Concentrates of lead and zinc compounds with sulfur resulting from hydrometallurgy (hot acid leaching, super-hot acid leaching and flotation)

Endpoint summary

Description of key information

According to transformation/dissolution study (OECD guidance 29) conducted for the substance, the most critical constituents leachable to water from this UVCB substance are lead and zinc compounds. Therefore, the chemical safety assessment focuses on the properties of constituents and the key values for CSA are selected based on the read-across data on the most bioavailable compounds of Pb and Zn.
Acute toxicity studies conducted for a variety of read-across lead compounds up to limit values did not show any toxicity in animals after oral, inhalation or dermal exposure.
Oral LD50 values for soluble zinc sulphate (monohydrate, hexahydrate and heptahydrate) ranges from 574 to 2949 mg/kg bw, 862 to 4429 mg/kg bw and 920 to 4725 mg/kg bw, respectively for the three forms of zinc sulphate.
Acute inhalation toxicity was not observed in the available studies from lead and zinc compounds. Effects of inhalation exposure to zinc sulphate were limited to pulmonary effects only. However, inorganic lead compounds have harmonised classification entry for Acute Tox 4 (inhalation).
Dermal absorption is not significant and dermal route is not relevant route of human exposure. Also animal data demonstrated lack of acute dermal toxicity of lead and zinc compounds after dermal exposures up to the limit concentration of 2000 mg/kg bw.

Key value for chemical safety assessment

Acute toxicity: via oral route

Link to relevant study records

Reference

Endpoint:

acute toxicity: oral

Type of information:

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

Adequacy of study:

weight of evidence

Study period:

Not reported

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: see 'Remark'

Remarks:

Used in EU risk assessment for zinc sulphate, Study well documented, meets generally accepted scientific principles, acceptable for assessment.Read-across justification: Read-across from the most critical and bioavailable constituents (zinc and its compounds):The target substance is a solid inorganic UVCB substance and insoluble in water. Therefore, the transformation/dissolution study (OECD guidance 29) was conducted for the target substance to focus on the most critical bioavailable constituents of the substance. Based on the mineralogical composition, two major constituents of this target substance in addition to lead are zinc and sulphur. Zinc appears in sulphide form in the target substance. According to the 7-day and 28-day transformation/dissolution study at 100, 10 and 1 mg loadings (OECD guidance 29) zinc and sulphur are also soluble from the target substance. Since sulphur can appear either in sulphide or sulphate form in water, the read-across data focuses on the properties of zinc sulphate and other bioavailable forms of zinc. The read-across on zinc and its compounds are used in the chemical safety assessment for those endpoints where the adverse effects of the target substance can be affected by zinc content of the substance. The read-across data was justified in order to avoid unnecessary animal testing.

Reason / purpose for cross-reference:

reference to same study

Qualifier:

according to guideline

Guideline:

OECD Guideline 401 (Acute Oral Toxicity)

Deviations:

yes

Remarks:

(No data about doses, controls, observation frequency, fasting period before study, age at study initiation, housing of animals)

Principles of method if other than guideline:

Not applicable

GLP compliance:

no

Test type:

standard acute method

Limit test:

no

Species:

rat

Strain:

Sprague-Dawley

Sex:

male

Details on test animals or test system and environmental conditions:

for more information refer to reference

Route of administration:

oral: gavage

Vehicle:

other: suspended in 0.85% saline

Details on oral exposure:

animals were observed for 10 daysDOSAGE PREPARATION: Solutions were administered at pH between 6.0 and 7.0. Sodium bicarbonate was used to adjust the pH when necessary.CLASS METHOD (if applicable)- Rationale for the selection of the starting dose: A preliminary screening with small groups of 3 animals was carried out The LD50 values were then calculated according to the Litchfield and Wilcoxon method.

Doses:

50 , 100, 500, 1000 and 3000 mg/kg

No. of animals per sex per dose:

5 animals per dose

Control animals:

not specified

Details on study design:

see reference

Statistics:

No data

Sex:

male

Dose descriptor:

LD50

Effect level:

920 mg/kg bw

Mortality:

no information

Clinical signs:

other: see reference

Gross pathology:

reddened stomach and intestinal mucosa

Other findings:

No data

Interpretation of results:

harmful

Remarks:

Migrated informationCriteria used for interpretation of results: EU

Conclusions:

LD50 is 920 mg/kg bw

Executive summary:

In an acute oral study zinc sulphate (type not specified, only “Zinc sulphate, Rayon”) was suspended in 0.85% saline and administered to male Sprague Dawley rats by intubation. Dose levels were 50, 100, 500, 1000 and 3000 mg/kg (5 animals per dose). Animals were observed for ten days. Toxicity signs were reddened stomach and intestinal mucosa. The LD₅₀value was determined as 920 mg/kg bw zinc sulphate.

Endpoint conclusion

Endpoint conclusion:

adverse effect observed

Dose descriptor:

LD50

Value:

574 mg/kg bw

Acute toxicity: via inhalation route

Link to relevant study records

Reference

Endpoint:

acute toxicity: inhalation

Type of information:

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

Adequacy of study:

weight of evidence

Study period:

August 2003- February 2004

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: see 'Remark'

Remarks:

Well-documented and corresponded to the requirements of the recommended Annex V test guidelines.Read-across justification:Read-across from the most critical and bioavailable constituents (lead and its compounds):Based on the mineralogical composition, lead is the main constituent in the target substance and appears in sulphate form. The target substance is a solid inorganic UVCB substance and insoluble in water. Therefore, the transformation/dissolution study (OECD guidance 29) was conducted for the target substance to focus on the most critical bioavailable constituents of the substance. According to the T/D study results, the readily soluble constituent is lead. Based on the hazard profile of lead it is also the most hazardous constituent of this substance. Therefore, and in order to avoid the unnecessary animal testing, the read-across data from the most critical constituent is used to evaluate the short-term and long-term toxicological adverse effects of the target substance. The read-across data focuses on the properties of lead sulphate and other bioavailable forms of lead.

Qualifier:

according to guideline

Guideline:

OECD Guideline 403 (Acute Inhalation Toxicity)

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Test type:

standard acute method

Limit test:

yes

Species:

rat

Strain:

other: Charles River Deutschland GmbH - CD

Sex:

male/female

Details on test animals or test system and environmental conditions:

Age at start of adaptation: males: approx. 45 days females: approx. 56 days Body Weight at start of administration males: 217-233 g females: 195-211 g Number 10 (5 male and 5 female animals) Duration of experiment: at least 5 adaptation days, 1 test day and 2 recovery weeks Diet - ssniff R/M-H V11534 served as food (ssniff Spezialdiaten GmbH, D-59494 Soest;composition: see Appendix 2). Feeding was discontinued approx. 16 hours before exposure; only tap water was ten available ad libitum. Periodic analysis of the food for contaminants based on EPA/USA is conducted at least twice a year by LUFA-ITL (limitation for contaminants in the diet: see Appendix 2). Certificates of analysis of the composition and for contaminants were provided by the manufacturer and are QUA archived.Housing - Granulated textured wood was used as bedding material for the cages. The cages were changed and cleaned twice a week. Periodic analysis of the bedding material for contaminants based on EPA/USA is conducted at least once a year by LUFA-ITL (limitation for contaminants in the bedding material: see Appendix 2. During the 14-day observation period the animals were kept by sex in groups of 2-3 animals in MAKROLON cages (type III) at a room temperature of 22 degrees C +/-3 degreesC (maximum range) and a relative humidity of 55%+/- (maximum range). Deviations from the maximum range caused for example dfuring cleaning procedures are dealt with in SPOPs. The rooms were lit (150 lux at approx. 1.5 m room height) and darkened for periods of 12 hours each.Drinking water - Drinking water in bottles was offered ad libitum. Drinking waater is examined according to the "Deutsche Trinkwasserverordnung 2001' [German Regulations on drinking water 2001] by the Hamburger Wasserwerke, D20539 Hamburg, at least four times a year (limitation for contaminants in the drinking water: see Appendix 2). In addition, drinking water samples taken at LPT are analysed by LUFA-ITL once a year for means of bacteriological investigations according to the German "Deutsche Trinkwasserverordnung 2001, Anlage 1' [German Regulations on drinking water 2001, Addendum 1].

Route of administration:

inhalation

Type of inhalation exposure:

nose only

Vehicle:

other: unchanged (no vehicle)

Details on inhalation exposure:

The study was carried out using a dynamic inhalation chamber (air changes/h (>/= 12 times)) with a nose-only exposure of the animals according to KIMMERLE & TEPPER. The apparatus consists of a cylindrical exposure chamber (volume 40L) which holds a maximum of 20 animals in pyrex tubesat the edge of the chamber in a radial position. The dust of the test item was generated with a rotating brush dust generator. The generator was fed with compressed air (0.5 bar) from a compressor (air was taken from the surrounding atmosphere of the laboratory room and filtered using an in-line disposable gas-filter). At the bottom of the exposure chamber, the air was sucked off at a lower flow rate than it was created by the spray-jet in order to produce a homogeneous distribution and a positive pressure in the exposure chamber. A manometer and an air-flow meter was used to control the constant supply of compressed air and the exhaust, respectively. Flow rates were checked hourly and corrected if necessary. The oxygencontent in the inhalation chamber was 21%. It was determined at the beginning and at the end of the exposure with a DRAGER Oxygen-analysis test set (DRAGER Tube Oxygen 67 28 081). The whole exposure system was mounted in an inhalation facility to protect the laboratory staff from possiblehazards.Concentration (mg/L air): 5.05Air flow entrance (L/h): 900Air flow exit (L/h): 800Air changes (changes per hour): 22.5

Analytical verification of test atmosphere concentrations:

yes

Remarks:

Drager Tube Oxygen 67 28 081, Minisart SM 17598 0.45 UM(sample filter), Vacuubrand, MZ 2C6)

Duration of exposure:

ca. 4 h

Concentrations:

5.05 mg/L air - actual concentration; nominal concentration - 848.9 mg/L air; 5.834 um mass median aerodynamic diameter; 1.061 mg/L air respirable amount particle size

No. of animals per sex per dose:

1 group of 5 males and 5 females

Control animals:

no

Details on study design:

After completion of exposure, the animals were observed for a period of 14 days. During and following exposure, observations were made and recorded systematically; individual records were maintained for each animal. A careful clinical examination was made at least once daily until all symptoms subsided, thereafter each working day. Observations on mortality were made at least once daily to minimize loss of animals to the study, e.g. necropsy or refrigeration of those animals found dead and isolation or sacrifice of weak or moribund animals, Cageside observation included, but were not limited to: changes in the skin and fur, eyes, mucous membranes, respiratory, circulatory, autonomic and central nervous system, as well assomatomotor activity and behaviour pattern. Particular attention was directed to observation of tremor, convulsions, salivation, diahhoea, lethargy, sleep and coma. Individual weights were determined before the exposure and weekly after exposure. Changes in weight were calculated and recordedwhen survival exceeds one day. At the end of the test, the surviving animals were weighed and sacrificed. Necropsy of animals was carried out and allgross pathological changes were recorded.

Sex:

male/female

Dose descriptor:

LC50

Effect level:

> 5.05 mg/L air

Exp. duration:

4 h

Mortality:

No mortality occurred

Clinical signs:

other: No clinical signs of toxicity

Body weight:

No inhibition of body weight gain

Gross pathology:

No abnormalities were detected at necropsy.

Interpretation of results:

practically nontoxic

Remarks:

Migrated informationrequires no classificationCriteria used for interpretation of results: EU

Conclusions:

Under the present test conditions, the LC50-value for CD rats following inhalation of a dust of Litharge (Lead oxide) for 4 hours can be expected above an actual concentration of 5.05 mg/L air. According to the EC-Commission directive of September 1st, 1993 on the approximation of the laws, regulations and administrative provision relating to the classification packaging and labelling of dangerous substances (67/548/EC and its subsequent amendments) and the results obtained under the present test conditions, Litharge (Lead Oxide) requires no classification.

Executive summary:

The aim of the present experiment was to obtain information on the acute toxicity following single 4 -hour inhalation exposure of rats to Litharge (Lead Oxide) in an acute toxicity study designed as a test limit. Rats were exposed to a dust of Litharge (Lead oxide) at an actual concentration of 5.05 +/-0.010mg Litharge/L air for 4 hours by inhalation using a dynamic nose-only exposure chamber. In the inhalation chamber, close to the animals' noses, the particles had a mass median aerodynamic (MMAD) of 5.834UM as determined with a cascade impactor. The Geometric Standard Deviation (GSD) of the MMAD was calculated as 4.814. The geometric mean diameter of the supplied test item was 11.430 um as determined with a Malvern Mastersizer. Under the present test conditions, a 4-hour exposure to a dust of Litharge (lead oxide at a concentration of 5.05 +/-0.10 mg Litharge/L air revealed no clinical signs of toxicity. No mortality occurred. No abnormalities were detected at necropsy. All animals gained the expected weight throughout the study period. The LC50 can be expected above an actual concentration of 5.05 mg Litharge/L air for 4 hours at 14 days. According to the EC-Commission directive 67/548/ECC and its subsequent amendments on the approximation of the laws, regulations, and administrative provision relating to the classification, packaging and labelling of dangerous substances and the results obtained under the present test conditions. Litharge (Lead oxide) requires no classification.

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed

Dose descriptor:

LC50

Value:

5 050 mg/m³ air

Acute toxicity: via dermal route

Link to relevant study records

Reference

Endpoint:

acute toxicity: dermal

Type of information:

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

Adequacy of study:

weight of evidence

Study period:

August 2003-December 2003

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: see 'Remark'

Remarks:

Well-documented and corresponded to the requirements of the recommended Annex V test guidelines.Read-across justification:Read-across from the most critical and bioavailable constituents (lead and its compounds):Based on the mineralogical composition, lead is the main constituent in the target substance and appears in sulphate form. The target substance is a solid inorganic UVCB substance and insoluble in water. Therefore, the transformation/dissolution study (OECD guidance 29) was conducted for the target substance to focus on the most critical bioavailable constituents of the substance. According to the T/D study results, the readily soluble constituent is lead. Based on the hazard profile of lead it is also the most hazardous constituent of this substance. Therefore, and in order to avoid the unnecessary animal testing, the read-across data from the most critical constituent is used to evaluate the short-term and long-term toxicological adverse effects of the target substance. The read-across data focuses on the properties of lead sulphate and other bioavailable forms of lead.

Qualifier:

according to guideline

Guideline:

OECD Guideline 402 (Acute Dermal Toxicity)

Deviations:

yes

Remarks:

There was one deviation from the study protocol which was concerned with the relative humidity (section 6.2 husbandry). On some of the study days, the relative humidity was higher than 70%.

GLP compliance:

yes (incl. QA statement)

Test type:

standard acute method

Species:

rat

Strain:

Wistar

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS- Source: Harlan Winkelmann GmbH- Age at study initiation: - Weight at study initiation: male 285-323 g; female: 187-218 g- Fasting period before study: - Housing:Before the animals arrived, the study room and cages were cleaned and disinfected. During the study, the room and cages were cleaned at regular intervals. The rats were hpoused individually in cages (Makrolon II).- Diet (e.g. ad libitum): Teklad Global 18% Protein Rodent Diet (pelleted diet, batch no.204986) offered ad libitim.- Water (e.g. ad libitum): Tap water as for human consumption was continuously available ad libitum via drinking bottles. Samples of drinking water are subjected to bacteriological tests, including the determination of chlorinated hydrocarbons, heavy metals and arsenic.- Acclimation period: range finding: 15 days; main test: 21 daysENVIRONMENTAL CONDITIONS- Temperature (°C): Room temperature was adjusted to 22 +/-3- Humidity (%): The relative humidity was kept between 38 and 78%. Maximum and minimum temperature and humidity were monitored daily.- Air changes (per hr): Air was changed about 16 times per hour and filtered adequately.- Photoperiod (hrs dark / hrs light): Artificial light was set to give a cycle of 12 hours light and 12 hours dark with light on at 7:00 AM.IN-LIFE DATES: From: To:

Type of coverage:

occlusive

Vehicle:

unchanged (no vehicle)

Details on dermal exposure:

TEST SITE- Area of exposure: One day before each treatment, the fur was clipped from a dosal area of approx. 5X10 cm in each animal. The skin was subsequently examined for abrasions. Since the skin was healthy and intact, all animals were used for the test and coloured for individual identification.- % coverage: - Type of wrap if used: An occlusive dressing using a 4X5 cm patch (filter paper), Leukosilk and Elastoplast. To ensure good contact of the test article with the skin, a few drops of peanut oil were placed on the patch.REMOVAL OF TEST SUBSTANCE- Washing (if done): Patch Removal- Time after start of exposure: 24 hoursTEST MATERIAL- Amount(s) applied (volume or weight with unit): 2000 mg/kg body weight- Concentration (if solution): The test article was used undiluted as supplied by the Sponsor- Constant volume or concentration used: yes/no- For solids, paste formed: No. VEHICLE- Amount(s) applied (volume or weight with unit): The solid test article was used undiluted as supplied by the Sponsor.- Concentration (if solution):- Lot/batch no. (if required): 210213- Purity: 99.8% PbO

Duration of exposure:

The exposure period was 24 hours

Doses:

The rats were given a single dermal administration of the test artcle of 2000 mg/kg body weight.

No. of animals per sex per dose:

5 male and 5 female

Control animals:

not required

Details on study design:

In each animal a number of clinical-toxicological signs were evaluated according to a modified IRWIN Screening procedure (S. Irwin; Comprehensive Observational Assessment, Psychopharmacologia 134, 222-257, 1968) and observed findings were recorded. The animals were examined until 10min. p.a. and at the following post-treatment intervals: 1h, 2h, 6h, 24h and thereafter once daily up to day 14. Because of the occlusive dressing, the evaluation of some parameters were excluded until the 24-h observation time point. After patch removal, dermal irritation was evaluated once daily for14 days according to a scheme based on Draize. Body weights were recorded immediately before treatment and on days 7 and 14 p.a. (termination).

Preliminary study:

The range finding test was conducted using 2 female animals which were treated with the dose of 2000 mg.kg body weight. There were no deaths in the preliminary study.

Sex:

male/female

Dose descriptor:

LD50

Effect level:

> 2 000 mg/kg bw

Mortality:

No animal died during the course of the main test after the single dermal administration of 2000 mg/kg.

Clinical signs:

other: No abnormal clinical signs were observed. No skin irritation findings were seen.

Gross pathology:

Gross pathological examinations at day 14 p.a. (terminal necropsy) revealed no findings.

Other findings:

No specific findings.

On the basis of the results obtained after a single dermal administration of the test article "LITHARGE lead oxide" to Wistar rats, the LD50 values after 24 h and 14 days were as follows: Male and female > 2000 mg/kg

Interpretation of results:

practically nontoxic

Remarks:

Migrated informationLD50 > 2000 mg/kg may be classified "non-toxic."Criteria used for interpretation of results: other: Draize

Conclusions:

No specific findings. On the basis of the results, obtained after a single dermal administration of the test article "LITHARGE lead oxide" to Wistar rats, the LD50 values after 24 h and 14 days were as follows: Male and Female > 2000 mg/kg. This value is higher than the limit specified as harmful by the EEC Directive 2001/59/EEC of 6 August 2001 and the Gefahrstoffverordnung (GefStoffV) of 15 November 1999 (BGB1.I, p. 2233). When administered by the dermal route, the test article "Litharge lead oxide" may be classified as "non-toxic".

Executive summary:

The acute dermal toxicity of LITHARGE lead oxide was investigated in one group of rats comprising 5 males and 5 females. On the basis of the range finding test, the animals were given a single dermal administration of LITHARGE lead oxide at the dose of 2000 mg/kg. The skin was exposed to the test articles for 24 hours. Clinical observations were carried out at regular intervals during the 14 -day observation period. Signs of erythema and oedema were evaluated once daily for 14 days. Body weights were determoned immediately before treatment and on days 7 and 14 p.a. Gross pathological examinations were carried out at study termination on all animals. The following results were obtained:

- No animal died during the 14 -day observation period.

- No abnormal clinical signs were observed.

- No signs of or skin iiritation were observed.

- The body weight development was slightly influenced in most animals during the first week after treatment, possibly due to the administration procedure as such. At the end of the study, 14 days after treatment, the body weights were in the normal range

-Gross pathological examinations on day 14 p.a. did not reveal any findings in the rats.

Since no deaths were caused in Wistar rats after dermal treatment with the test article LITHARGE lead oxide of 2000mg/kg, the LD50 values after 24h and 14 days were as follows: Male and Female >2000 mg/kg

The above value is higher than the limit specified as harmful by the EEC Directive 2001/59/EEC of 6 August 2001 and the Gefahstoffverordnung (GedStoffV) of 15 November 1999 (BGB1.I, p. 2233). When administered by the dermal route, the test article LITHARGE lead oxide may therefore be classified as "non-toxic".

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed

Dose descriptor:

LD50

Value:

2 000 mg/kg bw

Additional information

The health hazard assessment was conducted based on the most critical constituents of the substance. This substance is an UVCB substance and can be described as a moist solid powder which is insoluble to water. Therefore, the transformation/dissolution study (OECD guidance 29) was conducted for the substance. Based on the finding of the T/D study results, the read-across data on the most critical constituents (ie. lead and zinc compounds) were used for the chemical safety assessment.

According to the chemical composition analysis, the main phases of the substance are lead sulphate and zinc sulphide. The product consists primarily of sulphur (ca. 35 %), lead (ca. 25 %) and zinc (ca. 17 %) together with minor trace elements such as silver, silicon, aluminium, calcium and iron.

The transformation and dissolution study (OECD guidance 29) results indicated that the release at pH 6 was higher for all studied elements compared to release at pH 8. Based on the screening test results (loading rate 100 mg/L), the most critical components for the assessment were lead and zinc, with releases of 8282 µg/L and 75.4 µg/L, respectively. The other minor leachable metals were silver (34.7 µg/L), cadmium (0.48 µg/L) and copper (17.2 µg/L).

Results from the 7 day T/D test (loading rate 100 mg/L, pH 6) showed similar trend in release rates: 12333 µg/L (Pb), 91.4 µg/L (Zn), 15.6 µg/L (Cu), 31.4 µg/L (Ag) and 0.056 µg/L (Cd). In the 28 day test with lower loading rate (1 mg/L, pH 6), only concentrations of Pb (362.4 µg/L) and Zn (3.2 µg/L) were over the detection limits or blank sample values.

As the most soluble and critical components of this substance are lead and zinc, read-across data from these critical constituents are used for thi sendpoint. The read-across justification is presented in CSR annex I. All read-across data for toxicology are based on test data using either soluble Pb or Zn salts or measured (dissolved) Pb or Zn concentrations. The weight of evidence approach was used to make conclusions on the key value for CSA.

Based on the mineralogical composition, in addition to lead, two major constituents of this target substance are zinc and sulphur. Zinc appears in sulphide form in the target substance. According to the 7-day and 28-day transformation/dissolution study at 100, 10 and 1 mg loadings (OECD guidance 29) zinc and sulphur are also soluble from the target substance. Since sulphur can appear either in sulphide or sulphate form in water, the read-across data focuses on the properties of zinc sulphate and other bioavailable forms of zinc.

Pb and zinc compounds

Acute oral toxicity

All available studies indicate a very low acute oral toxicity of seven inorganic lead compounds. There was also no evidence of any local or systemic toxicity associated with the oral administration of any of these compounds. Whether or not the compound contained the anion of an inorganic acid or an organic acid had no effect upon toxicity, and literature searches found no indications that anions present in high production volume compounds not tested would impart properties of toxicity different from those that have been tested. The substance contains ca. 40 % (w/w) lead sulphate. According to CLP Regulation 1272/2008, Table 3.1 List of harmonised classification and labelling of hazardous substances, “lead compounds with exception of those specified elsewhere in this Annex“ (Index No. 082-001-00-6) are classified toxic after oral exposure with harmonized C&L entry of Acute Tox. 4 H302. Based on the CLP mixture rules the substance will be classified for Acute Tox. 4 H302.

According to the mineralogical composition analysis, in addition to lead, two major constituents of this target substance are zinc and sulphur. Zinc appears in sulphide form in the target substance. According to the 7-day and 28-day transformation/dissolution study at 100, 10 and 1 mg loadings (OECD guidance 29) zinc and sulphur are also soluble from the target substance. Since sulphur can appear either in sulphide or sulphate form in water, the read-across data focuses on the properties of zinc sulphate and other bioavailable forms of zinc. Zinc sulphate has harmonised C&L entry of Acute Tox. 4 H302.

Acute oral toxicity studies are available in rats and mice on zinc sulphate. All available studies indicate a low acute toxicity via oral route. However, the acute oral toxicity studies with zinc sulphate do not specifically state which hydrated form of the zinc sulphate was tested. As this impacts the LD₅₀ value, all available LD₅₀ values were re-calculated to provide an understanding the range of LD₅₀ values of currently marketed zinc sulphate products (i. e., mono-, hexa-, and heptahydrate). Table below summarises the results of this re-calculation.

Re-calculation of oral LD₅₀rat values

Reported for Zinc sulphateform	LD50 (mg/kg bw)	LD50(mg/kg bw) recalculated for			Reference
		Mono	Hexa	Hepta
Dihydrate	1,710	1,554	2,334	2,490	Domingoet al., (1988)
Heptahydrate	2,280	1,423	2,137	2,280	Lorke, (1983)
Unspecified	2,949	1,840^1 2,949^2	2,764^1 4,429^2	2,949^1 4,725^2	Courtoiset al., (1978)
Unspecified	920	574^1 920^2	862^1 1,382^2	920^1 1,474^2	Litton Bionetics, (1974)
Hexahydrate	> 2,500	> 1,665	> 2,500	> 2,667	Sanders, (2001a)
Heptahydrate	1,000 < LD50< 2,000	624 < LD50< 1,248	937 < LD50< 1,875	1000 < LD50< 2,000	Sanders, (2001b)

¹Assumes testing of the heptahydrate (worst case) ;²Assumes testing of the monohydrate

Conclusion: Based on the composition and the bioavailability studies of the target substance, lead sulphate and zinc sulphate are considered as the most critical compounds for this endpoint. Lead compounds and zinc sulphate have harmonised C&L entry of Acute Tox. 4 H302. Since there is no measured data on the substance itself, the self-classification was done according to the CLP mixture rules. Based on the C&L results, the target substance is classified as having acute oral toxicity Acute Tox 4 H302 (C&L procedure is presented in IUCLID section 13).

Key value for CSA: LD₅₀ (oral; rat) 574 mg/kg bw based on the read-across data from the most hazardous component (zinc sulphate) with respect to acute oral toxicity in the substance.

Acute inhalation toxicity

The substance is moist solid material with moisture content of 15%. During the storage and transportation phases the material may dry. This may lead to the possibility that the material could produce particles of inhalable size when handled. The mean particle size of the dry substance was determined to be 29.31 to 31.67 µm; 50 % of the particles are less than 14.52 to 14.72 µm and 90 % of the particles less than 77.83 to 85.11 µm. The substance contains ca. 40 % (w/w) lead sulphate. According to CLP Regulation 1272/2008, Table 3.1 List of harmonised classification and labelling of hazardous substances, “lead compounds with exception of those specified elsewhere in this Annex“ (Index No. 082-001-00-6) are classified toxic after inhalation exposure with harmonized C&L entry of Acute Tox. 4 H332. Based on the CLP mixture rules the substance will be classified for Acute Tox. 4 H332.

Only one acute inhalation study in rodents is available on lead compounds showing virtually no toxicity. In this study male and female rats were exposed to dust of lead oxide at the concentration of 5.05 mg/L for 4 hours. No mortality or no clinical signs of toxicity were observed during the study. Thus, the LC50-value following inhalation of lead oxide is concluded to be above an actual concentration of 5.05 mg/L air.

Male Syrian hamsters were exposed via inhalation to zinc sulphate aerosols in doses of 1.3 to 34.2 mg /m³ (1.1-7.3 mg Zn) for 4 hours. The activity median aerodynamic diameter (AMAD) and geometric standard deviation (GSD) of the aerosols were 0.59 μm and 1.46, respectively. The rate of phagocytosis of insoluble particles by pulmonary macrophages was determined in situ by introduction of insoluble gold colloid in the respiratory tract under anaesthesia. From a dose of 5.2 up to 34.2 mg ZnSO₄/m³ macrophage endocytosis of colloidal gold was significantly reduced 1 h after exposure compared with that in unexposed control animals. After 24 hours the rate of phagocytosis was still depressed, whereas after 48 hours it had returned to normal values. An increase in macrophage cell number was seen at low concentrations followed by depressions in macrophage numbers at high concentrations. No effects were observed at 1.3 mg/m³ (0.2 mg Zn) (Skornik and Brain, 1983).

In anesthetized dogs the pulmonary mechanics were not significantly changed after inhalation exposure to submicron aerosols of ZnSO₄ up to 17.3 mg/m³ for 7.5 minutes. Also an exposure of 4 hours to 4.1 to 8.8 mg/m³ ZnSO₄ to anesthetized dogs showed no effect on breathing mechanics, hemodynamic, or on arterial blood gases (Sackner et al., 1981).

Conclusions: Acute inhalation toxicity was not observed in the available read-across studies from lead and zinc compounds. However, harmonised classification entry of Acute Tox. 4 H332 for lead sulphate in Annex VI of Regulation (EC) No 1272/2008 (CLP) is taken in the account in this hazard assessment. Since there is no measured data on the substance itself, the self-classification was done according to the CLP mixture rules. Based on the C&L results, the target substance is classified as having acute inhalation toxicity Acute Tox 4 H322 (C&L procedure is presented in IUCLID section 13).

Key value for CSA: LC₅₀ (inhalation; rat) 5050 mg/m³ based on the read-across data from the most hazardous component (lead) in the substance.

Acute dermal toxicity

Dermal absorption of lead and zinc compounds through intact skin is expected < 0.1% and < 2%, respectively. Thus absorption through skin is not significant and dermal route is not relevant route of human exposure.

However, data from two lead compounds (lead oxide and dibasic lead phosphite) were selected for dermal toxicity endpoint. Data demonstrated lack of acute toxicity in animals after dermal exposures up to the limit concentration of 2000 mg/kg bw.

Acute dermal toxicity has also been investigated with the soluble zinc sulphate up to the limit concentration of 2000 mg/kg bw. Rats were exposed to the test substance for 24 hours. Study result show that the dermal LD50 value is > 2000 mg/kg bw.

Conclusions: Based on the studies of the most critical constituents (lead and zinc) of the target substance and the low dermal adsorption potential of both substances no classification to acute dermal toxicity is warranted.

Key value for CSA: LD₅₀ (dermal; rat) 2000 mg/kg bw based on the lowest observed toxicity of the main and the most hazardous constituent (Pb) in the substance.

Justification for selection of acute toxicity – oral endpoint
No study was conducted for the target UVCB substance. The study was selected based on the read-across data from the most hazardous component in the substance (zinc) with respect to acute oral toxicity.The bioavailable and critical constituents in relation to acute oral toxicity are lead sulphate and zinc sulphate. The self-classification of this substance based on the mixture rules and the concentrations of these critical constituents triggered the classification to this hazard.

Justification for selection of acute toxicity – inhalation endpoint
No study was conducted for the target UVCB substance. The study was selected based on the read-across data from the most hazardous component in the substance (lead) with respect to acute inhalation toxicity.The bioavailable and critical constituent in relation to acute inhalation toxicity is lead sulphate. The self-classification of this substance based on the mixture rules and the concentration of this critical constituent triggered the classification to this hazard. Despite the fact that the substance is a wet powder, it can get dried during storage and handling, and therefore, the inhalation route is relevant route of exposure.

Justification for selection of acute toxicity – dermal endpoint
No study was conducted for the target UVCB substance. The study was selected based on the read-across data from the most hazardous component in the substance (lead) with respect to acute dermal toxicity.Based on theproperties of the critical constituents of the target substance dermal route is not relevant route of exposure.

Justification for classification or non-classification

Based upon the overall observations of the mineralogy and bioavailability studies on the critical constituents of the target substance, the read across from these critical constituents (lead and zinc compounds), their harmonised classifications in the CLP annex VI, and the self-classification results based on the CLP mixture rules triggers this substance to be classified for Acute Tox. 4 H302 and H332 according to CLP Regulation 1272/2008 and Xn; R20/R22 according to the Directive 67/548/EEC.