Reaction mass of sodium hydrogensulfide and sodium carbonate

Endpoint summary

Description of key information

Acute oral toxicity: The acute oral toxicity is estimated using the LD50 values of the constituents, their proportions in the Reaction mass and assuming additivity of the ef-fects.  The following oral LD50 values were used for the estimate: for 60% sodium sul-fide 254 mg/kg corresponding 153 mg/kg of 100% sodium sulfide in rats, for sodium hydroxide 325 mg/kg in rabbits (determined using 1-10% NaOH and expressed as 100% NaOH) and for sodium carbonate 2800 mg/kg in rats. The estimated oral LD50 value for the Reaction mass is 699 mg/kg.    
Acute inhalation toxicity: No reliable studies are available (except for sodium carbonate that is a low potency and minor constituent of the Reaction mixture; inhalation LD50 800, 1200 and 2300 mg/m3 for guinea pig, mouse and rat, respectively), new studies are not justified due to high pH, minimal risk of inhalation.
Acute dermal toxicity: No reliable studies are available (except for sodium carbonate that is a low potency and minor constituent of the Reaction mixture; dermal LD50 >2000 mg/kg for rat), new studies are not justified due to high pH.

Additional information

General

A literature search and evaluation programme on animal and human acute toxicity data of sodium sulfide has been conducted.All data sources were assessed by expert toxicologists for quality and reliability, as well as relevance for regulatory risk assessment under REACH. The results are attached to the technical dossier in atabular report (IUCLID section 13).

Acute oral toxicity:

No studies on the Reaction mass are available. Therefore the acute oral toxicity is estimated using the LD50 values of the constituents, their proportions in the Reaction mass and assuming additivity of the effects. Acute oral toxicity is assessed using a weight-of-evidence approach. Two reliable studies (RL=1) with Na2S were included. An LD50 of 254 mg/kg bw could be derived for 60% sodium sulfide (corresponding 153 mg/kg for 100% sodium sulfide) from the Ullmann (1986) study report. Second, an LD50 of 1122 mg/kg bw was calculated for 100% (anhydrous) sodium sulfide in the study by Mason (1998). Based on a comparison with sodium hydrogensulfide as an analogous substance, the lower LD50 value (153 mg/kg) is used. For sodium hydroxide an oral LD50 values of 325 mg/kg in rabbits (determined using 1-10% NaOH and expressed as 100% NaOH) and for sodium carbonate an oral LD50 value of 2800 mg/kg in rats are used. The calculated relative potency values of sodium hydroxide and sodium carbonate against sodium sulfide are 0.471 and 0.0546, respectively, and the estimated oral LD50 value for the Reaction mass is 699 mg/kg.

 

Acute inhalation toxicity:

No reliable data are available for acute inhalation toxicity ofany of the constituents of the Reaction mixture except sodium carbonate (LD50 800, 1200 and 2300 mg/m3 for guinea pig, mouse and rat, respectively), new studies are not justified due to high pH, minimal risk of inhalation. Although this is a potential route of exposure for workers, testing is not justified since the test substance is classified as corrosive to skin and has a pH value of 13. Therefore, in accordance with section 8.5.2, column 2 Annex VIII of Regulation (EC) 1907/2006, in-vivo testing for acute toxicity study via inhalation does not need to be conducted.

Acute dermal toxicity:

No reliable studies are available (except for sodium carbonate; dermal LD50 >2000 mg/kg for rat).In the study report on acute dermal toxicity of sodium sulfide (60 % flakes) by Seaman,1982 [cited in IUCLID (2000) as TSCATS Accession number 26523, NTIS/OTS 505455, EPA doc N° 88-8100368, (1982) ], rabbits were treated with the test material at a dose level of 340 mg/kg bw, after which 9/10 animals died. However, the test material was applied toabradedskin (involving a series of scratches by which the stratum corneum was penetrated/abraded with a gauge needle), instead of intact skin. The study was assessed for relevance and reliability for risk assessment according to the criteria proposed by Klimisch et al. (1997), with the following conclusion: the study was rated as not reliable (RL=3) for use in EU risk assessment. The primary reason for this was that according to guideline OECD 402 (1987), care must be taken to avoid abrading the skin, which would alter its permeability, implying that the LD50 should be determined for animals treated via intact skin. Since the skin was damaged on purpose in this study by prior abrasion, the mandatory prerogative of an intact skin surface is violated. Although dermal route is a potential route of exposure for workers, new testing is not justified for animal welfare grounds: in accordance with section 8.5.3, column 2, Annex VIII of Regulation (EC) No. 1907/2006, an in-vivo acute dermal toxicity study does not need to be conducted since the test substance is classified as corrosive to skin.

Justification for classification or non-classification

Acute oral toxicity:

The LD50 value for 100% sodium sulfide is 153 mg/kg. According to the OECD SIDS Reports the oral LD50 of sodium hydroxide in rabbits is 325 mg/kg (expressed as 100% NaOH) and that of sodium carbonate in rats is 2800 mg/kg. The maximum proportions of these constituents (representing the worst case) of the Reaction mass are 19% (w/w) of the sulfides (sodium sulfide 3% + sodium hydrogen sulfide 16%), 5% (w/w) of sodium hydroxide and 10% (w/w) of sodium carbonate. Based on these values and assuming additivity of effects (the most likely mixture effect) for the constituents the estimated LD50 value of the Reaction mass is 699mg/kg.

Thus, based on the estimated LD50 value, according toCommission Regulation (EC) No 790/2009 Annex I Table 3.1.1., the classification of the Reaction mass is Acute Tox. 4, H302 ‘Harmful if swallowed’.

Specific target organ toxicant (STOT) – single exposure: oral

The classification criteria according to regulation (EC) 1272/2008 as specific target organ toxicant (STOT) – single exposure, oral are not met. No additional classification required.

 

Acute inhalation toxicity:

No classification is proposed for acute inhalation toxicity in the absence of an appropriate study. According to the data requirements as outlined in section 8.5, Annexes VII-VIII of Regulation (EC) 1907/2006 no new testing should be conducted as the substance is classified as skin corrosive cat.1b (causes severe skin burns and eye damage) according to Regulation (EC) No 1272/2008.

 

Acute dermal toxicity:

Current classification:Annex 1 of 1. ATP of the CLP Regulation [Commission Regulation (EC) No 790/2009 of 10 August 2009 amending, for the purposes of its adaptation to technical and scientific progress, Regulation (EC) No 1272/2008 of the European Parliament and of the Council on classification, labelling and packaging of substances and mixtures], Index No. 016-009-00-8, includes a classification as “H311: Toxic in contact with skin” for sodium sulfide (Annex IV includes a classification as R24). This classification does not appear in the previous versions of the “CLP Regulation” [Regulation (EC) No 1272/2008].

Seaman,1982 [cited in IUCLID (2000) as TSCATS Accession number 26523, NTIS/OTS 505455, EPA doc N° 88-8100368, (1982) ], reported acute dermal toxicity of sodium sulfide (60 % flakes) on rabbits treated with the test material at a dose level of 340 mg/kg bw. In this study, 9/10 animals died. Furthermore, it was observed that the test material was highly corrosive to the skin. However, the test material was applied toabradedskin (involving a series of scratches by which the stratum corneum was penetrated/abraded with a gauge needle), instead of intact skin, due to which the study was rated as not reliable (RL=3) for use in EU risk assessment.

No other reliable and relevant data on acute dermal toxicity of sodium sulfide are available. The dermal LD50 value for sodium carbonate is as low as >2000 mg/kg. Although this is a potential route of exposure for workers, new testing is not justified for animal welfare grounds: in accordance with section 8.5.3, column 2, Annex VIII of Regulation (EC) No. 1907/2006, an in-vivo acute dermal toxicity study does not need to be conducted, since the test substance is classified as corrosive to skin (sodium sulfide andthe Reaction masshas a pH value ≥11.5 in aqueous solution).

Conclusions: In Directive(1999/45/EEC), mixture including constituent classified R24 between 3 and 25% is classified as R21. Using conversion table in Annex VII ofRegulation (EC) No 1272/2008, the classification of the Reaction mass is Acute Tox. 4, H312: ‘Harmful in contact with skin’.