N-vinylformamide

Endpoint summary

Description of key information

Repeated inhalation toxicity (90 days): NOAEC = 50 mg/m³ (BASF AG, 1995). This value served as the point of departure for DNEL derivation.

Key value for chemical safety assessment

Repeated dose toxicity: via oral route - systemic effects

Endpoint conclusion

Endpoint conclusion:

no study available

Repeated dose toxicity: inhalation - systemic effects

Link to relevant study records

Reference

Endpoint:

sub-chronic toxicity: inhalation

Type of information:

experimental study

Adequacy of study:

key study

Study period:

February 21 - June 29, 1994

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: Guideline study (GLP)

Qualifier:

according to guideline

Guideline:

OECD Guideline 413 (Subchronic Inhalation Toxicity: 90-Day Study)

Version / remarks:

; in addition neurotoxicity testing following EPA test guideline (EPA 1985/87)

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: Dr. K. Thomae GmbH, Biberach, FRG
- Age at study initiation: about 7 weeks
- Weight at study initiation: mean males: 307 (287 - 332) g; mean females: 204 (179 - 231) g
- Housing: singel housing in wire cages (type DK III (floor area about 800 cm²) from Becker & Co., Castrop-Rauxel, FRG)
- Diet: KLIBA rat/mouse/hamster laboratory diet 24-343-4, 10 mm pellets (Klingentalmühle AG, Kaiseraugst, Switzerland) ad libitum (except during exposure, motor activity measurements and urine collection)
- Water: Tap water ad libitum (except during exposure, motor activity measurements and urine collection)
- Acclimation period: 7 days

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 20 - 24°C
- Humidity (%): 30 - 70%
- Photoperiod (hrs dark / hrs light): 12 / 12 (6.00 pm - 6.00 am dark; 6.00 am - 6.00 pm light)

Route of administration:

inhalation: vapour

Type of inhalation exposure:

whole body

Vehicle:

other: supply air

Details on inhalation exposure:

GENERATION OF TEST ATMOSPHERE / CHAMBER DESCRIPTION
- Whole-body exposure system: The animals were kept singly in wire cages (DK III) that were located in glass-steel inhalation chambers (volume V= 1.1 m³, BASF AG). In order to accustom the animals to the exposure conditions they were exposed to supply air in whole-body exposure systems on 5 days before the exposure period (preflow period). Thereafter 65 6-hour workday exposures were conducted for all test groups over a time period of 103 days. The animals did not have access to water or feed during the exposure.
- Generation of the inhalation atmospheres: Generator system: continuous infusion pump PERFUSOR (B. Braun), glass evaporator without or with two component atomizer (BASF AG), glass mixing stage (BASF AG), two circulation thermostats (Haake, Huber); Generation procedure: Conditioned supply air (about 50% relative humidity, 22°C) and compressed air were used for the exposure in all test groups. Test group 0 mg/m³: For reaching a chamber temperature comparable to the other test groups, a part of the supply air piping was heated with an electrical heating wire. Test group 10 and 50 mg/m³: The test substance was supplied to the heated glass evaporator at a constant rate by means of the metering pump. It was vaporized with heated compressed air and the developing vapors were passed through a downstream mixing unit before they were mixed with blast air and introduced into the whole-body exposure system. Test group 250 mg/m³: The test substance was sprayed into a counter current of supply air in the heated glass evaporator at a constant rate by means of the metering pump, a two component atomizer and heated compressed air. It was vaporized with heated compressed air and the developing vapors were passed through a downstream mixing unit before they were mixed with blast air and introduced into the whole-body exposure system.
- Air change rate: about 20 times per hour

TEST ATMOSPHERE
- Brief description of analytical method used: gas chromatography (glas column 1 m x 2 mm; separation phase 10% carbowax 20 M)
- Samples taken from breathing zone: yes

Analytical verification of doses or concentrations:

yes

Details on analytical verification of doses or concentrations:

The nominal concentrations were calculated for each exposure level from the test substance consumed and the amount of the supply air used. The concentrations of test substance in the inhalation atmosphere of the test groups 10, 50 and 250 mg/m³ were analyzed by gas chromatography. Daily means were calculated based on 3 (test group 10 mg/m³) or 6 (test group 50 and 250 mg/m³) measured samples. From these daily mean values, mean concentrations and standard deviations for the entire study were derived. The sampling volumes were adjusted to achieve comparable amounts of the test substance in the samples of the different test groups referring to the calibration range.

Duration of treatment / exposure:

103 days

Frequency of treatment:

6 h/working day for 103 days (65 exposures)

Remarks:

Doses / Concentrations:
10, 50 and 250 mg/m³ (3.4, 17 and 86 ppm)
Basis:
other: target conc.

Remarks:

Doses / Concentrations:
14, 69, 371 mg/m³
Basis:
nominal conc.

Remarks:

Doses / Concentrations:
10.1+/-0.89, 50+/-3.3, 253+/-13.0 mg/m³
Basis:
analytical conc.

No. of animals per sex per dose:

15 males and 15 females per dose

Control animals:

other: yes, concurrent vehicle (clean air)

Details on study design:

Post-exposure period: no
- Dose selection rationale: In a 14-day inhalation study (BASF AG, 1986) with concentrations of 450, 150 and 50 mg/m3 (155, 52 and 17 ppm) no clinical symptoms occurred except a slight irritation of the nose during the first few exposure days. Hematological and clinico-chemical examinations
pointed towards liver damage and an anemic process in the mid and high concentrations. Liver damage was substantiated by increased absolute liver weights. Histopathologically an increased glycogen content of the liver in the mid (males only) and the high concentration groups was detected by a
slightly increased PAS reaction. The NOAEC of this study was 50 mg/m³ (17 ppm). Based on the above tests the concentrations were set for the 90-day study. The high concentration was expected to produce impairment of liver and blood as observed in the 14-day study. It was also expected to produce possible neurotoxic effects, if any. The mid concentration should result in marginal effects on liver and blood. The low concentration should represent the NOAEC.

Observations and examinations performed and frequency:

DETAILED CLINICAL OBSERVATIONS: Yes
- Time schedule: A check for dead animals was made daily. The behavior and state of health of the test animals were checked on workdays at least 3 times on exposure days and, as a rule, once during the preflow period and the post-exposure observation day. During exposure only a groupwise examination was possible.

BODY WEIGHT: Yes
- Time schedule for examinations: at the beginning of the preflow period (day -8), on study day -3, study day 0 and then, as a rule, once a week.

OPHTHALMOSCOPIC EXAMINATION: Yes
- Time schedule for examinations: Before the beginning of the preflow period (day -9/-10), the eyes of all animals and at the end of the study (day 94/95), the eyes of the animals of test group 0 mg/m³ (control group) and of test group 250 mg/m³ (high concentration) were examined with an ophthalmoscope, for any changes to the refracting media.

HAEMATOLOGY: Yes
- Time schedule for collection of blood: at the end of application period (study day 103)
- Anaesthetic used for blood collection: No
- Animals fasted: Yes
- How many animals: 10 males and a0 females per dose group
- Examined parameters: leukocytes, erythrocytes, hemoglobin, hematocrit, mean corpuscular volume, mean corpuscular hemoglobin, mean corpuscular hemoglobin concentration, and platelets. The differential blood count and reticulocytes were evaluated visually. Clotting analyses were carried out using a ball coagulometer and the prothrombin time was determined (Hepato Quick's test).

CLINICAL CHEMISTRY: Yes
- Time schedule for collection of blood: at the end of application period (study day 103)
- Animals fasted: Yes (feed was withdrawn from the animals overnight)
- How many animals: 10 males and 10 females per dose group
- Examined parameters: Enzymes: alanine aminotransferase, aspartate aminotransferase, alkaline phosphatase, serum-gamma-glutamyltransferase, and liver-gamma-glutamyltransferase; blood chemistry: sodium, potassium, chloride, inorganic phosphate, calcium, urea, creatinine, glucose, total bilirubin, total protein, albumin, globulins, triglycerides, cholesterol, and magnesium

URINALYSIS: Yes
- Time schedule for collection of urine: Study day 96
- Metabolism cages used for collection of urine: Yes
- Animals fasted: Yes (urine was collected overnight; withdrawal of food and water)
- Examined parameters: volume, color, turbidity, nitrite, pH, protein, glucose, ketones, urobilinogen, bilirubin, blood, specific gravity, and sediment.

NEUROBEHAVIOURAL EXAMINATION: Yes
- Time schedule for examinations: Study days -2, 34, 68 and 98
- Dose groups that were examined: 10 males and 10 females per dose group
- Battery of functions tested: A functional observation battery (FOB) was carried out on the assigned animals. The exposure group, on which FOB was performed, was not exposed on the day of examination. The FOB started with pure observation without influencing the animals, followed by removal from the home cage and open field examinations in a standard arena. Thereafter, sensorimotor tests and reflex tests as well as quantitative measurements were conducted. The examinations were carried out by trained technicians which performed positive control studies as part of their training. The findings were ranked according to the degree of severity, if applicable. In order to ensure that the observer was unaware of the treatment groups the tatoo numbers of the animals were covered with adhesive labels outside the cage, and examinations were carried out in randomized order. Home cage observations: The animals were observed in their closed home cages; any disturbing activities (touching the cage or rack, noise) were avoided during these examinations in order not to influence the behavior of the animals. Attention was paid to posture, tremors, convulsions, behaviour, defecation, urination, and general observations (all other abnormal findings). Open field observations: The animals were transferred to a standard arena
(62 x 62 cm with sides of 25 cm high) and observed for at least 2 minutes. Following parameters were examined: fur, skin color, posture, salivation, respiration, activity, arousal level, vocalisation, tremors, convulsions, bizarre behaviour, impairment of gait, lacrimation, exophthalmus, and number of rearings within 2 minutes. Thereafter, the animals were removed from the standard arena and subjected to following sensorimotor or reflex tests: hyperesthesia, abdominal tension, palpebral closure, winking reflex, pupil size, pupillary reflex, pinna reflex, audition ("startle response"), olfaction, pain perception ("tail pinch" ), coordination of movements ("righting response"), and vision ("visual placing response"). Then quantitative parameters were determined: grip strength of forelimbs, grip strength of hindlimbs, and landing foot spread test.

MOTOR ACTIVITY MEASUREMENT:
- Motor activity was measured on the same day as FOB was performed.
- The measurement was performed using the Multi-Varimex-System (Columbus Instruments Int. Corp., Ohio, USA) with 4 infrared beams per cage. During the measurement the animals were kept in Polycarbonate cages with bedding. The cages were cleaned prior to each use. The animals were put into the cages in a randomized order. The measurements started at about 2.00 p.m. and the number of beam interrupts were counted over 18 intervals, each lasting 5 minutes. Measurement did not commence at the same instant for all cages; the period of assessment for each animal started when the first beam was interrupted by pushing the cage into the rack. Measurements ended exactly 1,5 hours thereafter.

Sacrifice and pathology:

GROSS PATHOLOGY: Yes (study day 103)
HISTOPATHOLOGY: Yes
Organs examined at necropsy (macroscopic and microscopic): gastrointestinal tract, liver, pancreas, lungs, kidneys, testes, ovaries, uterus, heart, bone marrow, spleen, thymus, CNS, PNS, thyroid glands

Statistics:

Body weights, clinical chemistry, hematology, urinalyses and liver GSH determination (excepting the differential blood count): ANOVA, Dunnett Clinical data (quantitative parameters of functional observational battery and motor activity): Kruskal-Wallis, Mann-Whitney U-test.
Urinalyses: With the exception of volume, color, turbidity, pH and specific gravity the scale for the urine parameters is divided into 4 sections (0, 1, 2, 3). Subsequently Fisher's exact test for the hypothesis of equal proportions.

Details on results:

CLINICAL SIGNS AND MORTALITY
No deaths were recorded throughout the study. During the preflow period the animals showed no clinical signs and findings different from normal. During the exposure period the animals of the test groups 0, 10 and 50 mg/m³ showed no clinical signs and findings different from normal (except one male animal of test group 10 mg/m³ showed alopecia (forelimbs) from day 76 to the end of the study and one female animal of group 50 mg/m³ showed alopecia (forelimbs) from day 31 to the end of the study. These findings were not considered to be substance related). During the exposure period the animals of the test group 250 mg/m³ showed following abnormal clinical signs: Slight apathy during exposure in males and females up to study day 5. Formation of red crusts on the snouts of male animals detected after exposure up to day 5. Urine smeared anogenital region in male animals after exposure on study day 0. From day 6 onward until the end of the exposure period the animals showed no clinical signs and findings different from normal.

BODY WEIGHT AND WEIGHT GAIN
The body weight of the animals of test group 10 and 50 mg/m³ were not statistically significantly different from the control group 0 mg/m³ (except in the female animals of test group 10 mg/m³ on day 70, where it was increased about 6%). The body weight of the male animals of test group 250 mg/m³ was statistically significantly decreased about 8% and 5% on day 7 and 13, respectively. The body weight of the female animals of test group 250 mg/m³ was statistically significantly decreased about 5% on day 7. It was statistically significantly increased about 7% to 8% from day 70 to day 98. The body weight change of the male animals of test group 10, 50 mg/m³ and of the female animals of test group 50 mg/m³ (except on day 70, where it was about 18% increased) was not statistically significantly different from the control group 0 mg/m³. The body weight change of the female animals of test group 10 mg/m³ was statistically significantly increased about 16% to 20% on days 54, 70, 75 and 91. The body weight change of the male animals of test group 250 mg/m³ was statistically significantly decreased about 90% to 15% from day 7 to day 35. The body weight change of the female animals of test group 250 mg/m³ was statistically significantly decreased about 100% and 45% on day 7 and 13, respectively. It was statistically significantly increased about 19% to 25% from day 54 to day 98.

OPHTHALMOSCOPIC EXAMINATION
No substance related findings were observed during the ophthalmological examinations. Spontaneous findings such as remainders of the pupillary membrane or corneal stippling were observed in several animals of all test groups and the control group without any concentration-response relationship. These findings are regularly observed in rats of this strain and age and are therefore not assessed to be abnormal findings.

HAEMATOLOGY
At the end of the study statistically significantly decreased mean corpuscular hemoglobin (MCH) values were found in the males and females exposed to the highest concentration (250 mg/m³). Furthermore, in the 250-mg/m³ group males statistically significantly increased platelet counts were detected. The other hematology examinations revealed no exposure-related changes. There were no treatment-related changes in the clotting parameters measured.

CLINICAL CHEMISTRY
Exposure of the test compound at the highest concentration (250 mg/m³) to male and female rats for 3 months caused marked increases in gamma-glutamyltransferase activities (about 20-fold of the control value) in the liver homogenates of either sex. Moreover, slightly, but statistically significantly increased alkaline phosphatase and gamma-glutamyltransferase activities were detected in the sera of the male and female animals exposed to the highest concentration. Blood chemistry data from males and females showed statistically significantly decreased urea concentrations and increased total bilirubin levels in the high concentration animals of either sex after 3 months of exposure. Moreover, in the high concentration females decreased sodium and chloride levels were found and in the high concentration males triglyceride content was reduced. The other blood chemistry parameters did not demonstrate exposure-related effects.

URINALYSIS
Females of the highest concentration group excreted increased amounts of urine (Ctrl: 2.1 ml (f); 250 mg/m³: 6.1 (f)) with decreased specific gravity (Ctrl: 0/10 animals with ≤ 1040 g/L (f); 250 mg/m³: 7/10 animals with ≤ 1040 g/L (f); significance level 1%, Fisher's exact test, 2-sided). Furthermore, increased numbers of bacteria were observed in the urine samples of the females (Ctrl: 0/10 animals with assessment limit = 3 (f); 250 mg/m³: 6/10 animals with assessment limit = 3 (f); significance level 5%, Fisher's exact test, 2-sided). In the males of the highest concentration group urinary volume was slightly increased (Ctrl: 4.2 ml (m); 250 mg/m³: 6.1 (m)) and increased blood was detected with reagent strip tests in the urine specimens of these animals (Ctrl: 1/10 animals with assessment limit ≥ 2 (m); 250 mg/m³: 6/10 animals with assessment limit ≥ 2 (m); significance level 5%, Fisher's exact test, 1-sided). The other urinary parameters were not affected by the exposure of the test compound.

NEUROBEHAVIOUR
Home cage observations: No abnormalities were detected in any of the test groups when the animals were observed in their home cages.
Open field observations: One male animal of test group 10 mg/m³ (day 98) and one female animal of test group 50 mg/m³ (day 68 and 98) showed
alopecia. No other abnormal findings were obtained.
Sensorimotor tests/Reflexes: No abnormalities were obtained in any of the test groups.
Quantitative observations: No abnormalities were obtained in any of the test groups.

MOTOR ACTIVITY MEASUREMENT
Regarding the overall motor activity (summation of all intervals) the values were reduced with statistical significance in the male animals in test group 10 mg/m³ on day 34. Comparing the single intervals with the control group, the following statistically significant deviations were seen: decreases of activity in the male animals of test group 10 mg/m³ at interval 7 on day -2, at interval 5, 14 and 16 on day 34 and at interval 3 on day 68; decreases of activity in the male animals of test group 50 mg/m³ at interval 3 on day 68; decreases of activity in the male animals of test group 250 mg/m³ at interval 7 and 8 on day -2, at interval 5 on day 34 and at interval 3 on day 68. Increased values were seen in the female animals of test group 250 mg/m³ at interval 5 on days 98. No other abnormal values were obtained. These observations are judged to be incidental, because they are randomly distributed across the observation times and the measurements and they lack any concentration-response relation.

ORGAN WEIGHTS
Increase of the absolute and relative liver weights of females (correlation to the histopathologically detectable liver changes present in both sexes). Increase of the absolute kidney weights in females (without histopathological correlate).

GROSS PATHOLOGY
No treatment-related findings.

HISTOPATHOLOGY
Centrolobular hypertrophy of hepatocytes (Ctrl: 0/10 animals (m/f); 250 mg/m³: 10/10 (m/f), thereof 10/10 (m) and 9/10 (f) strong hypertrophy)
Single cell necrosis (Ctrl: 0/10 animals (m/f); 250 mg/m³: 10/10 (m/f), thereof 3/10 (m) and 2/10 (f) strong necrosis)
Increase of hemosiderin deposition (as increase in pigmentation) in Kupffer cells (Ctrl: 0/10 animals (m/f); 250 mg/m³: 10/10 (m/f))
Mid (50 mg/m³) and low concentration (10 mg/m³): No treatment related histopathological findings were noted.

OTHER FINDINGS
There are some additional statistically significant intergroup differences in the results of clinical pathology testing. These deviations are marginal, incidental or sporadic, inconsistent, when compared with the other sex, or are not related to the concentration of the test compound. Accordingly, these findings are considered to be of no toxicological significance.

Dose descriptor:

NOAEL

Effect level:

50 mg/m³ air

Sex:

male/female

Basis for effect level:

other: clinical signs; body weight; haematology; clinical chemistry; urinalysis; organ weights; histopathology

Dose descriptor:

LOAEL

Effect level:

250 mg/m³ air

Sex:

male/female

Basis for effect level:

other: clinical signs; body weight; haematology; clinical chemistry; urinalysis; organ weights; histopathology

Critical effects observed:

not specified

Body weight (g)

The mean body weights differed ≤ 8% between test groups.

Significant effects on mean body weights:

_

Timepoint	Gender	Dose Group		Significance level
		0 mg/m³ (Control)	250 mg/m³
Day 7	male	337	310	1%
	female	218	206	5%
Day 13	male	360	341	5 %
	female	not affected
Day 70	male	not affected
	female	274	296	1%
Day 75	male	not affected
	female	279	299	5%
Day 82	male	not affected
	female	282	302	5%
Day 91	male	not affected
	female	286	306	5%
Day 98	male	not affected
	female	285	307	5%

_

Body weight change (g)

The mean body weight changes differed ≤8% between test groups.

Significant effects on body weight change:

_

Timepoint	Gender	Dose Group		Significance level
		0 mg/m³ (Control)	250 mg/m³
Day 7	male	30.7	2.9	1%
	female	16.0	0.0	1%
Day 13	male	54.2	33.7	1 %
	female	23.4	12.9	1 %
Day 20	male	77.9	62.6	5%
	female	not affected
Day 28	male	102.5	86.7	5%
	female	not affected
Day 35	male	118.2	98.9	5%
	female	not affected
Day 54	male	not affected
	female	65.3	77.4	5%
Day 61	male	not affected
	female	71.5	85.6	5%
Day 70	male	not affected
	female	72.1	89.9	1%
Day 75	male	not affected
	female	77.7	93.9	1%
Day 82	male	not affected
	female	79.8	96.2	1%
Day 91	male	not affected
	female	83.9	100.3	1%
Day 98	male	not affected
	female	83.0	101.0	1%

_

Hematology

Significant effects on hematologic parameters:

_

Parameter	Dose group		Significance level
	0 mg/m³ (Control)	250 mg/m³
MCH (mean corpuscular hemoglobin; fmol)
males	1.10	1.05	5%
females	1.13	1.09	5%
Platelet count (Giga/L)
males	797	914	1%
females	not affected

_

Clincal chemistry and blood chemistry

Significant effects on clinical chemistry and blood chemistry parameters:

_

Parameter	Dose group		Significance level
	0 mg/m³ (Control)	250 mg/m³
Bilirubine (umol/L)
males	3.65	7.56	1%
females	3.56	6.40	1%
Sodium (mmol/L)
males	not affected
females	144	141	5%
Chloride (mmol/L)
males	not affected
females	106	102	1%
Triglyceride (mmol/L)
males	2.42	1.20	1%
females	not affected
Urea (mmol/L)
males	4.91	3.89	1%
females	5.96	4.18	1%
Cholesterol (mmol/L)
males	1.79	2.30	1%
females	not affected
Albumine
males	32.2	34.8	1%
females	not affected
Alkaline Phosphatase (sera; ukat/L)
males	2.52	3.07	5%
females	1.51	1.97	1%
Gamma-Glutamyl-transferase (liver; nakat/ g protein)
males	29	602	1%
females	36	706	1%
Gamma-Glutamyl-transferase (sera; nakat/L)
males	0	19	1%
females	0	23	1%

Conclusions:

There was no functional or morphological evidence of neurotoxicity. The liver was the main target organ of systemic toxicity. The kidney also represented a target organ at the highest concentration. Under the conditions of this study, the NOAEL of the test substance is 50 mg/m³, the LOAEL is 250 mg/m³.

Executive summary:

The study is reliable without restrcitions (GLP-study according to OECD Guideline 413; in addition neurotoxicity testing following EPA test guideline (EPA 1985/87)).

Fifteen male and 15 female Wistar rats per test group were exposed to vapors of Vinylformamide (VFA) for 6 hours per working day for 103 days (65 exposures). The target concentrations of treatment groups were 10, 50 and 250 mg/m³ (3,4 ; 17 and 86 ppm). A concurrent control group was exposed to clean air. Clinical examination was performed once each working day during preflow period and on post exposure day (day 103). On exposure days findings were recorded before, during and after exposure. Body weight of the animals was determined weekly. Ophthalmology was carried out prior to and at the end of exposure period. Functional observational batteries and motor activity measurements were performed in 10 animals/sex and test group once before start of the exposure period and three times during the exposure period in about monthly intervals. Hematological and clinicochemical examination of numerous parameters was performed in 10 animals/ sex at the end of exposure period, including GSH and gamma-GT levels in liver homogenate. A complete necropsy including weighing of selected organs and gross pathological evaluation was performed in ten animals per sex. Histopathology was performed on several organs and tissues in these animals as required by the corresponding testing guidelines. Five animals per sex were sacrificed by perfusion fixation. These animals underwent neuropathological examinations.

The following substance related adverse effects occurred:

High concentration (250 mg/m³ = 86 ppm):

- slight apathy in the rats of both sexes and nasal crust formation in males during the first days of the exposure period

- slight depression of body weight development in the male and female animals during the first 5 or 2 weeks of the exposure period, respectively, but recovery as exposure proceeded

- increased alkaline phosphatase, gamma-glutamyltransferase and total bilirubin in the sera of both sexes

- decreased urea in the sera of both sexes

- decreased sodium and chloride in female animals

- decreased triglycerides in the males

- increased gamma-glutamyltransferase and GSH in liver homogenates of both sexes

- increase in urinary volume and blood detection in urine specimens of males increase in urinary volume and decrease of specific gravity in females

- increase of the absolute and relative liver weights of females

- increase of the absolute kidney weights in females

- centrolobular hypertrophy of hepatocytes, minimal to moderate single cell necroses and an increase of hemosiderin deposition in Kupffer cells in the livers of male and female animals

- minimal to slight changes of the transitional and olfactory epithelium in various incidences in male and female animals

Mid concentration (50 mg/m³ = 17 ppm):

- no substance related adverse effects

Low concentration (10 mg/m³ = 3.4 ppm):

- no substance related adverse effects

Conclusions: There was no functional or morphological evidence of neurotoxicity. The liver was the main target organ of systemic toxicity. The kidney also represented a target organ at the highest concentration. Under the conditions of this study, the NOAEL of the test substance is 50 mg/m³, the LOAEL is 250 mg/m³.

Endpoint conclusion

Endpoint conclusion:

adverse effect observed

Dose descriptor:

NOAEC

50 mg/m³

Study duration:

subchronic

Species:

rat

Repeated dose toxicity: inhalation - local effects

Link to relevant study records

Reference

Endpoint:

sub-chronic toxicity: inhalation

Type of information:

experimental study

Adequacy of study:

key study

Study period:

February 21 - June 29, 1994

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: Guideline study (GLP)

Qualifier:

according to guideline

Guideline:

OECD Guideline 413 (Subchronic Inhalation Toxicity: 90-Day Study)

Version / remarks:

; in addition neurotoxicity testing following EPA test guideline (EPA 1985/87)

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: Dr. K. Thomae GmbH, Biberach, FRG
- Age at study initiation: about 7 weeks
- Weight at study initiation: mean males: 307 (287 - 332) g; mean females: 204 (179 - 231) g
- Housing: singel housing in wire cages (type DK III (floor area about 800 cm²) from Becker & Co., Castrop-Rauxel, FRG)
- Diet: KLIBA rat/mouse/hamster laboratory diet 24-343-4, 10 mm pellets (Klingentalmühle AG, Kaiseraugst, Switzerland) ad libitum (except during exposure, motor activity measurements and urine collection)
- Water: Tap water ad libitum (except during exposure, motor activity measurements and urine collection)
- Acclimation period: 7 days

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 20 - 24°C
- Humidity (%): 30 - 70%
- Photoperiod (hrs dark / hrs light): 12 / 12 (6.00 pm - 6.00 am dark; 6.00 am - 6.00 pm light)

Route of administration:

inhalation: vapour

Type of inhalation exposure:

whole body

Vehicle:

other: supply air

Details on inhalation exposure:

GENERATION OF TEST ATMOSPHERE / CHAMBER DESCRIPTION
- Whole-body exposure system: The animals were kept singly in wire cages (DK III) that were located in glass-steel inhalation chambers (volume V= 1.1 m³, BASF AG). In order to accustom the animals to the exposure conditions they were exposed to supply air in whole-body exposure systems on 5 days before the exposure period (preflow period). Thereafter 65 6-hour workday exposures were conducted for all test groups over a time period of 103 days. The animals did not have access to water or feed during the exposure.
- Generation of the inhalation atmospheres: Generator system: continuous infusion pump PERFUSOR (B. Braun), glass evaporator without or with two component atomizer (BASF AG), glass mixing stage (BASF AG), two circulation thermostats (Haake, Huber); Generation procedure: Conditioned supply air (about 50% relative humidity, 22°C) and compressed air were used for the exposure in all test groups. Test group 0 mg/m³: For reaching a chamber temperature comparable to the other test groups, a part of the supply air piping was heated with an electrical heating wire. Test group 10 and 50 mg/m³: The test substance was supplied to the heated glass evaporator at a constant rate by means of the metering pump. It was vaporized with heated compressed air and the developing vapors were passed through a downstream mixing unit before they were mixed with blast air and introduced into the whole-body exposure system. Test group 250 mg/m³: The test substance was sprayed into a counter current of supply air in the heated glass evaporator at a constant rate by means of the metering pump, a two component atomizer and heated compressed air. It was vaporized with heated compressed air and the developing vapors were passed through a downstream mixing unit before they were mixed with blast air and introduced into the whole-body exposure system.
- Air change rate: about 20 times per hour

TEST ATMOSPHERE
- Brief description of analytical method used: gas chromatography (glas column 1 m x 2 mm; separation phase 10% carbowax 20 M)
- Samples taken from breathing zone: yes

Analytical verification of doses or concentrations:

yes

Details on analytical verification of doses or concentrations:

The nominal concentrations were calculated for each exposure level from the test substance consumed and the amount of the supply air used. The concentrations of test substance in the inhalation atmosphere of the test groups 10, 50 and 250 mg/m³ were analyzed by gas chromatography. Daily means were calculated based on 3 (test group 10 mg/m³) or 6 (test group 50 and 250 mg/m³) measured samples. From these daily mean values, mean concentrations and standard deviations for the entire study were derived. The sampling volumes were adjusted to achieve comparable amounts of the test substance in the samples of the different test groups referring to the calibration range.

Duration of treatment / exposure:

103 days

Frequency of treatment:

6 h/working day for 103 days (65 exposures)

Remarks:

Doses / Concentrations:
10, 50 and 250 mg/m³ (3.4, 17 and 86 ppm)
Basis:
other: target conc.

Remarks:

Doses / Concentrations:
14, 69, 371 mg/m³
Basis:
nominal conc.

Remarks:

Doses / Concentrations:
10.1+/-0.89, 50+/-3.3, 253+/-13.0 mg/m³
Basis:
analytical conc.

No. of animals per sex per dose:

15 males and 15 females per dose

Control animals:

other: yes, concurrent vehicle (clean air)

Details on study design:

Post-exposure period: no
- Dose selection rationale: In a 14-day inhalation study (BASF AG, 1986) with concentrations of 450, 150 and 50 mg/m3 (155, 52 and 17 ppm) no clinical symptoms occurred except a slight irritation of the nose during the first few exposure days. Hematological and clinico-chemical examinations
pointed towards liver damage and an anemic process in the mid and high concentrations. Liver damage was substantiated by increased absolute liver weights. Histopathologically an increased glycogen content of the liver in the mid (males only) and the high concentration groups was detected by a
slightly increased PAS reaction. The NOAEC of this study was 50 mg/m³ (17 ppm). Based on the above tests the concentrations were set for the 90-day study. The high concentration was expected to produce impairment of liver and blood as observed in the 14-day study. It was also expected to produce possible neurotoxic effects, if any. The mid concentration should result in marginal effects on liver and blood. The low concentration should represent the NOAEC.

Observations and examinations performed and frequency:

DETAILED CLINICAL OBSERVATIONS: Yes
- Time schedule: A check for dead animals was made daily. The behavior and state of health of the test animals were checked on workdays at least 3 times on exposure days and, as a rule, once during the preflow period and the post-exposure observation day. During exposure only a groupwise examination was possible.

BODY WEIGHT: Yes
- Time schedule for examinations: at the beginning of the preflow period (day -8), on study day -3, study day 0 and then, as a rule, once a week.

OPHTHALMOSCOPIC EXAMINATION: Yes
- Time schedule for examinations: Before the beginning of the preflow period (day -9/-10), the eyes of all animals and at the end of the study (day 94/95), the eyes of the animals of test group 0 mg/m³ (control group) and of test group 250 mg/m³ (high concentration) were examined with an ophthalmoscope, for any changes to the refracting media.

HAEMATOLOGY: Yes
- Time schedule for collection of blood: at the end of application period (study day 103)
- Anaesthetic used for blood collection: No
- Animals fasted: Yes
- How many animals: 10 males and a0 females per dose group
- Examined parameters: leukocytes, erythrocytes, hemoglobin, hematocrit, mean corpuscular volume, mean corpuscular hemoglobin, mean corpuscular hemoglobin concentration, and platelets. The differential blood count and reticulocytes were evaluated visually. Clotting analyses were carried out using a ball coagulometer and the prothrombin time was determined (Hepato Quick's test).

CLINICAL CHEMISTRY: Yes
- Time schedule for collection of blood: at the end of application period (study day 103)
- Animals fasted: Yes (feed was withdrawn from the animals overnight)
- How many animals: 10 males and 10 females per dose group
- Examined parameters: Enzymes: alanine aminotransferase, aspartate aminotransferase, alkaline phosphatase, serum-gamma-glutamyltransferase, and liver-gamma-glutamyltransferase; blood chemistry: sodium, potassium, chloride, inorganic phosphate, calcium, urea, creatinine, glucose, total bilirubin, total protein, albumin, globulins, triglycerides, cholesterol, and magnesium

URINALYSIS: Yes
- Time schedule for collection of urine: Study day 96
- Metabolism cages used for collection of urine: Yes
- Animals fasted: Yes (urine was collected overnight; withdrawal of food and water)
- Examined parameters: volume, color, turbidity, nitrite, pH, protein, glucose, ketones, urobilinogen, bilirubin, blood, specific gravity, and sediment.

NEUROBEHAVIOURAL EXAMINATION: Yes
- Time schedule for examinations: Study days -2, 34, 68 and 98
- Dose groups that were examined: 10 males and 10 females per dose group
- Battery of functions tested: A functional observation battery (FOB) was carried out on the assigned animals. The exposure group, on which FOB was performed, was not exposed on the day of examination. The FOB started with pure observation without influencing the animals, followed by removal from the home cage and open field examinations in a standard arena. Thereafter, sensorimotor tests and reflex tests as well as quantitative measurements were conducted. The examinations were carried out by trained technicians which performed positive control studies as part of their training. The findings were ranked according to the degree of severity, if applicable. In order to ensure that the observer was unaware of the treatment groups the tatoo numbers of the animals were covered with adhesive labels outside the cage, and examinations were carried out in randomized order. Home cage observations: The animals were observed in their closed home cages; any disturbing activities (touching the cage or rack, noise) were avoided during these examinations in order not to influence the behavior of the animals. Attention was paid to posture, tremors, convulsions, behaviour, defecation, urination, and general observations (all other abnormal findings). Open field observations: The animals were transferred to a standard arena
(62 x 62 cm with sides of 25 cm high) and observed for at least 2 minutes. Following parameters were examined: fur, skin color, posture, salivation, respiration, activity, arousal level, vocalisation, tremors, convulsions, bizarre behaviour, impairment of gait, lacrimation, exophthalmus, and number of rearings within 2 minutes. Thereafter, the animals were removed from the standard arena and subjected to following sensorimotor or reflex tests: hyperesthesia, abdominal tension, palpebral closure, winking reflex, pupil size, pupillary reflex, pinna reflex, audition ("startle response"), olfaction, pain perception ("tail pinch" ), coordination of movements ("righting response"), and vision ("visual placing response"). Then quantitative parameters were determined: grip strength of forelimbs, grip strength of hindlimbs, and landing foot spread test.

MOTOR ACTIVITY MEASUREMENT:
- Motor activity was measured on the same day as FOB was performed.
- The measurement was performed using the Multi-Varimex-System (Columbus Instruments Int. Corp., Ohio, USA) with 4 infrared beams per cage. During the measurement the animals were kept in Polycarbonate cages with bedding. The cages were cleaned prior to each use. The animals were put into the cages in a randomized order. The measurements started at about 2.00 p.m. and the number of beam interrupts were counted over 18 intervals, each lasting 5 minutes. Measurement did not commence at the same instant for all cages; the period of assessment for each animal started when the first beam was interrupted by pushing the cage into the rack. Measurements ended exactly 1,5 hours thereafter.

Sacrifice and pathology:

GROSS PATHOLOGY: Yes (study day 103)
HISTOPATHOLOGY: Yes
Organs examined at necropsy (macroscopic and microscopic): gastrointestinal tract, liver, pancreas, lungs, kidneys, testes, ovaries, uterus, heart, bone marrow, spleen, thymus, CNS, PNS, thyroid glands

Statistics:

Body weights, clinical chemistry, hematology, urinalyses and liver GSH determination (excepting the differential blood count): ANOVA, Dunnett Clinical data (quantitative parameters of functional observational battery and motor activity): Kruskal-Wallis, Mann-Whitney U-test.
Urinalyses: With the exception of volume, color, turbidity, pH and specific gravity the scale for the urine parameters is divided into 4 sections (0, 1, 2, 3). Subsequently Fisher's exact test for the hypothesis of equal proportions.

Details on results:

CLINICAL SIGNS AND MORTALITY
No deaths were recorded throughout the study. During the preflow period the animals showed no clinical signs and findings different from normal. During the exposure period the animals of the test groups 0, 10 and 50 mg/m³ showed no clinical signs and findings different from normal (except one male animal of test group 10 mg/m³ showed alopecia (forelimbs) from day 76 to the end of the study and one female animal of group 50 mg/m³ showed alopecia (forelimbs) from day 31 to the end of the study. These findings were not considered to be substance related). During the exposure period the animals of the test group 250 mg/m³ showed following abnormal clinical signs: Slight apathy during exposure in males and females up to study day 5. Formation of red crusts on the snouts of male animals detected after exposure up to day 5. Urine smeared anogenital region in male animals after exposure on study day 0. From day 6 onward until the end of the exposure period the animals showed no clinical signs and findings different from normal.

BODY WEIGHT AND WEIGHT GAIN
The body weight of the animals of test group 10 and 50 mg/m³ were not statistically significantly different from the control group 0 mg/m³ (except in the female animals of test group 10 mg/m³ on day 70, where it was increased about 6%). The body weight of the male animals of test group 250 mg/m³ was statistically significantly decreased about 8% and 5% on day 7 and 13, respectively. The body weight of the female animals of test group 250 mg/m³ was statistically significantly decreased about 5% on day 7. It was statistically significantly increased about 7% to 8% from day 70 to day 98. The body weight change of the male animals of test group 10, 50 mg/m³ and of the female animals of test group 50 mg/m³ (except on day 70, where it was about 18% increased) was not statistically significantly different from the control group 0 mg/m³. The body weight change of the female animals of test group 10 mg/m³ was statistically significantly increased about 16% to 20% on days 54, 70, 75 and 91. The body weight change of the male animals of test group 250 mg/m³ was statistically significantly decreased about 90% to 15% from day 7 to day 35. The body weight change of the female animals of test group 250 mg/m³ was statistically significantly decreased about 100% and 45% on day 7 and 13, respectively. It was statistically significantly increased about 19% to 25% from day 54 to day 98.

OPHTHALMOSCOPIC EXAMINATION
No substance related findings were observed during the ophthalmological examinations. Spontaneous findings such as remainders of the pupillary membrane or corneal stippling were observed in several animals of all test groups and the control group without any concentration-response relationship. These findings are regularly observed in rats of this strain and age and are therefore not assessed to be abnormal findings.

HAEMATOLOGY
At the end of the study statistically significantly decreased mean corpuscular hemoglobin (MCH) values were found in the males and females exposed to the highest concentration (250 mg/m³). Furthermore, in the 250-mg/m³ group males statistically significantly increased platelet counts were detected. The other hematology examinations revealed no exposure-related changes. There were no treatment-related changes in the clotting parameters measured.

CLINICAL CHEMISTRY
Exposure of the test compound at the highest concentration (250 mg/m³) to male and female rats for 3 months caused marked increases in gamma-glutamyltransferase activities (about 20-fold of the control value) in the liver homogenates of either sex. Moreover, slightly, but statistically significantly increased alkaline phosphatase and gamma-glutamyltransferase activities were detected in the sera of the male and female animals exposed to the highest concentration. Blood chemistry data from males and females showed statistically significantly decreased urea concentrations and increased total bilirubin levels in the high concentration animals of either sex after 3 months of exposure. Moreover, in the high concentration females decreased sodium and chloride levels were found and in the high concentration males triglyceride content was reduced. The other blood chemistry parameters did not demonstrate exposure-related effects.

URINALYSIS
Females of the highest concentration group excreted increased amounts of urine (Ctrl: 2.1 ml (f); 250 mg/m³: 6.1 (f)) with decreased specific gravity (Ctrl: 0/10 animals with ≤ 1040 g/L (f); 250 mg/m³: 7/10 animals with ≤ 1040 g/L (f); significance level 1%, Fisher's exact test, 2-sided). Furthermore, increased numbers of bacteria were observed in the urine samples of the females (Ctrl: 0/10 animals with assessment limit = 3 (f); 250 mg/m³: 6/10 animals with assessment limit = 3 (f); significance level 5%, Fisher's exact test, 2-sided). In the males of the highest concentration group urinary volume was slightly increased (Ctrl: 4.2 ml (m); 250 mg/m³: 6.1 (m)) and increased blood was detected with reagent strip tests in the urine specimens of these animals (Ctrl: 1/10 animals with assessment limit ≥ 2 (m); 250 mg/m³: 6/10 animals with assessment limit ≥ 2 (m); significance level 5%, Fisher's exact test, 1-sided). The other urinary parameters were not affected by the exposure of the test compound.

NEUROBEHAVIOUR
Home cage observations: No abnormalities were detected in any of the test groups when the animals were observed in their home cages.
Open field observations: One male animal of test group 10 mg/m³ (day 98) and one female animal of test group 50 mg/m³ (day 68 and 98) showed
alopecia. No other abnormal findings were obtained.
Sensorimotor tests/Reflexes: No abnormalities were obtained in any of the test groups.
Quantitative observations: No abnormalities were obtained in any of the test groups.

MOTOR ACTIVITY MEASUREMENT
Regarding the overall motor activity (summation of all intervals) the values were reduced with statistical significance in the male animals in test group 10 mg/m³ on day 34. Comparing the single intervals with the control group, the following statistically significant deviations were seen: decreases of activity in the male animals of test group 10 mg/m³ at interval 7 on day -2, at interval 5, 14 and 16 on day 34 and at interval 3 on day 68; decreases of activity in the male animals of test group 50 mg/m³ at interval 3 on day 68; decreases of activity in the male animals of test group 250 mg/m³ at interval 7 and 8 on day -2, at interval 5 on day 34 and at interval 3 on day 68. Increased values were seen in the female animals of test group 250 mg/m³ at interval 5 on days 98. No other abnormal values were obtained. These observations are judged to be incidental, because they are randomly distributed across the observation times and the measurements and they lack any concentration-response relation.

ORGAN WEIGHTS
Increase of the absolute and relative liver weights of females (correlation to the histopathologically detectable liver changes present in both sexes). Increase of the absolute kidney weights in females (without histopathological correlate).

GROSS PATHOLOGY
No treatment-related findings.

HISTOPATHOLOGY
Centrolobular hypertrophy of hepatocytes (Ctrl: 0/10 animals (m/f); 250 mg/m³: 10/10 (m/f), thereof 10/10 (m) and 9/10 (f) strong hypertrophy)
Single cell necrosis (Ctrl: 0/10 animals (m/f); 250 mg/m³: 10/10 (m/f), thereof 3/10 (m) and 2/10 (f) strong necrosis)
Increase of hemosiderin deposition (as increase in pigmentation) in Kupffer cells (Ctrl: 0/10 animals (m/f); 250 mg/m³: 10/10 (m/f))
Mid (50 mg/m³) and low concentration (10 mg/m³): No treatment related histopathological findings were noted.

OTHER FINDINGS
There are some additional statistically significant intergroup differences in the results of clinical pathology testing. These deviations are marginal, incidental or sporadic, inconsistent, when compared with the other sex, or are not related to the concentration of the test compound. Accordingly, these findings are considered to be of no toxicological significance.

Dose descriptor:

NOAEL

Effect level:

50 mg/m³ air

Sex:

male/female

Basis for effect level:

other: clinical signs; body weight; haematology; clinical chemistry; urinalysis; organ weights; histopathology

Dose descriptor:

LOAEL

Effect level:

250 mg/m³ air

Sex:

male/female

Basis for effect level:

other: clinical signs; body weight; haematology; clinical chemistry; urinalysis; organ weights; histopathology

Critical effects observed:

not specified

Body weight (g)

The mean body weights differed ≤ 8% between test groups.

Significant effects on mean body weights:

_

Timepoint	Gender	Dose Group		Significance level
		0 mg/m³ (Control)	250 mg/m³
Day 7	male	337	310	1%
	female	218	206	5%
Day 13	male	360	341	5 %
	female	not affected
Day 70	male	not affected
	female	274	296	1%
Day 75	male	not affected
	female	279	299	5%
Day 82	male	not affected
	female	282	302	5%
Day 91	male	not affected
	female	286	306	5%
Day 98	male	not affected
	female	285	307	5%

_

Body weight change (g)

The mean body weight changes differed ≤8% between test groups.

Significant effects on body weight change:

_

Timepoint	Gender	Dose Group		Significance level
		0 mg/m³ (Control)	250 mg/m³
Day 7	male	30.7	2.9	1%
	female	16.0	0.0	1%
Day 13	male	54.2	33.7	1 %
	female	23.4	12.9	1 %
Day 20	male	77.9	62.6	5%
	female	not affected
Day 28	male	102.5	86.7	5%
	female	not affected
Day 35	male	118.2	98.9	5%
	female	not affected
Day 54	male	not affected
	female	65.3	77.4	5%
Day 61	male	not affected
	female	71.5	85.6	5%
Day 70	male	not affected
	female	72.1	89.9	1%
Day 75	male	not affected
	female	77.7	93.9	1%
Day 82	male	not affected
	female	79.8	96.2	1%
Day 91	male	not affected
	female	83.9	100.3	1%
Day 98	male	not affected
	female	83.0	101.0	1%

_

Hematology

Significant effects on hematologic parameters:

_

Parameter	Dose group		Significance level
	0 mg/m³ (Control)	250 mg/m³
MCH (mean corpuscular hemoglobin; fmol)
males	1.10	1.05	5%
females	1.13	1.09	5%
Platelet count (Giga/L)
males	797	914	1%
females	not affected

_

Clincal chemistry and blood chemistry

Significant effects on clinical chemistry and blood chemistry parameters:

_

Parameter	Dose group		Significance level
	0 mg/m³ (Control)	250 mg/m³
Bilirubine (umol/L)
males	3.65	7.56	1%
females	3.56	6.40	1%
Sodium (mmol/L)
males	not affected
females	144	141	5%
Chloride (mmol/L)
males	not affected
females	106	102	1%
Triglyceride (mmol/L)
males	2.42	1.20	1%
females	not affected
Urea (mmol/L)
males	4.91	3.89	1%
females	5.96	4.18	1%
Cholesterol (mmol/L)
males	1.79	2.30	1%
females	not affected
Albumine
males	32.2	34.8	1%
females	not affected
Alkaline Phosphatase (sera; ukat/L)
males	2.52	3.07	5%
females	1.51	1.97	1%
Gamma-Glutamyl-transferase (liver; nakat/ g protein)
males	29	602	1%
females	36	706	1%
Gamma-Glutamyl-transferase (sera; nakat/L)
males	0	19	1%
females	0	23	1%

Conclusions:

There was no functional or morphological evidence of neurotoxicity. The liver was the main target organ of systemic toxicity. The kidney also represented a target organ at the highest concentration. Under the conditions of this study, the NOAEL of the test substance is 50 mg/m³, the LOAEL is 250 mg/m³.

Executive summary:

The study is reliable without restrcitions (GLP-study according to OECD Guideline 413; in addition neurotoxicity testing following EPA test guideline (EPA 1985/87)).

Fifteen male and 15 female Wistar rats per test group were exposed to vapors of Vinylformamide (VFA) for 6 hours per working day for 103 days (65 exposures). The target concentrations of treatment groups were 10, 50 and 250 mg/m³ (3,4 ; 17 and 86 ppm). A concurrent control group was exposed to clean air. Clinical examination was performed once each working day during preflow period and on post exposure day (day 103). On exposure days findings were recorded before, during and after exposure. Body weight of the animals was determined weekly. Ophthalmology was carried out prior to and at the end of exposure period. Functional observational batteries and motor activity measurements were performed in 10 animals/sex and test group once before start of the exposure period and three times during the exposure period in about monthly intervals. Hematological and clinicochemical examination of numerous parameters was performed in 10 animals/ sex at the end of exposure period, including GSH and gamma-GT levels in liver homogenate. A complete necropsy including weighing of selected organs and gross pathological evaluation was performed in ten animals per sex. Histopathology was performed on several organs and tissues in these animals as required by the corresponding testing guidelines. Five animals per sex were sacrificed by perfusion fixation. These animals underwent neuropathological examinations.

The following substance related adverse effects occurred:

High concentration (250 mg/m³ = 86 ppm):

- slight apathy in the rats of both sexes and nasal crust formation in males during the first days of the exposure period

- slight depression of body weight development in the male and female animals during the first 5 or 2 weeks of the exposure period, respectively, but recovery as exposure proceeded

- increased alkaline phosphatase, gamma-glutamyltransferase and total bilirubin in the sera of both sexes

- decreased urea in the sera of both sexes

- decreased sodium and chloride in female animals

- decreased triglycerides in the males

- increased gamma-glutamyltransferase and GSH in liver homogenates of both sexes

- increase in urinary volume and blood detection in urine specimens of males increase in urinary volume and decrease of specific gravity in females

- increase of the absolute and relative liver weights of females

- increase of the absolute kidney weights in females

- centrolobular hypertrophy of hepatocytes, minimal to moderate single cell necroses and an increase of hemosiderin deposition in Kupffer cells in the livers of male and female animals

- minimal to slight changes of the transitional and olfactory epithelium in various incidences in male and female animals

Mid concentration (50 mg/m³ = 17 ppm):

- no substance related adverse effects

Low concentration (10 mg/m³ = 3.4 ppm):

- no substance related adverse effects

Conclusions: There was no functional or morphological evidence of neurotoxicity. The liver was the main target organ of systemic toxicity. The kidney also represented a target organ at the highest concentration. Under the conditions of this study, the NOAEL of the test substance is 50 mg/m³, the LOAEL is 250 mg/m³.

Endpoint conclusion

Endpoint conclusion:

adverse effect observed

Dose descriptor:

NOAEC

50 mg/m³

Study duration:

subchronic

Species:

rat

Repeated dose toxicity: dermal - systemic effects

Endpoint conclusion

Endpoint conclusion:

no study available

Repeated dose toxicity: dermal - local effects

Endpoint conclusion

Endpoint conclusion:

no study available

Additional information

Repeated dose toxicity: Inhalation

In the key study according to OECD Guideline 413 15 male and 15 female Wistar rats per test group were exposed to vapors of N-Vinylformamide for 6 hours per working day for 103 days (65 exposures). The target concentrations of treatment groups were 10, 50 and 250 mg/m³ (3.4, 17 and 86 ppm). A concurrent control group was exposed to clean air. There was no functional or morphological evidence of neurotoxicity. The high concentration caused some signs of clinical irritation of the upper respiratory tract with mild changes in the nasal cavity as histopathological correlate. Initial depression of body weight development recovered until the end of the study. The liver was the main target organ of systemic toxicity. The high concentration produced abnormalities in several clinical chemistry parameters (alkaline phosphatase, gamma-GT, bilirubin) and in the liver homogenate (gamma-GT, GSH). Liver weights of female animals were increased. These findings correlate to the histopathologically detectable liver changes present in both sexes (centrolobular hypertrophy of hepatocytes, minimal to moderate single cell necroses and an increase of hemosiderin deposition in Kupffer cells). The kidney also represented a target organ at the high concentration. The increased urinary volume, which is associated with decreased specific gravity of urine as well as the decreased blood levels of sodium and chloride, and the increased absolute kidney weights in females, although without histopathological correlate, indicate some impairment of this organ. The slight increase of gamma-glutamyltransferase and GSH levels in liver homogenate and the liver weight changes in female animals caused by mid concentrations is considered to be an adaptive response to increase the metabolic capacity of the organ. It is considered to be reversible and not an adverse effect. The NOAEC under the conditions of this study therefore was 50 mg/m³ (BASF AG, 1995).

In the range-finder study for the above-mentioned subchronic inhalation study carried out in rats with a 14-day exposure to N-Vinylformamide at dose levels of 50, 150 and 450 mg/m³ substance-induced changes in the red blood count and distinct signs of hepatotoxic effects were observed in dose groups 150 and 450 mg/m³. Based on clinical signs, haematology, clinical chemistry, organ weights and histopathology a NOAEL of 50 mg/m³ was established under the conditions of this study (BASF AG, 1985).

Repeated dose toxicity: Oral

No subacute, subchronic or chronic repeated dose studies with oral application are available for N-Vinylformamide.

Repeated dose toxicity: Dermal

No subacute, subchronic or chronic repeated dose studies with dermal application are available for N-Vinylformamide.

Repeated dose toxicity: inhalation - systemic effects (target organ) digestive: liver

Justification for classification or non-classification

GHS classification according to Annex I 1272/2008 CLP (EU GHS):

Based on the results of a subchronic vapour inhalation study (key study; BASF, 1995) N-Vinylformamide is classified and labeled with STOT RE 2; H373; target organ: liver