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Repeated dose toxicity: dermal

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chronic toxicity: dermal
Type of information:
migrated information: read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
key study
Study period:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: see 'Remark'
The read-across approach is based on the assumption, that Tetrakis(hydroxymethyl)phosphonium chloride (THPC, CAS 124-64-1), as part of the technical product 'Tetrakis(hydroxymethyl)phosphonium chloride, oligomeric reaction products with urea' (THPC-urea, CAS 27104-30-9), is the relevant, most hazardous compound. The (local) mode of action based on direct chemical reactivity is the same in both compounds. Additionally the read-across approach is based on the worst-case assumption that the reaction mixture THPC-urea is as reactive as THPC. In the confirmatory information it becomes obvious, that THPC is at least 6 times more hazardous than THPC, oligomeric reaction products with urea. For the detailed justification of the read-across hypothesis see “overall remarks, attachments”. When considering both the read-across hypotheses, the direct read-across from data obtained with technical THPC (80%) onto technical THPC-urea (65-68%) do not lead to an underestimation of the hazard. No further uncertainty factor, e.g. AF=2 for read-across, is considered to be necessary for deriving a DNEL(THPC-urea) from NOAEL(THPC). Published test report from Cancer Research and US-EPA assessment report thereof. Evaluated data from a reliable secondary source (US-CPSC).

Data source

Referenceopen allclose all

Reference Type:
Report date:
Reference Type:
secondary source
Report date:

Materials and methods

Test guideline
no guideline followed
other: one treatment group of 60 female mice (limit test at MTD, dermal) four no-treatment control groups that were used for these tests as well as for other concurrent experiments (249 mice).
Principles of method if other than guideline:
Limit test at MTD: one treatment group of 60 female mice; skin application 3 times weekly for 496 days (mouse chronic)
four no-treatment control groups that were used for these tests as well as for other concurrent experiments (249 mice).
GLP compliance:
not specified
Limit test:

Test material

Constituent 1
Chemical structure
Reference substance name:
Tetrakis(hydroxymethyl)phosphonium chloride
EC Number:
EC Name:
Tetrakis(hydroxymethyl)phosphonium chloride
Cas Number:
Molecular formula:
tetrakis(hydroxymethyl)phosphonium chloride
Details on test material:
Name: Tetrakis(hydroxymethyl)phosphonium chloride (THPC)
Molecular formula: C4H12O4P.Cl
Structure: [Cl-].OC[P+](CO)(CO)CO
Molecular weight: 190.56
Substance type: ionic substance
Physical state: solid
Further details (analytical purity etc): 80% aqueous THPC

Test animals

Details on test animals or test system and environmental conditions:
random-bred female ICR/Ha Swiss mice (ARS/Sprague-Dawley Division, The Mogul Corp., Madison, Wis.) were acclimated to laboratory conditions
for 2 weeks, and treatments were begun when they were 6 to 8 weeks old. The mice were housed 6/cage on sterile hardwood chips (Betta Chip; Fisher & Son, Bound Brook, N. J.) in stainless steel cages, fed Purina laboratory chow and water ad libitum, and weighed monthly. The animal rooms were maintained at 22 to 24°C.

Administration / exposure

Type of coverage:
not specified
other: aceton-water (9:1)
Details on exposure:
external dose: 2 mg THPC per 0.2 ml aceton-water (9:1)
The dosages used in all experiments were based on short-term toxicity evaluations (4 to 6 weeks); the highest possible doses that gave
minimal cytotoxic effects, as determined by histopathological examination, were used for the chronic exposures.
Analytical verification of doses or concentrations:
Duration of treatment / exposure:
skin application 3 times weekly for 496 days
Frequency of treatment:
skin application 3 times weekly for 496 days
Doses / concentrations
Doses / Concentrations:
2 mg/application
nominal per unit area
No. of animals per sex per dose:
one treatment group of 60 female mice (limit test at MTD, dermal)
four no-treatment control groups that were used for these tests as well as for other concurrent experiments (249 mice).
Control animals:
yes, concurrent no treatment
yes, concurrent vehicle
Positive control:
No addition of tumor inductor or promotor.
Study hypothesis is, the possible liberation of formaldehyde and hydrochloric acid from free THPC in the fabric. Formaldehyde and hydrochloric acid are known to be in equilibrium with the animal and human carcinogen bis(chloromethyl)ether (Van Duuren 1978).


Observations and examinations performed and frequency:
All compounds were used in well-ventilated hoods, and the mice were housed there for at least 2 hr after treatment. All skin treatments were
continued for the duration of the experiment. Animals were examined regularly and scored, and the findings were charted once monthly.
Sacrifice and pathology:
Animals in poor health or with large tumor masses were killed. Except for the cranial region, animals were completely autopsied at the end of the
experiment or at death. Samples of all abnormal-appearing tissues and organs were excised for histopathological diagnosis. In addition, routine
histopathology was performed on skin, liver, and kidney in all animals dying during the test period and in 20% of all animals killed at the end of the
test. All tissue sections were fixed in 10% formalin, proc essed, blocked in paraffin, and stained with hematoxylin and eosin for histopathological
examination. Included in the protocols were groups given vehicle only; no treatment groups were included in the protocols.
Other examinations:
Skin lesions were diagnosed clinically as papillomas when they reached 1 cu mm in size and persisted for 30 days or more or when they were confirmed histopathologically.
The p values given in the table were assigned by means of computation of x2 analyses in which the tumor
incidences in the test groups were compared with a composite of 4 no-treatment control groups that were used for
these tests as well as for other concurrent experiments (249 mice).

Results and discussion

Results of examinations

Clinical signs:
effects observed, treatment-related
Dermal irritation:
effects observed, treatment-related
mortality observed, treatment-related
Body weight and weight changes:
not specified
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:
not examined
Behaviour (functional findings):
not examined
Organ weight findings including organ / body weight ratios:
not specified
Gross pathological findings:
effects observed, treatment-related
Histopathological findings: non-neoplastic:
effects observed, treatment-related
Histopathological findings: neoplastic:
effects observed, treatment-related
Details on results:
THPC was inactive in induction of skin tumors in skin painting studies.
THPC is a quaternary compound. Such compounds do not cross membranes very readily, therefore, they are not absorbed via the skin and poorly
absorbed from mucuous membranes. The chloride salts of quaternary bases are not likely to generate active chloride ions that could then help to
form bischloromethyl ether from the THPC.

Effect levels

open allclose all
Dose descriptor:
other: maximal tolerated dose (dermal)
Effect level:
2 other: mg/0.2 mL external dose
Based on:
act. ingr.
Basis for effect level:
other: minimal cytotoxic (local irritation) effect to mouse skin
Dose descriptor:
Effect level:
100 mg/kg bw/day (actual dose received)
Based on:
act. ingr.
Basis for effect level:
other: minimal effect on mouse skin, no systemic toxicity

Target system / organ toxicity

Critical effects observed:
not specified

Any other information on results incl. tables

No significant increases in tumors were observed when THPC (2 mg/animal) in acetone:water was tested for carcinogenic activity

by dermal application 3 times/week for 496 days (VanDuuren et al. 1978). Of the 59 treated animals necropsied, 17 lung (papillary)

tumors and 1 forestomach (papilloma) were observed, compared to 90 lung (papillary) tumors and 7 forestomach tumors out of the

249 untreated mice necropsied (p>0.05). Of the 29 mice treated with acetone:water (90:10) and examined, there were 7 lung

(papillary) tumors.

THPC was inactive in induction of skin tumors in skin painting studies.

The maximal tolerated dose (MTD dermal) of technical THPC is 2 mg/mouse per day. (Mouse bw 18g, body surface 75cm2)

external dose= 2mg/0.2ml (acteon:water 9:1)=10g/L (1%)

MTD=NOAEL (dermal, local) = 2mg/10% body surface mouse= 2mg/ 7.5 cm2 = 0.27 mg/cm2.

NOAEL (dermal, systemic)= 2mg/18g mouse= 100mg/kg bw/day

Applicant's summary and conclusion

The dermal toxicity study did not provide indications for systemic toxicity. Only slightly local effects were observed at the dose level applied.
In this chronic dermal test, based on minimal local irritation, a MTD of 2 mg THPC/animal=2mgTHPC/7.5cm2 = 0.25 mg/cm2, corresponding to 100 mg/kg bw/day (vehicle: aceton:water=9:1) what was identified to be the NOAEL in mice.