Calcium sulfate

Endpoint summary

Description of key information

Calcium sulfate is not considered to be harmful by the oral or inhalation route. The dermal toxicity of calcium sulfate is not considered to be relevant. Calcium sulfate is an inorganic ionic solid and is not expected to penetrate the skin. Furthermore, calcium sulfate is commonly used in plaster of Paris, and is not known to have been associated with any toxic effects

Key value for chemical safety assessment

Acute toxicity: via oral route

Link to relevant study records

Reference

Endpoint:

acute toxicity: oral

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: Study performed to GLP and guideline.

Qualifier:

according to guideline

Guideline:

OECD Guideline 420 (Acute Oral Toxicity - Fixed Dose Method)

GLP compliance:

yes

Test type:

fixed dose procedure

Limit test:

no

Species:

rat

Strain:

Sprague-Dawley

Sex:

female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Age at study initiation: 9 ~ 11 weeks
- Weight at study initiation: 194.9 ~ 206.6 g (sighting study), 194.9 ~ 203.6 g (main study)
- Fasting period before study: Animals were fasted the night before administration but fodder was offered 3 to 4 hours after the administration

Route of administration:

oral: gavage

Vehicle:

water

Details on oral exposure:

DOSAGE PREPARATION: Test substance was dissolved in the distilled water on the day of administration

- Rationale for the selection of the starting dose: In order to determine the appropriate starting dose for the main test, 50, 300 and 2,000 mg/kg of test substance were administered to each animal in a sighting study, but there were no toxic effects at least 2 days after the administration.

Doses:

50, 300 and 2000 mg/kg b.w

No. of animals per sex per dose:

In the screening study one female rat was used in each of the three doses. In the main test a further 4 female rats were administered with 2000 mg/kg of the test material.

Control animals:

no

Details on study design:

- Duration of observation period following administration: 14 days
- Frequency of observations and weighing: Mortality, clinical signs and toxic effects were observed 0.5, 1, 2, 3 and 4 hours after the treatment on the day of administration, after that were observed at least once a day till necropsy. Body weight was measured on day 1, 7 and 14.
- Necropsy of survivors performed: yes

Sex:

female

Dose descriptor:

LD50

Effect level:

> 1 581 mg/kg bw

Remarks on result:

other: The LD50 for calcium sulfate dihydrate was > 2000 mg/kg bw. The value has been calculated for calcium sulfate anhydrous

Mortality:

No mortality was observed within every dose level

Clinical signs:

other: There were no specific clinical signs during test period

Gross pathology:

No abnormal necropsy opinions in relation to administration of calcium sulfate, dihydrate.

Table 1: Mortality of Females (Group Summary)

 

Dose (mg/kg)	No. Dead/No. Dosed	Number of Deaths
		Days After Dosing
		1	2	3	4	5	6	7	8	9	10	11	12	13	14
50	0/1	0	0	0	0	0	0	0	0	0	0	0	0	0	0
300	0/1	0	0	0	0	0	0	0	0	0	0	0	0	0	0
2000	0/5	0	0	0	0	0	0	0	0	0	0	0	0	0	0

 

Table 2: Incidence of Clinical Signs in Females (Group Summary)

 

Signs observed	Dose level mg/kg	50	300	2000
Appears normals		1/1*	1/1	5/5
*: No. of animals with the sign/No. of animals examined

 

Table 3: Body Weights of Females (group summary)

 

Dose (mg/kg)	Animal Number
		Day 0	Day 1	Day 7	Day 14	Gain
50	1	194.9	214.0	234.2	243.0	48.1
300	2	200.2	225.6	229.6	235.2	35.0
2000	3	206.6	224.6	235.2	247.6	41.0
	4	194.9	214.6	222.4	227.8	32.9
	5	201.8	220.8	232.0	236.2	34.4
	6	203.6	217.6	220.0	224.8	21.2
	7	198.4	217.8	219.4	234.2	35.8
	Mean	201.1	219.1	225.8	234.1	33.1
	SD	4.55	3.79	7.30	8.84	7.30
	N	5	5	5	5	5

 

Table 4: Gross Findings of Females (Group Summary)

 

Dose (mg/kg)	Gross Observation		Frequency
	Location	Observation	Mortalities	Survivors
0	No gross findings		0/0*	1/1
300	No gross findings		0/0	1/1
2000	No gross findings		0/0	5/5
* No. of animals with the sign/No. of animals examined

Interpretation of results:

GHS criteria not met

Remarks:

The hydrated form exhibited no signs of toxicity whatsoever at the highest, dose therefore even with a correction to the anhydrous form which is lower that the limit dose, the anhydrous form is also considered not classified.

Conclusions:

The study was performed with calcium sulfate dihydrate which gave an LD 50 >2000 mg/kg. Based on this result the oral LD50 of calcium sulfate anydrous is >1581 mg/kg b.w

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed

Dose descriptor:

LD50

Value:

1 581 mg/kg bw

Acute toxicity: via inhalation route

Link to relevant study records

Reference

Endpoint:

acute toxicity: inhalation

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: Study performed to GLP and guideline

Qualifier:

according to guideline

Guideline:

OECD Guideline 403 (Acute Inhalation Toxicity)

GLP compliance:

yes (incl. QA statement)

Test type:

fixed concentration procedure

Limit test:

yes

Species:

rat

Strain:

Sprague-Dawley

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Harlan UK, Ltd, Oxon, UK
- Age at study initiation: 8-12 weeks
- Weight at study initiation: 199 - 350g
- Fasting period before study:
- Housing: Housed in groups of five by sex in solid-floor polypropylene cages with stainless steel lids, furnished with softwood flakes
- Diet: Harlan 2014 rodent diet ad libitum
- Water: ad libitum



ENVIRONMENTAL CONDITIONS
- Temperature: 19-25 °C
- Humidity: 30 -70 %:
- Air changes: 15 changes per hr
- Photoperiod: 12 hrs dark / 12 hrs light

Route of administration:

inhalation: dust

Type of inhalation exposure:

nose only

Vehicle:

other: unchanged (no vehicle)

Details on inhalation exposure:

GENERATION OF TEST ATMOSPHERE / CHAMBER DESCRIPTION
- Exposure chamber volume: Volume of ~ 30L (dimensions: 28 cm diameter x 50 cm high)
- Method of holding animals in test chamber: Each rat was held in a tapered, polycarbonate restraining tube fitted with a single tier of the exposure chamber and sealed by means of a rubber 'O' ring
- Source and rate of air: Compressed air was supplied by means of an oil free compressor
- Method of conditioning air: Passed through a water trap and respiratory quality filters
- System of generating particulates/aerosols: SAG 410 Solid Aerosol Generator (TOPAS GmbH, Dresden Germany)
- Method of particle size determination: Determined three times during the exposure period using a Marple Personal Cascade Impactor )Westech IS Ltd, Beds, UK)


TEST ATMOSPHERE
- Brief description of analytical method used: Gravimetric method
- Samples taken from breathing zone: yes

Analytical verification of test atmosphere concentrations:

no

Duration of exposure:

4 h

Concentrations:

Mean achieved 3.26 mg/L (calcium sulfate dihydrate), equivalent to >2.61 mg/L calcium sulfate anhydrous

No. of animals per sex per dose:

5/sex/dose

Control animals:

no

Details on study design:

- Duration of observation period following administration: 14 days
- Frequency of observations and weighing: All animals were observed for clinical signs at hourly intervals during exposure, immediately on removal from the restraining tubes at the end of exposure, one hour after termination of exposure and subsequently once daily for fourteen days.
- Necropsy of survivors performed: yes

Sex:

male/female

Dose descriptor:

LC50

Effect level:

> 3.26 mg/L air (nominal)

Based on:

test mat.

Exp. duration:

4 h

Remarks on result:

other: Equivalent to > 2.61 mg/L calcium sulfate anhydrous

Mortality:

No deaths occurred

Clinical signs:

other: Common abnormalities noted during the study included increased respiratory rate, hunched posture, pilo-erection and wet fur. Animals recovered quickly to appear normal from Day 2 post-exposure

Body weight:

One male animal exhibited a reduced bodyweight gain during Week 1 but recovered to show normal development during Week 2. Normal bodyweight development was noted for all other animals during the course of the study.

Gross pathology:

With the exception of one instance of dark patches on the lungs, no macroscopic abnormalities were detected at necropsy

Table 1: Temperature and relative humidity in exposure temperature:

Time (minutes)	Chamber temperature (°C) during exposure	Chamber relative humidity (%) during exposure
0	21	58
30	21	57
60	21	56
90	21	52
120	21	56
150	21	55
180	21	57
210	21	56
240	21	57

Table 2: Air flow and oxygen concentration in exposure chamber

Time (minutes)	Air flow (L/min) during exposure	Chamber relative humidity (%) during exposure
-3	50	-
0	50	20.8
30	50	-
60	50	-
90	50	-
120	50	20.8
150	50	-
180	50	-
210	50	-
240	50	20.8

Table 3: Exposure chamber atmosphere concentrations

Duration of exposure (minutes)	Net weight of sample (mg)	Volume of air sampled (L)	Chamber flow rate (L/min)	Atmosphere concentration (mg/L)
5	5.45	2	50	2.73
16	6.02	2	50	3.01
30	7.33	2	50	3.67
46	5.04	2	50	2.52
60	5.77	2	50	2.89
75	6.56	2	50	3.28
88	6.26	2	50	3.13
105	7.37	2	50	3.69
120	6.00	2	50	3.00
135	5.13	2	50	2.57
150	6.00	2	50	3.00
166	7.18	2	50	3.59
180	7.21	2	50	3.61
195	7.65	2	50	3.83
210	7.73	2	50	3.87
225	7.74	2	50	3.87
237	6.16	2	50	3.08

Mean achieved atmosphere concentration (mg/L) = 3.26

Standard deviation = 0.46

Nominal concentration:

Test material use (g)	150
Air flow (L/min)	50
Total generation time (mins)	243
Nominal concentration (mg/L)	21.3

Table 4: Cascade impactor data

Impactor stage number	Cut point (µm)	Amount collected (mg) per sample			Mean amount collected (mg)
		1	2	3
3	9.0	0.02	0.14	0.08	0.08
4	6.3	0.24	0.61	0.29	0.38
5	4.0	0.48	0.92	0.55	0.65
6	1.7	0.28	0.51	0.32	0.37
7	0.81	0.20	0.28	0.27	0.25
8	0.30	0.03	0.09	0.11	0.08
Back up filter	<0.30	0.03	0.10	0.03	0.05
Total mean amount of test material collected					1.86

Table 5: Calculation

Cut point (µm)	Log10 Cut point	Mean cumulative amount less than cut point
		(mg)	%	Probit
9.0	0.954	1.78	95.7	6.72
6.3	0.799	1.40	75.3	5.68
4.0	0.602	0.75	40.3	4.76
1.7	0.230	0.38	20.4	4.17
0.81	-0.092	0.13	6.99	3.52
0.30	-0.523	0.05	2.69	3.07

Results:

Mean mass median aerodynamic diameter (MMAD) = 2.92 µM

Geometric standard deviation (GSD) = 2.49

Predicted amount less than 4 µm = 63.6%

It is recognised that the mean achieved atmosphere concentration is lower than would generally be acceptable for this type of study. During characterisation, changes were made to the generation system to increase the inhalable portion of the test material, however, these changes also reduced the achievable test atmosphere concentration. However, as these changes reduced the particle size significantly it made it such that even at reduced test atmosphere concentrations the animals would be exposed to higher concentrations of particles <4 μm than if they were to be exposed to the standard target concentration of 5mg/L. It was, therefore, preferable to expose the animals to a lower concentration of test material, as this resulted in the animals being exposed to the highest possible concentration of particles <4μm.

Interpretation of results:

GHS criteria not met

Remarks:

Criteria used for interpretation of results: EU

Conclusions:

The acute inhalation median lethal concentration (4 hr LC50) of Calcium sulfate dihydrate, in the HsdHanTM : WIST strain rat, was greater than 3.26 mg/L, the equivalent LC50 value for the anhydrous form of this material is considered to be >2.61mg/L. On the basis of this result, Calcium sulfate dihydrate does not meet the criteria for classification in the EU in accordance with both Council Directive 67/548/EEC as amended and Regulation (EC) No 1272/2008 and will not require labelling for inhalation toxicity.

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed

Dose descriptor:

LC50

Value:

2 610 mg/m³ air

Acute toxicity: via dermal route

Endpoint conclusion

Endpoint conclusion:

no study available

Additional information

Acute toxicity: Oral route

In a reliable OECD guideline study (NIER 2003) calcium sulfate dihydrate was administered by gavage at 2,000 mg/kg bw to 4 female rats. Rats were observed for clinical signs and mortality for 14 days. No dead animals were observed in the limit test after 14 days observation so the oral LD50 for rats was > 2000 mg/kg bw. Based on this result the oral LD50 of calcium sulfate anhydrous is >1581 mg/kg b.w.

Khodykina 1996 (supporting study): Calcium sulphate (either as dihydrate or as hemihydrate) was administered to mice and rats by oral gavage. The following LD50 values were determined:

LD50 (dihydrate, mouse, oral) = 4704 mg/kg bw

LD50 (hemihydrate, mouse, oral) = 5824 mg/kg bw

LD50 (dihydrate, rat, oral) = 9934 mg/kg bw

LD50 (hemihydrate, rat, oral) = 9934 mg/kg bw

In the key study (NIER 2003), neither mortality nor any signs of systemic toxicity were observed after single oral administration of calcium sulphate dihydrate up to a maximum concentration of 2000 mg/kg bw to rats. Khodykina et al. (1996) have administered calcium sulphate (either as dihydrate or hemihydrate) in much higher concentrations (up to 10000 mg/kg bw) to both rats and mice. For either substance, animal and route of administration, the determined LD50 values were >4000 mg/kg bw, in fact doubling the requested benchmark dose for toxicity classification.

It can therefore be stated that calcium sulphate in either form can be regarded as non-toxic.

Acute toxicity: Inhalation route

In the current study, no signs of systemic toxicity were observed in rats up to a concentration of 3.26 mg/L calcium sulphate dihydrate.

It is recognised that the mean achieved atmosphere concentration is lower than 5 mg/L which is the required concentration for classification and labelling. During characterisation, the generation system was adapted to maximise the amount of particles <4 μm, as recommended by OECD (Series on Testing and Assessment Number 39: Guidance Document on Acute Inhalation Toxicity Testing, p37): “When testing aerosols, the primary goal should be to achieve a respirable particle size (MMAD of 1-4 μm). This is possible with most test articles at a concentration of 2 mg/L. Aerosol testing at greater than 2 mg/L should only be attempted if a respirable particle size can be achieved” and EC Guidelines (Regulation EC No. 1272/2008 section 3.1.2.3.2.): “Inhaled particles between 1 and 4 microns mean mass aerodynamic diameter (MMAD) will deposit in all regions of the rat respiratory tract. […] In order to achieve applicability of animal experiments to human exposure, dusts and mists would ideally be tested in this range in rats.”

Using a higher concentration of total dust would have led to a lower amount or respirable (<4 µm) particles. It can therefore be estimated that also at higher particle concentrations no toxicity after inhalation exposure has to be expected

Acute toxicity: Dermal route.

Calcium sulfate is an inorganic ionic solid. It is expected to partition strongly to water rather than organic media. While it is not possible to measure or accurately predict an octanol/water partition coefficient for inorganic ionic substance, such a value would be expected to be very low. Electrolytes are also known not to penetrate the skin in any significant quantity. Given the physico-chemical properties of CaSO4, it is not expected that the substance would penetrate the skin in any significant quantity and so would therefore not cause any toxic effects following acute dermal exposure.

Furthermore, plaster of Paris, containing mainly the hemihydrous calcium sulfate, has been used in the immobilization of broken bones and is not known to have been associated with any toxic effects, despite intimate skin contact, for periods of the order of one month, over considerable areas of skin. As this use simulates the acute dermal toxicity, it can safely be inferred that an acute dermal exposure test would be unlikely to cause any toxic effects.

Justification for classification or non-classification

Acute oral:

The acute oral toxicity of calcium sulphate was determined in two different studies. NIER 2003 found that the LD50 of calcium sulphate dihydrate after single oral application to rats is >2000 mg/kg bw. Khodykina et al. (1996) have administered much higher concentrations and found LD50 values >4000 mg/kg bw in both, rats and mice.It can therefore be stated that calcium sulphate in either form can be regarded as non-toxic and no classification is needed

Acute inhalation:

Although the current experiment does not reach the dust concentrations for classification according to Regulation EC 1272/2008 (max. limit dose of 5 mg/L) conditions were altered to achieve a maximum concentration of respirable particles (<4 µm). It can therefore be concluded that, even at higher dust concentrations, no systemic toxicity would arise.Taking into account the OECD Guidance Document on Acute Inhalation Toxicity Testing as well as Regulation EC No. 1272/2008, no classification of calcium sulphate as toxic by inhalation is justified

Acute dermal:

Calcium sulfate is an inorganic ionic solid not likely to penetrate the skin in any significant quantity. Furthermore, orthopaedic gypsum casts can be deemed to simulate acute dermal toxicity study conditions, are used for longtime without noticed any toxic effects. Therefore, it can safely be inferred that acute dermal exposure would be unlikely to cause any systemic toxic effects and therefore no classification for dermal toxicity is justified