Phosphine

Repeated dose toxicity: inhalation

Administrative data

Endpoint:

chronic toxicity: inhalation

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: Study well-described and performed according to the Pesticide Assessment guidelines of the US-EPA.

Data source

Reference

Reference Type:

publication

Title:

A 2-year inhalation study of phosphine in rats

Author:

Newton P.E. et al.

Year:

1999

Bibliographic source:

Inhalation Toxicology, 11:693-708

Materials and methods

Test guideline

Test guideline 1

Qualifier:

according to guideline

Guideline:

other: US EPA Pesticides assessment guidelines, Subdivision F, Hazard Evaluation: Human and Domestic Animals, Section 83-5

Test guideline 2

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 453 (Combined Chronic Toxicity / Carcinogenicity Studies)

GLP compliance:

not specified

Limit test:

no

Test material

Test material information

Constituent 1

Reference substance name:

Phosphine

EC Number:

232-260-8

EC Name:

Phosphine

Cas Number:

7803-51-2

Molecular formula:

H3P

IUPAC Name:

phosphane

Details on test material:

In order not to exceed the lower explosive limit during exposure atmosphere generation, the phosphine was supplied as 1% in nitrogen. Impurities identified by the manufacturer in the phosphine were (ppm): N2<10, O2<1, total hydrocarbon<5, CO<1, CO2<0.3, AsH3<10, H2O<1 and H2<5

Test animals

Species:

rat

Strain:

Fischer 344

Sex:

male/female

Details on test animals or test system and environmental conditions:

The rats were approximatively 7 weeks at initiation of exposure. Diet and water were available ad libitum except during the actual exposures. Animals were randomly assigned to each exposure group.
The animals were housed within open-mesh, stainless steel cages in environmentally controlled rooms with regulated air changes and a 12-h light/12-h dark cycle. The same cages were used for both the exposure and nonexposure period.

Administration / exposure

Route of administration:

inhalation: gas

Type of inhalation exposure:

whole body

Vehicle:

air

Remarks on MMAD:

MMAD / GSD: Not applicable

Details on inhalation exposure:

All exposures were conducted in identical 16000 liter stainless steel and glass chambers. The chambers had pyramidal-shaped tops to facilitate mixing and were operated dynamically at 12 air changes per hour. The chambers were operated at a slight negative pressure relative to the surrounding area. Temperature, relative humidity and chamber airflow were monitored continuously and recorded every 30 min during the exposure.
The 1% phosphine in nitrogen mixture was delivered from the cylinder through stainless steel and Teflon lines to the inlet of each exposure chamber. The metered phosphine gas mixed with chamber supply air in the chamber inlet prior to entry into the exposure chamber. The metered phosphine flow to each chamber was monitored by digital mass flowmeters.

Analytical verification of doses or concentrations:

yes

Details on analytical verification of doses or concentrations:

For the analytical exposure levels, samples for gas chromatographic determination of the phosphine exposure levels were withdrawn hourly from a line being flushed with chamber air from the breathing zone of the animals. GC analyses were performed on a Tracor 540 using a flame photometric detector. Each day the GC was calibrated before exposure initiation and checked periodically throughout the exposure.

Duration of treatment / exposure:

5 days/week - 104 weeks

Frequency of treatment:

6 hours/day

Doses / concentrations

Doses / concentrations 1

Remarks:

Doses / Concentrations:
0.3 ppm
Basis:
analytical conc.

Doses / concentrations 2

Remarks:

Doses / Concentrations:
1 ppm
Basis:
analytical conc.

Doses / concentrations 3

Remarks:

Doses / Concentrations:
3.01 ppm
Basis:
analytical conc.

No. of animals per sex per dose:

60

Control animals:

yes, concurrent vehicle

Positive control:

No

Examinations

Observations and examinations performed and frequency:

All animals were observed at least twice a day for morbidity, mortality, injury and availability of food and water. A detailed clinical examination of each animal was performed once during each study week including general condition, skin, fur, eyes, ears, nose, oral cavity, thorax abdomen, external genitalia, limbs, feet, respiration and palpation of tissue masses. Ophtalmologic examinations were conducted by a veterinary ophtalmologist in all animals prior to initiation of the exposure and in all survivors prior to necropsy.
Body weight and food consumption were recorded at least once prior the initiation of exposure, weekly during the first 13 weeks and monthly thereafter.
After 52 week of exposure, blood and urine samples were collected to evaluate a wide range of hematological, biochemical and urological parameters.
Hematological parameters evaluated: leukocyte count (total and differential), erythrocyte count, hemoglobin, hematocrit, mean corpuscular volume, mean corpuscular hemoglobin, mean corpuscular hemoglobin concentration, platelet count, reticulocyte count.
Biochemical parameters evaluated: alkaline phosphatase, total bilirubin, aspartate aminotransferase, gamma glutamyltransferase, sorbitol dehydrogenase, urea nitrogen, creatinin, total protein, albumin, globulin, albumin/globulin ratio, glucose (fasting), total cholesterol, sodium, potassium, chloride, calcium, magnesium, phosphorus and phosphokinase.
Urological parameters evaluated: 16-h volume, color and appearance, pH, specific gravity, protein, glucose, ketones, urobilinogen, nitrites, bilirubin, occult blood, leukocyts and microscopy of spun deposit.

Sacrifice and pathology:

A complete postmortem examination was performed. The animals were exposed to phosphine up to the day of necropsy. The animals were euthanized by anesthesia via intraperitoneal injection of sodium pentobarbital to effect followed by exsanguination from the abdominal aorta.
Absolute and relative organ weights were measured and calculated for the brain, adrenals, heart, kidney, liver, lung and gonads.
Microscopic examination of formalin-fixed hematoxylin and eosin-stained paraffin sections was conducted for the following tissues for all animals in the control and high exposure level groups and all animals dying spontaneously or euthanized in extremis: adrena, aorta, bone, brain, eye, esophagus, stomach, duodenum, jejunum, ileum, cecum, colon, rectum, ovary, testis, epididymis, Harderian gland, heart, kidney, larynx, liver, lung, mandibular, mediastinal and mesenteric lymph nodes, mammary gland, nasopharynx, pancreas, pituitary, prostate, seminal vesicle, salivary gland, sciatic nerve, skeletal muscle, skin, spinal cord, spleen, thymus, thyroid/parathyroid, trachea, urinary bladder, uterus, cervix and vagina. In addition, the kidney, lung, liver, trachea and nasopharynx, were designated in the study protocol as potential target organs and were also evaluated in all groups.

Statistics:

Data collected at each interval for body weight, food consumption, clinical pathology data, and organ weight were analyzed using one-way analysis of variance (ANOVA). If no significance was observed (p>0.05), no further analysis was evaluated. If significance was observed, Bartlett's test for the homogeneity of variances was evaluated. If Bartlett's test was not significant (p>0.05), a Dunnett's test was performed. If the Bartlett's test was significant, a Welch t-test with a Bonferroni correction was performed. Where nonparametric statistical procedures were appropriate, rank transformation was conducted on the data and an ANOVA was performed on the ranks. If the ANOVA was not significant, a Mann-Whitney U-test was evaluated.
Intercurrent mortality data was analyzed using the Kaplan-Meier product-limit method. Each test article group was compared with the control group using the log-rank test. Tumor incidence data were analyzed using both survival-adjusted and unadjusted tests. The unadjusted tests were based on the incidence and number of sites examined for each tumor type. The Cochran-Armitage trend test was calculated and a Fischer's exact test was used to comprae each test substance group with the control group. Th survival adjusted test was conducted according to the prevalence/mortality methods.

Results and discussion

Results of examinations

Clinical signs:

no effects observed

Mortality:

no mortality observed

Body weight and weight changes:

no effects observed

Food consumption and compound intake (if feeding study):

no effects observed

Food efficiency:

not specified

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

not specified

Ophthalmological findings:

no effects observed

Description (incidence and severity):

All rats whatever groups and sex, demonstrated some degree of corneal superficial dystrophy which were representative of pathology that would be expected considering age, sex and strain.

Haematological findings:

no effects observed

Clinical biochemistry findings:

no effects observed

Urinalysis findings:

no effects observed

Behaviour (functional findings):

not specified

Immunological findings:

not specified

Organ weight findings including organ / body weight ratios:

no effects observed

Gross pathological findings:

no effects observed

Description (incidence and severity):

Corneal opacity was observed in some rats from all sex groups, including controls. It is a spontaneous degenerative lesion of the cornea known in Fischer 344 rats. It was not considered to be related to the phosphine exposure.

Neuropathological findings:

not specified

Histopathological findings: non-neoplastic:

no effects observed

Histopathological findings: neoplastic:

no effects observed

Description (incidence and severity):

The only statistically significant increase seen was in adenomas of the Islet cells in the pancreas in male rats (incidence of 5% in the 3 ppm group) but it was considered to be random and not phosphine related.

Effect levels

Key result

Dose descriptor:

NOAEC

Remarks:

104 weeks

Effect level:

> 3 ppm

Based on:

test mat.

Sex:

male/female

Basis for effect level:

other:

Remarks on result:

other: No adverse effects noted

Target system / organ toxicity

Key result

Critical effects observed:

no

Applicant's summary and conclusion

Conclusions:

The study was performed on rats during 104 weeks NOAEC > 3 ppm.
No treatment-related changes suggestive of a toxic or carcinogenic effect were observed.

Executive summary:

In a chronic toxicity study of phosphine, 60 male and female F344 rats per group were exposed via whole-body inhalation for 6h/day, 5 days/week for up to 104 weeks to mean concentrations of 0, 0.3, 1 and 3 ppm phosphine. There were no phosphine-related effects seen on clinical observations, body weight, food consumption, hematology, clinical chemistry, urinanalysis and ophthalmology. There were no phosphine-related macroscopic findings or effect on absolute or relative organ weights. No histomorphologic alterations attributable to phosphine exposure were seen. In conclusion, under the conditions of this study, there were no treatment-related changes suggestive of a toxic effect seen in rats following 2 years of whole-body inhalation exposure to 0.3, 1 or 3 ppm phosphine.