1,3-propanesultone

Carcinogenicity

Description of key information

1,3-Propanesultone has been found to be carcinogenic in rats and mice by any of several routes of administration (i.e. oral, dermal, subcutaneous, i.v., transplacental).

Key value for chemical safety assessment

Carcinogenicity: via oral route

Link to relevant study records

Reference

Reference 1

Endpoint:

carcinogenicity: oral

Type of information:

experimental study

Adequacy of study:

supporting study

Study period:

1970

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Study meets generally accepted scientific principles, acceptable for assessment

Qualifier:

no guideline followed

Principles of method if other than guideline:

- rats were treated orally by gavage once weekly at 30 mg/kg bw for 340 days

GLP compliance:

no

Species:

rat

Strain:

other: BD

Sex:

not specified

Details on test animals or test system and environmental conditions:

no data

Route of administration:

oral: gavage

Vehicle:

water

Details on exposure:

VEHICLE
- Concentration in vehicle: 3%

Analytical verification of doses or concentrations:

not specified

Duration of treatment / exposure:

- 340 days

Frequency of treatment:

- once weekly

Post exposure period:

- all animals were exposed untill death

Dose / conc.:

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

No. of animals per sex per dose:

- 12 animals were used

Details on study design:

- Dose selection rationale: 30 mg/kg bw (8.5% of LD50), since a low oral absorption has been expected

Observations and examinations performed and frequency:

- no data, only formation of tumors and mortality was described in the publication

Sacrifice and pathology:

GROSS PATHOLOGY: Yes
HISTOPATHOLOGY: Yes

Details on results:

CLINICAL SIGNS AND MORTALITY

- 2/12 animals died ahead of time
- 4/10 animals died between day 248 and 377 due to malignant tumors (2 in the nervous system, 1 subcutaneous, 1 nephroblastoma)

GROSS PATHOLOGY

- a few malignant tumours in remote organs were observed

Dose descriptor:

NOAEL

Based on:

test mat.

Sex:

not specified

Basis for effect level:

histopathology: neoplastic

Remarks on result:

not determinable

Reference 2

Endpoint:

carcinogenicity: oral

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Study meets generally accepted scientific principles, acceptable for assessment

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 451 (Carcinogenicity Studies)

Deviations:

not applicable

GLP compliance:

no

Species:

rat

Strain:

Crj: CD(SD)

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Charles River CD male and female rats were procured as weanlings from Charles River Breeding Laboratories
- Housing: 2 per large plastic cage (12 inches x l4 inches x 7 inches), on corncob bedding
- Diet: Wayne Lab Blox meal
- Water: ad libitum
- Acclimation period: 7 - 10 days of quarantine

ENVIRONMENTAL CONDITIONS
- animal rooms were air-conditioned

Route of administration:

oral: gavage

Vehicle:

water

Details on exposure:

PREPARATION OF DOSING SOLUTIONS:
- solutions (in water) were freshly prepared on the day of administration

VEHICLE
- water

Analytical verification of doses or concentrations:

no

Duration of treatment / exposure:

- first group (low dose): 60 weeks exposure, 60 weeks on study
- second group (high dose): 32 weeks exposure, 60 weeks on study

Frequency of treatment:

- twice weekly

Post exposure period:

- all rats were necropsied after 60 weeks

Dose / conc.:

28 mg/kg bw/day (nominal)

Dose / conc.:

56 mg/kg bw/day (nominal)

No. of animals per sex per dose:

- 26

Control animals:

yes

Details on study design:

- Dose selection rationale: the high dose correseponded to the experimentally determined MTD (acute, subacutly or subchronic pre-tests)
Because of the numerous mammary tumors developing in the females at the 18th week and the high mortality in males, administration of the high dose was discontinued at the 32nd week

Positive control:

N-2-fluorenylacetamide

Observations and examinations performed and frequency:

DETAILED CLINICAL OBSERVATIONS: Yes
- Time schedule: twice daily, 7 days a week, for toxicologic effects or deaths
- presence of palpable masses was noted during such inspections

BODY WEIGHT: Yes
- Time schedule for examinations: weekly during the initial month of the study and biweekly thereafter

FOOD CONSUMPTION AND COMPOUND INTAKE (if feeding study):
- determined during the initial week and the fourth week of each subsequent 4-week period

HAEMATOLOGY: No

CLINICAL CHEMISTRY: No

URINALYSIS: No

NEUROBEHAVIOURAL EXAMINATION: No

Sacrifice and pathology:

GROSS PATHOLOGY: Yes
HISTOPATHOLOGY: Yes

- Moribund rats and those with large tissue masses were killed during the course of the chronic study. In addition, at the end of dosing, 5 animals of each sex from the group on the higher dose were killed and necropsied, and stained sections of the tissues were examined microscopically to detect any changes. These animals were used for calculation of tumor incidence but not survival rate .
- All rats were necropsied and the tissues examined histopathologically .

- the following tissues were examined routinely :
cerebrum, cerebellum, pituitary gland, spinal cord plus vertebrae, lung, heart, mediastinum, thymus, thyroid gland, parathyroid gland,
liver, spleen, pancreas, adrenal gland, kidney, urinary bladder, ovary, uterus or testis, accessory sex organ, esophagus, stomach, intestinal tract, and any abnormal tissue or mass .

Statistics:

Probabilities of survival were estimated by the product-limit procedure of Kaplan and Meier, which is commonly called the "life table method." Animals were statistically censored as of the time they died of other than natural causes or were found to be missing. For statistical analyses of a possible dose-related effect on survival, the method of Cox for testing 2 groups of equality and Tarone's extensions of Cox's methods for testing for a dose-related trend were used.
One-tailed P-values were reported for all tests except the departure from linearity test, which was only reported when its two-tailed P-value was less than 0.05. Also, the one-tailed Fisher's exact probability test and the Cochran-Armitage test for linear trend in proportions, with continuity correction were used. The treated groups were always compared to a "matched" negative or vehicle control, as appropriate.

Clinical signs:

effects observed, treatment-related

Description (incidence and severity):

At the 45th week animals on the low dose began showing signs of central nervous system disturbances. Therefore, the experiment was terminated at the 60th week.

Dermal irritation (if dermal study):

not examined

Mortality:

mortality observed, treatment-related

Description (incidence):

Propanesultone caused high mortality, and only 4 males and 6 females survived at 52 weeks at the high-dose level.

Body weight and weight changes:

not specified

Food consumption and compound intake (if feeding study):

not specified

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

Immunological findings:

not examined

Organ weight findings including organ / body weight ratios:

not examined

Gross pathological findings:

not specified

Neuropathological findings:

not examined

Histopathological findings: non-neoplastic:

not specified

Histopathological findings: neoplastic:

effects observed, treatment-related

Description (incidence and severity):

Propanesultone was tested at a sufficiently high dose to be toxic, but not enough animals survived to assess its potential for inducing late-appearing tumors. However, the treated animals of each sex had a highly significant incidence of malignant glioma of both the cerebrum and the cerebellum at each dose level (see table). In addition, each dose group of female rats had a significantly elevated incidence of mammary adenocarcinoma. A somewhat elevated incidence of granulocytic leukemia was found in each sex. Incidence of adenocarcinomas of the small intestine was 4 - 12% in the treated animals of each sex, but was zero in the controls. Two squamous cell carcinomas of the ear duct occurred in the male rats and 2 occurred in the female rats, but none developed in the matched or pooled controls. All of these cancers are rarely found in negative control animals.

Details on results:

Propanesultone caused high mortality, and only 4 males and 6 females survived at 52 weeks at the high-dose level. Because of the numerous mammary tumors developing in the females at the 18th week and the high mortality in males, administration of the high dose was discontinued at the 32nd week.
At the 45th week animals on the low dose began showing signs of central nervous system disturbances. Therefore, the experiment was terminated at the 60th week.

Propanesultone was tested at a sufficiently high dose to be toxic, but not enough animals survived to assess its potential for inducing late-appearing tumors. However, the treated animals of each sex had a highly significant incidence of malignant glioma of both the cerebrum and the cerebellum at each dose level (see table). The gliomas were astrocytomas and were often detected grossly as pea-sized areas of discoloration in the cerebrum or cerebellum. In addition, each dose group of female rats had a significantly elevated incidence of mammary adenocarcinoma. A somewhat elevated incidence of granulocytic leukemia was found in each sex. Incidence of adenocarcinomas of the small intestine was 4 - 12% in the treated animals of each sex, but was zero in the controls. Two squamous cell carcinomas of the ear duct occurred in the male rats and 2 occurred in the female rats, but none developed in the matched or pooled controls.
All of these cancers are rarely found in negative control animals. Thus propanesultone induced significant increases in malignant gliomas and mammary adenocarcinomas, and the incidences of leukemia, cancer of the small intestine, and squamous cell carcinoma of the ear duct were increased over those in controls.

Dose descriptor:

NOAEL

Based on:

test mat.

Sex:

male/female

Basis for effect level:

histopathology: neoplastic

Remarks on result:

not determinable

Dose descriptor:

T25

Remarks:

(daily exposure for 104 weeks)

Effect level:

1.6 mg/kg bw/day (nominal)

Based on:

test mat.

Sex:

female

Basis for effect level:

histopathology: neoplastic

Dose descriptor:

T25

Remarks:

(adapted to workplace situation)

Effect level:

4.48 mg/kg bw/day (nominal)

Based on:

test mat.

Sex:

female

Basis for effect level:

histopathology: neoplastic

Tumour frequency in rats after administration of 1,3 propanesultone for 60 or 32 weeks by gavage:

Tumour type	0 mg/kg		28 mg/kg (60 weeks)		56 mg/kg (32 weeks)
	Males	Females	Males	Females	Males	Females
Cerebrum Malignant Glioma	1/16 (6 %)	1/16 (6 %)	10/26 (38 %)	12/26 (46 %)	11/26 (42 %)	12/26 (46 %)
Cerebellum Malignant Glioma	0/16 (0 %)	0/16 (0 %)	6/26 (23 %)	8/26 (31 %)	11/26 (42 %)	4/26 (15 %)
Mammary gland Adenocarcinoma		0/16 (0 %)		6/26 (23 %)		13/26 (50 %)
Leukemia	0/16(0 %)	0/16(0 %)	0/28(0 %)	2/26(8 %)	4/26(15 %)	3/26(12 %)
Small intestine carcinoma	0/16 (0 %)	0/16(0 %)	3/26(12 %)	2/26(8 %)	3/26(12 %)	1/26(8 %)

T25 deviation according to Norwegian Pollution Control Authority:

Lowest dose with a significant increased tumor incidence:

The highest incidence of malignancies at the lowest dose level (i.e. in the cerebrum in females) is used.

Control: 1/16 (6 %)

28 mg/kg bw: 12/26 (46 %)

net %: [12 x (100/26) – 1 x (100/16)]/[100-1 x (100/16)] = 43%

 

Daily dose per kg bodyweight during the exposure period:

28 mg/kg bw, twice per week: i.e. 8.0 mg/kg bw/day

 

Dose of this incidence of gliomas when administration started after 6 weeks and exposure is for 24 months:

60/104 x 60/104 x 8.0 mg propanesultone/kg bw/day = 2.7 mg propanesultone/kg bw/day

 

T25 after 24 months (daily exposure):

T25 = 25/43 x 2.7 mg/kg bw/day = 1.6 mg/kg bw/day

Adaptation to workplace situation (exposure for 5 days/week, 48 weeks/year over 40 years):

T25(oral, workplace) = 1.6 mg/kg bw/d x 7/5 x 52/48 x 75/40 = 4.48 mg/kg bw/d

 

Endpoint conclusion

Endpoint conclusion:

adverse effect observed

Dose descriptor:

T25

4.48 mg/kg bw/day

Species:

rat

Quality of whole database:

Studies meets generally accepted scientific principles, acceptable for assessment.

Carcinogenicity: via inhalation route

Endpoint conclusion

Endpoint conclusion:

no study available

Dose descriptor:

T25

7.9 mg/m³

Species:

rat

Quality of whole database:

No study for the inhalation route available. Thus, the chronic oral gavage study in rats reported by Weisburger et al. (1981) has been used to derive an oral T25 value and to extrapolate to the inhalation exposure route.

Carcinogenicity: via dermal route

Link to relevant study records

Reference

Endpoint:

carcinogenicity: dermal

Type of information:

experimental study

Adequacy of study:

supporting study

Study period:

1976

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Study meets generally accepted scientific principles, acceptable for assessment

Qualifier:

no guideline followed

Principles of method if other than guideline:

The effects of limited and prolonged dermal exposure of mice to propanesultone were investigated with specific reference to the occurrence of skin and systemic neoplasia by applying the test solutions in different concentrations to the skin.

GLP compliance:

no

Species:

mouse

Strain:

other: CFI, C3H, CBah

Sex:

male/female

Details on test animals or test system and environmental conditions:

- mice of three strains were used: CF1 (an albino strain derived from Carworth Farm No. 1), C3H (obtained from the Laboratory Animal Centre, Carshalton) and CBah (a "hairless" strain derived from the Chester Beatty Institute, London).
- mice were bred in specific pathogen- ree conditions at Tunstall Laboratory
- six weeks of age at the beginning of treatment
- water and cubed 86S diet (obtained from Grain Harvesters, Wingham, Kent) were provided ad libitum

Animals for the comparative long-term study:
The mice were caged in groups of 5, of the same sex and strain, each receiving the same treatment.

Animals for the limited exposure study:
The mice (CFI) were individually housed.

Route of administration:

dermal

Vehicle:

other: benzene or toluene

Details on exposure:

Comparative long-term study:

The backs of the CF1 and C3H mice were shorn with fine electric clippers prior to the first treatment and then once weekly for the duration of the experiment. The test solutions and solvents were applied to the skin with fine brushes, twice weekly for 56 weeks. The volume applied on each occasion was estimated to be 0.05 - 0.1 mL/mouse. There were four treatment groups in each strain (CFI, C3H and CBah):

1) 2.5% w/v propanesultone in benzene for 4 weeks then in toluene for 1 year
2) 2.5 % w/v ß-propiolactone in benzene for 4 weeks then in toluene for 1 year
3) benzene for 4 weeks then toluene for 1 year
4) shorn only with no chemical exposure


Limited exposure study:

The hair on the back was shorn with fine electric clippers before treatment started and, then, weekly for the 78-week test period.
Treatment of all mice in a single block was started on the same day. The test solutions (0.1 mL) were applied to the dorsal skin using all-glass syringes. The treatment regimes were as follows:

1) one application of toluene; thereafter no further treatment
2) one application of 2.5% w/v propanesultone in toluene; thereafter no further treatment
3) 10 applications of 2.5 % w/v propanesultone in toluene on alternate days; thereafter no further treatment
4) one application of 25 % w/v propanesultone in toluene; thereafter no further treatment

Analytical verification of doses or concentrations:

not specified

Duration of treatment / exposure:

Comparative long-term study:
- 56 weeks (one application, treatment group 1,2 and 4)

Limited exposure study:
- 19 days (treatment group 3)

Frequency of treatment:

Comparative long-term study:
- twice weekly

Limited exposure study:
- one single treatment (group 1, 2, 4) and 10 applications on alternate days (group 3)

Post exposure period:

- Comp. long-term study: end of treatment until week 58
- Lim. exposure study: end of treatment until week 78

Dose / conc.:

2.5 other: % (nominal)

Remarks:

Comp. long-term study and Lim. exposure study

Dose / conc.:

25 other: % (nominal)

Remarks:

Lim. exposure study

No. of animals per sex per dose:

Comparative long-term study:
- 25 males and 25 females of each strain per group

Limited exposure study:
- 48 males and 48 females per group

Observations and examinations performed and frequency:

Comparative long-term study:
Records were kept of the gross appearance of the treated skins.

Limited exposure study:
Each animal was examined weekly and the size, appearance and position of all skin lesions were recorded. The criteria used for the initial recording of the presence of a skin tumour were that the lesion had reached a diameter of 2 mm and had persisted for 2 weeks. As a measure of the rate of tumour growth, the times when tumours reached 6 mm and 10 mm respectively were also recorded.

Sacrifice and pathology:

Comparative long-term study:
All mice that died, unless autolysis was too advanced, and all survivors, killed at the end of the study, were subjected to a detailed necropsy with a histological examination of the skin and major organs.

Limited exposure study:
After 78 weeks, the mice were killed and subjected to a detailed necropsy and a histological examination of skin and the major viscera for the presence of neoplasms. Similar examinations were carried out on animals dying or killed because of ill-health during the experiment, with the exception of
those not surviving beyond the first 7 days after exposure.

Both studies:
Skin tumours were classified on histological criteria as benign or malignant including probably malignant epithelial tumours. The epidermal tumours seen were papillomas, basal cell carcinomas, carcinomas and adenomas of adnexae, and squamous cell carcinomas. The dermal tumours found were fibromas, fibrosarcomas, haemangiomas, haemangiosarcomas and myxosarcomas.
Some epidermal tumours regressed spontaneously and could not be examined histologically. For the purpose of statistical analysis, such tumours, provided that they had reached a diameter of 2 mm and had persisted for 2 weeks, were classified as papillomas. Similarly, a tumour diagnosed as malignant was deemed to have become malignant at the time when it reached a diameter of 10 mm or, when the animal bearing it died, if this size had not been attained.

Statistics:

Actuarial analyses were carried out on both skin and systemic tumour data. For each class of tumour (e.g. 2 mm skin tumours, systemic lung tumours) the significance of the number of tumours occurring in the treatment groups was obtained by testing against the expected incidence, using a Chi 2 statistic. Lifetables were constructed for the incidence of 2 mm and malignant tumours in the 25 % propane sultone treatment group in the limited exposure study. Similar analyses were carried out on the data from the comparative longterm study, although only the length of survival was available to carry out the age-adjusted analysis.

Comparative long-term study

 

Survival:

In all control groups, the survival to the end of the trial (58 weeks) was 60%, or higher. This contrasts with the treated mice of all three strains exposed to propane sultone, where survival was much less. No CF1 of C3H mice survived exposure to propane sultone for 58 weeks, while only 12 % of the CBah mice exposed to propane sultone survived for 58 weeks.

 

Skin tumours:

No tumours were seen in the untreated and solvent controls whereas animals of all three strains exposed to propane sultone developed tumours of the dorsal treated skin. Tumours of both the epidermis and dermis were identified histologically, the majority being of epidermal origin, except in the C3H males, where the predominant tumour type was a dermal fibrosarcoma.

There was an apparent difference between strains in the number of animals ultimately developing skin tumours after repeated skin application of propane sultone; 40% of the CF1, 55% of the C3H and 79% of the CBah strain. Apparent differences were observed between the sexes in two strains in terms of skin tumour response to propane sultone exposure, with 71% of the CF1 males and 91% of C3H males having tumours compared to 12% and 24% of the females respectively. In contrast, in the CBah strain 87% of the males and 72% of the females developed skin tumours. However, the low incidences of tumours in CF1 and C3H females were associated with poor survival. When an actuarial analysis of the tumour risk is performed, which makes an allowance for differences in survival, the apparent strain and sex differences could not be confirmed.

 

Systemic tumours:

Systemic neoplasms were classified as tumours of the lympho-reticular tissues, the lung, female reproductive system and other tumours. The tumour incidence is given in the table below. There was a significant increase in the incidence of lympho-reticular cell sarcomas in CF1 mice exposed to propane sultone. C3H females treated with propane sultone had a higher incidence of tumours of the mammary gland and uterus than had the control C3H females. At necropsy, some animals, both in control and treated groups, had grossly enlarged spleens. Histologically, this was associated with an intense proliferation of myeloid elements in the red pulp of the affected animals.

Limited exposure study

 

Survival:

During the first 4 days of the study, 12 males and 2 females died after exposure to a single dose of a 25% w/v solution of propane sultone in toluene. This finding is consistent with the known acute toxicity of propane sultone. The number of survivors to the end of trial was significantly less in all treatment groups than in the solvent controls, with the exception of males exposed to a single application of a 2.5% w/v solution. No mice survived for 78 weeks after exposure to a single application of the 25% w/v solution. Ten applications of the 2.5% w/v solution resulted in no females and only 8% males surviving for 78 weeks. Females exposed to a single application of a 2.5% w/v solution had a 44% survival rate, whereas the males given this single dose had a survival rate comparable to that of the controls.

 

Skin tumours.

No skin tumours were found in any of the solvent-treated control CFl mice. There was a highly significant increase in the incidence of tumours of the treated skin in mice surviving the initial toxic effects of exposure to a Single application of a 25% w/v solution of propane sultone. A not uncommon clinical finding in these animals was ulceration seen shortly after application of the dose. These lesions healed subsequently with scarring. 29 out of 36 males and 26 out of 46 females developed tumours and 70% of these tumours were papillomas. The other skin tumours were either carcinomas or sarcomas, many of them being highly anaplastic. Single or ten sequential applications on alternate days of a 2.5% w/v solution caused a minimal, but not statistically significant, increased incidence of tumours at the site of application. Most of the tumours were first recorded 4 - 10 weeks after exposure and many reached diameters of 2 - 3 cm after a growth period of 3 - 5 weeks. About half the total number of tumours that developed underwent complete spontaneous regression and were therefore classified as papillomas for the purposes of statistical analysis. Several tumours with an initial rapid growth rate showed ischaemia and sloughing of the external mass, which was followed by regrowth at the primary site. Histologically, these proved to be malignant. Metastases to local and distant sites occurred in two males with anaplastic carcinomas and in three females with fibrosarcomas. To assess the probability of skin tumours developing in male and female mice after a single application of a 25% w/v solution of propane sultone, the data on the growth rates of individual tumours were analysed. During the period from 0 - 8 weeks for 2 mm tumours and 0 - 30 weeks for malignant tumours, the lifetables were similar for both sexes. After these periods, the risk to the male increased for both categories of tumours, whereas the risk to the females remained steady.

 

Systemic tumours:

Systemic neoplasms were classified as tumours of the lympho-reticular tissues and the lung, with all other tumours grouped under one heading since no specific tumour type made a predominant contribution to the total. Exposure of males and females to a single application of a 25% w/v solution or to 10 applications of 2.5% w/v solution resulted in a significant increase in the risk of tumour development for all three categories of systemic tumours, the latter dosage regime producing the greater risk. The single application of the 2.5% w/v solution increased the risk in females of developing lung or other tumours, but this risk was not realised in males having a similar exposure.

Table 1:  Incidence of skin tumours in three strains of mice after repeated skin application of Propane sultone (2.5% w/v solutions) for 56 weeks

Treatment	Strain	Group size	Number of animals with tumours				Total number of animals with tumours
			Benign		Malignant
			With one tumour	With more than one tumour	With one tumour	With more than one tumour (incl. benign)
Untreated	CFl           Males	24					0
	Females	23					0
	C3H           Males	25					0
	Females	20					0
	CBah           Males	25					0
	Females	25					0
Solvents	CFl           Males	22					0
	Females	25					0
	C3H           Males	25					0
	Females	21					0
	CBah           Males	24					0
	Females	25					0
Propane sultone	CFl           Males	21	6		6	3	15
	Females	24	3				3
	C3H           Males	22	1	1	16	2	20
	Females	25	2		3	1	6
	CBah           Males	23	2		18		20
	Females	25	2	1	13	2	18

Table 2: Incidence of systemic tumours in three strains of mice after repeated skin application of Propanesultone (2.5% w/v solutions) for 56 weeks

Treatment	Strain	Group size	Number of animals in each classifcation
			Lympho-reticular	Lung	Reproductive system	Other	With at least one tumour	With more than one tumour
Untreated	CFl     Males	24	1	5		1	7
	Females	23	1	2	1		4
	C3H    Males	25				16	16
	Females	20			1		1
	CBah   Males	25				4	4
	Females	25					0
Solvents	CFl      Males	22		4		3	7
	Females	25	3	4	1		7	1
	C3H    Males	25	1			12	12	1
	Females	21			2	2	4
	CBah   Males	24				2	2
	Females	25				1	1
Propane sultone	CFl      Males	21	12	9			18	3
	Females	24	17	2	2		18	2
	C3H    Males	22	2	5		11	13	4
	Females	25	2	1	18	1	17	5
	CBah   Males	23	2			1	3
	Females	25	2		5		6	1

Endpoint conclusion

Endpoint conclusion:

adverse effect observed

Dose descriptor:

T25

9.96 mg/kg bw/day

Species:

rat

Quality of whole database:

Study meets generally accepted scientific principles. However, it is not suitable to derive a T25 value. Thus, the chronic oral gavage study in rats reported by Weisburger et al. (1981) has been used to derive an oral T25 value and to extrapolate to the dermal exposure route.

Mode of Action Analysis / Human Relevance Framework

The considerable mutagenic potency of the alkylating agent 1,3-propanesultone – demonstrated in a large number of test systems in vitro and in vivo (see also chapter Genotoxicity) - and its ability to induce various systemic tumours shows that it is an unequivocally mutagenic substance with potent germ cell mutagen properties. No metabolic activation is needed to evolute its mutagenic properties.

Justification for classification or non-classification

Based on the available data regarding carcinogenicity 1,3-propanesultone is subject to classification and labelling:

Carc. 1B, H350 according to Regulation 1272/2008/EC.

Additional information

Animal data

1,3-propanesultone is a highly reactive alkylating agent. Its carcinogenic potency has been demonstrated in several studies in mice and rats.

 

In the key study with Charles River CD rats (Weisburger et al., 1981) 28 mg or 56 mg 1,3-propanesultone per kg bodyweight were administered by gavage two times per week. The low dose was administered for 60 weeks, while the high dose was given for 32 weeks and the animals were killed 28 week later (weighted mean dose was 29.9 mg/kg bw). Both doses led to various types of malignant tumors, primarily tumors of the brain with a possibility of induction of leukemia and carcinomas of the small intestine (see table below).

 

Tumour frequency in rats after oral administration of 1,3-propansultone.

Tumour type	0 mg/kg		28 mg/kg (60 weeks)		56 mg/kg (32 weeks)
	Males	Females	Males	Females	Males	Females
Cerebrum Malignant Glioma	1/16 (6 %)	1/16 (6 %)	10/26 (38 %)	12/26 (46 %)	11/26 (42 %)	12/26 (46 %)
Cerebellum Malignant Glioma	0/16 (0 %)	0/16 (0 %)	6/26 (23 %)	8/26 (31 %)	11/26 (42 %)	4/26 (15 %)
Mammary gland Adenocarcinoma		0/16 (0 %)		6/26 (23 %)		13/26 (50 %)
Leukemia	0/16 (0 %)	0/16 (0 %)	0/28 (0 %)	2/26 (8 %)	4/26 (15 %)	3/26 (12 %)
Small intestine carcinoma	0/16 (0 %)	0/16 (0 %)	3/26(12 %)	2/26(8 %)	3/26(12 %)	1/26(8 %)

Oral treatment of rats via gavage once weekly at 30 mg/kg bw/day for 340 days revealed a few malignant tumours in remote organs (nervous system, subcutaneous, nephroblastoma (Druckrey, 1970).

Doak et al. (1976) investigated the carcinogenic activity of 1,3-propanesultone by skin painting. Application of a 2.5% (w/v) solution of 1,3-propanesultone in benzene, twice weekly for 4 weeks, followed by application of a 2.5% (w/v) solution in toluene, twice weekly for 1 year, to the skin of CFI, C3H or CBah mice (groups of 21 - 25 mice per sex, 140 mice in total) led to the development of skin tumours in 59% of the mice (33 carcinomas, 32 sarcomas, 21 papillomas, 6 probably malignant tumours, 1 fibroma). Systemic tumours were observed in 51% of the mice consisting of 36 lymphosarcomas and 1 reticulosarcoma of the spleen, 11 hepatomas, 17 lung tumours and 27 other tumours. In 26 animals myeloid hyperplasia was noted.

Applied once to the skin of CFI mice, the 2.5% solution of 1,3-propanesultone in toluene caused enlargement of the spleen, thymus or lymph nodes in 2/48 males and 7/48 females but did not induce skin tumours within the 78-week observation period.

When the same concentration was applied to mouse skin ten times, the spleen, thymus and lymph nodes were enlarged in 19/48 males and 35/48 females. Skin tumours developed by week 4 in 5/48 males and 2/48 females. After a single dermal application of 0.1 mL of a 25% (w/v) solution of 1,3-propanesultone in toluene (corresponding to approximately 830 mg/kg bw/d) skin tumours developed in 29/36 males and 26/46 females. The first epidermal papillomas developed within 5 weeks and most developed within 10 weeks. At the same time, spleen, thymus and lymph nodes were enlarged. During the first 4 days 14/96 (15%) animals died; autopsy of these animals was not carried out.

Overall, the incidence of local and systemic tumours was much higher after chronic treatment than after single or short term treatment.

Subcutaneous injection of 1,3-propanesultone in rats yielded injection-site sarcomas (Druckrey et al., 1970). A single subcutaneous dose of 100 mg/kg produced local sarcomas in all of 18 treated rats (Druckrey et al., 1970). A single intravenous bolus of 150 mg/kg in 32 rats caused the death of 1 rat with a brain tumor after 235 days and the death of 9 others with malignant tumors of a variety of sites within 459 days (Druckrey et al., 1970). A single intravenous dose of 20 mg/kg given to pregnant rats on day 15 of gestation produced malignant neurogenic tumors in their offspring (Druckrey et al., 1970).

Human data

1,3 -propanesultone is only industrially used where rigorous risk management measures are in place during production and use. Therefore, human exposure can principially excluded and consequently, no epidemiological data on 1,3-propanesultone is available. However, during manufacturing mainly in the 1950s and 1960s exposure of a limited amount of workers could have occurred and the medical history of some cases could be traced (Bolt and Golka, 2004). As cerebral gliomas are the main systemic tumours induced by 1,3-propanesultone experimentally, the occurrence of a glioblastoma among previously exposed persons appears conspicuous. Three intestinal malignancies were recorded among the cases observed. Also noteworthy is one case of a duodenal carcinoma, normally a rare human malignancy. Two haematopoietic/lymphatic malignancies of different nature have been observed, and there was one case of a renal cell carcinoma. These malignancies observed within a group of persons exposed to 1,3-propanesultone appear consistent with the expectations from the available animal studies.

Derivation of T25 values

The dermal study in mice (Doak et al., 1976) is not suitable to derive a T25 value as only a 2.5% solution of 1,3-propanesultone was tested and the corresponding dose in mg/kg bw is unknown. Moreover, 1,3-propanesultone was dissolved in toluene which is classified for skin irritation. Observations focused on mortality and tumour formation, whereas skin reactions were not examined. Consequently, skin irritation might have occurred during the 1-year dermal application, influencing the local and systemic tumour incidence due to local inflammation or the enhancement of dermal absorption.

Thus, the chronic oral gavage study in rats reported by Weisburger et al. (1981) has been used in the following to derive an oral T25 value and to extrapolate to the dermal and inhalation exposure route.

Lowest dose with a significant increased tumor incidence:

The highest incidence of malignancies at the lowest dose level (i.e. in the cerebrum in females) is used.

Control: 1/16 (6%); 28 mg/kg bw dose group: 12/26 (46%)

net %: [12 x (100/26) – 1 x (100/16)]/[100 -1 x (100/169)] = 43%

Daily dose per kg bodyweight during the exposure period: 28 mg/kg bw, twice per week: i.e. 8.0 mg/kg bw/day

Dose of this incidence of gliomas when administration started after 6 weeks and exposure is for 24 months:

60/104 x 60/104 x 8.0 mg 1,3-propanesultone/kg bw/day = 2.7 mg 1,3 -propanesultone/kg bw/day

T25(oral) after daily exposure for 104 weeks: T25(oral) = 25/43 x 2.7 mg/kg bw/day = 1.6 mg/kg bw/day

This T25 value is identical with the value established by the Norwegian Pollution Control Authority in 1997. This value reflects daily exposure for 104 weeks and has to be adapted to the workplace situation (exposure for 5 days/week, 48 weeks/year over 40 years):

T25(oral, workplace) = 1.6 mg/kg bw/d x 7/5 x 52/48 x 75/40 = 4.48 mg/kg bw/d.

The oral T25 value of 4.48 mg/kg bw/d is applied in the derivation of the dermal and inhalation T25 value.

In the absence of specific absorption data following oral, dermal or inhalation exposure, the acute toxicity data can be used to establish a factor for the oral-to-inhalation and oral-to-dermal route extrapolation.

The inhalation LC50 in the rat after a 6-hour exposure is approximately 1.7 mg/L (OTS, 1992). Taking into account a rat breathing volume of 0.29 m³/kg bw and assuming 100% absorption the corresponding systemic dose is 490 mg/kg bw. In comparison, oral LD50 values ranging between 100 and 350 mg/kg bw have been reported for the rat (OTS, 1992; MAK, 1985; Druckrey et al., 1970), indicating that inhalation absorption will not be higher than oral absorption. Thus, the factor of 1 for oral-to-inhalation extrapolation is justified.

The only species where both dermal and oral acute toxicity data are available is the mouse. Whereas the oral LD50 is 400 mg/kg bw (OTS, 1992), the dermal LD50 is > 830 mg/kg bw (830 mg/kg bw caused 15% death; Doak et al., 1972). This data indicates that dermal absorption will be more than 2-fold lower than oral absorption, justifying a factor of 0.5 for oral-to-dermal extrapolation.

 

Taking into account the T25 (oral, workplace) of 4.48 mg/kg bw/d, the 8-h standard respiratory volume of 0.38 m³/kg bw for the rat, the adjustment of the respiratory volume for light activity of 6.7 m³/10 m³ and the oral-to-inhalation route extrapolation factor of 1 the T25 (inhalation, workplace) can be calculated as:

 

T25 (inhalation, workplace) = 4.48 mg/kg bw/d / 0.38 m³/kg bw x 1 x 6.7 m³/10 m³ = 7.9 mg/m³

 

Taking into account the T25 (oral, workplace) of 4.48 mg/kg bw/d and the oral-to-dermal route extrapolation factor of 0.5 the T25 (dermal, workplace) can be calculated as:

 

T25 (dermal, workplace) = 4.48 mg/kg bw/d / 0.5 = 9.96 mg/kg bw/d.