Formic acid, manufacture of, by-products from

Repeated dose toxicity: inhalation

Administrative data

Endpoint:

short-term repeated dose toxicity: inhalation

Type of information:

experimental study

Adequacy of study:

supporting study

Study period:

August 1987 - September 1987

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: GLP guideline study. Range-finding study, findings to be considered together with the main study.

Data source

Reference

Reference 1

Reference Type:

publication

Title:

Unnamed

Year:

1989

Reference 2

Reference Type:

publication

Title:

Unnamed

Year:

1992

Materials and methods

Principles of method if other than guideline:

GLP guideline study. 14-day range-finding study

GLP compliance:

yes

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

Details on test material:

95 % formic acid / 5 % water
- Name of test material (as cited in study report): formic acid
- Physical state: liquid
- Analytical purity: 95%
- Impurities (identity and concentrations): water. Formaldehyde: <0.1%
- Composition of test material, percentage of components: 95% formic acid, 5% water

Specific details on test material used for the study:

95 % formic acid / 5 % water
- Name of test material (as cited in study report): formic acid
- Physical state: liquid
- Analytical purity: 95%
- Impurities (identity and concentrations): water. Formaldehyde: <0.1%
- Composition of test material, percentage of components: 95% formic acid, 5% water

Test animals

Species:

mouse

Strain:

B6C3F1

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

Type of inhalation exposure:

whole body

Vehicle:

other: 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 teh 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:

12 days

Frequency of treatment:

5 days/week, 6 h/day

Doses / concentrations

Remarks:

Doses / Concentrations:
0; 0.06; 0.12; 0.24; 0.48; 0.95 mg/l (0; 31; 62.5; 125; 250; 500 ppm)
Basis:

No. of animals per sex per dose:

5

Control animals:

yes, concurrent vehicle

Details on study design:

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

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: No


CLINICAL CHEMISTRY: Yes
- Time schedule for collection of blood: day 3 and at termination
- Animals fasted: No data
- How many animals: 5/sex/dose


URINALYSIS: Yes
- Time schedule for collection of blood: day 3 and at termination

NEUROBEHAVIOURAL EXAMINATION: No


- Gross pathology: YES
- Time schedule: at termination
- How many animals: 5/sex/dose

Histopathology: Yes
The following tissues were examined microscopically: lungs, trachea, larynx, bronchial lymph nodes, nose
(three transverse sections), and all gross lesions from all treated and control animals.

Sacrifice and pathology:

GROSS PATHOLOGY: Yes
HISTOPATHOLOGY: Yes

Other examinations:

Coagulation

Statistics:

not specified

Results and discussion

Results of examinations

Clinical signs:

effects observed, treatment-related

Mortality:

mortality observed, treatment-related

Body weight and weight changes:

effects observed, treatment-related

Food consumption and compound intake (if feeding study):

not examined

Food efficiency:

not examined

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

not examined

Ophthalmological findings:

not examined

Haematological findings:

not examined

Clinical biochemistry findings:

not examined

Urinalysis findings:

no effects observed

Behaviour (functional findings):

not examined

Organ weight findings including organ / body weight ratios:

not examined

Gross pathological findings:

no effects observed

Histopathological findings: non-neoplastic:

effects observed, treatment-related

Histopathological findings: neoplastic:

no effects observed

Details on results:

CLINICAL SIGNS AND MORTALITY
Mortality: all mice exposed to 500 ppm of formic acid died during the  first week of the study; a female of the 250 ppm group was killed  moribund on day 4 of exposure. 
Clinical signs: nasal discharge, increased preening, and labored  breathing in the 250 and 500 ppm groups.

BODY WEIGHT AND WEIGHT GAIN
Body weight gain: significantly lower than in controls from day 42  onwards, terminal body weight of males 81% (females 84%) compared to  controls.


ORGAN WEIGHTS
Small increases (~ 10%) in the relative kidney weight in males at 62.5.  125, and 250 ppm and in female exposed to 250 ppm were reported. Reduced  absolute and relative thymus weight was seen in mice exposed to 250 ppm;  relative lung weights were slightly increased in these groups.

GROSS PATHOLOGY
there were no gross lesions. Dried exudates was noted around  the nares of all mice at 500 ppm and 1 female at 250 ppm during the first  week of the study. The stomach and small intestines were distended with  air in animals that died. Distension was attributed to swallowing air  during mouth breathing which was enforced by the swelling and occlusion  of the nasal passages. 

HISTOPATHOLOGY: NON-NEOPLASTIC
Histopathological lesions were similar in male and female mice. They were  limited to the nasal passages, except at the 500 ppm level where they  wear also present in the larynx, pharynx, and trachea. The incidence and  severity increased with dose.  At 32 and 62.5 ppm the histopathological findings were limited to mild squamous metaplasia of the respiratory epithelium in 2 females.

Effect levels

1

Dose descriptor:

NOAEL

Effect level:

0.06 mg/L air

Sex:

male/female

Basis for effect level:

other: histopathological changes in the respiratory tract

2

Dose descriptor:

LOAEL

Effect level:

0.12 mg/L air

Sex:

male/female

Basis for effect level:

other: histopathalogical changes in the nose

Target system / organ toxicity

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.

Histopathology detail information:
==========================================================
                       Exposure concentration (ppm) 
                       0  31  62.5     125    250    500
----------------------------------------------------------
                                  Males

NOSE
Respiratory epithelium
squam. metaplasia      0  0   0       3(1.3) 4(1.3) 1(1.0)
inflammation           0  0   0       2(1.0) 4(1.2) 5(1.4)
necrosis               0  0   0       0      0      4(3.5)
Olfactory epithelium
degeneration           0  0   0       0      3(1.3) 1(2.0)
necrosis               0  0   0       0      0      3(2.0)
LARYNX
squam. metaplasia      0  0   0       0      0      5(2.8)
inflammation           0  0   0       0      0      3(1.0)
PHARYNX
necrosis               0  0   0       0      0      3(2.0)
 
                                  Females 

NOSE
Respiratory epithelium
squam. metaplasia      0  0   2(1.0)  3(1.3) 4(1.0) 0
inflammation           0  0   0       2(1.5) 5(1.4) 5(1.8)
necrosis               0  0   0       0      2(1.5) 5(3.6)
Olfactory epithelium
degeneration           0  0   0       0      2(2.0) 0
necrosis               0  0   0       0      1(1.0) 5(1.8)
LARYNX
squam. metaplasia      0  0   0       0      0      1(2.0)
inflammation           0  0   0       0      0      3(1.0)
necrosis               0  0   0       0      0      5(2.2)
PHARYNX
necrosis               0  0   0       0      0      2(1.0)
==========================================================
Average grade of severity is given in brackets: 1=minimal ; 2=mild; 3=moderate; 4=marked

The NOAEC in this study was determined to be 32 ppm (0.06 mg/l), based on histopathological changes in the respiratory tract.

Applicant's summary and conclusion

Executive summary:

Mortality was complete at 500 ppm of formic acid within one week. At 250 ppm, one female died and body weight was significantly decreased by 16 to 19% compared to controls.

Systemic toxicity was generally low. Findings during histopathology consisted of squamous metaplasia of the respiratory and olfactory epithelium in groups at 125 ppm and above. The incidence and severity increased with dose. Squamous metaplasia and inflammation in larynx, and necrosis in pharynx, were seen in animals at 500 ppm.

The NOAEC in this study was determined to be 32 ppm (0.06 mg/l), based on histopathological changes in the respiratory tract (2 cases of mild respiratory epithelium squamous metaplasia in females at 62.5 ppm). Mice were more susceptible than rats exposed to formic acid under the same conditions.