Sulfite liquors and Cooking liquors, white

Endpoint summary

Description of key information

- Due to the high alkalinity and corrosivity of White liquor the acute toxicity tests are not applicable for investigating the substance.
- There is no available information of acute oral, dermal or inhalation toxicity concerning White liquor. The maximum expected concentration of one identified main ingredient (disodium sulphide) holding a harmonized classification does not suggest an acute toxicity classification for White liquor according to CLP regulation 1272/2008 (ATE>2000), but indicates need for classification for acute dermal toxicity according to DSD/DPD rules (67/548/EEC).  
- In contact with acids, White liquor may release toxic and flammable hydrogen sulfide gas (H2S).

Additional information

Due to the high alkalinity and corrosivity of White liquor the acute toxicity tests are not applicable for investigation.

The expected maximum concentration ranges of the identified main components in White liquor that hold a harmonized classification, did not suggest acute oral toxicity of White liquor either.

There is no available data on acute dermal toxicity of White liquor. Of the identified main components of White liquor only sodium sulfide (EC 215-211-5) has a harmonized classification for acute dermal toxicity. Based on the maximum expected concentration of Na₂S (ca. 7% w/w) in White liquor, and CLP rules for classification, acute dermal toxicity class is not allocated.  In contrast, according to the classification rules given under the DSD/DPD system, the Na₂S concentration suggests classification as harmful in contact with skin.

There is no available data concerning acute inhalation toxicity of White liquor. However, given as supplemental hazard information it should be noted that in contact with acids White liquor may release hydrogen sulfide gas, which carries a harmonised classification for acute toxicity via inhalation.

Justification for classification or non-classification

White liquor is an aqueous alkaline solution of inorganic cooking chemicals in kraft or soda pulping process. The source materials for White liquor are sodium salts of green liquor and calcium oxide. White liquor is a UVCB substance with a variable composition. Therefore the toxicological properties may be somewhat variable.

Experimental studies on acute toxicity of White liquor were not applicable due to the high alkalinity and corrosivity of the substance. The classification for acute toxicity of white liquor is based on ingredients and read-across information to green liquor test results due to lack of available test data for the white liquor. Toxicity testing via oral and dermal routes is not applicable due to the highly alkaline and corrosive properties of white liquor. Read-across to green liquor for the already available short term rat study (OECD 423, LD50 750 mg/kg in rat GL dry solids) is also applicable to assess the acute toxicity of white liquor and to determine the specific concentration limits for classification based on sulfide content.

CLP classification

As there is no available test data on toxicity for White liquor, bridging principles are applicable due to test data on similar substances (Green liquor). The classification of White liquor is also based on ingredients (sulfide content).

Of the main components of White liquor only disodium sulfide (EC 215-211-5) has a harmonized CLP classification of Acute Tox. 4 via oral route.

Acute oral toxicity

The classification for acute toxicity of white liquor is based on ingredients and read-across information to green liquor test results due to lack of available test data for the white liquor. Toxicity testing via oral and dermal routes is not applicable due to the highly alkaline and corrosive properties of white liquor. Read-across to green liquor for the already available short term rat study (OECD 423, LD50 750 mg/kg in rat GL dry solids) is also applicable to assess the acute toxicity of white liquor and to determine the specific concentration limits for classification based on sulfide content.

Substance	Classification	Specific concentration limits for sulfide (S^2-) content in white liquor	Hazard Codes/Statement
Sulfite liquors and Cooking liquors, white	Acute Tox. 3 Acute Tox. 4	C ≥ 21 % 3 % ≤ C < 21 %	H301, Toxic if swallowed H302, Harmful if swallowed

Acute Dermal toxicity

Sodium sulfide has also a harmonized CLP classification of Acute Tox. 3 via dermal route. The maximum expected concentration of Na₂S in White liquor does not indicate acute dermal toxicity class either (ATE > 2000). Due to the inconclusive data on White liquor, no classification of acute toxicity can be assigned based on the CLP rules.

Additionally, in contact with acids White liquor may release hydrogen sulfide gas (EC 231-977-3), which carries the harmonised classification Acute Tox. 2 with the hazard statement H330: Fatal if inhaled. EUH032 (Contact with acid liberates very toxic gas) shall be applied.

Substance	Classification	Specific concentration limits for sulfide content in white liquor	Hazard Codes/Statement
Sulfite liquors and Cooking liquors, white	Acute Tox. 3     Acute Tox. 4	C ≥ 12 %   6 % ≤ C < 12 %	H311: Toxic in contact with skin H312: Harmful in contact with skin

Supplemental hazard information:

In contact with acids White liquor may release very toxic hydrogen sulfide gas. Therefore the hazard statements H330/R23 and EUH032/R32 are deemed necessary.