Registration Dossier

Toxicological information

Repeated dose toxicity: inhalation

Currently viewing:

Administrative data

Endpoint:
sub-chronic toxicity: inhalation
Type of information:
migrated information: read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
key study
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: Study followed accepted scientific practice

Data source

Reference
Reference Type:
publication
Title:
Unnamed
Year:
1997
Report date:
1997

Materials and methods

Test guideline
Guideline:
other: US TSCA guidelines
Principles of method if other than guideline:
28 day rat nose only inhalation test using vapor of phosphorus tribromide (PBr3) which rapidly forms hydrogen bromide (HBr) and phosporus acid (H3PO3).
GLP compliance:
not specified
Limit test:
no

Test material

Constituent 1
Reference substance name:
Phosphorus tribromide
EC Number:
232-178-2
EC Name:
Phosphorus tribromide
Cas Number:
7789-60-8
IUPAC Name:
phosphorus(3+) tribromide
Details on test material:
- Name of test material (as cited in study report): Phosphorus tribromide
- Molecular formula (if other than submission substance): PBr3
- Molecular weight (if other than submission substance): 270.686
- Substance type: inorganic
- Physical state: colorless to pale yellow liquid
- Analytical purity: 99.99 %
- Storage condition of test material: stored under nitrogen and used in hood
- Other: Specific gravity: 2.850 Vapor pressure: 0.27 psi at 54 °C
- Source: Aldrich Chemical Company

Test animals

Species:
rat
Strain:
Fischer 344
Sex:
male/female
Details on test animals or test system and environmental conditions:
TEST ANIMALS
- Source: Charles River (CDF[F-344]/CrlBR)
- Weight at study initiation: Males 100 to 125 grams; females 75 to 100 grams
- Fasting period before study:
- Housing: two per cage in clear plastic cages with hardwood chip bedding, in laminar-flow rooms
- Diet (e.g., ad libitum): ad libitum except during exposure
- Water (e.g., ad libitum): ad libitum except during exposure
- Acclimation period: two week quarantine period
- Other: Animal care in acordance with Guide for the Care and Use of Laboratory Animals prepared by the Institute of Laboratory Animal Resources, National Research Council, National Academy Press, 1996 and the Animal Welfare Act of 1966 as amended

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 21 to 25 °C
- Photoperiod (hrs dark / hrs light): 12/12 hours

IN-LIFE DATES: Dates covered October, 1996 to May 1997 (acute through 28 day study).

Administration / exposure

Route of administration:
inhalation: vapour
Type of inhalation exposure:
nose only
Vehicle:
air
Details on inhalation exposure:
GENERATION OF TEST ATMOSPHERE / CHAMBER DESCRIPTION
- Exposure apparatus: Cannon 52 units within a set of Plexiglass boxes
- Method of holding animals in test chamber: Plexiglas restraining tubes
- Source and rate of air: dried laboratory air
- Method of conditioning air: Air dryer reduced humidity
- System of generating test substance: Gas tight syringes (1.0, 0.5, and 0.25 mL) used for direct delivery (needle tip evapoaration) into the10 L dried air stream. Sage syringe pumps used to control input of test article
- Temperature, humidity, pressure in air chamber: Humidity < 3 % as measured by HY-CAL detector.
- Air flow rate: minimum air flow delivery of 500 mL/animal
- Treatment of exhaust air: bypass and containment dump employed. Bypass air input used before and after the 4 hours exposures to supply clean air, and was used along with the PBr3 input carrier air to control the concentration of the exposure atmospheres. The Cannon chambers were vented through a vacuum pump which delivered the vapor to a water scrubber exhaust system. The containement areas were further isolated from the general laboratory area through use of a separate exhaust line which vented the enclosures.

TEST ATMOSPHERE
- Brief description of analytical method used: A bromide specific ion electrode permitted quantification of the test material through analysis of the bromide ion absorbed in an ionic strength buffer (pH 4.0). In order to monitor the lower concentrations, the ratio of vapor to buffer had to be increased from 10:1 air/absorber to 20:1 and 40:1. Sixty-mL plastic syringes containing 5.0 mL buffer were used to quantify the 50 mL vapor samples and acted as the reaction vessels for the absorption of test article. Multiple absorption samples were required to analyze the lower chamber concentrations.
- Samples taken from breathing zone: yes/no

VEHICLE (if applicable): not applicable
Analytical verification of doses or concentrations:
yes
Details on analytical verification of doses or concentrations:
Analytical: The test material PBr3 reacts rapidly with water vapor present in air forming hydrogen bromide and phosphonic acid. It is also a good brominating agent. These properties prevented the usual methods for measuring exposure concentrations – IR absorbance or gas chromatography. The method used for analysis used water reactivity to free bromide ion for analysis, then use of a bromide combination specific ion electrode (ATI Orion) to determine bromide concentration. This was validated by quantitative addition of PBr3 and the formation of bromide ion – a set of three bubblers in series demonstrated that > 95 % was absorbed in the first tube. The rapid reactivity and sample line loss negated a continuous analysis. A direct method for analysis was chosen for confirming the nominal concentration by spot sampling every 20 minutes.

Bromide analysis: A separate syringe for each concentration was used and a double absorption for the mid chamber sample, and 4 x 50 mL samples for the low dose chamber. The probe was soaked in buffer (94 Series Ionic Strength adjuster, ATI Orion, pH to 4.0 for solution) at a concentration near that of the expected mid range level sample. An appropriate range of standards were made for the exposure set, bracketing low and high values. The standard 0.1 M sodium bromide from Orion was diluted to 1 uM in decade values. If the low end of the standard curve was non-linear with the log concentration, the standards were made between the decade vaules (such as 2, and 4.5 µM and 20 and 45 µM). PBr3 values were then calculated from the bromide ion concentration. Over 90 % of the samples were between 10 and 100 µM.

Duration of treatment / exposure:
4 hours per day, excluding weekends, for 28 days (total of 20 exposures).
Frequency of treatment:
Once daily, for 20 exposures (5 days per week over 28 days)
Doses / concentrationsopen allclose all
Remarks:
Doses / Concentrations:
0.3 mg/L
Basis:
nominal conc.
Remarks:
Doses / Concentrations:
0.1 mg/L
Basis:
nominal conc.
Remarks:
Doses / Concentrations:
0.03 mg/L
Basis:
nominal conc.
Remarks:
Doses / Concentrations:
0.0 mg/L
Basis:

No. of animals per sex per dose:
10 males and 10 females per treatment group
Control animals:
yes
Details on study design:
- Dose selection rationale: 5 day repeated dose preliminary showed differences between high dose (0.51 mg/L measured) and control animals in body weights on days 3 and 4, and gross and microscopic lesions of the anterior nasal passages, and in the trachea of one high dose animal. One rat in the mid dose group (0.16 mg/L) had minimal inflammation of anterior nasal passages. No microscopic lesions were seen in the low dose or the controls.
- Rationale for animal assignment: random

Examinations

Observations and examinations performed and frequency:
CAGE SIDE OBSERVATIONS: Yes, on each exposure day
- Time schedule: daily, on exposure days


DETAILED CLINICAL OBSERVATIONS: Yes, on each exposure day
- Time schedule: daily, on exposure days

BODY WEIGHT: Yes
- Time schedule for examinations: Prior to initial exposure, then weekly

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: At necropsy
- Anaesthetic used for blood collection: Yes, CO2 inhalation
- Animals fasted: Yes, 12 hours before necropsy
- How many animals: all animals
- Parameters checked in table [No.?] were examined.

CLINICAL CHEMISTRY: Yes
- Time schedule for collection of blood: at necropsy
- Animals fasted: Yes, 12 hours before necropsy
- How many animals: all animals
- Parameters checked in table [No.?] were examined.

URINALYSIS: No

NEUROBEHAVIOURAL EXAMINATION: No data


OTHER:
Sacrifice and pathology:
GROSS PATHOLOGY: Yes (see attached background document List of tissues
HISTOPATHOLOGY: Yes (see attached background document List of tissues
Statistics:
Body weights were analyzed using the repeated multivariate analysis of variance with Scheffe pairwise comparisons (Barcikowski, R.J., 1983). Hematology, clinical chemistry, and organ weights were analyzed using a two-factorial analysis of variance with multivariate comparisons (Barcikowski, R.J., 1983). Histopathology data were analyzed with use of a Fischer Exact Test, or, if not valid, Yates' corrected Chi-square (Zar, J.R., 1974).

Results and discussion

Results of examinations

Clinical signs:
no effects observed
Mortality:
no mortality observed
Body weight and weight changes:
effects observed, treatment-related
Description (incidence and severity):
decreases in body weights in all treatment groups and controls
Haematological findings:
effects observed, treatment-related
Description (incidence and severity):
decreased platelets, increased monocyte and eosinophil %, increased mean corpuscular volume
Clinical biochemistry findings:
effects observed, treatment-related
Description (incidence and severity):
decreased chloride, calcium, ALT, triglycerides
Organ weight findings including organ / body weight ratios:
no effects observed
Gross pathological findings:
no effects observed
Histopathological findings: non-neoplastic:
effects observed, treatment-related
Description (incidence and severity):
mild inflammation anterior nasal passages in high dose group
Histopathological findings: neoplastic:
no effects observed

Effect levels

open allclose all
Dose descriptor:
NOAEC
Effect level:
0.1 mg/L air (nominal)
Based on:
test mat.
Sex:
male/female
Basis for effect level:
other: Microscopic findings of mild inflammation of the anterior nasal passages, minor serum chemistry and hematology effects seen in treated animals. Note: The NOAEC of PBr3 of 0.1 mg/L equates to 0.0916 mg/L HBr.
Dose descriptor:
LOAEC
Effect level:
0.3 mg/L air (nominal)
Based on:
test mat.
Sex:
male/female
Basis for effect level:
other: Microscopic findings of mild inflammation of the anterior nasal passages seen in this concentration group. Note: This LOAEC value for PBr3 is equivalent to 0.2748 mg/L HBr.

Target system / organ toxicity

Critical effects observed:
not specified

Any other information on results incl. tables

Attached tables:

Table 6 Body Weights of Male Rats Exposed for 28 days to Phosphorus Tribromide via Nose-only Inhalation

Table 7 Body Weights of Female Rats Exposed for 28 days to Phosphorus Tribromide via Nose-only Inhalation

Table 8 Mean Values of Serum Chemistries Parameters for Male Rats Exposed for 28 days to Phosphorus Tribromide via Nose-only Inhalation

Table 9 Mean Values of Serum Chemistry Parameters for Female Rats Exposed for 28 days to Phosphorus Tribromide via Nose-only Inhalation

Table 10 Blood Hematology Values for Male Rats Exposed for 28 days to Phosphorus Tribromide via Nose-only Inhalation

Table 11 Blood Hematology Values for Female Rats Exposed for 28 days to Phosphorus Tribromide via Nose-only Inhalation

Table 12 Absolute Organ Weights and Organ-To-Body Weight Ratios of Male Rats Exposed for 28 days to Phosphorus Tribromide via Nose-only Inhalation

Table 13 Absolute Organ Weights and Organ-To-Body Weight Ratios of Female Rats Exposed for 28 days to Phosphorus Tribromide via Nose-only Inhalation

Applicant's summary and conclusion

Conclusions:
The NOAEC of PBr3 when given by nose only exposure to male and female F-344 rats for 4 hours a day, 5 days per week for 20 exposures in 28 days is 0.1 mg/L (equivalent HBr exposure would be 0.0916 mg/L). The LOAEC, based on histopathology findings of mild inflammation in the anterior nasal passages was 0.3 mg/L (equivalent HBr exposure would be 0.274 mg/L). Decreased body weights were seen in treated and control groups and were thought to be due to restraint in the exposure chambers. Increased serum chloride levels in the exposed animals only was thought to be an artifact due to interference of ionized bromide in the test material with the serum chloride assay. There were no signs of toxic stress, or changes in organ weights in treated animals compared to control.
Executive summary:

Phosphorus tribromide (PBr3) hydrolyzes into HBr and phosphonic acid. In a 28 day study in Fischer 344 rats exposed for 4 hours per day, five days per week, to 0.03, 0.1 or 0.3 mg/L PBr3 showed no signs of toxic stress, alterations of body weight, or changes in organ weights compared to control animals. Minor serum chemistry and hematology effects were seen in treated animals. Microscopic tissue findings were limited to rats of the 0.3 mg/L group and consisted of mild inflammation of the nasal passages. A concentration of 0.1 mg/L was the no observable adverse effect level (NOAEL) in a 28 day inhalation study.