCE
- Washing (if done): Wypall wet with distilled water.
- Time after start of exposure: 6 h

TEST MATERIAL
- Amount(s) applied (volume or weight with unit): 2.5 mL/kg
- Concentration (if solution): equivalent to 0; 100; 300; 1000 mg/kg/day (nominal)
- Constant volume or concentration used: yes


VEHICLE
- Distilled deionised tap water
- Concentration (if solution): N/A
- Lot/batch no. (if required): not available
- Purity: not available

USE OF RESTRAINERS FOR PREVENTING INGESTION: no

Details on mating procedure:

After 2 weeks of treatment, P animals (Groups 1 to 4), each female was housed in cage of a male from the same treatment group.
- M/F ratio per cage: 1
- Length of cohabitation: Until evidence of copulation was established (max 14 days). Housed individually during daytime 6-hour exposure period.
- Proof of pregnancy: vaginal plug and / or vaginal lavage with the presence of sperm; referred to as gestation day (GD) 0
- After 14 days of unsuccessful pairing females were returned to individual cages.
- After successful mating each pregnant female was caged individually for the remainder of the study.

Analytical verification of doses or concentrations:

yes

Details on analytical verification of doses or concentrations:

The concentrations of Fatty acids C18-(unsaturated) lithium salts in 52 dosing formulation samples was established by determining lithium content by Inductively Couple Plasma Optical Emission Spectroscopy (ICP-OES). Samples were processed by microwave aided acid digestion (DIN 51460-2) before submitting to ICP-OES (EN ISO 11885).

Duration of treatment / exposure:

Males dosed for at least 43 days, beginning 14 days prior to mating (Groups 1-4).
Dosing of the females began 14 days prior to mating and continued through mating, up to and including GD 19 (Groups 1-4). Another set of animals (Groups 5 and 6) were dosed for a total of 43 days and then began a 14-day (non-treated) recovery period.

Frequency of treatment:

Daily, once per day for 6 hours.

Details on study schedule:

- Age at mating of the mated animals in the study: approximately 10 weeks of age

Remarks:

Doses / Concentrations:
0; 100; 300; 1000 mg/kg bw
Basis:
nominal conc.

Remarks:

Doses / Concentrations:
0; 111.25; 345.00; 1089.75 mg/kg bw
Basis:
analytical conc.

No. of animals per sex per dose:

Terminal Groups (Groups 1 to 4): 10 animals per sex per dose
Recovery Groups (Groups 5 and 6): 5 animals per sex per dose

Control animals:

yes, concurrent vehicle

Details on study design:

- Dose selection rationale: The dose levels were selected on the basis of available data from a previous dose ranging study (MPI Study No. 1883-001). Animals were dosed dermally once a day at 0, 525, 1050 and 2100 mg/kg bw/day (water based Fatty acids C18-(unsaturated) lithium salts) and for two weeks at 2106 mg/kg/day with oil-based Fatty acids C18-(unsaturated) lithium salts. The results of this study identified significant dose responsive dermal effects, based on maximized erythema and eschar scores at dose levels ≥1050 mg/kg bw/day Fatty acids C18-(unsaturated) lithium salts. A slight decrease in mean body weight was noted in males during the last week of
dosing, however, not other adverse body weight or food consumption effects were observed at the dose levels tested. A nominal high-dose level of 1000 mg/kg bw/day (at a slightly lower concentration based on dose volume) was selected for the defintive study to insure some morbidity. The nominal low dose level (100 mg/kg bw/day) was selected with 10-fold decrease to insure a no effect level, and a nominal mid-dose level of 300 mg/kg bw/day was selected to be about 3 times higher than the low-dose level and about 3 times lower than the high-dose level.
- Rationale for animal assignment (if not random): All animals placed on study will have body weights that fall within 20% of the mean bodyweight for each sex. Animals considered suitable for study will be weighed prior to treatment. After the appropriate number of animals with the highest and lowest body weights has been excluded, the remaining required number of animals on study will be randomized, by sex, into treatment groups using a standard, by weight, measured value randomization procedure.

- Rationale for selecting satellite groups: As above.

- Post-exposure recovery period in satellite groups: 14-day non treatment period.

- Section schedule rationale (if not random): Randomized.

Positive control:

Not included

Parental animals: Observations and examinations:

CAGE SIDE OBSERVATIONS: Yes
- Time schedule: At least twice a day, 7 days a week, for morbidity, mortality, injury, and availability of food and water. Towards end of gestation period, P females examined twice daily for signs of parturition.
- Cage side observations recorded are not reported, but are maintained in the study file.

DETAILED CLINICAL OBSERVATIONS: Yes
- Time schedule: Daily during the study (after wrap removal on dose days).

DERMAL IRRITATION: Yes
- Time schedule for examinations: Prior to first dose and daily during the study (after wrap removal on dosing days).

BODY WEIGHT: Yes
- Time schedule for examinations: Weekly during the study. Mated females weighed on GD 0, 7, 14 and 20 and on LD 0 and 4 and at termination.

FOOD CONSUMPTION:
- Food consumption for each animal determined and mean daily diet consumption calculated as g food/kg body weight/day: Yes

WATER CONSUMPTION: No

OTHER:
HAEMATOLOGY: Yes
- Time schedule for collection of blood: at termination / at recovery
- Anaesthetic used for blood collection: Yes (CO2)
- Animals fasted: No
- How many animals: 5 per sex per group (P animals) in Groups 1-4 at Termination (same animals designated for behavioral testing). 5 per sex per group in Groups 5 and 6 at Recovery
- Parameters checked:
 leukocyte count (total and absolute differential);  erythrocyte count;  hemoglobin;  hematocrit;  mean corpuscular hemoglobin, mean corpuscular volume, mean corpuscular hemoglobin concentration (calculated);  absolute reticulocytes;  platelet count;  blood cell morphology

CLINICAL CHEMISTRY: Yes
- Time schedule for collection of blood: at termination / at recovery
- Animals fasted: No
- How many animals: 5 per sex per group (P animals) in Groups 1-4 at Termination (same animals designated for behavioral testing). 5 per sex per group in Groups 5 and 6 at Recovery
- Parameters checked:
 alkaline phosphatase;  total bilirubin (with direct bilirubin if total bilirubin exceeds 1 mg/dL);  aspartate aminotransferase;  alanine aminotransferase;  gamma glutamyl transferase;  sorbitol dehydrogenase;  urea nitrogen;  creatinine;  total protein;  albumin;  globulin and A/G (albumin/globulin) ratio (calculated);  glucose;  total cholesterol;  triglycerides;  electrolytes (sodium, potassium, chloride);  calcium;  phosphorus

Oestrous cyclicity (parental animals):

Not determined

Sperm parameters (parental animals):

Parameters examined in P male parental generations:
testis weight, epididymis weight

Litter observations:

Litters were examined as soon as possible after delivery(LD 0) and on LD 4.

PARAMETERS EXAMINED
The following parameters were examined in F1 offspring:
Litter size, number of stillborn and liveborn pups, survival, number of males and females, individual body weights, abnormal behaviour, and gross abnormalities of the pups.

GROSS EXAMINATION OF DEAD PUPS:
yes, for external abnormalities. Offspring found dead on LD 0 had lungs removed and placed in tap water to determine whether live/stillborn.

Postmortem examinations (parental animals):

SACRIFICE
- Male animals: All surviving animals on day 44 (Groups 1-4) and day 57 (groups 5 and 6)
- Maternal animals: All surviving animals on LD 4 (groups 1-4) and day 57 (groups 5 and 6)

GROSS NECROPSY
- Gross necropsy consisted of external and internal examinations including the cranial, thoracic, and abdominal viscera, and recorded number of total implantation scars and number of corpora lutea on each ovary.

HISTOPATHOLOGY / ORGAN WEIGHTS
The tissues indicated in Table 1 were prepared for microscopic examination and weighed, respectively.

Postmortem examinations (offspring):

SACRIFICE
- The F1 offspring sacrificed on LD 4.
- These animals were subjected to postmortem external examinations.

GROSS NECROPSY
- Gross necropsy consisted of external examinations.

Statistics:

The raw data were tabulated within each time interval, and the mean and standard deviation were calculated for each endpoint by sex and group. For each endpoint, treatment groups were compared to the control group using: Group pair-wise comparisons; Cochran Manzel Haenszel test; log transformation / group pair-wise comparisons; Fisher's exact test; Arcsin-square root transformation, and; Covariate analysis, as presented in Table 2.

Reproductive indices:

Male and female mating index; fertility index and fecundity index.

Females Delivering Litters (%) = (No. females delivering litters / No. females pregnant) x 100

Females with All Stillborn (%) = (No. litters with all stillborn pups / No. females delivering litters) x 100

Females with Stillborn Pups (%) = (No. litters with at least 1 stillborn pup / No. females delivering litters) x 100

Fertility Index - Males (%) = (No. males impregnating a female / No. males paired) x 100

Fertility Index - Females (%) = (No. females pregnant / No. females paired) x 100

Offspring viability indices:

Live Birth Index (%) = (No. live pups at birth / No. pups born) x 100

Stillborn Index = No. stillborn pups / No. pups born

Viability Index – Day 4 (%) = (No. pups surviving 4 days (preculling) / No. live pups at birth) x 100

Clinical signs:

effects observed, treatment-related

Description (incidence and severity):

345 and 1089.75 mg/kg bw/day: localized scabbed area on dorsal surface and scabbed area in the thoracic region (related to test site) during dosing period. Recovery animals indicated trend towards recovery after cessation of dosing.

Body weight and weight changes:

effects observed, treatment-related

Description (incidence and severity):

Trend to decreasing mean body weight in males at 1089.75 mg/kg bw/day - though not statistically significant. Mean body weight change was statistically decreased in treated males at 1089.75 mg/kg bw/day during the premating interval from Weeks 1 to 3.

Food consumption and compound intake (if feeding study):

effects observed, treatment-related

Description (incidence and severity):

Trend to decreasing mean body weight in males at 1089.75 mg/kg bw/day - though not statistically significant. Mean body weight change was statistically decreased in treated males at 1089.75 mg/kg bw/day during the premating interval from Weeks 1 to 3.

Organ weight findings including organ / body weight ratios:

effects observed, treatment-related

Histopathological findings: non-neoplastic:

effects observed, treatment-related

Description (incidence and severity):

Test article-related microscopic findings in skin: minimal/moderate erosion/ulceration, epidermal hyperplasia and exudate, minimal/mild acute/subacute/chronic inflammation, minimal edema. 1000 mg/kg/day: secondary adaptive findings in thymus and spleen.

Other effects:

not examined

Reproductive function: oestrous cycle:

not examined

Reproductive function: sperm measures:

not examined

Reproductive performance:

no effects observed

Description (incidence and severity):

male/female fertility and fecundity indices and copulatory intervals unaffected by treatment.

CLINICAL SIGNS AND MORTALITY (PARENTAL ANIMALS)
300 and 1000 mg/kg bw/day animals: localized scabbed area on dorsal surface and scabbed area in the thoracic region (related to test site) during dosing period. These were dose-responsive, being most pronounced at the high dose level of 1000 mg/kg bw/day in both males and females. Recovery animals indicated trend towards recovery after cessation of dosing, although these dermal fndings remained evident. [See attached Parental Summary Tables 1-4; and Recovery Summary Table 32]

DERMAL IRRITATION SCORES
Daily dermal scoring (edema, as well as erythema and eschar) during the course of the dosing period in treated male and female animals, revealed dose responsive effects, particularly at 300 and 1000 mg/kg bw/day, with controls being devoid of any significant adverse dermal effects. [See attached Parental Summary Tables 8-11]
The results of the dermal scoring in the animals at 100 mg/kg bw/day were generally comparable to the controls. Edema in the males at 300 mg/kg bw/day was limited to very slight effects during the start of dosing, which progressed to slight edema, with a few instances of moderate edema at a little over 5 weeks into dosing. Edema in the males at 1000 mg/kg bw/day started at very slight effects right after dosing, which became slight edema after about a week of dosing and progressed to moderate edema by 3 weeks of dosing. Edema in the females at 300 mg/kg bw/day was similar to the males up to the time of mating. At 1000 mg/kg bw/day, edema also progressed to slight edema by Day 2 of dosing, prior to mating. During gestation, edema was very slight in the 100 mg/kg bw/day group; it was slight in appearance at 300 mg/kg bw/day and moderate at 1000 mg/kg bw/day. During lactation edema was limited to very slight effects at 300 and 1000 mg/kg bw/day.
The evaluation of erythema and eschar (to be referred to as erythema) showed more significant dermal scoring in the treated animals. Erythema in the males at 300 mg/kg bw/day was generally very slight starting about a week of dosing and continued during the dosing period (Days 1 to 44). Erythema in the males at 1000 mg/kg bw/day started with very slight to well-defined effects, and by the first week of dosing progressed from well defined to moderate erythema, with a few instances of severe edema. By three weeks of dosing, most of the males at 1000 mg/kg bw/day had moderate to severe findings. Erythema in the females at 300 mg/kg bw/day during the premating period started with very slight findings and some well defined effects about 5 days into dosing and this progressed to well-defined findings by two weeks of treatment until mating. Erythema at 1000 mg/kg bw/day for females during the premating period started with very slight to well defined findings, which progressed to well defined, moderate, and in a few instances severe erythema by two weeks of dosing, prior to mating.
These localized dermal effects at 300 and 1000 mg/kg bw/day were considered to be test article related. In the designated recovery animals the dermal scores were similar to the terminal animals, but there was a decreasing trend in severity and incidence after cessation of dosing. [See attached Recovery Summary Table 34]

BODY WEIGHT AND FOOD CONSUMPTION (PARENTAL ANIMALS)
There was a trend of decreasing mean body weight in the males at 1000 mg/kg bw/day, though, the values were not statistically identified. Mean body weight change was statistically decreased in the treated males at 1000 mg/kg bw/day during the premating interval from Weeks 1 to 3. Mean body weight and body weight gain in the treated females were generally similar to the controls and did not show any definitive treatment related effects over the
dosing period. [See attached Parental Summary Tables 16-27]
In the designated recovery animals, mean body weight at 1000 mg/kg bw/day was statistically decreased in the males during Weeks 3, 4, 5, 6, and 7, which correlated to the decreases in body weight gain in these animals during weekly study intervals 1-2, 2-3, 3-4, 4-5, and 1-7. Mean body weight at 1000 mg/kg bw/day continued to be significantly lower than controls during the recovery period; however, the mean body weight gain was comparable to the controls, indicating a reversal of the body weight effects after cessation of dosing. The designated recovery females did not show any statistically significant body weight changes, as compared to the controls. [See attached Recovery Summary Table 35-36]

REPRODUCTIVE PERFORMANCE (PARENTAL ANIMALS)
Male and female fertility and fecundity indices and copulatory intervals unaffected by treatment. [See attached Reproductive Summary Table 28.]
Natural delivery and Litter Data un affected by treatment. [See attached Reproductive Summary Table 29.]

ORGAN WEIGHTS (PARENTAL ANIMALS)
Possible test article-related organ weight differences at the terminal necropsy were present in the spleen. [See attached Pathology Summary Table 2; Recovery Pathology Summary Table 6]
At the terminal necropsy, the mean spleen weight (relative to body weight) was statistically significantly increased in males at 1000 mg/kg bw/day versus controls. The increased spleen/body weight ratio may have been associated with the lower mean body weight of males at this dose level compared to controls and/or the increased mean absolute spleen weight that may have reflected increases in extramedullary hematopoiesis noted microscopically.
Additional statistically significant organ weight differences at the terminal necropsy were limited to the increased mean adrenal gland weight (relative to body weight) of females at 1000 mg/kg bw/day compared to controls. There was no microscopic correlate for this effect, and the relationship to test article administration was unclear.

GROSS PATHOLOGY (PARENTAL ANIMALS)
Test article-related macroscopic findings were limited to the dose site in the skin. At the terminal necropsy, minimal to moderate abrasion/scab formation was identified in the dose site in the skin in control males and treated animals of both sexes with a dose-related increase in the incidence and/or severity in males at 300 and 1000 mg/kg bw/day and in females at all dose levels compared to controls. This reflected the test article-related erosion/ulceration noted microscopically in treated skin (see Microscopic section). At the recovery necropsy, the incidence and overall severity of abrasion/scab formation was reduced in animals at 1000 mg/kg bw/day, indicating partial resolution of this finding over the recovery period.
Other macroscopic findings were infrequent and typical of those commonly identified in rats of this strain and age. [See attached Pathology Summary Table 1; Recovery Pathology Summary Table 5]

HISTOPATHOLOGY (PARENTAL ANIMALS) - NON-NEOPLASTIC
Test article-related microscopic findings were present in treated skin, and possible test article effects were also noted in the thymus and spleen. Test article-related increases in the incidence and/or severity of microscopic findings in treated skin were present in males at 300 and 1000 mg/kg bw/day and in females at all dose levels versus controls at the terminal necropsy. These findings were generally present with a dose-related increase in incidence and severity, however, treated skin was not examined in all mid-dose animals (microscopic examination limited to animals with gross lesions). Test article-related microscopic findings in treated skin included minimal to moderate erosion/ulceration, epidermal hyperplasia and exudate, minimal to mild acute to subacute/chronic inflammation, and minimal edema. At the recovery necropsy, test article-related microscopic findings in treated skin in animals at 1000 mg/kg bw/day were similar, although they occurred at a lower incidence and severity indicating partial resolution of these findings over the recovery period. Minimal to mild cortical lymphoid depletion was noted in the thymus in animals of both sexes at 1000 mg/kg bw/day at the terminal necropsy while this finding was not identified in control animals. However, notably, there were no statistically significant differences in the mean thymus weight and the thymus was not examined microscopically for all control and treated animals. Thymic lymphoid depletion in animals at 1000 mg/kg bw/day may have been a secondary finding due to stress associated with the test article-related lesions in treated skin as evidenced by self-mutilation and hypersensitivity to touch noted clinically in males at this dose level. The thymus was not examined microscopically at the recovery necropsy. At the terminal necropsy, there was a slight increase in the incidence and severity of extramedullary hematopoiesis in the spleen in animals at 1000 mg/kg bw/day versus controls. The severity of splenic extramedullary hematopoiesis was generally increased in both control and treated females, likely due to recent parturition, but the slight increase in the incidence of this finding in animals at 1000 mg/kg bw/day may have also reflected an adaptive response secondary to test article-related inflammation in treated skin. The spleen was not examined microscopically at the recovery necropsy. [See attached Pathology Summary Table 3; Recovery Pathology Summary 7]

OTHER FINDINGS (PARENTAL ANIMALS)

Dose descriptor:

NOAEL

Effect level:

> 1 089.75 mg/kg bw/day

Based on:

test mat.

Sex:

male/female

Basis for effect level:

other: Reproductive parameters (male/female fertility and fecundity indices, and copulatory intervals) were unaffected by treatment. No statistically significant changes in delivery data and pup development / survival.

Dose descriptor:

other: NOAEL local effects

Effect level:

111.25 mg/kg bw/day

Based on:

test mat.

Sex:

male/female

Basis for effect level:

other: see 'Remark'

Clinical signs:

no effects observed

Mortality / viability:

no mortality observed

Body weight and weight changes:

no effects observed

Sexual maturation:

not examined

Organ weight findings including organ / body weight ratios:

not examined

Gross pathological findings:

no effects observed

Histopathological findings:

not examined

There were no treatment-related effects at any dose level on any of the reproductive parameters evaluated in this study including offspring survival (gestation and postnatal survival indices, percent pre- and post-implantation loss), pup body weight and pup sex ratio. There were also no treatment-related effects on any of the developmental parameters evaluated including external abnormalities, number of live and still births, mortality, sex determination and weights of pups. [See attached Reproductive Summary Tables 30 and 31.]

Dose descriptor:

NOAEL

Generation:

F1

Effect level:

> 1 089.75 mg/kg bw/day

Based on:

test mat.

Sex:

male/female

Basis for effect level:

other: No reproductive effects or definitive test-article related changes in the development or survival of the offspring.

Reproductive effects observed:

not specified

See attached documents.

Conclusions:

Dermal application of Fatty acids C18-(unsaturated) lithium salts to the dorsal surface of Parental male and female rats at dose levels of 100, 300, and 1000 mg/kg bw/day did not result in any adverse reproductive effects or any definitive test article-related changes in the development or survival of the offspring.

Executive summary:

Dermal application of Fatty acids C18-(unsaturated) lithium salts to the dorsal surface of Parental male and female rats at dose levels of 100, 300, and 1000 mg/kg bw/day did not result in any adverse reproductive effects or any definitive test article-related changes in the development or survival of the offspring.

In addition, results from the clinical pathology evaluations and neurobehavioral testing did not reveal any definitive effects that could be attributed to treatment at the dose levels tested. Test article-related dermal changes were limited to local effects at the test site for Parental animals at 300 and 1000 mg/kg bw/day, which showed a decreasing trend following cessation of dosing in the designated recovery animals. Microscopic evaluation of the skin at the test site showed minimal to moderate erosion/ulceration, epidermal hyperplasia and exudate, minimal to mild acute to subacute/chronic inflammation and minimal edema, which confirmed the macroscopic findings. At recovery necropsy, test article-related microscopic findings in treated skin in animals at 1000 mg/kg bw/day were morphologically similar, although they occurred at a lower incidence and severity indicating partial resolution of these findings following the recovery period. Microscopic findings of splenic extramedullary hematopoiesis and thymic lympoid depletion noted at 1000 mg/kg bw/day were considered to be secondary adaptive responses to parturition and localized dermal effects.

Systemic effects were limited to changes in body weight and organ weight at 1000 mg/kg bw/day, the highest dose level tested.

In summary, there were no treatment related effects at any dose level on any of the reproductive parameters evaluated in this study, or in any of the developmental parameters evaluated. Based on these daya, the NOAEL for developmental toxicity was >1089.75 mg/kg bw/day and the NOAEL for reproductive toxicity was also >1089.75 mg/kg bw/day.

Effect on fertility: via oral route

Endpoint conclusion:

no adverse effect observed

Dose descriptor:

NOAEL

900 mg/kg bw/day

Study duration:

subacute

Species:

rat

Quality of whole database:

Guideline study conducted to GLP.

Effect on fertility: via inhalation route

Endpoint conclusion:

no study available

Effect on fertility: via dermal route

Endpoint conclusion:

no adverse effect observed

Dose descriptor:

NOAEL

1 089.75 mg/kg bw/day

Study duration:

subacute

Species:

rat

Quality of whole database:

Guideline study conducted to GLP.

Additional information

There are no data for lithium naphthenate. Data from appropriate read across substances are presented, with data on fatty acids C18 (unsaturated) lithium salts and naphthenic acids.

 

Fatty acids C18 (unsaturated) lithium salts

There are no data available for lithium naphthenate. A key toxicity and reproductive toxicity screen, using the OECD 422 study design, was conducted in rats on fatty acids C18 (unsaturated) lithium salts via dermal administration. The test material was administered at dose levels of 0, 100, 300 and 1000 mg/kg/day nominal, equating to 111.25, 345 and 1089.75 mg/kg/day by analysis, and were based on local dermal effects from a dose range finding study. There were no treatment-related effects at any dose level on any of the reproductive parameters evaluated in this study, or in any of the developmental parameters evaluated. Based on these data, the NOAEL for reproductive and developmental toxicity was 1089.75 mg/kg/day. The lack of reproductive and developmental toxicity when C18 (unsaturated) lithium salts was administered to rats can be read across to lithium naphthenate, and no classification for this endpoint would be required. The consideration concerning the margin of safety between the human therapeutic dose and the NOAELs found in the relevant studies is presented in the Repeated Dose Toxicity section. The same proposals regarding the use of the human data for DNEL derivation are applicable for the developmental toxicity endpoint.

 

Naphthenic acids

In a combined repeated dose toxicity and reproduction/developmental toxicity screening study, conducted according to OECD Test Guideline 422 and to GLP, Sprague-Dawley rats (12/sex/group) were orally administered a mixture of naphthenic acids by stomach tube (gavage, in corn oil) at doses of 0, 100, 300 or 900 mg/kg bw/day. Males were dosed for 28 days (during the pre-mating, mating and post-mating periods) and females were dosed through pre-mating, mating, gestation and up to day 3 post partum (39-53 days in total). There were no test item-related adverse effects on the measured reproductive parameters (including mating index, precoital time, gestation length, corpora lutea and post-implantation loss) nor any microscopic effects on the reproductive organs. Consequently, the NOAEL for reproductive toxicity was set at 900 mg/kg bw/day, the highest dose tested (HPVIS, 2010). [See Repeated dose toxicity and Effects on developmental toxicity sections for further details].

 

In a non-guideline study, a group of 12 male New Zealand white rabbits received dermal applications of 2 ml undiluted calcium naphthenate (in an unspecified ‘carrier oil’) for 6 hours/day on 5 days/week for 10 weeks. A control group of 12 male rabbits was similarly exposed to the vehicle only. After the exposure period each male was mated with 2 untreated females. Males were necropsied either directly after mating or approximately 12 weeks later; gross and microscopic examinations of the male reproductive tracts were conducted. The females were necropsied on day 29 of gestation. Numbers of corpora lutea, total implantations, pre-and post-implantation losses and numbers of viable foetuses were recorded. Calcium naphthenate (in ‘carrier oil’) showed no effects on any of the evaluated parameters (Dix and Cassidy, 1983).

 

In a non-guideline study, female Wistar rats (13-14/group) were gavaged with a mixture of naphthenic acids (isolated from Athabasca oil sands, in corn oil) at doses of 0, 6 or 60 mg/kg bw/day for a total of 39-53 days (through 14 days pre-mating, mating, gestation and up to post-natal day 3). A dramatic effect on female fertility was observed in the high-dose group, with only a single female successfully bearing a litter; total cholesterol was significantly reduced at this dose. Mating and ovulation were unaffected by treatment (Rogers, 2003). These results suggest that the dose-related female infertility may be associated with poor embryonic implantation, an effect that might be secondary to depressed sex hormone production requiring cholesterol as a precursor. [See Effects on developmental toxicity section for further details].

 

Conclusion

As the NOAEL of 900 mg/kg bw/day for naphthenic acids is lower than the NOAEL for the lithium cation (NOAEL of 1089.75 mg/kg bw/day read across from fatty acids C18 (unsaturated) lithium salt), this value was taken as a worst-case scenario. As the molecular weight of the lithium salt of naphthenic acids is greater than the molecular weight of naphthenic acids themselves, the NOAEL of 900 mg/kg bw/day was applied directly to lithium naphthenate.

Effects on developmental toxicity

Description of key information

There are no data for lithium naphthenate. Data from appropriate read across substances are presented, with data on fatty acids C18 (unsaturated) lithium salts and naphthenic acids.

 

A dermal reproductive toxicity screening study in rats with fatty acids C18 (unsaturated) lithium salts was conducted according to OECD 422 and no adverse effects were seen in any of the reproductive parameters examined at any dose. Based on these data, the NOAEL for reproductive and developmental toxicity was 1089.75 mg/kg/day (Harlan 2010).

 

In an OECD Test Guideline 422 combined repeated dose and reproductive/developmental toxicity screening study, a mixture of naphthenic acids was administered to rats by oral gavage at doses of 0, 100, 300 or 900 mg/kg bw/day. The developmental NOAEL was considered to be 100 mg/kg bw/day based on reductions in the number of offspring, live pups born, and offspring body weights observed at higher doses (HPVIS, 2010).

 

Fatty acids C18 (unsaturated) lithium salts consists of a mixture of lithium salts C18 monocarboxylic acids with varying levels of saturation, with low concentrations of lithium salts C16 monocarboxylic acids with varying levels of saturation. The fatty acid components are chemically the same as the fatty acids exempt from registration under REACH Annex V and are considered to be non-hazardous. Any toxicity from this substance is expected to be driven by the lithium ion. Therefore, taking molecular weight, and thus lithium concentrations, for lithium salts of saturated C16 and 18 monocarboxylic acids as representative structures, fatty acids C18 (unsaturated) lithium salts is expected to have a lithium content in the range of 1.91 % to 2.97%. The lithium content for the hazard sample of lithium naphthenate is approximately 2.5%, which falls in the middle of this range and therefore the NOAEL of 1089.75 mg/kg/day for fatty acids C18 (unsaturated) lithium salt is considered applicable to lithium naphthenate.

 

As the NOAEL of 100 mg/kg bw/day for naphthenic acids is lower than the NOAEL for the lithium cation (NOAEL of 1089.75 mg/kg bw/day read across from fatty acids C18 (unsaturated) lithium salt), this value was taken as a worst-case scenario. As the molecular weight of the lithium salt of naphthenic acids is greater than the molecular weight of naphthenic acids themselves, the NOAEL of 100 mg/kg bw/day was applied directly to lithium naphthenate.

Link to relevant study records

Reference

Reference 1

Endpoint:

developmental toxicity

Type of information:

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

Adequacy of study:

key study

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: The study is performed by NTP according to GLP and valid methods, therefore it is considered to be adequate, reliable and relevant for classification. The score 1 was given bij HPVIS.

Justification for type of information:

See IUCLID section 13 for read across justification

Reason / purpose for cross-reference:

read-across source

Qualifier:

according to guideline

Guideline:

other: OPPTS 870.3650, 2000/OECD 422

Deviations:

no

Principles of method if other than guideline:

see section 7.5.1. (Repeated dose toxicity), section 7.6.2. (Genetic toxicity in vivo), section 7.8.1. (Toxicity to reproduction)

GLP compliance:

yes

Limit test:

no

Species:

rat

Strain:

Sprague-Dawley

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Charles River Laboratories, Raleigh, North Carolina
- Age at study initiation: no data
- Weight at study initiation: no data
- Fasting period before study: no data
- Housing: no data
- Diet (e.g. ad libitum): no data
- Water (e.g. ad libitum): no data
- Acclimation period: 16 days

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: To: no data

Route of administration:

oral: gavage

Vehicle:

corn oil

Details on exposure:

PREPARATION OF DOSING SOLUTIONS:
The naphthenic acids were suspended in corn oil to the appropriate concentrations and administered in 10 ml/kg doses.

Analytical verification of doses or concentrations:

not specified

Details on mating procedure:

- M/F ratio per cage: 1:1
- Length of cohabitation: 14 days. All females confirmed to have mated were placed in plastic maternity cages once mating was confirmed.
- Proof of pregnancy: vaginal plug referred to as day 0 of pregnancy
- After 14 days of unsuccessful pairing females were plac- Further matings after two unsuccessful attempts: Females for which copulation was not detected were placed in maternity cages at the end of the 14 day mating period.
- After successful mating each pregnant female was placed in maternity cages once mating was confirmed
- Any other deviations from standard protocol:Length of gestation was calculated as the time from confirmation of mating to the onset of delivery.

Duration of treatment / exposure:

Dosing initiated 14 days prior to pairing and continued throughout the mating and gestational periods until study termination on post-natal day 3. The total number of doses ranged from 39-53 depending on the time at which mating occurred.

Frequency of treatment:

Daily

Duration of test:

39-53 days

Remarks:

Doses / Concentrations:
0, 100, 300, 900 mg/kg/day
Basis:
actual ingested

No. of animals per sex per dose:

12

Control animals:

yes, concurrent vehicle

Maternal examinations:

CAGE SIDE OBSERVATIONS:
- All rats were examined twice daily for mortality and general health.
- All animals were examined approximately 1 hour after each treatment, and all unusual observations were recorded. ed.

DETAILED CLINICAL OBSERVATIONS:
- Time schedule:Detailed physical examinations of all animals were conducted weekly (See Section 7.5.1)

BODY WEIGHT: Yes
- Time schedule for examinations:females: recorded once week prior to test substance administration, on the first day of dose administration and weekly until evidence of copulation was obtained. From that point body weights of female rats were recorded on gestation days (GD) 0, 4, 7, 11, 14, 17, and 20 and on lactation days (LD) 0, 1 and 4 (termination). For females for which there was no evidence of copulation, body weights were recorded weekly until termination.

FOOD CONSUMPTION AND COMPOUND INTAKE (if feeding study): Yes
-Food consumption by adult animals was also recorded on the same schedule as the body weights.

WATER CONSUMPTION: No

POST-MORTEM EXAMINATIONS: Yes
- Sacrifice on gestation day #4, Females for which there was no evidence of mating were sacrificed on post-cohabitation day 25, those that showed evidence of mating but failed to deliver were euthanized on post-mating day 25, and all others were euthanized on post-natal day 4
- An examination of target organs including male and female reproductive organs was also carried out as part of this test (See also Section 7.5.1).
- Organs examined included: ovaries with oviduct, uterus with cervix and vagina, testes with epididymides, prostate and seminal vesicles.
- The ovaries, testes and uteri were weighed and all were examined histologically

OTHER:

Ovaries and uterine content:

The ovaries and uterine content was examined after termination: Yes
Examinations included:
- Gravid uterus weight: No data
- Number of corpora lutea: Yes
- Number of implantations: Yes
- Number of early resorptions: No
- Number of late resorptions: No
- Other:Uteri with no microscopic evidence of implantation were opened and subsequently placed in 10% ammonium sulfide solution for detection of early implantation loss

Fetal examinations:

- External examinations: Yes: all per litter
- Soft tissue examinations: No
- Skeletal examinations: No
- Head examinations: No

Statistics:

Parental mating, fertility, conception and copulation indices were analyzed using the Chi-square test with Yates’ correction (Hollander and Wolfe, 1999). Mean parental body weights (weekly, gestation and lactation), body weight changes and food consumption, offspring body weights and body weight changes, gestation length, numbers of former implantation sites, numbers of corpora lutea, number of pups born, live litter size on PND 0, unaccounted for sites, and pre-coital intervals were evaluated by one-way analysis of variance (ANOVA) (Snedecor and Cochran, 1980) to determine intergroup differences between the vehicle control and test substance-treated groups. If the ANOVA revealed significant (p < 0.05) intergroup variance, Dunnett test (Dunnett, 1964) was used to compare the test substance-treated groups to the control group. Mean litter proportions (percent of litter) of males at birth and post-natal survival were evaluated using the Kruskal-Wallis nonparametric ANOVA (Kruskal and Wallis, 1952) to determine intergroup differences between the vehicle control and test substance-treated groups. If the ANOVA revealed significant (p < 0.05) intergroup variance, Dunn Test (Dunn, 1964) was used to compare the test substance-treated groups to the vehicle control group.

Indices:

See Tables below and in Section 7.8.2.
Mating, fertility, pregnancy and gestation indices were not provided as such, however No. of females mated, pregnant and with litters were given.
Pre-implantation loss not provided, but No. of corpora lutea and No. of implantation sites given.
Implanation index not provided, but No. of implanatation given.
Post-implantation indexes given.

Details on maternal toxic effects:

Maternal toxic effects:no effects

Details on maternal toxic effects:
Althouth it was mentionned above that NOAEL for maternatl toxicity is 900 mg/kg bw, the toxicty part of this experiment learned that systemic toxicity and target organs were identified at 300 and 900 mg/kg bw. Therefore, it can be considered that there was maternal toxicity.

Dose descriptor:

NOAEL

Effect level:

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

Based on:

test mat.

Basis for effect level:

other: maternal toxicity

Dose descriptor:

NOAEL

Effect level:

ca. 300 mg/kg bw/day (actual dose received)

Based on:

test mat.

Basis for effect level:

other: developmental toxicity

Dose descriptor:

NOAEL

Effect level:

ca. 100 mg/kg bw/day (actual dose received)

Based on:

test mat.

Basis for effect level:

other: developmental toxicity

Dose descriptor:

NOAEL

Effect level:

ca. 300 mg/kg bw/day (actual dose received)

Based on:

test mat.

Basis for effect level:

other: developmental toxicity

Details on embryotoxic / teratogenic effects:

Embryotoxic / teratogenic effects:no effects

Dose descriptor:

NOAEL

Effect level:

ca. 300 mg/kg bw/day (actual dose received)

Based on:

test mat.

Sex:

not specified

Basis for effect level:

other: developmental toxicity: offspring delivered

Dose descriptor:

NOAEL

Effect level:

ca. 100 mg/kg bw/day (actual dose received)

Based on:

test mat.

Sex:

not specified

Basis for effect level:

reduction in number of live offspring

Dose descriptor:

NOAEL

Effect level:

ca. 300 mg/kg bw/day (actual dose received)

Based on:

test mat.

Sex:

not specified

Basis for effect level:

fetal/pup body weight changes

Abnormalities:

not specified

Developmental effects observed:

not specified

There were no apparent effects on mating. A single female in the 300 mg/kg/day group had a pre-coital interval of 13 days, resulting in a statistically significant increase in pre-coital incidence in this group. Otherwise all of the pairs productively mated and pre-coital intervals were within the historical control range for the laboratory. Note that there was a significant increase in pre-coital interval in the 300 mg/kg group, but this was due to a single female, and, as noted was within the historical range of the laboratory. Accordingly, it was not considered to have been a treatment-related effect. 

The length of the gestational period was similar across the groups. There were reductions in the numbers ofcorpora luteaand implantation sites in the high dose group, but the differences were not statistically significant (see Table 1 below). However, there was a significant reduction in the number of offspring born/litter in the high dose group (Table 2). There was also a significant reduction in survival in offspring in the high dose group, and those that did survive had significantly lower body weights than the offspring in the control groups. The number of pups found dead or euthanizedin extremis during the period PND 0-4 was: control = 1(1), 100 mg/kg/day = 0(0), 300 mg/kg/day = 12(5), and 900 mg/kg/day = 38(8).  

Table 1. Summary of reproductive parameters assessed in the repeated dose/reproductive toxicity study of refined naphthenic acids

Dose (mg/kg/day)	Corn Oil Control	100 mg/kg/day	300 mg/kg/day	900 mg/kg/day
Number of females paired	12	12	12	12
Number of female mated	12	12	10	11
Number of females pregnant^a	9	12	10	11
Number of females with litters	9	12	10	11
Pre-coital interval (days)^b	1.4+0.7	2.3+1.1	4.2+3.3*	3.8+3.5
Gestation length (days)	21.4+0.6	21.9+0.3	22.0+0.5	22.1+0.5
Corpora lutea	15.6+2.3	14.0+1.4	15.1+3.0	13.8+2.1
Implantation sites	15.0+2.4	13.6+1.1	13.0+1.2	12.2+3.7
Number born	14.1+1.9	12.9+1.1	12.0+1.6	10.8+3.8^c
Post-Implantation loss (%)^d	6.0	5.1	7.7	11.5

a. Pregnant = uterine implantation sites.

b. Data summarized as mean+standard deviation.

c. p < 0.05

d. Post-implantatoin loss = (No. of implantations - No. of life fetuses)/No. of implanatations (%)

 

Table 2. Survival, viability and growth of offspring followingin uteroexposure to refined naphthenic acids. The data are given as mean+SD.

Dose (mg/kg/day)	Corn Oil	100 mg/kg/day	300 mg/kg/day	900 mg/kg/day
Number of viable litters	9	12	10	11
Number of pups born alive/litter	13.9+1.9	12.9+1.1	10.1+4.0^a	9.6+4.0^b
Percentage of pups surviving from birth to termination        ( PND 4)	98.1+3.8	100.0+0.0	88.0+24.5	67.7+40.6
Pups (litters) found dead or euthanizedin extremis	1(1)	0(0)	12(5)	38(8)
Sex ratio (% males/litter)	58.9+9.6	53.9+9.6	55.2+19.1	58.1+22.7
Pup weight PND 1 – males	7.0+0.5	6.7+0.7	6.7+0.5	5.7+0.8^a
Pup weight PND 1 – females	6.6+0.6	6.5+0.6	6.4+0.4	5.6+1.1
Pup weight PND 4 – males	9.7+1.1	9.4+1.2	9.4+0.9	7.2+1.5^b
Pup weight PND 4 – females	9.1+1.0	9.0+1.0	8.8+0.7	7.3+1.5^b

a. p < 0.05, b. p < 0.01

Conclusions:

Treatment of Sprague-Dawley rats with refined naphthenic acids had no apparent effects on mating and did not produce malformations at the highest dose tested (900 mg/kg/day). However, there were significant reductions in number of offspring, number live born and offspring body weights. The overall no observed adverse effect level was 100 mg/kg/day.

Executive summary:

A combined repeated dose toxicity study with the reproduction/developmental toxicity screening test in Wistar ratswas performed by oral gavage with Naphtenic acids in corn oil. There were 3 test material treated groups (100, 300 and 900 mg/kg bw) along with a vehicle treated group (corn oil) each in 12 animals/sex/group. Male rats were dosed during premating, mating and afterwards for 28 days in total and females were dosed during premating, mating, gestation and up to day 3 post partum. In this section, only developmental toxicity parameters are discussed: (furher info on repeated & reproductive parameters is given in Section 7.5.1 and 7.8.1). Target organ findings were identified at the dose of 300 and 900 mg/kg bw, whereas 100 mg/kg bw was considered as the NOAEL for systemic toxicity.

Treatment of Sprague-Dawley rats with refined naphthenic acids had no apparent effects on mating and did not produce malformations at the highest dose tested (900 mg/kg/day). However, there were significant reductions in number of offspring, number live born and offspring body weights. The overall no observed adverse effect level was 100 mg/kg/day.

Reference 2

Endpoint:

developmental toxicity

Type of information:

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

Adequacy of study:

key study

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: GLP-compliant, guideline study, available as an unpublished study report. Acceptable for assessment.

Justification for type of information:

Please see the Read Across Justification Documents in Section 13 of IUCLID dossier.

Reason / purpose for cross-reference:

read-across source

Qualifier:

according to guideline

Guideline:

other: OECD Guideline 422 (Combined Repeated Dose Toxicity Study with the Reproduction / Developmental Toxicity Screening Test)

Deviations:

no

GLP compliance:

yes

Limit test:

no

Species:

rat

Strain:

Sprague-Dawley

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Charles River Laboratories
- Age at study initiation: approx. 8 weeks
- Weight at study initiation: Males - 266-311g; Females (nulliparous and nonpregnant) - 191-222g
- Housing: Individually housed in suspended, stainless steel, wire-mesh type cages, except during pairing, near parturition and during lactation. P females moved to plastic caging with wood chip bedding from GD20 - LD 4. Animal enrichment per SOP-ACU-89
- Diet (e.g. ad libitum): Lab Diet Certified Rodent Diet #5002, PMI Nutrition International, Inc., ad libitum.
- Water (e.g. ad libitum): ad libitum
- Acclimation period: 1 week

ENVIRONMENTAL CONDITIONS
- Temperature (°F): 64-79
- Humidity (%): 30-70
- Photoperiod (hrs dark / hrs light): 12 h /12 h

IN-LIFE DATES: From: 30 November 2010 to 1 Febraury 2011

Route of administration:

dermal

Vehicle:

water

Details on exposure:

TEST SITE
- Area of exposure: Dorsal surface; equivalent to approx. 10% of the total body surface area
- Type of wrap if used: Gauze dressing and non-absorbent cotton covered with self-adhesive tape and athletic tape.
- Time intervals for shavings or clipplings: As required

REMOVAL OF TEST SUBSTANCE
- Washing (if done): Wypall wet with distilled water.
- Time after start of exposure: 6 h

TEST MATERIAL
- Amount(s) applied (volume or weight with unit): 2.5 mL/kg
- Concentration (if solution): equivalent to 0; 100; 300; 1000 mg/kg/day (nominal)
- Constant volume or concentration used: Yes


VEHICLE
- Distilled deionised tap water
- Concentration (if solution): N/A
- Lot/batch no. (if required): Not available
- Purity: Not available

USE OF RESTRAINERS FOR PREVENTING INGESTION: No

Analytical verification of doses or concentrations:

yes

Details on analytical verification of doses or concentrations:

The concentrations of fatty acids C18-(unsaturated) lithium salts in 52 dosing formulation samples was established by determining lithium content by Inductively Couple Plasma Optical Emission Spectroscopy (ICP-OES). Samples were processed by microwave aided acid digestion (DIN 51460-2) before submitting to ICP-OES (EN ISO 11885).

Details on mating procedure:

After 2 weeks of treatment, P animals (Groups 1 to 4), each female was housed in cage of a male from the same treatment group.
- M/F ratio per cage: 1
- Length of cohabitation: Until evidence of copulation was established (max 14 days). Housed individually during daytime 6-hour exposure period.
- Proof of pregnancy: vaginal plug and / or vaginal lavage with the presence of sperm; referred to as gestation day (GD) 0
- After 14 days of unsuccessful pairing females were returned to individual cages.
- After successful mating each pregnant female was caged individually for the remainder of the study.

Duration of treatment / exposure:

Males dosed for at least 43 days, beginning 14 days prior to mating (Groups 1-4).
Dosing of the females began 14 days prior to mating and continued through mating, up to and including GD 19 (Groups 1-4). Another set of animals (Groups 5 and 6) were dosed for a total of 43 days and then began a 14-day (non-treated) recovery period.

Frequency of treatment:

Daily, once per day for 6 hours.

Duration of test:

Terminal Groups (Groups 1 to 4): Dosed for at least 43 days
Recovery Groups (Groups 5 and 6): Dosed for a total of 43 days before beginning a 14-day (non-treated) recovery period

No. of animals per sex per dose:

Terminal Groups (Groups 1 to 4): 10 animals per sex per dose
Recovery Groups (Groups 5 and 6): 5 animals per sex per dose

Control animals:

yes, concurrent vehicle

Details on study design:

- Dose selection rationale: The dose levels were selected on the basis of available data from a previous dose ranging study (MPI Study No. 1883-001). Animals were dosed dermally once a day at 0, 525, 1050 and 2100 mg/kg bw/day (water based Fatty acids C18-(unsaturated) lithium salts) and for two weeks at 2106 mg/kg bw/day with oil-based Fatty acids C18-(unsaturated) lithium salts. The results of this study identified significant dose responsive dermal effects, based on maximized erythema and eschar scores at dose levels ≥1050 mg/kg bw/day fatty acids C18-(unsaturated) lithium salts. A slight decrease in mean body weight was noted in males during the last week of dosing, however, not other adverse body weight or food consumption effects were observed at the dose levels tested. A nominal high-dose level of 1000 mg/kg bw/day (at a slightly lower concentration based on dose volume) was selected for the defintive study to insure some morbidity. The nominal low dose level (100 mg/kg bw/day) was selected with 10-fold decrease to insure a no effect level, and a nominal mid-dose level of 300 mg/kg bw/day was selected to be about 3 times higher than the low-dose level and about 3 times lower than the high-dose level.
- Rationale for animal assignment (if not random): All animals placed on study will have body weights that fall within 20% of the mean bodyweight for each sex. Animals considered suitable for study will be weighed prior to treatment. After the appropriate number of animals with the highest and lowest body weights has been excluded, the remaining required number of animals on study will be randomized, by sex, into treatment groups using a standard, by weight, measured value randomization procedure
- Rationale for selecting satellite groups: As above
- Post-exposure recovery period in satellite groups: 14-day non treatment period
- Section schedule rationale (if not random): Randomized

Maternal examinations:

CAGE SIDE OBSERVATIONS: Yes
- Time schedule: At least twice a day, 7 days a week, for morbidity, mortality, injury, and availability of food and water. Towards end of gestation period, P females examined twice daily for signs of parturition.
- Cage side observations recorded are not reported, but are maintained in the study file.

DETAILED CLINICAL OBSERVATIONS: Yes
- Time schedule: Daily during the study (after wrap removal on dose days).

DERMAL IRRITATION: Yes
- Time schedule for examinations: Prior to first dose and daily during the study (after wrap removal on dosing days).

BODY WEIGHT: Yes
- Time schedule for examinations: Weekly during the study. Mated females weighed on GD 0, 7, 14 and 20 and on LD 0 and 4 and at termination.

FOOD CONSUMPTION:
- Food consumption for each animal determined and mean daily diet consumption calculated as g food/kg body weight/day: Yes

WATER CONSUMPTION: No

OTHER:
HAEMATOLOGY: Yes
- Time schedule for collection of blood: At termination / at recovery
- Anaesthetic used for blood collection: Yes (CO2)
- Animals fasted: No
- How many animals: 5 per sex per group (P animals) in Groups 1-4 at Termination (same animals designated for behavioral testing). 5 per sex per group in Groups 5 and 6 at Recovery
- Parameters checked: Leukocyte count (total and absolute differential); erythrocyte count; hemoglobin; hematocrit; mean corpuscular hemoglobin, mean corpuscular volume, mean corpuscular hemoglobin concentration (calculated); absolute reticulocytes; platelet count; blood cell morphology

CLINICAL CHEMISTRY: Yes
- Time schedule for collection of blood: At termination / at recovery
- Animals fasted: No
- Number of animals: 5 per sex per group (P animals) in Groups 1-4 at Termination (same animals designated for behavioral testing). 5 per sex per group in Groups 5 and 6 at Recovery
- Parameters checked: Alkaline phosphatase; total bilirubin (with direct bilirubin if total bilirubin exceeds 1 mg/dL); aspartate aminotransferase; alanine aminotransferase; gamma glutamyl transferase; sorbitol dehydrogenase; urea nitrogen; creatinine; total protein; albumin; globulin and A/G (albumin/globulin) ratio (calculated); glucose; total cholesterol; triglycerides; electrolytes (sodium, potassium, chloride); calcium; phosphorus

Ovaries and uterine content:

No data reported

Fetal examinations:

Litters were examined as soon as possible after delivery(LD 0) and on LD 4. The F1 offspring sacrificed on LD 4 and these animals were subjected to postmortem external examinations.

PARAMETERS EXAMINED
The following parameters were examined in F1 offspring: Litter size, number of stillborn and liveborn pups, survival, number of males and females, individual body weights, abnormal behaviour, and gross abnormalities of the pups.

GROSS EXAMINATION OF DEAD PUPS: Yes, for external abnormalities. Offspring found dead on LD 0 had lungs removed and placed in tap water to determine whether live/stillborn.

Statistics:

The raw data were tabulated within each time interval, and the mean and standard deviation were calculated for each endpoint by sex and group. For each endpoint, treatment groups were compared to the control group using: Group pair-wise comparisons; Cochran Manzel Haenszel test; log transformation / group pair-wise comparisons; Fisher's exact test; Arcsin-square root transformation, and; Covariate analysis.

Indices:

Live Birth Index (%) = (No. live pups at birth / No. pups born) x 100
Stillborn Index = No. stillborn pups / No. pups born
Viability Index – Day 4 (%) = (No. pups surviving 4 days (preculling) / No. live pups at birth) x 100

Historical control data:

No data reported

Details on maternal toxic effects:

Maternal toxic effects: No effects
Reproductive parameters (male/female fertility and fecundity indices, and copulatory intervals) were unaffected by treatment. No statistically significant changes in delivery data and pup development / survival.

Details on maternal toxic effects:
- Clinical signs (parental animals): 345 and 1089.75 mg/kg bw/day: localized scabbed area on dorsal surface and scabbed area in the thoracic region (related to test site) during dosing period. Recovery animals indicated trend towards recovery after cessation of dosing.
- Body weight and food consumption (parental animals): Trend to decreasing mean body weight in males at 1089.75 mg/kg bw/day - though not statistically significant. Mean body weight change was statistically decreased in treated males at 1089.75 mg/kg bw/day during the premating interval from Weeks 1 to 3.
- Test substance intake (parental animals): Not examined
- Reproductive function: Estrous cycle (parental animals): Not examined
- Reproductive function: Sperm measures (parental animals): Not examined
- Reproductive performance (parental animals): Male/female fertility and fecundity indices and copulatory intervals unaffected by treatment.
- Organ weights (parental animals): Relative mean spleen weight increased in 1089.75 mg/kg/d males. Considered to be secondary adaptive response to localised dermal effects
- Gross pathology (parental animals): Test article-related macroscopic findings (terminal necropsy): minimal to moderate abrasion/scab formation in control males and treated animals of both sexes. Dose-related increase in incidence/severity in females (all doses) and males (345-1089 mg/kg/d)
- Histopathology (parental animals): Test article-related microscopic findings in skin: minimal/moderate erosion/ulceration, epidermal hyperplasia and exudate, minimal/mild acute/subacute/chronic inflammation, minimal edema. 1000 mg/kg/day: secondary adaptive findings in thymus and spleen.

Dose descriptor:

NOAEL

Remarks:

Generation P male/female

Effect level:

> 1 089.75 mg/kg bw/day (actual dose received)

Based on:

test mat.

Basis for effect level:

other: maternal toxicity

Remarks on result:

not determinable due to absence of adverse toxic effects

Dose descriptor:

NOAEL

Remarks:

Generation P male/female

Effect level:

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

Based on:

test mat.

Basis for effect level:

other: NOAEL for local effects at test site based on observations: minimal to moderate erosion/ulceration, epidermal hyperplasia and exudate; minimal to mild acute to subacute/chronic inflammation; and minimal edema at 300 and 1000 mg/kg bw/day dose groups.

Remarks on result:

other: The 1000 mg/kg bw/day recovery group animals indicated partial resolution of these findings following the 14 day recovery period.

Details on embryotoxic / teratogenic effects:

Embryotoxic / teratogenic effects:no effects

Details on embryotoxic / teratogenic effects:
No reproductive effects or definitive test-article related changes in the development or survival of the offspring.

- Viability (offspring): No effects
- Clinical signs (offspring): No effects
- Body weight (offspring): No effects
- Sexual maturation (offspring): Not examined
- Organ weights (offspring): Not examined
- Gross pathology (offspring): No effects
- Histopathology (offspring): Not examined
- Details on results (offspring): There were no treatment-related effects at any dose level on any of the reproductive parameters evaluated in this study including offspring survival (gestation and postnatal survival indices, percent pre- and post-implantation loss), pup body weight and pup sex ratio. There were also no treatment-related effects on any of the developmental parameters evaluated including external abnormalities, number of live and still births, mortality, sex determination and weights of pups.

Dose descriptor:

NOAEL

Effect level:

> 1 089.75 mg/kg bw/day (actual dose received)

Based on:

test mat.

Sex:

male/female

Basis for effect level:

other: No reproductive effects or definitive test-article related changes in the development or survival of the offspring.

Abnormalities:

not specified

Developmental effects observed:

not specified

Dermal application of fatty acids C18-(unsaturated) lithium salts to the dorsal surface of Parental male and female rats at dose levels of 100, 300, and 1000 mg/kg bw/day did not result in any adverse reproductive effects or any definitive test article-related changes in the development or survival of the offspring.

In addition, results from the clinical pathology evaluations and neurobehavioral testing did not reveal any definitive effects that could be attributed to treatment at the dose levels tested. Test article-related dermal changes were limited to local effects at the test site for Parental animals at 300 and 1000 mg/kg bw/day, which showed a decreasing trend following cessation of dosing in the designated recovery animals. Microscopic evaluation of the skin at the test site showed minimal to moderate erosion/ulceration, epidermal hyperplasia and exudate, minimal to mild acute to subacute/chronic inflammation and minimal edema, which confirmed the macroscopic findings. At recovery necropsy, test article-related microscopic findings in treated skin in animals at 1000 mg/kg bw/day were morphologically similar, although they occurred at a lower incidence and severity indicating partial resolution of these findings following the recovery period. Microscopic findings of splenic extramedullary hematopoiesis and thymic lympoid depletion noted at 1000 mg/kg bw/day were considered to be secondary adaptive responses to parturition and localized dermal effects.

Systemic effects were limited to changes in body weight and organ weight at 1000 mg/kg bw/day, the highest dose level tested.

In summary, there were no treatment related effects at any dose level on any of the reproductive parameters evaluated in this study, or in any of the developmental parameters evaluated. Based on these daya, the NOAEL for developmental toxicity was >1089.75 mg/kg bw/day and the NOAEL for reproductive toxicity was also >1089.75 mg/kg bw/day.

Conclusions:

Dermal application of fatty acids C18-(unsaturated) lithium salts to the dorsal surface of Parental male and female rats at dose levels of 100, 300, and 1000 mg/kg bw/day did not result in any adverse reproductive effects or any definitive test article-related changes in the development or survival of the offspring.

Executive summary:

The developmental toxicity of fatty acids C18 (unsaturated) lithium salts was assessed in a combined repeated dose and reproductive toxicity screening test following OECD guideline 422 (MPI 2011). The parental generation was dermally administered daily for 6 hours per day with fatty acids C18 (unsaturated) lithium salts at concentrations of 100, 300 and 1000 mg/kg bw/day. The offspring of the treated rats were then assessed for survival (gestation and postnatal survival indices, percent pre- and post-implantation loss), pup body weight and sex ratio and external abnormalities.

Effect on developmental toxicity: via oral route

Endpoint conclusion:

adverse effect observed

Dose descriptor:

NOAEL

100 mg/kg bw/day

Study duration:

subacute

Species:

rat

Quality of whole database:

Guideline study conducted to GLP.

Effect on developmental toxicity: via inhalation route

Endpoint conclusion:

no study available

Effect on developmental toxicity: via dermal route

Endpoint conclusion:

no adverse effect observed

Dose descriptor:

NOAEL

1 089.75 mg/kg bw/day

Study duration:

subacute

Species:

rat

Quality of whole database:

Guideline study conducted to GLP.

Additional information

There are no data for lithium naphthenate. Data from appropriate read across substances are presented, with data on fatty acids C18 (unsaturated) lithium salts and naphthenic acids.

 

Fatty acids C18 (unsaturated) lithium salts

A key toxicity and reproductive toxicity screen, using the OECD 422 study design, was conducted in rats on fatty acids C18 (unsaturated) lithium salts via dermal administration. The test material was administered at dose levels of 0, 100, 300 and 1000 mg/kg/day nominal, equating to 111.25, 345 and 1089.75 mg/kg/day by analysis, and were based on local dermal effects from a dose range finding study. There were no treatment-related effects at any dose level on any of the reproductive parameters evaluated in this study, or in any of the developmental parameters evaluated. Based on these data, the NOAEL for reproductive and developmental toxicity was 1089.75 mg/kg/day.

 

The consideration concerning the margin of safety between the human therapeutic dose and the NOAELs found in the relevant studies is presented in the Repeated Dose Toxicity section above. The same proposals regarding the use of the human data for DNEL derivation are applicable for the developmental toxicity endpoint.

 

The use of lithium in bipolar disorder has been reviewed by Horton et al (2012). This disease is more prevalent in women and is often concurrent with peak reproductive age. This review considers a therapeutic regimen based on PBPK modelling, simulating the concentration of lithium in the organs and tissues of a pregnant woman and her foetus. In the USA, lithium has been classified as a Class D drug (legal to use during pregnancy, but may cause birth defects). The maximum dosage regimen suggested by the modelling based on avoidance of any adverse developmental sequelae was 400 mg lithium carbonate, three times per day (1200 mg/day). This is slightly higher than the lithium carbonate treatment levels of 450 – 900 mg/day referred to in the Repeated dose toxicity discussion, section 5.6.3. Therefore, this paper presents further evidence, based on PBPK modelling, that the use of human therapeutic data is a valid approach for consideration of a human NOAEL and DNEL based on serum concentrations during long-term therapy.

 

The fatty acid anions of fatty acids C18 (unsaturated) lithium salts are not considered to be hazardous under anticipated exposure conditions, and under certain conditions would be exempt from registration. Any hazard would be expected to be driven by the lithium cation. On this basis, prenatal developmental toxicity data generated on a soluble inorganic lithium salt would be appropriate to read across to the lithium naphthenate.

 

Naphthenic acids

In a combined repeated dose toxicity and reproduction/developmental toxicity screening study, conducted according to OECD Test Guideline 422 and to GLP, Sprague-Dawley rats (12/sex/group) were orally administered a mixture of naphthenic acids by stomach tube (gavage, in corn oil) at doses of 0, 100, 300 or 900 mg/kg bw/day. Males were dosed for 28 days (during the pre-mating, mating and post-mating periods) and females were dosed through pre-mating, mating, gestation and up to day 3 post partum (39-53 days in total). A significant reduction in the number of live born pups was observed in the mid- and high-dose groups. The number of offspring and offspring body weights were also significantly reduced at the highest dose. Treatment with naphthenic acids did not produce malformations. The developmental NOAEL was considered to be 100 mg/kg/day (HPVIS, 2010). [See Repeated dose toxicity and Effects on fertility sections for further details].

 

In a non-guideline study, female Wistar rats (13-14/group) were gavaged with a mixture of naphthenic acids (isolated from Athabasca oil sands, in corn oil) at doses of 0, 6 or 60 mg/kg bw/day for a total of 39-53 days (through pre-mating, mating, gestation and up to post natal day 3). No malformations were apparent in the offspring (Rogers, 2003). [See Effects on fertility section for further details].

 

Conclusion

As the NOAEL of 100 mg/kg bw/day for naphthenic acids is lower than the NOAEL for the lithium cation (NOAEL of 1089.75 mg/kg bw/day read across from fatty acids C18 (unsaturated) lithium salt), this value was taken as a worst-case scenario. As the molecular weight of the lithium salt of naphthenic acids is greater than the molecular weight of naphthenic acids themselves, the NOAEL of 100 mg/kg bw/day was applied directly to lithium naphthenate.

Justification for classification or non-classification

Not classified. Available data suggest no classification for reproductive and developmental toxicity.