6-hydroxy-2-naphthoic acid

Endpoint summary

Description of key information

Oral study was performed using the read-across substance, 3-hydroxy-2-naphthoic acid.  Inhalation study was performed using the substance of record, 6-hydroxy-2-naphthoic acid.

Key value for chemical safety assessment

Repeated dose toxicity: via oral route - systemic effects

Link to relevant study records

Reference

Endpoint:

short-term repeated dose toxicity: oral

Type of information:

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

Adequacy of study:

key study

Study period:

1988-10-5 - 1989-08-03

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Limited scope of clinical/organ/tissue examinations and of functional observational battery; Apart from that, well documented and reported study, conducted according to OECD 407 test guideline of 1981 and in compliance with GLP.

Qualifier:

according to guideline

Guideline:

OECD Guideline 407 (Repeated Dose 28-Day Oral Toxicity Study in Rodents)

Version / remarks:

of 1981

Deviations:

no

GLP compliance:

yes

Limit test:

no

Species:

rat

Strain:

Wistar

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Hoechst AG breeding colony
- Age at study initiation: ca. 6 weeks
- Weight at study initiation (day -4): mean male: 101 g, female: 96 g
- Fasting period before study: none
- Housing: groups of 5, macrolon cages
- Diet (e.g. ad libitum): rat diet Altromin 1324, ad libitum
- Water (e.g. ad libitum): tap water, ad libitum
- Acclimation period: at least 5 days

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 22 +/-3
- Humidity (%): 50+/- 20
- Photoperiod (hrs dark / hrs light): 12/12

Route of administration:

oral: gavage

Vehicle:

other: aqueous carboxymethyl cellulose

Details on oral exposure:

The administration volume was 5 ml/kg bodyweight at all dose levels. Hence the concentration of test substance in the aqueous CMC preparation (vehicle) administered was 0.00, 0.24, 1.20 and 6.00 % (w/v) in the vehicle control, low dose, mid dose and high dose groups, respectively.

Analytical verification of doses or concentrations:

no

Duration of treatment / exposure:

28 applications in 29 days.

Frequency of treatment:

7days per week

Remarks:

Doses / Concentrations:
0, 12, 60, 300 mg/kg bw/day (mf)
Basis:
actual ingested

No. of animals per sex per dose:

5

Control animals:

yes, concurrent vehicle

Positive control:

Not available

Observations and examinations performed and frequency:

Clinical observations: twice daily.
Functional observations (not specified), and examination of eyes, oral cavity and teeth: at weekly intervals.
Body weights: determined at beginning of the study and then twice per week.
food consumption: determined twice per week.
water consumption: determined once per week.
Haematology/Clinical chemistry/Urinalysis: at study end from all animals.

Sacrifice and pathology:

All animals were killed on day 29 after 28 consecutive days of oral (gavage) treatment.
Organ weights and organ to body weight ratios determined: heart, lung, liver, kidneys, spleen, testes, adrenals.
Organs/tissues examined at necropsy (macroscopic and microscopic): heart, lung, liver, kidneys, spleen, stomach, jejunum, colon, thymus, testes, adrenals, bone marrow.

Other examinations:

No

Statistics:

Not specified, significance level p= 0.05

Clinical signs:

no effects observed

Mortality:

no mortality observed

Body weight and weight changes:

no effects observed

Food consumption and compound intake (if feeding study):

no effects observed

Food efficiency:

not specified

Water consumption and compound intake (if drinking water study):

effects observed, treatment-related

Description (incidence and severity):

water consumption increased at 300 mg/kg at day 7 and day 14

Ophthalmological findings:

not specified

Haematological findings:

no effects observed

Clinical biochemistry findings:

effects observed, treatment-related

Description (incidence and severity):

Phosphate decreased , bilirubin increased at 300 mg/kg bw . Although values were within the range of historical controls they are considered to be substance related because of the distinct deviation from the concurrent control.

Urinalysis findings:

effects observed, treatment-related

Description (incidence and severity):

bilirubin (ca 35 µmol/L) in female at 300 mg/kg bw

Behaviour (functional findings):

no effects observed

Organ weight findings including organ / body weight ratios:

effects observed, treatment-related

Description (incidence and severity):

slightly increased liver weight in females at 300 mg/kg bw

Gross pathological findings:

effects observed, treatment-related

Description (incidence and severity):

adrenal gland findings in females at 60 and 300 mg/kg bw

Histopathological findings: non-neoplastic:

effects observed, treatment-related

Description (incidence and severity):

necrosis of adrenal cortex in one female at 60 mg/kg bw and in one female at 300 mg/kg bw

Histopathological findings: neoplastic:

not specified

Dose descriptor:

NOEL

Effect level:

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

Based on:

test mat.

Sex:

male

Basis for effect level:

other: At 300 mg/kg/day decreased serum phosphate level (toxiccological relevance of this finding is unclear), increased bilirubin concentration in serum and urine but without microscopic correlates in the liver.

Dose descriptor:

NOEL

Effect level:

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

Based on:

test mat.

Sex:

female

Basis for effect level:

other: see 'Remark'

Critical effects observed:

not specified

The administration of the test substance had no influence on body weights, food consumption and behaviour of the animals. No mortality was observed. There were no neurological impairments, no eye opacities and no pathological findings in the oral cavity or teeth. 300 mg/kg bw: an increased water consumption was observed during the first two study weeks; at the end of the study, a significant decrease in serum phosphate, and an increase in serum bilirubin levels were observed when compared to the controls (the levels were within the normal range of the historical controls). In both sexes, bilirubin was found in the urine (ca. 35 µmol/L) and serum. Females showed a slight, but statistically significant increase in liver to bodyweight ratios (without histopathological correlate)(no further details available). At histopathology, one out of five females of the high-dose and one out of five female of the mid-dose group showed adrenal necroses. Examination of the animal from the intermediate dose group revealed diffuse necrosis of the right adrenal cortex. Complete necrosis of the adrenal cortex was detected in the female of the high dose group. Liver fibrosis, and changes in the lobular structure were microscopically seen in one of the females of the low-dose group, but considered as a chance event due to the lack of a dose-response.

Conclusions:

For male animals the no-observed-effect-level (NOEL) was set at 60 mg/kg/day, because of decreased serum phosphate levels (toxicological relevance of this finding is unclear) and increased bilirubin concentration in serum and urine (but without microscopic correlates in the liver). For female animals the no-observed-effect-level (NOEL) was set at 12 mg/kg/day, mainly because of necroses of the adrenal cortex in one female each at 60 and 300 mg/kg/day. In addition, at 300 mg/kg decreased serum phosphate levels, increased bilirubin concentration in serum and urine and slightly increased liver to bodyweight ratios (but without histopathological correlates in the liver) were evident.

Executive summary:

Rats (5 males and 5 females/dose group) were treated by oral gavage administration with 3-Hydroxy-2-naphthoic acid at dose levels of 0, 12, 60 or 300 mg/kg bodyweight/day once daily, seven days/week over 28 days. All animals were killed after 28 treatment days (day 29). At regular intervals during the study, eyes, oral cavities and teeth were examined and clinical signs, functional observations (not specified), body weights, food consumption and water consumption were recorded. In addition, at the end of the study, haematology, clinical chemistry and urinalysis examinations were performed on all animals. Organ weights were determined and macroscopic pathology and histopathology were performed on a number of organs/tissues from all animals.

Bodyweight, food consumption and animal behavior were unaffected by treatment with the test substance and mortality, neurological impairment, eye opacities and pathological findings in oral cavity or teeth were not evident at all dose levels. At 12 mg/kg/day, no signs of toxicity attributable to treatment with the test substance were evident. At 60 mg/kg/day, male animals were unaffected by treatment, whereas a relationship of necroses in the adrenal cortex in one female at 60 and one female at 300 mg/kg/day to treatment with the test item could not be entirely discounted. In addition, at 300 mg/kg/day a transient increase in water consumption, decreased serum phosphate levels and increased bilirubin concentrations in serum and urine were evident in both sexes and slightly increased liver to body weight ratios in females. Histopathological hepatic correlates were not evident.

The no-observed-effect-level (NOEL) was 60 mg/kg/day for male animals and 12 mg/kg/day for female animals.

Endpoint conclusion

Endpoint conclusion:

adverse effect observed

Dose descriptor:

NOAEL

12 mg/kg bw/day

Study duration:

subacute

Species:

rat

Repeated dose toxicity: inhalation - systemic effects

Link to relevant study records

Reference

Endpoint:

repeated dose toxicity: inhalation

Remarks:

other: Repeated Dose via inhalation

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: No GLP statement; However, is a well-conducted, well-documented study with Quality Assurance oversight.

Qualifier:

no guideline followed

Principles of method if other than guideline:

This was a repeated-dose study with daily exposure 6 hours/day, 5 days/week for 2 weeks.

GLP compliance:

no

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 Breeding Laboratories, Kingston, NY
- Age at study initiation: Males, 42 days; Females, 58 days.
- Weight at study initiation: Males, 200 g mean (range 189-214g); Females, 187 g mean (178-197g)
- Fasting period before study: Not stated
- Housing: Individual in stainless steel, wire mesh cages, during both exposure and non-exposure periods.
- Diet (e.g. ad libitum): Purina Rodent Laboratory Chow ad libitum during non-exposure period, no food during exposure.
- Water (e.g. ad libitum): city tap water (Elizabethtown Water Co.) ad libitum during non-exposure period, no water during exposure.
- Acclimation period: 2 weeks.

ENVIRONMENTAL CONDITIONS
- Temperature (°C): Not stated.
- Humidity (%): Not stated.
- Air changes (per hr): Chambers operated at an airflow rate between 155 - 257 liters per minute, giving one complete air change every 6.5 to 3.9 minutes.
- Photoperiod (hrs dark / hrs light):

IN-LIFE DATES: From: 30 March 1981 To: 10 April 1981

Route of administration:

inhalation: dust

Type of inhalation exposure:

whole body

Vehicle:

air

Remarks on MMAD:

MMAD / GSD: MMAD for 20 mg/m^3 group was 4.29 micron, with GSD of 2.44.
MMAD for 60 mg/m^3 group was 4.34 micron, with GSD of 2.95.
MMAD for 200 mg/m^3 group was 3.80 micron, with GSD of 3.56.

Details on inhalation exposure:

GENERATION OF TEST ATMOSPHERE / CHAMBER DESCRIPTION
- Exposure apparatus: Exposure chambers were stainless steel and glass construction, with a total volume of one cubic meter and an effective volume of 760 L.
- Method of holding animals in test chamber: Animals were placed in the exposure chamber in individual stainless steel, wire mesh cages.
- Source and rate of air: Dry air, at a back pressure between 3.0 and 6.0 psi was passed through the dust feed mechanism (Wright Dust Feed Cylinder).
- Method of conditioning air: Not stated.
- System of generating particulates/aerosols: Test material was first ground with a mortar and pestle, sieved through a 60-mesh screen, and vacuum dessicated. The test material was then press-packed into a Wright Dust Feed Cylinder using a Carver Hydraulic Press at a pressure of 2000 psi. The packed cylinders were placed on Wright Dust Feed mechanisms mounted on the horizontal portals of the exposure chamber.
- Temperature, humidity, pressure in air chamber: Not stated.
- Air flow rate: Between 155 and 257 liters per minute.
- Air change rate: One complete air change every 6.5 to 3.9 minutes.
- Method of particle size determination: Batelle Cascade Impactor.
- Treatment of exhaust air: Not stated.

TEST ATMOSPHERE
- Brief description of analytical method used: Airborne concentration determined by dividing the amount of material sampled by the total volume of air sampled.
- Samples taken from breathing zone: yes.

Analytical verification of doses or concentrations:

not specified

Duration of treatment / exposure:

6 hours per day.

Frequency of treatment:

5 days a week, for 2 weeks.

Remarks:

Doses / Concentrations:
Air Control
Basis:
nominal conc.

Remarks:

Doses / Concentrations:
19.6 mg/m^3 (20 was target)
Basis:
analytical conc.

Remarks:

Doses / Concentrations:
58.9 mg/m^3 (60 was target)
Basis:
analytical conc.

Remarks:

Doses / Concentrations:
186 mg/m^3 (200 was target)
Basis:
analytical conc.

No. of animals per sex per dose:

5 males/5 females (10 animals total) per dose.

Control animals:

yes

Observations and examinations performed and frequency:

CAGE SIDE OBSERVATIONS: Yes
- Time schedule: Twice daily during exposure and non-exposure periods.

DETAILED CLINICAL OBSERVATIONS: Yes
- Time schedule: Full, recorded physical assessments were performed twice weekly.

BODY WEIGHT: Yes
- Time schedule for examinations: Body weights were determined pre-test, and before and after exposures 1, 5 and 10.

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

WATER CONSUMPTION: No data

OPHTHALMOSCOPIC EXAMINATION: No data

HAEMATOLOGY: Yes
- Time schedule for collection of blood: Collected at terminal sacrifice.
- Anaesthetic used for blood collection: No data
- Animals fasted: No data
- How many animals: All animals.
- Parameters checked: Hemoglobin, Hematocrit, Leukocyte count (total and differential), clotting time, erythrocyte count.

CLINICAL CHEMISTRY: Yes
- Time schedule for collection of blood: Collected at terminal sacrifice.
- Animals fasted: No data
- How many animals: All animals.
- Parameters checked: Blood Urea Nitrogen (BUN), Serum Glutamic Pyruvic transaminase, glucose, total protein.

URINALYSIS: No data

NEUROBEHAVIOURAL EXAMINATION: No data

Sacrifice and pathology:

GROSS PATHOLOGY: Yes
- Organ weights: Adrenal Glands, Heart, Kidneys (paired), Liver, Lungs, Spleen, Testes with epididymides (paired) and Ovaries (paired).
HISTOPATHOLOGY: Yes
- High Dose Group: Trachea, esophagus, lungs, liver, kidneys, eyes, nasal turbinates (3 sections).
- Low and Mid-Dose Groups: Liver.

Statistics:

METHOD FOR BODY WEIGHTS, ORGAN WEIGHTS, ORGAN/BODY WEIGHT RATIOS:
One way ANOVA, followed by a multiple comparison procedure if needed. First, Bartlett's test was performed to determine if groups had equal variance. If variance was equal, parametric procedures were used. If not, non-parametric were used. Parametric procedure was standard ANOVA. Non-Parametric was the Kruskal-Wallis test, and if differences were indicated, a summed rank (Dunn) test was used. A statistical test for trend in the dose level was also performed. For Parametric analyses, a standard regression techniques, with a test for trend, were used. In a Non-Parametric Case, Jonckheere's test was used. The Bartlett's test was performed at the 1%, 2-sided risk level, while all other tests were at the 5% and 1% two-sided risk levels.

METHOD FOR HEMATOLOGY AND CLINICAL CHEMISTRY:
Means were first tested for equal variance. If the variance was equal, a standard, independent, 2-sample t-test was utilized. If the variances differed, Welch's t-test was used. All tests were performed at the 5% and 1%, 2-sided risk levels.

Clinical signs:

no effects observed

Description (incidence and severity):

All animals survived to terminal sacrifice. Increase in dried material around face, and increase in lacrimation observed.

Mortality:

no mortality observed

Description (incidence):

All animals survived to terminal sacrifice. Increase in dried material around face, and increase in lacrimation observed.

Body weight and weight changes:

no effects observed

Food consumption and compound intake (if feeding study):

not specified

Food efficiency:

not specified

Water consumption and compound intake (if drinking water study):

not specified

Ophthalmological findings:

not specified

Haematological findings:

no effects observed

Clinical biochemistry findings:

effects observed, treatment-related

Description (incidence and severity):

Depressed SGPT values in the high-dose females when compared to control. However, values were within normal biological limits, and were therefore not of Toxicological significance.

Urinalysis findings:

not specified

Behaviour (functional findings):

not specified

Organ weight findings including organ / body weight ratios:

effects observed, treatment-related

Description (incidence and severity):

Absolute and relative spleen weights were significantly lower in high-dose females, when compared to controls.

Gross pathological findings:

no effects observed

Histopathological findings: non-neoplastic:

effects observed, treatment-related

Description (incidence and severity):

Increased mitotic activity of parenchymal liver cells was found in all male rats of the high-dose group.

Histopathological findings: neoplastic:

no effects observed

Dose descriptor:

NOAEC

Effect level:

> 60 mg/m³ air

Based on:

other: Expert Opinion

Sex:

male/female

Basis for effect level:

other: see 'Remark'

Critical effects observed:

not specified

Conclusions:

See Executive Summary.

Executive summary:

A two-week inhalation toxicity study was performed with a dust of the test article. Groups of five male and five female Sprague-Dawley derived CD® rats were exposed six hours per day, five days per week for two weeks. The cumulative mean exposure concentrations were 19.6, 58.9, and 186 mg/m³ for Groups II, III and IV, respectively. The aerodynamic mass median diameters were 4.29, 4.34, and 3.80 microns, with mean geometric standard deviations of 2.44, 2.95 and 3.56 for Groups II, III and IV, respectively.

All animals survived the duration of the study. Physical observations of the exposed animals revealed increased instances of dried material around the facial area and lacrimation in Groups III and IV. These observations suggest a treatment-related effect. Body weights, hematology, and clinical chemistry parameters were unremarkable for all exposed animals when compared to the control group.

Absolute and relative spleen weights for females at the high level were lower than control, and may associate with treatment. There were no macro-pathology findings that associated with treatment. Sections of selected tissues were examined microscopically from all rats. Increased mitotic activity of parenchymal liver cells was found in all male rats of the high-dose group. This increase was considered to be related to administration of the test substance.

Other pathomorphologic findings occurred sporadically in control rats as well as test-article exposed rats. They were not related to the administration of the test substance.

Endpoint conclusion

Endpoint conclusion:

adverse effect observed

Dose descriptor:

NOAEC

60 mg/m³

Study duration:

subacute

Species:

rat

Additional information

Repeated Dose - Oral Toxicity:

For male animals the no-observed-effect-level (NOEL) was set at 60 mg/kg/day, because of decreased serum phosphate levels (toxicological relevance of this finding is unclear) and increased bilirubin concentration in serum and urine (but without microscopic correlates in the liver). For female animals the no-observed-effect-level (NOEL) was set at 12 mg/kg/day, mainly because of necroses of the adrenal cortex in one female each at 60 and 300 mg/kg/day. In addition, at 300 mg/kg decreased serum phosphate levels, increased bilirubin concentration in serum and urine and slightly increased liver to bodyweight ratios (but without histopathological correlates in the liver) were evident.

Repeated Dose - Inhalation:

Based on treatment-related advese findings only in the high dose group, the NOAEC was set at 60 mg/m3.

Justification for selection of repeated dose toxicity via oral route - systemic effects endpoint:
For male animals the no-observed-effect-level (NOEL) was set at 60 mg/kg/day, because of decreased serum phosphate levels (toxicological relevance of this finding is unclear) and increased bilirubin concentration in serum and urine (but without microscopic correlates in the liver). For female animals the no-observed-effect-level (NOEL) was set at 12 mg/kg/day, mainly because of necroses of the adrenal cortex in one female each at 60 and 300 mg/kg/day. In addition, at 300 mg/kg decreased serum phosphate levels, increased bilirubin concentration in serum and urine and slightly increased liver to bodyweight ratios (but without histopathological correlates in the liver) were evident.

Justification for selection of repeated dose toxicity inhalation - systemic effects endpoint:
Based on treatment-related advese findings only in the high dose group, the NOAEC was set at 60 mg/m3.

Justification for classification or non-classification

Based on the criteria set forth in REGULATION (EC) No 1272/2008, neither the read-across substance, nor the substance of record meet the criteria for classification for Specific Target Organ Toxicity - Repeated Exposure.