Dimethyl methylphosphonate

Carcinogenicity

Administrative data

Endpoint:

carcinogenicity: oral

Type of information:

experimental study

Adequacy of study:

supporting study

Reliability:

3 (not reliable)

Rationale for reliability incl. deficiencies:

other: Survival rate too low

Data source

Reference

Reference Type:

publication

Title:

Unnamed

Year:

1987

Materials and methods

Test guideline

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 451 (Carcinogenicity Studies)

Principles of method if other than guideline:

Evaluation of test substance carcinogenic potential after 2 years oral administration to test animals

GLP compliance:

no

Remarks:

well documented study peer reviewed study

Test material

Test material information

Constituent 1

Reference substance name:

Dimethyl methylphosphonate

EC Number:

212-052-3

EC Name:

Dimethyl methylphosphonate

Cas Number:

756-79-6

Molecular formula:

C3H9O3P

IUPAC Name:

dimethyl methylphosphonate

Details on test material:

- Name of test material (as cited in study report): Dimethyl methylphosphonate; Synonyms: Fyrol DMMP; Methyl phosphonic acid, dimethyl ester; DMMP; Methanephosphonic acid dimethyl ester; Dimethyl methanephosphonate
- Molecular formula (if other than submission substance): C3H9O3P
- Molecular weight (if other than submission substance): 124.1
- Analytical purity: ~98% for lot No. 4182-2, ~99% - > 99% for lots No. L120381, 1114L-6-l or 1114L-2-1
- Composition of test material, percentage of components: 0.04% - 0.06water and 0.47-1.1% total impurities
- Lot/batch No.: 4182-2; L120381; 1114L-6-l; 1114L-2-1
- Stability under test conditions and storage condition of test material: stability studies with the gas chromatographic indicated that dimethyl methylphosphonate was stable as a bulk chemical when kept for 2 weeks at temperatures of up to 60° C. The test substance at 0.6% in corn oil was stable when stored at room temperature for up to 7 days. A subsequent stability study performed at the study laboratory indicated that dimethyl methylphosphonate/corn oil mixtures are stable for 14 days under refrigeration. In the 2-year studies, dose mixtures were stored at 4° C for no longer than 13 days.

Test animals

Species:

rat

Strain:

Fischer 344

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: the male and female F344/N rats used in these studies were produced under strict barrier conditions at Frederick Cancer Research Center under a contract to the Carcinogenesis Program. Breeding stock for the foundation colonies at the production facility originated at the National Institutes of Health Repository. Animals shipped for study were progeny of defined microflora-associated parents that were transferred from isolators to barrier-maintained rooms.
- Age at study initiation: 4-5 weeks (placed on study at 7-8 weeks age)
- Weight at study initiation: see Table 1
- Fasting period before study: none
- Housing: Polycarbonate (Lab Products, Inc., Garfield, NJ, and Hazleton Systems, Aberdeen, MD); 5 animals per cage
- Diet (e.g. ad libitum): NIH 07 Rat and Mouse Ration (Zeigler Bros., Inc., Gardners, PA)
- Water (e.g. ad libitum): Acidified to pH 2.5
- Acclimation period: 20 days; the animals were quarantined. Thereaft;er, a complete necropsy was performed on five animals of each sex and species to assess their health status.

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 22.2-24.4°C
- Humidity (%): 30-70%
- Air changes (per hr): 12-15 room air change per hour

Administration / exposure

Route of administration:

oral: gavage

Vehicle:

corn oil

Details on exposure:

PREPARATION OF DOSING SOLUTIONS:
dose volume 6.5 ml/kg; test substance was formulated with corn oil with a Polytron mixer and resuspended daily with a magnetic stirrer

Analytical verification of doses or concentrations:

yes

Details on analytical verification of doses or concentrations:

During the 2-year studies, the dose preparations were analyzed at approximately 8-week intervals. The dose mixtures were prepared within specifications 94% of the time (within ±10% of the target concentration). Only 3/47 dose formulations were determined to be out of specifications (within ±13%). Referee analysis periodically performed by the analytical chemistry laboratory, found good agreement was found between the results at the two laboratories.
During the study, deaths occurred in April 1983 in low dose (male mice dosed in parallel). Special analyses were therefore performed on the contents of the dosing containers and their corresponding archive samples. The concentrations in the archive samples were within the specified limits, whereas that of the high-dose sample taken in the animal room was high (134% of target), and the low-dose sample taken in the animal room was low (79% of target). Because the archive samples were determined to be within specifications, it would appear that a dosing accident or misdosing due to improper handling or re-suspending of the dose mixture occurred in the animal room on these days.

Duration of treatment / exposure:

103 weeks

Frequency of treatment:

5 days per week

Doses / concentrations

Remarks:

Doses / Concentrations:
0, 500 and 1000 mg/kg bw per day
Basis:
actual ingested
gavage

No. of animals per sex per dose:

50

Control animals:

yes, concurrent vehicle

Details on study design:

- Dose selection rationale: based on the results of the 13-week study

Positive control:

none

Examinations

Observations and examinations performed and frequency:

CAGE SIDE OBSERVATIONS: Yes
- Time schedule: all animals were observed two times per day and palpated once each 4 weeks

DETAILED CLINICAL OBSERVATIONS: Yes
- Time schedule: clinical signs were recorded once per week (also see above

DERMAL IRRITATION (if dermal study): No

BODY WEIGHT: Yes
- Time schedule for examinations: body weights by cage were recorded once per week for the first 13 weeks of the studies and once per month thereafter. Mean body weights were calculated for each group.

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 AND: No data

OPHTHALMOSCOPIC EXAMINATION: No data

HAEMATOLOGY: No (also see pathology)

CLINICAL CHEMISTRY: No

URINALYSIS: No

NEUROBEHAVIOURAL EXAMINATION: No

Sacrifice and pathology:

GROSS PATHOLOGY: Yes; animals found moribund and those surviving to the end of the studies were humanely killed. A necropsy was performed on all animals including those found dead, unless they were excessively autolyzed, cannibalized, missexed, or found missing. Thus, the number of animals from which particular organs or tissues were examined microscopically varies and is not necessarily equal to the number of animals that were placed on study. During necropsy, all organs and tissues were examined for grossly visible lesions.

HISTOPATHOLOGY: Yes; tissues were preserved in 10% neutral buffered formalin, embedded in paraffin, sectioned, and stained with hematoxylin and eosin. Tissues examined microscopically are: cecum, colon, costochondral junction, duodenum, esophagus, eyes, gallbladder (mice), gross lesions and tissue masses, heart, ileum, jejunum, kidneys, larynx, liver, lungs and mainstem bronchi, mammary gland, mandibular and mesenteric lymph nodes, nasal cavity, pancreas, parathyroids, pituitary gland, prostate/testes/seminal vesicles or ovaries/uterus, rectum, regional lymph nodes, salivary glands, sciatic nerve, skin, spinal cord, spleen, sternum including marrow, stomach, thyroid gland, thigh muscle, thymus, trachea, and urinary bladder.

Other examinations:

None

Statistics:

see below

Results and discussion

Results of examinations

Details on results:

CLINICAL SIGNS
No compound-related clinical signs were recorded.

MORTALITY
Estimates of the probabilities of survival for male and female rats administered test substance at the doses used in these studies and for vehicle controls are shown in Table 1. In male rats, the number of survivors in both the low dose group (after week 88) and the high dose group (after week 82) was significantly lower than that in the vehicle controls (Tables 1&2). The survival of high dose female rats was significantly lower than that of the vehicle controls after week 63 (P<0.05; P<0.01 between weeks 76 and 101). Survival of low dose female rats was comparable to that of the vehicle controls.

BODY WEIGHT AND WEIGHT GAIN
Mean body weights of high dose male rats were 5%-10% lower than those of the vehicle controls between weeks 28 and 76 and 10%-24% lower between weeks 80 and 104 (Table 2). Mean body weights of high dose female rats were 8%-12% lower than those of the vehicle controls after week 80. Mean body weights of low dose male and female rats were comparable to those of the vehicle controls throughout most of the studies.

GROSS PATHOLOGY AND HISTOPATHOLOGY

- Renal effects: administration of test substance to male rats increased the average severity of nephropathy and caused mineralization (calcification) of the collecting tubules in the renal papilla (overall incidences of 12/50; 41/50; 36/49, respectively for the vehicle control, low dose and high dose group), hyperplasia of the transitional epithelium lining the renal pelvis and overlying the renal papilla (0/50; 23/50; 21/49), and focal hyperplasia of the renal tubular epithelium (0/50; 8/50; 9/49).

Administration of test substance to male rats was also associated with the occurrence of rare renal tubular cell adenocarcinomas (0/50; 2/50; 3/49) and papillomas of the transitional epithelium lining the renal pelvis (0/50; 7/50; 3/49); a transitional cell carcinoma occurred in a low dose male rat. There were no tubular cells or transitional cell neoplasms of the kidney in female rats.

- Hematopoietic system effects: The incidence of mononuclear cell leukemia was increased in high dose male rats (10/50; 11/50; 17/50).

- Thyroid gland effects: C-Cell carcinomas, considered a nonfatal tumor, occurred in male rats with a significant positive trend (1/49, 4/50, 4/49); the incidence in the high dose group was significantly greater than that in the vehicle controls, but the incidences of C-cell adenomas (3/49, 0/50, 1/49) or carcinomas (combined; 4/49, 4/50, 5/49) in dosed male rats were not significantly different from that in the vehicle controls by the incidental tumor test.

The incidences of follicular cell adenomas or carcinomas (combined; 0/49, 1/50, 0/49) in dosed male rats were increased by the life table trend test but only marginally by the incidental tumor trend test, the latter being the more appropriate test for nonfatal tumors. The incidences of thyroid gland tumors were not increased in female rats.

- Multiple organs effects: Mesotheliomas in the tunica vaginalis in male rats (0/50, 4/50, 6/50) occurred with a significant, positive trend; however, the incidence of total mesotheliomas at all sites was only marginally increased (2/50, 5/50, 6/50; historical control: 20/250) when analyzed by the incidental, tumor trend, test, and the incidence-of mesotheliomas (all sites) in dosed animals was not greater than the vehicle control incidence in pairwise comparisons with the vehicle controls by the life table test.

- Nasolacrimal duct effects: Chronic inflammation was observed at an increased incidence in high dose male rats (male: vehicle control, 1/50; low dose, 1/50; high dose, 8/50); this lesion was not notably increased in dosed females (0/50; 0/50; 2/50).

Effect levels

1

Dose descriptor:

NOAEL

Effect level:

500 mg/kg bw/day (actual dose received)

Sex:

female

Basis for effect level:

other: no evidence of carcinogenic activity of test substance was observed for female F344/N rats given doses of 500 or 1000 mg/kg

Remarks on result:

other: Effect type: carcinogenicity (migrated information)

2

Dose descriptor:

LOAEL

Effect level:

500 mg/kg bw/day (actual dose received)

Sex:

male

Basis for effect level:

other: see 'Remark'

Remarks on result:

other: Effect type: carcinogenicity (migrated information)

Any other information on results incl. tables

Table 1: Survival of rats in the 2-year gavage study

Sex		0 mg/kg	500 mg/kg	1000 mg/kg
Male	Animals initially in study	50	50	50
	Non-accidental deaths before termination (a)	22	33	45
	Accidentally killed	1	0	1
	Killed at termination	26	17	4
	Died during termination period	1	0	0
	Survival P values (b)	<0.001	<0.031	<0.001
Female	Animals initially in study	50	50	50
	Non-accidental deaths before termination (a)	20	17	27
	Killed at termination	30	32	23
	Died during termination period	0	1	0
	Survival P values (b)	0.044	0.720	0.049
(a) Includes animals killed in a moribund condition; (b) The result of the life table trend test is in the vehicle control column, and the results of the life table pairwise comparisons with the vehicle controls are in the dosed columns.

 

Table 2: Mean body weights and survival (only time period where deaths occurred are presented)

Week on study	Mean body weights and number of animals still alive at indicated time period
	Vehicle control (0 mg/kg)				Low dose (500 mg/kg)						High dose (1000 mg/kg)
	Mean BW (g)		Survivors		Mean BW (g)		BW %of control		Survivors		Mean BW (g)		BW %of control		Survivors
	Male	Female	Male	Female	Male	Female	Male	Female	Male	Female	Male	Female	Male	Female	Male	Female
0	163	119	50	50	162	126	99	106	50	50	158	123	97	103	50	50
24	410	213	50	50	408	214	100	100	50	50	392	208	95	98	49	50
36	439	229	49	50	437	225	100	98	50	50	417	223	95	97	49	50
40	450	231	49	50	439	227	98	98	50	50	418	226	93	98	49	49
44	456	238	49	50	448	231	98	97	49	50	425	230	93	97	49	49
48	464	445	49	49	455	236	98	96	49	50	428	235	92	96	49	49
52	467	254	48	49	463	247	99	97	48	50	435	245	93	96	49	49
56	475	262	47	49	468	254	99	97	45	49	438	252	92	96	46	45
60	484	266	43	49	472	258	98	97	41	46	445	254	92	95	43	42
64	487	276	42	49	478	269	98	97	39	46	450	265	92	96	43	42
68	485	283	40	49	480	276	99	98	38	45	445	274	92	97	40	40
72	488	291	40	48	478	283	98	97	37	44	439	277	90	95	37	40
76	487	298	39	48	478	286	98	96	34	44	437	285	90	96	35	37
80	489	303	39	47	477	287	98	95	32	44	434	278	89	92	27	30
84	484	304	38	46	471	294	97	97	30	44	423	276	87	91	24	29
88	479	306	37	44	466	293	97	96	25	44	413	283	86	92	17	27
92	480	310	36	43	468	301	98	97	24	42	406	283	85	91	10	26
96	473	313	35	37	457	296	97	95	23	39	386	281	82	90	10	26
100	468	314	29	34	459	293	98	93	19	35	369	283	79	90	8	24
104	451	318	27	30	416	293	92	92	17	33	343	280	76	88	4	23
BW: body weight