Iron sulphide

Endpoint summary

Description of key information

Key studies were available for iron sulfide for oral and dermal acute toxicity, both showing LD50 values above 2000 mg/kg bw with absence of clinical or pathological observations. For read across purpose, comparison with a worst case source chemical iron dichloride was made, showing systemic effects and lethality after (300 and) 2000 mg/kg bw. Therefore iron sulfide is safe compared to more water soluble iron salts, most probably due to limited water solubility and limited systemic absorption.

Key value for chemical safety assessment

Acute toxicity: via oral route

Link to relevant study records

Reference

Endpoint:

acute toxicity: oral

Type of information:

read-across from supporting substance (structural analogue or surrogate)

Adequacy of study:

supporting study

Justification for type of information:

See attached read-across justification

Reason / purpose for cross-reference:

read-across source

Vehicle:

corn oil

Mortality:

All animals received 2000 mg/kg body weight died after one hour and one animal received 300 mg/kg body weight was found dead on day 2.

Clinical signs:

other: Hypoactivity, piloerection, prone position, reddening and edema on ears, fore-legs and hind-legs, dyspnea, incomplete eyelid opening and hypothermia were observed in the three dead animals of 2000 mg/kg and in one dead animall of 300 mg/kg group. These si

Gross pathology:

No abnormalities were observed in all survived animals. At 2000 mg/kg body weight, nasal discharge (reddish or clear) was observed in all animals externally. Hemorrhage on lymphatic nodes, stomach and intestine in all animals and hemorrhage on thymus in one animal were observed. One animal showed hypertrophy of pancreas and other one animal showed the hypertrophy of spleen.
At 300 mg/kg body weight, hemorrhage on lymphatic nodes, and intestine were observed in the dead animal. And there was no abnormality by the macroscopic examination of survived animals after the study termination on day 15.

Table 1. Mortality and clinical signs

Group	Dose (mg/kg)	Animal No.	Clinical signs observed in days after treatment						Mortality (%)
			Hours on day 1 after treatment				Day 2	Day 3-15
			1	2	3	4
1	300	F1	H, P	H, P	H, P	H	N	N	0/3 (0)
		F2	H, P	H, P	H, P	H	Ss	N
		F3	H, P, S	H, P	H, P	H	Ss	N
2	300	F4	H, P	H, P	H, P	H	N	N	1/3 (33)
		F5	P	H, P	H, P	H	Ss	N
		F6	H.Le.P.Pp	H.Le.P.Pp	Dy.H.Le.P.Pp	Ht.H.Le.P.Pa	FD	-
3	2000	F7	H.P.Pp.†		FD		-	-	3/3 (100)
		F8	H.P.Pp.Di.†		FD		-	-
		F9	H.P.Pp.†		FD		-	-

Dy: Dyspnea; FD: Found Dead; H: Hypoactivity; Ht: Hypothermia; Ie: Incomplete eyelid opening;

N: Normal; P: Piloerection; Pa: Pale; Pp: Prone position; S: Salivation; Ss: Soft stool; Di: Diarrhea;

†: Reddish change and edema on ears, fore-legs and hind-legs.

 

Table 2. Summary of group mean body weights

Group	Dose (mg/kg)	Mean body weight ± S.D. (g)
		Day 1	Day 8	Day 15
1	300	163.9 ± 6.9	206.6 ± 6.3	228.7 ± 12.5
2*	300	161.6 ± 1.7	207.4 ± 7.7	226.7 ± 6.6
3**	2000	162.5 ± 6.1	-	-

  * One animal was found dead 2 days after administration.

** All animals were found dead 2 days after administration.

 

Table 3. Gross necropsy findings (Group summary)

Group			1	2	3
Dose (mg/kg)			300	300	2000
Number of animals examined at terminal kill			3	3	3
External Finding	No gross finding Reddish nasal discharge Clear nasal discharge
Internal Finding	No gross finding		3	2
	Hemorrhage	Intestine Lymphatic node Ovaries Pancreas Stomach Thymus		1 1 1	3 3   2 1 1
	Hypertrophy	Pancreas Spleen			1 1

Interpretation of results:

Toxicity Category IV

Remarks:

Criteria used for interpretation of results: EU

Conclusions:

All animals dosed at 2000 mg/kg body weight and one animal dosed at 300 mg/kg body weight were found dead. The acute lethal oral dose (LD50 cut-off values) to rats of the test article, Iron dichloride was estimated to be between 300 and 2000 mg/kg body weight under the test conditions.

Executive summary:

Three female Sprague-Dawly rats were administered 300 mg/kg bw read-across substance iron dichloride by single oral gavage prepared in corn oil according to Acute Toxic Class method. Formulations were administered by single oral gavage at a dose volume of 10 mL/kg body weight. After the test article has been administered, food was withheld for 3 to 4 hours. Since no mortality was observed in this first group, three additional rats were administered 300 mg/kg bw Iron dichloride by single oral gavage. One animal of this second group was found dead on day 2. Three additional rats were tested at the limiting dose of 2000 mg/kg bw. All animals that received 2000 mg/kg body weight died after one hour. Hypoactivity, piloerection, prone position, reddening and edema on ears, fore-legs and hind-legs, dyspnea, incomplete eyelid opening and hypothermia were observed in the three dead animals of 2000 mg/kg and in one dead animall of 300 mg/kg group. These signs were considered to be distressful and painful symptoms caused by acute systemic toxicity of the test article. At 300 mg/kg body weight, all animals showed hypoactivity and piloerection on day 1. Some animals showed soft stool on day 2, but these symtoms were recovered. All survived rats gained normal body weight throughout the study. No abnormalities were observed in all survived animals. At 2000 mg/kg body weight, nasal discharge (reddish or clear) was observed in all animals externally. Hemorrhage on lymphatic nodes, stomach and intestine in all animals and hemorrhage on thymus in one animal were observed. One animal showed hypertrophy of pancreas and other one animal showed the hypertrophy of spleen. At 300 mg/kg body weight, hemorrhage on lymphatic nodes, and intestine were observed in the dead animal. And there was no abnormality by the macroscopic examination of survived animals after the study termination on day 15. The acute oral LD50 to rats of the read-across test article, Iron dichloride was estimated to be between 300 and 2000 mg/kg bw under the test conditions.

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed

Dose descriptor:

LD50

Value:

2 000 mg/kg bw

Quality of whole database:

High quality study

Acute toxicity: via inhalation route

Endpoint conclusion

Endpoint conclusion:

no study available

Acute toxicity: via dermal route

Link to relevant study records

Reference

Endpoint:

acute toxicity: dermal

Type of information:

read-across from supporting substance (structural analogue or surrogate)

Adequacy of study:

supporting study

Justification for type of information:

See attached read-across justification

Reason / purpose for cross-reference:

read-across source

Limit test:

yes

No. of animals per sex per dose:

5

Sex:

male/female

Dose descriptor:

LD50

Effect level:

> 2 000 mg/kg bw

Based on:

test mat.

Mortality:

During the study, there was no unscheduled death.

Clinical signs:

other: Yellowish-brown change on the skin of applied site was observed in all treated animals from day 2 but this sign was recovered on day 15 except 3 animals. 2 males and 4 females showed the reddish nasal discharge on day 2. See Table 1

Gross pathology:

Internally, no abnormalities were observed in all animals by microscopic examination. On application sites, scars were observed in one male and
one female (see Table 3).

Table 1. Mortality and clinical signs (1 dose group: 2000mg/kg nw)

Sex

Animal No.

Clinical signs observed in days after treatment

Mortality (%)

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

male

M1

N

Ya

Ya

Ya

†

N

N

N

N

N

N

N

N

N

N

0/5 (0)

M2

N

Ya

Ya

Ya

Ya

†

†

†

†

†

†

†

N

N

N

M3

N

Ya, Nd

Ya

Ya

Ya

Ya

Ya

Ya

Ya

Ya

†

†

N

N

N

M4

N

Ya, Nd

Ya

Ya

Ya

†

†

†

†

†

†

†

N

N

N

M5

N

Ya

Ya

Ya

Ya

Ya

Ya

Ya

Ya

†

†

†

N

N

N

female

F6

N

Ya, Nd

Ya

Ya

Ya

Ya

Ya

Ya

Ya

Ya

Ya

†

†

†

†

0/5 (0)

F7

N

Ya, Nd

Ya

Ya

Ya

Ya

Ya

Ya

Ya

Ya

Ya

†

†

†

†

F8

N

Ya

Ya

Ya

Ya

Ya

Ya

Ya

Ya

Ya

Ya

†

†

†

†

F9

N

Ya, Nd

Ya

Ya

Ya

Ya

Ya

†

†

†

†

†

N

N

N

F10

N

Ya, Nd

Ya

Ya

Ya

Ya

Ya

Ya

Ya

Ya

Ya

†

†

N

N

N: Normal

Nd: Red nasal discharge

Ya: Yellowish-brown change on application sites

†: Slight yellowish-brown change on application sites.

 

Table 2. Summary of group mean body weights

Sex	Animal number	Body weight (g)
		Day 1	Day 8	Day 15
Male	M1	275.1 279.7 266.2 265.8 256.9 268.7 ± 8.89	312.8 319.7 286.6 310.7 293.9 304.7 ± 13.88	360.1 379.1 329.7 369.2 331.7 354.0 ± 22.28
	M2
	M3
	M4
	M5
	Mean ± SD
Female	F6	225.1 232.3 226.9 233.5 223.8 228.3 ± 4.34	243.2 241.6 242.9 245.5 231.2 240.9 ± 5.59	253.3 250.0 260.6 269.1 252.2 257.0 ± 7.83
	F7
	F8
	F9
	F10
	Mean ± SD

 

 

Table 3. Gross necropsy findings (Group summary)

Dose (mg/kg/day)		2000
Sex		Male	Female
Number of animals examined		5	5
External finding	No gross finding Scar on applied site	4 1	4 1
Internal finding	No gross finding	5	5

 

Interpretation of results:

GHS criteria not met

Conclusions:

The acute lethal dose (LD50 values) of iron dichloride to rats by single dermal administration was considered to be greater than 2000 mg/kg body weight under the conditions of this study.

Executive summary:

In a classic dermal acute toxicity study, 5 male and 5 female Sprague-Dawley rats were clipped their fur on dorsal part approximately 10 % of the total body surface area one day before dosing. The read-across test article Iron dichloride was weighed and wetted with corn oil. The limit tests at one dose level of 2000 mg/kg body weight were performed. The test article was applied uniformly and held in contact with the skin with a porous gauze dressing and non-irritating tape for 24-hour exposure period. At the end of the exposure period, residual test article was removed using distilled water. During the study, there was no unscheduled death. Yellowish-brown change on the skin of applied site was observed in all treated animals from day 2 but this sign was recovered on day 15 except 3 animals. 2 males and 4 females showed the reddish nasal discharge on day 2. All rats gained normal body weight throughout the study. Internally, no abnormalities were observed in all animals by microscopic examination. On application sites, scars were observed in one male and one female. The acute lethal dose (LD50 values) of iron dichloride to rats by single dermal administration was considered to be greater than 2000 mg/kg body weight under the conditions of this study.

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed

Dose descriptor:

LD50

Value:

2 000 mg/kg bw

Quality of whole database:

High quality study

Additional information

A key acute oral toxicity test (Up-and-Down Procedure) was conducted with female Wistar rats to determine the potential toxicity of iron sulfide (Tribotecc® - Ferrostar) after a single dose via the oral route (Mohan Kumar, 2012a). The test item was suspended in Milli-Q water and was administered as a single oral dose to fasted (16 - 18 hours) rats. A limit test at 2000 mg/kg was initiated with one female rat. The first animal survived, and four additional animals were tested sequentially with the same dose. Those four animals survived, and the test was concluded. All animals were active, showed no clinical observations and gained body weight during 14 days observation period. All animals were subjected to necropsy at sacrifice and there were no abnormalities observed in any of the rats. Based on the present study results, the estimated acute oral LD₅₀ of iron sulfide is greater than 2000 mg/kg body weight in female rats. In a support read across oral acute toxicity study (acute toxic class method) iron dichloride was given in female Sprague-Dawly rats at 300 and 2000 mg/kg bw in corn oil (OECD SIDS, 2004). No mortality was observed at 300 mg/kg bw, so 3 additional rats were administered 300 mg/kg bw iron dichloride, with one animal found dead on day 2. Three additional rats were tested at the limiting dose of 2000 mg/kg bw, which all died after one hour. Hypoactivity, piloerection, prone position, reddening and edema on ears, fore-legs and hind-legs, dyspnea, incomplete eyelid opening and hypothermia were observed in the three dead animals of 2000 mg/kg and in one dead animal of 300 mg/kg group. These signs were considered to be distressful and painful symptoms caused by acute systemic toxicity of the test article. At 300 mg/kg body weight, all animals showed hypoactivity and piloerection on day 1. Some animals showed soft stool on day 2, but these symptoms were recovered. All survived rats gained normal body weight throughout the study. No abnormalities were observed in all survived animals. At 2000 mg/kg body weight, nasal discharge (reddish or clear) was observed in all animals externally. Hemorrhage on lymphatic nodes, stomach and intestine in all animals and hemorrhage on thymus in one animal were observed. One animal showed hypertrophy of pancreas and other one animal showed the hypertrophy of spleen. At 300 mg/kg body weight, hemorrhage on lymphatic nodes, and intestine were observed in the dead animal. And there was no abnormality by the macroscopic examination of survived animals after the study termination on day 15. The acute oral LD₅₀ to rats of iron dichloride was estimated to be between 300 and 2000 mg/kg bw under the test conditions.

 

An acute dermal toxicity test was conducted with Wistar rats (male and female) to determine the potential toxicity for iron sulfide (Tribotecc® - Ferrostar) after 24h exposure via the dermal route. The test item at the dose of 2000 mg/kg body weight prepared as a paste was applied occlusively on the dorsolateral thoracic skin to cover about 10% of body surface of the animal. After the 24 hours the dressing was removed and the applied area was washed and wiped dry. The treatment was initiated in 5 female rats at the dose of 2000 mg/kg body weight. There were no clinical signs of toxicity, local skin reactions or mortality observed, hence 5 male rats were treated at the same dose of 2000 mg/kg body weight. There were no clinical signs of toxicity, local skin reactions or mortality. There were no abnormalities detected at the necropsy. Based on the present study results, the acute dermal LD₅₀of Tribotecc®-Ferrostar is greater than 2000mg/kg body weight in male and female Wistar rats. In a support read across dermal acute toxicity study (classic method), 5 male and 5 female Sprague-Dawley rats were treated with iron dichloride in corn oil at 2000 mg/kg body weight under semi-occlusive dressing for 24-hour exposure period (OECD SIDS, 2004). At the end of the exposure period, residual test article was removed using distilled water.During the study, there was no unscheduled death. Yellowish-brown change on the skin of applied site was observed in all treated animals from day 2 but this sign was recovered on day 15 except 3 animals. 2 males and 4 females showed reddish nasal discharge on day 2, and all rats gained normal body weight throughout the study. Internally, no abnormalities were observed in all animals by microscopic examination. On application sites, scars were observed in one male and one female.The acute lethal dose (LD₅₀values) of iron dichloride to rats by single dermal administration was considered to be greater than 2000 mg/kg body weight under the conditions of this study.

 

The inhalation route was not considered appropriate based on low vapour pressure (for metals in general) and high particle size (d10 = 6.71 µm, d50 = 34.5 µm and d90 =65.4 µm), which are too large for reaching the alveoli of the lungs, therefore inhalation testing was not performed.

 

From the read across between the acute studies with iron dichloride (source chemical) and iron sulfide (target chemical), it is clear that iron dichloride is more toxic due to its corrosive properties, but also due to higher water solubility most probably leading to higher systemic absorption (as there were systemic toxicity effects especially after oral dosing). Therefore iron dichloride is a worst case source chemical, showing a factor of at least 6 in benefit of iron sulfide based on the difference in LD₅₀ (>300 mg/kg for iron dichloride and > 200 mg/kg bw for iron sulfide). This factor will be further used for risk evaluation based on read across for threshold related endpoints.

Justification for classification or non-classification

Iron sulfide does not have to be classified for acute toxicity according the EU labelling regulations of CLP No. 1272/2008 of 16 December 2008.