Reaction mass of ethane-1,2-diol and 2-hydroxyethyl formate and ethylene diformate

Repeated dose toxicity: inhalation

Administrative data

Endpoint:

sub-chronic toxicity: inhalation

Type of information:

experimental study

Adequacy of study:

weight of evidence

Study period:

December 1987 - March 1988

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Data source

Reference

Reference Type:

publication

Title:

NTP Technical Report on Toxicity Studies of Formic Acid (CAS No: 64-18-6) Administered by Inhalation to F344/N Rats and B6C3F1 Mice

Author:

Thompson M.

Year:

1992

Bibliographic source:

NIH Publication 92-3342, Toxicity Report Series Number 19

Report date:

1992

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

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

Deviations:

no

GLP compliance:

not specified

Limit test:

no

Test material

Test material information

Constituent 1

Reference substance name:

Formic acid

EC Number:

200-579-1

EC Name:

Formic acid

Cas Number:

64-18-6

Molecular formula:

CH2O2

IUPAC Name:

formic acid

Test animals

Species:

rat

Strain:

Fischer 344

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Taconic Farms, Inc., Germantown, NY
- Age at study initiation: 6 wks (7 weeks for mice in 13-week studies)
- Housing: individually
- Diet: standard NIH-07 diet ad libitum
- Water: tab water ad libitum
- Acclimation period: 12 days


ENVIRONMENTAL CONDITIONS
- Temperature (°C): temperature 75°F
- Humidity (%): rel. humidity 55+/-15%,
- air changes per hour: 15
- Photoperiod (hrs dark / hrs light): 12/12

Administration / exposure

Route of administration:

inhalation: aerosol

Type of inhalation exposure:

whole body

Vehicle:

air

Details on inhalation exposure:

GENERATION OF TEST ATMOSPHERE / CHAMBER DESCRIPTION
- Exposure apparatus: commercial 1.7 m³ inhalation chambers
- Temperature, humidity, pressure in air chamber: temperature 75°F, rel. humidity 55+/-15%
- Vapor generation: liquid formic acid was pumped by a micrometer pump to a vaporizer heated to 97.5°C. The vapor entered a distribution line where a constant 2300 ppm atmosphere was maintained. Dilution air (HEPA filtered, rel. humidity 50%) carried a metered amount to the individual exposure chambers.

TEST ATMOSPHERE
- Brief description of analytical method used: a Foxboro Mitran 980 infrared spectrometer at 9.050 microns was used to monitor the exposure chambers, control chamber, exposure room, an online standard of formic acid vapor, and a pure nitrogen source. All locations were monitored every 40 min. In addition, formaldehyde concentrations were monitored in the 8 ppm and 128 ppm exposure chambers, and in the formic acid distribution line. Corrections were made for absorbance of water and for instrument drift.
The online monitor was calibrated with GC analyses of grab samples taken from the exposure chambers at the time of the readings.

The limit of detection and limit of quantification for the on-line monitor were determined at an average chamber relative humidity of 33-51%.
The practical detection limit was 0.36 ± 0.10 ppm, with a practical quantification limit of 0.68 ± 0.10 ppm.

- Samples taken from breathing zone: yes

Analytical verification of doses or concentrations:

yes

Details on analytical verification of doses or concentrations:

A Foxboro Mitran 980 infrared spectrometer at 9.050 microns was used to monitor the exposure chambers, control chamber, exposure room, an online standard of formic acid vapor, and a pure nitrogen source. All locations were monitored every 40 min. In addition, formaldehyde concentrations were monitored in the 8 ppm and 128 ppm exposure chambers, and in the formic acid distribution line. Corrections were made for absorbance of water and for instrument drift. The online monitor was calibrated with GC analyses of grab samples taken from the exposure chambers at the time of the readings.
The limit of detection and limit of quantification for the on-line monitor were determined at an average chamber relative humidity of 33-51%. The practical detection limit was 0.36 ± 0.10 ppm, with a practical quantification limit of 0.68 ± 0.10 ppm.

Duration of treatment / exposure:

13 weeks

Frequency of treatment:

5 days/week, 6 hours/day

Doses / concentrations

Doses / concentrations 1

Dose / conc.:

0 ppm

Remarks:

corresponding to 0 mg/L

Doses / concentrations 2

Dose / conc.:

8 ppm

Remarks:

corresponding to 0.015 mg/L

Doses / concentrations 3

Dose / conc.:

16 ppm

Remarks:

corresponding to 0.030 mg/L

Doses / concentrations 4

Dose / conc.:

32 ppm

Remarks:

corresponding to 0.061 mg/L

Doses / concentrations 5

Dose / conc.:

64 ppm

Remarks:

corresponding to 0.122 mg/L

Doses / concentrations 6

Dose / conc.:

128 ppm

Remarks:

corresponding to 0.244 mg/L

No. of animals per sex per dose:

20
(10 for core study and 10 for clinical pathological studies performed after 3, 23 and 90 days of the study)

Control animals:

yes, concurrent no treatment

Details on study design:

Post-exposure period: none
- Dose selection rationale: based on rangefinding study

Positive control:

None

Examinations

Observations and examinations performed and frequency:

CAGE SIDE OBSERVATIONS: Yes
- Time schedule: daily

DETAILED CLINICAL OBSERVATIONS: Yes
- Time schedule: daily

BODY WEIGHT: Yes
- Time schedule for examinations: recorded on a weekly base

OPHTHALMOSCOPIC EXAMINATION: No

HAEMATOLOGY: Yes
- Time schedule for collection of blood: additional rats on days 3 and 23, core study animals at termination in week 13
- Anaesthetic used for blood collection: Yes (70% CO2:30% O2)
- Animals fasted: No data
- How many animals: 10/sex/dose
- Parameters checked in table No. B1 (report, Appendix B) were examined.

CLINICAL CHEMISTRY: Yes
- Time schedule for collection of blood:
- Animals fasted: No data
- How many animals: 10/sex/dose
- Parameters checked in table No. B1 (report, Appendix B) were examined.

URINALYSIS: No. Only in rangefinding study

NEUROBEHAVIOURAL EXAMINATION: No

- Gross pathology: YES
- Time schedule: at termination
- How many animals: 10/sex/dose

Histopathology: Yes
- Tssues examined: adrenal glands, brain, bronchial lymph nodes, cecum, colon, duodenum, epididymis/seminal vesicles/ prostate/testes or ovaries/uterus, esophagus, eyes (if grossly abnormal), femur (including marrow), gallbladder (mice), gross lesions and tissue masses with regional lymph nodes, heart, ileum, jejunum, kidneys, larynx, liver, lungs with mainstem bronchi, mammary gland and adjacent skin, mandibular and mesenteric lymph nodes, mediastinal lymph nodes, nasal cavity and turbinates, pancreas, parathyroid glands, pharynx (if grossly abnormal), pituitary gland, preputial /clitoral glands (rats), rectum, salivary glands, spinal cord and sciatic nerve (if neurologic signs present), spleen, stomach (including forestomach and glandular stomach), thigh muscle, thymus, thyroid gland, trachea, and urinary bladder. In addition to all gross lesions, the following tissues were examined in all other dose groups:
rats--nose (three transverse sections), lung, larynx, trachea, bronchial and mediastinal lymph nodes;
mice--nose (three transverse sections).
Organ weights (to the nearest mg) were obtained from all core study animals and include: liver, thymus, right kidney, right testis, heart
and lungs.

Other:
- sperm morphology and vaginal cytology were evaluated in rats and mice exposed to 0, 8, 32, and 128 ppm.

Sacrifice and pathology:

GROSS PATHOLOGY: Yes
HISTOPATHOLOGY: Yes

Other examinations:

Compared to OECD 423: additional examinations of effects on respiratory tract and reproductive organs. Sperm morphology and vaginal cytology were evaluated in rats and mice exposed to 0, 8, 32, and 128 ppm.

Statistics:

Organ and body weight data: procedures by Williams (1971, 1972) and Dunnett (1955).
Clinical chemistry and hematology data: nonparametric multiple comparisons methods of Shirley (1977) and Dunn (1964).

Results and discussion

Results of examinations

Clinical signs:

no effects observed

Description (incidence and severity):

No clinical signs that were clearly treatment-related were noted.

Systemic toxicity: no systemic toxic effect occurred at any dose level. Few changes compared to controls were noted (increase in body weight at the low doses, isolated minor to mild changes in hematology and clinical chemistry,) but were few and generally minimal to mild in magnitude, and showed no dose-related pattern.

Mortality:

no mortality observed

Body weight and weight changes:

effects observed, treatment-related

Description (incidence and severity):

Body weights were not affected, terminal body weights were all within +/- 5% compared to controls.

Food consumption and compound intake (if feeding study):

not examined

Food efficiency:

not examined

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

not examined

Ophthalmological findings:

not examined

Haematological findings:

no effects observed

Description (incidence and severity):

Isolated minor to mild changes; few and generally minimal to mild in magnitude, and showed no dose-related pattern.

Clinical biochemistry findings:

no effects observed

Description (incidence and severity):

Isolated minor to mild changes; few and generally minimal to mild in magnitude, and showed no dose-related pattern.

Urinalysis findings:

not specified

Organ weight findings including organ / body weight ratios:

effects observed, treatment-related

Description (incidence and severity):

No treatment-related effect effects on absolute/relative organ weights.

Gross pathological findings:

no effects observed

Description (incidence and severity):

There were no unusual gross lesions. The occurrence of variations in absolute or relative organs weights (liver: increased in all treated male groups (p<0.05 at 8 and 16 ppm; p<0.01 at 32, 64, and 128 ppm); lung: decreased in all treated male and female groups, p as much as p<0.01) was not dose-related, and there was no histopathological correlate.

Histopathological findings: non-neoplastic:

effects observed, treatment-related

Description (incidence and severity):

Increased incidences of histopathological changes were noted in the nose of animals at 128 ppm, substantiated by squamous metaplasia of the
respirators epithelium and degeneration of the olfactory epithelium in most animals. The incidence was higher in males compared to females. The
severity was generally minimal to mild. Lesions observed at 62.5 ppm in the preliminary 14-day exposure study in this species/laboratory could not be reproduced in this more robust study with longer exposure. For details see "Remarks on results" and "Overall Remarks"

Histopathological findings: neoplastic:

not examined

Other effects:

no effects observed

Description (incidence and severity):

Male and female reproductive organs: Regarding the male and female reproductive organs, there were no effects on sperm motility, density or testicular or epididymal weights, and no changes were seen in the length of the estrous cycle.

Effect levels

1

Key result

Dose descriptor:

NOAEC

Remarks:

local

Effect level:

0.122 mg/L air

Based on:

test mat.

Sex:

male/female

Basis for effect level:

other: microscopic examination of upper respiratory tract including olfactory epithelium: absence of / or minimal effects

2

Key result

Dose descriptor:

LOAEC

Remarks:

local

Effect level:

0.244 mg/L air

Based on:

test mat.

Sex:

male/female

Basis for effect level:

other: increased incidences of squamous metaplasia of the respiratory epithelium and degeneration of the olfactory epithelium

3

Key result

Dose descriptor:

NOAEC

Remarks:

systemic

Effect level:

0.244 mg/L air

Sex:

male/female

Basis for effect level:

other: Absence of systemic effects. Histopathology: no effects except from nasal effects. Testicular and epididymal weight, sperm motility and sperm density: not affected. Female estrous cycle: not affected.

Target system / organ toxicity

Key result

Critical effects observed:

not specified

Any other information on results incl. tables

Exposure concentration: during the 2-week and the 13-week studies, at least 96% and 91%, respectively, of the measured concentrations for each chamber were within ± 10% of the target concentration.

Effects summary:

Species, strain, number, sex/group	Test substance Duration, concentration	NOAEC/LOAEC, findings, remarks	Reliability	Reference
Inhalation
Rat Fischer F344   10 m 10 f	Formic acid 13 weeks   0; 0.015; 0.030; 0.061; 0.122; 0.244 mg/L; (0, 8; 16; 32; 64; and 128 ppm) for 6 h/day, 5x/ week   (65 exposures). (whole body exposure)	NOAEC for local toxicity: 0.122 mg/(L*d) (64 ppm); based on upper respiratory tract irritation.   64 ppm: Nose; 1/20 mild degeneration olfactory epithelium.   LOAEC for local toxicity: 128 ppm: Nose; respiratory epithelium; squamousmetaplasiain 15/20 animals.Olfactoryepithelium degeneration in 14/20 animals.   NOAEC for systemic toxicity:128 ppm (0.244 mg/(L*d)   Systemic effects: 0/20; LOAEC not achieved at highest tested concentration (128 ppm)   Histopathology: no effects except from nasal effects.   Testicular andepididymalweight, sperm motility and sperm density: not affected.   Female estrous cycle: not affected.	1	NTP (1992)

Applicant's summary and conclusion

Conclusions:

The NOAEC and LOAEC were 0.122mg/L (i.e. 64 ppm) and 0.244mg/L (i.e. 128 ppm) based on respiratory effects.

Executive summary:

In this OECD guideline No. 413 test conducted under GLP conditions, 10 rats per sex and dose were exposed to formic acidv apor at 0, 0.015, 0.030, 0.062, 0.122, or 0.244 mg/L (0, 8, 16, 32, 64, or 128 ppm; dose selection based on results of a range finding study) via whole-body inhalation 6 hours/day, 5 days/week for 13 weeks.

There were no mortalities nor clinical signs or systemic toxicity in male and female rats exposed to 8, 16, 32, 64, or 128 ppm for 13 weeks (5 days/week, 6 h/day). There were no unusual gross lesions noted during necropsy, organ weights were not affected by treatment. Male and female reproductive parameters (sperm motility, density, and testicular or epididymal weight; length of the estrous cycle) were not affected. Histopathology revealed increased incidences of squamous metaplasia of the respiratory epithelium and degeneration of the olfactory epithelium in the high-dose male and female rat groups where most of the animals were affected. However, the severity was generally minimal to mild.

A systemic LOAEC was not achieved. The authors suggested that the lack of systemic effects in both 2-week and 13-week NTP inhalation studies is possibly related to the rapid metabolizing capacity of formate to CO₂, due to high tetrahydrofolate and 10-formyl tetrahydrofolate dehydrogenase levels in rodents. These levels are much lower in humans who are significantly more sensitive to the formate toxicity. Therefore, caution should be used in considering the results obtained with rodents in determining potential human risks associated with systemic exposure to formic acid. Nevertheless human experience does not indicate that formic acid represents a significant systemic thread to humans unless at high concentrations following intended or incidental ingestion or large scale skin contact, where the caustic effect also governs the toxic mode of action.

Based on the local histopathological changes in the respiratory tract the NOAEC in this study was determined to be 64 ppm (0.122 mg/L), and the LOAEC was 128 ppm (0.244 mg/L). The systemic NOAEC was 128 ppm (0.244 mg/L), the highest concentration tested.